4.3L 7747 Vortec Heads, Iron LT1 Timing Table.

BLMS are in the 126-132 area after a half hour drive (freeway and stop and go).

When I give it just a smidge of fuel (grandma type acceleration) It does okay. Give it moderate (20% delta TPS) and the WB will show 11-12:1 for half a second, then shoot up to 15-16:1 and start bucking/lean popping.

Once the rpms hit say 2300ish or I enter PE... it takes off like a rocket (so far so good with the vortec heads power wise).

Seems like the AE isn't lasting long enough, but I don't see a length or decay table in the 7747-mine.ecu.

Once I hit 3600rpm no matter what I change it starts to lean out so I'll check the pressure tomorrow.

How do I get the AE to stay longer?

 

Way beyond where I am, but AE length is in the "Delta TPS/Map AcelPmp uSec" tables isn't it?

 

Are you sure the fuel pressure is not dropping under load. The AE should be just enough to get you into PE mode. Have you tried changing the PE enable TPS table to something more performance oriented?

 

I don't think there is, I hope I'm wrong! That might be of some use... or EBL . ANYWAYS...
Try this; use the VE table for your AE. In the higher MAP areas where you're not cruising, you can add AE. It'll be fake, obviously, but it'll work rather well. Remember, a VE table "should" be rather smooth always increasing with MAP and increasing up to around peak torque, then start to go back down. If you're just learning in the cruise cells it does nothing, absolutely NOTHING for your AE. You must move the cells in the upper MAP ranges if it's backfiring through the intake or try adding more MAP AE.
The other issue with TBI is the size of the injectors. They're really really small and even smaller when you look at them from the perspective of having more AE than port injection! The smaller the injector, the longer it has to stay open to get the same fuel in but sometimes there isn't enough time to stay open... this is when you backfire lean with TBI. Small injectors = crap for this main reason. Larger injectors can deliver that much more fuel when the engine needs it.
BTW, you should be shopping for EBL soon. It'll solve your TBI AE tuning issues and then some (shamless plug).

 

Weird thing is... when I hit just the slightest hill.... my map goes to 80-100 at the say 1500rpm range!? And goes lean.

I'm going to check fuel pressure tomorrow. Have to rig something up. I have not tried bringing the PE down. I figured I shouldn't really hit PE at 20% off idle throttle, right?

The AE I do get, lasts for less than a second.

Baddog, those tables are for quantity.

My Delta TPS is maxed at 25% at the 15555 and slopes down to 0.0

If I set the Delta MAP to any higher than a sloped 4000uSec downward... then it's too much intial AE.

My BPW Constant is factory 181 which fits exactly with the formula. I have the fuel pressure on the TBI cranked (which helped alot.)

Some of my VE tables are adding to be over 100. IE 3600+ Guess that would really mean that with boosted FP, there is a volume delivery problem somewhere.

 

I would grab some 350 injectors (leave the pressure stock 12 psi) or 305 55lb/hr injectors and put the fuel pressure at 15 PSI (You get the same 7.7 grams/sec). That will get you more fuel, faster! Just make sure the pump is up to it. Don't forget the fuel filter and strainer! With either combo your BPWC will need to be 135. That will drastically raise your RPM potential before you go static and get you more fuel during AE! IF low BPWC numbers bother you, mine is set at 75! and I have the equivalent of 105 lb/hr injectors on my 305!

 

This is a v6.. The injectors are 45s.

Bigger injectors would work. TBI definitely is interesting with how much it needs to spit out.

Filter and pressure are tomorrow.

Fuel pump is identical to stock thirdgen L03

Do I need to retune what I have for the bigger injectors, that should all be BPW constant set right?

 

Actually your stock injectors should be 40 lbs/hr per Turbo City, they flow matches many of them all day long.

By simply setting the BPWC with the injector change, my experience is the truck will start and drive decent, but far from perfect. The VE table will need alot of work. I am almost sure it needs alot of work anyway due to the vortecs.

With the modest cam that came in the 4.3 Vortecs and Vortec heads, they made 200 FWHP. I am guessing your 89 4.3 has the stock 89 cam in it. In that case you are probably in the 180-190 FWHP range. Your injectors flow enough fuel at 85% duty cycle and a BSFC of 0.500 to make 136 FWHP. See a problem there.

The above mentioned injectors at their corresponding pressure recomendations will flow 61 lbs/hr each. That is enough for 207 FWHP.

