NOTE:This is not a forced induction theory discussion, as those topics are fully covered by any number of different internet sites, and in a number of books. We are also assuming that the person using this guide is very well aware of all the particulars when it comes to SHO ownership, and we can assume that before anyone would undertake a mission such as this, that they are intimately aware of what needs to be done to a SHO for it to fully enjoy the benefits of forced induction (suspension, brakes, engine maintenance, etc). As such, those topics will not be covered here, except where they directly affect the fuel/engine/tuning/etc needs specific to a turbocharged venture.
TURBOCHARGING YOUR SHO
PART 1 - Two important questions
By far the question I am asked most often, and which I see most often in the various posts by those interested in turbocharging their SHO, is this: Will this turbo work for a SHO? The answer: YES. Every turbo will work for a SHO. How well it will work is an entirely different matter. To that end, I highly recommend that anyone interested in turbocharging their SHO asks themselves two very important questions, as the answer to these questions will outline their entire project. Question #1 - What is my budget? Question #2 - What is my intended usage?
1.1 - What is my budget?
Now, you may wonder, what does my budget have to do with my turbo selection? Well, not only do turbochargers themselves very greatly in price, from cheap chinese ebay knock-offs (less than $300) to super trick ball-bearing units from name brand manufacturers ($2000+), but the capability of the turbo has everything to do with the modifications needed to support that capability. In other words, it makes no sense to spend a large amount on a turbocharger if you do not also plan to spend a large amount on the supporting hardware needed to extract the peak performance of said turbocharger. So, sit down with paper and pencil, and give yourself a budget. Way too many projects are started without a clear budget in mind, and many of those projects are abandoned once the cost exceeds initial expectations. Hopefully, with a realistic and honest budget, and by purchasing parts that fit that budget, you will be much more likely to see your project to completion.
1.2 - What is my intended usage?
Is this going to be a weekend toy? A daily driver? An all out track weapon? A dragstrip warrior? The ultimate highway Supra-killer? Again, ask yourself honestly, what do I want this car to do? Because the best turbocharger for a monster standing mile car is not necessarily the ideal choice for a daily driven commuter. The SHO engine, with the proper supporting mods, is capable of making WAAY more power than the drivetrain can handle. Do not let an insane HP goal cause you to build a car that is no fun anywhere accept above 6000rpms. That said, there are a number of turbocharger selections that will allow the SHO engine to have a very broad and usable TQ curve, while providing a very nice high rpm HP rush.
PART 2: Turbo selection
So, we have already answered what our intended usage is, which in large part is decided by our budgetary constraints. Now we are ready to pick a turbo to match our needs. But how? As you have surely noticed, there are a MYRIAD of choices when it comes to turbochargers in comparison to superchargers. The reason being, a turbo is entirely dependant on the exhaust of the engine to drive it's turbine and compressor. A supercharger does not have to worry about this. It is going to move a certain amount of air at a certain RPM regardless of what vehicle it is on. So you end up having much less trim choices. Most of us are familar with the Vortech S-trim and T-trim correct? Consider this the compressor side of the turbo. Only with turbos, there are a LOT of compressor choices, in different trims within each compressor family. The pulley size of a supercharger has a large effect on it performance. Consider this the turbine side of the turbo. Only with turbos, there are a LOT of turbine choices (not just the turbine itself, but the A/R of the turbine housing). Sound confusing? Well, it can be. But we are already ahead of the game, because we have answered what our intended usage is, and what our budget will be. So, we can simplify things. All we really have to worry about is finding a turbo whose compressor map matches the needs of our build, and that brings us to the next section.
2.1 - Compressor maps
Now, this section is not going to go into detail about how to read compressor maps, or the importance of A/R ratios, or certain trims of compressor wheels. It is simply a broad overview, but if you can grasp the fundamentals, it will get you in the ballpark of where you need to be concerning turbo selection. First, let's take a look at a compressor map. This is from a Turbonetics 62-1.
As you will notice, this is a simply X Y axis graph to plot the airflow capabilities of this certain compressor. To the left we see PRESSURE RATIO, and along the bottom, AIRFLOW. The ovals in the middle are EFFICIENCY ISLANDS (the higher the percentage, the better use we are getting out of our compressor), and the arcs are a measure of the compressor's RPM. The dashed line along the left is the SURGE LIMIT. These items will tell us all we need to know about our compressor selection (we will get to turbin A/R later). The pressure ratio is just that, a RATIO of our intake manifold pressure (actually compressor outlet pressure, but for this discussion we are simplifying things) plus atmospheric pressure (actually compressor inlet pressure) divided by atmospheric pressure. Now, lets assume we are considering this turbo. Our intended usage is a modest daily driver, our budget is small, so we will be using stock injectors/MAF/tuning, and stock engine internals, and no intercooling. With that, our HP limit is around 300chp. Is this turbo a good choice? Let's have a look. The AIRFLOW axis, measured in LBS/minute, is an approximate indicator of how much HP you will be making. 30 lbs/min equates to approximately 300chp. Our stock non-IC engine will only like about 10psi. But there is no PSI markings on this graph you say. Correct, only PRESSURE RATIOS. So what pressure ratio does 10psi equate to? This is the equation - intake manifold pressure (IM) plus atmospheric pressure (AP) divided by atmospheric pressure (AP). So, IM (10psi) plus AP (14.7psi) divided by AP (14.7psi) = Pressure Ratio (PR)...(10spi+14.7psi)/14.7psi = PR...24.7psi/14.7psi = PR...1.68 = PR...PR = 1.68. We simply add our expected manifold pressure to 14.7 and then divide that sum by 14.7 to get our PR. To make it easy, at the end of this section is a breakdown of all psi levels as they equate to PR, from 5psi to 25psi. Now, back to our map. We have our PR of 1.68 (let's call it 1.7) and our airflow of 30lb/min (300chp). Let's plot those out on our map.
