TPS vs MAP AE 7427 $0E

[Fast355]

I've run into the same problem. Popping is not rich, it's lean. IIRC there is a max PW size that needs to be increased. Then you'll probably end up reducing values in the other two tables.

You'd think the high pressure cal would be closer but the high pressure 454 had a TBI specific manifold which had a smaller volume than the old carby manifold plus adapter.

Increasing spark advance or changing the spark retard limit can increase how quickly the engine accelerates which in turn draws the fuel/air mix out of the manifold before it can ignite.

Edit: Yes, the maximum Async pulsewidth value will limit total AE.

Lack of timing advance can also cause popping.

[CDeeZ]

In the beginning of my tune learning I chased what I thought was a lean pop. After install WB realized it was not lean pop but anticipated spark retard. I lowered the amount of spark retard allowed and increased advance in the 60-85 map area and haven't had a pop in years. I had a friend with mod 454 that had similar results. Your mileage might be different.

Interesting. I know this is a lean pop because I can see it on the WB02 gauge itself, as well as the logs. I have wondered if I don't have enough timing now though.

I've run into the same problem. Popping is not rich, it's lean. IIRC there is a max PW size that needs to be increased. Then you'll probably end up reducing values in the other two tables.

You'd think the high pressure cal would be closer but the high pressure 454 had a TBI specific manifold which had a smaller volume than the old carby manifold plus adapter.

Increasing spark advance or changing the spark retard limit can increase how quickly the engine accelerates which in turn draws the fuel/air mix out of the manifold before it can ignite.

Edit: Yes, the maximum Async pulsewidth value will limit total AE.

Well what I was saying is that increasing the Delta TPS and MAP AE seems to help lessen the lean pop when you smash the throttle open quickly, however, those same changes appear to have made it overly rich on very light throttle tip in pulling away from a stop. It literally pegs my WB on 10 AFR for a second or two. I've read several threads on TGO where Dewey talked about having a similar/same issue... Here's one I stumbled on
https://www.thirdgen.org/forums/tbi/...ifold-big.html

Where is this max PW you speak of? Do you think the 350 AE parameters would be closer??? I thought with the big throttle body and single plane carb intake it would be closer, but now that you mention the 454 manifold was smaller.......

Lack of timing advance can also cause popping.

I was running the stock L05 timing table from the $0E bin I started with. I then copied over the timing table from Brian, (sturgillbd on here). His timing table IIRC has a little more advance in it. It seemed to help mine with the lean pop when you smash the throttle open....

I'm running TrickFlow aluminum heads https://www.summitracing.com/parts/SUM-162108

Maybe with these new heads and the single plane, flat top pistons and everything else I don't have near enough timing advance for this combo? Anyone have a timing table for such a combo that might be closer in the ball park vs what I've tried?

Initial spark advance is 3*

[PlayingWithTBI]

I have the same heads and a 46mm TB with 18LB spring on a 3704 intake (bored out to 48mm).

AMUS 2.JPG

[CDeeZ]

How's yours running? My TB measures nearly 52 MM... One of the reasons I suspect AE is what is causing this lean pop.

[PlayingWithTBI]

How's yours running? My TB measures nearly 52 MM... One of the reasons I suspect AE is what is causing this lean pop.

It's getting better, Dave helped me get the Main Fuel table dialed in so my BLM is ~127 ave. Now i'm adjusting VE and PE with data logging. Of course mine's an '88 with 7747 and I'm guessing my cam (207/213 @.050, .466/.484 with 1.6 rockers) is milder than yours. Here's where I am so far;

PE-AE bin 06.JPG

[1project2many]

Well what I was saying is that increasing the Delta TPS and MAP AE seems to help lessen the lean pop when you smash the throttle open quickly, however, those same changes appear to have made it overly rich on very light throttle tip in pulling away from a stop.

The first 25% of throttle angle change makes a greater difference in air density than the next 50%. I tend to ramp MAP AE in faster than TPS on a larger plenum. Then I'll increase the MAP difference to enable AE as a limit to MAP contribution at low throttle angles. This helps prevent rich surges when load changes without much change in throttle.

Are those heads a fast burn style? They might require a fair amount more timing.

[PlayingWithTBI]

The first 25% of throttle angle change makes a greater difference in air density than the next 50%. I tend to ramp MAP AE in faster than TPS on a larger plenum. Then I'll increase the MAP difference to enable AE as a limit to MAP contribution at low throttle angles. This helps prevent rich surges when load changes without much change in throttle.

Are those heads a fast burn style? They might require a fair amount more timing.

Thanks 1p2m, Good info! These heads (SUM-106108) have 170cc intake runners, from what I understand "fast burn" heads are 210cc which come into power at higher revs. Although these heads have bigger valves (2.02/1.60 compared to ~2.00/1.55) I'm wondering if they are a good match for a single plane manifold with a 7.4 TB on a SBC???

CDeeZ: do you have a 5.7 or is it stroked? A 350 @ 6,000RPM only needs a little over 600CFM (check out the "Carburetor Sizing" at the bottom")

http://www.tciauto.com/tc/racing-calculators