So I talked to the guys over at modular powerhouse today. (trying to get a different dyno for a reading) They of course, are booked through early november. Shiat. Anyway, they told me that a stock 5.4 block can safely handle 10 PSI. Now, the only reason I even post this is because they specialize in and pretty much only deal with 4.6 and 5.4 engines. (they do do the occasional 5.0) So, 9 PSI here I come baby!

 

Navi98,

I am going to say this one more time, just for the record because when it happens (and it will), I want to know you have been warned.
If you continue to run at 6lbs boost without an FMU using stock 19lb fuel injectors, you are going to destroy your pistons. If you increase to 9lbs boost, it will happen faster. The stock 19lb injectors can not keep up with the fuel demand. You will run lean and then things will happen. They will happen at WOT so it will be worse. The FMU should not change the way then engine runs in non-boosted conditions since it does not work until it senses boost. Perhaps you had yours installed backwards. Its not hard to do if the lines are attached to the FMU backwards.
If I remember correctly (check to make sure) looking at the FMU one of the hose attachment points comes out of the center back of the FMU. That hose should have a female fitting on the other end.
The hose that comes out of the side of the FMU should have a male fitting on the other end.
They can only fit one way on the fuel system but it is possible to attach the hoses reverse on the FMU.
The vacuum line is attached to the top and should be connected with a T to the line going to your boost gauge so you will know immediately if you loose boost to the FMU. There are instructions at the Powerdyne website on how to hook it up.

You should call whoever burned your chip for you and I'm sure they will verify it should be run with the FMU.

As far as NAVI fuel pumps go, I am not sure what you have. I think in 98 it was a 2V 5.4 engine. Later NAVI's got a 4V engine (32 valve) and they may have a higher flowing fuel pump.

Good luck.

WLF

 

I have that new 90` elbow I am installing tonight. I will try reattaching the FMU and see how well it works. Now, I know there is a difference in a mustang and and SUV, but why then can a mustang with 19 injectors boost 10-12 psi with no issue, but a truck cannot? The way it is setup currently, I have no detonation, no pings, no knocks, no rattles no nothing. Just running smooth as silk and fast as hell. While reading the data driving down the road, my 02's are reading exactly correct, maybe even just a tad rich at WOT. When I do go to the new pulley, 2.75", I will have the chip reburned and make sure then whether or not the FMU should be installed. I ordered the pulley today, will call dugan tomorrow and have them call diablo and write me a new program. Believe it or not , no one has ever had diablo burn such a program for a navigator.

 

you're playing with fire junior.

you should ONLY run 9 or 10 pounds of boost with larger injectors (42's) and MAF. that much boost isnt even safe WITH an FMU, much less without.

you might be one of the lucky ones, but chances are you wont be. just dont say we didnt tell you so when it blows.

 

OK, forgive the repetiveness of the mustang thing, I know that irritates everyone here, but its what I know. Then why can a 5.0 with 24lb injectors run 10 psi with no problem?

 

98Navi,
Just make sure when the bigger pulley is on,to test it on the dyno w/ a wideband air/fuel meter.Thats the only way to find any inadequacies w/ your fuel system.I would advise not going wot until the dyno,no matter if you were running 42# injectors.When you make changes,you better be sure your tune still applies to your setup.Other than that,you should be good to go.

good luck
Frank

 

FMU vs No FMU. Return vs Returnless. Adjustable Fuel Pressure Regulator vs Non-adjustable.

 

OK, the navi has a return system on it. I have the FMU but haven't reinstalled it (the electric fan thing didn't work out last night) I can add an adjustable pressure regulator no prob, so does that clear up the issue or leave more?

And I am going to order a new program for the chip. I am just considering what I want to have on it. I am leaving the country on a cruise the second week of november so I decided that is the best time to have all that done, while I ain't at home.

 

5.0's were built much stouter that modular motors. cast block and heads, forged crank, etc.......a stock 5.0 can handle a 175 shot no problem. try that with a modular motor and see what happens.....

if 10 people told me not to do something, eventually i'd get the idea.......

 

OK, called Dugan today, the chip was burned to have an FMU online and he said that it was best that I get it back online like 10 minutes ago unless I wanted a lightning block he had for sale for my fried powerplant after a couple weeks of that. Well,crap. It was running so good too. I ordered the high performance dual electric fan setup from Summitracing today. I know you all like Troyer, but from the picture he had posted his setup didn't look all that spiffy, and the Summit one has a one piece design. We'll see how it goes

 

FMU reinstalled, after an hour long fight with the fuel supply line spring release mechanism. What a biaaatch. It unseated fine, then popped back out before I put the FMU back inline, and I have to fight scream yell and cuss to get it all put back together. But, the good thing about it is, after a couple quick runs back and forth down the street, I am pulling a full 5+ pounds (not quite 6) of boost. I installed a 3 inch 90` elbow from the charger to the MAF. I bought the rubber plumbers elbow from lowes. (yeah, I am impatient and cheap) The fans I ordered next day air, so they'll be in tomorrow. I am hoping for delivery of the Crossdrilled/slotted rotors tomorrow as well. I already have the EBC pads and Caliper paint sitting and waiting.