prscarf

ok gents this is the problem:
the blms are tuned and the truck runs great with the combo i have below. it has the lower curve tuned for somtime but when i go wot this is when the engine begins to loose power and start missing and sputtering. i thought it was because of the stock fuel pumps so i finally brokedown and purchased two walbro fuel pumps 255. these babies can pump the fuel. i adjusted the pressure to 15psi on the tbi. i still have the same problem with the missing at about 3600rpm and up. my feel is the engine is leaning out, the o2 count drops below 500mv and if i backoff the throttle abit it stops. with the alum heads, single plane this unit is getting too much air and not enough fuel imo. could the 454tbi just not have the capacity to feed this combination? i even checked my spark curve which has 22deg advance at 4000rpm 100kpa. i even dropped the woth afr to 10 at this rpm, no change. even maxed the fuel to 100 on the fuel curve at lower right corner of the ve curve, and nothing changes. injector constant is 120. i am lost with this, like i said the engine wants more fuel at the top ends. at the lower rpms is runs great with nice response. should i change fuel pressure and to what. the cam is degreed in to 6deg advanced for max torque. could this be causing this? i have not done a plug cut but from what i remember with the old fuel pumps it was running lean at wot. the old pumps had 12psi. getting back to the cam i don't think the advance is causing this because it doesnt happen when i rev to 4000 with no load (vehicle is parked). it has something to do with load. really believe it is a fuel problem.

i attached a screen shot of the ve, spark, wot afr.

91 chevy 4x4 sbc 383 stroker, 64cc 23deg trickflow alum.heads c/w weiand xcelerator single plane, adapter, cam is an extreme 4x4 comp. Cam. 12-235-2 grind ( .447/.462 lift, duration 210 218 lift @50, 111 lobe separation) . unit has hypr. Flattop floating pistons, eagle cast crank, 5.7eagle rods, bal.to 0.5grams, 10.2:1 comp. Headers c/w 2.5” flowmaster exhaust. 16147060 pcm, $85def
454tbi 80lbinjectors

1MEAN92RS

Um, I can't see the tables... they're really small. Could you upload a larger version of those? We might be able to offer some assistance then.

prscarf

top is the spark, below this is the ve, on right is wot afr

Brent

iTrader: (1)

Turn the FP up and see what happens. I'd bet your gonna need 20psi or more.

Also be aware that if you can run the injectors static depending on you BPW and WOT AFR's. They won't be metering fuel accurately at this point and that may be part of the problem. If this is the case then raising the FP might not give the results it should if the injectors were running 85% or less.

Just for the sake of disscussion I conservatively estimate your engine should make 385hp. 1hp/cuin is a reasonable starting point IMHO.

385hp @ .5 BSFC and 85% DC requires 2 113pph injectors

80pph injectors rated @ 10psi will support approx 272hp @ .5 BSFC and 85% DC

80pph units @ 15psi will support approx 333hp @ .5 BSFC and 85% DC

To get 113pph from your injectors you will need to raise the pressure to 20psi.

Keep in mind these are rough numbers and just a guide to get you close.

prscarf

what do you mean by "Also be aware that if you can run the injectors static depending on you BPW"

also can the injectors take 20psi and what do you think my bpw constant should be?

thanks for your help Brent

Brent

iTrader: (1)

Static means 100% duty cycle. If you raise the BPW too high or lower the WOT AFR table too low (numerically) the ECM will keep the injectors on constantly at WOT higher rpm. Injectors like a maximum of 85-90% DC depending on who you ask.

I don't know if your scan tool reports injector PW, but if it does you can calculate if you are at 100% DC. If not, you can buy an automotive DVOM that reports DC. Sears has 'em.

The only reason you would have this situation is if you don't have enough fuel availible at the injector. (insufficient pressure in this case)

Leave the BPW alone for now. Raise the FP in small increments and you should notice an improvement. Test it all the way to 20-25psi. It should get really rich at some point.

If you have the GM 17112560 injectors, they have been tested to around 60-70 psi by a GMECM member.


PS: Two WB255's?! Thats enough pump for 900hp! Do you have dual tanks?

PSS: Do you have any WOT Diacom/Datamaster/etc scans that we can look at?

