Wednesday, February 20, 2013

Pro Comp Electronics Stack Injection


Pro Comp Electronics Stack Injection

I purchased a Pro Comp stack injection system for a Small Block Chevy engine this past November from a distributor in California called Straight Line Performance in Norco California, it was advertised as being usable with a speed density ECU of TPI variant FAST, Holley, or equivalent. It was also advertised as having a vacuum plenum (which would be necessary to run a map sensor.)

I received my system (intake, throttle bodies, fuel rails, and some assorted plumbing) as advertised. I was curious to see if the throttle bodies could be swapped side for side to put the injectors to the inside as Straight Line Performance said they probably could. That was to no avail as the fuel rails would have hit each other and the electrical connections would have also. While the throttle bodies were off I took pictures of the remaining manifold and adapters.

The entire system is made in Australia and shipped here through distributors. The intake was originally designed for IDA style Weber carburation and then adapters were machined to accept this Australian throttle body. As I inspected the system further I observed there was NO vacuum plenum or for that matter no fittings or open bungs for vacuum whatsoever. I contacted Straight Line and asked why the Small Block Chevy system had no vacuum system. He assured me it was there and had 3/8” hole in the runners. With the throttle bodies off and a runner length of only 2 inches any holes would have been readily visible but weren’t there.

I was bound and determined to use this system based on the latest TPI Chevy computer # 1227730 (speed density) with 24lb injectors, with a dedicated custom stand alone harness and a custom burned prom. To accomplish this goal I needed a vacuum source, so I modified the runners to come together underneath the intake and exit on top of the manifold in the rear. After close to 4 hours work this was accomplished.

I installed the entire system and proceeded to fire the unit. After 4 different proms we finally came to a combination that didn’t run so rich, but the main problem was that the system made very little vacuum (10 inches.), right on the borderline for the ability to run a speed density computer. To get it to idle and run at all I had to apply an external vacuum (mighty vac) @ 18inches.

While the system was acquiring operating temperature everything seemed ok, but it was when it went into closed loop things fell apart. The system started to pop back through the throttle bodies in random patterns, it was also popping through the exhaust. Any additional blipping of the throttle would cause additional backfiring. The man I had do the electronic setup has done 100’s of these things commercially and he was as baffled as I was. First we tried another Map sensor, then kicked down the fuel pressure to lean it out (we finally ended up @ 35psi). We replace the computer and 4 custom burned chips. Each chip got successively better but still not actually drivable.

My electronics guy thought it might be that the FI trigger wire (to negative coil tower) might be getting interference from surrounding electronics and suggested I install a MSD 6 AL to acquire a cleaner square wave signal for the FI trigger. After trying that it was to no avail, the system just flat out won’t work with a speed density system. I even looked up the Pro Comp Electronics catalog and they showed a small block Ford intake with throttle bodies and said that a Small Block Chevy system was available. They also claimed that the Chevy system has a vacuum plenum….it doesn’t! The Pro Comp catalog shows a complete turn-key system but doesn’t say if it is a speed density system or if it’s an Alpha-N system (which would make far more sense.)

Alpha-N takes the vacuum out of the equation entirely because it makes decisions based on TPS, ignition pulse, and oxygen sensor input. You might think, “what’s the big deal just get the Alpha-N computer.” The difference is the price…..a factory style TPI speed density computer can be had with prom for about $300……..The Alpha-N systems start at about $1700!

Initially I thought, “How can anyone build an electronic fuel injection manifold with no vacuum ports?” The answer is right there if you pay attention, the manifold was originally designed for carburation (Weber IDA’s.) With a stick shift transmission there would be no need for vacuum. Obviously the transformation to electronic fuel injection was not very well thought out as ANY speed density system requires a map sensor be hooked up to the engine vacuum, and this one has none!

Fortunately my electronic guy has been here and done that before. He was doubtful from the start that a stack injection system could run off a speed density system. They are notoriously low vacuum producers. Thank goodness he has done low buck Alpha-N stack injection systems before. He has worked with the now obsolete Accel Gen 6 ECU before on a retrofitted Hilborn stack setup. The Gen 6 ECU has an Alpha–N capability at a low price, so we found the computer, altered the harness, programmed the new ECU and reinstalled the system.

Today was the turning point, the car acts 100% different with the Alpha-N tune in the Accel Gen 6 box. Idles great and has the crispness that one expects with electronic fuel injection. Jim's Performance had the knowledge to fix a problem caused by a manufacturer that didn’t do the required research and development to properly sort out their finished product. I blame both Pro-Comp (who to this day never returned my phone calls), and Straight Line Performance in Norco California that denied my claim that the intake manifold didn’t have and vacuum provisions (they told me I didn’t know where to look!)

Conclusion:

Would I ever buy another product from Pro-Comp Electronics? The obvious answer is NO! Would I buy anything from the distributor known as Straight Line Performance? This ranks and even bigger NO! The owner was very condescending after he had all my money and ignored any and all my concerns. I now know how to “fix” this poorly executed system, but there are other systems that are designed better and perform better. Maybe the Small Block Ford stack system they make is better and actually HAS a vacuum plenum, but I know the Small Block Chevy system does NOT! Be forewarned the manufacturer and the distributor BOTH confirmed to me that this system would run with a speed density computer…….IT WILL NOT! VERY DISSATISFIED!

27 comments:

Bobby Kraft said...

I have considered an electronic stack injection system for my gasser, do you know anything about the Inglese system?

republican patriot said...

You may want to view this video first Bobby http://www.youtube.com/watch?v=2tJ4kqgRGvc

circuit board said...

