Easiest way to boost compression on stock 3.0

[redwraith94]

I want to convert my 89 sho mtx to run on e85, and make as much use of it as possible. I want to keep it naturally aspirated, and boost the compression ratio as high as I can.

1. I don't know how high of a CR I can go on e85, from what I understand pure ethanol is around 104 octane, but I don't know the octane rating of e85.
2. I don't know how boosting CR will affect daily driving, this car won't be going to the track.

I want this car to be as fast as possible, while keeping it na, and in a reasonable budget. So what are your guys' suggestions?

I want to boost the CR, but from what I hear the stock pistons are forged, and very strong.

I have no experience with building engines, so advice is appreciated.

 

[Jarrod]

If you're trying to maintain a budget, but still be as fast as possible, Naturally Aspirated is not the way.....

Raising your compression ratio (all other things equal) will increase the amount of power you make across the powerband, but will require higher octane and carefully tuning to prevent detonation.

The stock pistons are not forged, and you'd replace the pistons in your engine anyway to raise the compression, since there's really no other viable way to do it with our engines because the aftermarket is so small.

What's your reasoning for wanting to stay naturally aspirated? A supercharger from either FPS or NTP will make far more power on even a stock 3.0 than you'll pull out of just about any N/A build, and you'll have a more usable torque to begin with.

Also, the topic of all-out N/A builds has been covered quite a few times, along with specifics on what is and isn't available for our engines when building for either boost or staying naturally aspirated. Check out the Search button on the top of your screen for more info.

 

[Lightning]

Raising compression ratio is easy, all you need is a new set of pistons.

SHOnut has them: http://www.shonutperformance.com/Performance.htm

Of course, if he doesn't have what you want, you can always get a set custom made to your specifications and then you can have pretty much what ever C.R. you want. Just don't expect them to be cheap. Probably save money by boosting it instead.

 

[HotRodKid]

pure ethanol is 116 octane, while e85 is about 105

the stock pistons are not forged, i beleive they are hypereutectic, as ford originaly refered to them as "single crystal pistons"

 

[thecrew2999]

e85 can run some pretty wild compression ratios.. a lot of boosted guys (not really SHO owners) run e85 and get good results.

i dont wanna go over anyones head but if you directly contact wisco piston company they will get you any ration, any coating whatever you want for far less then what was mentioned.
figure about 7 bills for the pistons tho. and if your running high compression i recommend the gapless rings. olny downside is the 5000 mile break in ... yes i said 5000 mile.. chrome moly gapless rings take a lot of breaking in...

no one has experimented with crazy compression rations but would be cool to see someone with a ultra high compression ratio like 12 - 13 to 1

i know the HC 3.3 pistons (which is olny .1 more then 3.2) yeilds 25 hp and im not sure tq which i have heard from all the 3.3 HC guys ive talked to so its worth it if you wanna do that route.

if i was you going HC i would go 3.3 for sure.

i think shonuts HC is like 10.1 or 10.5 i dont remember but i would like to see you go higher then that for sure.

good luck

 

[sho_sc]

There is a limit on the CR. I believe that Josh was working with a Bonneville racer a few months back designing (via Wiseco) HC piston and there is a limit due to the shape of the head, seems it was between 12.5-12.9 :1 . My motorcycle racing friends use the rule of thumb that for each full CR point you raise compression (i.e. 9.8:1 to 10.8:1) you gain 4% torque across the curve.

 

[Racer X]

There's also the issue of what e85 will do to the fuel delivery system that was NOT designed to run e85.

 

[AIrcraftMech]

Too much work for too little

There's also the issue of what e85 will do to the fuel delivery system that was NOT designed to run e85.

True words Racer X. E-85 is not made to be used in a regular engine. After you up grade ALL of the rubber components in the fuel system then you can go out and try to find someone to reprogram all of the perimeters in you computer to get the bennies of the E-85. It's not worth it due to the fact that it would be cheaper to go out and by a newer car that will take either type of fuel. Plus you won't see any type of big gains running E-85. My brother has a Titain and he swears that he gets better mileage and has more power running regular gas than when he runs the E-85. Me, I just cheat. I run 100LL that I get from work. I normally run about 3/4 tank of the 100LL with 1/4 of high test. Ummm, smells so good out the exhuast and gives the car a little more pep. Funny thing is, I have never bothered to check the mileage. Maybe I should do that on the next tank.

 

[somedude_001]

E85 will reduce your power output when compared to gas. the reason for that on your typical car is that the comprssion is not high enough to take advantage of E85s properties (directed at AIrcraftMech) so your buddy with the titan is right. E85=less power and worse milage on a engine optimised for gas.

to convert the fuel system you will need.

fuel pump
metal fuel lines
injector O-rings rated for E85
FPR rated for E85 and one that will pass a higher volume than stock
larger injectors that are rated for E85
tweecer to tune
turbo or S/C +related parts or new pistons

1slickred89 converted his turbo ATX car to run on E85 and had good results. I had planned to do that to my turbo ATX as well but the fuel is still not avaliable in my area

the good:
cooler intake temp
lower EGT
reduced detonation

the bad:
increased fuel consumption (richer AFR)
if you stay N/A you will be disapointed
you will not be saving money

 

[redwraith94]

I want to keep everything na, I like the challenge of trying to find things to improve, more than the raw speed. .8 Gs acceleration is nice, and I really want to improve on it.

