Max. c/r on 91 octane?

[ryan_george]

Just wondering:
What is the maximum compression that I should run using 91 octane, and stock chip on a 2.7 stroker?
Thanks in advance.

[Jordan]

how much timing advance is the key...

[ryan_george]

Isn't the timing determined by the ecu?
Sorry for the dumb question, I don't know very much (nothing) about timing! :?

[rs4pro3]

Yes but you can buy an adjustable cam gear and change it yourself, or alter the sensor ont he front of the crank a little

[ryan_george]

Well, assuming that I dont have an adj. gear and haven't moved any sensors.

[Jordan]

9.5:1

[ryan_george]

Well I'm planning on putting early euro eta pistons, and eta crank into the m20b25. And doing this will give me about a 10.1:1 c/r (from what I've been told).
Any suggestions on what to do? Slighty thicker head gasket maybe?
94 octane is the highest I can get, and it's not extremely common. I dont really want to have to resort to octane boosters, etc.

[Fred]

9.5:1

Bingo.

[ryan_george]

Are oversize head gaskets available, and will they be able to lower the compression to the 9.5:1 that you suggest?
I can only seem to find +0.3mm gaskets, and that doesn't seem like a substantial amount.

[AdamF 88iS]

Even 9.5 is a little much as gas gets worse and worse.

[Jon325i]

Even 9.5 is a little much as gas gets worse and worse.

True. Its just owl piss nowadays.

Jon

[ryan_george]

Are oversize head gaskets available, and will they be able to lower the compression to the 9.5:1 that you suggest?
I can only seem to find +0.3mm gaskets, and that doesn't seem like a substantial amount.

^^^^^^

[robmespeedy]

Comp .

Hey Ryan ,
dont listen to me , but My Chevy Camaro is Running 10.5:1 on 91 octane at 36 degrees total advance .

I dont know what it would be for the e30
But on my E30 im going with ROSS pistons 10.0:1

[Screaming_bmwe30]

stock compression is 8.8:1, and with a stock timing/fuel chip you should be able to get away with 10 c/r if you run 93 premium or even 91. I was running 9psi on stock compression, stock ignition, without detonation, and that is like running over 10c/r.

Also, Who here has actually tested fuel to prove that it's any worse than it used to be, haha, it's not, because they have to meet that minimum octane rating to sell the shit.

[ryan_george]

Thanks for the input guys. :D