2276 Turbo Efi compression ratio and elevation

[slowsixtyduece]

Hi all. I'm just about ready to assemble the top end but before I do I am wondering if I need to change my compression ratio. My build is a 2276 turbo with SDS EFI. I will have fuel and ignition control.
Specs:
-Engle v-26 on 112 LC
-T3/4b hybrid turbo
-ported 40x37 heads that have a 68cc chamber
-Single 50mm TB, CB end castings
-5.4 rods
-water/ meth injection (no intercooler)
-91 pump gas

I live in Colorado and my elevation is approx 5,500 ft above sea level. It stays pretty cool up here but does get a little warm in the summer months. Car is a weekend driver, 98% street miles, driving up and down mountain passes every once in a while but mostly driving around town and country roads with highway driving too (65 mph).

Planning on around 6-12 lbs of boost once tuned.

Right now I am planning on going with 0 deck with a .060" copper head gasket. According my calculations, with 68cc chambers I will have approx 8.2:1 static CR. Is this too much??
Will I have trouble if I spend some time at sea level with the motor?
Any thoughts are welcomed

[70turbobaja]

Im at 4100 ft in arizona so with the heat my density altitude goes to 6k and I am running 8:1 as well on an 1835 cc. I am running intercooler so let me know how yours behaves please

[slowsixtyduece]

Im at 4100 ft in arizona so with the heat my density altitude goes to 6k and I am running 8:1 as well on an 1835 cc. I am running intercooler so let me know how yours behaves please
Posted: Fri Apr 10, 2015 4:24 am

Sounds like a stout 1835 build. Where exactly are you in AZ? I used to live in Prescott. My old 1915 NA motor usually did okay with 9:1 compression, a t-4 oil cooler conversion and all German tin. Phoenix was a little warmer on it though . I'll keep you posted!

[70turbobaja]

Im down in douglas arizona. Its way down south in arizona. I guess you can call it northern mexico since its a border.lol my baja used to run 9.1 compression but I dropped It when I went turbo so I would worry about pinging

[Steve Arndt]

Sounds just about perfect to me. Maybe run .050 instead of .060 head gaskets.

[Chip Birks]

I agree with Steve. Either one work just fine.

[turbobaja]

Hi all. I'm just about ready to assemble the top end but before I do I am wondering if I need to change my compression ratio. My build is a 2276 turbo with SDS EFI. I will have fuel and ignition control.
Specs:
-Engle v-26 on 112 LC
-T3/4b hybrid turbo
-ported 40x37 heads that have a 68cc chamber
-Single 50mm TB, CB end castings
-5.4 rods
-water/ meth injection (no intercooler)
-91 pump gas

I live in Colorado and my elevation is approx 5,500 ft above sea level. It stays pretty cool up here but does get a little warm in the summer months. Car is a weekend driver, 98% street miles, driving up and down mountain passes every once in a while but mostly driving around town and country roads with highway driving too (65 mph).

Planning on around 6-12 lbs of boost once tuned.

Right now I am planning on going with 0 deck with a .060" copper head gasket. According my calculations, with 68cc chambers I will have approx 8.2:1 static CR. Is this too much??
Will I have trouble if I spend some time at sea level with the motor?
Any thoughts are welcomed

You should be fine, and I'd recommend going with the .050" copper shims also. Pretty sure Mario ran that same cam/CR and displacement over 15psi boost with a water/air charge cooler near sea level so you should be safe at your altitude w/out a charge cooler. Pull some timing out through your torque peak and keep your AFR in a safe area, should be fun.

[MarioVelotta]

You will love the combo!! I was on 114lc with my v-26. The meth with work great for 6-12psi. Any more and an intercooler will be a good idea.

[slowsixtyduece]

Thank you all for the replies! It seems like the consensus is that a .060" copperhead head gasket would be fine, however, a .050" gasket would be even better. I understand that in terms of keeping the combustion in the chamber instead of the cylinder, etc. If that is the case, .050" is going to put me in the vacinity of 8.4:1 static C/R. At that C/R I'm still thinking it's a bit too high for flat top pistons and 6-12 psi. Am I overthinking things?

You will love the combo!! I was on 114lc with my v-26. The meth with work great for 6-12psi. Any more and an intercooler will be a good idea.
Posted: Sat Apr 11, 2015 1:22 am

Mario, I've read about your combo before, and to be honest, I've based much of my build around you and turbobobs combo. Pretty impressive dyno numbers and quarter mile times for street cars. Anyhow, what C/R were you running in the 2276? Also , were your mid 11 sec runs on slicks and with pump or race gas?

Again, thanks to all who replied!

[MarioVelotta]

Mario, I've read about your combo before, and to be honest, I've based much of my build around you and turbobobs combo. Pretty impressive dyno numbers and quarter mile times for street cars. Anyhow, what C/R were you running in the 2276? Also , were your mid 11 sec runs on slicks and with pump or race gas?

I was at 8.1 or 8.2:1 Can't remember right now. I had LOTS of deck and ran copper gaskets. My 11.5's where at 15psi, on slicks and 92 pump and intercooler. I've never even tried race fuel.