Rb25de Metalic Resonating

[GTS4WD]

Hey guys.

I just transplanted an RB25DE (with VCT) in my S. This new engine under load has a strange metallic noise around two and three thou RPM, more like two metal parts being in contact and resonating. It always occurs around 2-3K then goes away. It seems to settle down slightly when the engine reaches operating temp. The noise is the same even with VCT solenoid disconnected.

The noise appears to be coming from the exhaust, yet I removed all shields and is still there. Noise could transmit though from the engine.

The spark plugs are very clean and white, so there seems to be no valve problems. The car accelerates and idles very smoothly. Fuel consumption for this new engine seems to be higher than what it should be (although these issues may not be linked).

Any ideas to what it may be and how to fix?

Thanks in advance =]

[nick81xd]

could be either one of ur mufflers have collapsed. or your cat. hit them to see if it rattles that or check for loose bolts or washers

[Eug]

no idea what it sounds like... but if it is what i think you're trying to describe then it's a typical inline 6 twin cam characteristic... the m3 has a slight metallic raspy sound (and yes i have heard one in full song in real life) - and although not comparable, it is quite distinct.

try to put a sound file up... easier to diagnose

[GTS4WD]

could be either one of ur mufflers have collapsed. or your cat. hit them to see if it rattles that or check for loose bolts or washers

Done that.. Exhaust is fine. Nothing rattles.. no loose bolts.. only thing I found once I took off the sheilding was a small rock. Muffler and cat have no noise at all.

Ill try getting a sound file

[NA_R33]

Im going with eugene, mine sounded terrible till i got a proper exhaust put on it, its a twin cam thing, do a search on exhausts in this section to get a better idea of muffler, resonator and pipe diameter to fix the problem. I also learned the other day, like a resonator a pipe can be added perpendicular to ur normal exhaust just to act as another expansion chamber.. honda uses this to deal with the twin cam resonance.

[GTS4WD]

Unfortunately I cannot import a sound clip from my phone to my copmputer.

Is there anywhere I can hear a 25DE engine? On a video or sound clip to compair the two?

As per before.. just sounds like metal clipping.

[Greg]

It could be your gearbox. I ran my car with the rubber gear boot off once, and the noise was extremely loud and it was obviously coming from the gearbox. Nothing to worry about. Could see if changing your oil improves it. Check that your gear boot is fitted properly.

[R33GTS25]

I have that sound too. Ill try get a sound file now.

[GTS4WD]

It could be your gearbox. I ran my car with the rubber gear boot off once, and the noise was extremely loud and it was obviously coming from the gearbox.

But why would the resonating be between 2-3 K? If it was the G-box.. wouldnt it be throughout all RMP range? And Im pretty sure its from the engine. When we opened the G-box it was in pretty good nik. It seems like its comming from the engine and all simptoms seem to point that way. Thats why Im so freaked out about it.

I have that sound too. Ill try get a sound file now.

Much appreciated brother bear!

[Greg]

But why would the resonating be between 2-3 K? If it was the G-box.. wouldnt it be throughout all RMP range? And Im pretty sure its from the engine. When we opened the G-box it was in pretty good nik. It seems like its comming from the engine and all simptoms seem to point that way. Thats why Im so freaked out about it.

no. it hits its natural frequency at this rpm range, hence making the noise.

[adoboy666]

I have the same noise with my r32 gts25, it has the rb25de as well and is making the metallic noise around the same rev range. I have only just started noticing it within the past 2 weeks( have had my licence for a month now lol)

my exhaust seems to be running quite hot as well, but not hot enough for the exhaust overheat light to come on.

Ill check my cat and exhaust out on the weekend anyway.

Ps i have an auto gearbox and flushed it out as well as the torque convertor and replaced with new fluid but still sounds the same.

[ignuz]

Does it sound like this?

[GTS4WD]

YES!..

But without the sexual exhaust note..

Got my papa bear to drive it today.. its freakin LOUD!.. the metalic resonating is just like the one you showed.. but just much louder and somehow.. nastier sounding..

I take it by the replies that its just a normal sound?

It has a stock RB20DET exhaust with the slightly bent R33 25DE connector from the headers to the exhaust flange. Does anyone see anything wrong with this?

Much appreciated sound clip

[dyken]

i had the same thing realli realli badly i changed my catback now it sounds sweet as

[ignuz]

What size is your exhaust GTS4WD anyway now that you did the transplant?

[GTS4WD]

What size is your exhaust GTS4WD anyway now that you did the transplant?

I transplanted a Rb25DE from a 4wd Stagea into my R32 GTS4 which had an RB20DET. It has a stock 20DET exhaust. The only difference is that I used an R33 connector pipe from a RB25DE to connect the headers to the stock RB20DET exhaust.

[GTS4WD]

if anyone still cares.. This metalic resonating is a common problem in early RB25DE's.. It causes absolutely no damage to the engine/exhaust.. The only way to get rid of it is a cat/exhaust/muff.. or bear they annoying very loud rattle..

Advan (in Syd) + 1 point!

[Eug]

what's the source of the problem?

i still stand by the inline 6 twin cam characteristic; cam related or something.

[GTS4WD]

The way it was explained to me is that:

"all engines make noise due to moving parts/rpm/mods etc..

Most engines sound different, they have different mechanical characteristics and that makes them sound diff..

early models of the RB25DE have that loud metalic raspy resonance due to the way the engine was designed"

Its a shit load louder than a raspy cams sound.. Got a mate to drive it the other day so i could hear it from the outside..

its LOUD! i mean FREAKING LOUD! it resonates through the whole exhaust and is amplified and expeled out the end.

In the later Rb25DE's there was a small flap that was kept closed at row rpm and opened at WOP and higher RPM to help keep the noise of it to a minimum.

An exhaust/muffler will cancel the sound, hence there arnt any/rarely do modded 25de's have the sound. Couple it with a new exhaust, and it disapears completely.

So yeah, its just a natural characteristic that 25de's have. Its similar to cams on full symphany, but a million times louder, and out the exhaust.

Theres no mechanical defect with the engine/exhaust. It causes no damage and will not harm the engine.. its just there..

hope this little bit of info helps anyone in the future..

[Eug]

oh yeah well i guess we all pretty much agree on that then. but it's not a "problem" as such, just a characteristic...