Pre-Tuner

iTrader: (2)

For the last two months, I've been burning chips and reading through this site. In the last two months, I've got nowhere. I started with my tbichips burn, and started working with that. After 10-15 datalogs, I found that some of my VE cells were above 100 when added together, so that meant starting over. After starting over, 10-15 more datalogs and adjustments and my VE graph looked nowhere near what it should. So, the other day, I started over again. This time, from scratch, with a stock bin that I downloaded from moates.net. To keep everything close, I've only adjusted the BPW because my fuel pressure is so high.

Let me run what I have down for you. 7747 ecm, new 350 crate engine with vortec heads, compcams .488/.495 roller cam, Holley 502-6 tbi @ 21psi, K&N intake system, new GM distributor, heated O2, shorty headers, 3" exhaust, 2000 stall converter.

What was in it was a 350, non-roller, swirl-port heads...basically bone stock.

Between these two engines, there are notable differences, but the displacement is the same. The way I see it, the stock bin should work without too many problems...it should run.

Right now, with the stock bin, it backfires through the TB, stumbles with much throttle, surges when I come to a stop, and is very down on power. This thing is not performing even close to how it should.

Each datalog I run, I drive for about 45-60 minutes, up hills, down hills, slow, fast, etc... The BLM tables I get are fairly complete, with many samples. I just ran another datalog with the stock bin, and some cells are rich, and others are lean. Cells with big differences are sometimes right next to each other. For instance, at 2800 rpm, and 50,60,70map, I have 91,123,and 89. I don't know about you, but in my limited time as a tuner, I know that if I try to correct this, my smooth stock VE graph will not be smooth anymore.

From everything I've read, everyone says to start slow, which I feel I'm doing. I figure the stumble with some throttle is from AE, which I haven't touched at all. It seems to dive when at full throttle, which I'm not worried about yet either. All I want to get right at this point is to get the VE table in the ballpark and smooth. Getting data like I've been getting isn't helping me any, and/or I just don't understand what I'm doing.

Any BLM's with less than 15 samples, I throw out of my equation. I'm using the same equation as everyone else. I'm also using Autoprom with tunerpro RT and WINALDL.

I was thinking that the problem could be something else, but EVERYTHING is new. All of the sensors, distributor and all ignition components.

Anyone have any ideas?

smartman__007

iTrader: (1)

I'm no expert but I'll ask a couple of questions to further enlighten people who are experts. What exact fuel pressure are you running? Without a gauge you wont be able to get the BPW set correctly. Use the equations from https://www.thirdgen.org/forums/tbi/...free-tune.html and try to get your BPW set correctly. Also check the Static Posts. It might explain some weird results from cells close to each other. A BPW below 80 or so should give you plenty of room to adjust to stay below 100% and leave some for WOT enrichment. Get back to us on the PSI if you got it and BPW and post a bin and we'll see what we can do this.

Pre-Tuner

iTrader: (2)

The exact fuel pressure I'm running is 21psi, all warmed up. The BPW I found with the calculation is 97, but I'm using 90 because 97 was still too rich. I'll gladly post by bin, but I'm not sure how. What do you mean by "static post"?

Grim Reaper

TBI is the one area where I have limited experience. The reason, the stock ECMs are so slow and limited in information, that it is almost useless to tune with unless you get a WB. My doctor won't give me enough Valium prescriptions to allow me to start playing with TBI.

You may want to consider posting this on the TBI Board as well. There are many on that Board who are familiar wtih tuning TBI that should be able to help you.

The limitations of the stock TBI ECMs is why RBob developed EBL. You may wish to talk to RBob about it. There is also a post on it.

I too wish I could be more help. You have greater threshold for frustration than me.

smartman__007

iTrader: (1)

Theres a post in the Come in for a free tune thread but it sounds like you dont have that problem. Static Injectors dont have enough time per engine revolution to inject enough fuel. Explaining the weird BLM numbers in close cells. Grim reaper is right, the stock ecm is slow in terms of data rate. Only taking a "Picture" of the senors every 1.2 seconds or so. (Just guessing don't shoot me) To post your bin.. Example, pre-tuner.bin change the extension to .txt and post it with the go advanced button and click the tab Manage attachments, or you could put it in a .zip file too. .zip file would be easier...

honken

You need to nowe your hp and set the pressure to it.
Can the fuelpump take the hp and pressure ?????
Diffrent cam more and less fuel at diffrent rpm and map..
Backfire to tb its to lean or hi timing ????
Blm at 100 to rich surgine to rich ???
Ae and pe can mess with you ???
If you are lean at high map and ve at 100% get more pressure or more bpw values try to set ve at max 95 % on high and lean out the low map..
If blm is 10% rich take off 6% try to take all the rich values thats around 8%
to 12% to smooth it out be careful look at the blm and be smooth on the throttle when you logg or you mess up the logg....
You can do it with ve 2 its changes all map at rpm (remember LEAN on high map bump it up in ve 1).