I wanted to thank you for this great read!! I definitely enjoying every little bit of it I have you bookmarked to check out new stuff you post.

Gasser Madness said...

What ECU did finally use? I assume it was Alpha-N?

republican patriot said...

Because I didn't want to spend the big bucks to purchase F.A.S.T., Big Stuff, Holley etc, my Electronics guy convinced me to buy a now obsolete Accel Gen 6 ECU, it has Alpha-N capability.

Anonymous said...

I would have to say what was your reasoning for not using procomps ecu it runs speed density or the alpha n

republican patriot said...

#1 the distributer Straight Line Performance never even offered the injection as a complete kit....obviously I received my injection in the system's infancy. I have seen the ECU in Pro-Comp's catalog, but not sure whose ECU it is, let alone an explanation wheather or not it has Alpha-N capability.

Anonymous said...

i know I wouldnt of been to thrilled about it.If you go to speedmaster (aka) turnkey efi there is a technical and scroll down and there is your info on the computer.the alpha n I wouldnt think would work well with this not enogh trim curves.But realize this most closed loop systems will not operate well untill your temerature is above 200 degrees some fib and say 180 but its makes a big difference in tuning. But are you happy with this setup

republican patriot said...

The Accel gen 6 is setup right now to go into closed loop @ 165 degrees, we are going to do final dyno tuning within the next few weeks....but for right now, yes I am finally satisfied

republican patriot said...

I went to turnkey efi and had to actually search the instruction sheet to find that their ECU is capable with Alpha-N tuning. I guess my concern would be that if they lied about the systems ability to run speed density, and the problem of not having a vacuum plenum.......why would I trust their computer either?

Anonymous said...

well you went a little to far download the software not the instruction sheet 1st download and it will show you how to run there computer in closed loop or alpha n

Gasser Madness said...

Why would a manufacture of a product like this claim that it would run on speed density computer at all when they have no vacuum plenum?

republican patriot said...

This is my point exactly!

republican patriot said...

Update: I finally got the car to a dyno @ Anderson Performance East in Stevensville, MD......WHAT a huge difference!.....Thanks Bill!

http://www.youtube.com/watch?v=wXesvI49Ek0&list=UUCKaLG_zwxF6kLp9AiUgbcw&index=1

Rodolfo Karl said...

Very interesting topic, thank you for this article!

Anonymous said...

How would you rate the quality of the rest of the system? The castings, TBs and linkage, ect? They have a complete kit less injectors for $2500! The 388 SBC cam in my Cobra kit is 250* @ .050” so I will for sure need Alfa-N!

Al

A 60 something Rightwinger!

republican patriot said...

Well, the casting was originally made for weber carbs, then adapters were made to mate the 50 MM throttle bodies to the manifold. Alpha N is the ONLY way for these manifolds to run on a computer because of the lack of adequate vacuum. Speed density requires not only a vacuum signal but a signal that doesn't pulse. Power brakes with this setup is most certainly out of the question. Automatic transmissions that have vacuum controlled shifting such as a 350TH or a 400TH are only marginally acceptable, but cable controlled shifting such as 200R or 700R-4 could only work if an acceptable fixture could be made to mate to the opposite side of the round center linkage controller.

Mike Woosley said...

Hi Al,
Can you please tell me what cable you used for the bell crank? I purchased the same pro comp for my windsor. Thanks in advance.

Mike
Wasilla, AK

republican patriot said...

Hi Mike, just used a Lokar cable kit

Mark Walters said...

I love your technical interpretation of an installation that almost all gasser guys would love to do. Although most of your posts have to do with politics, do you intend to write anymore car related articles?

republican patriot said...

Funny you should ask this question Mark! I am working right now on a project with a small block Chevy to return a high MPG result in an "A" body GM car!....stay tuned!

RIC said...

ARE YOU SATISFIED WITH THE MECHANICAL COMPONENTS IN THE EFI SYSTEM YOU USED?

republican patriot said...

No I'm not Ric, and here is why.......the throttle bodies are WAY to big for ANY application they are 50MM EACH! This was a poorly designed product with even a less thought out plan to make it work to the end user.

Glenn Sawyer said...

Hope all is well? My name is Glenn Sawyer I live in Australia. Earlier this year I purchased a Procomp turnkey EFI 8 stack fuel injection setup, and like you I could not get any help whatsoever here in Australia. When I rang Procomp here in Australia I would be put off every time. I eventually got onto Louis Forester at Procomp USA, and he at least answered all of my phone calls that I made. He did email me a 13 page trouble shooting guide which was very helpful to me also .I have read your opinion on the turnkey EFI and agree 100% with you. The people here in Australia gave me 42lb/hr. fuel injectors which I thought were a bit of an over kill. After I started the car up I had a lot of black fumy smoke everywhere and Excess fuel been pumped into the engine. I have ordered 8 x 24lb/hr. injectors which I hope will be here tomorrow. Would you be willing to share what you have your settings set at so I can compare with mine? I could also email or fax to you the 13 page trouble shooting guide, if you would like.

republican patriot said...

Well Glenn, I have sold this car and the fuel map went with it, and unless you are running an Accel Gen 6 box the map would be useless. Yea the very fact they suggested 42lb injectors means they have NO clue about what works with this setup. I wish you luck......have your dyno tune guy run the base idle pretty fat, somewhere around 12.5 AFR otherwise the motor will fall flat on it's face at the slightest opening of the throttle the tip in is a bitch because of the 8 50 MM bodies

nakedblogger said...

Actually the ford system does have a good vacuum port and works wonderful. no problems!
Use their ECU why take on a problem when you don't have to...

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