To start I had a bog when I would crack open the throttle, then the motor would finally pick up and accelerate. As a quick cure I set the Stoich. AFR for power enrichment to 12.00... it stopped the bog perfectly, but the AFR was always 12.00 because power enrichment was enabled when LV8 would be at 50. Well the motor idles at about 50 to 60 LV8. Would it be OK to set the min. LV8 for PE for a higher amount say 60 to 70??

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'86 TA, T-tops, T-5, 3.73, 4 wheel disks 350, compucam 2040, performer intake,SLP Headers, 3" race magnum muffler, 1.6 Comp rockers, Ripper shifter, perf. friction pads, Hypertech ignition, Earls brake hoses, Hotchkis springs, Tokico Illumina 5 adjustable shocks and struts, Lakewood panhard and trailing arms
14.50@ 97 with carb... now converted to TPI

 

That was the totally wrong way to fix the problem. What you should've done was increase the pump shot, usually labeled as acceleration enrichment. With a performance engine and parts, you'll need quite a bit more to reduce and/or eliminate the bog caused by the extra amount of air inhaled by the engine.

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Greg Westphal
'87 IROC 355TPI/A4

 

Now I know the difference... as you can see I am new to this and I figured that I would be going rich instead of lean so it would be safer. Now I am playing around with the AE instead, I got it confused with the power enrichment! Thanks for the reply

But now that I am looking at acceleration enrichment using GMEPRO should I rase the factor?? I ask because it starts at .125 when vl8 is 0 and goes to .2 when lv8 is at 256. and according to any of my data logging the injector BPW lowers as the rpms increase.. from about 8 to 6 from 3300 to 5500 revs. So in this case does less AE factor = more fuel???

[This message has been edited by slowTA (edited July 31, 2001).]

 

Glad I could help. The table you're looking at is actually AE vs. -change- in LV8. If you have a bigger change (somewhat corresponding to a bigger change in throttle), you'll need a bigger pump shot (more AE). So, more AE = more fuel.

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Greg Westphal
'87 IROC 355TPI/A4

 

So how much bigger would you recomend... and where??? I know it would be hard to guess at this, but I'm just looking for a little 'kick' in the right direction.


So far I mad ethese changes in GMEPRO
from to
0 .125 .128
64 .125 .140
128 .156 .179
192 .203 .203
256 .203 .203

 

That's definitely in the right direction, but you'll need to use a scan tool to see how much the LV8 is changing when you crack open the throttle, and also to see how well the changes are working. With something like Diacom, you can graph the results to actually see what's going on. The values can go up to 1.00 in GMEPro, so you have lots of room for adjustment if you need it.

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Greg Westphal
'87 IROC 355TPI/A4

 

OK, thats good to know (that you think I'm going in the right direction)... I use Craigs software s I can see that the LV8 goes up to about 120 to 180 depending on how much I hit the gas. The bad part is that I tried the above values and the bog was still there... raising the fuel pressure (from 40 to 42 psi) didn't seam to make a difference. Maybe even a little worse! But then I noticed that the spark advance would take out about 2d when I would press the gas, then it would bog and the timing would advance only after the bog ended. So is the timing right and fuel is wrong, or the other way around?

 

Thinking back to when I had a car with a carburetor, I think a bog means you have too much pump shot, but I could have that backwards. Maybe try removing some of the pump shot and seeing what happens.

If it's correlating more with the timing removed, you can bump up the values in the ESC recovery table. I have mine ramping up to 200 %/sec and there's still room for more. The only problem is that if you're actually getting real knock when getting on the gas, then you won't totally fix it this way either, so you'll need to see where it's happening on the main spark advance table and remove a little timing there.

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Greg Westphal
'87 IROC 355TPI/A4