Tuning Help

NewfoundlandDud · 06-26-2008, 06:42 PM

Alright, a little background.
In April I pieced together and installed a S/C "kit" on the Maxima.
Basically I rounded up most of a Stillen/Vortech kit with a few extra's such as Matty's V1 plate, etc.

On the first start-up I blew-up my AEM FPR, so I took that + the BEGI FMU out and installed the Vortech FMU that came with the original kit.

I had a pretty good basic tune with the Vortech while I waited for the AEM FPR re-build kit to come (~14 AFR before boost, ~11.5 in boost). I know it's not ideal, but it was "close enough" with the basic stuff plus the NEO.

Anyway tonight I re-installed the AEM + BEGI setup, and now I'm having problems. I had a Rough tune going with ~12 AFR through the whole boost range, and again ~14 before boost(Dipping to 10 as soon as it sees boost).

The problem comes when I turn the car off. It doesn't start!!
If I turn it over a few times one-after-the-other, sometimes it starts, but it's labored.
I also had a lot of trouble adjusting the fuel pressure trying to use both the FPR and the FMU which has a "Baseline fuel pressure" adjustment in itself.

My fuel gauge goes to the maximum reading (100psi) when the Auxiliary "T-rex" pump pressures up. (When the ignition is turned to "ON").
Whether I try to start it then, or if I back off the FPR + FMU completely until the gauge slowly creeps down to 50 psi, it doesn't want to start either way.

I don't know if the fuel pressure is too high when starting, or if it's being choked, but it isn't working either way. I also turned the NEO corrections off to try, and no luck.

If someone can help me by either giving me a starting point, or maybe tell me what's going wrong, I would really appreciate it. This is the first time that I have tried to tune my car, so I would appreciate any assistance.

Thanks.

NewfoundlandDud · 06-26-2008, 06:47 PM

So I have 4 places to adjust:
1) Fuel Pressure on the Fuel Pressure Regulator (AEM)
2) Fuel Pressure on the Fuel Management Unit (BEGI)
3) Rising Rate (With Boost) on the BEGI
4) MAF Signal with the Apexi NEO

I'm having problems getting the base fuel pressure to correspond to the adjustment on the FPR and FMU set screws to begin with, it seems like it either wants to sit at ~60psi or ~100psi, but the AFR does change, so maybe both my gauges are crappy.

The big problem though is the not-starting thing.
Any advice there would be awesome.

kzoosho · 06-26-2008, 07:07 PM

well for one, whats your base fp? Also if you are getting 100psi once you turn the key on thatll keep it from starting.

NewfoundlandDud · 06-26-2008, 08:38 PM

Hard to say what the correct FP was, since I have a gauge attached to the AEM FPR, and another in the gauge pod.
At one point the gauge on the FPR was just stuck at 100psi, even when the car was turned off, while the gauge inside said 60psi.
Even when the gauge inside was giving a reading, it was all over the place.....I would turn the ignition to "ON", the pump would sound and it would go to 100psi. If I let it sit for a minute, it would slowly fall to below 50psi, then if the car started it would go to lets say 70psi. While the car was started (showing 70psi), I could back the set screws out on the regulators, or tighten them down, and it didn't have any effect.

The car wouldn't start at 100psi or 50 psi, or 70.....??

Anyway I ended up re-installing the Vortech FMU and tuning back to that.
But I would like to know how to do it correctly so that I can attempt it again when I have some time (And don't need the car to get to work the next day).

*The Wizard* · 06-26-2008, 09:33 PM

Curious, why did you pull the Vortech FMU for the BEGI? Also, what size disc is in the Vortech FMU? Does the BEGI have interchangeable discs like the Vortech unit?

IMO, you're having problems because you installed two items at the same time that both have adjustments. ie too many variables to consider.

Here's what I would do to troubleshoot your situation.

Pull the AFPR and put the stock FPR back on. Make sure your Maxima runs like it should with just the BEGI FMU. If so, than you know your adjustments/problems need to be made with the AEM AFPR. If it doesn't run well, you know your BEGI FMU is at fault. Either make the necessary corrections/adjustments, or pull it and put the Vortech FMU back in.

Once you have that figured out, reinstall the AEM AFPR and adjust as necessary. If you still can't get everything ironed out, you might still have a bad/defective AEM AFPR.

Simplify your situation and maybe go with the AEM AFPR and the Vortech FMU, this will take one variable out of the equation. ie less headaches.

Also, I forget. What size pulley are you using, and what size injectors are you using? I may or may not change some of my above recommendations....

NewfoundlandDud · 06-27-2008, 04:21 AM

The BEGI FMU has an adjustable rising rate (Set screw) instead of the discs that the Vortech uses.

My issue was that at idle/low RPM, I was adding ~20% to the MAF signal, which told me that my baseline FP was too low. Also, while boosting I was in the 9's so I ended up taking ~20-30% out of the MAF signal with the NEO. I wanted to get a more "mechanically" tuned fuel map to start with (i.e. less adjustment on the NEO), so I needed more adjustment.