1MEAN92RS

yeah, crank up that fuel pressure... you should see some help from that right off the bat. I think what Brent means is that the fuel injector can stay open constantly at WOT??? and if they are doing that already, then you might not see the gains you would expect from an increase in FP.

prscarf

well i cranked up the fuel pressure to 20psi but the oem modified regulator is not working at the pressure properly, it just will not maintain it after idle. when you step on the peddle it drops and i know its not the pumps, and yes i have dual tanks. i either have to use a larger spring or and summit regulator, i have the dam thing almost screwed in the entire distance and it is way to sensative. i do use a scantool which is datamaster and my laptop but i don't have it at the moment. from what i remember my injectors never went to 100% at wot. i have to put the scanner back on the engine and make a run.

NotDadsW41

Sounds like you could use one of the springs from the vAFPR.

They are quite a bit stiffer than the stock L03 or L05 spring.

prscarf

i had enough of removing and reinstalling the injector pod top to adjust the oe regulator. i am going to block the return line, leave the oe regulator at the 15psi present and run the feed and return to a new mallory 3port regulator. i can then adjust much more easier.

DM91RS

Check out the thread on 3- 21- 02 DIY AFPR.....it shows how to make the stock unit adjustable without removing it

kdrolt

This won't help solve your problem(s) but your VE table reaches around 93% at 2400 rpm... which is where the engine used to make peak torque with the stock engine and cam. With your engine and 210/218 degree cam, it's more likely that you reach max VE near 3500-4000 rpm... so the 100% load column should be modified to reflect that. And that means the whole table needs some tweaking. IMO.

Your spark advance table vs load vs rpm also seems a little unsmooth. Again IMO.

BTW I agree with Brent's math: unless you raise the FP a lot, those injectors will never provide enough fuel to that engine/cam combo. Larger injectors will help, but you will still need to tweak the fuel cal, AND probably the fuel pressure too.

Also, have you checked the ECT to make sure that's working properly? The ECT and MAP sensors are the two key sensors used by the TBI system, and if one/both are faulty, you will get lousy performance.

It also occurs to me that, without knowing how you've plumbed the fuel system (with two bigboy Walbro fuel pumps) and without knowing what the fuel feed/return sizes are, that the FPR may not be doing all that well in regulating. i.e. it might be overwhelmed and not giving you the fuel pressure you think you are getting. Do you have a means of seeing the fuel pressure from the driver's seat?

HTH. Pls keep us posted. - Ken

prscarf

i do have a fuel gauge but i cannot run it into the truck, i am going to tape it to the windshield. as for the spark curve what part don't you like, am i not advancing the curve enough at higher rpms and if so what should be max advance at 100kpa 4000-4400rpm.

fast_broker

iTrader: (1)

The guys above are right. I am not sure what size injectors you are running but you'll have to crank up the FP a lot to get them to work with that motor...

Running a FP gage while driving might not tell you much at all. It's the injector size that is limited, not the fuel delivery system. Even at 100DC, those pumps will keep up with the injector demand but the injector max flow cannot keep up with built 383 demand.

Here's what I would do: I would raise the FP to 20psi or so, then, if O2 readings STILL show lean at high rpm/loads, tweak the higher rpm higher MAP FUEL tables RICHER to get good operation and power at WOT. THEN, you go back and tweak the rest of the FUEL table LOWER, as a result of the too high a fuel pressure for the low-load areas... Add some spark, as well, similar to a mellow HEI curve, to get started. That will REALLY wake up the motor... Here's an example, may want to lessen the higher rpm/high-load spark AND the 30MAP spark numbers, as this is for Al head/big cam taht idles at 800rpm:

EDIT: this is for NO EGR operation, no EGR spark adder, no PE spark adder... ie, this table is the ONLY spark table the engine will see... VERY IMPORTANT not to burn this table into a stock prom without other appropriate changes.

