The facts:
Carb to TBI swap on a 383.
ECM = 7747
TB = 454 with 90lb/hr injectors
Stock Cam
Stock 70's era heads (1.94" intake valves)
Edelbrock Performer Intake
Headers
Starter BIN = 5.7L ASDU

The Question:
Assuming I have everything else adjusted correctly...would you expect to have to raise or lower the AE tables in the starter bin? My guess is that I would have to lower the AE because the injectors are much larger (90 vs 65lb/hr). Am I on the right track?

 

Guessing doesn't always work with tuning. If there are no other changes, and the AE was perfect before, then you might have to cut back on AE.
BUT,
sometimes your out of AE, and wind up unknowingly cutting back on the tune, so when you get enough injector you can be more agressive with the tune, and then wind up using alot more AE.

AE is a function of pulse width, so your always having to watch that.

 

Thanks Grumpy. I was afraid you were going to say that. This trial and error method of tuning is taking far longer than I ever could have imagined. I think I have burned over 200 different bins so far. I'm just about ready to fork over my hard earned dollars to pay for a custom chip. How is it that people can pay for a custom chip for a combination like mine and actually receive something that works? It seems that everything with tuning is trial and error. There must be some calculations that these chip tuners are using to get it close, right?

 

You just figured that out huh. You were buying snake oil.

 

Been keeping notes?.
Reviewing the changes, and they're effects?.

Once you *get it* it gets alot easier.

Remember the movie *Days of Thunder*?.
There's a scene where they have the driver go out testing, and set the car up the wrong way, and have the driver get clear on what changes, have what effects.

Might try that for other then WOT timing-fuel.
Just make a couple percent changes, and note how they feel.

There's lots of *experts* selling chips, that probably know less then what you do.

 

Actually, I never bought their snake oil but I have given it some serious thought when I have had bouts of frustration.

 

Yep, I've been keeping notes and reviewing the changes. The problem I have is that I took on a totally custom tune for my first try. I have a combination that no stock bin even comes close. If I could at least drive my rig I would feel like I'm getting somewhere with this tune. As it sits now, as soon as I put the engine under a load it falls on its face. I think the AE is screwed up but I can't tell.

 

Post your main spark, and VE table (and VE adder).

 

This might not be the best suggestion but I'll tell you what I would do. If the engine seems to need AE then dump a bunch in to see what happens. Take notes (like grumpy said). You can always take it back to stock. Going rich is safe,usually. Does it backfire, that could mean you are lean....


I think the main thing when tuning is to just drive the car around. No datalogging or thinking about what the car needs. Once you feel the engine out you'll start to see what's going on. The aldl data doesn't tell you what's wrong. You use that info to help determine what steps to take.

I don't know assembly lanuage nor does any tuning software have a manual. So I just make changes and note the results. Eventually you'll know how much to change things. If you want to know if a change is safe you can ask first. This board is the greatest resource on the internet about ecm tuning. The guys here will do most anything to keep you from buying a "custom chip".

So don't think about giving up and buy that crappy "custom" chip. I have a handfull of custom chips my friends paid for (these chip was from guys like ed wright). The custom chips had many problems so I slapped my tune in there. If you do buy a custom chip be prepared to send it back several times. Each time your "custom tuner" might charge you and get more irritated. Once you get the chip back, you'll find another problem. It's an endless cycle. Don't waste your time. Besides, they'll never get your WOT a/f ratio right(or even close)

 

Well, I started over from scratch today with an ACSW bin. I finally gave up on the ASDU and decided to try something different. This has been a pattern for me now. I burn about 50-60 bins starting with a stock bin, then I get frustrated and start over with a different bin. ACSU, ARJT, AZFT, ASDU, and now the ACSW. Here's the latest from teh ACSW:

Spark Constants


SA Table


VE 1


VE Adder


AE 1


AE 2



The AE may look a little low to you folks but I tried some really high values and that didn't work so now I'm working my way down. My 383 is fed through a 454 TB and 90 lb/hr injectors so I suppose the AE tuning is a WAG.

 

Thanks for the advice. I'm trying to keep from buying a chip. The little demon in my head keeps telling me that it might be worth it if I could get a bin (albeit an expensive bin) that would at least get me road worthy and then I could fine tune it from there. However, I can only blame myself for starting with such a complicated tune. I've been working on this since June of last year so I think I can hold out for another month or so before I blow my brains out.

 

What K/Pa do you idle at?, and have at low cruise.
Are you running closed loop?. WB?

Your VE's total into the 90s everywhere.
What is your BPC set at?.

You might try adding 10% to your BPC, and then droping the VE table values by 10% and see where you are.

 

My engine is now idling at about 40-45 KPa and 700 RPM. Yes, I am running CL but without a WB O2. I'm using a standard heated O2.

