Clean the maf? I feel that is a waste, for 200.00 bucks buy a new one. I have seen more then one maf go bad that did not show signs. You need to watch more then just the maf on your logs to see it..

 

As mentioned before mine only did it on the track after several sessions, then fine the next morning (no codes were present). I have replaced the factory boost solenoid and next time I'm at the track if it does still do it I will pull off, unplug the MAF and then see if the boost returns. Shouldn't run it hard that way on the track, but should be able to just unplug it, and if boost was being cut by a false signal from the MAF then it should return. At that point MAF will run on different default fuel tuning table, but full boost should still be available. I remember a thread about running MAF-less and I believe Markski unplugged on the dyno and still made the same power or similar. Someone chime in if I am wrong, not 100% positive on this.

 

best of luck with that, let me make my last post a bit clearer. I have seen bad maf's that were not throwing codes or easy to find with data logging. You are having a problem that is hard to find and you already changed the N75 valve which is a pain. Adjust wastegates, same thing. The price of the valve plus time to install, Same if not more the putting in a new maf. I can be wrong but cel does not need to be on or throw a code in order for the maf to be bad.

 

Point taken, I will be bringing a new MAF along when I go to the track next month, but changing the boost soleniod costs less than $40 and an hour of my time which is one reason I did it first. Since I want to know the real cause, and I cannot duplicate the problem with street driving, I have to wait for the next track day to see if the solenoid fixed it. If not, I'll throw in the new MAF like you are suggesting. PITA to track down since it only occurs on extended track sessions. Also it is not just fuel as I am running race gas on the track and only 1.2 bar, and once it starts doing the boost drop to .8 it stays there even if I let the car cool down for an hour or two. Then next morning all normal, just weird.

 

Peter did something to it when you were not looking.

 

When you let it cool down did you do a soft reset, disconnect the battery for a few minutes then reconnect? These cars kind of stay on unless you lock it with alarm. Even then they still draw power.

 

I did pull the battery cables to during cool down. Left them off for 20 min or so, then also with both disconnected, touched the positive and negative battery cables together which further discharges any soft memory. Still had same problem, but next day it was fine.

 

That's something that Sean would do to YOUR car, (or your rear end...)

I'll be in town for the Mile next week hope to see everyone

 

I am not sure if the maf is your problem then. Do you use the water/meth on the car when it happens? I know it sounds like I am against using it but it can be wetting the maf when the diverter valves dump boost in too the intake. I drys over night and is good to go the next day. The track is the hardest proving grounds and what works on the dyno not always works on the road course..

 

I do use the meth on the track, not for fueling but for cooling. Running 70/30 water meth. There is one more possibility, and that is the failsafe of the meth system. There are two, tank level and flow sensors, if either activates, the boost cuts to wastegate default, which coincidentally is .8-.9. However when the problem is occurring on the track the meth is still spraying fine. Tank is full and the bar graph on the meth gauge is full showing full spray, so flow should be fine and the tank is almost full. Tony at EPL said there is an instance where the meth could be spraying and the fail safe could still be triggered. The aquamist meth gauge has flow limit screws where you set a low limit for flow and a high limit. He said if it goes outside that limit it could still trigger a boost cut and the meth would still spray. To test for this you can get rid of the limit by turning the left screw all the way counter clockwise, and the right screw all the way clockwise. This effectively disables the boost cut do to flow or level. The problem I have is that this only occurs at the track, so I have to wait for it to happen again then try this also. Still not sure how if this is the problem, that it would just start happening in the afternoon at the track , then be fine the next morning.

I'm still going to bring a MAF to the track just in case, it just ruins an afternoon of track time when the boost just drops like that for the rest of the day after being fine all morning. Makes no sense, any of the possible causes seem like they would occur on the street also as cooling it down does not make it go away until the next day.

 

okay, Two things. One is there a chance that under hard braking or turning that the meth injection can suck some air, does that let the fail activate? does that need to reset or does it reset itself?

Second item is that the DV's may be sending water/meth into the maf and wetting it. Talk to your tuner and see if you can run straight meth. The straight meth would most likely be fully evaporated and less likely to effect the maf (if that is what is happening).

 

Nope can't suck air, tank is vertical and full, pickup at bottom, and does not make sense as to why only in the afternoon sessions.
Swapping the MAF next time it does it will answer also. As would unplugging the MAF, sure would like it to do it more often so I can find it!

 

Could it be some failsafe (not meth related) that is pulling the boost down? DME related fail-safe? I'm not 100% familiar with the boost strategy on the ECU but could the high intake temps in the afternoon be reducing boost?

 

The meth is installed on the pressure side...just before the TB. Its not sprayed across the maf.

 

Don't think so because I let it cool down for over an hour before driving home, pulled the battery cables to reset, and on the relaxed drive home it was still doing it. I did not have my laptop with me at the track so could not datalog which would be the ideal thing to do. So will have to bring the laptop next time, and if it does crop up, get off the track and datalog. Will be able to tell what your guessing by checking ECU boost set point (request), and actual boost. Going to change plugs also, guess that is possible, maybe they are heating up enough that they do not cool down until the next day. As Tony just mentioned the MAF is way before the spray as I am still running stock intake piping, but possible the MAF is still acting flakey but not due to water on it.