Vacum 21.1 19.6 18.1 16.6 15.1 13.6 12.1 10.6 9.0 7.5 6.0 4.5 3.0 1.5 0.0
RPM 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
400 28 28 28 28 28 28 28 25 22 19 16 16 16 16 16
600 28 28 28 28 28 28 28 25 22 19 16 16 16 16 16
800 28 28 28 28 28 28 28 25 22 19 16 16 16 16 16
1000 29 29 29 29 29 29 29 26 23 20 17 17 17 17 17
1200 31 31 31 31 31 31 31 28 25 22 19 19 19 19 19
1400 32 32 32 32 32 32 32 29 26 23 20 20 20 20 20
1600 34 34 34 34 34 34 34 31 28 25 22 22 22 22 22
1800 35 35 35 35 35 35 35 32 29 26 23 23 23 23 23
2000 37 37 37 37 37 37 37 34 31 28 25 25 25 25 25
2200 38 38 38 38 38 38 38 35 32 29 26 26 26 26 26
2400 39 39 39 39 39 39 39 36 33 30 27 27 27 27 27
2800 42 42 42 42 42 42 42 39 36 33 30 30 30 30 30
3200 45 45 45 45 45 45 45 42 39 36 33 33 33 33 33
3600 48 48 48 48 48 48 48 45 42 39 36 36 36 36 36

prscarf

fb, you actually run this timing without knock? man this seems like alot.

prscarf

something else is troubling me about this insuff. fuel problem, why not just increase the bpw constant to say the 454 stock bin (142) instead of trying to compensate with fuel pressure. wouldn't this feed the engine at wot. also, this tbi was from a bigblock chevy and it fed all these cubes. i know my engine breaths alot better and at different places but i would think this would feed this sbc 383.

fb, i will try you spark curve and i don't have the egr or pe or any other spark added into my prom.

Brent

iTrader: (1)

No it won't feed the engine. The injectors are already turned on constantly when at WOT. They can't stay on any longer than that, so no more fuel is going to be delivered.

Look at it this way, if the injector is on the entire time it takes for one 4 stroke cycle (2 crank revolutions) to happen, where are you gonna get more time from?

Besides you need the increased pressure to make the injectors flow the amount of fuel required by your engine. Thats a basic hydraulic principle (flow rate vs pressure).

How about those WOT Datamaster scans? They should shead some light on things.


IMHO, just slapping his timing curve into your BIN is quite risky. You're are better off testing YOUR engine to see what it wants.

Keep in mind he is using the 747 ecm and the numbers may calc differently than yours. IE what the table says doesn't nesssesariyl mean thats what the final advance is.

prscarf

i understand about the injectors. as for the timing, my base is set at "0", and all other timing is turned off. so, it is like fb says "pure curve no additions" . mine has always been pure with no other additions other than cool compenstion spark at startup.

what i really like to know is when someone talks total advance is this the highest advance in the spark table or just at wot.

also what should the timing be at wot, at say 4500, 100kpa. i though my curve was in the ball park. also, i have to get my laptop to run a scan which is on a pce of company equipment at the moment so i have to wait.

JPrevost

Just like everybody else has pointed out...your VE table doesn't look right. What is your VE #2 table? Remember that the table 1 and 2 are added and shouldn't total more than 100, if it does it's ignored and thought to just be 100.
I would crank the fuel pressure up a LOT and mess with the VE table, set the BPW to something like 130 and just adjust the VE tables. Drive in drive, try to avoid overdrive. You can also just try and adjust the AFR to an even lower number to verify that the car is running lean. What is your pump shot tables looking like? Would you post the bin file here so I can look at everything else.
I was having the same problems when the car was running lean, it just wouldn't pull beyond a mid range rpm and just got flat sometimes backfiring through the intake when you let off and quickly go back on the throttle.

prscarf

mine is a pcm and i only have one ve table and thats it. you need the 85def file to read my bin. it is not 747ecm. i really cannot do anthing til i get the mallory 3port reg. or a larger spring in the stock regulator. the fuel curve can be tweeked at the wot position to 100 but thats it. i have never really race the truck at wot to much and via reason for the wot problem post. i had pump shots that would would make a lawn sprinkler look like a fire hose and i think it all stems down to what the boys have been telling me "fuel pressure". it just got too much air in one shot, damn engine is breathing more than i can feed it.

fast_broker

iTrader: (1)

The curve I posted is essentially nothing more than a tabular representation of a moderately aggressive HEI curve... Works fine for me with Al heads.

