Timing: Low vs. High

[VIN7]

Has anyone every checked to see what the differences in running 93 octane and alcohol with low (18*) timing vs. high (24*+)? Anyone with dyno or track numbers to back it up? I know Steve Hill is a proponent of high timing and Steve Yaklin endorses low timing.

Mike

 

[Steve Y]

I run low timing because I am not out to set records on pump gas plus I hate working on these things. Steve Hill, AKA "The transitional knock kid" likes high timing cuz he loves working on these things and IS out to set records.
LOL
Steve

 

[Mr URL]

This is what I like....using pathetic 91 octane (only thing commonly available at the pump) ....

18 degrees if using 70% isoprophyl 20 psi boost
22 degrees if using 100% denatured 24 psi boost

I don't like transitional knock. I'd rather run less timing with higher boost.

Works for me anyway!

 

[Steve Wood]

Chad, have you tried diluting the denatured with about 40% water?

I have been running my cars that way recently and cannot tell the difference.

 

[Steve Hill]

Oh yeah?! .... well, I say, " if ya wanna be on the cutting edge yer gonna get cut." Uh, yea, something like that. Oh well.

Ok, for the record, I do get varing amounts of knock spiking at the instant of wot. This is nearly always a one-time instance. From from then on until cessation (of wot) I record no further knock, even deep into fourth gear. This would be at 26lbs boost and 25 or so degrees timing.

The higher timing pulls hard on top and launches real nice. Yet I do admit there are occasional large spikes. These can pull a bunch of timing, which, naturally, then kills performance until the software routine gives it back.

THe transitional knock bugaboo I have yet to get a handle on. One problem for me is I am constantly changing things around, can never leave things alone.
This is good, because I learn some things, but, also bad, because after a bunch of years at this w-a thing I'm now hopelessly confused.

I have been tempted to throw a odd number into the ME software setup to ignore this one-time phenomenon except the Yakman would yell at me. Again.

 

[Steve Wood]

He yells at everyone...but he learns too...he has been easing more timing into some of these chips, tho...*g*

Go ahead and stick an odd number in there...a wise user never tells him....same with leaning down the 0-4000 launch curve...

 

[BM Computer Src]

I have found it benefical to reduce the timing in the lower RPM's and middle LV8 areas, to eliminate the transitional knock associated with high timing and alky. Also, I have found the bringing the PE on earlier (vs TPS voltage) will help also, as I usually find the spike in retard occours before the fuel/alky was there (O2's did not rise in line yet). I usually run 22-23 degrees on pump / alky, and about 19-23 psi. However, in race trim I like at least 28 degrees. I tend to tweak my chips, to get the best performance. Sadly, most folks just go buy generic "street / race" chips and will never realize their potential of their combination though.

-Bob

 

[Steve Wood]

Not sure about the tps as lv8 seems to be the factor that seems to trigger PE more often on my cars, but my MEs start with lower timing and end up with higher advance in the upper rpm ranges and this seems to greatly help the transitional knock...I run around 23# of boost.