V2Rocket

Well I've made good use of the tire size calculator and the transmission ratio/speed calculator...

anyone have a chart or calculator that can see the minimum octane needed to avoid knock at certain amounts of boost/compression ratio?

TurboTommy

That'll be hard to do, 'cause there's more variables that have to be considered, like: temps, timing, camshaft, cylinder size, air/fuel.

You could probably get away with pump 87 octane running 8.5 compression with 16 psi boost, on a cool humid day with moderate ignition timing, clean oil-free intercooler, and long duration camshaft, and 11:1 air/fuel
You'd probably need race gas with the same boost/compression on a hot dry day, with a mild cam, a few more degrees timing, and 12.75:1 air/fuel, running it on the track.

V2Rocket

Howabout mildly warm (say, 75F), stock cam, clean IC, 9.5 compression and 15lbs boost?

Would 91 octane suffice?

reno808

just put 93 and above. It doesnt get any easier than that

The DareDevil

Only one way to find out

V2Rocket

The highest (gasoline) octane offered in SoCal is 91. Soon there will be some E85 stations but I don't have the money right now for an ethanol-proof fuel system.

Howabout 10-12psi on those same conditions?

blown 944

NO.

about 10 psi is about all you'll be able to run on 91 IMO with a sc setup unless you have a timing retard box.

95ONE

most cars are already ethanol proof. you're running up to 15%ethanol in your fuel right now. it's just not as bad as the internet has made it out to be. You will need to change fuel filter after 1 tank full to be safe. Turn up the fuel about 30% and advance the timing a little.

Not much more to it than that.

V2Rocket

i was greatly warned by my grandfather (worked in petroleum laboratory for 30-40 years) that ethanol would destroy my fuel system. i imagine my injectors would be fine but the rubber lines i am concerned about.

also, any danger to the fuel pump?

Keithr726

Your injectors would go first, get some delphis

V2Rocket

Things to consider:

stock 944 camshaft
9.5:1 compression
10psi boost (ECR of about 16)
about 70 degrees ambient temperature
clean intercooler
spark retarded 4 degrees
fuel increased 6%

think 91 octane will take it?

944CS

why do you have to run 15 psi?

V2Rocket

on the last post i changed the number of psi to 10. right now im playing with different levels of boost and seeing which is the maximum i can go given my engine's setup and availability of local fuel. regardless of boost i want to use the highest octane readily available, which around me is 91. i just want to see how much i can crank the boost without knocking.

Rogue_Ant

Why not just hook up a counter to pin 15 on the KLR and see if your knocking or not?


Rogue

944CS

he's trying to turbo his n/a, he doesnt have a KLR
also 16:1 is going to be too much for 91