Pump gas Comp. Ratio Q's?
 

So I'm officially about to open up the Evo for "surgery". *thumbsup*

However I was wondering if you guys may be able to help me out with a quick question..

Since E85 isn't a reliable option for my area, I'm stuck on 93 Octane. I was eyeballing a set of 8.5:1 Weisco's.

I wanted to see if some more experianced builders would share their Compression Ratios they chose for a 500'ish HP pump gas Evo?

And lastly, would running a low Comp. Ratio for a "Pump Tune" have any affext on HP/TQ numbers if I am able to go with a true Flex Fuel build down the road, should E85 become more available?

Thanks in advance. I appreciate the help.

i really think your missing a big part of the equation. what turbo?

Having a high compressor street motor is nice as it gives you a snappier feel off boost. It can be beneficial when running a large turbo as it helps mitigate the lag. However, having a higher compression motor (10.5:1 +) will also increase your cylinder pressure (obviously). Which can a make it more prone to detonation if your tune is off or you get a bad tank of gas...etc.


I've seen guys run 10:1 on the street, but personally I run 9:1

You have to decide how you want the car to behave. Higher comp: responsive engine but less peak power or lower comp for less low end but potential for higher HP numbers. My honda was 10.8:1, 91 oct + water/meth, and 15psi of boost. Sure, it was only 350whp but it was an INSTANT 350whp. damn, that thing was fun. But, I digress....
Hey, at least you're not stuck with 91. LOL. If i had 93 here, I'd never run e85.

Pump gas Comp. Ratio Q's?
 

Not missing a part of any equation.. I asked about Comp. Ratios for a reason.

I'm curious what others went with on Pump Builds and/or if they had any negative experience if they went Flex.

The turbo on this build is a Gen 2 Twin Scroll 6266 DCBB 1.15 A/R. That's PLENTY enough air to hit 500 on Pump. It's not huge per say, but it will flow well over what I'm shooting for on Pump, and will be plenty enough if I go flex.

The car is built to drive. It's not a purpose built drag build, nor an auto-x build. It'll see more action on the highway than anywhere else. Hitting full boost by 4k isn't important to me with this build, as top end is what will make the difference on the highway, or at the drag strip a couple times a year.

I understand how compression ratios affect performance, I just wanted to hear some experiences from people with similar builds and their Pro's & Con's.

I was leaning towards either 8.5:1 or 9.0:1, with 9.0:1 being the highest I would probably go, due to detonation concerns.

What kind of numbers are you putting down on pump with your current build at 9.0:1?

Check out this thread: https://www.evolutionm.net/forums/ev...omparison.html

A lot of the chatter revolves around alcohol fuels but the gist of the story is to go with as much compression you can without sacrificing boost pressure. The return on investment is better with a low compression/high boost setup vs high compression/low boost.

Out of curiosity, if you are looking for freeway speeds and occasional drag racing, why did you pick an Evo?
There are a ton of cars that do better for less $$

Pump gas Comp. Ratio Q's?
 

Because Evo's have always been one of my favorite platforms. It's AWD so I can cruise up to the local riding spots in the winter, and it's a Sedan, so it's great when the family wants to go for a weekend cruise. Beyond that, the CT9A platform has the ability to perform well, if not surpass most other platforms in many different motorsports.

I can go rip some Freeway pulls on the weekend, I can go to the local 1/4 and Drag, I can go Auto-X, I can go Rally (which I would never do, but still), and I can go Road Race. All while being able to go to the store and grab groceries, cruise with the family, make it to the mountain in the winter and still get decent gas milage.

Each owner may have their own preference as to "what" or "why" this or that car is better for whatever reason, but I don't care about all of that. I love my Evo. And that's why I'm here.

Try to find another platform that can do all of this, while being able to put down serious HP/TQ numbers for under $30k. Most platforms are lucky to be able to do two of those things well, the Evo does ALL of them well.

Besides all of the aforementioned reasons, it's what I want to do. Which is why I'm doing it. :thumbup:

You're definitely entitled to your opinion and I respect your thoughts on the situation.

However, this is not a purpose built, one discipline car. And that's the beauty of it. With everything mentioned above, in my opinion, there's nothing that comes close to an Evo in versatility, with the exception of a Forester and CTS-V Wagon. Both of which I am a fan of, but they don't shine nearly as bright as an Evo does from every angle. :beer:

I agree, I just ask because I see a lot of people going the high HP route which definitely affects it's usefulness in other disciplines.
It's a great all-around vehicle, to to begin with. I agree with that, too. {thumbup}

I'd agree with that! But to each their own. Each build, style of build, or purpose for the build has it's own unique Pro's & Con's.

I'm a big fan of balance myself, and find that the goal of 500-600whp is just about perfect for everything, from late night cruises down I-5 to racing my watch at Pacific International.

Truth be told, I live in an area where there are A LOT of Lamborgini's, Ferarri's and R8's, Ext.. The reasoning behind the "high-ish" numbers is because I see them on the freeway all of the time. There's nothing better than smoking a $250k car, in a little 4 Door box with a "grocery cart spoiler" and being able to add insult to injury by reminding them you only have $50k into it, including the cost of your car. And you can use it year around with your whole family piled into the little pig. Not to mention, I only pay $100.00/Mo for full coverage insurance.

She's the perfect little mobile. It's not a Lambo by any means, but it can "party" just as hard, if not harder than a Lambo with the right build. (So to speak, LOL)

I gotcha. I saw you mention Autox and Rally (which i'd like to do too, but my car isn't built for it LOL). A 500whp Evo (especially on pump gas) wouldn't so well at either.
For having fun around town, freeway, and drag strip, I think you are definitely on the right track. I have a friend who has the same goals as you and he's very happy with his GT35r. When he drove my car, he said, "The power comes on too soon. I like how mine drives". It's definitely all about personal preference. I also think "all-around performance" is an objective term.
And +1 on surprising exotics. I once ran an autox course that was basically a small road course (kart track with speeds into 4th gear). I had FTD and beat a guy in an F430 who was not happy LOL. The guy that builds my oil pans has a Gallardo and GTR in his shop from time to time. I beat those guys at our road race events... it doesn't make them too happy LOL. not bad for <400whp.

That's what I'm saying! LOL!

Well done sir! Well done!

If you want to be able to run good boost and timing for good power with pump gas, keep the compression ratio at 9:1. No need to to lower it to 8.5 though. Stock is 8.8, and 9 is a small bump up and works well. Wiseco offers it with the 1400hd's..