Miki

I have the following problem, my MY98 boosts very nice (1.2bar) until it reaches about 5500rpm, then the boost starts to drop. If I keep my foot down it keeps dropping all the way down to around 0.5bar @ 8000rpm.
Same problem in all gears, except maybe the 1st, it's a bit hard to tell.
If I set max boost to around 1.0bar it might run very nice all the way to the top, but not always, even with a setting as low as this it might drop after 5500rpm...

I've tried swapping the following parts, without any noticeable improvement:
- turbo (used to be a VF35)
- ECU (have tried STi v. IV mapped by Prova and original STi IV)
- headers (changed from OEM headers to GT-Spec)
- boost controller (have tried OEM, manual and Blitz EBC, no difference)
- intercooler (from WRX MY02 to Hybrid FMIC)

The VF22 is used and hasn't been checked, but the VF35 was checked, same problem. Last time the car was on a dyno (previous owner) they noticed the wastegate was shut (yes shut, not opened!) when this happens.

So, I'm now wondering about the Samco inlet hose, if it could be collapsing? I've read that some have experienced this, although it seems almost unbeliavable that it would collaps with an open K&N filter.
Any way to test this, other than on a RR? I could of course try to fit another pipe inside the samco one...... but..... whereabout is it that it has been noticed to collaps, is it at it's narrowest part, or?

Or, is it the VF22 that can't handle the thing, I've understood that they should be modified, but how ?

Here are some specs of my car:

- STi VII Shortblock
- STi IV ECU, mapped by Prova
- STi IV AFM
- STi IV inlet temperature sensor
- STi II camshaft + stiffened springs 37/72Kg
- 480cc injectors
- IHI VF22
- Ramair 110mm / K&N open filter
- 3" DownPipe + 3" catless exhaust
- Walbro (255l/h) & FPR
- Hybrid FMIC
- Samco inlet pipe
- GT-Spec headers + Uppipe + Thermo tech

The last dynorun resulted in around 350hp/477Nm @ 1.22bar boost, but the boost started dropping at about 5500rpm. 1.0bar resulted in around 330hp, no drop. Here are the results:
http://www.subaruclubfinland.net/kuv..._impreza98.jpg

Under the hood:
http://www.subaruclubfinland.net/kuv...mpreza98_3.jpg

Bob Rawle

How old is the Samco, its almost certainly the problem, these used to be renowned for it, Samco have improved the construction ltterly and solved it but you may have one of the intake pipes that does this.

bob

Miki

Bob, tnx for your prompt reply !

I dunno how old it is, but my guess is that it could well be 2-3 years.

Was it a specific part of the pipe that collapsed, or just random, or was it the whole thing?
I was thinking about moving the power steering container to another spot and that way replacing part of the inlet pipe, i.e. the actual bend. Maybe that could help if the problem is where the pipe does the 90'ish degree bend around the tank?

Or, should I just ditch the Samco pipe and get another one, or even put back the OEM one???

Bob Rawle

If its of that age then suggest replacing with a latest version, it collapses just in front of the turbo inlet, if the car was on the dyno and the bonnet up you would have been able to see this happening. As you are the OEM would be better at that.

bob

Miki

Yes, I haven't taken the car to a dyno myself yet, and the previous owner just didn't know to look for this when they where dynoing the car.

Guess I need to have a custom inlet pipe made then, one that won't collaps, no matter what...

Thanks again Bob !

Floyd

iTrader: (9)

Or you could try putting a large jubilee clip around the pipe at the weak points. You may find that the clip will force the pipe into a circle, which will resist collapsing. It'll take you five minutes to fit and cost not very much to try. Obviously don't tighten too much that you squash the pipe

Aren't I nice

F

Miki

Heh, I was actually thinking of something in that direction.
The space around the pipe is a bit limited, tho, but maybe there's just enough space to fit something around it. It's probably more of a problem to get my hands down there and be able to fasten it....

Miki

Problem solved, or at least now I know whats is causing it.
Thanks for the good advice guys !!!!.
I managed to slip a clip around the hose, and also to push the pipe ~5mm more onto the neck of the turbo. This helped for now, but the problem will certainly return, at least the clip won't stay there for too long...

Bob Rawle

Sorry but putting a clip around the outside won't stop it collapsing inwards will it ? thats not going to fix it.

The latest Samco pipes do not collapse.

bob

StickyMicky

for the hose to collapse inwards would it not tend to bulge and go into a oval shape??

i could imagine a clip around the area that bulges and ovals would do the job, thats if it bulges and ovals

Miki

As I said this is definitely not a longterm fix, but at least I now know where the problem is.
Hmm.... maybe they'll give me a refund in exchange for a new one at Samco if I send them this pipe....

EDIT:
What inlet pipe do you guys suggest? I made a search and found out that there's at least a MRT one. There were tohers as well, but at least some of them might be Samco just sold with another name?
And when you know what to buy, the next question is obviously "where can I find it" ?

Bob Rawle

Ring Roger Clark Motorsport

bob

R19KET

Cheapest, easiest way to solve it, since the pipe is no good anyway, is to cut it at the weak point, and fit a tube insert, with a couple of jubilee clips.

Mark.

rroberrto

I found the collapsing inlet no longer an issue after wrapping couple of layers of heat-ressitant tape around it's waist (the part hidden beneath the inlet manifold) to even out the negative pressure in high boost situation. You'd be amazed how much reinforcement these tapes give by trying to squeeze the tube before and after.

Robert

Jack0

I have had first hand experience of these Samco pipes as Bob knows from old!
Ditch this pipe NOW!
I wasted so much time with this pipe in the past.
Get the uprated one as Bob has repeatedly indicated or replace it with a tea bag!

Jack0.

XNWRX

I've had this problem on my STi7 using a Perrin inlet hose (brand new one) !
To check, just remove your air filter and close the air inlet before the MAF using your hand (the less air will get in, the more prone to collapse will be the hose). Then operate the throttle body with the other hand so you reach the RPM point where you will see the hose collapsing (I've also seen that the stock hose part between the MAF and your aftermarket turbo hose started to collapse as well !).
My solution :
Cut the hose at the weak point (which in my case was just before the dump inlet on the pipe), and fit a 63 mm tube inside (exhaust pipe is ideal), then secure it with a couple of jubilee clips.
Works fine ;-)

AvalancheS8

Presumably though in order for there to be enough vacuum to collapse it there must be some reasonably serious restrictions in the inlet tract before the intake pipe. If these were sorted out so that the inlet tract didn't run with so much vacuum there would be no problem. Has anyone tried sorting it this way and killing 2 birds with one stone by improving the inlet efficiency at the same time ?
i.e, by doing this kind of thing...

David_Wallis

i would expect samco to swap this.. but a jubilee clip will stop a hose collapsing to a point.. would take a lot to shut one.. marks solution works though...

David