I30tMikeD

iTrader: (8)

I either have the weakest butt-o-meter in history, or the dyno I went to was messed up. The acceleration feel good up top. I actived the VI numerous time while driving and took the car out to 7K in 2nd a bunch of times. There was one time that I don't think the VI opend, but besides that the car seemed to pull really good all the way to redline. Maybe it's just been messed up for a while and that is what I am used to.

96sleeper

iTrader: (4)

Go to radio shack and buy a pack of 470k resistors (I think that is the right one) and unplug the connector on your knock sensor and jump the two wires with a resistor. This will give you full timing advance. Then check your butt dyno. Its a cheap way to avoid spending $100 on a knock sensor that wasn't needed.

BEJAY1

iTrader: (19)

Guess, I'll bring my manometer and infared pyrometer along too when we hook up. In addition to the Auterra, Palm, and both ECU's...

Oh, just for giggles check that airfilter immediately. I clogged my K&N with dirt & mud so bad it caused me to run rich and blew out all 3 of my O2's.

Dave B

Dang Mike, I'm sorry to hear about your troubles. I'm at a loss with what is happening on your car. Just curious, is this the same dyno Neal uses? If so, that dyno reads pretty low. Neals numbers are artifically low as are some of the other dynos I've read about coming from that place. I'd recommend doing a vacuum check, compression, and yanking the cat to look and see if the bricks are intact. While I haven't dynoed with my JWT ECU, my power doesn't really drop once 6000rpms is reached:



Mods at the time were an intake, y-pipe, MEVI, and B-pipe. I plan on dynoing with the JWT ECU once Fall rolls around.

The fact that your Summit RPM switch didn't activate is further proof that none of these RPM switchs are perfect. That's why I run a manual VI switch with my Harlan just so I have total control on the dyno or at the track.

I too have gotten the itch to sell all my mods and get rid of my after going to the track and getting pitiful numbers on occassion thanks to the Summit switch. Overall, I'm still happy with my car and I plan on keeping it for a long time. I've pretty much given up on getting a used G35 sedan because the prices are still high and I'll get basically nothing for my Maxima. I figure I'd have to cough up about 18K to get the G35 after selling my Maxima. I've pretty much decided to buy a 98 Cobra (~10-12K) and make that my fun car. I'll probably get rid of the MEVI since I won't be racing the Maxima much. I'll remove the wing on the Cobra, lower it with Eibach/Koni, add 4.10+ gears, X-pipe, intake/MAF, and some other basic mods.

SR20DEN

iTrader: (7)

Are you using the injectors that came with the engine? Could be a bad one.

Check the fuel pressure too.

This thing needs more fuel. Get that situated first.

And once you approach 13.5+ AF on the dyno the engine heats up quicker and can be less consistant, especially when you start the runs from 2000 rpm.

I30tMikeD

iTrader: (8)

I've got a pack of those resistors and two extra knock sensors laying around so that is no big deal.

I30tMikeD

iTrader: (8)

It's a not a dyno that Neal has ever used. The guy there did say that they used to get this 400whp SC maxima in there sometimes....

It may not be the rpm switch, it might be a canister problem. When I remove the tube going from the canister I don't get that vacuum release like I should. The VI works everytime when the car is not under load, so that makes sense that it would be that my canister is not holding vacuume.

Dave B

Yep, sounds like it could be the vacuum tank. I've been considering on getting an OEM Nissan one. Mine has been fine, but my plastic vacuum tank is showing signs of warpage.

krismax

iTrader: (15)

Did you plug that barb on the bottom of the TB?

I30tMikeD

iTrader: (8)

yep, still don't know what it does though....I think it might be something for the EGR system.

deezo

iTrader: (3)

Mike, that's what I was thinking also.

Dave, I'm using the OEM tank from a 2000 Max. I'm going to mess around with it and see what I get.

I actually have another check valve that I bought. I'm going to use it to see what happens. Jeff92se actually recommended me to use it when I was having issues last year.

