hey guys:

please try to stay on topic. This thread is obviouslyvery important to me.

PM Each other ify ou want to talk about the ups and down of bike sales.

Thanks,
IanS

 

No offense bud,but perhaps letting someone else drive your car down the track to see what they can do?

As far as the dyno numbers coming in, since you've virutaly exhausted all other options, look for the un-obvious like:

A big rat or small cat stuck in your exhaust pipe
Stolen weights from the gym that your forgot in your trunk
Folded flex section in the y-pipe
Tranny slippage
Clogged fule injectors

Maybe you just got a lemon.....

 

schedule*

 

Does anyone know if engine compression would have any correlation to the amount of vacuum, ie. lower compression causing the engine to make less vacuum?

 

ebmorgan also drove it down the track, and the best he ran was 15.0.

mtrai760 was watching me race, and noticed I was hooking up fairly well, and brake-launching correctly.

Already took the exhaust system (not the muffler, but everything else) apart. Flex section is good. i replaced my B-Pipe with a Stillen B-Pipe 2 weeks ago to get rid of the crush section.

And I don't think a clogged muffler would cause a loss in vacuum.

Clogged Fuel injectors would make my FP go down. My FP is between 40 (idle) and 70 (full boost). From what I understand, this is pretty normal.

the only weight in the car was my amp rack and 1 10" Sub. that comes out to about 100lbs (MDF Amp Rack/Box). that wouldn't cause this kind of loss, and it wouldn't matter on the Dyno.

The compression question is interesting, but the ODBII scan showed that my engine was running pretty well.

Still something I may try.

IanS

 

Interesting.

I looked at my plugs today. They look brand new.

Beyond that, they are BKR6E - 1 step colder.

I don't know why I thought they were 2 steps colder.

Just for fun, I gapped them to .044 (stock) and drove around.

I know I'm imagining things, but it looked like I hit 9 PSI.

By the way, the V1 usually hit 1lb less boost than the V2.

So I should be at 9PSI.

But my vacuum is still low, and both my Dyno and track times sucked.

*sigh*

IanS

 

Yes, 100lbs will make a significant difference in way your car performs. It's not .1 for every 100lbs. It's more like .2-.3 seconds and 1-2mph. And your wheels, PLEASE tell me you are NOT running those tanks at the track. If so, you are loosing a solid .2-.3 with the wheels. The poor gearing of the auto takes it's toll mostly from 0-40. When you add big heavy wheels and more static weight, the auto has a harder time moving the heft than a 5 speed. I can launch at any rpm I choose, you're stuck with a very small available range. Your vacuum is still fairly low, but right off the bat, I can see two things that are sucking out life out from your car. I could see low 14s which would be pretty good for a auto SC.

Dave

 

He was using 15in steelies at the track...

 

I oculd have sworn i already said that earlier...oh well, I'm too lazy to read back and check.

Matt, good news on the MEVI's. I'll tlak to you about it when I drop off that "thing" to you later this week.

IanS

 

I would try a compression leakdown test as opposed to the normal dynamic compression test. The compression leakdown test allows you to measure the leakage past the rings and valves as well as listen for leakage at various points to determine what is broken.

Have your valves ever been adjusted? Have you checked your brakes to make sure they are not binding on the caliper?

 

I think it's a timing issue. Have you seen what the timing advance is at full throttle? It seems like an awefully low trap speed to me. I hit 106 MPH trap speed in my WRX at only 250 WHP and 110 MPH trap speeds at 311 whp. Granted, it's quite a bit lighter than your car but still, it seems like you should be hitting 100 MPH trap speeds.

 

I thought the curb weight of the WRX was over 3000lbs.

That would make it as heavy as a Maxima.

Unfortunately if it's the timing there's not much I can do . The timing is not adjustable in the 4th Generation Nissan as i understand it.

I was looking at the factory FSM, and timing (at idle) is supposed to be between 13-17. I'm at 15. Seems just about right.

