Folks,

I've been struggling with an issue for a long time and want to see if any of the LS gurus have any thoughts on what is causing it. Bottom line is, the engine performs OK up to a point, then increasing boost results in the engine running richer and losing power. Firmly believe it's a weak ignition issue but haven't been able to solve it.

Here is some background and I apologize if I ramble but I feel the more info I provide, the better. Car is a 92 Fox that started out with a LQ long block with some budget rods and pistons, TU1 cam, unported 317s with Comp double springs and trunion upgrade, LS1 intake, T6 S480, MS3X, PTC, Glide and DRs. With 18.5psi and pump E85, it ran the number you see in my sig with a 1.32. I was pleased as that met my initial goal. Swapped out the LS1 intake for a ProFlo and ran it at the 1/8-mile track while the 1/4-mile track was under repair. Had a lousy 1.42 but it went 127.5mph. Went downhill from there as I tore up the thrust, crank and block and did it again to a SBE before I discovered the glide was putting 135+psi in the cooler/converter circuit. Never liked glides and went back to a TH400.

With the thrust issue fixed, I decided to duplicate Mark Frederich's setup and built a 402ci shortblock with a Summit block and Manley rotating assembly. Carried over everything else, including the heads, intake, coils, etc, added link-bar lifters and freshened up the turbo with a billet 85mm comp wheel. Don't know why I did it, but I swapped out the MS3X for a Holley HP EFI. Car has not come close to matching the original performance!! I've triple-checked the timing, done a leak down, swapped out the 581 coils for Pantera EFI upgraded 510C coils, replaced the coil sub harnesses, tried different plug wires, plug gaps, injectors, timing from 12-18*, boost from 16 to 20psi and it makes no difference. Best it ever ran with the Holley was 8.84 @ 154.5. Also, with the Holley, soon as you went off idle, it had a subtle misfire more pronounced when driving. Sent the ECM back to be checked and no one seem to able to pinpoint the problem.

I've seen discussions where others had somewhat similar issues and the go-to answer is to swap to IGN-1A coils. For me, that's about another $1,000, on top of the thousands already spent, for 8 coils, brackets, harness conversion and good plug wires. Another option was to sell all the Holley stuff and go back to my roots, MS3X and instead of spending another $1,000, put a $1,000 back in my pocket. Choice was easy. First startup and test drive with the MS and the annoying misfire was gone. First 10psi test hit felt good but I noticed in the datalog that at 8psi, the Inj DC shot up to 103% then suddenly back to normal as the boost got to 9psi. I run dual pumps, a Bosch 044 primary and turn on an AEM 380 with a KB BAP at 8.5psi and that was fine with the Holley but the 044 was out of fuel at 8psi with the MS. Hmm. First track session I started out with 13.5psi and it went 145mph and 2 passes later I was up to 16.8psi and it went 153.5, a nice 8.5mph pickup. Next time out I bumped it up another 1psi and it went to 154.4 but started going richer. With 19psi, it went 155.15 and running even richer. I planned to run alky and for the hell of it I adjusted the fuel table and turned it on knowing it wouldn't work, but was curious. It's a 20gph nozzle but I have the PWM set to 25% at turn-on and 40% at max boost/RPM, so not much. Engine fell on it's face and struggled to 145mph!!!!! When the engine is running good it has no problem getting to redline in a hurry, so I know its not valve float, lifters, weak springs, etc.

I know I've probably lost some folks but hopefully I still have some readers. I don't know what else I can do. There is always the IGN-1A coils option, but how do you explain Mark's car and many other quick LS cars running stock coils? The only other thing that changed when I went to the 402 was the cam sensor. Being a Gen IV block, I am running a 24x crank with a 1x cam sprocket and sensor and the Racetronix extension/adapter harness. I know GM had a transition year where they ran 24x crank with the 1x front cover sensor. I was told all the sensors are the same but also found out the 58x setup have 5V to the cam sensor instead of 12V. Could this have anything to with my issue?

Thanks for reading my true confessions and appreciate any feedback that can talk me off the ledge.

