VVL head conversion Comp ratios

[badmotorfingaz]

Hi all,

Interested in what compression ratio most of you are going for when carrying out a full rebuild, I see most companies like CP and JE etc can supply an of the shelf 9.0:1, anyone reverting back to 8.5:1 or goin the other way like a 9.5:1, I realise fuel type, boost etc play a part in what's suited, so if you picked a 9.:1 what were your reasons etc.

Thanks in Advance

[jr_ss]

9, 10 and I believe higher 11, are available. 10:1 you'll need to run E85 or Meth injection.

A VE head on an 8.5:1 SR20DET bottomend yields about 9.5:1. However, very limited choices with valve reliefs

[Tom N]

9:1 for pump gas and 11:1 for race gas, E85 or meth injection.

[hanzbrady]

Compression ratios depend heavily on application and use, not just fuel and other physical components of the build. The lower the compression ratio on a boosted motor means the less response your motor will have out of boost, however; with this you can run more boost and have a wider easier window to tune in and make power. 8:5:1 is great on high horsepower motors that are always being driven in their powerband with lots of boost. Now 9:0:1 is where you get a compromise of off boost reliability and drive-ability vs potential power output in racing or hard driving situations, all in all this is better for a more "mild" street/strip car. The super high compressions such as 11:1 are race only boosted builds with insane fuel set-ups or are for NA builds.

[SoundEfx]

I wouldn't want to be a tuner trying to boost a 11:1 or more compression ration.

[Tom N]

I wouldn't want to be a tuner trying to boost a 11:1 or more compression ration.



Nothing hard about it if you're not an idiot.

[hanzbrady]

I wouldn't want to be a tuner trying to boost a 11:1 or more compression ration.

I've personally only seen it work on one of my friends cars, it's a promod Volkswagen beetle running on alcohol tuned with a stand alone MSD system. There's some video of it in my build thread.

[Tom N]

Boosted high compression motors are rather common these days. Especially with the availability of E85. I built my first one in 2004 and had to order custom high compression pistons thru Marco of Magnus Motorsports. Now 10:1 and 11:1 Pistons are common off-the-shelf pistons. Anyone who says they haven't seen them used isn't around fast cars very much...

[hanzbrady]

Boosted high compression motors are rather common these days. Especially with the availability of E85. I built my first one in 2004 and had to order custom high compression pistons thru Marco of Magnus Motorsports. Now 10:1 and 11:1 Pistons are common off-the-shelf pistons. Anyone who says they haven't seen them used isn't around fast cars very much...

I'm surprised you find E85 common in florida, I rarley get to see it because no one wants to run it due to our horrible humidity. I agree though, today's fuels are revolutionizing engine building.

[Tom N]

I'm surprised you find E85 common in florida, I rarley get to see it because no one wants to run it due to our horrible humidity. I agree though, today's fuels are revolutionizing engine building.


Its becoming more common in my area of Florida which is the Bay Area.

[jr_ss]

As soon as they put an E85 station in Venice I'm making the switch... Took temping to not make 600whp all day every day.

[Tom N]

As soon as they put an E85 station in Venice I'm making the switch... Took temping to not make 600whp all day every day.

There's one right off I 75 on bee ridge. Not a 20 minute drive from us.
And it's always on the way to the track or Tampa :2f2f:

[jr_ss]

There's one right off I 75 on bee ridge. Not a 20 minute drive from us.
And it's always on the way to the track or Tampa :2f2f:

That's not a big deal for someone that travels all over the place daily. That's completely out of the way for me. Having a station in Venice will give me much more incentive. Soon though, it's only a matter of time. I'm hoping the new WAWA they are building at 776/41 will have it.

[Kingtal0n]

I'd run it with a flex sensor so I can use 93 and Eanything in any combination at any time.

[Tom N]

That's not a big deal for someone that travels all over the place daily. That's completely out of the way for me. Having a station in Venice will give me much more incentive. Soon though, it's only a matter of time. I'm hoping the new WAWA they are building at 776/41 will have it.



None of the Wawa's they are putting in around here have it. Only gas stations i see getting it are Thorton's and racetrack

[Tom N]

I'd run it with a flex sensor so I can use 93 and Eanything in any combination at any time.



I have my Talon set up on flex fuel. It's the best thing ever for a street driven race car. I will get the Nissan set up on flex fuel one of these days. For now it's just pump gas with methanol injection