8.6, 9, or 9.5 CR for initial NA eventual Turbo build?
08-28-2014, 06:01 PM
#21
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To put it in perspective, the difference on a dyno on a 7.6 liter gasoline v8 between 8.5 and 9.5 compression is about 20ft lbs of torque on a ~500ft lbs engine. If you rationalize that down using napkinscratch guestimating it won't be but about 4.75 ft lbs on a 1.8 liter. But the extra couple of lbs of boost you could run without detonation will be worth far more power than that. YMMV.
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08-28-2014, 06:07 PM
#22
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darn it. 
BTW- my assumption is a tank or two every year. The trip I have in mind is from Chicago to Colorado. In Illinois, Iowa, and Nebraska I have found either 93 octane or e85 everywhere. Colorado has a max of 91 octane with occasional e85. I am just worried what would happen if I was running say, 11:1 and had no choice but to put a partial or full tank of 91 in.
I am half willing to risk it because I am sure I will get good at finding e85 stations around my local area before I go on a trip and have to worry about learning that habit.
BTW- my assumption is a tank or two every year. The trip I have in mind is from Chicago to Colorado. In Illinois, Iowa, and Nebraska I have found either 93 octane or e85 everywhere. Colorado has a max of 91 octane with occasional e85. I am just worried what would happen if I was running say, 11:1 and had no choice but to put a partial or full tank of 91 in.
I am half willing to risk it because I am sure I will get good at finding e85 stations around my local area before I go on a trip and have to worry about learning that habit.
To put it in perspective, the difference on a dyno on a 7.6 liter gasoline v8 between 8.5 and 9.5 compression is about 20ft lbs of torque on a ~500ft lbs engine. If you rationalize that down using napkinscratch guestimating it won't be but about 4.75 ft lbs on a 1.8 liter. But the extra couple of lbs of boost you could run without detonation will be worth far more power than that. YMMV.
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08-28-2014, 06:14 PM
#23
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To put it in perspective, the difference on a dyno on a 7.6 liter gasoline v8 between 8.5 and 9.5 compression is about 20ft lbs of torque on a ~500ft lbs engine. If you rationalize that down using napkinscratch guestimating it won't be but about 4.75 ft lbs on a 1.8 liter. But the extra couple of lbs of boost you could run without detonation will be worth far more power than that. YMMV.
8.6 it is. I just wish we had e85 here.
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08-31-2014, 11:47 PM
#26
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Fyi... My little brother on his jdmAaa stock bp 94 block holds 15psi on e85 self tune for the past year and no issues. Same setup on 91 at 12psi posted 240whp (mustang dyno)with boost dropping to 10psi in the last 500rpm.
There is nothing special about the jdm bp motors then maybe the fact that it has 50k miles or less. But 15psi is holding just fine. This is also his dd miata. 6 days of the week it sees boost constantly.
There is nothing special about the jdm bp motors then maybe the fact that it has 50k miles or less. But 15psi is holding just fine. This is also his dd miata. 6 days of the week it sees boost constantly.
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