GTM stage 1 S/C - Throttle not opening fully? Or boost leak? Please help!
 

So more than 2 years after installing a GTM stage 1 S/C, I still am plagued by gremlins.

Basically, cold start performance is excellent. I get on-boost instantly and it pulls like a maniac. After it is fully warmed up, I get consistently poor (slower than stock) performance, with intermittent full-power.

I have spent days and days chasing boost leaks that simply don't appear to be there. Everything is double-hose-clamped and holds 15psi on a pressure test with no leaks to be found...

I've attached some screenshots of uprev logs showing two runs in second gear, performed about 15 seconds apart. In run 1 (good run), which is ~2800 to 4000 RPM, I instantly get boost, which rapidly builds to ~5psi by 4000rpm. Power delivery is excellent, timing advance sits at about 15 degrees during WOT and the throttle & VVEL exactly match my accelerator input.

The second run, performed literally 10 seconds later, with WOT from ~2800 to 4000rpm, exactly as in the good run. The car sits at 0psi, then builds to maybe 1psi by 4000rpm. Performance is horrific. Timing sits at ~22 degrees, and the throttle and VVEL seem to slowly work their way open rather than matching the accelerator pedal input.

I have played with the throttle maps for hours, and I simply don't understand how WOT at the same RPM, in the same gear, performed 10 seconds later, can have a completely different response! I assume if this was an (impossible to find) boost leak I would get the VVEL & Throttle performing the same way in both runs?

It's like there is some other feature/sensor/something that is wildly changing the car's throttle response, even on identical runs.

I'm so sick of battling this gremlin, and it is really sapping any fun out of the car :( Any advice would be greatly, GREATLY appreciated!!!!!

Thanks :)

That doesn't sound like much fun... I'm no expert but could it be something with the intake manifold? Have you reached out to GTM?

This isn't a piping boost leak or it wouldn't be sporadic. First thing I would do is clean and inspect your bpv. Sounds like it might be getting stuck and allowing boost through it.

BPV is a good suggestion. What about throttle position sensor?

Would this also cause the PCM to play games with the throttle, etc due to AF ratio?

I've removed, torn-down, cleaned, lubricated & re-assembled the BPV (35mm turbosmart re-circulating). It seems to operate smoothly and normally in response to pressure/vacuum changes. About 6 months ago out of desperation I even replaced the cut-down spring with a full-sized supercharger spring from Turbosmart (which is far too strong for the GTM setup, locking the valve closed most of the time and causing a lot of flutter, but certainly ruling out the BPV recirculating).

I did speak to Sam but then he stopped responding, so I'm battling this one on my own now.

I was also thinking maybe a boost leak where the plastic manifold meets the head, but that doesn't explain why the throttle and timing are so different (I would have thought that, boost leak or no boost leak, the throttle & timing should behave the same). I've removed and reseated the intake manifold at least 4 times over the past couple of years, including replacing the gasket, and it all seems completely fine.

I'm most confused about the throttle and timing differences between the two runs - I just can't understand how or why the ECU is doing what it is doing, especially as the MAF sensor readings are quite similar between the two runs.. It's like there is some unknown third variable the ECU is using to decide how to perform :(

What about the super charger itself? Are you confident the internals are working properly? Hopefully you don't have any valve train issues either. How about reloading the tune? Is there such a thing for the 370z? I did that with my Supercharged Mustang a few times.

Just throwing things out here... Belt slip? :-) I'm guessing it's ok?

PCV valves?

Belt coverage with the GTM kit is very high, the belt is in good condition and tension is fine so I think that can be ruled out. PCV is fine as well, unblocked and no leaks.

Supercharger I'm fairly sure is fine internally, as it has no trouble producing power when the throttle wants to open properly :)

Make sure supercharger traction fluid isn't low ...and when is the last time it was changed...if I remeber correctly our super chargers work with a type of traction drive to engage internally ...

I assume it behaves the same way stationary or moving? Did you say you checked/replaced the throttle position sensor?

On my Mustang I had to turn traction control off completely. It literally stalled the car any time I pushed the throttle just a little aggressively.

Same problem I had it's a bad tune from GTM (sam)

Turn the highlight function to "OFF"

Make this change and all will be well!

http://www.the370z.com/forced-induct...ing-boost.html

http://www.the370z.com/members/pokey...74308-tune.jpg

Damn! I just read that thread. What a nightmare.

ditch uprev and go to ecutek, there are several parameters that are not accessible in uprev that exist in ecutek.

