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Metal vs Stock AFM Pipe

SeriesIIGTST
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SeriesIIGTST Mentor

SeriesIIGTST

Posted
Posted

Hi,

I was told by a mate that I should replace the stock pipe from my AFM to my turbo with a solid metal pipe as apparently the stock rubber one will actually suck inwards when my turbo boosts up. Especially now that I've got an aftermarket turbo and running more boost.

What are your opinions on this? Is it worthwhile? I guess any exhaust shop/speed shop would be able to make this pipe up?

Car is R33 GTS-t

Cheers!

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GTR32 Rising Star

GTR32

Posted
Posted
Hi,

I was told by a mate that I should replace the stock pipe from my AFM to my turbo with a solid metal pipe as apparently the stock rubber one will actually suck inwards when my turbo boosts up. Especially now that I've got an aftermarket turbo and running more boost.

What are your opinions on this? Is it worthwhile? I guess any exhaust shop/speed shop would be able to make this pipe up?

Car is R33 GTS-t

Cheers!

A lot of turbo intake tubing has a spiral wire in it to stop this from happening. Some people remove it because they think it wil improve flow, not realising that they are achieving the opposite. Unless you are having air flow limitation issues, in which case you probably need to look at the intake system as a whole (no pun intended!), save yourself the hassle.

rev210 Grand Master

rev210

Posted
Posted

On the R33 gtst the spiral rubber tube is very similar to the VL turbo unit. If you bin it and replace it with a metal or PVC pipe (cheaper) you may expect 7hp+ gain on the factory turbo. Thats more power than from upgrading the airfilter.

The metal spiral is to help stop the pipe from colapsing, the rasied bumpy ridges that go with them are to allow for pipe flex movement and they are the part of the design that sucks or should I say prevents suck.

PVC pipe and a heat gun and some rubber elbows will do the job.

Sydneykid Grand Master

Sydneykid

Posted
Posted
Is their a particular boost level or engine power output where this problem starts to occur or is it more of a case by case basis ?

My experience has been it is more of a question of "age and condition" than boost or power level. I have had a 210 rwkw (1 bar) car suck it closed and I had a 260 rwkw (1.3 bar) one that didn't. I have not ever seen a problem at 200 rwkw or less, so if you are under that it is probably OK.

Roy Grand Master

Roy

Posted
Posted

Sydneykid, what air filters were they running?

My thinking... :) there is no way air flow makes the inlet pipe collapse (physics i suppose), so its not boost or turbo size related. So its the vacuum from the turbo, but in order for their to be a vacuum in the inlet system there must be a restriction upstream, ie the filter

If there is an open pipe (ie no filter) then you will never see the pipe collapse. Now obviously there has to be some sort of pressure drop accross the filter (i suppose we are aiming for negligible), but perhaps by sticking with the same filter that causes the std pipe to collapse, but replacing with aluminium pipe etc... then its actually a band aid fix for a shoddy/dirty air filter that is causing an inlet restriction -> vacuum->pipe collapse. Get a better air filter free up the restriction and there wont be a vacuum in the inlet...

Dont knoe how true the above is, just soem thoughts... thinking can be a dangerous thing with a hangover. :headspin:

Busky2k Veteran

Busky2k

Posted
Posted

Dont forget Roy, it gets bloody hot in the engine bay, considering the pipe is right next to the turbo so it could soften quite a bit methinks. My SR20 doesnt have a spiral wire to help support it but I still think its strong enough to prevent collapsing. But one thing for sure, it has all those corrugated surfaces and irregular diameter which would hurt flow by quite a bit. (BUt still not as restrictive as the pesky 50mm SR20 AFM!) So I think it would be worth replacing with a mandrel bent pipe to address those problems, especially if you upgrade to a Z32 AFM/bigger turbo.

Roy Grand Master

Roy

Posted
Posted

Yeh, but even if the thing gets hot a malleable (spelling?), you still need negative pressure/vacuum fo rthe pipee to be sucked closed. Eleminate the negative pressure and the pipe cannot physically be sucked in/collapse.

As for replacing yeh sure, go ahead, just making the point that the cause coulc be an inlet tract problem that may be costing you power...a metal pipe is a fix, but perhaps not a fix to the actual problem...just a means of masking the pobolem.

rev210 Grand Master

rev210

Posted
Posted

forget the pipe collapsing issue for a moment (it does happen, possibly due to the rubber getting old). The extra power I mention is to do with the airlow restriction the factory unit has vs a good replacement pipe, on a stock turbo at factory levels of boost. More power is at stake when you up the base performance.

Zombie Collaborator

Zombie

Posted
Posted
So its the vacuum from the turbo, but in order for their to be a vacuum in the inlet system there must be a restriction upstream, ie the filter

If there is an open pipe (ie no filter) then you will never see the pipe collapse. Now obviously there has to be some sort of pressure drop accross the filter (i suppose we are aiming for negligible), but perhaps by sticking with the same filter that causes the std pipe to collapse, but replacing with aluminium pipe etc... then its actually a band aid fix for a shoddy/dirty air filter that is causing an inlet restriction -> vacuum->pipe collapse. Get a better air filter free up the restriction and there wont be a vacuum in the inlet...

My thoughts are that the pipe itself is a restriction and hence creating vacuum.

So I am guessing if you truely want minimal vacuum you would run no intake piping at all, just open air turbo. But we dont live in a perfect world.

Adam

Black33 Proficient

Black33

Posted
Posted
My thoughts are that the pipe itself is a restriction and hence creating vacuum.

So I am guessing if you truely want minimal vacuum you would run no intake piping at all, just open air turbo. But we dont live in a perfect world.

Adam

the pipe itself can't be the restriction, as was said, you would need a restriction upstream, ie air filter to cause a vacuum in the pipe and collapse it.

(start motivational talk) I think it's a great idea to replace the rubber pipe, it would be very easy to make up a steel pipe composing of a few bends and straight bits of pipe, joined with silicone joiners and hose clamps. All we would need is one person to make up a couple of sketches with seperate pipes with lengths and bends required and it would be a make it yourself kit for everyone to use. (end motivational talk)

:D

Roy Grand Master

Roy

Posted
Posted

Im not saying dont replace the pipe, im just saying be sure your air filter isnt the reason its happening.

Imagine the flexi hose part on your vacuum cleaner at home. Turn the thing on and the hose is fine...cup your hand over the end of it and it will want to suck close....now getting rid of that flexi pipe and using metal tube will stop the tendency for the pipe to collapse, but doesnt remove the restriction my cupped hand places on the inlet.

Is my analogy make any sense?

Black33 Proficient

Black33

Posted
Posted
Im not saying dont replace the pipe, im just saying be sure your air filter isnt the reason its happening.    

Imagine the flexi hose part on your vacuum cleaner at home. Turn the thing on and the hose is fine...cup your hand over the end of it and it will want to suck close....now getting rid of that flexi pipe and using metal tube will stop the tendency for the pipe to collapse, but doesnt remove the restriction my cupped hand places on the inlet.

Is my analogy make any sense?

I totally agree, but I also think it is a god idea to change the pipe as the corrugations in the rubber pipe around the bend, can't be too good for the flow.

Also, the cast piece at the end of the pipe from the intercooler to turbo intake looks tiny in my opinion - it's gotta go.

SeriesIIGTST Mentor

SeriesIIGTST

Posted
  • Author
Posted

So the consensus is that it's probably worthwhile anyway, regardless of whether there is a restriction further up the line. However, the restriction should also be addressed by fitting faster flowing filter.

So that leads onto is there a proven brand of filter which flows well but still filters things smaller than a bird (unlike HKS)

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