Sad to hear at such a low mileage use. Have you had them apart? what was diagnosis for failure? If you posted failure I might ha e missed it.
Knock knock
- Thread starter 810sho
- Start date
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Cr performance said, debris lack of oil or over speed. I didn’t personally have them apart but the impeller shaft was broken in half and the impeller was embedded in the housing (both times, stock and upgraded) only on the front turbo though. Backs were fine to the eye, so I assume it was a oiling issue, maybe the lines were clogged, there was debris in the engine when I pulled it apart and unfortunately I didn’t rebuild it the first time so I do not know if the lines / screens were cleaned before hand, this time all of it was replaced, right after I rebuilt it this time I was having a problem with my knock sensors detecting, I flashed back to stock went back to gearhead a/o tune and it was fine, I noticed the knock in the engine when I was doing a crank relearn, because I changed the sensors I wanted to do the procedure and when I did I heard the knock on deceleration, and that’s where this thread starts,
considering the di setup would cause no change to the harness/ pcm is why I would never change to a non di setup it would cause way more of a headache than it’s worth and essentially take a step back, it’s redundant at that point, also there is not a lot of physical evidence that the walls become a issue, why wouldn’t it be advised to take displacement now over later?
Also the plan is to used oversized ecoboost pistons and I beam connecting rods. For the price of pistons rods and a complete 3.7 is still as cheap as buying a used 3.5. With the gen 1 3.7 engines going for around 800 bucks near me that seems like a solid investment with what data is provided from the 3.7 community, I’ve talked to super six (I know they are disliked on these forums) but they do this for a living they have found no evidence that sleeving the block makes a difference at the power level I plan to run, tom at super six was asked “do you run closed deck blocks on your 4.0l stroker setups” his reply was “no. The difference is negligible”
Like I understand. I get the point, I already have a 3.5 why go through all this work to be limited by turbo size , maybe I’ve transitioned from seeing this car as a daily to seeing it as a project, it’s been in the garage more than I’ve driven it in the last 2 years because of turbo failure/ engine failure, I might as well build something that I enjoy rather than be like every other built sho I’ll be different, may be respected for that maybe hated, but when someone asks about the build I can elaborate and share knowledge that I’ve gathered from the process to shed insight on if it’s at all feasible/ reliable or not, I’ll reap what I’ve sewed when the time comes If it doesn’t work out which I’m not finding too much evidence that it will not work
what’s the reason the 3.7 mustang stock short block guys are making 500 hp at 10pounds of boost and 600+ whp at 14psi running mid 9 second passes, and from what I’ve seen it’s typically piston/ rod failure before block failure on these engines, 3.5 eb hot side is limited?
Is there a actual viable reason that’s backed by research and testing on why not to use a 3.7 or is it all speculation? I’m genuinely curious, no one has provided solid evidence that there’s a difference between the 3.7 fwd blocks and rwd blocks beside bell housing and if that’s true and the 3.7 fwd blocks are identical other than bell housing there is plenty of proof that the 3.7 makes great power on boosted applications there are I believe 4 or 5 on YouTube alone that make more power with less boost than any 3.5 eb engine, the only serious concern is how di pistons are shaped to control where the gas ends up in the chamber, centralized around the plug improving the combustion process aiding in a more complete burn of fuel.
The only other concern is the transmission after a certain power level they don’t live anyway, but if there ever is a readily available upgrade path then I’ll be ahead even if it’s .2l
my question is seriously why not ? There is no recorded evidence that is concerning other than piston type, the connecting rods are the same, crank is the same, deck hight is the same, block is the same, and I’ve not seen any proof to combat that statement.
Is the hot side specifically Why you suggest increasing displacement wouldn’t make a difference?
i would genuinely like to see more information on the cylinder wall thickness making a difference, and if it doesn’t why wouldn’t starting at a larger displacement be just fine
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I suspect playing Mr. Potato Head might present more headaches than you're anticipating, more than changing some wires. When you bastardize the combustion chamber I just feel like you're going to have a mountain of tuning work to do. Without a doubt there will be big changes in the dynamics of those chambers, both in terms of air swirl/tumble and fuel stratification. Call me a worrier, but I see the potential for LESS power doing this.
If the plan is to build the motor anyway, then what does the cost of a used 3.5L have to do with anything? Your cheapest option is rebuilding the engine that you already have instead of throwing away $ on another block and custom made head gaskets. Also where does one find a 3.77" "ecoboost piston"? Sounds custom, and more $$$.
