[maxi-overdose]

iTrader: (3)

another EGT question:

recently I noticed that my EGT has gone higher than before. It may be because that I drive harder now. But it still worries me and seems it wont stop. For example, I floored the pedal at 3500, 4th gear, 80mph and downshifted to third. At 110mph, 5500rpm, I saw 810 celcius of EGT! Seems like it just wont let me pass 100mph.

I pulled my O2 sensors 2 weeks ago. The one right after the pre-cat on the ypipe looks black. But the one right after the rear bank is really white. I checked the plugs and they seems to be fine. The insulator is a bit brownish and the electrode bridge on the top is dark gray. am I running lean? can I tell by the O2 sensors?

What do you guys think?


lack of fuel?
1.Boost bleeder valve on the FMU is bad?
I have installed a vortech bleeder valve onto the fMU to leak out some boost. But now it is close all the way and I am not leaking out anything, but I am still getting high EGT like the example above. I will take off the bleeder valve and see if it gets better.

I loose the bleeder valve all the way before. the fuel pressure became lower but the EGT reading is still the same. weird....


2.fuel pressure??
I highly doubt it....fuel pressure is there. I saw 80psi of fuel when I floored it at 4th...it went up to >100 if I downshift 2 gears.


3.injectors??
why does my rear bank O2 sensor look lean while the front one looks ok? For front bank, I pulled the O2 sensor right after the pre-cat instead of the one right after the exhaust manifold. Is it possible that something makes my injecotrs in the rear cylinders inject less fuel into the engine? I am already getting high fuel pressure...

do I need more to deliver adaquate fuel to the rear injectors?


4.Fuel pump maxxed out!
how much pressure can stillen inline fuel pump handle? again.....I still dont understand fuel pressure vs fuel delivery. I thought more pressure = more fuel and why more fuel pressure will lower fuel delivery??



exhaust is too restrictive
1.cat-back/stock muffler is too restrictive.
I just got a greddy cat-back I need to get used to the noise and power gain is.....anyways, I will leave that to another thread.

2.cat's clogged?
I checked and it seems to be fine. stock cat shouldnt be that restrictive, right? Do I need high flow cats?



thx guys for reading this long thead and help me.

IceY2K1

iTrader: (3)

All I know is that the reason your REAR bank is running leaner then the FRONT bank is because of the direction of the fuel rail supply.

246-->Fuel out
135<--Fuel in
Front
--of--
-Car-

So, the injectors with the most fuel to least fuel(rich to lean) would be 5-3-1-2-4-6.

You are seeing high fuel pressure on your gauge, but apparently it's NOT adequate to the injectors on the rear bank. Why I don't know, but a fuel rail pressure tester should tell you, right? Otherwise, my *GUESS* is that the 02-sensor on the rear bank is fooling the ECU into triming the fuel. Try replacing the rear bank 02?!?

Jeff92se

iTrader: (82)

Wow! Be careful!

Chunger

iTrader: (1)

S/b in open loop mode so that probably isn't it.

IceY2K1

iTrader: (3)

ejj

iTrader: (5)

Where is your EGT probe located?

[maxi-overdose]

iTrader: (3)

thx Alex. cylinder 6 plugs seems fine. but I took it out after I idle the car for 1 minute or 2. I dunno if idling the car too long will make the plug looks different.

I pulled all other plugs and they seems fine. But I should boost the car, then shut it off and pull the plugs. or strap her onto a dyno will be even better.

weird thing is that my ECU never throws any code abour rear bank running lean. hmmm...maybe I have a stupid ECU.


maybe it is too much pressure for the stillen inline fuel pump and it cant handle that much?

[maxi-overdose]

iTrader: (3)

what's s/b?



on the ypipe between the front and rear bank

trying my best

BlackCat

iTrader: (6)

s/b = should be

ejj

iTrader: (5)

So wouldn't that mean that you're only getting EGT readings for the front bank...and therefor you don't know much, or anything about the rear bank's EGT's?

