Pistons - Please

[BlueCollarDaily]

They were all very close and balanced out easily. For me e85 is easily available and it’s not my daily so it was a no brainer. With modern intercooler higher compression is not as much as an issue as it was in the past. I run a procharger D1x stage 2 and with the base 4.88 pulley on a stock engine made over 800 to the wheels. Now with a 3.90 pulley I made 1050 but am planning on going up slightly with some larger injectors and an upgraded intercooler.

Very nice I'm EB stage 2 minus .5 on my 19 but all my other cars have been procharger...have a F1A-94 on my 67 Camaro and love it....never been an issue one with it....
Did you ever run the D1x on 93? If so what did you get....a D1x stage 2 is exactly what I was going to buy( have a guy literally spent double on the EB with both stages not counting failures) , went with Edelbrock for the warranty but 3 engines later and no warranty backing down boost to stage 1 level and a custom tune....yea I'm wishing I'd just put 5k to the side bahaha. Since I could install it myself ( not needing ASE for warranty) it would be off carfax and money left over could have funded a built short block.....
800whp with a 4.88 damn...what is that 11-12psi?

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[BlueCollarDaily]

I'd rather run more compression. Conventional methods yield conventional results....

I understand the thought process it's just that I dont race much if the car can even stay together long enough we talking maybe 3-4 test n tunes then watch big boys run while I'm there...but snappy 1/3rd throttle performance of that D1 and 12 to 1 I use that everytime its started, does that make sense ?

 

[80FoxCoupe]

I understand the thought process it's just that I dont race much if the car can even stay together long enough we talking maybe 3-4 test n tunes then watch big boys run while I'm there...but snappy 1/3rd throttle performance of that D1 and 12 to 1 I use that everytime its started, does that make sense ?

Absolutely. One thing to remember is that most get all caught up on static compression. They forget that we have adjustable cam timing via tuning. Which means that dynamic compression can be bled off to a degree. Also 18up direct injection cools cylinder temps to some extent. With that being said, why go below 12:1? To each their own.

 

[BlueCollarDaily]

Absolutely. One thing to remember is that most get all caught up on static compression. They forget that we have adjustable cam timing via tuning. Which means that dynamic compression can be bled off to a degree. Also 18up direct injection cools cylinder temps to some extent. With that being said, why go below 12:1? To each their own.

I was literally I mean literally sitting here thinking about that, being new to the platform and the ability to adjust intake and exhaust cams independently vs load/rpm in real time SHIT...we often used cans to put dynamic compression where we needed it and protect the engine my previous 30 years building, tuning, and racing GM....

I was literally sitting here thinking cant we just bleed some cylinder pressure off in key areas of a pull? Also the DI is nuts impressive get this shit my first engine went from 220-230psi ( fyi both new long blocks only test at 175-190 on same gauge same everything including tune, hmmmmm) to 90s psi in 3 cylinders and 120psi in a 4th total gone pumping oil whole nine. THAT engine in that shape barely idling once above 2300rpm to say 3200 the DI would literally BLOW the oil of half the spark plug and it get this shit, would clean up and misfire counter would stop....it would even pull to redline smoothly as pie and I drove it 15 miles to installer using the paddles to keep it in that range and you couldnt even tell it was blown...the second the DI blend lowered it would crazy misfire hehe.......the DI is impressive tech.....

 

[engineermike]

Lower compression and more boost will allow more torque and power at any given octane. Examples are plentiful. No OEM that I can find has supplied 12/1 compression and boost. The highest compression I could find on a factory boosted engine is 11/1 and there is a reason for that.

Take these examples of workaday engines and their performance variants:
- BMW B58 is 11/1 compression and makes 369 ftlb. Performance version S58 is 9.3/1 and makes 443 ftlb.
- Ford 3.5eb is 10.5/1 and makes 470 ftlb. In the raptor it’s 10.0/1 and makes 510 ftlb. In the GT it’s 9.0/1 and makes 550 ftlb.
- Honda 1.5 turbo is 10.6/1 and makes 162 ftlb. The SI version is 10.3/1 and makes 192 ftlb.

Altering valve timing to reduce cylinder pressure is self-defeating. Bleeding off pressure out the intake valve is reducing effective displacement and will never make as much torque and power as lowering the compression ratio, both allowing more boost.

I’ve don’t quite a bit of benchmarking work comparing all sorts of engines bmep vs compression ratio, pre-spark cylinder pressure and temperature, and post-spark pressure and temperature. Supercharged gen3 coyotes are off the charts.

 

[80FoxCoupe]

Lower compression and more boost will allow more torque and power at any given octane. Examples are plentiful. No OEM that I can find has supplied 12/1 compression and boost. The highest compression I could find on a factory boosted engine is 11/1 and there is a reason for that.