I30tMikeD

iTrader: (8)

Run the car for 30 sec, remove the hose going from the canister to the MEVI and see if you get vacuum release.

deezo

iTrader: (3)

This always confuses me. If the vacuum releases, that means it's working right?

Dave B

Yes, just undo the vacuum line from the tank to the solenoid. You should here a pressure release.

I30tMikeD

iTrader: (8)

If I replace this canister it will be my third one. Neither time was there visable problems with it, I just think the check valve inside stoped working.

I30tMikeD

iTrader: (8)

I don't think this is related to my dyno issues but....http://forums.maxima.org/showthread.php?t=334869

Nealoc187

iTrader: (23)

I think I've got a sticky check valve in my Napa vacuum tank too, I tested whether or not I have any vacuum stored after a 30 second idle and I've got none. However my MEVI will open when in neutral just blipping the throttle up, but under load it doesn't always open, in fact most times it does not. I've never had the summit switch not light up correctly (unlike the harlan which did weird flashes when it got freaked out) but even. So I think I've been pointing the finger in the wrong place when it came to my recent MEVI problems, I think mine and mikes are both vacuum canister related. This does not however answer the question of why mikes power falls off so badly as he gets into the upper RPMs.

As can be seen from the dyno, mike makes GOOD peak torque, it's just that it falls off like a rock at 6000rpm or so. Dynos calculate HP from the torque they measure and the RPM they measure it at. So it's definately NOT the machine he dyno'd on.

One thing had occurred to me which I mentioned to mike, and this will sound really stupid, but since mike wasn't the one driving the car on the dyno, it's possible that the guy with his foot on the gas instinctively started to let off the gas as the car approached the redline indicated on his tach, that would explain the leaning out of the A:F ratio, and the sudden and here-to-for unexplainable loss of power when the car hits around 6000rpm...

I30tMikeD

iTrader: (8)

Spent the afternoon checking some things.

1. Vacuum. It's not that. I get 19 hg's and the vacuum responds correctly when the throttle is bliped to 2500 rpms. It would not be a vacuum problem anyhow since even a small leak will cause major idle and driveability problems.

2. Coil packs and spark plugs. Plugs look a little too white but nothing terrible. I know I am a bit lean so that was expected. Coil packs pass the mulitimeter ohm test.

3. Knock sensor. I get a reading of 700 ohm's. Wierd thing is that I can't get a reading at all when using the ground prog (right prog). I get my 700 reading when using my battery for a ground. Don't know if that should be a concern. I do have two other working knock sensors but don't want to replace mine until I meet up with brian and see if this one is messing with my timing.

3. Cat Put the car on the lift at the shop I used to work at. I did not actually remove the cat because I was concerned about the bolts to the B-pipe breaking. I was not in the position to deal with that at that time. Pounded on the cat and B-pipe and did not hear any thing loose but that does not mean my cat isn't broken apart and clogging things up. One thing about it being the cat is that I remeber a few customers in the past with clogged/broken cats and thier car had no power what so ever, which is not my case.

4.VI. Not my main problem but still looked into it. Removed the top cover of the VI and all butterfly valves are there..no missing screws. Got a new vacuum canister but still don't get a release of vacuum when removing the hose from the canister to the solenoid...that has me confused. Removed all the VI vacuum hoses and checked for clogs and such and they are all in good shape. I want to rig up some sort of LED that will let me know when the VI opens. Not just when the summit switch activates but when the actual VI opens. Maybe some sort of connection on the actuator that when it's broken an LED light in the cabin goes off/on. That way I will know for sure that it's working.

I really think it's a timing issue or exhaust problem.

deezo

iTrader: (3)

Mike: As far as the VI thing goes, I'm going to try rigging something mechanical also so I can really know if this thing is opening. I just used the check valve and the butterfly flutters when it opens so I connected the canister back up. I did the canister test and it holds vacuum until I unplug it.

Maybe I'll put my son under the hood while drving around and have him tell me if it's working.

96sleeper

iTrader: (4)

This may be backwards from everyone, but ever since i got the summit switch, I have never had one problem with my MEVI not opening. I have a led wired up to the switch so I can tell that it stays working. What I did on the map/baro switch was provide power to it at all times, and let the rpm switch provide ground. I did away with the relay. I put a quick disconnect on the ground wire from the rpm switch, and I can check the vacuum canister to make sure it is working. I can let the car sit in my driveway for 8 hours and then go ground out the solenoid and the MEVI will open flawlessly with the car not running.

I30tMikeD

iTrader: (8)

Ok...tell me if this makes any sense.

I know for sure now that my VI not opening is a canister problem. I now have collected 3 napa canisters over the last year. On all three of them I can blow air in and out of of one nipple. The nipple that recives the vacuum from the FPR should not be able to be blown through, and I can on all of them.

So, when my rpm switch activates the solenoid the solenoid vents to atmosphere correct? Well, if my check valve is not working then all I basically have is my FPR venting to atmoshphere...hence a vacuum leak. Now this would only occur at high rpm's when my rpm switch is activated so I would not have a vacuum leak until then.....That is why my power is normal at low rpm's.

Rpm switch activates....check valve does not work...vacuum leak occurs...power drops. Make sense or am I missing something.

Stephen Max

iTrader: (59)

I doubt that the vacuum leak itself is enough to affect power directly, but it may be indirectly. If your check valve isn't working, then your fpr may be seeing residual vacuum in the canister during the dyno run. If the fpr is seeing vacuum then it doesn't raise fuel pressure from 34 psi to 43 psi as your manifold vacuum drops to zero when you go WOT. That may be why you are so lean (14:1) right after the rpm switch activates the vacuum control solenoid.

Have to think about this for a while, though.

I30tMikeD

iTrader: (8)

I think it all kinda works together and it all happens at my 5.4K VI activation point. Vacuum leak, unmetered air, lean condition, power loss. I may even get some detonatioin because of the lean condition which may pull my timing a bit and contribute to the problem

Dave B

I don't know if anyone has said this, but the condition you're experiencing is a major problem with the JWT ECU tuning. Every JWT ECU dyno plot I've seen shows a 14:1 AF from 2000-7000rpms.

I30tMikeD

iTrader: (8)

Put a check valve in line with my vacuum canister and my VI now works!

I guess when it's been so long since something has worked you forget what it feels like when it does work. It's definately working now. I drove around for 15 minutes and acvtivated the VI about a dozend times and everything feels sooo much better. I didn't know what I was missing.

I don't want to say for sure that both my power loss and VI issues are both taken car of, but I am kinda sure it is. I will continue with checking everything out and meet up with Bejay1 for some diagnostic time tomorrow as well as check my cat.

I30tMikeD

iTrader: (8)

I am at 13.5:1 or less until 6k...but that is when all my power issues occur.

deezo

iTrader: (3)

Where did you place the check valve Mike? I know you said in line but on which path?

I30tMikeD

iTrader: (8)

it's right before the vacuum canister on the hose from where I tap for vacuum.

Dave B

I guess this is probably why I've never had a vacuum problem, I've always run an inline check valve before my vacuum tank. It's good to hear you got the VI to work. Can you hear the switchover? Mine's freaking loud.

Now it's time to figure out where all your power went. I'm really hoping you can prove to me that headers actually make power.

I30tMikeD

iTrader: (8)

I really think my power loss was related to the bad check valve creating a vacuum leak. You think my theory makes sense? I won't know for sure until I dyno again. I hope to get some good info on my timing when I meet up with Bejay1 tomorrow.

I30tMikeD

iTrader: (8)

Got together with Bejay1 today and eliminated a few more things.

It's not the timing. I get 28 degrees at redline WOT

It's not the cat. Temp before the cat is the same after the cat. I do have some temp difference before and after the resonator, but it was not drastic.