My BPC (or BPW in Tunercat) is set at 102. I used a calculation I found on DIY-EFI last year before the site crashed.

BPW = 1461.5 X engine size in liters/# of cylinders / injector flow rate in gms/sec

I don't know if this is right but it's what I've been using for BPW.

 

Set it up to 110, and drop the table values by 10%, and see if that improves things. If it does then try boosting the BPC to 120 and again drop the values. While initially there shouldn't be much of a change, you will be able to get the VE numbers down into a workable range. With them so high, and the added table so high you just maybe out of room to tune much.
BTW, if you read the thread about way tune a stock application, this is what I did in my truck to make tuning more managable.

 

my AE vs tps are up to about 2800 as are the AE vs map at 2500 and it seems my car (350cid) still wants more. i have done across the board (AE) at 5% more each time. it seems to improve each time but air temps got to 40 deg and i quit till 4/04. i had/have a stumble on hard accelleration. some members suggested just the higher tps area and others said just the lower. i did both on the % increase. i am thinking that the lower tps may need it more as that is where i am at(throttle position) initially when it occurs. those butterflies opening up sharply offers the onset of air that needs more AE than my stock bin. now the add on of AE was said to mask other issue areas that may be the real problem? i was at 12.1/1 on wide band in PE so i believe my VE tables may be OK. in prom the commanded PE is at 12/1. now i placed at 12.5/1. spark tables are stock for 84 vette but i took out 2 deg at 2400-2800 at 40 map where KC occurred and that helped.

 

do any of you have an issue with dropping VE table 2 to 0 and just using table one for VE? seems an easier calculation for me. the correct way was posted some time back. i think a couple of the lower rpms table 2 could not be zeroed out( 0 rpm and 3200)?. and the higher ones as well 3200 and up ?

 

Ok, thanks. I'll give this a shot tonight and I'll post the results tomorrow.

 

well its very possiable with only a total of 160pph of fuel aviable that you might need a bit more fuel injector. I havent done alot with tbi setups but i know that the tbi injectors can withstand a good deal of pressure around 50psi i do belive and work fine. SO riasing the fuel pressure might be a good way to increase the avaiable PW times and buy yourself some much needed headroom.

 

AFAIK, the largest injectors GM ever made for TBI were the 90lb/hr injectors. They were available on some, but not all, of the 454s. Since I'm running several cubes less than a 454, I'm guessing that 180lb/hr is enough. I think my biggest problem right now is me just not knowing enough about EFI tuning. I began my research in Jan '03 and started the hardware installation in June '03. It's been over a year and I think I still have a long way to go.

 

I only had a about 20min to work on this last night so I only got to try one BIN. I made the changes that you suggested but it didn't get any better. In fact it idled quite rich. I'm going to lower the VE a little more and give it another shot (hopefully tonight).

 

Well the air dmenads of a low rpm 454 with a really mild camshaft are very different from your 383 with a much more radical camshaft. IF i had picked tpi style inejctors for your build i would have installed something in the nieghborhood of around 210pph total. SO bump that fuel pressure cut back the VE and BPW and enjoy some headroom.

 

No, that just means your bout ready to break through. My advice is to sit down one day and keep burning chips untill you get it right(or close). I have been known to burn over 10 chips a day. That's what you need to do...

 

Only the first year or two, then they went to 80s.
A year.........
I'm working on a decade, and still finding new stuff everyday.

 

NO
NO
NO
NO
NO

It's VE 2 that allows you to keep from overfueling the motor at higher RPM. Unless your shifting at 4,800.
If your going over 4,800, then the fuel curve starts going toooooo rich at higher rpm.

ECM bench time, if you want to see whats going on.

 

I am very new to EFI tuning, but I can offer a general tuning suggestion.

You seem confused as to whether your engine needs more or less fuel. Try this- create a small vacuum leak as close to the plenum as possible (so not to affect just one runner of your intake). Maybe disconnect one small vacuum line, and see if your problem is better or worse. Worse? You need more fuel. Better? You are too rich. The above can be done at idle and cruise. Run the vacuum line inside the car and you can modulate the leak with your hand while driving.

 

Grump please elaborate. i am shifting at 5000 maybe 4800. when i zeroed the tables as instructed by a member. i noticed no change in BLMs as a result of that alone. it simply allowed an easier calculation using one table rather than 2 in calc. my new cam is going in 5/04 so will be running motor at 5500-5800. now you are saying the table 1 plus the fiqures in table 2 (which are still there 3200-6000) will cause it to run rich? how can that be? as a side note my tach stopped working when i installed the accel coil and hei over 4000 rpms so need to work on that b4 i do any high rpm shifts. i was told to try to remove filter and bypass it. that may work,

 

Interesting idea. I'll give it a try. Thanks.