 

Are you running closed loop. What’s your commanded vs. actual a/f? Is your ecu setup for variable fuel pressure?

 

At this point, not running closed loop.

Commanded vs Actual AFR depended on what pass and whether I had the alky on or off. The last "good" pass with 16.8psi, I was commanding 11.6:1 (E70 on a gas scale) and the actual was within .2 richer. With 19psi, the actual AFR got as rich as 10.2:1. With the alky turned on, I was commanding 10.8:1 and the actual got down to 9.9:1.

Not sure what you mean by ecu setup for variable fuel pressure. It is a boost-referenced FPR and I log it and at no point was there any variance from base FP + boost.

 

I usually run closed loop and Its normal to be +or - .2 a/f from commanded. Meth will alway cause richer readings.
Not familiar with ms3, but Some ecu’s need to know if you’re running variable (boost referenced fpr) or fixed pressure.

 

Have you tried running batch fire VS sequential just to rule it out?
Coils grounded super well I take it?
Have you tried OEM coil wires VS the crazy aftermarket stuff?
Using resisted plugs? Current gap?
% of water/meth you sprayed?

 

Haven't tried batch, but that would certainly take the cam sensor out of the equation.

MS3X grounded to head as recommended. Engine is solid mounted but also has ground straps to the frame. Same setup from day 1.

BR7EF running out of the box gap (.025) but tried gapping them up and down.

I have a 20gph nozzle being controlled by the MS with a SSR. Turn-on point is 10psi and above 4,000RPMs with a PWM of 25% ramping to 40% at max RPM/boost, so not much. The problem starts at 16+psi even without the alky. Increasing boost or turning on the alky makes it worse.

 

Sorry. I've tried several plug wires, but currently using AC Delco 9748RR for the LS7 Z06.

 

What are your intake air temps, what makes you think it needs water/meth at that boost level. I,ve found that air/fuel bellow 11.3 at any point on e70-e85 acts as a rev limiter.

 

I get there are other issues at hand, but NGK lists the BR7's at .028 out of the box. I'd run .015 until you have it sorted.

Is it a harness you built? Does each coil pack group of 4 have a dedicated ground to the head?

I meant what percentage of water to meth? Running washer fluid? 50/50? Etc. Running straight washer fluid washes out spark in a hurry on my setup. I PWM a pump as well. with 2 12gph nozzles. Mine flowed a surprising amount at low DC's. This is the cheap 8000 series pump as well only 150psi or so max. I run 2 bottles of heat with one gallon of washer fluid. That's supposed to net 50/50. I can run higher DC's with a 50/50 mix without spark trouble.

Good luck, that's a bummer!

 

The alky (pure meth) is being used to keep the intake temps in checks. At this time of the year it's not bad, low-160s through the traps. With that small amount I tried, it dropped the IAT down to 119. Prior to this, I was injecting water pre-turbo through a 7gph nozzle and the IAT was low-140s.

It's a standard off-the-shelf MS harness with OEM coil harnesses on each bank. Keep in mind that this is the 1st time I've put meth in this engine and at that point, it was already losing power. Also, this is not a new problem. As for the plugs, I've tried down to .018 and it makes no difference.

Your point about grounding the ground pack grounds triggered a thought and I went back and looked at battery voltage in the datalog and it turns out on the 19psi runs, my battery voltage was down to 13.0V and on the 1st 13.5psi pass, it was 13.3V. I wonder if that voltage is too low to provide the spark energy I need with the increased load? Never noticed this before as on startup and cruising, my gauge shows 13.8V and never turned that on in the datalog display?

 

"Engine is solid mounted but also has ground straps to the frame. Same setup from day 1.".
Batt directly to engine, or thru the frame?
I think that there is an issue with a support system, [batt grounds, etc,] that is following 2 entirely different systems.
I'd suggest volt drop testing on both sides + & -. Also check all electrical connections.

 

Is this just a cast s480?

 

Zach,

started out with a cast S480 but when I went to the 402, I upgraded it to a billet 85 wheel. Same 96mm/1.32 turbine side.