Some of the later 4.3s with 170 FWHP came with 305 55 lb/hr injectors stock.

 

61# tbi injectors flow about as much hp worht of fuel as 15.25# TPI injectors... see a problem? REALLY small.
Even the bbc injectors at 75# aren't much at stock pressures. That's like having a TPI motor with 19# injectors (stock only on the 305's, not 350's).
New fuel pump + more fuel pressure = better all the time until you're running such a small idle pulse width that you're running super rich or injectors aren't opening. Which in that case, turn down the pressure just a tad

 

Basically JP is saying a TPI pump (or Walbro, etc.) in the tank along with a different spring in the regulator! Last time I checked, you can get the spring for a 1995 TBI 454 truck that is 28-32 PSI, straight from GM.

There is also a AFPR on Ebay that is supposed to adjust from 5-40 PSI and can be Vacuum Referenced.

JP - double check your math you are only feeding 6 cylinders vs 8 with the 61# injectors. With that you have the equivalent of 20.3 lb/hr injectors. The stock 40# is like having 13.3 lb/hr injectors. Late model vortec 4.3/5.0/5.7 poppet injectors are 19 lbs/hr. See some more of the problem.

 

I think I'll buy a walbro, stick that in the car, and use the TPI pump for the Jimmy. LOL

I'd like to figure out the AE part though. It's a daily with 4x4 it wont see alot past 3000rpm really.


Oh and it is the stock 89 cam. Only reason I did the vortec swap was because I got the heads for dirt, and my old heads had leaky guides.


is $20 a good price for 350 injectors? I'm used to paying $250 for the 30lb SVOs that I have in the car?! LOL

 

The pair for $20? If so it is a pretty good deal, if they are in good shape. New ones are about $100.00 each! If nothing else you can buy them, then have them cleaned.

I really think that your AE is a VE issue and could also be related to the injector size.

 

i can relate to the AE issue. up until late this summer i did not have a handle on it. i took JP recomendation of adding fuel in those cells in VE that you seldom see cept when in AE. "crutches" AE. i stole that phrase? I added some more(15%) in those cells should have added more? i will suggest it helped. stopped tuning November and find still need more AE MAP. values for AE TPS are adequate A/F yet it (TPS) times out too quickly as you state. my PE is at like 50% TPS and that too can help out AE in transitions if i move to 30% and i did but not yet ran that bin. gas mileage may suffer.

 

It's been a while since I did any tuning, since my motor blew and all, But if I remember correctly you can fiddle with the TPS filtering value to lengthen or shorten AE. I think I read that in Rbob's fueling paper. I'd check my notes, but they're at my parents house with the car.

 

I've read about the lag filter, but was unclear on just how it would effect duration of AE.


Put my PE to 30% and it helped a little, but still pops a bit before fulling hitting PE.

Think I'll pick up those 350 injectors.


I've added a bunch of VE in the 60-90 cell lower rpms. To the point that with the two VE tables added, it's over 100%. Still getting about 135-145 blms in those cells.

Had the fuel pressure gauge on and got 8psi with the pressure cranked. The adapter I was using was leaking fuel a bit so the reading my be skewed, need to find something else out. Brass fittings with nipples into a Tee with lots of teflon tape is not such a hot combo apparently lol.

 

Theres also a constant, or two, depending on the ecm, thats used to decay out the AE. If you increase its value, you can extend the time AE is in effect for both MAP and TPS.

Also make sure that the '0' cell in both the tps and map AE is equal to zero. Youll want this since the computer slids down the table as the AE decays out. This along with the decay constant will allow you to dial in the magnitude, decay rate, and duration of the AE

 

There is no constant in the 7747 for AE decay/duration. Those are zero, because if there is zero change, it shouldn't be adding fuel! :O)





On a side not. Got the fuel pressure fitting to stop leaking. Reads 8psi at idle. Give it a little gas in the driveway, and the pressure drops to about 4psi. Even if my gauge is off on the Actual psi reading, it shoudn't drop like that.

YAY! Found the source of hte problem. I'm seriously going to have to tune down the ae tables and such when I get it fixed because they are incredibly high now! lol.

Thinking Walbro for the Car, and the TPI pump for the 4.3L

 

And why not?.
In my lil world I tune to make the engine happy, not to what I think it should want. If it takes a low PE enable, then so be it.