From looking at our plotted points, and our map, does this seem to be the best compressor choice for our needs? Technically, this turbo will meet our HP desires (with no problem of course), we are in a good efficiency island, but as we can see, there is a LOT of turbo left on the table. And with our mostly stock components, we will never see the full capacity of this turbo, and due to it's larger size, turbo lag will be a factor. I bet we can find a more suitable compressor, one that will nearly elimate lag, and still provide enough room for HP growth down the road. Take a look at this compressor map, with the PR and airflow plotted, to see what I mean.
This is a T04B turbine/H3 compressor section (old nomenclature, not sure what turbonetics would call it now). Our PR/airflow plot puts us almost right in the middle of the best efficiency island. And as we can see, if we wanted to up the boost some, perhaps after we made some injector/MAF/intercooler upgrades, we could easily make 350chp, and still be right in our best efficiency island. This would be the better choice considering our intended usage and budget.
As another example, let's us assume we have a large budget (one that allows for a Tweecer, forged pistons, upgraded fuel system including large injectors, intercooling, etc), and we want a beast of a SHO, something in the neighborhood of 450chp. Will this T04/H3 work well for us? It will probably take around 15psi (a PR of just over 2.0) to achieve that number. Let's add those numbers to our map.
Now we can see that we have went from nearly a 74% efficiency down to around 67%, and are at the edge of this turbo's capabilties. Will it work? Yes, it will make the power we want, but can we find a better suited compressor? Let's take another look at the 62-1 we saw earlier, with the new numbers as well.
Ahh, now we are talking! We can make our desired 450chp, and we are well within the capabilities of our turbo, in a high efficiency island, and still have plenty of room to grow should we desire to run more boost.
So, do we begin to understand the importance of proper compressor selection? As we stated at the outset, nearly ANY turbo will work on the SHO, but how WELL it works is what is important to us. And by having a good idea of our budget and intended usage/HP goal, we can narrow those hundreds of options down to just a few.
psi vs pressure ratio table:
5psi = 1.34 PR
10psi = 1.68 PR
15psi = 2.02 PR
20psi = 2.36 PR
25psi = 2.70 PR
2.2 - Turbine A/R ratio
Now, about the turbine A/R. Without going into great detail, the A/R is defined as the inlet cross-sectional area divided by the radius from the turbo centerline to the centroid of that area. In simple terms, a smaller A/R increases the velocity of exhaust gas powering the turbine, at the expense of more backpressure, which will reduce the capacity of that particular turbine and effect high rpm performance. A larger A/R decreases the velocity of the exhaust gas powering the turbine, decreases backpressure, increases boost lag, but lets the engine breathe better at higher rpms (something our SHO's love to do). For instance, two identical turbocharger compressors, one with a 0.63 A/R, one with a 1.21 A/R. The smaller A/R turbo will boost very quickly, which will effect the TQ curve dramatically, giving LOT of low end grunt, but sacrificing top end HP. The large A/R turbo will breathe VERY well at high rpms, and make lots of top end power, but will have more boost lag, which will effect the low end TQ. The same turbocharger, but they make their power very differently. I would go so far as to say that A/R selection is MORE important than compressor selection, to a point. For example, my last turbocharger was a T3/60-1, with a smallish A/R (around .63 I think). That car made LOADS of TQ at low RPM, and had very quick turbo spool. My current 62-1 has an A/R of .81. It builds boost a little slower, but it also breathes much better at high rpm. While the old turbo outshined this one for TQ production in rpm's below 5000, it only made useful HP to around 6000rpm. My current turbo still makes great TQ, but due to the larger A/R, it lets the engine breathe much better at high rpm, so that @ 7000 rpm it is making a LOT more HP than my old turbo (and more TQ). Lastly, note that compressor housings do not generally come in differing A/R ratios, as they have much less effect than the A/R of the turbine housing. Also, keep in mind that the compressor maps we looked at above are only a measure of the COMPRESSOR's capability, and do not take into account engine size and speed or turbine A/R, all of which will have a great effect on performance. But fret not, this does not make the compressor maps useless. Just remember that they are more of a guide than an actual blueprint of turbo performance.
