Thanks tom

 

Thats SICK Lucas, congrats on that!

 

now if there was only a much wider availability of e85 then i would be on this in 2 shakes

 

wow badass, good work

 

isn't e85 pretty expensive? sorry for double post.

 

E85 is about $2.80 a gallon around here from what I've heard and I'll be on it full time in my EVO as soon as I get my new wideband o2 sensor to Lucas so he can finish my tune

Tom

 

For you guys that have run E-85 for awhile, does it kill your wideband quickly like leaded fuel?

 

Dope numbers Lucas. That thing must be rediculous on the street with that little turbo spooling up so fast.

 

Leaded race fuel kills O2 sensors, not E85 or unleaded gasoline.

Retuning the ECU for E85 is easy. I did it the basic tune yesterday in a few minutes (literally), and it worked perfectly from the get-go. However, even stock frame turbo cars need a 255lph pump and 850cc/min injectors to be safe.

 

So the question is, does the higher compression make more or less power at a given boost level on similar setups while running less timing advance on the high compression motor?

 

Well I have not played with high comp to have real proven # but from what I can tell and know you will make more HP at a given boost level. The thing about timing is if its low you will make big hp gains getting it up but at a certain point you will stop making hp with timing so having the timing the same and higher comp lets you make more hp in the end. My car is still running a good 3deg more then it really needs on the 10:1 comp with E98.

I know in the DSMs I always felt like I could make more HP on the stock 7.8 comp motor on pump gas then I could on the 2g 8.5comp but with better gas or meth the 8.5 comp would make more hp. Been years since I have had back to back cars or much dyno time with different comp. With the tuning knowledge I have now VSs then its hard to say on the higher comp making less hp on pump then.

 

I was running 8.0 to 1 pistons. On the exact same set-up, I switched to 9.5 to 1 the next season. I was able to make more power with 5 degrees less timing at the same boost level.

 

The static compression ratio (SCR) is just a simple static measurement. The dynamic compression ratio (DCR) is the actual compression the engine 'sees' when running, it varies with rpm, and it is the limiting factor. It is affected by a combination of things, including the static compression ratio and the boost pressure.

How much DCR the engine can tolerate before it becomes a losing proposition is largely a matter of fuel octane and boost pressure. A 9.5:1 SCR motor should be expected to generate 5-7% more torque than the same motor with 8:1. However, if the boost pressure rises, and if octane is limited, than the 9.5:1 motor will reach its limit, while the 8:1 motor keeps increasing power.

Also, increasing the DCR with boost pressure will always deliver more power than increasing it with the SCR, because greater O2 density trumps greater mechanical pressure.

With a smaller turbo and limited octane, large cams reduce DCR at lower engine speeds, which offsets a high SCR and allows greater boost pressure in the midrange. Also, because turbo efficiency drops at high rpm (where DCR rises), this reduces the overall DCR, which of course allows for a higher SCR. This is one reason WRC get away with what they do. Increase the turbo size however, and that will change. Where a larger turbo and limited octane however, a high SCR will limit boost and power potential.

What C16 and VP Import do is remove octane as a limiting factor, which allows one to have the best of all worlds. With pump gasoline however, the picture becomes a bit more complicated, being affected by things such as turbo size and efficiency, cams, etc.

 

Very Nice post TedB. It helps me understand a little more about our setup. Thanks very much.

 

what kind of variance do you see in "octane" levels between the various blends of ethanol fuel be it E-70, 85, 98, etc?