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Old 01-10-2011, 07:05 PM
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Default How much timing advance do YOU use, 4.3 TBI & CPI How much timing advance do YOU use

How much timing advance do YOU use, 4.3 TBI & CPI

I'm an old wrench, we used to put the timing off the scale back in the old days, with massive results in HP, of course we'd open the jets or put in smaller needles in the case of the Quadrajet

Several guys here have 4.3 engines and want to jack the timing..

Here in N.Ga, altitude 600-900' Humidity usually high.. temps from 8F - 100F

I know most of these 4.3's suggest 0 degrees, at temperature, a/c off etc

So HOW MUCH ADVANCE do you guys get by with regular fuel with minimal pinging and of course NO Detonation [both different events]

Right now, the 2 vehicles in question are:

1. Vehicle A = 94 CPI Jimmy 4X4 auto
2. Vehicle B = 93 TBI S-10 2wd auto

Both vehicles have good compression across the board, stock and unclogged EGR, good overall condition with No "check engine" Codes
No skips, both running good as is, we desire more economy.

We know where the brown EST disconnect wire is
[under the passenger mat next to the heater box]

So ANY feedback regarding 4.3's, even you guys with OTHER year vehicles is very much appreciated..

Also, besides power gains, any fuel mileage improvements doing this ?

We all know sometimes added timing lets you "feel" more power hence a little heaver foot, often resulting in worse mileage..

Thanks in advance
DrVette
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Old 01-10-2011, 07:48 PM
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I don't think you can advance the timing for the results you are looking for as the PCM will just try to adjust it back to how it is programmed. Hate to say it but your best bet is to have the PCM tuned rather than trying to adjust the timing mechanically.

Now, if you swapped over to carb'd setups...
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Old 01-11-2011, 12:06 PM
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Quote:
Originally Posted by AJBert View Post
I don't think you can advance the timing for the results you are looking for as the PCM will just try to adjust it back to how it is programmed. Hate to say it but your best bet is to have the PCM tuned rather than trying to adjust the timing mechanically.

Now, if you swapped over to carb'd setups...
I expect if that was done on a 92 S10 W engine such as mine, which got about 23 MPG in 92 when I bought it new, that the MPG would go south in a big hurry, along with the HP.
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Old 01-12-2011, 11:45 AM
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Quote:
the PCM will just try to adjust it back
On vehicles with the same system as my 96 Yukon w/5.7L Vortec, you are absolutely correct.

AFAIK, on these units with a "timing scale" which allows for initial timing set, I am pretty sure the timing will "stick" and only be retarded by signals from the Knock Sensor on the side of the block..

These systems, particularly the Z engine, is almost identical to my 94 GMC 1500 w/5.7 TBI and I ran 6 degrees advance on 87 octane with No pinging and No Detonation.

Thanks for the replies, any and all inputs are appreciated and fully considered

DrVette
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Old 01-16-2011, 07:57 PM
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A note of importance here.

Originally this 94 CPI vehicle had a -3 degrees timing, I kept getting O2 sensor & Fuel Rich Codes.

Setting the timing on factory spec 0 Degrees stopped the Check Engine Light..

I had already pulled the top half of the plenum to check for leaking fuel lines, FPR and replaced the O2 sensor, checked the plugs, wires, replaced the coil as it was leaking fire badly..

I had loaned my timing light to a "pal" who dropped it and returned it broke it, finally I took it to another guy and paid him to check it out for vac leaks, timing, FPR pressure etc.

All that and what it needed was the timing set.
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Old 01-16-2011, 09:57 PM
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Ah, the old timing light! A valuable tool lost on the generation of computer controlled engines. I've still got mine, though it is a bit dusty and hasn't been used in a few years.
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Old 01-20-2011, 12:05 AM
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Well you still need a timing light to set the base timing on TBI engine, I believe we set mine to 6 degrees advance on my 350 also with the EST wire disconnected. I can't remember what the timing shows when you check it with the EST hooked up after it readjusts itself.
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Old 01-20-2011, 03:40 PM
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Quote:
the PCM will just try to adjust it back
This does not relate to the 94 CPI.
When the timing was moved from a -3deg to 0deg the O2 & Fuel Rich code went away.

This DOES relate to my 96 Yukon which does NOT have initial timing set and no info on the radiator support except "do not adjust timing, the ECM etc"

thanks for the replies
DrVette
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Old 01-20-2011, 09:55 PM
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i had my '92 Jimmy set @ +9, and never ran into any issues.

but it sure did seem to take awhile before i saw any improvement in fuel mileage. must've been the new break in period.
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Old 01-20-2011, 10:08 PM
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my 91 4x4 2dr, With timing set at 0* i was getting roughly 250 miles to the tank. I did a cat back,and a k&n,ac delco plugs,and set my timing 4*,and actually lost 22 miles to the tank. set it back to 0,gained it back plus another 10. I did notice better throttle response though at 4* my lead foot doesnt help either.
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Old 01-20-2011, 10:08 PM
 
 
 
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43, advance, advanced, blazer, chevy, cpi, detonation, elevation, motor, pre, relace, retarded, table, tbi, timing


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