What am I looking at under the "high octane spark,..." thing. I see the grams / cylinders, but what is it .... grams of what ... mixture???

What values or areas should I be looking at to learn to adjust???


In terms of MAX performance, should I ignore the values between 400-2000 rpm and 0.40 gm/cyl and say 1 gm/cyl and jsut concentrate on the other values???

thanks <img src="gr_eek2.gif" border="0"> <img src="images/icons/confused.gif" border="0"> <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

 

Howdy! I'll field this question.

Well, I think of the gm/cyl as a percent load. So, 1.0 = 100% load and .60 = 60% load. That beeing said, I looked at the stock tables and determined that from 60% up the stock tables are "pretty much" the same. Then takeing that info I determined what I wanted WOT timing to be and changed the graphs accordingly... Basically I made the 60-100% graphs nearly identical and I have mine setup for 28 degrees at 4000 rpm then at 5000rpm its goes up to 30 till 8000rpm.

I tried out 31 total, but it was riding the line between knock and no knock.

BTW, if you are looking at AutoTap you can read "calculated engine load" which is determined from MAF, MAP, and RPM. These are tyipical things that a timing curve would be based off of...

Hope that helps!

Ryan Karasek <img src="gr_images/icons/cool.gif" border="0">

[ February 19, 2002: Message edited by: Ryan Karasek ]</p>

 

Ryans Answer is quite correct. The one question he didn't answer was: "Gms of What" This value is the amount of air in each cylinder fill. This is used as a measure of Load, as Ryan explained.
Ken

 

Mine goes to 1.2Gm/cyl, can I assume that is 100% TPS, is 0.6Gm/cyl 50% TPS?

 

thanks for the reply.


Hmmm mine goes up to 1 gm/cyl... now I have seen two '99 vettes go up to 1.2 gm/cyl.

Why is that ?? My vette is a '98...looks like they changed a little bit...

 

CJones:
It really doesn't relate to TPS directly. Its more of a vacumm vs. MAF flow rate calculation. When I said WOT before, that really assumes MAP goes near 100 kpa and the MAF sences a higher flow... But realy try to think of it as load. And on that note I'll say that from the factory, it appears any thing over .60gm/cyl is near WOT. Hope that didn't confuse anybody.

Ryan K <img src="images/icons/confused.gif" border="0">

[ February 20, 2002: Message edited by: Ryan Karasek ]</p>

 

is there a way on ATAP to measure the gm/cyl to check the area that we are under WOT as it relates to those tables??

"I have mine setup for 28 degrees at 4000 rpm then at 5000rpm its goes up to 30 till 8000rpm."

so you took the entire block from .6 gm/cyl - 1 gm/cyl @4000-5000 and amde all those 28* then the block from 5000 on all 30?
<img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

 

gm/cyl is in fact a measured quantity.

It's not a loading number directly.

You can ATAP, and gather the data needed to calculate gm/cyl

all you need to measure is MAF and RPM

if your measuring MAF in lb/min, you will need to convert to g/s. Converstion is: MAF(lb/min) /.1323= MAF (g/s)

You have RPM. There are 4 cylinder events in 1 revolution

So, you have 4*RPM/60 cylinder events per sec or RPM/15 (cyl/s)

you want g/cyl, this is MAF[g/s]/(RPM/15 [cyl/s])

or g/cyl = 15*MAF/RPM

FWIW, i see upwards of 1.4 g/cyl under boost, although i just stay in the last part of the table then <img src="gr_stretch.gif" border="0">

While the calculation will not be dead on, it will put you in the right location

[ February 20, 2002: Message edited by: y2khawk ]</p>

 

I asked this same question a few weeks ago..

I was told that Grams/Cylinder was calculated by dividing Grams per second by 8 to get Grams per Cylinder per second and then divide that by RPM's to get Grams per Rev per Cylinder.

Is this not correct? If not, how do you get to that number??

 

remember, it takes 2 revolutions of the engine to get all 8 cylinders to fire.

re-read my post above <img src="gr_stretch.gif" border="0">

 

Y2KHawk.. FINALLY! Someone comes up with a formula and explanation that I can buy! Thank You.

Tom

 

y2khawk, you the man!

I'm programming a 99 Firebird with a B1 cam this weekend, looks like I'll need to bring a calculator too.

 

Sorry to bring this back from the dead...good info, what I was looking for.

 

good info! but i still don't get it.

i can calculate my g/cyl and see 1.05 up to 1.11. my timing chart in that area on high octane shows a max of 10deg.

for some reason atap is showing 14.5deg of timing thruout the entire run. i added 2deg to that chart and still see 14.5deg of timing.

anyone know what i am doing wrong?

 

Excellent!!!! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />