Yup, that's kindof what I said above...

 

Ah, nice thinking. Thanks, i guess i wasn't sure what the aim of this activity would be Think i should do that at some point on my L03, i know there's got to be a gremlin somewhere with the timing setting there.
But can you really reach in the back there with the timing gun and actually see anything?

 

Ive experienced this type of misalignment on 90s Vortec motors. On these Vortecs, the distributor is only a secondary ignition switch and contains no primary ignition components. The cam sensor is only a diagnostic sensor to measure cam crank misalignment. On these motors turning the distributor has no affect on ignition timing. However, it is possible to put the cap and rotor enough out of phase with the PMC's primary ignition pulses that you will get misfires. Of course youll also throw a code(32 IIRC).

On HEI dists, whether internal coil or external coil, the primary ignition drive(pole peice and timing core) and secondary ignition switch(cap and rotor), are mechanically fixed in synch with each other. Unless the distributor is damaged so that the timing core has rotated on the shaft, or somehow the rotor or cap are misinstalled, there is really no way the cap and rotor can be out of phase.

Remember, the timing on these cars(any HEI car after 82) is ECM controlled(EST) and trying to determine proper distributor phase by watching the alignment of the cap and rotor with the engine running is likely to be an exercise in frustration.

 

The interesting thing about those is that they allow something like +/- 22.5 degrees either side of TDC for the distributor placement. The PCM will just correct for it by adjusting the timing of the firing pulses to the coil. Too far, and the PCM will have trouble adjusting for it as the hardware can only do so much.

As far as HEIs, Ive never run into one that had a rotor phasing problem. The only issue Ive ever heard of is the center reluctor thats pressed on the shaft coming loose and moving about, which will really throw off the timing. In that case, its easy to spot as you can just put the dist. to TDC. The problem will show up as the "star" points on the reluctor being misaligned with the ones on the outer magnet with the rotor pointing at the #1 position.

 

I just fixed one of those for a freind, it was only off one tooth and PCM could not compensate. Is one tooth 22.5 degrees? Or maybe some are differant...

 

Well the DUI large cap HEI is in and (knocking on pressed wood here) it seems to have done the trick. Right away just idling I could tell it was a lot lot better. Drove it and the fuel trims actually started to make sense and really were pretty close. It made it to 5300 before it leaned out and started to misfire but thats not bad. Added about 15% more fuel where it had gone lean and ran it up to 5700 today and two times in the process it sort of hesitated for an instance but it was still a little lean yet but it ran strong otherwise. I thought it was kind of funny to see 87 kpa at 5700 rpms. I really need to get a 4 inch intake setup on it bad. Also I haven't totally ruled out lifter collapse either on the slight hesitation it had. I'm going to run the valves again and make sure I've got the lifters within .010 of being collapsed and re evaluate. Overall though its an entirely different truck and a blast to drive.

 

Still doing OK?

 

Not completely. Overall it runs much better but the loss of power is still there about 4000 rpms and sometimes it still misfires some. After a lot of thought and digging in the chronicles I realized something. Back when I first put the LT4 hot cam and roller lifters in it I was still running a much heavier 15w 40 mystic oil compared to the Mobil 1 5W 30 I'm using now. Initially it ran good even for having a small dual plane intake on it. It would twist up to 5000+ no problem even though the intake was causing a light restriction to it on the topend. At that point I ran a Harley F150 truck and was able to stay with it and at that point there was no loss of power per say or breaking up. Then at some point along the way I decided to put Mobil 1 in it since I had been using it on my 99 Silverado. At some point between then and not too long after that I began having issues. The lifters I'm using came out of a 200,000+ mile engine so they are not new by any means. After doing a lot of google searching on lifter collapse I'm starting to wonder if that hasn't been the problem all along. If I get a chance this weekend I'm going to try a valve adjustment method David Vizard has touched on before. Basically run the rocker down until the lifter plunger is within .010 of being fully collapsed and run it. Now my thoughts on this are for one I will need to use a dial indicator to make sure I'm getting it right and that there is no chance of holding a valve open and two that this is more than likely going to change my rocker/valve geometry quite a bit as well. For the most part though I want to try this and see if it makes it better or not. If it does I know I'm on the right track and its either going to be getting new lifters or maybe the easy fix and just run 20w 50 oil in it and either not drive it in the winter of make damn sure to get it warm up first. If not that I don't know what the problem is. At this point I know its not tune or ignition related.

 

Ive experienced lifer problems with the thinner oils with my current Morels. They tend to bleed down at temperature with anything less than 5W-40, and I get a cyclitic ticking thats RPM dependant. Ive never had it with GM lifters, tho. Those seem to bleed down much more slowly than the aftermarket units.

Id be hesitant on running the plunger all the way down. If you do get valve float, it could possibly cause some major issues. At the very least, youd definitely know your valves are floating! The proper adjustment for the majority of hydrolic lifters is 1 full turn, or .040" of lash. I wouldnt take it much farther than that.

If you want to test the lifters to see if its ticking. While you have the hood open and your standing near the engine, rev the motor up to its redline in neutral and see if you hear any clatter. If you hear the lifters start to clatter at certain engine speeds, and your running the right ammount of lash, then its time for new ones.

 

Well, as a diagnostic measure, I installed a carb. Truck hauls azz and no rpm fluctuation at all. May try installing the CC distributor and see if that helps diagnose whether its ignition or fuel related.

 

Was talking to Chris (fast355) a couple nights ago and he started asking about the pulse width when it was acting up. I was running well into the 5s in the 4000+ range. I increased the fuel pressure to 40 psi and it cleared up pretty well until after 5000 rpms. I'm going to try 50 psi and see what happens. This is using 61# injectors.

 

Just be aware that your fuel pump may not be able to keep up that pressure at wot & high rpm I think most are limited to about 45psi for their flow rating. You can check the walbro 255's graphs @ http://www.diyautotune.com/catalog/w...ump-p-312.html the other walbro's are posted somewhere, I forget where.

My rat is freekin' thirsty at 5k & the walbro fell on it's face trying to keep 60psi on the 80lb injectors, ended up with this...
http://www.diyautotune.com/catalog/s...660#googlebase

it's noisy.

 

This is the one I'm using:

http://www.jayracing.com/index.php?m...&products_id=1

 

At 50 PSI, the walbro will flow around 300 PPH of fuel. That may or may not be enough. Also keep in mind that the type of regulator in use will effect how much you can deliver. If your using a stock TBI regulator, you can run into pressure fluctuations as they are somewhat restrictive inside.

 

I am using a stock pump for a 5.7 vortec truck 96 or 97 model when the pump motor itself was still replaceable. I know all about the stock regulator being very restrictive which is why I bypassed mine and went with an external only. Still haven't had a chance to try it at 50 psi just yet.

 

The restrictive nature of stock regulators will not be a factor in pressure loss situations.

Any constrictions in the long delivery line can be (tight bends, connections, transitions).

Remember the pumps are rated w/o any delivery line restriction or load.

The Bosch 044's (dual or staged) are a favorite of the 500-650hp crowd.
They are more realistically rated & reliable pumps.

Edit: Didn't mean for that to sound like the Walbros are unreliable, they have a good reputation also.

 

Its the opposite with TBI. The stock regulator return causes the pressure to be higher than the actual setpoint of the regulator with high flow pumps. This is due to the excessive pressure drop going thru the return side. You can set it for, say "35" at idle, when the regulator is actually only set for 25. When the fuel exits thru the injectors instead of the regulator under load, the excess pressure is relieved, and the fuel pressure drops down to whatever its truely set for, causing a lean condition.

 

Ummm ya...I see why you had a hard time tuning TBI.

 

If you ever take an injector pod apart and look at it you will see what he's talking about. Basically the pod was not intended to have much excess flow through it and very little flow overall for that matter. I took mine and cut the entire regulator housing off, enlarged all the passages I could to at least 5/16" and made the throttle body itself returnless and fed only from a metered fuel source from my external regulator and for the first time since it had anything but a stock pump and fuel system I actually have steady fuel pressure. Doing this drastically changed the amount of AE fuel it wanted because of the amount of pressure drop I was getting before was really messing with it and in fact I had always had this incurable lean bog if I floored it from a dead stop.

 

Did you mount this internal or external?

 

60 psi on 80 lb injectors!? what thirsty engine would gulp that in at 5krpm?

 

VA454, it's external.

ownor, it's a 480+hp RAT, the big pump is now running 52psi.

The point is the little pump could not maintain pressure.
At 60+psi idle setpoint, it had no ***** & fell on it's face.

For a while I had to compensate w/VE & BPC till the big pump fit in the budget (more Top Ramen, cheap hot dogs & beer).

This is w/ all -8 supply line, pod passages "massaged" for increased flow ect.

"If I ever"...get real RED I'm the guy finding the limits.

 

OK, I haven't read all 5 pages, so this might have been mentioned before...

Put an inductive pickup timing light on it, and set it where you can see it.
When it breaks up, is the light erratic ?
An inductive pickup works on the current in the plug wire, not the voltage, so no spark, no flash. Any spark, flash, no matter how weak.

Then, try closing the plug gap down, A LOT !
If it runs with a .020 gap but not with .060 then you KNOW it's weak ignition.
( performance aside, does it still miss ? )

 

My ride has stock distributor with 270K miles on it, at 4000k no misfires...
just lots of blue and red lights in back window
if its not what you just changed then perhaps its your
T-chain or Dist-Gear
valve Springs(floating)
push rods (deflecting)
hot spots on pistons/heads/valves

then to trouble shoot
change distributor
change ECM
then lastly LOL

 

Not sure that was real helpful in any respect...

 

Time for an update. Turns out the problem was the injectors going static. Apparently a wide band is utterly useless when injectors go static. As of now I'm running my stock 350 injectors which I thought were 61# but turns out could be only 55# at 50 psi. I've had to play with the injector offset to gain a little more fuel as well and I'm in async by 80 kpa. It now pulls through 1st decently up to 6000 but falls on its face going static into 2nd gear. Its not breaking up anywhere near like it was but its running pretty dang lean in the 14.5:1 range if not leaner. I tried not to push it, just enough to see its not breaking up like it was. The injectors that came with my 454 throttle body are the little 46# ones. I'm thinking I really need to get some 74 or maybe they are 75# 454 injectors. I was told to stay away from the 80# ones as they don't like high fuel pressure that well. I think the 454 injectors at about 35 psi should do and at least I will have room to grow when the time comes. I've been searching but can't seem to find anything set in stone on the exact part number for the injectors I'm looking for. All sorts of threads but the info seems inconclusive.

 

glad you found that one out man! i'm sure it's in the thread somewhere already but what's your calibration/tuning equipment? i hear ya on the injector info being hard to find or even contradictory sometimes.. maybe someone else can help you out here. but about the 80# injectors you mentioned, aren't they the ones rated 80 lb/hr at the higher psi rating (thinking 30 or something like the later model TBIs had)?

 

I am using tunerproRT, an Ostrich 2.0 and scannerpro.

I have no idea on the 80# injectors other than I was told to steer clear of them. I guess the 46# 454 injectors were actually rated at 90# at 46 psi.

I want to get injectors big enough to give me some adjustability. The plans are a stroker of some sort later on, maybe a 396 or even a 408 if the block permits and some very heavily ported vortec heads with big valves and the right cam and see where that leads me. I would like to get well into the 500 range NA so I want injectors that can support that as well as where I'm at now.

 

There's a vendor here that has 100 PPH injectors.