PART 3 - Exhaust Piping
So, we have out turbo picked out now, but where do we put it? Certainly, there are a number of choices, each with it's own advantages and disadvantages. There is at least one of each of the following type of turbo powered SHO on the road right now: rear remote mount (strings), engine bay (in place of stock filter box, as seen on my car, Power Surge, NCtaurusSHO and others), and subframe mount (in the case of somedude's ATX SHO). Since my area of familiarity is with the engine bay mounted turbo, that is what the references in this article will deal with. One of the main reasons there have been so few turbocharged SHO's is because of the problems associated with fabricating the pipes responsible for carrying the hot air charge to a suitable location in the engine bay. As you are all aware, there simply is not a tremendous amount of free space under the hood of the SHO. And routing HOTHOTHOT pipes up near delicate wires/hoses/electrical components is no task for the uninformed. This is why turbo placement under the hood is usually limited to the airbox area. On my setup, a y-pipe collects the rear exhaust and routes it toward the front of the car, joining up with the front manifold to form an uppipe routed between the engine and fan shroud. Here is a picture from underneath the car.
It terminates right above the ABS block, to place the turbo in the stock airbox location. The ABS computer and ICRM are both relocated slightly to allow for plenty of room between them and the hot pipe. Also, I have cut down the neck of the thermostat housing and fitted a stainless steel radiator hose for better clearance. So far, in over 55k miles of driving, no failures of those parts has been experienced.
Now that we have a turbo placed in this general area, we have to provide it with fresh air, and make room for intercooler piping if we are running one (and an IC is always recommended). On my car, I removed material from the driver engine bay wall to allow for placement of a 3" inlet pipe. The open element conical filter, attached to the 80mm Lincoln MAF, resides in the fenderwell area fore of the front tire. This area provides clean cool air, with little worry of splashing water up into the filter element.
With so many options available for intercoolers, for now we will leave this area alone. Later I will include some pics of my current setup, as well as a new setup I have been working on.
With the turbo placed in the position described above, the exhaust must be routed towards the back of the engine bay. There really is only one route here, with the downpipe finding the room between the firewall and transmission (there is a small space just to the passenger side of the speedometer cable). It is tight here, with the downpipe actually against some cables/wire, so care must be taken in wrapping the downpipe, and also in insulating the surrounding wires/cables. Once past the intermediate shaft, the downpipe connects up to your choice of 'catback' exhaust (I have no catalytic convertors on my car, and am making no provisions for one in the upcoming downpipe). While we are on the topic of exhaust, I think it is safe to stay that a completely stock exhaust system will not provide much restriction for low boost/low HP systems (300hp). And the popular dynomax or other 2.5" systems out there will likely flow up to 400hp with no problems. Above that, you will likely need some type of custom exhaust. The one pictured below is in use on my current SHO, it is a 3" mandrel bent system with a single Thermal Dynamics muffler. A system such as this should be able to flow in excess of 700hp.
Part 4 - Fuel system/engine upgrades
4.1 - Fuel system upgrades
No matter what our goal, the main purpose of turbocharging our SHO is for an increase in HP and TQ. The turbocharger does it's part by cramming the engine with more air than it could take in if it were naturally aspirated. But air is only part of the equation. Without the adequate fuel to mix with that incoming air, no more power will be had. There is no need to go into detail about duty cycles and pulse widths and other minutia of fuel injectors. Suffice it to say that if we are turbocharging a SHO, we will want to upgrade our injectors and fuel pump. The stock system can support close to 300chp, but to do so it will be operating at near 100%, and it is always a good idea to keep a safety margin when it comes to fuel. Run your car too lean, and bad things can happen.
Just how much modification needs to be done? Again, it all depends on what our HP goals are. A small turbo/low boost system could get by with 39lb injectors and a 155lph pump, enough to support 350chp with no difficulty. For reference, my last turbo SHO used a 190lph pump and 47lb injectors, and supported 505+chp through the stock fuel lines (using an FMU). I eventually upgraded to the SHONUT hi-flow fuel system, which incorporates dual feed lines from the regulator to the rail, a larger feed line from the the tank, and an adjustable FPR. My next project has a 255lph high pressure fuel pump to insure that I will always have plenty of fuel. Even larger injectors can be had for the SHO, some people are using 63lb'ers right now, which will probably be my next choice. But most people will never need anything larger than the Accel 48-lb injectors, a quality 255lph pump, and an aftermarket FPR, as those items will reliably support upwards of 525chp in a well tuned turbocharged SHO.
Keep in mind that some injectors will require you to modify your fuel rails to accept them. Others are available that will fit a stock rail with no modification. Do your research and know what you are buying. Also, DO NOT USE AN FMU! Yes, the original turbo SHO ran one for years, and the FMU provided plenty of fuel. But lack of fuel is not a weak spot for FMU's. Lack of tuning abililty is. I can not stress how much better this car runs now that I am using a proper FPR. Idle quality is MUCH better. Driveablity is MUCH improved at all throttle positions. And fuel mileage is much better, with my last road trip allowing me a 26mpg fillup (with average speed well above the posted limit). FMU's can work, but they should be viewed as a temporary bandaid only.
