Good Compression Ratio for 1k Build on e85?
02-14-2018, 06:08 PM
#1
Instructor
Thread Starter
Good Compression Ratio for 1k Build on e85?
I'm in the process of spec'ing parts for my build and need insight on compression ratio.
The car will rarely see a dragstrip but plenty of highway pulls and light street driving. What is a good compression ratio for 900-1k whp on e85 for a 427? From past projects 10.5:1 seems like a good balance, but want to hear from those who've run or tuned cars at that level. Any CR will work, but there is a point of diminishing returns and a razor thin tuning window (not interested in being here). A fat powerband is more important to me than some peak number from 6800-7000 rpms.
Thanks,
-GK
- Forged 427
- e85 (no meth)
- Likely 2200R/YSi (could go one step smaller if it feels too lazy)
The car will rarely see a dragstrip but plenty of highway pulls and light street driving. What is a good compression ratio for 900-1k whp on e85 for a 427? From past projects 10.5:1 seems like a good balance, but want to hear from those who've run or tuned cars at that level. Any CR will work, but there is a point of diminishing returns and a razor thin tuning window (not interested in being here). A fat powerband is more important to me than some peak number from 6800-7000 rpms.
Thanks,
-GK
Last edited by Ghost Knight; 02-14-2018 at 06:44 PM.
02-14-2018, 06:55 PM
#2
11:1 is what I would aim for.
02-14-2018, 10:02 PM
#3
Team Owner
e85 only or want to run pump too?
Flex fuel 10.2-10.5
E85+ only, 11+
Flex fuel 10.2-10.5
E85+ only, 11+
02-15-2018, 10:45 AM
#5
Instructor
Thread Starter
e85 only, I'll run pump 93 if I need to limp to the next e85 pump (no WOT, low rpm).
I had meth on past cars and don't want to run it again. Full e85 is better IMO, less points of failure.
I had meth on past cars and don't want to run it again. Full e85 is better IMO, less points of failure.
02-15-2018, 01:44 PM
#6
Team Owner
I would also run meth. Easy power and gains.
02-15-2018, 03:13 PM
#7
Safety Car
E85 and meth here and the combo is great. I’d run a minimum of 11.1:1
02-21-2018, 03:37 PM
#10
Safety Car
Stock here 
03-02-2018, 11:59 PM
#11
Melting Slicks
10:1 is flex fuel territory. Depends how much gasoline you actually want to use. get stuck somewhere with only 87? You want to be able to drive the car in the worst case scenario: 10:1 with a cam should be fine as long as it stays cool and you drive easy on 87, even at sea level.
This is true as long as the class is unlimited with respect to fuel use. If there were a fuel quantity restriction or some other economy related feature in a race, more compression might outweigh the increase in power that lowering it might have offered.
Interesting problem we face: increasing compression offers both increased power, and decreased power, depending on the perspective.
Luckily the answer is simple as in the quoted passage, he is saying power comes first when fuel use is unrestricted, so we lower compression until it is safe enough to make that much power given the airflow and RPM required to make it. Clarifying what the quoted means for readers ;D
Interesting problem we face: increasing compression offers both increased power, and decreased power, depending on the perspective.
Luckily the answer is simple as in the quoted passage, he is saying power comes first when fuel use is unrestricted, so we lower compression until it is safe enough to make that much power given the airflow and RPM required to make it. Clarifying what the quoted means for readers ;D
Last edited by Kingtal0n; 03-12-2018 at 12:19 PM. Reason: clarifying the below quoted passage for readers