Also we are accumulating accurate information on TBI injectors here:
http://www.eagle-mark.com/Forums/viewtopic.php?f=9&t=94

 

Red, Rich was nice enough to get the right info posted in a jpeg you can save & distribute.

http://www.chevytalk.org/fusionbb/sh...hp?tid/260664/

It's also in his bowtiebreakers web library.

I made a injector PW/RPM/DC chart that might help you select an async transition rpm, it's in word & I could attach it to a e-mail.

eagle-mark posted the right injector info, but since started to monkey with it.

http://www.eagle-mark.com/Forums/viewtopic.php?f=9&t=94

The information that the 80pph are lazy/slow (this adds to necessary offset) was first posted here by Walt Sherwin from his own bench/oscilloscope testing years ago.

The 231's I've tested start to leak at a lower pressure then the 17084304's have, while this pressure is extreme (60+psi) it is important when looking for enough fuel to match the big TB airflow.

Finally NO vendor has proven to the satisfaction of this board that they can supply 90, let alone 100pph injectors. If they had, I would own them.

 

I would like a copy of this for myself. If you see fit I would also include it in our collection of documents.

How rude!

Absolutely no monkeying is going on with documentation of the TBI injector flow rates I received from a very reliable source (1.72afr). I have just added, next to the flow rates of the same part number injector that was serviced by an injector cleaning service. At this point it is just an experiment to see and show the importance of having flow matched injectors. At this point only one set of Big Block TBI injectors have been serviced and shown that such a cleaning service can equalize injectors to the same flow rate, which means one was clogged more than the other, not that a service can change or match a set of injectors, only that when cleaned they did flow more and one cleaned up more than the other. We also decided that there are to many varibles to prove the flow test performed on this machine is accurate as to the first test. Once all injector part numbers have been serviced we may have a benchmark to say that this method of cleaning service is 5% or 10% or whatever higher or lower then origanal testing. Or it may prove to be totally inaccurate, or, or, or. But at this time all it has proven is what we already know, which is you should always have your injectors serviced to see if they match!

I beleive RBob had a set and tested them?
If not please do tell what happened and who got them or how the test came out... just curious as I have an engine that was planning to use these on.

 

I would prefer RBob clarify his own data, but read post #44 of that thread & do the math yourself.
&
I don't want to be adding any offset I don't have to.

 

Yeah I suck and search but the only thing I found was quote But I thought they ended up at 100?

 

Sry man, I shoulda linked.

https://www.thirdgen.org/forums/tbi/...injectors.html

As a side note for y'all, the diy-efi.org server is back up, I had to re-bookmark it.

http://www.diy-efi.org/

 

I have done some reading and I believe the correct part number for the GM 91-93 454 injectors that were 74/75# per hour is 17084304 and the number has since changed to 17112560?

 

Here is what I have frim research done here.
17084304 - Black / Blue - 76pph - 7.4L / 454 - 91-93

 

Actually the same thing, 17112560 is the part # by the GM parts book or computer.

And 17084304*RPD is the number that appears on the assembly line installed part. Replacement injectors may be marked with a different three letter suffix ie.17084304*XXX

I guess you would call those Rochester part #'s. If you plug the Rochester # in to a GM lookup it spits out the GM #, parts are delivered with the Rochester # on them & GM # on the package. The GM # is never on the part.

Here is some cross reference assistance,

http://www.fuelinjector.citymaker.co...ester_TBI.html

 

Well I finally got some 74# injectors. IIRC the number was 57229 they are Borg Warners from Oreillys for a 91-93 454. Put them in, set the pressure at 40 psi and set the injector constant vs vacuum (VAFPR) table accordingly and went for a drive and it was the SAME damn thing. Long terms showing on the lean side overall and still misfiring. So I went back and changed the injector constant for 30 psi but left the actual pressure at 40 psi to trick the PCM and make it hold the injectors open longer and went for a drive and the fuel trims were much better. Actually it was as rich as 110 at low load but under WOT I was still going static somewhat. I am going to do the same thing only set the injector constant for 20 psi and raise the actual pressure to 50 psi and see what happens. That is going to be a boat load and a half of fuel but if it wants it its going to get it.

