Crossover pipe

Cory9584 · 11-03-2005, 02:17 PM

Im just wondering if theres any more power or less lag from upgrading the crossover pipe size?

IanS · 11-03-2005, 02:20 PM

Not unless you have a huge turbo. People have had success wrapping it in header wrap to keep the heat in, though. It helps spool a bit and will keep your engine compartment a bit cooler.

Upgrading your downpipe/cat/exhaust will get you more power and more spool.

Porsche-O-Phile · Porsche-O-Phile's Garage

Why in the name of God they didn't add a heat shield above the crossover pipe is beyond me. . . I'm willing to bet a good percentage of rear seal/oil pan gasket failures are due to the heat from that thing. . .

Zero10 · 11-04-2005, 07:19 AM

P-O-P, you think so too! Especially if you sit in traffic for a while. I'd go as far as saying it can't be good for the steering rack, oil pan gasket, RMS, balance shaft O-rings, etc.

Then again, they did put the turbo almost against the block under the intake, so who knows what they were thinking....

Lawrence Coppari · 11-04-2005, 10:35 AM

There is a heat shield at the turbo between it and the block. The last foot of the line feeding the turbo is double walled with an air gap (annulus) between the two walls. That is insulation.

Zero10 · 11-05-2005, 08:43 AM

Yeah, but the air gap is not open at the ends, so it just sits. So if you're in heavy traffic, it's almost as bad as not having it at all. Heat-wrapping it would be a good solution however.

I don't recall there being a heat shield between the turbo and the intake manifold, that's what I meant, that and putting a turbo only a couple inches from the block is just a bad idea in my books. I don't understand how they managed to make the engine bay so damn tight on these things.

IanS · 11-05-2005, 10:41 AM

Too much piping. Turbos always add extra piping and they exacerbated the problem by putting it on the wrong side of the car.

I keep hearing about people coming out with kits which move the turbo to the correct side of the engine, but it never seems to happen. I think you'd have to move some major stuff over, maybe even the engine itself, to make enough room.

Zero10 · 11-05-2005, 06:00 PM

The callaway kit had the turbo on the right side.
Really, what they need to do is find a way to mount the engine upright, that would free up a LOT of room.
I like the idea of having the intake and exhaust on the same side, with the manifolds mounted together, and the turbo bolted straight onto the manifolds. Very compact, but no chance for an intercooler that way.

nynor · 11-06-2005, 08:39 AM

i've been toying with the idea of wrapping my headers and my cross-over pipe. any thoughts?

IanS · 11-06-2005, 10:17 AM

I'm planning on wrapping my crossover at some point when all my oil leaks are fixed. Apparently its hard to do with the crossover on the car, but it doesn't look that hard to me. Maybe an hour of work?

Since the headers already crack easily, some people are wary of wrapping them, though I've heard of people using header blankets on them, which are also quite easy to install, which is nice.

AaronM · 11-06-2005, 10:38 AM

Quote:

Originally posted by IanS
Too much piping. Turbos always add extra piping and they exacerbated the problem by putting it on the wrong side of the car.

Yeah, keeping the turbo and the intake charge cooler is such a terrible idea.

The goal was to increase the life of the turbo, and that was clearly successful given the comparison of expected turbo life of the 930 and 931 to the expected turbo life of the 951.

IanS · 11-06-2005, 11:51 AM

It keeps the turbo cooler, but the intake warmer, since the intake manifold and all the associated parts are sitting above the turbo, xover pipe and downpipe, baking.

The expected turbo lifetime on these cars is quite amazing, especially given that most owners don't use synthetic. But it is on the 'wrong' side of the car from a power/spool/etc perspective.

Both the intake and exhaust piping would be shorter if the turbo was on the exhaust side and all the rubber bits under the hood would last a lot longer.

A reliable turbocharger on an aircooled car is going to be a difficult proposition because water cooling a turbo tends to give it much better longevity.

AaronM · 11-06-2005, 03:45 PM

Quote:

Originally posted by IanS
It keeps the turbo cooler, but the intake warmer, since the intake manifold and all the associated parts are sitting above the turbo, xover pipe and downpipe, baking.

The expected turbo lifetime on these cars is quite amazing, especially given that most owners don't use synthetic. But it is on the 'wrong' side of the car from a power/spool/etc perspective.

Both the intake and exhaust piping would be shorter if the turbo was on the exhaust side and all the rubber bits under the hood would last a lot longer.

A reliable turbocharger on an aircooled car is going to be a difficult proposition because water cooling a turbo tends to give it much better longevity.

I'd rather replace $100 of rubber bits and take a small hit on spool-up than replace $2,000 of turbo...

The rubber takes a lot less labor to replace also.

Aaron

IanS · 11-06-2005, 05:42 PM

No turbo I can think of is $2000, even new. And if the turbo was located in a reasonable location, its typically only 2 or 3 hours of labor to swap it out.

I can't think of a single car that has the turbo where the 944 turbo does, and its not just because of easier packaging.

No car is designed perfectly in retrospect, and the turbo location is probably the most obvious flaw with the 944 Turbo. I'm sure it seemed like a wise choice for the sake of turbo longevity at the time, but it was an overly conservative choice in retrospect.

nynor · 11-06-2005, 06:47 PM

god bless the german engineers! my brother went through two turbos in a year in his subaru from the same time period (late '80's). i'll take my conservatively engineered 951, thank you very much.

long live my turbocharger!!!

AaronM · 11-07-2005, 05:58 AM

Quote:

Originally posted by IanS
No turbo I can think of is $2000, even new. And if the turbo was located in a reasonable location, its typically only 2 or 3 hours of labor to swap it out.

I can't think of a single car that has the turbo where the 944 turbo does, and its not just because of easier packaging.

No car is designed perfectly in retrospect, and the turbo location is probably the most obvious flaw with the 944 Turbo. I'm sure it seemed like a wise choice for the sake of turbo longevity at the time, but it was an overly conservative choice in retrospect.

So because I happen to agree with Porsche's decision (while admitting the tradeoffs that is induces) I am somehow wrong? Honestly, God help the person who comes on here and ever presents a reasoned view to counterbalance the screaming hysterics. It's worth noting also that the intake charge temperature on the 951 is well below the intake charge temperature of the 931.

You find me a new K26/8 for cheap then if that's so common and easy to do.

IanS · 11-07-2005, 08:10 AM

I didn't say you were wrong. I said the turbo was on the wrong side of the car, which I say both in reference to the modern standard of putting it on the exhaust side and in my opinion, and that it appears an overly conservative choice in retrospect.

You're not wrong for liking it where it is any more than I'm wrong for wishing they'd put it on the exhaust side. We both see the tradeoffs differently and I'd accept the tradeoffs I see by moving it and you're not as keen on them.