IceY2K1

iTrader: (3)

I'd expect the plugs to show symptoms vs. the 02-sensor.

ECUs can be tricky and even ignore problems until it's too late. My suggestion is to borrow Kevs' OBD-II software, take a few scans on these high EGT runs, and send me the data files to look at. I'm not sure I'll be able to tell anything, but it's worth a shot.

I would expect to see your fuel pressure drop on your gauge. Another *GUESS* is that maybe your injectors need to be cleaned or for some reason one or more of the rear bank injectors are going STATIC from the 110+psi fuel pressure. Like I explained before, I'd expect the FRONTs to fail first due to super high fuel pressure, but maybe the REARs require a higher duty cycle then the fronts due to having less fuel pressure. So, the higher duty cycle and 100+psi fuel pressure *MIGHT* be causing them to lock-up, which would cause a lean condition.

Last, I'd like to see your OBD scans if you can get them, so I can observe your front vs. rear bank 02-sensor readings. Although, you're going open-loop, they still measure/display current 02 voltages just no trim values.

[maxi-overdose]

iTrader: (3)

thx~


I think the temp reading is based on mixing of both banks. I understand the probe will read the front bank more than the rear because of the flow. but I believe the super hot exhaust gas from rear bank can also contribute the high EGT. what do you think?



let me see if I can boost the car and pull the plug right the way...see if I can do it this weekend.


I talked to Kevin today about this. we plan on going to a dyno so we can see how much gain we got on our cat-back (his 3" and my 2.5"). lets see if I can borrow his lap-top and OBD adapter during the dyno run. I will be able to see my AFR on the dyno day. dyno God.....

hmmmm.....how much difference of pressure do you expect to see between front and rear? I dont think there's a big difference between front and rear. Say if I am pushing 100 psi to the front cylinders, I doubt that I will see the rear fuel p. dropped to 60psi. But without any proof...I am just guessing

I will try to get that on the dyno day. You want the O2 sensor reading right after each bank, right? not the one after the pre-cat, eh?


thx for your help, really appreciate it.

IceY2K1

iTrader: (3)

Kev and dyno. Kev and OBD scans. He's been saying that for 10+months now.

I don't know either. Just know it's enough to cause the last cylinders to burn up first.

Not sure I'm helping, just brainstorming here. I'm not sure what you mean by "You want the O2 sensor reading right after each bank, right? not the one after the pre-cat, eh?". If you're referring to the OBD scanner, it logs ALL of them at once. Just scan and save the dat files and email them to me. I'll look at them and if I see anything funny, I'll graph them in Excel to help see things better.

[maxi-overdose]

iTrader: (3)

he's a busy man

I am not too familiar with OBD scanning....I thought you can select individual O2 sensor and monitor their voltage. That's why I said that I will monitor the O2 sensor right after each bank for comparison.


I will collect the reading of all the O2 sensors and keep you updated.


thx again~

ejj

iTrader: (5)

I doubt that. The exhaust is moving much too fast. I think you're just reading the front EGT's (which I am too)...but if your front bank is lean, odds are your rear may be even leaner!

IceY2K1

iTrader: (3)

Oh sheeeeeit!

Front bank is the bank to monitor for 4th gens......5th gens. should be watching the REAR bank.

ejj

iTrader: (5)

Fuel goes into the front bank first on 4th gens...

IceY2K1

iTrader: (3)

Not according to the FSM and I'm 90% sure not on the 4th gen I helped add a FMU too.

Correct me if I'm wrong though.

ejj

iTrader: (5)

FPR is on the back bank...inlet to the fuel rail (hard to see in the pic) is on the front..

Unless I'm misunderstanding something...

IceY2K1

iTrader: (3)

That looks different. Are those lines that are running to the drivers' side hooked to your FMU or something?

Let me do some digging.