Take these examples of workaday engines and their performance variants:
- BMW B58 is 11/1 compression and makes 369 ftlb. Performance version S58 is 9.3/1 and makes 443 ftlb.
- Ford 3.5eb is 10.5/1 and makes 470 ftlb. In the raptor it’s 10.0/1 and makes 510 ftlb. In the GT it’s 9.0/1 and makes 550 ftlb.
- Honda 1.5 turbo is 10.6/1 and makes 162 ftlb. The SI version is 10.3/1 and makes 192 ftlb.

Altering valve timing to reduce cylinder pressure is self-defeating. Bleeding off pressure out the intake valve is reducing effective displacement and will never make as much torque and power as lowering the compression ratio, both allowing more boost.

I’ve don’t quite a bit of benchmarking work comparing all sorts of engines bmep vs compression ratio, pre-spark cylinder pressure and temperature, and post-spark pressure and temperature. Supercharged gen3 coyotes are off the charts.

Well there it is. Looks like low compression is the best option. See you guys in my rear view mirror!

 

[Woopaloop]

Lower compression and more boost will allow more torque and power at any given octane. Examples are plentiful. No OEM that I can find has supplied 12/1 compression and boost. The highest compression I could find on a factory boosted engine is 11/1 and there is a reason for that.

Take these examples of workaday engines and their performance variants:
- BMW B58 is 11/1 compression and makes 369 ftlb. Performance version S58 is 9.3/1 and makes 443 ftlb.
- Ford 3.5eb is 10.5/1 and makes 470 ftlb. In the raptor it’s 10.0/1 and makes 510 ftlb. In the GT it’s 9.0/1 and makes 550 ftlb.
- Honda 1.5 turbo is 10.6/1 and makes 162 ftlb. The SI version is 10.3/1 and makes 192 ftlb.

Altering valve timing to reduce cylinder pressure is self-defeating. Bleeding off pressure out the intake valve is reducing effective displacement and will never make as much torque and power as lowering the compression ratio, both allowing more boost.

I’ve don’t quite a bit of benchmarking work comparing all sorts of engines bmep vs compression ratio, pre-spark cylinder pressure and temperature, and post-spark pressure and temperature. Supercharged gen3 coyotes are off the charts.

The main reason they leave the CR that low is because they dont want a case of bad gas or user error (putting 87 or 85) in the motor to blow it. Higher compression motors will net more power per lb of boost but have less detonation resistance. If you plan to run e85 (good quality) or have a reliable meth setup I don't really think it's neccessary to lower the compression at boost levels around 1 bar.

 

[Avispa]

That and Ford set the compression in the 2020 GT 500 @ 9.5. The old Terminator was 8.8 and it was hard to blow up one of those if you paid any attention to the tune and fuel. 12:1 sounds scary.

 

[80FoxCoupe]

That and Ford set the compression in the 2020 GT 500 @ 9.5. The old Terminator was 8.8 and it was hard to blow up one of those if you paid any attention to the tune and fuel. 12:1 sounds scary.

Don't be scared!

 

[engineermike]

Well there it is. Looks like low compression is the best option. See you guys in my rear view mirror!

Looks like you left out the part about more boost.

 

[engineermike]

.... If you plan to run e85 (good quality) or have a reliable meth setup I don't really think it's neccessary to lower the compression at boost levels around 1 bar.

To the OP @schmeky, @BlueCollarDaily, and many others e85 is not an option.

12/1 and 10 psi on 93 can work surprisingly well as long as nothing else ever goes wrong. One bad tank of gas, a tune error, a bad fuel pump, or a clogged car and it’s game over. This is precisely the reason you don’t see any oem running 12/1 with boost.

 

[BlueCollarDaily]

Lower compression and more boost will allow more torque and power at any given octane. Examples are plentiful. No OEM that I can find has supplied 12/1 compression and boost. The highest compression I could find on a factory boosted engine is 11/1 and there is a reason for that.

Take these examples of workaday engines and their performance variants:
- BMW B58 is 11/1 compression and makes 369 ftlb. Performance version S58 is 9.3/1 and makes 443 ftlb.
- Ford 3.5eb is 10.5/1 and makes 470 ftlb. In the raptor it’s 10.0/1 and makes 510 ftlb. In the GT it’s 9.0/1 and makes 550 ftlb.
- Honda 1.5 turbo is 10.6/1 and makes 162 ftlb. The SI version is 10.3/1 and makes 192 ftlb.

Altering valve timing to reduce cylinder pressure is self-defeating. Bleeding off pressure out the intake valve is reducing effective displacement and will never make as much torque and power as lowering the compression ratio, both allowing more boost.

