Good day.

I took my 1987 NA (racecar) to the dyno to see what my baseline numbers are.

The car made 144 hp at the wheels.

Mods:

OBX header to borla stainless catback (duals, not true duals).
All emissions removed.
secondary throttle plates removed.
A?C removed
Airpump removed
Power steering removed
charcoal canister removed (catch can with filter installed).
Stock ports
Stock ECU
Stock plugs / wires
stock air box and AFM.
Aux ports are wired open with pineapple racing inserts.


The car is running 13.9 to 14.1 AFR while pulling between 4500 and 7000 (dyno tests run in 3rd gear).

The lamda sensor is about 15 inches from the exhaust ports in the exhaust stream from # 2 rotor.

The fuel pressure is 50 psi (I have no idea why it is that high, stock fuel rail and regulator).


During the dyno run, the stock O2 sensor was removed (I figured it didn't matter since this was to be performed at full throttle).

The injectors were cleaned about 12 months ago by marren.

I believe the grounds are good. I will recheck those tonight. I am also removing the injectors to have them sent back out (its cheap and worthwhile if it is an issue).

I DO have the massive 3800 hesitation where the AFR goes crazy lean (like 16:1) and the car makes less power in that 100 to 200 rpm band. I assume this is from teh secondary injectors coming on a little late.


Any ideas?

Thanks!

Rob R.

 

Grounds!!!

 

+1 for grounds.

do you have any kind of piggyback controller like an SAFC installed?

 

Other than grounds, which have been already mentioned...

How smooth is the idle? TPS Sensor set? Any vacuum leaks (test using propane or starter fluid sprayed around intake)?

edit: fuel pressure is 50PSI as you mentioned, but this is with the pressure gauge tee-d into the fuel system on the supply side?

 

Yes, teed into the supply line.

The grounds were double checked and ohmd. They are good.

The car starts right up first crank and idles at about 800 rpm once it gets a little temp.

I found something else while I was playing with injectors. The line from the boost sensor was plugged. Could that do it? I wouldn't think so because it still knows how much air is going in from the AFM.


Thanks!
Rob R.

 

No piggyback controllers or anything either.

 

Actually, the boost sensor needs to see what's going on. Along with RPM's, it enables the secondary injectors.

IIRC, the vacuum line goes to just above the ACV (which you may not have anymore). Also, make sure it's plugged in.

 

Well, that is probably the issue!

I do not have the acv anymore. Basically, the line goes to the port in the upper intake manifold that is right at the flange between upper and lower intake manifolds that "points" at the passenger side shock tower, Right?

 

You don't need the ACV. That's only for emissions. It shouldn't radically effect how the car drives

 

on an NA that is correct. the turbo goes to a port on the ACV.

 

On a sidenote, when I installed the acv block off plate I drilled and tapped 2 holes in it to use as vacuum/boost nipples. The thing is, it blows air out of the nipples anytime the motor's running

 

Are you sure it's completely plugged? It has a plastic restrictor pill in the line; very tiny orifice in it. The restrictor needs to be there. It should be very difficult to blow air through it, but it should still move some air. Try putting one end of the line into a cup of water and blowing through it to check for bubbles.