I have some other items changed, and my WOT voltage is much lower the what you'd expect, and here's what my TPS PE enable table looks like. The 160 figure is in the neighborhood of 1.6v if that helps.

*---------------------------------
* PE TPS THRESHOLD VS RPM -
* TABLE VALUE = %TPS * 2.56 -
*---------------------------------
FCB 70 ; 400 RPM
FCB 70 ; 1200
FCB 160 ; 2000
FCB 160 ; 3200
FCB 130 ; 4800

 

Wow, that's almost off idle!

Either way, my fueling system needs to be revamped first hehe. Need to be able to get it there.

 

There are 'decay' constants for the TPS and MAP terms that are used to generate the delta TPS/MAP AE terms that are used for the lookups. This is done by subtracting these terms from the standard MAP and TPS to get the delta value, which is then used to perform the lookup.

These arnt decay terms in the usual sense, but I like to think of them as that. These will actually be listed as 'slow TPS' and 'slow MAP' filter terms. The higher their numerical value, the faster the AE decays out. I dont know offhand what the addresses are for these in the 7747, Id have to go and look.

 

Knew it from the minute you said that it was popping, you weren't getting enough fuel and the pressure was dropping under load. I bet that is the actual reading! Seen it numerous times. That and the fact, the BLMs were tuned pretty decently.

Forget putting the OLD TPI pump into your 4.3. I would hate to hear that a couple of months down the road, that pump fails. Get you a Walbro 190 for the 4.3. It is more than adequate and will serve you well. Then get the 255 for the TPI. Better safe than sorry, IMO!

IF, it were my truck, I would put in the 190 Walbro, grab a pair of 350 injectors, leave the pressure at 12 PSI, set the BPWC at 135(stock 350 setting as well) from the 181 stock value (then use the AE settings from the ASDU 350 .BIN file. You have the same displacement per cylinder as a 350 and the same injector flow vs. pulsewidth. Should get you in the ballpark.

 

Ah, here we go. The filter coefficients in the 7747 are actually tables with the filter coefficient being dependant on coolant temp.

The table for the slow filtered AE TPS starts at $D31D and the table for the slow filtered speed density MAP (used in the AE routine and elsewhere) starts at $D306.

The higher the filter coefficients in the tables are, the faster the AE will decay out. The caveat to the MAP filter coefficient is that the slow filtered MAP term is used elsewhere, so changing that one can have an impact on things like decel enlean.

 

Id also hold off and work with the AE and be sure that it really does need more duration, and not more MAP or TPS AE in certain spots.

I found myself needing more duration after messing with everything else.

A good rule of tumb for me was that if the zero cell needed to have AE in it, then I didnt have enough duration.

 

I would hold off all work with that truck, until you get the fuel to support the engine. That means more than 8 PSI idle fuel pressure and certainly more than 4 psi at a throttle snap. That and get yourself an injector that will flow enough fuel to feed your engine. Otherwise you WILL be tearing down and engine that has pistons with burned holes in them. Ask me how I know?

 

I missed the rather important side main note of the cause of the problem in the above post. My bad.

 

Just bringing it to everyones attention. I am sure he will still have plenty more questions, when he gets proper fuel delivery.

 

The Fuel Pump in my Car is only 2 years old. It supplies enough fuel for my Sold Cammed 300RWHP engine(see sig). Pressure doesn't drop at all. Will get a 255 for the car.

 

Yes...

It may be true that your stock fuel pump will not support your new setup and may need to be changed anyway, but here's some food for thought based on my own experiences.....

Before you change the pump, check your wiring thoroughly. If you have a bad (green/ corroded) connection in one of the plugs or a bad wire, the fuel pump will see low volts under load and not perform like it should. The fact that your pump is only getting 4-8 psi makes me leary that this might be the case......and/or a plugged fuel filter.

-Mike

 

Replaced the fuel filter before testing pressure. It drops PSI in neutral free reving just a bit.

When I start thinking about the engine before the head swap... it was real pathetic like when you first gave it gas. If you eased into it, it would go, or if you downshifted. I think it was going way lean there too, just now with the new heads it's more drastic.

When I pull the tank I'll check the wiring.

 

I also had a trip ruined by a split hose connecting the pump to the sending unit. It bled off too much to hold sufficient psi, but would crank and idle sorta ok, but erratic, going up and down. But you couldn't even see the split till you pinched it just right, very easy to miss.

