I just pulled my vehicle out of the garage today for the first time in over 6 months. The motor idles really nice (base timing at 6 degrees), but under load the motor is backfiring out the throttlebody.

Here's the major specs: LT1 Intake, LT4 HOT cam, and Speed Density conversion

I can rev the motor while in park and I don't have any problems. When I take it on the road and give it moderate to much throttle, the motor backfires out the throttlebody. Even at lower RPMs under load the motor feels congested or something (hard to explain).

I've burned some of my first proms, only removing VATS and changing the injector flow rate for the 26lb LS1 injectors. I have tried both 26 and 22 for the injector flow rate...same problem exists.

What suggestions do you guys have? Is there something I can do for now with my PROM (i'm using Tunercat) that I can change? I only have Auto X-Ray as I don't have a cable yet for my laptop. What should I be looking for?

Don't know if it helps, but I did notice that as I accelerated the integrator went from about 90 increased to 180.

I'm sure there's a lot going on here, but what do you think the major problem is here?

 

I went thru my first MAJOR tuning experience a month ago or so. Mine did the SAME thing...backfiring out the intake. It wanted ALOT more gas. And ALOT more AE, but I'm working with TBI here. I don't think MPFI needs near as much AE as TBI does.

Also, try 20-24d timing where the engine idles. That cam is going to want alot of timing at idle to stay running.

Hope this helps a bit...

 

There is already a lot about this in the archives of this board. Changing the AE delta TPS table will clear it right up.

Tim

 

Your VE tables need work after that cam swap. Only right way to do it is with a scantool.

 

I did lower the values up to 3000rpm in my VE tables by exactly 15%. I did some research on this board about the LT4 HOT cam and that seemed to be a good starting place.

I'm currently doing the research on that AE table...however there are many AE tables. I hope to make sense of it soon.

John, again thanks for the work on the LT1 intake. I took this pic earlier today. I still have a little cleanup, but this is a current shot of my engine compartment. I'm working on an aluminum air intake...but am more concerned about getting the motor running right first.

 

I'm having trouble searching the archives about this one. The trouble is I don't know exactly what I'm looking for. Can you give me some search tips?

 

Hey wasap Wildside, CrazyH here (Hawaiian97s10 from the Sportruck.Com boards), I would sudgest searching for 'delta table' since Traxion mentioned the AE delta TPS table could be the source of the problems. The best search would be 'AE delta TPS table' but the search function wont let you use anything less than 4 characters in a search. So search for delta table, then look for anything with AE delta TPS table. Good luck!!

 

Thanks man, I'm finding more info with that search.

 

After playing with the AE tables the backfire is gone. It now hesitates a bit. I'm guessing I still have to adjust that AE delta TPS table a bit more...and I'm sure I have other tables to mess with, too.

This is my next question. I significantly increased the values in the AE delta TPS table. See pics below.

Stock


Modified


I know the tables need to be modified to "what the motor wants", but do these values seem abnormally high to you guys? I wouldn't know because I've never had another BIN (for a motor similar to mine) to compare with.