Powerjection III Install and Review

Shameless bump for pic!

 

Alternators from carb cars don't charge till 2500 rpm so you won't see 14.4v at idle, so upgrade the alternator to one off of a EFI car. I can't help with the ticking.:beers2:

 

My car rarely see's 14.5v. It often hangs in the high 13's. I'm ok with that as long as the fuel pump is doing it's thing, which even at ~12.5 volts still maintains ~43psi. I'm using a mid-late 80's GM 105 amp alternator.

 

Yeah, even in the low 13's the fuel pump was working fin and giving me 45psi, but it still ran horribly. As soon as the voltage went up the engine starting running better.
I'm going to go ahead and upgrade the big three to 1/0 gauge. It's been something I've been putting off since I bought it, buit I figure, I might as well do it now and see if it helps. I have tons of extra wiring from past sound system builds, so it's just a matter of taking the half hour and doing it. Sounds like it might be a project for this evening.

 

The more I think about it, the more I think it IS interference. When watching the RPM's on my laptop, it will roam from 900-1300 at idle and will read up 500rpm's higher than my tach when driving.

The tach singal wire going from the -terminal on the coil and the power cable going from the battery + to the ecu run along the same route right next to each other. COuld that be causing interference?

Originally, I USED to have the tach signal wire fromt he ECU spliced intot he tach wire from the coming from the tach at the rear of the block before and never had this problem...but I also had the MSD box hooked up back then too.

I think the errant tach signal might be the route cause of the problems I'm seeing. I'm going to re-splice into the tach signal wire from the tach at the rear of the engine and see if that does anything.

 

When I first started up my FI system, during cranking the computer showed 11,000 RPM. Needless to say I also had strong ignition interference (amplified by the MSD) and the engine flooded out pretty bad.

I had to move to an external coil and get rid of my HEI.

-Bob C.

 

What ignition set up are you using now? If you are not using a shielded wire for your tach signal, it can very well be picking up interference from your spark plug wires or even alternator.

Points are noisy as all heck. Signals off the negative terminal of the Coil can be noisy (though my T-bird is hooked up that way with a pertronix in place of the points). I've ran off the Tach signal port on the 4-pin HEI with out trouble, same with the 7-pin. Now I run straight off the HEI pickup coil with no module, using the MSII to tell the MSD 6al when to fire.

 

I have a Mallory Magnetic Breakerless Distributo and an MSD Blaster II coil.

 

Finally got a hold of Retrotek and went through some troubleshooting. I got the decel problem taken care of, but the rpm hunting is still messing everything up. They took a look at the some logs i took and said everything with the ecu itself is good. So we came to the conclusion that it IS interference with the signal wire.

Sigh. There are only two things that have changed since I had the unit on originally:

1. Originally, I had an MSD 6 box hooked up to everything.
2. Due to the placement of the MSD box, the wiring for everything went over the A/C box and up the passenger side fender to the battery.

I'm not really sure where to go at this point, there is no active way to change how sensitive the ECU is to interference. I REALLY don't want to have to buy a new ignition box, but since I've already tried routing the signal wire away from everything else, I'm kinda out of other options. I WAS toying with the idea of sticking a stock distributor in there and seeing if maybe it's the distributor itself causing the interference but I'm not sure how that could be.

Open to suggestions.

 

I know zip about your mallory distributor, but is there a place you can tap into for a tach feed before it hit's the coil?

Can the powerjection take a variable reluctor (VR) or Hall Effect signal? I'm not sure which type of signal the mallory breakerless system uses, but if you can find out which type it is (HEI's are VR style, pertronix conversions of points are Hall effect as examples), you may be able to pull the tach single straight off the pickup signal.

Another note would be, is it signal interference on just the tach signal, or do all the sensors have interference noise (checking the datalogs, do the coolant temp and intake air temp numbers wobble +/- 3 regularly)? IF they all show some interference, go pick up a radio noise suppression filter from any place that sells car stereos and install on the power feed to the ECU. That's all you can really do for that since the throttlebody is the ground source.

 

Yes, I can tap into the tach wire goign to the tach at the back of the engine befor eit enters the main wire loom. in fact, I tried that to see if it made had any kind of effect and nada.

I'll have to double check the data logs to see if the coolant and IAT are stable or not. From what the tuner at Retrotek said, everything else looked fine except the rpm's.

I might try to relocate the coil away from the distributor/alternator/plug wires and see if that has any effect.

If all that fails, I'll just break down and get another CD ignition box.

 

In the voice of Borat..GREAT SUCCESS! I got the new Summit Ignition box installed tonight, set the rev limiter to 5500 and bam! no more tach hunting! Car runs like a raped ape!

I do have one question: Why would a single plane intake allow me to run more advance than the dual plane EB? That's the ONLY thing I've changed and I seem to keep being able to dial in a few more degrees of timing. I'm up to 10* initial timing with a total of 34 before 3500rpm.

Anyway, I'm happy now. Seems to be running well. We'll see how long it lasts. Thanks for the help everyone.

 

My "guess" would be less cylinder filling at low rpm, and thus less pressure in the cylinder and will use more advance. Lazy air flow at lower rpm, I don't think MPI would be as noticable, because your system is throttle body injected so is a wet flow manifold vs. a MPI style dry flow. Are you sure your total needed to change?

Glad to hear it's running strong!

 

I didn't change the mechanical advance...it came set fromt he factory with 24* mechanical advance. With the old dual plane, I tested it to see what initial timing setting gave me best performance without pining and it was around 6* initial. I've got it set to 10* initial right now and still no pining...might try 12* later and see how that responds.

 

I can run 36* total with 20* initial on 87 octane in my lazy GS350 with no pinging...

Congrats on the install. I've been eyeing the setup..

 

First measured fuel mileage results are in...I got a whopping 9.5mpg. No different than the tired Quadrajet that i had on there before. This is all city driving, approx 30 miles a day. I've got the AFR set at 14.5 at idle and 14.2 for most of the cruising I do around down. I might try to lean it up again a bit to see if that helps. Next step will be the 200-r4 to see how that helps.

 

Oi, that mpg is rough, it is city though... What rear gears are you running? I'd of hoped that cam would of do better =/

 

Stock 3.42 posi. I thought it would do much better also...I was hoping for 12-13 at least! Sigh. I should've gotten an MPFI setup.

 

An overdrive should up that number pretty good. My Centurion get's 12 around town with TH400 and 2.93's out back. So hopefully it's in your gearing. All my V8 cars have either had 2.xx gears or overdrives. An overdrive ought to kick that number up some, even in the city driving.

 

Yeah, I'm thinking it's gearing as well siince my old 71 Riv, that had 2.92's, got around 13-14mpg with a carb.