 

Is that a hose in the tank?

 

Yes, it's about 1.5" long and bridges between the pump outlet and the steel uplift tube that goes out the top of what is typically called the sending unit. It may look like a regular high pressure fuel line, or it may look like a spongy sort of thick walled rubber line, depending on the brand of pump. New pumps always come with a new short piece of hose for that purpose.

 

My book says to clamp off the return line and run the pump and if I get the higher pressure then it's the regulator. I'll go check that too!

 

i was of opinion if reg goes it spits gas out of spring retainer on TB? i blew two reg gaskets so that was my experience. dont think the seat ever fails?

 

Got a new pump in there... no pressure drop in neutral and it reads 12psi now. STILL LEAN POPS on acceleration, but it's better. ALL blms I've got 125 area now.

https://www.thirdgen.org/techbb2/sho...hreadid=256268

That says I've got 45lb/hr injectors like I thought. I have 55's coming.

 

That chart is a little off, the correct ratings are on Turbo City's page.
I actually had a pair of 350 injectors flowed and they are 61 lbs/hr, 305s are 55 lbs/hr, 4.3s are 45 lb/hr, 2.8 are 33 lbs/hr, and Cop/Van 350 injectors are 68 lbs/hr.

What pump did you end up putting in it?

 

Just the TPI pump. Money's tight because of the holidays, and the tank is cake it pull in this thing.

Turbo City's page looks like they tell you what they flow after they fix em up. Grumpy posted a similar list to the one I did, the only difference being the 4.3L Yellow/blue and the 2.8 black/white were not filled in. The rest were the same.

The Orange/Black one's I bought claim to be 55lb/hr. Which are 5.7L Truck injectors.

 

They are the 61#/hr injectors. Decent too, can up the fuel pressure for more flow.

The '747 has decent AE routines. Look for the table of TPS% lag filter values, can extend the duration of delta TPS% AE by lowering the value. I believe the table is at $31E

RBob.

 

Alrighty. Found the table!

Got my fuel pressure up to 15psi, wont go any higher without a spring or something. Was using a 7747mine.xdf, and decided to try importing the ecu type in, and it has more tables. Must have a weird mod xdf before.

Got the lag filters, also have the AE vs Coolant temp. Which should help give more AE also. I've tripled the AE in the AE vs Delta TPS and it still pops and doesn't get enough fuel.

Injectors should be on their way.

Weird how off different threads and such are about TBI injector color flow. Looks like Grumpy's post from DIY-EFI was wrong since it said the 5.7 orange blacks were 55lb/hr.

Are the 305 injectors indeed larger than the 4.3L ones?

If so my buddy Dewey316 on here needs some larger ones for his 305... and we might be able to swap. I'll use his 5.0 ones and he gets the 350 ones I just got.

 

Too bad you weren't around ~8 years ago to post better info..

Do you know at one time, it wasn't even common knowledge that there was even a color code?.


I'll let you figure out the answer to your guestion, gads, I'd just hate being wrong again.

 

Aww man, I wasn't meaning to make an offense. I look to you and Rbob and Prevost and such as good information. After all there is so much information about these things; how do you know what's fact aside from what someone is talking out of their rear?

So I was going on your previously posted information.

 

How does the Min/Max Asnych BPW work? I found a post with Monte saying he changed his to the 454. Is this a limitation, or a calculated figure? How does it work?

Thanks!

 

Have you looked at the 747fuel.txt file?
It's on DIY. Not sure if it got posted on Moates.
I hope that answers your question.
I haven't looked at that file in at least a year.
I need to find some time to go over old stuff again.

 

Well to sum up my swap and tuning:

