Today i went for a ride on some good roads (well as good as we can do down here), and while climbing a hill i noticed a valve tapping sound. It was only in lower RPM's, and i only heard it when climbing (i could hear it echoing off the trees). It doesn't do it on a flat road (or atleast that i can hear), and i have never heard this sound before. I posted this in the FI forum since it "may" be FI related on my car. Anyone have any ideas what this may have been? Paranoia?

 

My other Nissan make the valve tap sound when both exhaust manifolds' bolts broke! Check that no bolts broke and the plate is not warped. You have to be careful not to over torqued them when installing turbo headers. Good luck!

 

^^He has a TN kit, he wouldnt of even taken off the stock manifolds...

 

My other Nissan's (not Z) stock manifold warped and was not heat stressed by FI. If that's the issue, it's a chance to upgrade headers. Apply thread loosener overnight to ONLY the bolt studs, to avoid breaking them and enduring my expensive repair$.

 

First Ive ever heard of that happening...

 

could it be your oil level. You said only when you were going uphill so maybe the oil was sloshing away from the pickup?

 

Bingo... I would check that for sure. Whats your oil level? What kind of oil? Do you have a pan spacer or replacement pan?

 

I have an oil pan spacer, and even after 6 fresh quarts I noticed under 2500rpm's easy throttle input-flat ground gets me what sounds like a tap tap tap....wasnt there NA. It does happen in 3rd as well, but its most pronounced in 4th when drivin gon back roads where the sound bounces off trees. I didnt want to post before I double checked. Could also be a vibration of somesort under the hood or downpipes, on and off of something....

 

even if it was oil starvation, we have solid follower buckets not hydraulic. could it be light knock? in those ranges the ecu is trying to hold the timing right on the verge of knock at around 35-40 degrees advance.
also, maybe lightweight pullies and clutch assemblies could not be dampening the piston firing shock and it is the trans gears rocking back and forth when under light throttle like that. hard to tell without actually hearing it.

 

it sounds mor elike knock than anything else.

 

I havent datalogged this when happeneing but I will and get back to you...

 

I went out today and played around with it. Its only audible(atleast only audible due to exhaust) at around 1300-2300 rpm's. I am almost certain it is preboost detonation as the car is at -10 vacuum when it does it. Any idea what i can do? I know with past vehicles i would just up the octane lvl of gas (regular to plus fuel) , but since this car runs super, i don't want to have to mix race gas and pump for every fill up. Would changing from the 380 injectors with the TN kit to 440's cause a problem like this?
edit:
I always called the sound i hear "valve tapping", but it is fact not valves at all. I had a rodea at one time that did this, and it was detonation. The regular fuel would ignite at the wrong time (i assume thats detonation) and cause the rattling sound. I believe in that particular vehicle it was due to carbon buildup, but who knows. When i would run super/plus fuel it wouldnt do it.
ALSO tested this on relatively flat ground, and it did it just the same. oil lvl is fine it was the first thing i tested.

 

For what it's worth, my stock NA engine would experience some sub 2500rpm knocking, if I was going up hill, heavy load, and in one of the upper gears. Downshift into the power band, and I imagine the noise will go away.

 

So nothing i can really do? Why isnt the factory sensor picking it up and pulling timing?

 

Most factory knock sensors only work within a specific RPM range..usually between 3000rpm and 5500rpm, where the chances of engine knock or most likely. So in the sub 2000rpm, there isnt much you can do, other than downshift.

 

So should I just keep the car above 3k in all gears except 1st?

 

It sounded like this was only occuring when going up hills and giving it a lot of accelerator input, below 2000rpm. Typically, when I am cruising around, my RPM's are always above 2000rpm, and usually in the 2500-3000rpm range.

 

sounds to me like a pre-turbo exhaust leak.

 

Well took the car in yesterday and had the guy who installed the kit ride with me to listen to the sound. He said it wasn't detonation, and was 99.9% sure its an exhaust leak or something loose. Thanks a lot guys for helping me out on this one.

 

Glad to hear that. Hopefully they can track down the leak quickly.