A little adventure of mine, for thoes who are interested:

I had my car dyno-tuned last August.
The base fuel pressure on my Autometer gauge (installed under the hood) read around 40psi (or higher if I recall correctly).

That gauge blew up and dumped fuel all over my coil pack
So, I got another one - which did the exact same thing!

Some time passes without a FP gauge.
I finally put a B&M one in and it reads just under 20psi - WTF?!
Not believing this, I put in a $10 gauge from CISCO. This one also reads just under 20psi - WTF?!
So I trade the B&M gauge for a Russell (liquid filled). This one also reads just under 20psi.

Now, I figure I'll turn the FP up to 25psi and see what happens.
Crappy idle, black smoke @ WOT, A/F gauge reads rich @ part-throttle.

When I review logs of track runs, I see knock at the top of 3rd - eventhough supposidly my fuel is fine. I've always attributed this to having too much timing - due to a low airflow signal - due to my HKS S-AFR being leaned out across the board (as I had assumed).
That theory can go out the window now. There's no way my S-AFR could be so lean with such low FP. So for the first time I take a look at what's set up in there:
Below 3000rpm, generally +30% correction.
Above 3000rpm, generally 0% correction.

Next time at the track I'll turn the base FP up and re-tune with a wideband.
Hopefully this will take care of some of that knock up top.

Mods to mention:
720cc injectors, Walbro pump, ChargedAir AFPR, HKS S-AFR,
9:1 pistons, 17cTD06 turbo (similar to a 20G), FMIC, 3" turbo-back, 2G MAFS.

I wonder if the spring in the FPR could have loosened up over time?

Seems strange that *two* gauges would have been that incorrect, and by the same amount.

Jeff, I did consider that possibility.
But, that does not explain why I'm rich when the fuel pressure is raised.
Just based on my S-AFR settings I think it's safe to say that 20psi is the actual pressure, from day one (on the dyno).

If the spring did loosen - it could only mean that I was tuned really rich on that dyno.
It's possible but I doubt it since the car has pulled pretty much the same ever since.
My times and logs at the track are even consistant (the same) between 40psi (Autometer gauges) and 20psi (new gauges).
An extra 5psi of FP made a HUGE difference. I couldn't even imagine how rich it would be if I turned that up to 40psi right now (without re-adjusting the S-AFR).

Oh and I should add that Performance Improvements no longer stocks/sells the Autometer FP gagues.
Coincidence?

ChargedAir AFPR

I have seen about 4 of these FPR go low after a while (more then 6 months old)in the past 2 years (since they came out) its a good thing you caught it.

Now I'm stumped...

If it is the AFPR and not the gauges, then why has everything been so consistant (track times/logs)?

Is there something compensating for this lack of fuel pressure that I don't understand?

I'd love to put my finger on this...
But in the end I think tuning again from scratch is the only solution

Here are some logs...
They both end at around 6200rpm in 3rd gear.

LAST FALL: 40+ psi BASE FUEL PRESSURE
(according to Autometer gauges)


TODAY: 20 psi BASE FUEL PRESSURE
(according to Russell and two other brands):


I've changed absolutely nothing in the time between these two logs.

If there really was a difference of 20psi, wouldn't that be seen in the logs?

This is why I'm pointing my finger at Autometer.

My offer still stands of letting you test the aeromotive AFPR I have sitting in my garage that hasn't made it into my car yet. Let me know.

Thanks for the offer Noah!

I'm going to see what happens when I re-tune with a wideband and higher FP.
If the results still don't make sense I may have to take you up on that