So as some of you know, because I'm maxing out my MAF with the 2.87" Pulley @ about 5800RPM the JWT ECU isn't tuning my fuel right with the 370cc Injectors.

So today I decided to put my Cartech back in.

Before putting it back in, I replaced my fuel pump (needed to do this anyway) and went for some runs. at max boost in 2nd Gear, I hit 59PSI of FP. Also left the T-Rex Aux pump plugged in for extra safety.

Went back to the garage, installed the Cartech on the return line from the rail, put a check valve on the end so that air only blew out of it, and didn't get sucked in with vacuum. "IN" port is coming from fuel rail, "OUT" is going out to fuel tank. (return line)

Tuned the dial down quite a bit and tuned the bleeder down about 1/2 way...Pulled the vacuum while running and PSI shot up from 38PSI to 44PSI on my cockpit fuel gauge.

So I went for some runs.....at full boost I was still hitting 59PSI. So of course I was like "WTF?" and turned the center **** in even more, checked again with vacuum line off - 50PSI.

Went for some runs - now I'm only hitting 56PSI at redline! But car feels INCREDIBLY strong...lit up 2nd gear like it wasn't a thing. Smoke everywhere.

So I turned it down EVEN FURTHER....without vacuum plugged in 54PSI....wnet for some more runs....

Didn't feel as strong this time (but still pretty nice) and I maxed out at 54PSI this time!.

So I turned the **** all the way out and opened the bleeder all the way - did some more runs...car feels kinda weak again and 59PSI max.

So the more I turn that screw in the more it DROPS FP on the gauge at redline, but raises it at idle without the vacuum plugged in. It also feels stronger when the Cartech is "on", not weaker as a considerable lean condition would represent.

EGT's never went above 1400 on any run.

So I guess my quesiton is wtf is going on? I have the FP Gauge sending unit on the INFLOW line to the fuel rail...could that be it? It's somehow causing this?

Thanks!
IanS

 

Why does Fuel pressure rise when you turn in your center screw with no boost acting on it. ?? Im having the same problem and my static pressure of my pump is only 50...Weird..

I have to decide if its the Sender Unit for the fuel pressure Sender or the BRAND NEW Walbro Intake pump I have

Im Clueless

-matt

 

The Cartech does that - it's how it's designed. That's not my problem, that's just how I was testing that it was working and my FP gauge was working.

FP does not rise when there is a vacuum line connected to it.

 

So we have no more room to adjust the static pressure setting (center ****)? Also when you mentioned with the pressure going down, though it looks like we did everything right....are we absolutely sure we didn't set it up backwards (I know dumb question, but we've had our moments before guess it's better to make absolutely sure).

S

 

just checking...but are you running this on top of the JWT ECU?

 

Yes.


maximase86 -

I described above in detail on how it's hooked up - I'm sure it's right - but I posted just in case - if it's wrong, soemone will correct us. According to the Cartech site, it's right.

The more the center **** goes down, the lower peak FP at redline is.
Under the same setting, pressure at 0 vacuum (idling with vacuum unplugged) shows raised FP.

The more you take it out, the more it goes back to normal (before Cartech).

I don't know why I'm explaining this to you - you saw it...lol.

 

I know....I'm just trying to re-think this through me head....just making sure we didn't miss something or what not.

S

 

So without any Vaccum acting on the Cartech, the Fuel pressure should rise when the center set screw is turned in ?? So when you have boost pressure acting on it, with a mightvac 10psi, fuel pressure should rise alot ??

-matt

 

Yes - except I don't have a Mighty Vac - but doing some runs does effectively the same thing.

 

So when i put pressure (10psi) onto the cartech with the mightyvac, I should see an increase in fuel pressure when that set center bolt is screwed in ?? I have a feeling my pump is bad becuase im not gettin an increase at all

-matt

 

nevermind - figured it out.

It helps if your vacuum source isn't coming from the MEVI line that already has a check valve on it disallowing boost to get through.

 

Yes, you should.

I would think even with a bad pump SOMETHING would happen.

