LETHALRACER

I was looking at my bin for my Camaro last night and realized something strange. It seems that I only have 29.7 deg total timing in my program. I thought that I had to add my initial to what my Auto X-ray said, but it seems that the X-ray already adds it. The bin reads that I have 23.7 deg above 70kpa above 3,500rpm. Shouldn't by timing be around 36-38deg by 2,800rpm. How much power am I loosing. I am guessing 50-60hp.

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91 Z28 ALL FORGED 383,EAGLE 6" RODS,11.2:1 SRP PISTONS,TOTAL SEAL RINGS,MINI RAM,ACCEL 58mm T-BODY,AFR 210'S
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COMP HYDRAULLIC ROLLER
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G-Tech time 12.20@124 w/200lb passanger.

rumair

this definitely isn't an "advanced" question, especially if i can answer it. i have 40* total timing at WOT above ~3500~ rpm. the LT1 loves timing; it still freaks me out that it handles that much and has absolutely zero knock retard across the board.

treyZ28

not exactly advance by any stretch of the imagination...

timing gain is dependant upon how advance you are currently..,''timing can give you a few hp but the amount gained is less and less for every degree you advance it...

in advanced tech terms
lim (g) = 0
g--->infinity

where g is the amount of power gained for another degree of timing advance over the last advance

(assuming no knock use higher octane)

although i think g cant ----> infinity, only 359

just had to throw that in.
basically *(just to use easy numbers that are WAY off) ,
if
1* advance is 100hp over stock
2* is 140hp over stock
3* is 160hp
10* is 165hp

so its not linear- roots equation i think ?


so dont think having crazy advanced timing and 108 octane is going to gie you massive gains- 5-6 hp is the most you can gain in a stock LT1

...moving to LT1 tech- ohh wait i;m not a moderator


edit: Christ i'm doing too much calc and engineering hw today! take a 5 min break and look what happens!

cheers
trey


[This message has been edited by treyZ28 (edited September 02, 2002).]

INTMD8

On all of the LT1's I've dyno tuned, none of them have made more power with more than 34 degrees of total timing. Most can run at 31-32 degrees and lose no HP but gain torque.

rskrause

That's exactly what I have seen with the exception of one car with a solid roller. This was a really high-rev setup with an Accel DFI and it needed something like 36-37 degrees. It was running race gas, and this probably had somehting to do with it as well.

Rich Krause

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'95 Z-28 383: Vortech, nitrous, etc.
AIM: rstevenkrause

ZBass28

What about in terms of a blower car guys?

What are you doin with yours Jim in the low boost, mid-rpm ranges?

GUMP

I have DFI and have my start line timing set at 41 and taper it down to 38 as I go thru the traps. I have tried running it a bunch of different ways and have found that this works well (Cam is 256/266 @ 0.050).

Daren

LETHALRACER

I don't have an LT1. I have an old school L98. Pre 87 short block. Does this make a difference.

GUMP

It makes a difference if you have a regular ignition which is not programable. My car leaves harder with a bunch of timing, but needs to be retarded to get good mph's. On a non programable system you kind of have to compromise.

Daren

LETHALRACER

I have the stock type distributor that came with the 91 L98 motors. All of the timing adjustments are done by the computer.

Eric Bryant

Older heads need more total advance, typically speaking. This is because they've got a less-efficient combustion chamber, so the burn needs more of a head start in order to develop maximum mean cylinder pressure.

The catch is that older heads typically tolerance less advance than newer heads. So, when adjusting timing, you adjust it so that you avoid detonation. This will typically be something less than the advance that yields maximum power. You can do one of two things - run higher-octane fuel, or "upgrade" the cylinder heads to something like Vortecs or Fast Burns. AFRs are excellent heads in terms of airflow, but they tend to require a bit more advance than the newest factory heads.

Do not add excessive amounts of fuel to quiet down detonation caused by excessive spark advance, as the detonation is still occuring (albeit inaudibly). If you do this, you may get the chance to involuntarly inspect the bottom end of the motor.



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Eric Bryant
'96 Impala SS (LT4 396, T56, "firm" suspension)
'96 GMC K2500 (parts hauler/dune runner)
'92 Roadmaster wagon (winter beater)
'01 Honda Accord LX V6 Coupe (wife's car)
http://www.bryantperformance.com