Chuck,

thanks for jumping in. The electricals is unchanged from when I bought the rolling chassis. Batt positive and ground cables are both 1/0. They both run to junctions in the DS front wheel well. The ground cable is connected to the frame on it's route to the front. From the ground junction, there is a 4g cable to the engine, a 10g for big cooling fan and a 6g to a distribution block inside the car. There is another cable from the frame to the engine block. From the positive junction, there is a 4g to the starter, 4g to the alternator and 10g for the fan. The MS, like the Holley, has it grounds to the head.

Hope I didn't muddy the waters with that description. I could try and draw a diagram if it would help.

 

Have you ever verified actually timing with a light vs. ECU timing ?

 

Huh, 100% meth shouldn’t drown spark at all. Might pin the power supply wire to the coils (I use a needle) and run it to a volt meter so you can watch actual supplied coil power on a pull?

I ran into the same drop with mine using 100a alternators. Switching to the 1 wire 160A Fbody alternator fixed it. ($140 on ebay) Didn’t have spark issues but the fuel pump was dropping off. (killing the fan at WOT helped a lot with my setup too if you aren’t doing that)

Still weird though. U have plenty of dwell time to fully charge the coils. Even at 12.5v I’d think it should fire off small gaps easily with no water in the mix. What kind of Dwell does Pantera suggest on his 510C coils? I know weak spark has always been an issue on the Holleys. Zbrown ran .015 gap forever on his setup and said he didn’t appear to have any spark performance issues gapping down that small. He has switched to the IGN-1A’s since as well.

Hellbents10 ran the old square coils at 6ms dwell. 40+psi on straight methanol up to 9k rpm. They hit a wall at 204mph with them. Kurt Urban seems to favor those as well among the stock coils.

 

As mentioned before, I've verified the timing several times.

I am running a 1-wire 145A DR44G with a 470-Ohm resistor in the wire. Today I redid the alt batt cable and cleaned up the connections and now I have 14.1V at idle and with the hi-beams, tranny cooler pump and on-board compressor turned on, it only dropped to 14.0V. Don't know how that load compares to full power load on the rack though and I didn't want to run a lot of boost on street. What voltages are you seeing at idle and at full load on the track?

I have the coil dwell fixed at 3.5 but plan to call Lance later and see has any thoughts and his suggestion for a dwell table for the 510C. Prior to the 510C, I ran 581s, so I don't think it's a coil-specific problem.

 

Long long shot,,, but I've fixed a few intermittent ignition and injector firing issues by adding a nice heavy ground wire from each head to block and 1 from the intake (If metal) to the block, All the same location.. (I usually use the bolt that the brackets the injectors connect to. )

I think ground/ground loops get more important with the spark and injection firing by digital controlled ignition. The coatings on the newer head gaskets are suspect to me in how well the head can actually ground to the block, especially with steel fasteners on a AL assembly. I use one on the trans to engine junction around one of the transmission bolts.. I also use electrical connection grease on them with toothed washers from a electrical supplier.

I started doing it back when we converted large building control systems for analog to digital we used to have all kinds of hair pulling issues when digital PLC tech became the mainstream vs hot wire analog signals..

Good luck,, and let us know the end result when you sort it..

 

Have you tried different firmware in the holley, seems to me that others may have been having some issues but i'm not certain.

 

I run the standard 510c coils at 4.5ms but have done the spark jump test up to 7ms. Beyond 6 I really can’t see a difference, but between 3.5 and 4.5 is noticeable.

 

I read it all, and had deja vu. First thought that came to mind? 16 volts

I'm unsure how many are still running 16v but that was a movement to get around similar issues in days gone by.


That aside, with above I am a BIG fan of grounds that work. Creating a network so the pulses dont loop backwards is also important ( ever into car audio? ) Ground placement as well as abundance surely wont hurt you. I like the idea of a single dedicated ground per coil and a decent copper strap per side of block and a few chassis leads. Does the Holley have a ground lead directly to the ECM similar to factory LS PCM? If so make sure its added.

You might want to look at power supply as well. Its possible the new ECU draws more than your previous and the feeds for it and the coils are not quite good enough? Im guessing blind here, but the thought popped up so I mentioned.