Ahhhh this looks very promising!! Problem is I don't have P0101 at all :( It's missing from my Uprev rom... Did you have to make any changes to have these options? I don't have the 2 DTC settings for the MAP sensors either :(

It will not set the code, trust me, if it did I would not have spent 8 month and 3K USD to find it.

If you do not have that code, look at all the other codes for one with the same name.

Do you have P0106?

You need someone with the same year and Aus make that has a good tune, copy his setting. Good luck

Last check with uprev see if you have the current ROM reader with full access to all the code.

I've just grabbed all the Uprev ECU dumps for EU/AUS models (I'm 1EL6B, but I downloaded all the others with the rom editor) - They are all missing 101, 106, in fact all the MAF & MAP performance/range/correlation settings (and a good 10-20 other DTC's) are missing! Nothing similar in name either.

The JDM and US ECU dumps from Uprev have these codes, but the EU/AU dumps don't, making me think the issue is at Uprev's end in not adding these DTC's to the ROM dumps. I've just emailed them asking why they are missing.

My car definitely has a MAP sensor, so I'm certain the codes are built into the ECU... We will see what Uprev comes back with!

OK, so I disconnected the MAP sensor and the ECU throws P010A. I have no P010B, but I do have P010A,C,D.

With the MAP sensor disconnected, I get full boost followed by crippled performance shortly after. I disabled P010A,C & D, and cleared codes, and with the MAP sensor still disconnected I get the same massive throttle lag...

So I'm fairly sure it is MAP sensor related, but it seems like my ECU probably doesn't have the MAP/MAF performance DTC's at all.

So my question is, how the F*** do I fix this!? I can't disable the DTC because my ECU doesn't have it, the DTC I do have doesn't stop the "safe mode" and leaving the MAP sensor unplugged doesn't help... So depressing!

I guess a better start would be if anyone has definitive information on how the MAP sensor's output is used by the ECU? Is it purely a safety device? I feel like there has to be a magic bullet for this problem, I just don't know what it is...

Who tuned the car? your ECU has to have it somewhere, if it didn't the sensor wouldn't be on the car :/.

I thought anyone with FI has a custom tune and only use a canned tune to drive it to the tuner, or use it as a baseline for the custom tune.

Sorry, I should clarify - It has been significantly modified, but the starting point was the GTM base tune. AFR targets are fine and timing is conservative.

Any updates? Curious to know the status

No, the can tine is 80-85% and you can drive on it, very safe.

Really consider this. Ecutek=full control. Timing, throttle (real throttle control), you could even have hybrid MAF/MAP tuning.

Update:

Still F***ed.

I'm certain it's the MAF/MAP sensor...

Sam at GTM was useless, as was Uprev. Basically I'm physically limited by not being able to disable this code.

The original service manual has the P0101 and P010B codes in it, yet Uprev doesn't have them in my rom.

EDIT: after checking out the MAP sensor, it can only read from about -30 to about 1psi. 1psi equates to 5V output (on a 5V input). I'm going to remove the MAP sensor, grab a couple of resistors and feed a constant 3v into the MAP sensor input signal to see if this helps.

The service manual doesn't suggest that P0101 or P010B could even relate to the MAP sensor though, so there is a chance I'm screwed... May be talking to ECUTek soon... Uprev is a joke.

So, just did the following:
- cleaned TB's
- cleaned MAF's
- reset TBs, ECU and idle air volume

No change, still crippling ECU mode

I then replaced the MAP sensor with a voltage divider putting out 3.2v. this didn't throw a MAP error, but identical symptoms occured (possibly triggered slightly later, I seemed to have a good 5 minutes of driving before the ECU reverted to ****-mode)

Anyone ever tried an ECU swap? I'm tempted to buy an ECU that UpRev supports disabling P0101/B and dropping it in...

SpecialtyZ sells the MAP sensor from the GTR that is a drop in replacement for the 370Z MAP and it is designed to read boost. That is what I am using with a Ecutek tune from Seb. Contact Seb and see if he can offer you some advice.

EcuTek Tuning - 370Z/G37

Are you still using the Turbosmart BOV? Mine fluttered badly, so I changed to lighter springs AND firmer springs , still fluttered and seamed to blow off early when using a lighter spring. I switched to a Synapse valve, still flutters but seams to work fine, though it performs better ( less flutter) when I keep it lubed.

I also get P101 code a lot when I start up cold, so I bought a cheap laptop and keep it and my uprev cable that I got with my SC kit in the car.
I downloaded my uprev program onto the computer and reset the code when it pops up. Which seems to happen when the car sits for more than a couple days.