4.1 -Engine upgrades
Sure, we all want a 3.2 low compression forged engine with a knife-edged crank and shotpeened rods, and we want to bolt on p+p heads stuffed with the meanest camshafts known to man, breathing through extrude honed runners and BBB's. So does that mean that if you don't have the deep pockets needed for such items that your dreams of owning a turbocharged SHO will never be realized? Of course not. If you own a SHO, any SHO, you already have one of the more robust and capable engines ever offered in a Ford sedan. The stock rotating assembly (save for the pistons) of any well maintained SHO will withstand the abuse of over 750hp. VERY few stock engines can make that claim. My last turbo SHO has as it's ONLY engine mods the following - overbore to 3.2L, forged low CR pistons. But the heads, cams, intake manifold, throttle body, exhaust manifolds, rods, crank, etc, etc, etc are all BONE STOCK. There simply is no need to spend huge amounts of cash of a laundry list of engine modifications when you are planning a turbo SHO project. Save your money and concentrate getting high quality turbochargers/WG's/BOV's and the needed fuel system and tuning upgrades. The only engine upgrade I will strongly encourage is that of forged pistons (a slight drop in compression ratio is desired as well, for reference, mine are 9:1, down from the stock 9.8:1). Forged pistons are better suited than the stock hypereutectic pistons to withstand the extra pressure and heat that turbocharging introduces. If you plan on running anything more than 15psi, plan also on getting forged pistons.
Certainly, once one has eeked out every last ounce of HP they can from their current turbo system, and they still want more, the above mentioned camshafts, head work, EH intakes, etc, etc can give nice HP gains. But IMO, it is more worthwhile to concentrate your effort and time and money to other areas of the car that are not up to the task of putting up with the demands of a 400+hp 3400lb sedan. Bigger brakes, suspension upgrades, a Quaife. With even a mild turbo system you will already be making enough TQ to snap your fair share of third gears. More power will only hasten the demise of your transaxles. Of course, I know full well that plenty of you will disregard what I say and do everything you can to that Yamaha gem so that you can brag about having the most powerful turbo SHO on the planet. So to that end, I feel it is my obligation to stay one step ahead of you. But that is a discussion for another time and place...
Pertinent pics will be added soon, stay tuned for updates.
Part 5 - Tuning your turbocharged SHO
5.1 - Why do I need a tune?
While many modifications to the SHO can be performed with great results and without making any changes to the stock EEC-IV programming information, the airflow capacity of a turbocharged SHO is simply too much for the stock strategy. To that end, there are some changes that we are going to have to make. Already mentioned were the fuel upgrades that are necessary for your venture. Once larger injectors than stock are used, you must have some way to tell the computer so that it can adjust for the different fuel flow. Also, the stock MAF meter will only be able to meter about 300chp, a number very quickly eclisped in even the lowest boost turbo SHO. Again, once a larger than stock MAF is used, you need to tell the computer so that the correct MAF curve can be used, thereby insuring that your engine is recieving the appropriate amount of fuel as it relates to the amount of air being ingested. There are a number of different solutions that we will discuss.
5.2 - Tuning Options
In a nutshell, you have the following options when it comes to tuning your turbocharged SHO. Send your information (engine size, injector size, MAF curve, modifications, etc etc) to a tuner, who in turn will flash what we in the SHO community call an LPM (Lifetime Performance Module). This small piece of hardware will 'piggyback' onto your stock EEC-IV computer, and change the computers strategy to reflect your current modification level. This is the simpliest way to get up and running, as it requires no knowledge of the EEC-IV, no tuning expertise, and is relatively inexpensive (around $250-350). But, it also has it's limitations. To make any adjustments to your tune, you have to remove the hardware and send it back to the programmer for a 'reflash', rendering your SHO a very large paperweight. And, every time you make a significant change to your system, you have to remove the hardware and send it back to the programmer for a 'reflash'. If you want to run more boost, you have to remove the hardware...well, you get the picture.
Next, you can invest in a user programmable piece of hardware, one that still 'piggybacks' onto your stock EEC-IV computer, but which can be 'reflashed' any time you see fit, either via laptop computer, or with it's own special handheld tuner. Examples of these include the TwEECer, X-Cal, SCTuner, and others. The ONLY one I have any familiarity with is the Tweecer. It has worked wonders for my car, and I am very pleased with it's results. That said, I have heard wonderful reports from other SHO owners that have used other means to tune their SHO's. In the end, do your research, see which will work best for you, as you are the one spending your hard earned dough.
Also, you can use what is referred to as a 'stand alone' ECU. In other words, you remove the stock EEC-IV computer, and replace with a different computer. An example of this would be the AEM EMS. Since I have absolutely no experience in this arena, this paragraph is over.