I want to see the car run na with the highest possible compression that I can give it, running alkey. Its not that I think alcohol is some super race fuel, but I am set on running alkey in her, after doing a bunch of research I decided to try running my 3.8 buick on about E30 (by mixing with 87) for 4 tankfuls so far. I have lost some mileage in the city, but I want to build the sho to really make use of it.

I saw the pistons before, and 830 is over budget for me, if I was going to save up to spend that, I would really want whatever the max CR is for e85 (pure alkey is too hard to come by to use in a daily driver for me.)

If I can get to the point where the I can boost the CR without breaking the bank, I will get alkey compatible lines (probably teflon), viton seals, a new pump, and a plastic tank, then also injectors that flow probably 25% more, and then just tweak the fuel pressure from there. I am cheap, and tweecar isn't in the budget right now (not saying it isn't great, just want to avoid swapping the ecu.)

I understand that it won't be a huge boost, 10 to 20% boost would be ok with me. From what research I have done I do plan on doing:
Port polish
Cold air intake
Exhaust mods (not sure about which parts will be replaced yet)
Acid dipping parts, and then putting down 1 layer of carbon fiber cloth / por15 on each side. I plan on doing this to the hood, and trunk at least, and maybe the roof, doors, and quarter panels.

I need a hobby bad, and love cars, I wanted an engine to tweak, and the sho seems to be the perfect engine, just begging to be tweaked.

I just bought a set of used Titanium Intake Valves that need to be ground down. My friend that I am in the process of buying the sho from has the setup to grind valves, and owns a machine shop. I know this won't net me horsepower, but I am aiming for revvability, and component life.

I appreciate all the feedback, since the pistons are cast, how much of a CR boost do you guys think the stock pistons could handle?
On na, what is the highest CR that you guys have heard of?
What other options do I have to boost CR, other than a piston swap?
What is your opinion on hypereutectic pistons, could they handle a boosted compression ratio, this car will never see boost, but I have no actual experience with this, just alot of article reading = squat.

Since the Titanium valves are lighter, I want to switch to lighter springs (I'll weigh both the tappet, and valve to figure how much lighter of a spring I can go.)
Can I grind the face of the valve down, (possibly on exhaust too, or maybe use inconel exhaust valves, and grind them down) then face mill the head down a bit?

Only ways that I know of to boost cr:
swap pistons
face mill head
overbore cylinders (stock head)
thinner head gasket

I know this is a stupid idea, but my mind requires me to ask. The head is cast aluminum, can it be welded to fill in space (with an alloy with that has the same expansion coefficient as the head)? Has anyone ever heard of the head being weldable, or this way too far fetched?

I have lots of ideas burning a hole in my brain, and I wish to try them, I don't have crap loads of money, but I do have a fair amount of time, and a fair bit of money, but realistically for new pistons I can't go over 2 grand. Is that a laughable sum? I dunno, could I get 14:1 pistons for that price, that wouldn't die at 7-8k rpm? again I dunno. I don't even know what CR ratio I can run on e85.

This is my car to tweak, and test ideas, so your thoughts are appreciated, because I am basically starting my car modding years from scratch here.

 

[redwraith94]

I thought that ideally doubling the compressions from 10.5 to 21 (not that I could actually near 21, she isn't a diesel would almost double the power (minus all the friction, etc.) but that basically power increased almost equally (minuse friction) with CR. Am I way off here?

 

[rudedog]

Personally I think the op should start by reading all he/she can about engines/theory/ and the like. since this person ahs stated that they have no prior knowledge of the subject. You guys sprouting all this info is cool and all but jumping into HC on any car is a big deal, and jumping into HC on a SHO is quite another. Simply just doing maintenance breaks some of you guy's bank rolls, let alone doing big technical modifications. Not saying the person isn't able, just sayin'.

 

[egroce11]

redwraith94
I'm running just over 11-1 CR on my N/A motor some friends of mine are running 12-1 on an N/A motor in a super modified car. Just a quesstion thou: why are you thinking of going with a lighter valve spring? These motors can and do run at some ungodly rpm's I really believe that if you go any lighter on the springs the valves are going to float.


Ernie

 

[sho_sc]

Only ways that I know of to boost cr:
swap pistons
face mill head
overbore cylinders (stock head)
thinner head gasket

I know this is a stupid idea, but my mind requires me to ask. The head is cast aluminum, can it be welded to fill in space (with an alloy with that has the same expansion coefficient as the head)? Has anyone ever heard of the head being weldable, or this way too far fetched?

Swap Pistons - Yes
Mill Head - No , with DOHC and milling it throws cam timing off.
Overbore Cylinders - ?? , requires new pistons.
Thinner head gasket - Kinda, Only 2 type of head gaskets work. MLS and Cooper. Custom MLS will cost you more than your budget and it won't raise compression that much. Cooper must be retorqued often, PITA to do on a SHO.