The auterra could not read a couple other items I wanted to see like fuel and manifold pressure. The car is running real strong up top now that my VI is working. I feel that my vacuum leak at VI activation threory is correct. I will dyno again to find out.

Dave B

His peak torque is decent, but there are many others making 190-195wtq at peak with the MEVI/JWT ECU 5 speed. I haven't dynoed with my JWT ECU yet, but I made 184wtq prior. I expect to making at least 190wtq. I guess what worries me is that the headers aren't doing what they're suppose to. Even with an MEVI failure, the power should have been much stronger prior to 5400rpms. This is what brings me to the dyno and the numbers it generates. Dynojets observe how fast your car spins the rollers over time while observing RPM. From here torque is calculated and then HP. This isn't to say all dynos spit out the same kinds of numbers. Dynojets in two different states won't produce the same numbers. I believe this was Mike's first dyno so we have no idea what he would have done prior. It is quite possible that his I30 may have generated higher numbers at the shop I run at. The same can be said about your car. Your numbers are relatively low compared to the others, but your 1/4 mile times suggest otherwise. Different dynos, different numbers.

Dave B

Honestly, I don't know how a bad check valve would cause a leak to the atmosphere (ie vacuum leak). The only thing venting to the atmosphere is the MAP sensor. When the MAP sensor is not engaged, the vacuum line to the actuator valve is being vented to the atmosphere. When the MAP sensor engages, the valve closes and vacuum from the tank pulls the actuator valve back and opens the butterfly valves.

Even with a small vacuum leak and the butterfly valves open, I would think power would still be made and sustained at the typical 6100-6200rpm MEVI peak with power slowly falling off by about 4-5% at 7000-7200rpms. With a small vacuum leak, the numbers will probably be slightly lower. I've run at the track with a small vacuum leak and I was about .1 and 2mph slower on average. My leak was right after the MAF. The car ran fine, but it was slower.

I30tMikeD

iTrader: (8)

I see what your saying. So with a bad check valve there is not a direct line from the FPR hose to atmosphere at any time? The acuator is a completely colsed system? So if I was able to keep the VI activated for, let' say, 20 minutes then the vacuum would never be depleted because it is not escaping, it's just pulling the acuator arm open But not actually leaving the system.

What StephenMax said about the FPR and how the amount of vacuum controls the fuel pressure made sense to me. I don't fully understand how it works but If not having the check valve caused problems with the FPR and for some reason fuel pressure droped then I would have the problems I am having right? It just seems really odd that this power loss just "happens" to take place at my VI activation point. Everything seems fairly normal before that...then all of the sudden bam!

If my crap "vacuum leak theory" is not correct then I have no idea what is wrong.

Me and Bejay1 saw nothing odd happening today during our runs. One thing we just did not have time to do was data log some WOT runs with my check valve not working. We really should have.

spirilis

iTrader: (2)

If the vacuum check valve is malfunctioning, I would imagine you'd experience a "vacuum leak" in the TANK because WOT causes intake manifold pressures to rise to near-atmospheric pressures...
The purpose of your vacuum tank with its check valve is to store vacuum (or rather, store the lack of air) so that when the VI requires engagement, the VI side of the system has sufficient vacuum to pull its actuator. If it's allowing air to vent back into the tank at WOT (due to check-valve allowing 2-way flow) then it will have insufficient vacuum to pull the actuator on the VI.
For a while I thought I had that same problem with the stock VIAS on the 2000 (VQ30DE-K)... turns out using a stopwatch test my VIAS was working fine. I actually haven't proven that too well (I only did 2 runs in 2nd gear, one with and one without the VIAS control solenoid connector hooked up), but I do hear the "roar" at 5200 RPM and above with my new PR CAI.

I30tMikeD

iTrader: (8)

Exactly, that is the reason I said the my VI was not working.