There are also band-aid products like airflow converters or MAF extenders, but I do not recommend the use of these. Hey, this is my 'HOW-TO'. If you don't like it, write your own.
5.3 - Whoops! I blew up my SHO!
TURBOCHARGING YOUR SHO
PART 1 - Two important questions
By far the question I am asked most often, and which I see most often in the various posts by those interested in turbocharging their SHO, is this: Will this turbo work for a SHO? The answer: YES. Every turbo will work for a SHO. How well it will work is an entirely different matter. To that end, I highly recommend that anyone interested in turbocharging their SHO asks themselves two very important questions, as the answer to these questions will outline their entire project. Question #1 - What is my budget? Question #2 - What is my intended usage?
1.1 - What is my budget?
Now, you may wonder, what does my budget have to do with my turbo selection? Well, not only do turbochargers themselves very greatly in price, from cheap chinese ebay knock-offs (less than $300) to super trick ball-bearing units from name brand manufacturers ($2000+), but the capability of the turbo has everything to do with the modifications needed to support that capability. In other words, it makes no sense to spend a large amount on a turbocharger if you do not also plan to spend a large amount on the supporting hardware needed to extract the peak performance of said turbocharger. So, sit down with paper and pencil, and give yourself a budget. Way too many projects are started without a clear budget in mind, and many of those projects are abandoned once the cost exceeds initial expectations. Hopefully, with a realistic and honest budget, and by purchasing parts that fit that budget, you will be much more likely to see your project to completion.
1.2 - What is my intended usage?
Is this going to be a weekend toy? A daily driver? An all out track weapon? A dragstrip warrior? The ultimate highway Supra-killer? Again, ask yourself honestly, what do I want this car to do? Because the best turbocharger for a monster standing mile car is not necessarily the ideal choice for a daily driven commuter. The SHO engine, with the proper supporting mods, is capable of making WAAY more power than the drivetrain can handle. Do not let an insane HP goal cause you to build a car that is no fun anywhere accept above 6000rpms. That said, there are a number of turbocharger selections that will allow the SHO engine to have a very broad and usable TQ curve, while providing a very nice high rpm HP rush.
PART 2: Turbo selection
So, we have already answered what our intended usage is, which in large part is decided by our budgetary constraints. Now we are ready to pick a turbo to match our needs. But how? As you have surely noticed, there are a MYRIAD of choices when it comes to turbochargers in comparison to superchargers. The reason being, a turbo is entirely dependant on the exhaust of the engine to drive it's turbine and compressor. A supercharger does not have to worry about this. It is going to move a certain amount of air at a certain RPM regardless of what vehicle it is on. So you end up having much less trim choices. Most of us are familar with the Vortech S-trim and T-trim correct? Consider this the compressor side of the turbo. Only with turbos, there are a LOT of compressor choices, in different trims within each compressor family. The pulley size of a supercharger has a large effect on it performance. Consider this the turbine side of the turbo. Only with turbos, there are a LOT of turbine choices (not just the turbine itself, but the A/R of the turbine housing). Sound confusing? Well, it can be. But we are already ahead of the game, because we have answered what our intended usage is, and what our budget will be. So, we can simplify things. All we really have to worry about is finding a turbo whose compressor map matches the needs of our build, and that brings us to the next section.
2.1 - Compressor maps
Now, this section is not going to go into detail about how to read compressor maps, or the importance of A/R ratios, or certain trims of compressor wheels. It is simply a broad overview, but if you can grasp the fundamentals, it will get you in the ballpark of where you need to be concerning turbo selection. First, let's take a look at a compressor map. This is from a Turbonetics 62-1.
As you will notice, this is a simply X Y axis graph to plot the airflow capabilities of this certain compressor. To the left we see PRESSURE RATIO, and along the bottom, AIRFLOW. The ovals in the middle are EFFICIENCY ISLANDS (the higher the percentage, the better use we are getting out of our compressor), and the arcs are a measure of the compressor's RPM. The dashed line along the left is the SURGE LIMIT. These items will tell us all we need to know about our compressor selection (we will get to turbin A/R later). The pressure ratio is just that, a RATIO of our intake manifold pressure (actually compressor outlet pressure, but for this discussion we are simplifying things) plus atmospheric pressure (actually compressor inlet pressure) divided by atmospheric pressure. Now, lets assume we are considering this turbo. Our intended usage is a modest daily driver, our budget is small, so we will be using stock injectors/MAF/tuning, and stock engine internals, and no intercooling. With that, our HP limit is around 300chp. Is this turbo a good choice? Let's have a look. The AIRFLOW axis, measured in LBS/minute, is an approximate indicator of how much HP you will be making. 30 lbs/min equates to approximately 300chp. Our stock non-IC engine will only like about 10psi. But there is no PSI markings on this graph you say. Correct, only PRESSURE RATIOS. So what pressure ratio does 10psi equate to? This is the equation - intake manifold pressure (IM) plus atmospheric pressure (AP) divided by atmospheric pressure (AP). So, IM (10psi) plus AP (14.7psi) divided by AP (14.7psi) = Pressure Ratio (PR)...(10spi+14.7psi)/14.7psi = PR...24.7psi/14.7psi = PR...1.68 = PR...PR = 1.68. We simply add our expected manifold pressure to 14.7 and then divide that sum by 14.7 to get our PR. To make it easy, at the end of this section is a breakdown of all psi levels as they equate to PR, from 5psi to 25psi. Now, back to our map. We have our PR of 1.68 (let's call it 1.7) and our airflow of 30lb/min (300chp). Let's plot those out on our map.