The combustion chamber is very limited to modification. With 4 valves and a spark plug, they ain't much room left to fill.


In addition, raising fuel pressure on a NA motor to increase fuel delivery won't work. The EEC (computer) "learns" it's way around the increase fuel pressure, plus you are limited to how much pressure the intank pump will take before it fails.

 

[redwraith94]

Personally I think the op should start by reading all he/she can about engines/theory/ and the like.

I have, basically I want to improve horsepower in stages, first stage is raising compression, second stage is raising rpms. I want to keep it na, and buying new pistons is an option, but not if they cost 7 grand.

In order to do that though, I have purchased some used Titanium intake valves, that I will grind down to fit the sho. This is for reliability, and increasing rpms. I know rpms won't do anything without modifying the intake, and exhaust.

Ernie, the first thing that I am doing (in the way of a major mod) is to get titanium valves, my idea here is that they may need to be heat treated, and if they do I will do that first, then grind them done, and an associate of my old chem professor puts plasma nitride coatings on things for a living. So I will contact him about coating the stem, and valve seat.

I am just trying to find reasonably priced ways to boost cr, but I don't have experience building motors, the most I have done so far with cars is Lower intake manifold gasket on the buick, differential side carrier bearing on my tempo, and general parts like alternators, water pumps, fuel pumps, and that kind of thing.

Raising compression ratio is easy, all you need is a new set of pistons.

SHOnut has them: http://www.shonutperformance.com/Performance.htm

Of course, if he doesn't have what you want, you can always get a set custom made to your specifications and then you can have pretty much what ever C.R. you want. Just don't expect them to be cheap. Probably save money by boosting it instead.

I can't go 830 per piston, but when I click the link it says it is only 415? I would assume this is per piston, and if so I could pull it off, but I still don't know what compression ratio to go for on e85.

I see keith black / speed pro hypereutectic pistons on summit for like 200 for a set of 8. I know that forging is more expensive, but do I really need forged? Would hypereutectic be able to handle a 14-16:1 cr, if e85 can go that high normally?

I figured that raising cr to 14:1, up from 10.4:1, would be similar to running 6lbs of boost, in terms of stress on the crank, pins, rods, and pistons. since 1 atmosphere is 14.69 psi, x 40% = 5.876 psi.

 

[HotRodKid]

$830 is for a set of 6 pistons
415 is the price due to the "half now half when they are made" payment system shonut uses

6psi is more stressful then switching from 10.4:1 to 14:1

 

[Kens1992mtxSHO]

I remember seeing a thread about someone wanting to do the same thing a few months ago...

 

[redwraith94]

$830 is for a set of 6 pistons
415 is the price due to the "half now half when they are made" payment system shonut uses

6psi is more stressful then switching from 10.4:1 to 14:1

omg, I feel stupid. Then I guess new pistons it is.

 

[redwraith94]

Swap Pistons - Yes
Mill Head - No , with DOHC and milling it throws cam timing off.
Overbore Cylinders - ?? , requires new pistons.
Thinner head gasket - Kinda, Only 2 type of head gaskets work. MLS and Cooper. Custom MLS will cost you more than your budget and it won't raise compression that much. Cooper must be retorqued often, PITA to do on a SHO.
...
In addition, raising fuel pressure on a NA motor to increase fuel delivery won't work. The EEC (computer) "learns" it's way around the increase fuel pressure, plus you are limited to how much pressure the intank pump will take before it fails.

I meant that I would go for over size injectors (in the range of 25% more) to handle the e85, and then use the pressure regulator to adjust the afr, when the ecu is in closed loop mode, just for startups, and such.

I intend on purchasing a new fuel pump to handle the e85, I seriously doubt a stock ford unit would, as I owned a tempo for a few years, and my god that was a piece of crap..plastic spacers for the differential side carrier bearings FTL.

I also intend on purchasing new oxygen sensors, probably bosch, unless someone else knows of a better brand. This way the ecu shouldn't have to adjust to much to maintain stoich during normal driving.

I don't suppose that a stock head gasket would handle 14-16:1 cr, but how much would a custom mls gasket run me, and how much would I be able to shave off the gasket thickness, before it becomes an interference motor?

 

[redwraith94]

Well i realized that boosting compression by 25% (from 10.4, to 13) would only net me about 10% boost in power. I don't want to go through the trouble of getting the block honed, bored, and balanced with new pistons.

So I purchased a set of heads from Eric, and I will be trying to fill in the combustion chamber with a bit of weld.

First I have to see what alloy the heads are, if it is weldable, and then I need to find it's expansion coefficient. I will be trying to fill in the space on the side of the combustion chamber. I calculated that I need 8-10 cc's of metal to boost it to a high 12 - 13:1 compression ratio.

Thinner head gasket - Kinda, Only 2 type of head gaskets work. MLS and Cooper. Custom MLS will cost you more than your budget and it won't raise compression that much. Cooper must be retorqued often, PITA to do on a SHO.

I will look around on the net, but do you have any more info on the Custom MLS ?