What I thought the probelm might be is that without a working check valve the pressure inside the FPR hose is not what it is supposed to be at WOT and fuel pressure is effected. But I don't really understand how that system works with the manifold reaching atmospheric pressure and the fuel pressure changing...

spirilis

iTrader: (2)

The manifold reaches atmospheric pressure because the throttle is wide open, and quite simply, the engine can't suck air in fast enough to keep up and maintain a low pressure inside the manifold (well, up to a certain point--I think that becomes less of a problem as RPMs increase) So instead of the engine's intake strokes dominating the volume inside the manifold with its vacuum, the throttle body dominates by allowing air to rush in to fill up the vacuum (since air's coming in through the throttle body faster than it's going into the cylinders, whereas with the throttle closed it's usually vice-versa)
Normally the manifold sits at a steady low pressure because the engine's intake strokes occur so fast,but due to the throttle restricting airflow, not enough air can come in to meet the hungry demands of the cylinders. That's the throttle plate doing its job--restricting incoming air to restrict power production. Results in a consistent low pressure inside the manifold. At WOT, the "throttle" effect of the throttle plate is not present, hence why you produce the most power with the pedal to the metal

Now, as for your FPR argument... that's a good point, but I'm not sure if it'd make a large enough difference to produce THAT big of a power dropoff. Theoretically, if the hoses going from the manifold to the FPR are large enough, there shouldn't be any significant difference in pressure at the FPR. However, the vacuum tank does change the demands on that vacuum hose, since the vacuum tank is undoubtedly much larger... so I dunno. Hard to tell I guess, at least without some equipment that can tap the vacuum source without introducing a lot of extra volume to the system itself.

I don't know a lot about the fuel systems either, but I believe the FPR normally (without input from the vacuum hose) attempts to maintain fuel pressure at a certain constant... but the vacuum hose inlet allows the FPR to modify that "constant" pressure it maintains so that at high vacuum (lower demands, due to the throttle being closed tighter) it runs at a lower fuel pressure for economy, and at higher pressures (lower vacuum, e.g. WOT) the FPR maintains a higher fuel pressure to meet the extra fuel demands on the engine. But I'm pretty sure there's a decent margin of error/inconsistency allowed in that setup.
(I believe boost-sensitive FPRs take this concept further by allowing the FPR to respond to greater-than-atmospheric pressures, bringing fuel pressure up even higher...)

I30tMikeD

iTrader: (8)

Thanks for the info, it helped me understand the relationship of the manifold pressure.

So I think to prove my theroy of my power loss I need to rig up a fuel pressure gauge that I can read inside the car. Remove my inline check vavle that I installed to make my VI work and see if fuel pressure drops at VI activation. Then put the check valve back and see if fuel pressure remains constant past VI activation.

Or I could just go dyno again and see what happnes.

What is a good way to read my fuel pressure?.....I suppose T off a fuel line and run it into the cabin of the car. Should I be worried about having a fuel line connected to a pressure gauge inside my car at WOT?

spirilis

iTrader: (2)

Not sure, never played with the fuel system much... doesn't sound like something I'd want to do

I understand there's something called a "schrader valve" that's typically used to tap into a fuel system... maybe you could install an in-line piece in the fuel hose with a schrader valve on it, and hook up a fuel pressure gauge, just not sure how you'd view it from the interior... I'd be a little hesitant to close the hood on one of those and have a gauge in the interior

PS- I'd try the dyno with the check valve installed. Do you notice a difference with it installed?

I30tMikeD

iTrader: (8)

I am not going to make any claims on how my car feels because I actually thought it felt good before the dyno. I officially have the worst butt dyno in history.






















.....but, yes, the car feels much better with my VI working.


Do you guys think it's important to go back to the same dyno? I know of a place I can save about $40 and I did not much care for the people at the first place I went to.

If I do dyno again, and some miracle happens that my curve looks normal then I will dyno my second run with the check valve removed and see what happens.