what happens when you unplug the vaccum line going to the FMU and you boost? the FMU doesnt sense boost therefore doesnt up the fuel pressure therefore under boost you can lean out and byebye motor correct???

reason being my friend, (member of the org) has a supercharged Max and was getting it tuned and his motor is blown now. whats weird is #2,#4,#6 leaned out and the plugs melted. #1,#3,#5 are ok.

sorry to hear that cha ching

- Phil

Yes, this is exactly how it works. If the vacuum/boost signal is removed, the FPR will not up the fuel pressure when it sees the boost signal.

Man sorry about your friend. Anyone we know? How do you know it was disconnected?

it is Lynn(Lyt97SC)
i hope he doesnt mind me telling everyone...hehehe
he's running 3.125 pulley.

the guy isnt admitting fault at the moment so im trying to help him get more evidence. ie. calling Vortech. The guy keeps saying if it was his fault all 6 cylinders would be bad...not juss the front 3.

I don't know about that. Doesn't the 4-gens run one long fuel rail? Ie.. fuel comes in along one side, feeds 3 cylinders and then runs to the other side and feeds the rears and then out to the return?

If so, maybe the rears would lean out first(or whatever side gets fuel last). Plus it's not like you would keep hammering the motor until ALL the cylinders toast up right?

In fact, most blown motors only see one or two bad cylinders, but I don't know for sure.

Sorry I'm not too familar w/ the 4-gens fuel rail or firing order.

the firing order is 123456
usually what ive seen is #5 cylinder goes bad cause its the last injector on the fuel rail.
heres how it works, looking at the engine
1 3 5
2 4 6
fuel goes to 6 and ends at 5. When my motor went bad #5 was bad. I dunno...sounds like a poor excuse to say juss cause not all cylinders went bad so its not their fault.

I agree.

It's odd that the front side leaned out and burnt first. I'm at a total loss. Maybe something got stuck in the fuel rail? I guess if the rail got plugged, the first 3 would lean out first? wild guess

Why would the guy unhook the vaccum line?

Say, isn't this what Cheston posted on MaximaDriver.com about removing the vacuum hose to the FMU? It was supposed to make the FMU think that its always on boost and thus ups the fuel pressure. Is this what the topic is about?

What he told me was that they pulled just the front plugs and they were melted. He didnt mention the rears. I dont know if you or I misunderstood him.

He had the car running for a few days with the 3.125 and 12:1 FMU disc. He had played a little and drove it around with out any problems. He drove it to the shop for the tuning.

He told me, they did a base line pass with the 3.125 and 12:1 FMU and got 277hp with 10.5-11psi. It was very rich, so the tech who does the programing of the Racers Group "The Program" decides to tune via the ECU, he pulls the vacume line off the FMU and did a pull. This is when the melt down happend.

Now as most of us know even in a perfect situation the fuel injectors in the Maxima will not flow enough fuel at 100% duty cycle with stock fuel pesssure to support more then perhaps 250hp. This is why you use the FMU to raise fuel pressure.

Case in point, I30Krab, he has a SC I30 running a JWT tuned ECU. He does not use a boost referenced FMU. instead he uses 300ZXTT injectors. I have talked to JWT and this is how they recomend it be done with base fuel pressure.

In my opinion the tech at the shop performing the tuning of the Racers Group product made a fatal and uncalculated decision attempt to use base fuel pressure with stock fuel injectors for a high boost Maxima.

I would bet the tech doing the tuniing did not have any idea what size the fuel injectors were in a Maxima or what the base fuel pressure was. With out this information he could in no way calculate the effects of his actions.

I told Lynn to be sure to get coppies of all dyno pulls with air to fuel information. I gaurentee this will show that the motor went treminaly lean as a result of the vaccume line being pulled from the FMU.

It will a tough fight to get this shop to cover the cost of the new motor. If they do not want to help with the new motor I would recomend writing to the "Racers Group" and asking for assistance. Then try the local BBB. Then any trade orginizations that the shop may belong to. If you get no results them, get a lawyer.

Man... that sucks. Sorry it happened, Lynn.

3.125 eh? Too many people using me as a test subject for that pulley. I'm not going to say anything when I downsize.

------

Oh it happened at the Racer's Group? I remember Matthel telling me Lynn was getting the UNICHIP, but didn't remember when.

lol, when i read the post I thought it was going to be something else going wrong with your car...I was like "jesus, this man has terrible luck" But even tho it sucks at least it was someone else for once,

Good luck to both of yaz on keepin' the fast rides on the road...

PJ

Man that really sucks but I know how he feels (I too lost a motor that I spent over $1k on engine work ). Assuming he keeps the car, this would be a good time to try a VQ35DE swap. On car-part.com I've found 3 of these motors (pathfinders of course) for $900-2000. Given some 8.5cr forged pistons and bigger injectors like 370cc or 550cc he could make all the power the tranny could handle. Otherwise a rebuild with lower compression pistons is going to cost the same amount anyway.

Yup!

Id say a 2000 or 2001 motor and use some low CR pistons. I think his good friend could help him get a set??????? The 2000 & 2001 internals are suposed to be improved over the 4g internals. I would bet the con rods are stronger. With those 9:1 forged pistons and 14psi, that car would move!!!

NOOOOO! That is referring to disconnecting the hose for the HOBBS switch to keep the inline fuel pump always running... NOT THE FMU!

Whew! Now I can detach the hose again...

Uhhh I had the 3.125 b4 you Kevving...

I didn't know because you didn't tell me! You were using me to find out if the 3.25 was stable or not!!!

Nutin' but love for you.

heeheeheehee...it's all good Kev...enjoy your holidays, pass along my wishes to Jane.

so now you think your special delio? don't forget cha ching doesn't beat on the car daily, as would a dyno run or 1/4mile run would. 3.125 is safe, as long as you keep the fuel running

Happy Holidays to you also my boosted buddy.

Hey pedoPHILe! How do you know I don't beat on my car? Or maybe I have something else in the car..... that's why it hasn't blown up yet.

a bible?

buwahahahahaaaa

Four leaf clovers and Rabbits Feet too.

SuDZ

Holy water injection

LOL,

So this is where all the boosted people are..

so what explaination is there for only the front 3 cylinders melting? hummmm

they were lucky!