Guys, I am in the process of tuning my 383 with AFR195's, 216/220 roller cam and a pair of 90lb injectors in 2" crossfire throttle bodies, all on top of an X-Ram. (Essentially the same as a 454 TBI on a single plane manifold).... My question is regarding pumpshot (accel enrichment vs MAP and also vs TPS). I have looked at lots of stock bins to try to determine a relationship between the amount of TPS pumpshot vs the MAP pumpshot and they are inconsistent., Some have equal amounts in both tables, most have more TPS pumpshot (anywhere from 2441-13672!!) I have a bog when I crack the throttle open. I was increasing both tables together in 10% steps, but now my "vs MAP" table has bigger pumpshot than any of the stock bins, including the 454's. It makes sense that the TPS pumpshot would be bigger as it is instantaneous and doesn't rely on the manifold pressure changing before it comes into play. What I want to know is, how do I determine when to stop increasing the vs MAP table and keep increasing the vs TPS table? Ben.

Ben Ron here. like i said before i saw improvement and was at 200% of stock values when i quit at 11/2003. if temps were stable(not falling) i think i would be just fine. have you tried burning a chip at 250% of stock AE tables? i believe i am at around 2700 usec on TPS and 2300 at MAP last i could recall. i think i burned one more greater that that( 3000/2500) but never installed. that 383 is 10% larger than the 350 and may need all the AE you are offering and more. maybe you need more AE down low like 1600-3200 rpm VS adding accross the board, i may have errored by adding too much above 3600. is the the AE falling out of atomization? that is you are giving more but losing due to spray on plenum floor. i am confident the 454 TB will help me in this regard as no plenum floor. straight shot. i assume the blms are in line. i disabled(dont recommend) PE and got 4000 dialed in closed loop. never did that with 4400 however. what type of spark advance are you running? i think aluminum heads need a bit more advance down low. would more advance help the issue? i have not yet advanced my spark tables. i believe they are what they were when taken off the CF forum for stock or slightly modded. any knock counts?

G'Day Ron!
I am up to about 4000 on my delta TPS table, thats more than all the stock 350 (l05) bins, but nowhere near the big block bins (ANTZ 7813 and AZFT 13672 !!) so there is plenty of headrom left there. This afternoon I will go for a test run and leave the delta MAP's where they are and just work on the delta TPS values to see if I can get rid of this bog.
As for timing, I am still running a pretty conservative table while I sort the fuel out, and because I didn't want any knock counts on my new motor. Maybe that is contributing a little, but I think I 'll get some more fuel into it before i increase the timing...

Might have to pull some timing out.
Are you balancing out what your doing with MAP and TPS AE?.
And sudden tip-ins can cause some serious MAP fluctuations, so you might have to shore things up with the VE table to get things correct.

Yes, tip-in MAP at low speed can dump in a lot of AE fuel. Easy to get it correct at mid-RPM then drown the engine at low RPM.

One thing going for you is that the '747 AE has a lot of adjustability. And with all the code in EPROM with optioned features it is easy to change the AE around (There is room to change the code).

RBob.

hmmmm, i am sure it wants more fuel. If it is at cruise and I boot it, all goes quiet for 1/2 a second, oxy sensor volts falls to zero.. After a short period of silence, it suddenly takes off like a rocket!

This afternoon I went on a 90mile trip and logged with winaldl all the way. Picked up very few knock counts which is good and also managed to trim my VE's a bit closer to ideal also.

I backed off the Accel vs MAP a bit, back down to somewhere between where most of the stock 350 and 454 bins are, then increased my accel vs TPS up another 20% (Now around 7000usec). Now it is much better, but still wants just a little more i think.

My thinking is this: I think the vs MAP table comes into play more for load changes like hills and gear changes, whereas the the vs TPS give instant fuel when the throttle is cracked. It seems to be working and now when I crack it open I am greeted by the sound of squealing rubber, rather than a 1/2 second of silence as it was before ;-)
I think I'm geting there with this thing..

Depending on the combo.
Light load, is MAP/MAF based, then mid load AE is pretty much TPS related, and a full hammer drop is a blending of both.

And the PE TPS enable can be a huge influence.

i would think the initial PS is a result of TPS AE and then the MAP sensor detects the pressure drop and hits it a fraction of second later for a double wammy. it would seem possible to get it right on TPS and then overload with the second shot(MAP). i think that is happening to me. if i do an aggressive accel such as getting on Xway it may not stumble but if i do same but floor it at 60 mph i get a gurgle sound from engine and that i think is the overload on AE.. i may scale back the 3200 and above on both TPS and MAP. and only increase at below 3200. if i accellerate moderately to 4000 and then nail it the engine seems to be able to accept all the fuel it is getting and seems crisp to 100mph. WB on dyno showed 12.1/1 at 5100 rpms so not too far off on PE. odd thing is that Dominic's AE is nowwhere as large as mine yet he has larger flow #'s with AFR heads. same 2.00 inch TB. that puzzles me.

Ronny, it seems as though you keep referring to an AE vs. RPM table. In the '7747 there is no such table. Maybe your ECU has a mislabeled table name.

RBob.

my TC shows AE vs TPS and AE vs MAP. PE commanded ratio has rpm table. i see my post was in error. cannot "scale back above 3200". my error !! i have not tuned since 11/2003 so starting to forget.

I am all too familar with that problem, and it doesn't take too long either!

There are a couple more tables for AE. Another one that is important is the AE vs Coolant at LD40C. This is an overall multiplier to the combined MAP & TPS AE. On a cold intake motor it can help to add AE even as the engine temperature rises to operating temp.

RBob.

i will look at that. seems to run real nice in open loop. goes closed at about 155 deg. 180 thermostat. same on cold start with choke enrichment. Starts right up. I can drive immediately. once in closed loop then stumble prone till engine is 175-180 ans then diminishes. maybe this all changes when the 454 goes on. stumble that is. the xram is not a cold weather set up IMO.

Guys,

I'm reading this thread with a lot of interest as I'm tuning my '93 383 LT1 right now and have some transitional problems to work out. I am using Tunercat for the chip editing and I want to work on the AE stuff but the only table listed in the DA3 definition file is AE vs. Collant Temp and AE vs. Differential TPS. I'm wondering if anyone knows if the AE vs. MAP tables are present in the 278 ecm's code?

Also, does anyone know if a listing of all the constants and their address for the 278 ecm (93 speed density LT1) is available as Tunercat seems to be missing some of them?

Thanks,
Rob