Block and CR choice for high elevation... on 91 usually, sometimes E85, flexfuel
Nov 23, 2018, 01:52 AM
#1
Block and CR choice for high elevation... on 91 usually, sometimes E85, flexfuel
Is there life after E85... and at high elevation?
I will preface this post by saying I am familiar with the pros and cons of the various 4g63/4G64 block configurations in regards to RPM, piston speed, rod angle, side loading, etc. but not in relation to large fluctuations in elevation, fuel and compression ratio. I have searched for information on and beyond this forum and still don't have a clear idea of what to do.
I have an VIII with 9x,000 mile stock block, stock 9.8cm turbo, Kelford 272, all the usual E85 supporting mods to maximize this setup, that I ran 30psi on E85 almost exclusively when I lived at sea level and E85 stations were abundant near me. I LOVED this setup and was very happy with the response, fast spool and low end torque, and it made a decent 340/340 on FFTECs Mustang dyno. Most of my driving is mountain roads and highways, I used to autocross and would like to again, and begin tracking the car again. Not much interest in drag type driving and big turbos that spool much slower than my current setup.
Now I live and will drive the car at 6,000' elevation most of the time, only occasionally going down to sea level, and there are no E85 stations within 2 hours of me anymore, not until I get back down to sea level basically. I will use full flex fuel on stock ECU to make the best of this, and haul E85 back up the mountain as often as possible. When I did run the car on the 91 tune at 6000', it was obvious I was forever spoiled by E85 and sea level, and want some of that performance back, but losing low end and slower spool do not appeal to me just to get certain torque and power numbers, later at a higher RPM. But no E85 80% of the time.... so how to proceed?
Fast forward a few years and the car was wrecked, so the engine will be swapped to a new shell. At this point, while the engine is out I am considering building the block, probably to make the most of a 71HTA or Green size turbo (and future proofing it, making it more reliable at these power levels), at least for now. 400wtq/400whp, up to 450/450 is probably the most I will want and be able to use. but I want it all early and low in the RPM range, to be flogged hard reliably with big sticky tires, around a track, hence considering a built block in addition to built transmission and tcase.
At this point I am having a hard time deciding which block would best suit my needs now, and what compression ratio, and because without E85, I will need a bigger turbo to produce similar power. Obviously high elevation means less air density, so larger displacement like 2.3 would help a larger turbo produce more torque at lower boost, spool a bigger turbo faster, but I am hesitant to give up RPM which would require me to shift more often autocrossing or on track, or ever.
I want my high elevation, low end torque, flex fuel, don't have to upshift cake and to eat it too. What displacement and compression ratio would be the best for my goals?
I will preface this post by saying I am familiar with the pros and cons of the various 4g63/4G64 block configurations in regards to RPM, piston speed, rod angle, side loading, etc. but not in relation to large fluctuations in elevation, fuel and compression ratio. I have searched for information on and beyond this forum and still don't have a clear idea of what to do.
I have an VIII with 9x,000 mile stock block, stock 9.8cm turbo, Kelford 272, all the usual E85 supporting mods to maximize this setup, that I ran 30psi on E85 almost exclusively when I lived at sea level and E85 stations were abundant near me. I LOVED this setup and was very happy with the response, fast spool and low end torque, and it made a decent 340/340 on FFTECs Mustang dyno. Most of my driving is mountain roads and highways, I used to autocross and would like to again, and begin tracking the car again. Not much interest in drag type driving and big turbos that spool much slower than my current setup.
Now I live and will drive the car at 6,000' elevation most of the time, only occasionally going down to sea level, and there are no E85 stations within 2 hours of me anymore, not until I get back down to sea level basically. I will use full flex fuel on stock ECU to make the best of this, and haul E85 back up the mountain as often as possible. When I did run the car on the 91 tune at 6000', it was obvious I was forever spoiled by E85 and sea level, and want some of that performance back, but losing low end and slower spool do not appeal to me just to get certain torque and power numbers, later at a higher RPM. But no E85 80% of the time.... so how to proceed?
Fast forward a few years and the car was wrecked, so the engine will be swapped to a new shell. At this point, while the engine is out I am considering building the block, probably to make the most of a 71HTA or Green size turbo (and future proofing it, making it more reliable at these power levels), at least for now. 400wtq/400whp, up to 450/450 is probably the most I will want and be able to use. but I want it all early and low in the RPM range, to be flogged hard reliably with big sticky tires, around a track, hence considering a built block in addition to built transmission and tcase.
At this point I am having a hard time deciding which block would best suit my needs now, and what compression ratio, and because without E85, I will need a bigger turbo to produce similar power. Obviously high elevation means less air density, so larger displacement like 2.3 would help a larger turbo produce more torque at lower boost, spool a bigger turbo faster, but I am hesitant to give up RPM which would require me to shift more often autocrossing or on track, or ever.
I want my high elevation, low end torque, flex fuel, don't have to upshift cake and to eat it too. What displacement and compression ratio would be the best for my goals?
Last edited by hokiruu; Nov 23, 2018 at 02:10 AM.