What size injectors are you running in the 383? What pph???????

prscarf

80pph from a 454tbi. i did put your curve in and things seem fine, cannont hear any knock but have to scan to see. i have not stood on the engine yet.

JPrevost

You won't be able to hear knock. The ecm will catch the slightest hint of knock from the knock sensor and retard the timing before it becomes audible to human ears. If you're that bionic women then maybe... .

prscarf

ok gents, hear is a scan at wot for short run. notice the knock count (ouch!!!), 02 is rich, injector duty cycle never gets over 45. need your thoughts. i am going to post the other wot short run after this so look at this screen shot.

note: the o2 never drops below 850, also the red vertical line is where the data coms from on the chart.

prscarf

2nd point of chart, see the vertical red line has moved to the right. how do i increase the injector duty cycle? the fuel pressure is at 15psi.

fast_broker

iTrader: (1)

IMO:

Your fuel table is too lean. So, when at WOT, like your pix of scan tool shows, your BLM and INT are locked at 128. This FIXES your ECU to run at your table values, which I argue are TOO LEAN!

ie, You are encountering LEAN KNOCK at WOT that will never be cured unless you up the FP and/or up the BPW at WOT to make the motor run at 13AFR or less! The DUTY CYCLE shown has nothing to do with feedback of rich or lean at WOT,as the BLM's and INT are locked at 128. AS such, your BPW value used is a default from your tables, which are lean!!! before you ran my curve, I hope you turned your EGR advance OFF (0 degrees in entire table and/or disabled EGR!!!) and turned your PE advance off (0 degrees in entire table)!!! If not STOP DRIVING THE CAR NOW and fix it...

Comments?

prscarf

yes all are turn off many moons ago. i ordered a new mallory 4309 regulator which will give me the fp i need. as you can see i didn't push things. i even tryed to put a different spring for another 454tbi and i got to 17psi but thats it. will keep you posted on my ventures. how can you tell from the scan that i am running lean other than the spark knock from the fuel curve you gave me?

Brent

iTrader: (1)

You can't tell from the scan that you are running lean. Its a guess based on the symptoms and specs you report.

The only way to tell if you are lean is:

A) A WBO2 sensor. This will show gross deviations from the AFR's where NA engines usually run. The stock O2 volts mean nothing.

B) Performance testing. GTech/ Vericom / Dragstrip (MPH)/ Dyno
If you increase fuel delivery and performance increases, you are lean.


First thing to do is go back to your previous Spark Table values. You have a fueling issue, so you don't want to be changing two areas at one time. Take care of the fueling problem first.

I wouldn't bother working the fuel tables or BPW until you have the new FPR installed because any changes you make will have to be redone.

After you have the new FPR installed and the pressure is set to 25 psi, see how it runs at WOT. If the missing dissappears you are on the right track. Take some performance measurements for a baseline. Without measurements you are wasting your time.

Now its just a matter of juggling the VE table, WOT AFR and BPW so that you have the right amount of fuel. If the VE table is maxed at 100, Duty Cycle is under 90% and you are still lean, the BPW needs to be raised or the WOT AFR table needs to be lowered. Since you are already at 10.5 on the WOT AFR I'd raise the BPW first.

You want to keep an eye on the DC at 5000+ RPM's and make sure it stays under %90. Optimally you want just enough FP that the injectors have to run around %85 at peak HP. This will provide you with enough dynamic range to keep the injectors stable at idle, low speed and WOT.

prscarf

thanks Brent and fb for you input. i will get back to this post once i get the fuel regulator installed.

prscarf

Ok fellas, don’t buy the 5port mallory 4209 regulator thinking you can adjust the dam thing from 3-50psi, not going to happen if you order one from summit or jegs (eventhough the catalog says 3-50). Mallory stopped putting the extra springs into the purchase. I just happen to find one a friend. I can now adjust my new regulator to 20-20 psi.