I’ve don’t quite a bit of benchmarking work comparing all sorts of engines bmep vs compression ratio, pre-spark cylinder pressure and temperature, and post-spark pressure and temperature. Supercharged gen3 coyotes are off the charts.

Are you talking at WOT or 20% throttle? Because as I stated I would prefer the balance to compression to boost pressure to be skewed toward NON boost operation of which the average street vehicle lives 99% of it's like, while it would be also desirable to live that other 1 percent...lol...
I can't imagine how many variables there truly are but turbulence, complete combustion, overall volumetric efficiency, intercooling and heat exchanger btu capacities, techniques such as DI affect on combustion ( we were astounded how far lean the AFR shifted lean to max torque on GM apps), thermal conduction of the block and radiator ect ect ect....
Personally I've built engines as low as 8 to 1 for boost and high as 11....I prefer that 10ish range because that 8 to 1 engine was terrible unti boost comes on....

I'm not bullish on 12 to 1 for sure scares me to be honest, but I've felt this car stock and it has horrific torque and nimbleness already at part throttle....very lazy...I certainly wouldnt want to lower it to 9.5 to 1....there has to he an area where just the heat generated from compressing a gas( boost) beyond atmospheric overwhelms your intercooler and heat exchangers, as they are in car and purchased already, ability to control that heat and you pull timing IAT vs cylinder pressure. That has to have a curve and while I'm certain regardless of some of the effects of DI and high compression that's below 12 to 1, its probably higher than 9 to 1 on this engine and as I said I'm not willing to give up ANY off boost power to gain on boost power as it's already anemic....

More stroke of CI and sure start lowering it opening up tuning window for me personally they are getting 730whp put of 93 with the system as is now...if I had to lower that ( and I would if I could fit a larger pulley ) to open tuning window for 93 ( it has to be meeting the tuning window now as it's an awfully sensitive engine it would show up as positive knock; the sensors have not been desensitized) I would lower boost for less power at WOT but I want ZERO part of less torque everywhere but WOT ( and boost) by lowering compression....fuel efficiency either...in your testing how did BSFC fare low to high?

I dont dispute at all to a certain degree ( and there has to he a cross over of heat generated and belt slippage and all the things associated with running higher boost levels on the same sized blower aka rotors and bearings and thermal generation ect ect ect ) lower static compression and higher boost yields better results and a wider tuning window in an octane limited application .....its just I'm for real street and I'd never want to give to much of the 99% operational status of my engine ( off boost), for more tuning window, max torque and max power on.....but my goal isnt max effort ET on 93 it's a well balanced car....
That said yes on the chart 12 to 1 is off it haha...and since I'm broke now UNLESS I can get a no rebalance piston combo, I'd definitely split the middle and drop to 11 to 1 and maybe go down a gear ratio....primarily because a 11 to 1 option is also a shelf piston I can get....
Admittedly I dont know the tricks in coyote world to drop a half point or so like cheapo LS9 MLS gaskets and a head common $100 head swap on LS....or having the combustion chambers ported and bowl blending which takes them from 118cc to 122cc most of the time....then running a .053 gasket with slightly above zero deck for quench....I just simply cannot manipulate existing coyote components with any thrifty and economical manner to stay in the efficiency range while not breaking the bank.....to new.....
However 11 to 1 shelf pistons exist in the unit I've chosen after your reminders I'll certainly lean towards them especially if the crank has to be rebalance ( I was hoping to get a combo 2-3grams off from stock and run it ).

Always nice to learn or relearn things, I thought it insane myself to boost 12 to 1 with cast pistons...who cant handle the slightest bit of detonation....BUT if that load out gets me say 700whp and drives like I want, hey I'm really just fine with that but it I can drop a point and even go to 3.31s squeezing now a solid 750whp out of that....be fine too....I just cant take this car being as lazy as it was stock ( I get into low boost a lot it's why I like my 2650) it was horrible...wouldnt spin a 255 tire with TC off trying, so taking 6 or 7% off of it no thanks I've drove 8 to 1 dogs before....interesting for you observations my current BBC runs at 9.7 to 1 over 1000hp no intercooler and pump gas....hehe...but when base engine is 700hp dont need much additive hehe.....
Always enjoy your post Engineer Mike

 

[BlueCollarDaily]

Actually I enjoy about all the post here, I'm still new to the platform and I'm soaking info like a sponge....and old dry as hell sponge but I can still take on a little water ;)

 

[80FoxCoupe]

Looks like you left out the part about more boost.

Again, see y'all in the rear view.

 

[Avispa]

Fox, I'm not scared. I'm sticking with a stock long block for now...lol

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