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Turbo Hose (Intercooler to Throttle)

Hi everyone,

I've been thinking about the metal pipe on our classic 900 turbos that runs from the stock intercooler to the throttle intake. The pipe is pretty restrictive both in terms of bore and shape, especially the more angular type on the 8 valve models with intercooler (Tii models).

The bore from the air box to the turbo and from the turbo to the intercooler are pretty wide, but the bottle neck is from the intercooler to the throttle.

I've done some measuring. The bore of the rubber connector hose going onto the intercooler is about 60mm and the bore of the rubber connector hose going over the throttle is about 70mm. The metal pipe, however is just over

60mm at the throttle end and a miniscule 40mm at the intercooler end. The rubber connector pipe actually steps up from that small bore to 60mm. What a waste! Surely some kind of pipe that curves from 70mm to 60mm in one go would be ideal. Would it really be that beneficial?

Okay, practicalities. A 90 degree 70mm bore silicon pipe at one end, a reducing 70mm to 60mm bore silicon pipe at the other end and a length of aluminium hose insert of the relevant length in the middle. Sound okay? This would give a full 70mm bore from the intercooler to the throttle, rather than the poor 40mm. Would that be better?

Would the silicon (say Samco or SFS) be of the right heat range? Samco make hoses that are suitable up to 170 degC. Is that sufficient for the air coming out of an intercooler?

Whatcha think?

Paul

1989 900 Turbo S
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Reply to
Paul Halliday
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Hmm, interesting thought. What's the max effective bore of the throttle body with the throttle wide open? Does the flap indeed go entirely horizontal or is it somewhat less than that? I would guess given the engineering that went into this car that a bottleneck which you surmise may exist probably doesn't... otherwise you'd have a lot of people putting bigger pipes on, and given the large number of production 900's (>900,000 worldwide) there would be sure to be kits available.

I know the rated steady-state turbine inlet temp (exhaust gas temp) of most variable vane modern turbochargers is around 750C... what the actual exhaust temp is I don't know, but I'd bet it would get hotter than 170C...

Reply to
Dave

40mm is very narrow - I've never owned an intercooled 8vT, so can't actually picture it - but it sounds a little tight.

Whether making it bigger would make a difference, I'm not sure. IME restrictions like this matter a lot less on turbo engines than on NA ones.

Having said that, I think if it was mine I'd be tempted to give it a try. Shouldn't be too difficult to do.

Reply to
Grunff

Salutations:

You know, of the many things that may be odd in a SAAB - I have always considered the turbo set-up to be second to none. I do not know, but I wonder if the restriction may be allowing for cooler airmass so that increasing the pipe size after the intercooler might reduce pressure and/or induce further turbo lag as pressure is built up in the larger pipe..

I know that they replaced a lot of the rubber parts on the classic 9000 air intake system with metal parts by 93/94 and I think they did so to eliminate variations in pressure, or to save money, or to make the system last longer - only SAAB engineering knows I suppose.

If I were (and may yet) be messing with modifying a turbo system - I would actually get a couple of lengths of cheaper hose to road test variations on pipe size - it may be that reducing the pipe would make the turbo snappier - but reduce total top pressure and perhaps fatally induce pressure too quickly in the system.

Currently, I trying to figure out if I can graft my 89 9000 turbo onto a

94 900 with a 2.3 non-turbo engine. It has a good old distrihutor so I can mess with the timing a bit. I think it may just be possible using a manually adjustable wastegate if I'm willing to do a lot of surgery on the header and perhaps replace the pistons - or not - perhaps it's just not reasonable as I've been assured by the good folks Abbot..
Reply to
Dexter J

in article snipped-for-privacy@eunomia.uk.clara.net, Grunff at snipped-for-privacy@ixxa.com wrote on 28/11/2003 22:49:

The rubber section from the intercooler actually steps down from 60mm to about 50mm (to take the OD metal pipe). 40mm actual bore in the metal pipe does sound very restrictive.

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This link shows my engine. The pipe with "turbo intercooler" written on it is the 40mm ID pipe. The rubber throttle connector pipe is 70mm ID and the intercooler end has the bore step-down connector pipe.

The other pipe from the turbo to the intercooler is also metal; presumably

40mm ID as well. I was thinking of replacing this one as well with a wider bore setup.

Okay? Presumably, the turbo can push a lot more air than the throttle/engine can gulp even if there is a 40mm pipe in the way :)

Not difficult. I think I can make it up out of parts pretty much any Motorsport shop. Just relatively expensive.

Samco & SFS both make turbo silicon (to withstand both pressure and temperature). What is the temperature that generally comes out of the end of a standard SAAB 900 intercooler?

Paul

1989 900 Turbo S
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Reply to
Paul Halliday

in article snipped-for-privacy@news.eastlink.ca, Dexter J at snipped-for-privacy@lamelamelame.org wrote on 29/11/2003 18:17:

Good points.

The pipe from the turbo to the intercooler is also metal and presumably 40mm bore. Not much point substantially increasing the bore after the IC when the bore before it doesn't match.

I think all things considered, I'm going to look into increasing the bore from the turbo to 50mm. That's about 2 inches and seems to match the exhaust end of the turbo.

Paul

1989 900 Turbo S
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Reply to
Paul Halliday

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