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Fuel Pressure Gauge

3K views 15 replies 7 participants last post by  Louvered97GTP 
#1 ·
It was brought to my attention that you can never max out 42.5lb injectors with an M90 car. Well my injectors are just about maxed out running a 2.8 pulley and stg 3 IC, xpz cam and stg 3 heads. I am seeing 20+ ms on the ipw's during my scan and about 4* of knock with stock timing and AFR at 11.3 on the wideband at WOT. So I was told that I could be losing fuel pressure at WOT and the injectors are trying to make up for it by opening longer.

My question is, how accurate is an Electrical Fuel pressure Gauge? Or should I just go Mechanical with an isolator to mount the gauge inside the car?
 
#2 ·
It would be worth it to be able to monitor fuel pressure for sure. I am not sure if Autometer even still offers the mechanical gauge with an isolator. I have it on my Turbo Mustang. But it has been about 10 years since I bought it. LOL. I believe we still have an electrical fuel pressure gauge from Scotts car for sale.



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#3 ·
I have an electrical gauge from autometer and I find it to be pretty crucial. The fuel pressure gauge on my fuel pressure rails reads the same as the one in my pod. I might be wrong, but I thought the 42.5s get maxed out easily with as many mods as you have?
 
#4 ·
So the electrical gauge reads the same as your mechanical gauge at idle. What does the electrical gauge read at WOT?
I still need to install my FP rewire kit this weekend. My problem may have been due to a weak battery that I replaced yesterday with an optima red top. Hopefully the FP rewire will help too. I really don't think I should be seeing knock w/ a 2.8 with my mods.

It would be worth it to be able to monitor fuel pressure for sure. I am not sure if Autometer even still offers the mechanical gauge with an isolator. I have it on my Turbo Mustang. But it has been about 10 years since I bought it. LOL. I believe we still have an electrical fuel pressure gauge from Scotts car for sale.
Autometer does sell a mechanical FP gauge that reads up to 100psi. I can get the isolater still too. I was told however that the isolator and the gauge need to be mounted at the same height for accuracy in reading.
 
#5 ·
Asking how accurate an electrical gauge is would depend on how good the electrical gauge is.. know what I mean?

If you buy a gauge that is accurate to X readings and Y speed, then it should do those things. The nice thing about electrical vs mechanical is going through the firewall with the pressurized hose.
 
#6 ·
That is true, the down side is if you have a problem, or skewed reading, you have to rule out the electrical side first. Hence when you have an Oil Pressure problem, the first thing you do is check Oil Pressure with a mechanical gauge.

I would like to know at what speed the readings are delivered on the electrical gauge.
 
#7 ·
First, If i'm reading this correctly, the only thing you have done with your fueling is add 42.5# injectors? If so, I'm surprised you went that far with your build and never addressed your fueling past the addition of larger injectors. Fueling is the most crucial thing in keeping these boosted motors alive. Are you still running a stock 1999 fuel pump too?

Get the Autometer electrical gauge. Mine has never let me down and even though I don't have a mechanical reading to compare it to, I feel the readings are acurate. Add the rewire kit and then look to see where your at with those things and your new battery.

I don't know that I would believe the idea that 42.5's will be enough for any M90 car, i've seen plenty M90 cars that go through a whole lotta fuel. Even if that was the case, you still need to support the larger injectors with something, volts, pump....
 
#8 ·
as far as fueling, I have upgraded flow matched injectors, the walbro 255lb/hr pump, stock regulator, and an ICCU to control the fueling at different maf frequencys. I just got the rewire kit and am going to install it this weekend. I would of last weekend but it was 20* outside. AS far as the battery, I just had to wait until I had enough money for the Optima. Those things are $150 bucks.

I'm looking to upgrade to the 65lb injectors as I want to twin charge my car next year. So might as well get them now.

I think I may get that electrical gauge. How does it work exactly? Does it have a fitting that screws on to the fuel rail and then an electrical sender on the other side of it?
 
#11 ·
I have modified stock rails but it still has the -4AN fitting on it. So I just need to find the fitting that is dual female, one side being 4AN and the other accepting the 1/8" NPT correct?
 
#13 ·
I originally had the 2 piece adapter made out of AN fittings. I think I misread your post because my response to your question doesn't make a lot of sense really and isn't that helpful, sorry bout that...I will still post those pics for the hell of it.
 
#14 ·
It's actually true that the power output available to the wheels on an M90 car is well within the support of 42's. However, that doesn't account for the loss from loading the SC. My 42's are maxxed on a Walbro, AFPR, and a MSD BAP.
 
#15 ·
Ron, What is a MSD BAP??

What puzzles me is that my knock doesn't start showing up until about 92mph and above 5500rpm in 3rd gear. My wideband shows that I'm rich running 11.3. Boost is around 12.5-13psi, stock timing. I can up the ICCU at WOT, but it doesn't really help.

Seriously with a STG 3 IC, heads and the XPZ cam, there shouldn't be any knock. When I scan, my LTFT's are very close to 0. Could this have something to to with PE vs Time vs RPM?
 
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