~Vortec heads rebuilt, placed on an '89 4.3L TBI
~Edelbrock Vortec manifold with Holley TBI adapter plate.
~Lots of odds and ends.
~New fuel line because with the 4bbl/TBI adapter it kinks the feed line too much.
~Fought crossed plug wires for a week. :banghead:
~8062ECM died
~Installed 7747 ECM
~Made fuel pressure regulator adjustable, only got 8psi out of it.
~Checked pressure in driveway, reved engine, dropped to 4psi (No wonder it was gutless with the old heads)
~New TPI Fuel Pump. 12psi all the time! WOOT
~After AE runs out, I'm lean. Tip in, AFR hits 12:1, then leans out. 15-16 sometimes 17:1 and pops. If I add more AE, its too rich on tip in and bogs. BLMS are 130-140 in the 50+KPA cells.
~My VE1 Table is as high as it can go in the high map ALL RPM. VE2 is at like 40. I should be getting much more fuel.
~Rig is gutless uphill, hits 100KPA without being in power enrichment (set at 45), and goes lean.
~Bought 5.7L injectors from ebay $30. Had them flowed and cleaned $50. Set my BPWC to 135 instead of stock 181. SUPER lean. Set it to 190 and it runs the same as before. $80 spend on the same injectors. That guy is getting bad feedback.
~Injectors/pressure can't be too small/low because WOT I get 12.3:1 The whole time up to around 5200 when it's shifted.
~Now planning a quadjet, 229dizzy, and AFRP. I'm done. This has been a nightmare.
~All AFR raedings done with a wide band. Cruise and Idle reads 14.7 in closed loop, so the Narrow band O2 seems to be doing it's job.
~Spark is factory, also tried a vortec timing table, and taking timing out, and advancing.... didn't make any improvements really. Map seems to read like it should. Even if it's reading a false low vacuum (high kpa reading) it should be adding a BUNCH of fuel, and the WB says I'm lean, and I lean backfire through the TBI....

Anyone have ideas? When do you put the final nail in the coffin?

 

Is this in closed loop? If so that rich of AE will drive the INTegrator down. The engine will then lean out as the AE tapers off.

The biggest issue is lack of data logging. Can't tell what anything is doing.


What are the numbers and/or color codes on the injectors you are using?

RBob.

 

This is in closed loop yes. Come to think of it, in open loop it does do better in the colder temps. As it approaches normal op, it tends to lean out a bit though.

I can try to log, but the real time logging isn't quite out yet

Yellow/Blue (no color physically on mine)
GM 5235203*RPD / 6209
Those are the original ones.

I picked up ones that claimed to be Orange/black 5.7L ones. Flowed and cleaned them. See this thread about those Numbered GM 5235132*RPD 1075 GM.

Running at the same BPWC egr off in the xdf, I don't get the blms to come down any. I can go log with winaldl for an acceleration, and an uphill.... and log with the innovative and post them if that will help. I can post my bin too.

Thanks Rbob, didn't realize too rich AE will cause it to lean out on the end. I always thought 12:1-12.8:1 was ideal for tip in.

 

consider increasing fuel pressure? i am seeing lean WOT A/F(13.1-13.3) so in spring will bump 2.5 lbs and reapproach my VE tables.

consider involking PE earlier to help out the AE? if AE times out too soon(lean) the PE may transition to a 12.5 A/F. i am running 50% TPS for PE in last burn.

not sure if changing BPW is wise. you may need 80 lbs inj's. changing BPW may skew other areas. it was once said fooling ECU not a good idea.

 

Shouldn't need to increase fuel pressure, since I get plenty of fuel WOT. Unless the pumpshot used more fuel than that?

My PE comes in at 45%.

I was always lead to believe you must change the BPWC to match your injector sizing, and compensate so with increased fuel pressure?

 

my error did not read carefully. your 12.3 WOT is good.

you stated going uphill not in PE you go lean. i believe AE-MAP values could be looked at. i see similar issues with my set up. i think fuel sometime falls out of atomization due to high MAP resulting at moderate RPMS. never an issue at mid RPMS.


again did not see your PE is set for 45%. OK in my book.

BPW is a factor of cid -inj size - fuel pressure. i chose to set per the formula and do not deviate.

i hear it is possible to adjust the lenght of time AE-TPS is in effect. i think it was AE delta TPS or similar. i think it takes the same volume of fuel and spreads it out over time. that tells me if you adjust it (delta) you may want to add more AE TPS to balance it out. not too sure on this as i dont have in my tunercat program and have yet to use tunerpro rt 4.0 other than for datalogging. correct me if error.

my AE values are not that great since i have larger injectors and 17.5 FP. you have smaller injs and may benefit from greater FP. if you up FP you will up AE result from what i understand. if that helps your AE then you car reduce your commanded PE a tad.

it took me a while experimenting with all those tables and net results.

 

Burned probably 120 chips since the heads went on. I set the BPWC to 135 per formula based on the assumption of 61#/hr injectors that I bought. I've set the TPS AE coef lag filter from 145 I believe was stock, down to 70 now, and it hasn't helped much.