RB25DET Neo Cam Gears?

[Dyzzii]

Hi guys

I've been lead to believe by my tuner that my VVT cam gear is making some noise. Around 5000rpm every single pull a noise is picked up by the knock sensor, which keeps going until about 5500rpm at which point it stops, and the ECU sometimes thinks it's knock and pulls timing to compensate. Tuner seems to think it is my intake cam gear, and believes it may be getting a bit noisy for some strange reason. Noise has been described to me almost as a "ddddrrrrrrdrrrrrdrrrrdrrrrrrrrdrrrrrrrr" (best way I can describe it on here) and happens every single pull. Can only be heard through the knock sensor which makes diagnosing it a real pain, as putting it on the dyno every time I replace a component is not even remotely practical. Normally this would not bother me enough to pursue, but because it is affecting how the car drives on some pulls, it's not something i'm happy to leave alone.

He has also suggested that it could potentially be a lifter, but that seems very unlikely as these cars have solid lifters off memory. 

So I contacted Nissan, and am unable to get a brand new intake cam gear for less than $1,200 which is absolutely absurd. So i'm now contemplating other solutions to my problem, and have been thinking I would actually be better off going aftermarket cams with adjustable cam gears. However my setup is still relatively stock with a few bolt ons (front mount, exhaust, cold air intake, nistune ecu, stock turbo, stock injectors etc).

So my questions really are:

1. Are there any other suggestions for what this noise could be?
2. What other solutions would I have rather than paying $1,200 for a gear from Nissan?
3. Would going cams on a setup as stock as this even be worth it?
4. How much power would I lose if I just went adjustable cam gears on the stock cams?

On a side note, I have recently replaced the cambelt with a GATES timing kit as I was lead to believe that could have been the culprit. Mechanic told me the previous cambelt had not been done very well, and had likely been overtensioned. So this rules out the cambelt or any related tensioners to it, but could reinforce the idea of the cam gear being the culprit?...

Appreciate any and all feedback!

 

[Rusty Nuts]

What other solutions would I have rather than paying $1,200 for a gear from Nissan?

part No. 132025-5L301 should be what you need. Available from AMAYAMA approx $854  14 days delivery but run your vin number to be sure.

 Mechanic told me the previous cambelt had not been done very well, and had likely been overtensioned. So this rules out the cambelt or any related tensioners to it, but could reinforce the idea of the cam gear being the culprit?... This statement set the bullshit meter to high. The camshaft sprocket rotates on a substantial journal which is how the VCT moves it. It is more likely the VCT internals are making the noise...they are not rebuildable

 

[Rusty Nuts]

Have you tried replacing the front knock sensor they rarely go wrong but shit happens.

[AngryRB]

Strange the noise is only at 5k, when mine needed replaced it was rattling loud at cold start idle speed.. 

I got mine thru kudos motorsport around the $850 if I remember correctly.

[Dyzzii]

11 hours ago, Rusty Nuts said:

Have you tried replacing the front knock sensor they rarely go wrong but shit happens.

Appreciate the replies I will look into the part! And no I havent replaced the knock sensor. It appears to be working as intended so have had no reason to replace it. My main concern is that is a massive amount of cash to fork out to only “potentially” fix an issue. But I may just have to bite the bullet.

1 hour ago, AngryRB said:

Strange the noise is only at 5k, when mine needed replaced it was rattling loud at cold start idle speed.. 

I got mine thru kudos motorsport around the $850 if I remember correctly.

No audible noise whatsoever at idle or outside the car. Listening to it pulling on the dyno you’d never know and the power/torque curves are fine which makes it even stranger. I’m worried at the fact he thinks it “might be” the culrpit. So difficult to diagnose as every time i replace something it would have to be chucked back on there to listen for the issue again.

[Rusty Nuts]

I agree with Angry RB the noise from mine was generated at idle only, But I had a spare engine and swapped over VCT.

 

[Rusty Nuts]

Once came across a Neo that had a lifter bucket that would "cock" slightly in the bore and jam a few thou low which caused the lobe to slap hard against the shim. Changed the shim and it stopped doing it. The old shim had a substantial mark on it.

[Rusty Nuts]

Mate, don't discard the faulty knock sensor suggestion. Search this site for Faulty Knock sensor there are eight pages of issues experienced , some very similar to what you are experiencing

[Dyzzii]

12 minutes ago, Rusty Nuts said:

Mate, don't discard the faulty knock sensor suggestion. Search this site for Faulty Knock sensor there are eight pages of issues experienced , some very similar to what you are experiencing

You think the knock sensor could potentially just be having a meltdown and pinging which is what he is hearing? That would make life a hell of a lot easier.

