Hello again everybody,

I have been chasing down an intermittent, EAR PIECING vacuum leak / whistlin. Originally the TID kept popping off but after getting this resolved the whistle finally showed itself again on idle. Pulled out the stethoscope and seemed to be isolated to somewhere around these 3 metal *vacuum* lines?



I am curious as to what these lines are from? I’ve found a few pictures of S5 engines with block off plates and/or emissions deletes that do not appear to have these lines. What system is this part of, and would the rats nest delete remove this? What exact system would this be a part of?

This is NOT a daily so removing the emissions / idle control shouldn’t be an issue. I was planning on going aluminim TID and removing the attached emissions there but now that this issue appeared, I’m thinking I may be pulling the manifold. Trying to get some additional information before jumping into it.

 

After a midnight post I realized there is definitely some more info I can give lol

It is a 1991 GT-R. Fully stock except for APEXi Power Intake, catless downpipe, midpipe and APEXi N1 Dual Catback.

The only thing I had done prior to this was pull the BACV off and clean it and some of the intake as well, specifically the N370-13-24X intake pipe. This broke and needed to be replaced. After these 2, I still did not have an idle, ran a smoke test and discovered the clamp on the TID coming off, which is now resolved. This brought my idle back, but with a whistling. I thought TID again ran a smoke test and it was, the clamp I bought needed to be modified for the tabs on the end of the factory TID. This is done and ran a smoke test confirmed no leak on the TID. But the whistle is still there, arguably louder. I didn’t have much time to mess with it or take a video but we put the stethoscope up right against these 3 metal lines and it did seem like that’s where it was coming from.

I don’t have much else though. I’m still on the factory ECU and to my understanding, certain things cannot be deleted unless you have a standalone. Right now, the budget could support a piggyback such as SAFC but I’m not sure if this would be enough to cover the emissions deleted. Again, this is NOT a daily, it’s going to be built over time probably more in the street / drift direction. FMIC and aluminum TID are already in the plans but that was because I originally thought this was from the TID. Now I’m not sure.

TBH, i did NOT intend on doing the rats nest delete. But if it removes these metal lines or makes this easier to trace, I’m game.

Also, I did delete the cats, and didn’t do anything with the split air pipe, or air pump. I’m new to all of this so not sure if this would have any whistling effect but I have been reading that the split air pipe is unnecessary without cats. Unnecessary is fine, but would it possibly cause something like this? Me and a few buddies of mine been trying to trace this down for a little under 2 months now.

 

those three lines go from the solenoids to the Air Control Valve ACV, which is right under them.

 

pinch each hose off with needle nose pliers, one of the diaphragms likely has gotten old and cracked internally causing a vacuum leak you can't see. the first to get old and leaky is usually the EGR valve, which is on the backside of that picture and has it's own hose not visible in that picture. You can also verify it by testing them with a vacuum pump.

 

thank you for the response, that’s definitely worth trying as well. but i was under the assumption i don’t have EGR ? on a S5 jdm

 

You're correct. The S5 does not have an EGR valve. The purpose of the EGR valve was to recycle exhaust gas back into the combustion chamber to reduce the combustion temperature, which would in turn lower the NOx emissions. The NOx emissions were never a problem on the rotary engine due to it's high internal recycle ratio.

 

Right, the S5 doesn't have it, i didn't look too hard at the picture to notice.