And, I know you said your plugs are not old, but I'd be thinking some type of miss or misfire. Are you sure the plugs are the right ones?

LP

 

They are a 1 stage cooler and pregaped from EVoms. I didn't see them or install them though. Originally I thought it was misfiring too but, the old plugs didn't look that bad.

 

My guess is that the plugs are the problem. A number of knowledgeable folks have told me there is no need to change from the OE plugs until you get quite a bit higher in power.

I'm not a betting person, but I'd bet something on this one. The problem you now have is that a plug change is a PIA.

LP

 

Okay, Tonight I checked the Pin arm on both turbos and they are moving freely back and forth. I also checked the diverter valves and they are moving freely. One of the diverters ports on the driver side was not lined up correctly with the turbo housing though. It was pointing half off of the inlet of the Turbo port.


I also check the turbo hoses on top of the engine along with the tubing before the intercooler. Everything seems intach.


I did notice that the rubber tubing was very easy to squeeze. Has anyone had an issue with the tubing after a flash? I'm thinking contraction or expansion. I would think that would also create problems.

 

May be my next choice if the dealer or Indy shop doesn't have any suggestions.

 

Okay, quick update a year later.


I have been in contact with Evoms on this issue and their request was to take a video of the noise, my iphone did better then my Go pro so here it is. (I needed too refresh the video to see boost.)


https://www.youtube.com/watch?v=2W5O...ature=youtu.be

This noise happens after Boost hits 15PSI.? Recently I installed, New spark plugs gapped at 0.25 stock temp rating, New coils, New 997.2 GT2RS intercoolers, swapped out the Evoms BRV's to Forged (yellow springs) BRV's, I did pressure check the intercooling system to 25PSI after the turbo's.


I have the Durametic Pro version so I can log and create excel spreadsheets, what should I be logging to put this issue to rest?

 

Have you tried putting back the oem brv?

 

I'd have a Porsche Centre wipe the tune and back to OEM tune.

 

It could be a few things and most have been mentioned.

It could be the flash - you may want to re-flash with the same maps or as mentioned get the dealer/tuner to put a stock map back on and see if it goes away. Have the tuner check his map for those specific rpm, engine loads.

Check the voltage as you do those runs and see if the voltage drops, if it does, then there could be a disruption to the fuel pump (I actually had that issue) and it sounded a bit like your issue.

Have the technician check for secondary knocks - I don't believe those throw a check engine light, but when that happens the car pulls timing and turbos have sensitivity towards pulling timing (i.e., you lose much more power than NA engines - if memory serves right, each degree of timing is about 50 hp)

Did you change your coils when you changed the plugs? If not, that's a good idea to do.

Good luck as finding the root cause for these things is annoying at best.

 

no solution for you here.
But I have a similar problem, Less of the air noise but definitely similar.

I'd guess the flash. I believe someone previously said that it was probably an overboost issue reacting and closing the throttle plate, looking back over my logs this appears evident, although not by much (5% deviation maybe)

I always just figured it was spark blowout and that I needed to swap my plugs and coils, but I haven't got to do that yet.

It's not a case of knock as I logged everything I could regarding the timing.

Hope you find the issue all the same, it may help me nail my issue down for next season.

 

512bb - Thanks for the information. I just replaced plugs and coils. Evoms would like me to now do some logging. I will have the logs soon.


Mitchy - when this occurs, there is no jerkiness to the car due to miss firing. Logging will really help clear this part up though

 

Funny. Read this. Another Evoms car with a pulsing issue

http://www.parr-uk.co.uk/media/pdf/p...turbo-test.pdf

 

Interesting, same thing I feel and hear? I'm not at 700HP though so, I cant say I'm pushing the limits of the ECU. Do happen to know when this was published?

 

2008. You've been amazingly patient I have to say.

 

The car in that article was using a very early EVT700 kit with very early 997TT software. Totally different hardware from this car, and the issue causing the power oscillation was resolved years and years ago. What was going on then was much different from that this is--a slow oscillation, whereas this noise is occurring at a higher frequency.