READ THE STICKY
https://www.thirdgen.org/forums/diy-...uide-book.html

Pre-Tuner

iTrader: (2)

I thought when you log, you're supposed to log using a variety of throttle openings, like gently moving up to speed and other times just jumping on it. That's not correct?

I just bought Rbob's EBL system, so that should help with the datalogging. A wideband will be next.

I figure I should be around 300-320hp, but that's just a guess. I installed a new walbro 255 about a month ago and it has no problem keeping up.

Maybe the backfire through the TB is from being lean since I beleive the AE is way off. The timing is low on the table and the distributor is set to zero.

I'll check out that post again.

Fast355

iTrader: (2)

I have not played with a 160 baud TBI ECM in over a year for this very reason. Everything I have is either 8192 baud or RBobs EBL.

The 1993-1996 TBI applications were 8192 baud.

smartman__007

iTrader: (1)

(Edit)

smartman__007

iTrader: (1)

LoL, Don't remind me Fast355 about the slow baud rate of our TBI's. It's absolutely terrible trying to tune with only a few samples a second. Part of your idea is true about checking all throttle opening rates except the getting on it. If you open the throttle too quickly or too far, you invoke Power Enrichment which involves 5 or so tables of injection parameters. Those I am sure are way off which is causing the Rich/Lean conditions in weird places.

Slowly let into your throttle and never go over about 75% throttle and try not to even Jump from 0% to 25% too quickly as it uses Pump Shot, Wall Wetting, and some other variables to add more fuel to keep the motor from leaning out from the sudden raise in MAP and obvious rise in air entering the intake. There is a setting in your PROM burning program that will allow you to set Power Enrichment TPS% higher so you have a less likely chance of getting skewed data on account of it.

The walbro 255 should supply your TBI with no problem so it's not fuel starvation because of hardware, It's fuel starvation from prom settings. Keep plugging away and keep us updated we'll try to get this solved because I'm actually in your shoes with my brothers TBI motor. His was starving for fuel so we changed the pump and now I need to get my BLM's closer to 128 so I setup an Excel Spreadsheet to use INT and BLM data to recalibrate VE and will tackle Pumpshot, Wall Wetting, Power Enrichment, and other Auto Enrichening features later. First get your Fuel delivery table the closest it can be and your WOT and Pump shot next and fine tune spark advance and go from there.

Fast355

iTrader: (2)

Two birds with one stone.

https://www.thirdgen.org/forums/tbi/...6197427-a.html

https://www.thirdgen.org/forums/tbi/...i-zz4-cam.html

Pre-Tuner

iTrader: (2)

Isn't that one bird with two stones?

alvanwie

Just a couple of hints which may help:

Be sure you have disabled the egr in the ecm, since there is a separate BPC table for when the egr is active.

Your cam change will probably require more spark advance, especially at low rpm's.

The big bore tbi's usually require a large increase in AE settings.

Pre-Tuner

iTrader: (2)

OK, do you have a guess at how much larger the AE increase should be? (as a place to start before I get the WB)

Fast355

iTrader: (2)

I would not touch MAP AE just yet.

The TPS AE is more of the problem with the larger TBI. Calculate the area of the new TBI bores vs. the stock bore and adjust the AE using the % difference. Should get you pretty close.

alvanwie

I would agree, start with the TPS AE. Depending on all the details of your engine combo (intake manifold,cam,heads,tbi), don't be surprised if you need to increase TPS AE setting by as much as 200-500%. If the tbi was the only thing changed, maybe a calculation based on airflow increase of the tbi would be valid, but with the other changes you have made I would have no suggestions on how to calculate the AE requirements for your motor.

Remember the AE changes are only for helping to cure problems with accelleration lean pop. This has nothing to do with your BLM (VE table) adjustments. Logging data for BLM adjustment, you should be trying to do this without engaging AE or PE as others have pointed out.