Pump Gas - Octane Rating and Compression Ratio

[Mgardiner1]

9+ DCR at sea level would most likely not run on 93 without pinging, even having only .043 quench.

go with the 21cc dished pistons.

[PolloLoco]

9+ DCR at sea level would most likely not run on 93 without pinging, even having only .043 quench.

go with the 21cc dished pistons.

Damn, that's what I was afraid of.

[PolloLoco]

9+ DCR at sea level would most likely not run on 93 without pinging, even having only .043 quench.

go with the 21cc dished pistons.

What about E85? I've spent a little time today doing research. Very limited discussion about it on this forum, and it's quite dated, but FrankZ would be the subject matter expert here and he's had a bad experience. Hopefully I can build on his discoveries and be better prepared. Still have more research to do...

[Mgardiner1]

i think i would shoot for a DCR of 8.5 or lower...... i'm not a fuel expert, but i have a hard time believing that excellent quench can make up the difference of extreme compression ratio's

[crustodd]

Hey guys,
My stoker is a 4.7. I did the long rod version. I used the KB's with the 21.73 dish and the block was zero decked. The head was milled down A LOT to get to the 58cc chambers. If I remember correctly the static comp was around 9.68:1 and the dynamic was around 8.5:1. Might a' been a tiny bit +/- that. I'm using the Lunati 63501 cam. I worked at length with the machinist to get the quench around .040-.045. I run premium that's available here in Oregon from Union 76 stations. I am getting some LIGHT pinging around 3000-4000 under 3/4 to WOT. If I add some Sunoco 110 octane, will this likely cure it? If it did, does that mean it's NOT a lean condition? It's VERY strong, accept for a few gremlins (sensors, etc...) I've gone to plugs that are two steps cooler, and the ping persists. It seems like it doesn't run quite as strong either. Maybe, maybe not. I will also relocate the IAT to the air cleaner.

Todd

[Mgardiner1]

If I add some Sunoco 110 octane, will this likely cure it?

Not trying to be an ass, but please try not to hijack other peoples threads. You have enough of your own threads going on relating to your pnging issues.

As outlined, a DCR or 8.5 or high MAY or MAY NOT run on regular pump gas (87-93 octane), dependent on quench. The only octane i can vouch for with 8.25 DCR and .057 quench is 89 octane. I have yet to try 87.

[crustodd]

I wasn't trying to hijack this thread. I was just trying to give the info on what I was experiencing with the parts mix and machine work I had done. I'm about 150 feet above sea level where I'm at for reference.

[SilverXJ]

On my previous stroker I had a SCR of 9.79: and a DCR of 8.56:1. Regular was a no go. Marbles. Midgrade had some pinging and premium no ping. Diamond-x replied in my build thread that he can run regular gas. He has a similar build as I am working on which means his numbers are most likely similar to mine; SCR of 9.55:1 and DCR of 8.34:1.