 

How much injector offset are you using?

I've bumped my table x 2.5 (to 990 usec @ 11.2-14.4 volts) with good results.

 

Still using the stock table for 61# injectors.

On the injector constant it seems to me like that is more of a setting to get the PCM on the same page as the injectors calibrated flow at stock pressure. To get more flow you would want to leave the injector constant alone and turn the pressure up or at least it sure seems that way.

 

The injector constant needs to match the actual flowrate of the injectors. Whatever they flow at the current pressure is what the injector constant should be. Otherwise, the engine will be way rich when you turn up the pressure.

 

I used to think that too but the more I thought about it the more I think it doesn't need to be so. Let me put it like this. Back in the day when it just had a throttle body spacer and headers and dual exhaust on it the pressure was upped with no other tuning to give it more fuel. The PCM didn't know about the pressure change, all it knew was more fuel was there and it took it away where needed and let it be where needed. Fast forward to now. If I were to set the BIN up to where the PCM knew I was running 74# injectors at 40 psi then to me that makes me think the PCM knows about the changes and will treat those 74# injectors at 40 psi as it would at 10 psi. At 40 psi and corrected for it would pulse them shorter and in turn flow less fuel. At 10 psi it would pulse them longer to produce the same amount of fuel. By telling the PCM I'm running the injectors at say 20 psi but in actually running them at say 50 psi I should get the same long pulse times but with the higher pressure therefor much higher flow. The extra flow can be controlled with the MAF table, thats not the problem. The problem is I need to open up the flood gates at WOT and thus far correcting for the injector size and pressure is not getting it done. Maybe my thinking is way off but it has worked so far. Right now I'm corrected for 30 psi and running 40 psi and that took the fuel trims from running in the 140s to 150s down to the 106-115 range.

Edit: Just got back from a drive and I did both just as I said with the PCM set for 20 psi and the actual pressure at 40 psi and I did take the injector offset table times 2.5 as mentioned above and the end result was a ton of extra fuel. Closed loop was able to get the lowend stuff down to where I could drive it but once I got on the road I was staying very rich and actually set a code 45 rich condition detected and the wideband was pretty much pegged rich the whole time. Time to dial it back some and see what happens.

 

More disappointment. I copied the injector offset vs battery voltage table from BHDF which is a 7.4 tbi bin into my bin and again ran it at actual 40 psi with the PCM injector constant set for 20 psi. Still plenty of fuel on part throttle stuff and this time at WOT it was showing plenty rich, into the 10s at times, but I was still going static. By 4000 rpms I was into the 5.00 range and breaking up. I'm at a loss.

 

Here is the answer as I did everything from dizzy to injectors to fuel pump. It's old wires going from the module plug on your dizzy to your computer. Run (4) new wires, splice them into the module plug, cut old ones off at plug saving space for the new wires. Run in a new plastic cable spool harness following the old wire harness into the computer. Slice them into wires on the computer. Just match up the wire colors, I used to know the computer cable numbers, but follow the colors. Do not remove old wires from the bundle, it may disturb other aged wiring. The slightest resistance caused by old age will effect the signal going to the computer and the engine will misfire, the tack will jump and give you every symptom of every other component but it's those wires.

 

Interesting. When I put the large cap HEI in it I did get a new connector pig tail and dug back into the harness quite a ways and soldered the new pig tail on and the wiring was pretty shabby. It may be worth the time to volt drop test those four wires as you say and see whats up. I could have corrosion growing in the firewall pass through connector for all I know.

 

Values are rounded to tenths, 100% is static.

