I have been reading a lot and still don't fully understand what would be better for my build seems like half say 9:1 and the other half 10:1.
2.3 stroker
Gsc s2 cams and springs
Bb fp red
Supporting fuel system exhaust all that
Ported intake and tb
I can't get e85 very close to home though I can get it.
I would like to have a map switch.
My car will be a dd and weekend drag car sometimes
Should I go 10:1 or stay 9:1?
I'll probably take the car to evo dynamics because they seem reputable and somewhat close.
I'm in Knoxville ar 72845.
They said I should stay at 9:1 and I'm not opposed to taking it somewhere else if someone knows of a better place within about 10 hours from me. Thanks in advance.
I have done a ton of reading and searching by the way. Just still unsure.

 

I believe it was Buschur who said that there was no difference in drivability between a 9.0:1 or a 10.5:1, which he proved with his RS multiple times. I would go with the 10:1 if you're going to use E85 at some point. I've had low and high compression pistons on my engine and for some reason, I prefer the high compression, even on pump gas.

 

If you're going to run 91/93 consistently I would just run 9:1. Pump Gas on 10:1 doesn't seem very fun.

 

I have a 10:1 on 93 oct. Very fun indeed

 

OP, its your build and you have a recommendation from your builder--- Now, what do you see as the perceived benefits for a 10:1 motor. I ask this because if you cant think of at least 2 things immediately off the top of your head then stick with what EVO-D recommended. Your looking those guys in the eyes and they are backing the build. Nothing against the forum here, but your not working with them and their opinion provides no vested interest in the result. Again , go with the recommendation of the builder, if you have questions run it by them for their view since there is a big difference between arm chair racing and function. Good Luck.

 

I am the builder they are the tuner. What's to say they just haven't done any/many 10:1. I do all my own work except tuning. More compression makes it better to drive off boost or the effect that it drives better off boost. These are questions I want more information on. Buschur swears by it. A lot of people say it's great some say it doesn't. I want more direct information.
More info faisalm

 

That was just a place not too awfully far to drive. No specific reason why I chose them.

 

I guess it's just cause I'm stuck with this fish **** 91 oct we have here in California.
I went 10.5:1 on my build running a fp black. Plan on just running E85, 91 in case of an emergency. Lol

 

if you are planning on e85 or race gas 10:1 will be fine.. on 91/93 i would be much more worried about durability.

 

Ok let's try pros and cons. Opinions of people who have ran both comp ratios.

 

If you search you will find a thread that Aaron "JohnBradley" posted in. He states the pros and cons about compression, especially when tuning. It is a very good read especially if you do not understand how CR and ignition timing are related. For the record I chose 9.5:1 on my slr 2.2l and my motor will see 93 and e85.

 

Mitsubishi had gone up to 9:1 on a previous version of the EVO and went back to 8.8:1. For a pump gas car I would stay with stock compression or lower. Stock 1G DSM is 7.8:1 and they can make a lot of power on pump with boost. I have 10.5:1 because I run E85 almost exclusively.

 

I run 10.5:1 and my car runs on 93 most of the time

 

I had 10.6:1 running pump and e85. Switched it to 10:1 for more pump since its not available in canada.

 

The knock threshhold with higher compression and pumpgas doesnt math out. 1 full point of compression according the old hot rod rule is around 4% more power and this holds true in our engines as well. So if you have a 9:1 motor that makes 600whp it theoretically will make 624 with compression. It feels no different down low, doesnt affect transient response, and really makes life more difficult on pumpgas.

Here is why-

92 octane WA/OR and some Midwest 91 octane are limited to 28psi give or take on a 9:1 motor. On a 10:1 motor that threshold drops to 20-21psi and then its all about the combination in order to run that. I have used det-cans, I can read plugs, I have tuned cars with stock knock control settings and watched voltage vs counts, I am not giving aberrant data.

Here is a 9:1 LR2.4 with a 3586 at 19psi, 25psi, and 28psi -



Giving the 19.25psi the benefit of the doubt and say it made 5% more power with a 10:1 motor but was limited to that boost, would 545whp (519x1.05) be as much fun as running 28psi?