 

Curb weight on the wagon is 3180 although I got mine down to almost 3000 lbs by using lighter components (alluminum, titanium, and chrome-moly). See? that's what I'm saying. I understand times could be traction limited but the trap speeds is what concerns me here. It should be over 100 MPH for that kind of power (which is VERY respectable). Timing is adjustable via a variety of piggy back systems. I used the Unichip on the WRX but Greddy also makes an E-Manage which should do the trick and can be had with optional boost module. You can fine tune your fuel curves and tune your timing curve with it using laptop and dyno with wideband O2.

 

There are no chips out for the Maxima. There is the JS unit that MardisgrasMax uses that cost well over $500, and the JWT ECU that cost $600. Not worth it to me right now when I can get a 5-spd conversion for a little bit more, and my timing is apparently perfect anyway. The JS and JWT's would only help me if I go with more boost (smaller pulley), to retard timing and prevent detonation, I think.

Also, my fuel is tuned using a Cartech Adjustable FMU and a wideband O2 on a dyno to 12.1:1 across the band.

My A/F is perfect, and my timing is perfectly within specs. Why would I want to change it?

Next thing I'm doing is re-replacing my TB, EGR, and Y-Pipe gaskets, Putting in a high-Flow Stillen exhaust, and doing a compression test.

Later this year I may get an APEXi FMS and tune the fuel even more. but I really don't think fuel is my problem here.

And there is the possibility I could have a cat stuck in my exhaust. i tore apart my Y-Pipe and cat and b-Pipe recently, so the only place left a clog could be is the muffler itself.

IanS

 

I feel your bad Ian...literally.

 

I sincerely doubt your muffler is the problem. iuf you want to test go to the track and just unbolt the muffler to see if your trap speeds rise accordingly. Your AF mixtures are perfect which is good but how did you check your timing specs? I assume you checked your base timing but that is not indicative of what the ECU may be doing under high boost and high load situations. It may very well be pulling timing a significant degree especially onder hot track conditions. I see as much as 12 degrees pulling of the ECU timing on the WRX since the ECU is very conservative. Now an ECU that was never programmed for boosted conditions may very wel be doing the same thing. On an SC Type R I saw about 40 whp gain from fine tuning fuel curve and timing mapping. Now the fuel curve made a difference but about 30 of that whp gain was simply from advancing timing at high RPM. On the WRX I see about 28 degrees timing advance (tuned with Unichip) at high RPM under full throttle.

 

Interesting theory.

howabout this:
Send me $800+ and gas money to Cali to have JWT make an ECU especially for me, and I'll do it. Oh yeah, need vacation time from work paid for, too.

Just kidding.

The funny thing is that the previous owner of my SC blew his engine while JWT was making an ECU for him, on their Dyno.

I'm not sure, but I don't think JWT changed the timing all that much. It's more fuel pressure levels, etc.

The timing on the Maxima is not really advancable. (Once again, as far as I know)

I really don't think it has anything to do with timing. It's obviously something else, because the vacuum gauge reads low at idle (an obvious symptom of whatever's wrong), but the timing is showing a perfect within spec reading.

At high boost, my boost Gauge reads 8-9PSI, which is perfect. Wouldn't it show quite a bit less if my timing was being reatarded? (I'm really asking, I honestly don't know....I do know timing affects vacuum, but does it affect boost?)

IanS

 

Time to buy as 2k3

 

The ECU ignores the knock sensor in closed loop mode on a 4th gen Maxima.

 

As I said I'm just offering suggestions. If you want to pay me and drop the car off I'll be happy to look at it and find your problem. As for timing yes it is programmable at the map using a Techtom rom board and yes it makes a HUGE difference in power especially if the ECU is trying to correct something. Now someone mentioned the ECU ignores the knock sensor at full throttle BUT some knock sensor detection may be causing the ECU to alter the timing map at part throttle and such ignition changes also do change your full throttle maps on many ECU's (not sure on that year Maxima). Go ahead and continue to look for your leak which could very well be your problem but I think there is more power there even if there is a leak. I'm VERY dissapointed at 14's out of an SC Maxima. That's pretty darn slow (no offense to anyone). Such a great motor and so much power and torque I would think it'd be worth some 13's at least.

 

One word: Automatic


That's why.