RB26 boost problem

[Amaru]

Had a quick search but couldnt find anything, having an odd problem with the car (R32 GTR).

Just had some Tomei Poncams installed and when the car hits 0.75 bar boost it sounds like its misfiring (its not misfire though) and the turbos (hks gt2530's) start to surge (e.g going "woosh woosh woosh woosh woosh woosh").

Anyone know what could possibly cause this problem? The car drives fine around off boost, but as soon as it hits 0.75 bar it runs into the above problem. The car ran 1.5 bar no problems before the cams were installed.

From what I was told the in cam is +4 and ex cam is -2, all the shims were also replaced and valve springs.

If anyone has any ideas what could be causing it, would be appreciated.

[japtaxi]

welcome to the world of "turbo shuffle"

this is where u replace standard exhaust manifolds and put in manifolds with balance pipe in between.

[Jay95R33]

I thought the Proncams where dialed right straight out of the box (no need to run adj cam gears etc).

I'm probably wrong though

J

[The Alchemist]

mine does it as well although my cams are set on "0" on my degree wheels, which means very little other than a starting point for which to gauge changes by. I stop it by simply changing down a gear and moving out of the surge line.

Have you have it dynoed since the cam change? my torque starts to drop off after 4800rpm since I've installed the cams so I guess I will need to retard them to move the torque curve to the right a bit to get back the top end rush. I change gear now at 5000rpm cause the torque drops off so much after that.

Mike

[Amaru]

mine does it as well although my cams are set on "0" on my degree wheels, which means very little other than a starting point for which to gauge changes by.  I stop it by simply changing down a gear and moving out of the surge line.

Have you have it dynoed since the cam change? my torque starts to drop off after 4800rpm since I've installed the cams so I guess I will need to retard them to move the torque curve to the right a bit to get back the top end rush.  I change gear now at 5000rpm cause the torque drops off so much after that.

Mike

Havnt had it on a dyno but done extensive road tuning with it. Whats wierd is once the car warms up (oil temp over 70 and water temp at 80 - 85) it does it a few times, and then it clears up and doesnt happen again until you cold start the car and wait for it to warm up where it does it a few times again, and then clears up and doesnt happen. Very wierd problem.

And the cams are far from dialled in from factory, all in all after this experiance, ive come to the conclusion the camshafts are -far- from a "bolt in" item...

[The Alchemist]

try setting it back to "0" / "0"to start with then retard the inlet ( this will move the torque upwards in the mid to top range) and adv the exhuast ( this will widen the lobe centres given a broader torque delivery0 THATS THE THEORY ANYWAYS

I'm off to the dyno tomorrow for some extensive testing on my own GTR so I'll let you know my results if you like.

Mike

[Amaru]

Thatd be great if you could man, mines going in soon for a whole day of dynoing to get it right and ill let you know what I come back with as well

[DAN00H]

Nik

Can't be the cams that have made the difference, as my car is doing it as well! and it has not had any changes since the dyno day. 1st time I experienced it was using OCTANE booster - it foulded the iridums, which i replaced with coppers. This solved it for a few hundred km's, but it has since returned.

I have read other posts that point to the coilpacks.... I'll be checking these and changing my fuel filter.