Gregory347
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GT500’s putting down some good numbers with 9.5:1 on E85 and 93 too.. so why not a coyote?
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Short block…. Compression ratio?
- Thread starter Gregory347
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SolarFlare
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I figured being in a mustang group and Op asking about a coyote build that this is the motor we should be discussing. You want to go “fast” on a modern full weight car with nothing but 93 it better be light, it better be auto and it better have displacement and good head flow.
engineermike
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Right.... anyone who's spent a lot of time logging and tuning a 12/1 gen3 on 93 knows you run into a timing/boost wall. You add timing, you get knock. You drop timing and add boost, you get knock. Sure, you can tweak cam timing, lambda, and GDI settings and squeeze a little more out of it but you're going to find yourself limited to the 700 rwhp range no matter what combination of settings you use. Lower compression, however, and suddenly the wall moves and you can run more timing, boost, or both. On 93 and Gen 3, Brenspeed made 760 rwhp at only 14 psi using the 9.5/1 Aluminator, and PBD made 900 rwhp on a 9.5/1 Predator on 93 at 18 psi. Lowering the compression will get you past that boost/timing wall I mentioned earlier.
That said, if you ask your tuner what compression to run, he'll most likely tell you keep it at 12/1 and have a list of reasons to do so. However, note that at 12/1 he can sell you a tune he's sold a thousand times already, so he makes money for minimal effort and you make decent power. If you drop compression, it will take a lot more tuning time that he just doesn't want to get bogged down with.
engineermike
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I asked the question because when car shopping I wasn't brand or model-loyal. I looked at all the options for making the most power possible when supercharged, ranging from Camaro SS, ZL1, Challenger SRT, Hellcat, etc. I couldn't find a better combination for the buck than a supercharged Coyote Mustang, even on 93. You're answer to my question about how to go fast on 93 was "you don't", so I was wondering what your recommendation was since apparently you think I made a poor choice. It's clearly possible to go fast on pump 93, so what is it about a Coyote Mustang, other than the compression ratio, that makes it such a terrible choice for this goal?
You laid out 2 sets of mutually exclusive requirements. What car meets these requirements?
SolarFlare
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look brother. I’m not here to convince you. And going on about this is just a waste of both of our times. If you or anyone else wants to buy a 40k mustang, spend 15k in mods then potentially build a motor for 10k more and run sewage water fuel in an obviously performance oriented vehicle that’s entirely on Ya’ll. Just because y’all see a sheepy Audi R8, UGR lambo or Calvo viper make 950-1050whp on pump gas doesn’t mean it’s easy OR relevant to a 30k coyote conversation, those guys pay 150k+ for combos like that without price of car. I welcome anyone to actually do it in a mustang. Make 1000whp on pump and run 9.0s or 8s.
base c6, c6Z06, a C6ZR1 and C7Z are all relatively light cars, the ones which aren’t as light are still very aerodynamic and the ones who aren’t auto still have favorable rolling gear ratios for 50-60rolls. Also Vipers.
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engineermike
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Ah, and the truth shall set you free. In post #3 the OP clearly stated “optimize performance with pump” and in your post #7 you said “Ideal in my opinion is stock compression”. But what you meant was, “ideal for e85 or race gas is stock compression”, which doesn’t answer his question.
I’m not trying to convince YOU to try to make power on pump but that’s what the OP asked for so that’s how I answered. E85 isn’t for everyone and you purist racers don’t seem to understand that most people daily their mustangs and don’t want to drive across town every 150 miles to fill up.
It actually is relevant. It costs little extra to optimize for pump gas.
Only 2 seats and the heads don’t compare to coyote heads, so that’s a no-go.
SolarFlare
Well-Known Member
Once again. He should do whatever his tuner and builder is comfortable with. You can drive an 11:1 compression car with boost and 93 anywhere, you want to party? Add octane booster for safety and a little more power. Idk why you continuously want to have these back and forth conversations which prove nothing and you’re saying nothing besides “can be done”. If it only costs “a little more” then why isn’t anyone doing anything with it and more importantly, WHY HAVENT YOU? Any 1/8, 1/4 times? Any 60-130 draggy hits? Anything besides internet promises? No? Ok then.
ice445
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I feel like you're misreading what he's saying. He's not saying you're wrong, just that it doesn't help OP. Making big power on pump gas with stock 12:1 compression is effectively impossible, as you're saying. But it's certainly not impossible if you drop the ratio. There's a reason the OEM's are using 9.5:1 for their boosted motors, like the Predator and the Hellcat 6.2. The dynamics of combustion simply work out better when using boost and lowly pump gas if you knock down the compression ratio.
It's a fact high compression ratios with boost are going to make the MOST power, but that's if you have the fuel to match that.
SolarFlare
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Quoted and underlined from OP's original comment.... "Car will be pump on street and ms109 at track."
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ice445
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Well I guess that makes it easy, just have a 700whp street tune or less and then a whatever it makes tune for the track.
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engineermike
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Also quoted and underlined from OP.... "optimize performance with pump"
You can only optimize for one fuel and he made his intention clear in post #3.
Every one of these discussions goes the same:
OP: What compression ratio should I use with pump gas?
E85 guys: 12/1. Stock is best!
Technical guys: But what about knock?
E85 guys: Well you have to switch to E85. Any idiot knows that.
Technical guys: But he said pump gas.
OP: Lost interest due to the bickering.
You can only optimize for one fuel and he made his intention clear in post #3.
Every one of these discussions goes the same:
OP: What compression ratio should I use with pump gas?
E85 guys: 12/1. Stock is best!
Technical guys: But what about knock?
E85 guys: Well you have to switch to E85. Any idiot knows that.
Technical guys: But he said pump gas.
OP: Lost interest due to the bickering.
SolarFlare
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I’m sure OP will be fine. Whichever way he goes.
Meatball
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You all haven’t gotten too nasty esp for forum arguments, and it’s always interesting to hear a debate on tech stuff that’s appropriate to this forum. I’m sure the OP benefits even if there’s no clear consensus.
but frankly, I haven’t heard a good response to your pointing out that the factory 18 Cobra Jet uses relatively low compression even though there’s zero chance it would be run on low octane fuel (if I have that right) like a street car.
SolarFlare
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It’s not my place to say why Ford chose to go lower compression. They have their reasons. Maybe they chose to go overly concervative being that it’s a flagship racecar thats big money that they don’t want bad feedback on. On the flip side I believe Lunds Whipple gen 3 car went 7s….and compression If I recall correctly is over 12:1
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We knock most of ours down to 11:1 compression…it helps open the window up a lil for tuner error… trying to cram lots of boost with tons of compression (NOT on M1)equals tons of cylinder pressure, the tuner better be good!!
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