------ DC in milliseconds
RPM. - 100%-85%-80%

3500 - 8.6 - 7.3 - 6.9
4000 - 7.5 - 6.4 - 6
4200 - 7.1 - 6.0 - 5.7
4400 - 6.8 - 5.8 - 5.4
4500 - 6.7 - 5.7 - 5.3
4700 - 6.4 - 5.4 - 5.1
4800 - 6.3 - 5.3 - 5
4900 - 6.1 - 5.2 - 4.9
5000 - 6.0 - 5.1 - 4.8
5200 - 5.8 - 4.9 - 4.6
5500 - 5.5 - 4.7 - 4.4
5700 - 5.3 - 4.5 - 4.2
5800 - 5.2 - 4.4 - 4.1
5900 - 5.1 - 4.3 - 4
6000 - 5.0 - 4.2 - 3.9
6200 - 4.8 - 4.1 - 3.8
6500 - 4.6 - 3.9 - 3.7
6700 - 4.5 - 3.8 - 3.6
6800 - 4.4 - 3.7 - 3.5

Switch to async over 80% DC.

 

It needs to match the ACTUAL flowrate of the injector. If it doesnt, the PCM wont compensate for the extra added fuel, and it will be pig rich. If the injectors flow 150 pph at 40 PSI, the injector constant should be set for 150 pph. The injector constant is used by the PCM to determine how long it needs to keep the injectors open for. In the final fuel calculation in my code, the PCM takes the mass of air in the cylinder calculated from the mass airflow along with the commanded AFR, and then divides it by the ammount of fuel the injector flows per second to get the time the injector needs to be open for. For example, say you have 100 pph injectors rated at 10 psi, and you turn them up to 20 psi, and their measured flowrate is 120 pph. If you leave the injector constant for injectors that flow 100 pph, the fueling will be 20% too rich.

DO NOT use the mass airflow table to compesate for it. The MAF table should be calibrated using the actual flowrate of your injectors at the pressure theyre being operated at. This way, if you change the pressure, all you have to do is change the injector constant, and the fueling will be exactly the same as before. The goal of raising the injector fuel pressure isnt to richen the engine, its to shorten the PWs at WOT to buy yourself more fuel delivery capacity.

Set the injector PW for what it should be for the flowrate at your current fuel pressure, and recalibrate the MAF table. This way, the PCM will be calculating the right PW for the mass of air entering the motor. The purpose of the mass airflow table is solely to provide a transfer function to convert the frequency input from the sensor to the measured airflow. If you change the table to adjust the fueling for other things like the injector flowrate, you no longer have an accurate indication of the airflow.

 

If the injector goes to 100% dutycycle, THATS IT. Maxing out the pulsewidth in the PCM will not provide any more fuel. The injectors are already being held fully open, and are giving you everything theyve got. Its possible that you can go the other way. Give the motor SO MUCH fuel that it begins misfiring from an excessive rich condition. This can show up as a false lean condition on the wideband because you have both a surplus of fuel with a surplus of oxygen in the exhaust, so there is no longer a large differential of oxygen across the substraight as there would be with a fully burned rich mixture. Remember that in an excessively rich mixture, its possible for the flame front to go out before it consumes all the fuel if theyre isnt enough oxygen. One key assumption with any oxygen sensor is that you have complete combustion. If thats violated at any time, the readings are useless.

 

I hate to say it as a former TBI user, but if your having this much trouble with the TBI, you might want to go to MPFI. I have a MAF code for that as well when using the TBI PCM. The code has a variable injector firing stratagy that dynamically manages the firing rate to optimize the dutycycle of the injector. This allows the use of larger injectors without the problems of short PW at idle. It also maximizes the firing time at WOT. You can get an edel victor-e intake, and just use the TBI at a regular TB. I had lots of issues as well due to all the difficulty in getting lots of fuel out of 2 injectors instead of 8.

 

Actually I'm going to give speed density a try again with my original BJYM code to see if its me, the an issue in the MAF code, or still something mechanical or electrical. There is an efan path that I need to finish putting in but other than that all transferable settings have been transferred and its just a matter of repinning a couple wires.

If I do anything different than TBI and I plan to, I am going to use something like a Megasquirt 2 or 3 and retain the original PCM to use as a TCM for the transmission.