From looking at our plotted points, and our map, does this seem to be the best compressor choice for our needs? Technically, this turbo will meet our HP desires (with no problem of course), we are in a good efficiency island, but as we can see, there is a LOT of turbo left on the table. And with our mostly stock components, we will never see the full capacity of this turbo, and due to it's larger size, turbo lag will be a factor. I bet we can find a more suitable compressor, one that will nearly elimate lag, and still provide enough room for HP growth down the road. Take a look at this compressor map, with the PR and airflow plotted, to see what I mean.
This is a T04B turbine/H3 compressor section (old nomenclature, not sure what turbonetics would call it now). Our PR/airflow plot puts us almost right in the middle of the best efficiency island. And as we can see, if we wanted to up the boost some, perhaps after we made some injector/MAF/intercooler upgrades, we could easily make 350chp, and still be right in our best efficiency island. This would be the better choice considering our intended usage and budget.
As another example, let's us assume we have a large budget (one that allows for a Tweecer, forged pistons, upgraded fuel system including large injectors, intercooling, etc), and we want a beast of a SHO, something in the neighborhood of 450chp. Will this T04/H3 work well for us? It will probably take around 15psi (a PR of just over 2.0) to achieve that number. Let's add those numbers to our map.
Now we can see that we have went from nearly a 74% efficiency down to around 67%, and are at the edge of this turbo's capabilties. Will it work? Yes, it will make the power we want, but can we find a better suited compressor? Let's take another look at the 62-1 we saw earlier, with the new numbers as well.
Ahh, now we are talking! We can make our desired 450chp, and we are well within the capabilities of our turbo, in a high efficiency island, and still have plenty of room to grow should we desire to run more boost.
So, do we begin to understand the importance of proper compressor selection? As we stated at the outset, nearly ANY turbo will work on the SHO, but how WELL it works is what is important to us. And by having a good idea of our budget and intended usage/HP goal, we can narrow those hundreds of options down to just a few.
psi vs pressure ratio table:
5psi = 1.34 PR
10psi = 1.68 PR
15psi = 2.02 PR
20psi = 2.36 PR
25psi = 2.70 PR
2.2 - Turbine A/R ratio
Now, about the turbine A/R. Without going into great detail, the A/R is defined as the inlet cross-sectional area divided by the radius from the turbo centerline to the centroid of that area. In simple terms, a smaller A/R increases the velocity of exhaust gas powering the turbine, at the expense of more backpressure, which will reduce the capacity of that particular turbine and effect high rpm performance. A larger A/R decreases the velocity of the exhaust gas powering the turbine, decreases backpressure, increases boost lag, but lets the engine breathe better at higher rpms (something our SHO's love to do). For instance, two identical turbocharger compressors, one with a 0.63 A/R, one with a 1.21 A/R. The smaller A/R turbo will boost very quickly, which will effect the TQ curve dramatically, giving LOT of low end grunt, but sacrificing top end HP. The large A/R turbo will breathe VERY well at high rpms, and make lots of top end power, but will have more boost lag, which will effect the low end TQ. The same turbocharger, but they make their power very differently. I would go so far as to say that A/R selection is MORE important than compressor selection, to a point. For example, my last turbocharger was a T3/60-1, with a smallish A/R (around .63 I think). That car made LOADS of TQ at low RPM, and had very quick turbo spool. My current 62-1 has an A/R of .81. It builds boost a little slower, but it also breathes much better at high rpm. While the old turbo outshined this one for TQ production in rpm's below 5000, it only made useful HP to around 6000rpm. My current turbo still makes great TQ, but due to the larger A/R, it lets the engine breathe much better at high rpm, so that @ 7000 rpm it is making a LOT more HP than my old turbo (and more TQ). Lastly, note that compressor housings do not generally come in differing A/R ratios, as they have much less effect than the A/R of the turbine housing. Also, keep in mind that the compressor maps we looked at above are only a measure of the COMPRESSOR's capability, and do not take into account engine size and speed or turbine A/R, all of which will have a great effect on performance. But fret not, this does not make the compressor maps useless. Just remember that they are more of a guide than an actual blueprint of turbo performance.