1 hour ago, Rusty Nuts said:

Once came across a Neo that had a lifter bucket that would "cock" slightly in the bore and jam a few thou low which caused the lobe to slap hard against the shim. Changed the shim and it stopped doing it. The old shim had a substantial mark on it.

This has completely lost me here haha, i know a fair bit about the workings of motors but am lost as to what you’re talking about here haha. Any more idiot-proof way of putting it?

so you’re thinking is it’s more likely to be something else rather than the cam gear, as most past experiences had an audible noise at idle?

Thanks heaps for your help so far too.

[Dyzzii]

Oh wow have had a read of the knock sensor threads. Only thing is my tuner can hear it when listening in through headphones to the sensor? Or would the sensor potentially be magnifying the feedback that was just normal engine vibration and that’s what he’s hearing?

i’d think he’d have suggested this to me though? He has a hell of a lot of experience with skylines and is a very respected tuner in NZ.

[Rusty Nuts]

 

The knock sensor is tuned to detect the engine knock/detonation frequency, when they shit themselves they detect other frequencies as knock. Your tuner is hearing noise which is possibly fooling the sensor (and him?)

[Ben C34]

1 hour ago, Rusty Nuts said:

 

The knock sensor is tuned to detect the engine knock/detonation frequency, when they shit themselves they detect other frequencies as knock. Your tuner is hearing noise which is possibly fooling the sensor (and him?)

That's assuming he is listening to the factory sensor. Ask if he used it or his own sensor when tuning to rule out this possibility.

[Rusty Nuts]

I'm assuming nothing of the sort, regardless how the tuner is listening its the output of the factory knock sensor that is signalling the ecu to pull timing

[Dyzzii]

21 hours ago, Ben C34 said:

That's assuming he is listening to the factory sensor. Ask if he used it or his own sensor when tuning to rule out this possibility.

I believe he is using the factory sensor.

Do you guys happen to know what sensors are compatible for the 25det neo? Can i just get any neo knock sensor as a replacement? Or must it be 25det? 

[Dyzzii]

19 hours ago, Rusty Nuts said:

I'm assuming nothing of the sort, regardless how the tuner is listening its the output of the factory knock sensor that is signalling the ecu to pull timing

Yeah that makes sense. Just weird to not have any CEL's or anything like that, but from what those other threads said it doesn't appear that they throw codes. Am I right in saying there are 2 knock sensors on the car? And if so, would you recommend replacing both of them, or just the one he is listening in on? May have to look around some wreckers for one and fingers crossed it helps!

[Rusty Nuts]

Yep, there are two, the most common ones used are Part No. 2206059S00 they are used on multiple Nissan engines RB's and VG's. New between $160 and $180 but grab a couple from the wreckers, take one of yours as a sample. I'm running RB30 ones in my 25/30 and ecu is happy. There's a pair for sale on ebay for $14 the guy is in Bundaberg gotta be worth two schooners.

[Dyzzii]

3 hours ago, Rusty Nuts said:

Yep, there are two, the most common ones used are Part No. 2206059S00 they are used on multiple Nissan engines RB's and VG's. New between $160 and $180 but grab a couple from the wreckers, take one of yours as a sample. I'm running RB30 ones in my 25/30 and ecu is happy. There's a pair for sale on ebay for $14 the guy is in Bundaberg gotta be worth two schooners.

Bugger i’m from New Zealand . I’l have to scout a few wreckers out online from here and hope to come across some. Am tempted to just go brand new to eliminate the issue but I guess that’s pointless as I still don’t definitively know what the issue is!

Thankyou heaps for your help so far. Will likely have sorted some by the end of the week. Only issue is i’l have no idea if they’l fix the problem until its back on the dyno

[Rusty Nuts]

Why not a nice bit of straight road surely you could feel the timing being pulled.also( Maybe the guy on ebay posts to NZ)

Edited January 1, 2019 by Rusty Nuts

[Dyzzii]

17 hours ago, Rusty Nuts said:

Why not a nice bit of straight road surely you could feel the timing being pulled.also( Maybe the guy on ebay posts to NZ)

I’ve never actually felt the timing pull noticably. To me it feels smooth and constant. I don’t believe it pulls timing every time, just occasionally.

[Rusty Nuts]

Fair enough, wish you the best of luck with it mate and hope its a cheap fix.