I'm sure it'll probably "work" but you're not going to gain anything for your efforts. If you just want to be different then all the power to you. And kudos for your intention to share the lessons learned.
For starters, drivetrain losses. Then, big laggy turbos that are turds below 4500 rpm coupled with 1000 hp rated intercoolers and full E85 fueling. Weight, suspension, tires, launch strategy... There's no magical horsepower secret sauce in the 3.7 engine itself, and if there were it would be in the heads that you plan to discard. It seems this where you are leading yourself astray, thinking you'll net some big gain from drawing false parallels with a different platform and entirely different setup. The extra 0.2L of displacement is equivalent to 1.6 psi of boost. You'll make the same power, at 1.6 psi less boost. You won't make any additional power because either your turbos are at their limit, your fuel system is at its limit, your rods are at their limit, or all of the above. You probably won't even see improved IAT from the lower boost since you'll just be pushing the turbos further out of their efficiency range. Also if we're diving harder into anecdotes, how many LeMans wins does the 3.7 cyclone have under it's belt? Why doesn't Roush Yates use 3.7 or 4L displacement? They've pushed the 3.5L to about 1000 hp. How come 3.7 mustangs are topping out at 600 hp, but 2.3l mustangs are hitting 800 hp AND SWITCHING TO 2.0L BLOCKS TO DO IT?
That would be a great question for real race teams with real research and testing. "How come you guys can run 600-800 hp all day on your 3.5L but Auto Mafia has a pile of broken engines from same HP and less torque than the 3.5L ecoboost crowd?"
Truly, you won't. That's my whole point and caution to you. You'll be equal at best, as long as you don't ruin things with the ill-paired combustion chamber and piston.
Auto Mafia has a recorded collection of broken engines in their shop. They even talk about how they keep blowing rings out of them. How about that? More below.
Yes and no. Yes the turbines of this platform are extremely restrictive. But no our specific turbos aren't particularly relevant. Like I said above, 0.2L is a difference of 1.6 psi. Just turn the boost up. Can't? well then your turbos are already at their choke point anyway and can't move more air mass no matter what you do, or because you're being held back by some other limiting factor.
A lot of it is kinda common sense. Honda guys don't build 2000 hp 2.0L's without jacketless billet blocks. And it's not because they just like throwing money away. Here's a quick article I found to wet your whistle- https://www.musclecardiy.com/performance/how-to-build-racing-engines-cylinder-blocks-guide/
Auto Mafia suggested in a vid that their engine failures usually start with ring failure and massive blow-by. From the above article:
Just because nobody has taken the time to acknowledge the 3.7L's wall thickness as the problem, doesn't mean it's not the problem. Of course, I don't know either but from my quarterback armchair it seems like a DUH situation.
Whatever you do, good luck with it!
@stripSHO, I’m glad you chimed in, I guess I never assumed the Nuances of all at hand, and I suppose I need to research engine theory a bit deeper.
Reason I didn’t assume the chamber would be significantly different is because I would be using the correct heads, and pistons with the correct compression height I wouldn’t assume there would be a difference in piston height, which would theoretically not change all of the other factors playing into that. quench, compression, valve clearance. But until it’s measured I guess it’s schrodinger's engine. But there are facilities that make oversized ecoboost pistons, they go for around 1000usd which isn’t far off of the 3.5 piston price. I’d like to know specifically if the cylinder is the cause due to distortion under load, I get that theoretically, it would deflect and become un-perpendicular but is that actually what we’re seeing with these blown up 3.7s or something else?
With auto mafia blowing engines, I suppose I thought it was a ring gap issue over a cylinder wall issue, sense that’s a common occurrence on untouched na engines that get boost, I didn’t assume the cylinder walls were deforming that much to make it the sole problem over ring gap due to the fact that the built 3.5 bottom end engines are typically rated to around 700 without a closed deck, I didn’t think the cylinder walls would loose that much structure.
Reason I was questioning hot side is because of the larger turbine for the compressor side I am already running with the upgraded turbos, I was thinking of the possibility of increasing hp per cylinder due to the larger cylinder size, but I suppose if the turbos are already hot side limited larger cylinder size would effectively do nothing until that restriction is gone.
