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Robert, if you showed no mixture increase I suspect your TPS was bad. On a stock motor that much change should vary mixture between 14 and 10. You had other problems.
The best place to check would be in the tailpipe after the two pipes merge together. It would be easy to add a bung at that point. Another thing that would be good is the addition of the data ack LM1 to monitor mixture. Chuck
The reason I use the LM1 is that it interfaces nicely with the MegaTune software for data logging.
Those of you that log, tell us what the F/A ratio is on the long straights where you race. CB
I just connected a $16 Harbor Freight fuel pressure gauge up. I expected to find 3bar (43.5psi) held steady, relatively independent of engine rpm. But what I got was 38psi at idle and 35psi whenever I put a few rpms on it.
With a $16 gauge it’s hard to know anything for sure tho. I have a couple spare FP regulators, so I’ll try another one.
What should I expect with FP dropping under different manifold vacuum conditions?
The only test in Bentley is 43.5psi by jumping fuel pump relay with motor off.
I clamped off return valve and FP went thru the roof so certainly the fuel pump is capable of decent pressure.
Later edit. Spare FP regulator shows same behavior. So I imagine that my cheap gauge isn’t that accurate. I’d a sure felt better tho if FP stayed rock solid at 43psi, independent of rpms.
What does the vacuum line to the FPR do anyhow? Vacuum is high at idle and low at at WOT, right? Or do I have that backwards? So the vacuum line has to tell the FPR that the motor wants lots of fuel, so maybe it restricts return flow (increasing FP) a little so more fuel is available on the rail.
That’s what confuses me. That’s the opposite behavior from what I saw where giving the car some gas seemed to cause FP to drop.
What am I missing?
Ranger wrote:
[quote]I just connected a $16 Harbor Freight fuel pressure gauge up. I expected to find 3bar (43.5psi) held steady, relatively independent of engine rpm. But what I got was 38psi at idle and 35psi whenever I put a few rpms on it.
With a $16 gauge it’s hard to know anything for sure tho. I have a couple spare FP regulators, so I’ll try another one.
What should I expect with FP dropping under different manifold vacuum conditions?
The only test in Bentley is 43.5psi by jumping fuel pump relay with motor off.
I clamped off return valve and FP went thru the roof so certainly the fuel pump is capable of decent pressure.
Later edit. Spare FP regulator shows same behavior. So I imagine that my cheap gauge isn’t that accurate. I’d a sure felt better tho if FP stayed rock solid at 43psi.[/quote]
Oh Jesus! :blink:
scottmc wrote:
[quote]
Oh Jesus! :blink:[/quote]
ScottM: if obsessive behavior ended, it wouldn’t be obsessive.
Another interesting test. I pulled the vac line from the FPR and FP immediately went to the correct 3bar. So the increased vac of idle depresses FP and it goes to it’s correct 3bar only under higher throttle conditions because vac is reduced. Do I have that right?
And this means the my $16 gauge is reasonably accurate. I love it when cheap tools end up working out fine.
You have engine vacuum everywhere except the top end of the rev rage at wot. Next dyno trip, plug the line and try. CB
Ranger wrote:
AFAIK yes. The FPR attempts to keep the pressure delta from the fuel rail to the intake manifold (i.e. across the fuel injectors) constant so a given pulse width equates to a known amount of fuel being metered.
FWIW just got off a DynoJet here in Greenville indicating 146hp/tq corrected over three runs within 10min of each other on my 220k (?) motor. A/F appeared to be in the 13s mostly. They said they’d Email me the data, if anyone wanted to see. It wasn’t the huge deficit I had hoped to blame poor laptimes on 
I’ll have to blame suspension setup and R888s now.