 

Ah yes.

I'm glad you got it figured out. I spent all morning thinking about what could possibly give you these symptoms, and all I could think to say was that mine doesn't act that way.

 

He's getting a pressure increase, but only up to 60 psi and no higher, right Matty?

 

I blame maximase86 - he's the one that did the vacuum while I was doing the fuel lines.

 

something for discussion...sorry to slightly jack the thread but it looks like you sorted everything out...

say i am maxing out the A32 MAF with the 3.125 pulley and wanted to drop down to say a 2.87. could i use an FMU either cartech or Vortech to ramp up the FP on the top end to compensate for the MAF reaching its limit? i am not sure what JWT has to say about running an FMU on top of their ECU.

i am just wondering if hooking up an FMU into my setup will mess with the tune of JWT that is supposed to run at stock FP. like in the midrange when the FMU boosts the FP up while its supposed to maintain stock levels.

just looking for a way to get down to a 2.87 i guess. thanks.

 

In midrange with a 2.87" you are already into a decent amount of boost...

I'll be doing EXACTLY what you say above for the exact same reasons - Using the Cartech, which ramps FP according to boost, it should work fine.

I may get a drop in A/F ratios below 12.5:1 in the 3000-4500RPM range from the Cartech as far as A/F goes, but I expect the AFC can somewhat tune that out.

The big worry is the A/F at 6000+ RPM, where I'm maxing my MAF out and running lean. Lean is always worse than rich....so if I have to sacrifice some midrange power to save my engine up high, then that's life.

As far as JWT is concerned, they do not recommend and actually "forbid" using any other Fuel Management with their ECU's. But that's ridiculous of course, and probalby they only say that for liability reasons and the fact that they believe their maps are "perfect", which we know are not "perfect" in all cases....

I'll be Dynoing hopefully this Saturday, and that will tell us all how well this method works.

 

For a while I was using the Cartech to increase fuel pressure at high rpm to lower the afr below what the JWT ecu was providing. Worked great.

You can also lower afr (at WOT) across the board by increasing your base fuel pressure.

 

I am sofa king we todd did. I feel really dumb now. :P

We should still get up on the dyno next weekend.

S

 

can this be done with the vortech FMU or is there some feature that the cartech has that allows this to function properly?

 

I odn't believe a regular Vortech will work because it cannot be adjusted to only add FP at high boost, and it will cause the entire run to be rich.

A Vortech Super FMU would probably work.

I also heard somewhere about a "mod" you can do to the regular FMU <add a bleeder valve yourself> to make it work - but I haven o information or personal experience on it.

 

No..I went out for a ride and the fuel pressure is increasing past 60 very well but the thing is at idle when I put a boost pressure on the cartech Im getting NO response, but when i go for a ride and boost it goes uP ??? ??

-matt

 

Hmmm. That's interesting. I wonder if your fuel pump doesn't get enough voltage when at idle to be able to pump over 60 psi.

What fuel pressure are you getting up to, and at what boost pressure?

 

I just had the car out..Im gettin up to about 8psi I think maybe alittle less and its going up to about 80 psi of FP...Ithink maybe my belts loose. ?? Its hard to tell cause its soo quick

What fuel pressure do you guys get when your cruizing and not boosting ?? im at about 36 when cruizing..then any blip of the gas it goes to about 40ish then dropps down..when I let off...

the thing is when I boost, the Fuel pressure shoots up but shoots right back down when I lift up on the throttle...is that normal ?? sorry for all the stupid questions..

-matt

 

Everything you describe sounds normal. Now you need to have some dyno-tuning done.

Fuel pressure when cruising is going to depend on what your manifold vacuum is, but anywhere between 34 to 43 psi is about right if your base fuel pressure at idle is set to 34 psi.

It's very possible your belt is slipping. What size pulley did you say you had?

 

Here's the link where maxi-overdose mentioned about the bleeder valve.

http://forums.maxima.org/showthread.php?t=293549

 

3.125 ...any tricks I should know about gettin my Belt perfect...thats probably whats wrong

-matt