The Vortech FMU doesn't have a FP adjustment, and I beleive it just has the 8:1 disc in it. I decided to go with the other setup as a "complete unit", since the previous owner of the kit did just that. (I beleive that he left the stock FPR on the car, and just used the AEM & BEGI in series).

To answer your other Q's, I'm running the 3.125" pulley on stock injectors.
I hit about 8-9 psi in 3rd (Auto).

**mtrai760** · 06-27-2008, 09:23 AM

Are you pulling the vacuum line off of the BEGI before adjusting it's fuel pressure? If not, that is your problem.

I am running 370cc injectors, Z32 MAF, AEM FPR, and Cartech FMU. No AFC or other fuel controller. Here is how I make adjustments.

To start off with, loosen the fuel adjustment stud on the Cartech until it is not adding any fuel pressure. Start the car and get it fully warmed up.

Next, set your base fuel pressure on the AEM. I am running at 34 PSI.

Next, with the car still running, pull the vacuum line from the Cartech. Now you are ready to adjust the fuel pressure that the Cartech will be adding. Tighten the Cartech until you see the fuel pressure just start to rise. This is the fuel pressure you will be adding once you start to boost. Now set the fuel pressure you desire. Once that is done, plug the vacuum line back in, and your fuel pressure should go back to the base pressure on the gauge.

Hope this makes sense to you, if not, let me know or send me a PM.

*The Wizard* · 06-27-2008, 09:26 AM

Quote:

Originally Posted by NewfoundlandDud

The BEGI FMU has an adjustable rising rate (Set screw) instead of the discs that the Vortech uses.

My issue was that at idle/low RPM, I was adding ~20% to the MAF signal, which told me that my baseline FP was too low. Also, while boosting I was in the 9's so I ended up taking ~20-30% out of the MAF signal with the NEO. I wanted to get a more "mechanically" tuned fuel map to start with (i.e. less adjustment on the NEO), so I needed more adjustment.

The Vortech FMU doesn't have a FP adjustment, and I beleive it just has the 8:1 disc in it. I decided to go with the other setup as a "complete unit", since the previous owner of the kit did just that. (I beleive that he left the stock FPR on the car, and just used the AEM & BEGI in series).

To answer your other Q's, I'm running the 3.125" pulley on stock injectors.
I hit about 8-9 psi in 3rd (Auto).

If the previous owner left the stock FPR in place, then the AEM AFPR wasn't doing anything.

With your mods, there is no need for an AFPR. I'd leave the stock FPR in place, pull the AEM AFPR, and reinstall the Vortech FMU for a trouble free setup.

*The Wizard* · 06-27-2008, 09:29 AM

Quote:

Originally Posted by mtrai760

Are you pulling the vacuum line off of the BEGI before adjusting it's fuel pressure? If not, that is your problem.

This is key info right here. I had to do the same thing back when I had the Vortech SFMU.

borka · 06-27-2008, 02:19 PM

I am running 3.33 pulley the aux pump and vortech fmu with i believe a 8:1 disk, and i have to deduct 30-40% fuel on my vafc2 to reach 11.5-12afr. so i will be getting a 6:1 plate and hopefully this will roughly lower fuel delivery across the board, and i can always fine tune with the VAFC2.

why are you using all these fuel regulators? just swap the plate in the vortech and be done.

i believe you need an afpr only if running larger injectors to reduce fuel pressure at startup.

mooseq30 · 06-27-2008, 02:45 PM

Read my PM and maybe it will help!
As well I think the idea of so many fp adjusters is just too much, like said before me; eliminate everything use stock fpr, with fmu 4:1 is best to my knowledge and tune from there!

**mtrai760** · 06-27-2008, 02:58 PM

The Cartech FMU does not control fuel pressure for anything but boost. It does not affect fuel pressure under normal driving conditions. It is the same thing as the Vortech FMU, only better. You can adjust the rate at which it adjust fuel pressure two ways, VS. the vortech where your stuck with changing disc out.

mooseq30 · 06-27-2008, 04:20 PM

I agree I have the cartech fmu, bought it used and it is still working perfect from day one till present! It has an onset adjustment but its best left at 0psi above NA, or thats were I have it set and it works great.4:1 ratio with max of -13 on the neo afc!

NewfoundlandDud · 06-27-2008, 04:25 PM

Thanks for all the info guys.
I'll be running the Vortech FMU for another little while now until I get some time to install/tune the other setup.

mooseq30, thanks for the informative PM. I'll get back to you when I know more.
To answer your question, the dec air wasn't touched on the NEO, so it's set to the defaults.

I'll report whatever I can when I start back at it.
So I should remove the stock FPR??

**mtrai760** · 06-27-2008, 04:30 PM

If you have the stock FPR, then you don't need the AEM.

mooseq30 · 06-27-2008, 07:47 PM

no aem needed unless u change ur injectors or remove the stock one, so I say leave the stock one ditch the aem!

*The Wizard* · 06-28-2008, 11:51 AM

Like I said before, IMO there is no need for the AEM AFPR with your current setup, and considering you're still on stock injectors. Why complicate things?

Leave the OEM FPR in place. Ditch the AEM.