My 3.4 Life Story Build Complete-Tuning Issues w/3.6 Injectors

[asphaltgambler]

Hi, all! So this car / restoration has been quite a journey for me. Over my 54 years on earth, I have completed many different restorations and rebuilds from vintage bikes, muscle cars, original style trucks, even an old wooden boat or two.

This area of work was also a big part of my professional life. I can honestly say I have journey-man level competence in just about every area. I am also very detail oriented with my work. But this car without-a-doubt has been the most challenging in every possible way. I started this in 2005 if that gives you any idea. The two largest obstacles were initially time and money to commit. Then when the economy crashed, it was mostly money.

I bought this car in the fall of '04, the engine promptly threw a rod and there I was. To make matters worse, the car was really going to be a 'play-toy' for the wife and I. So much for that.............................We then decided to take the toughest route possible. Complete tear down to shell and start going through every piece, every system my way so when complete we would know that car inside and out and plan to keep it until we die (no kidding)


The engine is: Michael Mount built big bore 3.4, 10:2 compression, JE pistons, Elgin cam set with custom grind; big lift-aggressive duration but tightened up the lobe-center line for good street manners. All ARP fasteners, the heads have been flowed and blended, turbo oil pump, B&B headers and last but not least 964 induction system with MSD controller for the resonance flap.



Engine management: is stock Motronic box modified by Steve Wong to double-speed the board and one of his custom chips. MSD coil and wires. the 964 intake and injectors with a Lindsey Racing mass-air conversion that has a standard 911 fuel map file installed. The fuel lines are custom; retain are original fittings but have converted to braided lines and kept the original crush cup sleeves on the ends.

Problem: I finally arrived to the point to start and run last night. It sounds awesome and very, very crisp response but it is running very rich across the entire RPM range. I mean blubbering black smoke.

I am a very experienced tuner and I would guess the amount of fuel in the combustion chamber is easily 25% or greater than needed to proper A/F ratio. I do have a wide-band oxygen sensor system installed and calibrated. The needle almost stays at "0"

I really believe after much thought the problem is mostly the 3.6 injectors. I had them cleaned and balanced a few ago and kept them safe until install. I understand their is some difference with the resistance between them and the standard 3.2 injectors. I did not know this prior to buying/swapping my old intake set-up for the plastic 964 unit.

I'm sure there are tuning issue ahead that will need addressed but the overly fat fuel delivery I think is mechanically related (wrong injector application)

Here are a few pics, I have not finished cleaning or detailing until I fix the fuel problem.








I'd like some feedback as to anyone who has done this swap and if they installed the 3.6 injectors or kept the 3.2 injectors that were originally installed - Thanks!

[kojo911]

Sounds like a safe assumption. Just a guess but if u sent out a moronic box from a 3.2 and asked for a chip to match larger displacement etc., the duration that the injector is open would be greater than stock. I bet that the 3.6 injectors are larger or flow more and are dumping a ton of gas in the thing. Just a thought, but do you know if the signal sent by the Lindsey MAF is compatible with your set up?

[asphaltgambler]

Actually there is an update. Apparently the Lindsey Mass air unit had to get 'friendly' with the combination. Once there was a heat cycle and restart today everything seems to be inline as far as running and AF - go figure!!

[Flat6pac]

I am of the understanding that the 3.6 injectors dont work in a 3.2.
I was doing a 3.4 with enlarged throttle body and know the 3.6 uses the same air flow sensor as a 3.2 so the 3.6 injectors seemed the likely idea but research said no...
Bruce

[Dan J]

Which fuel pressure regulator are you using? The 3.6 is if I remember correctly is a 3.8 bar
and a 3.2 is a 2.5 bar ( the numbers may be wrong I'm going off memory but the 3.6 runs higher pressure for sure) Which would give you way too much fuel if your DME is tuned for the lower pressure injectors. I'd probably also put the 3.2 injectors back in. Personally I'm not a fan of the mass flow conversions I'd put the AFM back on but that's me