rol

iTrader: (1)

I just had my car on the dyno to map it after going single. I've driven it a little bit on the road, pig rich and with a very conservative tune.

When we put it on the dyno it was clear that there was a lot to be done, so we started of just trying to even out the fuel and adding just a little bit of ignition. Did 6 runs where we didn't really look at the hp, just tried to even out the tourque band. But when comparing the six runs we saw we had lost a fair bit of top end power and torque. Tried to figure out what was happening and did two more runs, the car then started making a strange noise, not really loud but it sounded a bit like something vibrating/grinding. The tuner also felt it in the clutch pedal. We then stopped the car to look for loose parts or what have you, but didn't find anything obviously wrong. Then we had a lot of trouble getting the car to start again, but when it finaly started I could see that the front pully was slightly vibrating.

So now I'm wondering whats happened, Could I have spun a bearing, or could the front pully loosend somehow? The engine was rebuilt max 2000 miles ago, and I havn't tuched the front pully or the front eccentric shaft bolt.

Hope someone can give me some hints to what may be wrong.

The mods are as follows: Street ported rebuildt engine with new housings, GT35r singel turbo with all the suporting mods( fuel, ic and exhaust), greedy pully set, HKS twin power.

rd_turbo

iTrader: (4)

The starting issue and the vibration issue may be unrelated. Was the starting problem accompanied by a significant difference in starting speed or were there any unusual noises during cranking?

If the vibration is caused by mechanical failure, and I'm sure you know this, you'll need to start digging. I'd check the front pulley bolt as you said. If it's loose, assume the thrust bearing has dropped, in which case the front cover will need to come off. If the bolt is tight, try turning the engine over with a wrench a few times and see if you feel anything unusual. Also, in very rare instances, if the flywheel nut was not torqued properly, the key will get loaded cyclically and shear, which could allow the flywheel to rotate relative to the e-shaft, which would result in imbalance. You may elect to remove the stationary gears with the engine in the car. Broken teeth won't result in vibration for long before the debris locks the engine up. That will give you an indication on the condition of the stationary gear bearings, although the wear will not be enough to result in significant play. It's usually the front one that fails first.

You may also want to check the spark plugs, in case the vibration is caused by a failed plug or a misfiring. That will give you a chance to check the compression, in case one of the seals decided to pack it in, in which case the vibration would be power pulse related.

Barry Bordes

What did your oil pressure look like during this time?

Drain your oil and check it's condition. Cut the oil filter apart to check for metal.

Check axial end-play on the e-shaft.

Barry

rol

iTrader: (1)

Thx for the answers. The starting speed was the same and there where no unusual noises during crancking. Oil pressure was constant before and after, but i only have the stock oil pressure gauge which isn't very accurate.

I'll start digging in a weeks time, I'll keep you posted and probably come back with more questions