Now to update on my 383, at 20-25psi rich rich rich so rich it smoking rich. It is so rich I can see unburned fuel when reving it. My pump shots are not much different than a 454 pump shot bin. When drive it and get on the throttle what a slug and knocks with all this fuel to much spark and fuel, there is no way I can run fb fuel curve. this is pure curve, no pe added, no initial, base at zero with tlight. I did change the fuel curve towards the 3-4000 range and Did plug cuts and yes they were black. Even the blm is at below 100 to 116 across the entire curve. Wot afr are all 11.7 –11.5. I changed my fuel pressure back to 17 and it is definitely more responsive during wot runs than before. O2 never drops below 870 at wot runs and bpw is at 113. I cannot for the life of me get my injectors to have a duty cycle of 80% ever, even at 5000rpm in drive at wot 47% is the highest. Even if I drop the bpw down to 102 this doesn’t change, why? Can someone explain what the max. async bpw should be? Or what it means, doesn’t this limit the injector duty cycle. I cannot change this value on my chip with tunercat so I don’t know if this is limiting my injectors. any thoughts gentlemen? what changes the duty cycle?

Brent

iTrader: (1)

This should be no surprise to you. Raising the FP will make the entire range richer. You will have to rework the idle and cruise portions of the VE table.

It sounds like you are changing too many things at one time. I would go back to the BIN you were using before putting in Fastbroker's spark values.

1. Raise the FP back to 20psi and set the BPW to 128 (because your Duty cycle is so low).

2. Make a 30% reduction in the idle and cruise areas (20-60KPA x 0-3600rpm) of the VE table and check the BLMs. I wouldn't spend too much time getting them perfect yet because you may have to raise FP again depending on WOT. Just rough them in so the exhaust isn't burning your eyes.

3. Grab out your GTech or other performance testing device and get a WOT baseline. 3 runs should make for a nice average. Record you runs on the Datamaster. If you don't have any method for performance testing, go get one. A shop with a chassis dyno and WB02 would be a good starting point. Then you would know immediately if WOT is Lean or Rich. This will knock a bunch of time off your testing.

4. Now you have to try to increase performance. Start by richening things up in the prom. Use with the VE table and WOT AFR table. Test performance. Repeat until its running its fastest.

Dropping the BPW will decrease your duty cycle. Thats why I recomended raising the BPW to 128.

Async PW as reported by your scantool is injector on time. Async mode is used for pumpshot and some other times. I wouldn't worry about it. Sync PW is the one listed above Async and is the one Duty cycle is derived from. You change Duty Cycle by raising or lowering the VE table, WOT AFR table and the BPW constant.

prscarf

brent,
i will do what you say, below is the new fuel curve i have in my bin before any altering. i did increase the upper part of the curve. as for the spark i reduce wot max to 30deg.

prscarf

brent, did what you said and droped the curve 30% upto 60kpa, increase the fp to 20-21. this is what happened, the engine was suprisingly close to 128 on cruise (bpw set to 128), and when i went into wot major rich, truck felt like someone was pouring gas down the throtte of the tbi what a slug, and yes i did a plug cut, black black black (i know it is running rich at wot). i then dropped the fuel pressure back to 17-18 put my 102bpw chip in and the above fuel curve i just posted above this post and what a difference the truck responded like i was at nhra tracks all the way to 5000rpm. i have no idea how you guys can dump so much fuel down your engines, i not being critical but just trying to understand why and i do appreciate your help.

my next question is it better to have a 140bpw constant and reduce the fuel curve to match the 128blm so you injector duty cycle is running in a more optimal condition, or leave the bpw constant low and increase the fuel table to match 128 which keeps the inj dc low?

i did check my injectors and they are the black/blue 80lb/hr and the # does match the codes of these injectors.

Brent

iTrader: (1)

Looks like I over estimated the engines HP. That would explain why 17psi works better than 20psi.

Either method results in the same final injector on time (PW) and duty cycle. Only when you change FP does the duty cycle have to change.

For example: at 2000 rpms x 60kpa engine XYZ wants 2.5msec PW to maintain 14.7:1 AFR. Now if we raise the FP 5 psi the injector only has to stay on for 2.0msec to maintain 14.7:1.

Personally I would have left the BPW constant stock. I would have lowered it only if I couldn't lower the VE table far enough to get it to idle at 128BLM.