UMD_MaxSE

iTrader: (1)

the 5th gen has a fuel damper on the return side that sits right off the fuel rail. It looks like a fpr, but the actual fpr is on the feed line. The fuel is fed into the front bank on both 4th and 5th gen as far as I know.

ejj

iTrader: (5)

Yes. The rubber line coming off the rail at the top of the picture is heading to the aftermarket FPR. The line right above that, which has another rubber line heading to the drivers side is the return line.

[maxi-overdose]

iTrader: (3)

hmmm...but I am pushing a lot of fuel into the engine though...

I know if the car is running really really lean, it will feel slow and the engine will be bogging (happened to me before when the fuel pump wire was cut) But my car is pretty smooth....according to butt dyno.


worse case is that it is running at a 15:1 AFR, the car would still feel fast....and it is going to kill my engine in no time.

ejj

iTrader: (5)

Maybe injector problems? Maybe you're at 100% duty cycle and the extra fuel pressure isn't getting it done?

IceY2K1

iTrader: (3)

Actually, the fuel damper is on the FRONT bank and the fpr is on the REAR bank.

On 4th gens. fuel is fed to the rear bank, ejj has his backwards.

IceY2K1

iTrader: (3)

Had to figure out how to shrink a PDF down below 50K.

UMD_MaxSE

iTrader: (1)

hehe... thanks

IceY2K1

iTrader: (3)

NP...you just started to make me second guess myself. Hehe.

Anyways, as soon as Sprint gets his website back up, I can PROVE the rear bank feed and front is return for the STOCK 4th gen fuel rail, which is OPPOSITE to the 5th gens..

ejj

iTrader: (5)

Huh?

That looks the same as the 4th gen, except we don't have a fuel dampner on the front of the rail.

Street Reeper

So on the 4th gen should I mount my EGT on the front bank like maxi?

IceY2K1

iTrader: (3)

No offense, but I think you've got yours backwards. I'm waiting for access to a FSM to know for sure.

ejj

iTrader: (5)

How could I have it backwards? The FPR only can bolt to 1 end of the fuel rail...and the fuel rail can't go in backwards.

IceY2K1

iTrader: (3)

Only thing I can think of is that you moved the feed fuel line from the back rail to the front rail?

ejj

iTrader: (5)

The car won't run (or start) if the fuel lines are backwards...

http://forums.maxima.org/showthread....ght=fuel+lines

I really do have it right:



This is going to be a PITA to explain, but here's a try:


On the right you see the FMU as SARD FPR. The line going from the FPR clearly goes to the rear bank of the fuel rail. Passing under that line you can see the intake line to the fuel rail. Its got the FP sensor in it. That's run directly from the fuel filter to the fuel rail.

My fuel rail is set up the same as my mom's 97 GXE, which has a stock fuel system.

IceY2K1

iTrader: (3)

What does a fuel injector care which way the fuel is flowing? As long as the FPR is downstream, it will work either way.

Yes, yours is setup the same as a 5th gen. I can clearly see that, but can you get a picture of your moms' GXE or another stock setup?

ejj

iTrader: (5)

The injectors don't care, but the FPR does. FPR's are on the rear bank in a stock setup...again, look at the fuel rail. The FPR can ONLY bolt to the rear for us, because we don't have a fitting for the dampner on the front bank.

It will be hard to see...but if you can pick out the stock FPR, you'll see its on the rear bank:

IceY2K1

iTrader: (3)

Alright, I got it. I see the FLANGE you were talking about. I didn't get what you meant by "look at the rail" when your aftermarket FPR was elsewhere. I see the FPR bolts to the rail on the rear bank.

Those pictures are all of a '97, right?

ejj

iTrader: (5)

Yes

123456789

Y2KevSE

iTrader: (13)

Fuel flow for 4th gen and 2k-2k1 are different. 4th gen enters from the side closest to the cabin and 2k-2k1 enters from the side closest to the front of the car.

IceY2K1

iTrader: (3)

That's what I've been saying all along.

Only problem is that, ejj's pic shows the FPR attached to the end of the fuel rail exiting the REAR bank.