PART 3 - Exhaust Piping
So, we have out turbo picked out now, but where do we put it? Certainly, there are a number of choices, each with it's own advantages and disadvantages. There is at least one of each of the following type of turbo powered SHO on the road right now: rear remote mount (strings), engine bay (in place of stock filter box, as seen on my car, Power Surge, NCtaurusSHO and others), and subframe mount (in the case of somedude's ATX SHO). Since my area of familiarity is with the engine bay mounted turbo, that is what the references in this article will deal with. One of the main reasons there have been so few turbocharged SHO's is because of the problems associated with fabricating the pipes responsible for carrying the hot air charge to a suitable location in the engine bay. As you are all aware, there simply is not a tremendous amount of free space under the hood of the SHO. And routing HOTHOTHOT pipes up near delicate wires/hoses/electrical components is no task for the uninformed. This is why turbo placement under the hood is usually limited to the airbox area. On my setup, a y-pipe collects the rear exhaust and routes it toward the front of the car, joining up with the front manifold to form an uppipe routed between the engine and fan shroud. Here is a picture from underneath the car.
It terminates right above the ABS block, to place the turbo in the stock airbox location. The ABS computer and ICRM are both relocated slightly to allow for plenty of room between them and the hot pipe. Also, I have cut down the neck of the thermostat housing and fitted a stainless steel radiator hose for better clearance. So far, in over 55k miles of driving, no failures of those parts has been experienced.
Now that we have a turbo placed in this general area, we have to provide it with fresh air, and make room for intercooler piping if we are running one (and an IC is always recommended). On my car, I removed material from the driver engine bay wall to allow for placement of a 3" inlet pipe. The open element conical filter, attached to the 80mm Lincoln MAF, resides in the fenderwell area fore of the front tire. This area provides clean cool air, with little worry of splashing water up into the filter element.
With so many options available for intercoolers, for now we will leave this area alone. Later I will include some pics of my current setup, as well as a new setup I have been working on.
With the turbo placed in the position described above, the exhaust must be routed towards the back of the engine bay. There really is only one route here, with the downpipe finding the room between the firewall and transmission (there is a small space just to the passenger side of the speedometer cable). It is tight here, with the downpipe actually against some cables/wire, so care must be taken in wrapping the downpipe, and also in insulating the surrounding wires/cables. Once past the intermediate shaft, the downpipe connects up to your choice of 'catback' exhaust (I have no catalytic convertors on my car, and am making no provisions for one in the upcoming downpipe). While we are on the topic of exhaust, I think it is safe to stay that a completely stock exhaust system will not provide much restriction for low boost/low HP systems (300hp). And the popular dynomax or other 2.5" systems out there will likely flow up to 400hp with no problems. Above that, you will likely need some type of custom exhaust. The one pictured below is in use on my current SHO, it is a 3" mandrel bent system with a single Thermal Dynamics muffler. A system such as this should be able to flow in excess of 700hp.
Part 4 - Fuel system/engine upgrades
4.1 - Fuel system upgrades
No matter what our goal, the main purpose of turbocharging our SHO is for an increase in HP and TQ. The turbocharger does it's part by cramming the engine with more air than it could take in if it were naturally aspirated. But air is only part of the equation. Without the adequate fuel to mix with that incoming air, no more power will be had. There is no need to go into detail about duty cycles and pulse widths and other minutia of fuel injectors. Suffice it to say that if we are turbocharging a SHO, we will want to upgrade our injectors and fuel pump. The stock system can support close to 300chp, but to do so it will be operating at near 100%, and it is always a good idea to keep a safety margin when it comes to fuel. Run your car too lean, and bad things can happen.
Just how much modification needs to be done? Again, it all depends on what our HP goals are. A small turbo/low boost system could get by with 39lb injectors and a 155lph pump, enough to support 350chp with no difficulty. For reference, my last turbo SHO used a 190lph pump and 47lb injectors, and supported 505+chp through the stock fuel lines (using an FMU). I eventually upgraded to the SHONUT hi-flow fuel system, which incorporates dual feed lines from the regulator to the rail, a larger feed line from the the tank, and an adjustable FPR. My next project has a 255lph high pressure fuel pump to insure that I will always have plenty of fuel. Even larger injectors can be had for the SHO, some people are using 63lb'ers right now, which will probably be my next choice. But most people will never need anything larger than the Accel 48-lb injectors, a quality 255lph pump, and an aftermarket FPR, as those items will reliably support upwards of 525chp in a well tuned turbocharged SHO.
Keep in mind that some injectors will require you to modify your fuel rails to accept them. Others are available that will fit a stock rail with no modification. Do your research and know what you are buying. Also, DO NOT USE AN FMU! Yes, the original turbo SHO ran one for years, and the FMU provided plenty of fuel. But lack of fuel is not a weak spot for FMU's. Lack of tuning abililty is. I can not stress how much better this car runs now that I am using a proper FPR. Idle quality is MUCH better. Driveablity is MUCH improved at all throttle positions. And fuel mileage is much better, with my last road trip allowing me a 26mpg fillup (with average speed well above the posted limit). FMU's can work, but they should be viewed as a temporary bandaid only.
