DOHC Turbo compression ratios

[vr4ced]

What compression ratios do you guys use in your twin cam setups?

Also how much boost are you pushing?

Looking at my options I'm thinking of using 9.0:1. Its higher than what I would have traditionally used.

[Lummy]

All the old rules for compression ratios are out the window now with E85 being redily available.

Look into it, you wont be disappointed.

I run 9:1 on my DOHC 4G63 with 18psi of boost. Makes 360HP atw on a very conservative tune. If I were to do a rebuild, subject to availability, I would up the CR.

[1320ft]

E85 & 12:1 = Happy in the pants!

[vr4ced]

All the old rules for compression ratios are out the window now with E85 being redily available.

Look into it, you wont be disappointed.

I run 9:1 on my DOHC 4G63 with 18psi of boost. Makes 360HP atw on a very conservative tune. If I were to do a rebuild, subject to availability, I would up the CR.

Cool. Is this in the race scorpion? Are you using a stroker? What cams?

I have trouble finding E85 in my local area. What servos do you get it from?

[thrash]

E85 & 12:1 = Happy in the pants!

really??

[Lummy]

I certainly wouldn't suggest 12:1 as a good idea, although it wouldn't be impossible with a well built engine, low boost and an excellent tune.

Yes, it's in the race Scorpion. Stroker 4G63, cams are 264/264

Where are you located? I'm seeing E85 available at more and more places these days - I use pump E85 from United. If you look on forums, you'll hear some people talking about inconsistencies with pump E85. I haven't seen any evidence of this - you can buy test kits to check the ethanol level and you can do a visual check (it should be virtually clear, just with a slight purple tinge - if it's absorbed a lot of moisture, it will be cloudy).

I have nothing but praise for E85. You just need to make sure your fuel system is up to the challenge of delivering up to 25% more than before as at WOT, you do use quite a bit more than ULP.

[1320ft]

I certainly wouldn't suggest 12:1 as a good idea, although it wouldn't be impossible with a well built engine, low boost and an excellent tune.

Really,

We did a 2jz not long ago with 12.5:1 running 40psi and not an issue.

Makes a lazy 1300h/p

[thrash]

alas, the question becomes.. was that a reliable daily driver or did it only ever see <9 seconds of use every now and again?

[niss720]

Most of the liberty's, uniteds and mogas servo's have e85 in SA, u will need to get it tune by someone who knows e85 tho! I'd recommend steve knight if you I that way. I have personally used 9:5 on my ca18 and it's great, little lag and high power with low boost, but as with everything its all about the tune

[fugazi]

12:1 is not the problem... the problem is the tuner!