Hey guys need a little help with my tune I'm working on

[Jwathen23]

Hey guys I'm working on a tune for my 94 gmc 2500 using tuner pro rt.. I have all the correct definition files as well as my bin.. $0e.. I've gotten my ve tables pretty decent still a bit off though... I'm using just a narrow band o2 sensor and using blm data to adjust ve tables.. I can't seem to supply enough fuel at high map readings.. I had pe turned off then just turned it back on thinking it should help out in the high map values... I was wondering what exactly does pe and ve do?should they be turned off when tuning ve tables? Mostly ve? Also what is the best way to tune spark tables? My knock counts are like 40000 don't know if it's a bad knock sensor or its getting false knock readings? I've heard you use knock counts to help tune spark tables is that correct? I'm new to this tuning deal and this is my first tune I'm working on... had to tune my truck because I added vortec heads and a marine intake..

[Kitch]

I have a 94 G20 van and had trouble getting the full throttle end of my VE table to respond to changes. In my case the stock injectors were maxing out so I increased the fuel pressure with an adjustable regulator, after a few tweaks the VE table then started to respond. To get an idea how hard your injectors are working have a look at how high your injector DC% gets at W.O.T.

[Jwathen23]

Yeah I've noticed there like 12 volts!!.. the problem I'm running into now is a guy thought me a trick to lower your injector flow rate by let's say 5% then lower all your ve tables by 5% to besides the ones that need more fuel... it's worked so far but I'm getting to the point that I've lowered the flow rate by 10 percent... what do I need more fuel pressure or bigger injectors? More fuel pressure means to buy the adjustable fuel pressure regulator to the tbi.. and of course more fuel is to buy bigger injectors

[Jwathen23]

Actually checked it out this morning went up to 17 volts

[Jwathen23]

I am running 11 psi of fuel pressure now if I buy that regulator and run 13 psi will that little bit make a difference?

[Kitch]

There are guys around here that know much about tuning than I do but with my limited knowledge I would say if you are running Vortec heads, stock injectors and 11psi fuel pressure you will have problems. Have a read of this post, it explains what I found: TBI Injector DC%

[Jwathen23]

The read sounds interesting seems like I am running out of fuel.. in tuner pro I don't have a graph that shows the % left of my injectors but I can tell you there in like 17 dc%.. so up the fp or would I need bigger injectors

[lionelhutz]

When you are tuning the VE table using the stock O2 sensor and BLM data you need to ensure you only use data from closed loop operation. Narrowband O2 sensors are completely useless for telling you any AFR besides stoichiometric.

The VE table is basically the reference the PCM uses to figure out how much air is entering the engine. Knowing the air, it can then calculate the correct amount of fuel. In closed loop operation the PCM calculates the fuel for stoichiometric operation. Then, it watches the O2 sensors and make a correction to the fuel. The correction factor is the BLM number.

At high throttle, you want the fuel to be on the rich side for best operation. Well, the O2 sensor is useless for this so the PCM goes open loop and calculate how much fuel is required without using the feedback from the O2 sensors. This is the PE or power enrichment mode.

Personally, I think starting with VE table tuning using BLM numbers is OK to start. It gives you an idea of what happens and how much of an effect changes have. One of the biggest problems someone first trying to a tuner has is making changes too big and not smoothing the table. So, make small adjustments and keep the table fairly smooth looking. Also, try to operate the engine in a stable condition in any cells you're logging and adjusting so the BLM data is valid.

Timing is a lot tougher. The cumulative knock count is useless. If you're operating at a certain point, say 1400rpm and 45kPA for example, and the knock count is increasing then you could try lowering the timing at that point.

You understand what the timing table means? The numbers in the RPM direction are basically like mechanical advance and the numbers in the kPA direction are basically like the vacuum advance. The table column at 100kPA is basically your mechanical advance curve with no vacuum advance. Then, as you move to lower kPA columns in the table you add more vacuum advance.

So, where did you see 17V in regards to the injector pulse width?

Overall, I would agree you need more fuel pressure to feed your modified engine. Have you checked-out the "ultimate TBI mods" yet? Part of that is info on making the stock regulator adjustable so you can turn-up your fuel pressure. You can probably get 13psi without buying a regulator.

What fuel pump are you running?

[Fast355]

To fuel a STOCK Vortec engine you are going to need about 22 PSI with your 61# injectors to push them up near 80 lb/hr or you could run 80# 454 injectors at stock pressure. Your stock fuel pump will open the bypass valve about 15-16 psi and will probably not flow enough to feed the 80#s.

[Jwathen23]

I'm running the stock fuel pump... the fuel pressure is reading right at 11 psi now... I've ordered thr adjustable fuel pressure regulator for the tbi with a gauge and fitting from cdi technologies... what's the most psi I can get out of this stock pump... I know you can use a tpi fuel pump if you need more fuel pressure and regulate it down... I seen the 17 driving down the road in tuner pro rt using the dash board.. I'll see if I can get a pic

[Jwathen23]

So 454 injectors with the tpi pump?

[Jwathen23]

Hard to do while I'm driving but that was at like 30 mph and about 90%throttle

[lionelhutz]

No, either 454 injectors or a TPI pump for more pressure.

The top row second from left is inj %DC, right? You want to see what that goes to at WOT operation.. 100% should indicate the injectors are fully on, but I can't verify if it's correct or not. If you were 90% throttle at a fairly high rpm them I'd question if that is correct or not. Basically, If it reads right then once you are close to 100% and the injectors are full-on you can't get any more fuel.

[Jwathen23]

No on this dash it's second to bottom row second from left it's called inj dc% sorry I thought said that my stock pump at 15 psi still wouldn't feed the 80# injectors..

[Jwathen23]

Which way would you go? 80# injectors with the stock pump or a tpi pump for the 60# injectors next week I'm ordering a mild cam and headers.. which would be best.. and how did you get vortex heads need 22 psi? Not doubting you or anything just curious how I could find out stuff like that