4.1 -Engine upgrades
Sure, we all want a 3.2 low compression forged engine with a knife-edged crank and shotpeened rods, and we want to bolt on p+p heads stuffed with the meanest camshafts known to man, breathing through extrude honed runners and BBB's. So does that mean that if you don't have the deep pockets needed for such items that your dreams of owning a turbocharged SHO will never be realized? Of course not. If you own a SHO, any SHO, you already have one of the more robust and capable engines ever offered in a Ford sedan. The stock rotating assembly (save for the pistons) of any well maintained SHO will withstand the abuse of over 750hp. VERY few stock engines can make that claim. My last turbo SHO has as it's ONLY engine mods the following - overbore to 3.2L, forged low CR pistons. But the heads, cams, intake manifold, throttle body, exhaust manifolds, rods, crank, etc, etc, etc are all BONE STOCK. There simply is no need to spend huge amounts of cash of a laundry list of engine modifications when you are planning a turbo SHO project. Save your money and concentrate getting high quality turbochargers/WG's/BOV's and the needed fuel system and tuning upgrades. The only engine upgrade I will strongly encourage is that of forged pistons (a slight drop in compression ratio is desired as well, for reference, mine are 9:1, down from the stock 9.8:1). Forged pistons are better suited than the stock hypereutectic pistons to withstand the extra pressure and heat that turbocharging introduces. If you plan on running anything more than 15psi, plan also on getting forged pistons.
Certainly, once one has eeked out every last ounce of HP they can from their current turbo system, and they still want more, the above mentioned camshafts, head work, EH intakes, etc, etc can give nice HP gains. But IMO, it is more worthwhile to concentrate your effort and time and money to other areas of the car that are not up to the task of putting up with the demands of a 400+hp 3400lb sedan. Bigger brakes, suspension upgrades, a Quaife. With even a mild turbo system you will already be making enough TQ to snap your fair share of third gears. More power will only hasten the demise of your transaxles. Of course, I know full well that plenty of you will disregard what I say and do everything you can to that Yamaha gem so that you can brag about having the most powerful turbo SHO on the planet. So to that end, I feel it is my obligation to stay one step ahead of you. But that is a discussion for another time and place...
Pertinent pics will be added soon, stay tuned for updates.
Part 5 - Tuning your turbocharged SHO
5.1 - Why do I need a tune?
While many modifications to the SHO can be performed with great results and without making any changes to the stock EEC-IV programming information, the airflow capacity of a turbocharged SHO is simply too much for the stock strategy. To that end, there are some changes that we are going to have to make. Already mentioned were the fuel upgrades that are necessary for your venture. Once larger injectors than stock are used, you must have some way to tell the computer so that it can adjust for the different fuel flow. Also, the stock MAF meter will only be able to meter about 300chp, a number very quickly eclisped in even the lowest boost turbo SHO. Again, once a larger than stock MAF is used, you need to tell the computer so that the correct MAF curve can be used, thereby insuring that your engine is recieving the appropriate amount of fuel as it relates to the amount of air being ingested. There are a number of different solutions that we will discuss.
5.2 - Tuning Options
In a nutshell, you have the following options when it comes to tuning your turbocharged SHO. Send your information (engine size, injector size, MAF curve, modifications, etc etc) to a tuner, who in turn will flash what we in the SHO community call an LPM (Lifetime Performance Module). This small piece of hardware will 'piggyback' onto your stock EEC-IV computer, and change the computers strategy to reflect your current modification level. This is the simpliest way to get up and running, as it requires no knowledge of the EEC-IV, no tuning expertise, and is relatively inexpensive (around $250-350). But, it also has it's limitations. To make any adjustments to your tune, you have to remove the hardware and send it back to the programmer for a 'reflash', rendering your SHO a very large paperweight. And, every time you make a significant change to your system, you have to remove the hardware and send it back to the programmer for a 'reflash'. If you want to run more boost, you have to remove the hardware...well, you get the picture.
Next, you can invest in a user programmable piece of hardware, one that still 'piggybacks' onto your stock EEC-IV computer, but which can be 'reflashed' any time you see fit, either via laptop computer, or with it's own special handheld tuner. Examples of these include the TwEECer, X-Cal, SCTuner, and others. The ONLY one I have any familiarity with is the Tweecer. It has worked wonders for my car, and I am very pleased with it's results. That said, I have heard wonderful reports from other SHO owners that have used other means to tune their SHO's. In the end, do your research, see which will work best for you, as you are the one spending your hard earned dough.
Also, you can use what is referred to as a 'stand alone' ECU. In other words, you remove the stock EEC-IV computer, and replace with a different computer. An example of this would be the AEM EMS. Since I have absolutely no experience in this arena, this paragraph is over.
There are also band-aid products like airflow converters or MAF extenders, but I do not recommend the use of these. Hey, this is my 'HOW-TO'. If you don't like it, write your own.
5.3 - Whoops! I blew up my SHO!
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This will definately give me a starting point.
for him?
:laugh_ti:
