Possible Valve Hitting Piston Sound/issue?

[mill-180]

hi guys, having a bit of an issue atm with my R34 GTT RB25 NEO. its been rebuilt and currently getting tuned,

the tuner found out the VCT wasn't connected so it is now connected but after 5000rpm it sounds like a valve is hitting the piston.

he heard this and turned the car off right away and D/C the VCT solonoid.

He took apart the timing belt cover and timing perfect and the TB has not jumped any tooths.

All clearances were checked and triple checked before bolting the block to the head.

It only happens when the is VCT activated, anything below 5000RPM, there is no noise and drives perfectly, idles perfect and no stuttering or hesitation.

Can anyone help me with this problem and to sort it out?

My car has been off the road for quite some time and this was suppose to be the final stage but now looks like it could be delayed longer by this unknown noise thats really got me worried

If anything, he will end up tuning the car without VCT activated.

Appreciate any feedback or input regarding this situation.

Edited February 16, 2011 by mill-180

[zebra]

Its probably knocking, if it were a valve hitting a jam pot there would be next to nothing left.

So wait, tuner tuned car with No NVCS then hooked it up and ran it up on the dyno? and it made noises....yup sounds like it was pinging its head off to me.

Also I'd find a new tuner if he didnt re-tune after hooking the vct up.

[DVS JEZ]

Even a few taps of piston to valve will bend the valves. If it hasnt been damaged yet then it might not be contacting.

Try turning the vtc on at a lower rpm and see if the noise is still there.

It might be pinging

[mill-180]

and for ppl who said it drives crap with VCT turn off, i ran it in for 1000KM with the VCT turned off (i didnt even know it wasnt connected) and the car drove perfectly, no issues or felt "sluggish" at all.

Would a knocking noise be that audible outside the car?

Surely my tuner would know what knocking/pinging sounds like.

[DVS JEZ]

It might have driven perfectly without it. But with it it should be even better.

He should know what pinging sounds like. Its hard for us to diagnose sounds. We are just giving possible causes

[R31Nismoid]

and for ppl who said it drives crap with VCT turn off, i ran it in for 1000KM with the VCT turned off (i didnt even know it wasnt connected) and the car drove perfectly, no issues or felt "sluggish" at all.

Would a knocking noise be that audible outside the car?

Surely my tuner would know what knocking/pinging sounds like.

well you'll be in for a nice surprise when VCT is turned on and you see the difference.

if you don't, then same as the other thread about it recently - the tuner is doing it wrong.

[89CAL]

+1 for it being tune related.

At 5000rpm a valve hitting the piston is not going to end well. Think about human reaction time, it would have hit the piston at least 10 times at those engine speeds before he backed off. If the car drives fine now and es checked everything I don't think this is your problem

[rob82]

If the VCT is being turned off at 5000rpm then your piston to valve clearance gets bigger as the cam is retarding. Try giving it a free rev with it on as - in battery voltage across the two solenoid pins and see if it still makes the noise not under load. Is there any chance that it is PWM the solenoid after 5000rpm - they can be quiet noisy.

[mill-180]

hi guys,

thanks for all the replies.

i was reading through this thread,

http://www.skylinesaustralia.com/forums/topic/353835-rb25-hi-flow-turbo-and-vct-help/

and it indicated that the VCT solenoid can be noisy and make clicking noises? it never did this before, is there any reason why it should be noisy now?

I am going to visit the tuner tomorrow and try and hear the sound myself first hand.

He is an experienced tuner so i trust his judgments, hopefully he is right.

I'd hate to find out that it was infact a noisy solenoid and he charged me unnecessary labour to check if the TB was correct.

[R31Nismoid]

I'd hate to find out that it was infact a noisy solenoid and he charged me unnecessary labour to check if the TB was correct.

LOL

Are you serious?

He is doing a process of elimination - fact is, that costs money and time.

If you want a proper job, dont be a tightass.

Better to rule something out initially than not at all especially with that type of noise.

You'd cry like a baby if it had smashed all the valves and he said it was just a VCT solenoid now wouldn't you?

[dori34]

Yeah I see what you mean nismoid, but the TB was triple checked before installing cover back on and I was 100% sure it wouldn't of been off. I guess he just wanted to be sure.

Now regarding the noisy solenoid, does anyone have a YouTube link to what it would sound like? Is it common that these would be louder then usual when it was perfectly quiet before?

Zebra; he was tuning for cruise then moved onto WOT and he found out the VCT was d/c so he got it connected, then started to tune again with the VCT that's when the noise occured.

Te solenoid works from 1500-4500rpm, then after it would turn off, if this the case, why wud it get louder after 5000? if it was infect the valve hitting the piston, then the damage wudve already been done and the motor won't even run anymore.

[mill-180]

UPDATE:

ok its definitely not a clicking noise from a vct solenoid, sounds like a grinding noise.

the tuner set the vct to kick in earlier @ 2000rpm and thats when the sound occured.

Any ideas people?

[tridentt150v]

Hu uh a guessing game [claps hands]

a valve guide sliding up and down in the head

sorry for you though, its going to cost $$$ whatever it is..........and it will frustrate the hell out of you until you find it.

BTW I really don't know, without sound and being there its a guessing game.

[Rolls]

and for ppl who said it drives crap with VCT turn off, i ran it in for 1000KM with the VCT turned off (i didnt even know it wasnt connected) and the car drove perfectly, no issues or felt "sluggish" at all.

Would a knocking noise be that audible outside the car?

Surely my tuner would know what knocking/pinging sounds like.

VCT makes a huge difference, its like comparing an rb20 to an rb25

[BoostdR]

I had a similar sound from a motor I built. It was actually the timing belt vibrating and touching the lower timing cover on the side... might be worth a look.

Edited February 18, 2011 by BoostdR

[Don Dada]

VCT makes a huge difference, its like comparing an rb20 to an rb25

I used to have mine triggered by a msd digital window sw and tried numerous on/off switchin pts and the difference was verrrrry minimal with the seat of the pants meter....waste of time in my book ......this was on the stock ecu tho, it only decresed spool time by a couple 100rpm

[Don Dada]

UPDATE:

ok its definitely not a clicking noise from a vct solenoid, sounds like a grinding noise.

the tuner set the vct to kick in earlier @ 2000rpm and thats when the sound occured.

Any ideas people?

If its only when the soleniod is activated then is got to be somthing with the vct mechanism???

[KiwiRS4T]

When you say rebuilt did you get new pistons? A few people have had problems with the pistons supplied for neo engines and ended up with very high compression ratios suggesting that the pistons were not really suitable.

[r31 25t]

Just a thought, but when VCT is activated is there a dip in oil pressure and supply to the head?

Maybe the cylinder head or VCT is not assembled quite right.

[Rolls]

I used to have mine triggered by a msd digital window sw and tried numerous on/off switchin pts and the difference was verrrrry minimal with the seat of the pants meter....waste of time in my book ......this was on the stock ecu tho, it only decresed spool time by a couple 100rpm

put it on a dyno, the difference is massive.