I guess block condition will be the decision maker when I pull the 3.5 out of the Taurus.
Also what’s the formula to determine the 1.6 psi difference
Reason I didn’t assume the chamber would be significantly different is because I would be using the correct heads, and pistons with the correct compression height I wouldn’t assume there would be a difference in piston height, which would theoretically not change all of the other factors playing into that. quench, compression, valve clearance. But until it’s measured I guess it’s schrodinger's engine. But there are facilities that make oversized ecoboost pistons, they go for around 1000usd which isn’t far off of the 3.5 piston price. I’d like to know specifically if the cylinder is the cause due to distortion under load, I get that theoretically, it would deflect and become un-perpendicular but is that actually what we’re seeing with these blown up 3.7s or something else?
With auto mafia blowing engines, I suppose I thought it was a ring gap issue over a cylinder wall issue, sense that’s a common occurrence on untouched na engines that get boost, I didn’t assume the cylinder walls were deforming that much to make it the sole problem over ring gap due to the fact that the built 3.5 bottom end engines are typically rated to around 700 without a closed deck, I didn’t think the cylinder walls would loose that much structure.
Reason I was questioning hot side is because of the larger turbine for the compressor side I am already running with the upgraded turbos, I was thinking of the possibility of increasing hp per cylinder due to the larger cylinder size, but I suppose if the turbos are already hot side limited larger cylinder size would effectively do nothing until that restriction is gone.
I guess block condition will be the decision maker when I pull the 3.5 out of the Taurus.
Also what’s the formula to determine the 1.6 psi difference
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Ta2dResqr
SHO Member
It is not the correct heads. Simple way to see it, Go to your local convenience store. Grab the largest cup and one size smaller lid (Slurpee lid will aid in the visual). Above the lid is your combustion chamber, below is your cylinder. Notice there is a ring all the way around where the combustion chamber doesn't match the cylinder? Instead of everything being pushed up into a nice hemisphere, it is now hitting a wall all around the edge. This air has to go somewhere. That area on the piston will now see extra forces, the air flow inside the cylinder gets completely changed, and depending on how everything is set up, if any part of your piston goes above deck height, it may now be smashing into a cylinder head.
There are a ton of reasons not to go this route. However, it sounds like you are dead set on doing it.
Not dead set yet just leaning towards giving it a shot the more time goes on, it’s all theory that it won’t work, or won’t work good, or make good power at this point, I just want to understand why it wouldn’t act like a big bore 3.5 ecoboost with all the correct components, or why you wouldn’t want to bore a ecoboost engine,
There are 4.0l+ ecoboosts out there. Just don’t see why this would be any different, if not super expensive why wouldn’t it be a viable way to increase displacement for effectively no extra cost.
Guess I’m just not seeing the problem, there are many ways around compatibility, we’re going as far as welding v bands to exhaust manifolds to support bigger turbos I don’t see why a big bore or stroker sho is a problem,
and for the dome vs cylinder head problem I can clay it out and see where the piston comes the closest and take a burr tool to adjust that clearance accordingly,
also why wouldn’t you want a smaller cylinder head on a engine, that’s been practice for many years to use a smaller chamber, welded chambers are a thing too if anything as long as Compression is calculated, ptv is measured properly and piston to cylinder head clearance is measured, nothing should be worrying, engines have been using wedge style heads for years also those have a flat area specifically designed to increase compression.
I’ll give it a shot I ain’t got nothing to loose, I already dumped a ton of money into this thing as it is and if it doesn’t work I’ll just use the rods in the 3.5 block and have a whole parts engine to use maybe for a 4.0l stroker down the road who knows
luigisho
SHO Member
Theory shmeory. Put it in and push go pedal
I like your style lol
Say you do want to shoot for the moon, and that hypothetically there is no structural shortcoming of the 3.7. Then yes, a 3.7+ could make sense. I can't speak specifically to your turbos, but knowing what I know about the OEMs they were modified from, I am fairly confident that all the bigger bore will do is push your compressors deeper into choke without adding any air flow capability. Absent any indication of a desire to build your own custom turbo setup, there just doesn't exist a sufficient "why" to make a debate about the "why nots" worthwhile. It is fun discussion though.
As for the 1.6 psi, it's just the displacement ratio times manifold pressure (absolute). So, from your 14 psi mustang example: (3.7L/3.5L - 1) * 28.5 psia = 1.63 psi.
