924Board.org

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Yeah, what he said!
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Paul · Posted: Thu Nov 15, 2007 11:04 am Post subject:

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

That fuel filter in backwards syndrome ...
Maybe we should take a poll?

Mine was like that too, but there were so many other things wrong I'm not sure how much bad running-ness it contributed

My boost switch cuts off around 17 lbs or so . . . And that's what Haynes says is right. (I hooked it up to a bike pump and a multi meter.)
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1980 931 w/88K, decorating a field for 3 yrs.

924guy · Posted: Fri Nov 16, 2007 11:06 am Post subject:

hmmm... i wonder if theres a different rating for the series one and two boost pressure switch?? mine definitely cuts out at 25psi, and it wasnt a bike pump i was testing the limit with....

_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

25 lbs of boost is unthinkable ...
I think I was giggling like I was on helium even with a "mere" 17 (and it sounded sort of like a jet)

Here's what Haynes says: the switch should cut out at "approximately" 21 lbs. Then it should come back on anywhere between 15.6 and 20 lbs.

As for two ratings, who knows. Haynes lists the stock boost at 9-10 lbs but I was informed on this forum that the Yank version goes less, like 6-7 (which coincides roughly with what mine was putting out stock)

as for my seeing 17 at cut-out, I suppose 1) it's possible I wasn't reading the gauge very accurately and only saw around 17/18 on the gauge (gauge is off to the side) in a quick glance before avoiding a telephone pole or dog walker. and 2) the actual pressure might peak ahead of what the gauge can read. It's kind of hard to say what's going on when you're the only one in the car and you're trying to steer, shift, not get a ticket, not hit anything, and read a gauge during about 2 seconds of max boost . .

or, 3, my boost switch is a little premature
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1980 931 w/88K, decorating a field for 3 yrs.

jazz guy · Joined: 26 Nov 2002 Posts: 434 Location: Colorado

I have run higher than stock boost for a number of years. I know for sure that my overboost switch cuts the fuel before it gets to 25 psi. I've banged into the limit around 20 psi a number of times. I also see pressure spikes when I lift to shift (before the recirc. valve can activate) that cause the overboost switch to kick in and cut fuel.

On my car, I have found that boost much above 17 has diminishing returns. The turbo turns into a heat pump and the engine doesn't pull nearly as well as it did up to 17. I do have water/methanol injection on the car and while it stops detonation, it still doesn't make much more power above 17 psi. Taking into account the limitations of the kkk turbo and cis systems in our cars, I don't see how a 931 could live very long pushing even 20 lbs. boost on pump gas. Maybe my car is the exception, and isn't running optimally, but I would definitely have to see it to believe it.

Before I added water/meth injection, I would run 12 to 14 psi, depending on air temp, with no metallic crackling (bad) noises. W/ inj. 15 - 17. Your results may vary a little. Have fun.

Cheers, Brian

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

jazz guy--
thanks for that excellent information.
Not that I have any idea what water/meth injection is, but whatever . .
I'm running it at 12 for the moment. I have a couple of concerns-- mainly retaining decent gas mileage and two, not getting tickets. And, finally, not blowing up the engine that I just got running well.
Therefore . . . I think 12 will do me for the time being.
I figure, the car just flew through inspection, it's all legal, it goes like stink (more or less) so it'll be my d.d. until I absolutely have to go pick up a load of 2x4s or something ...
then I'll throw my F--d back on the road again
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1980 931 w/88K, decorating a field for 3 yrs.

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England

I think turbo removal is going to have to be the way foward as i have hit a dead end as to why this turbo is only making 3-4 psi boost . Im going to check it all throughly does anyone have any good tips for removal before i have a go at taking it off thanks .

924guy · Posted: Tue Nov 20, 2007 12:02 am Post subject:

have a good assortment of socket long and short extentions with the "wobble" ends, and a swivel for the exhaust flanges, as well as some open end metrics, particularly the larger sizes for the oil line banjo bolts.
soak everything with pb blaster for a few days, and dont forget the waste gate mounts and j pipe connections.
if your waste gate hasnt been out before, expect to need new studs, if your lucky, you wont need a machine shop to remove/repair the studs. rebuilding it while its out is a good idea, as the wg diaphram is probably on its last leg.
once the turbo is completely disconnected (the bracket mounts are a pita as well, but it can be done) itll need to be rotated just right to drop it out.
_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

Smoothie · Posted: Tue Nov 20, 2007 1:32 am Post subject: Re: 924 TURBO NO BOOST

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England

Smoothie · Posted: Wed Nov 21, 2007 12:56 am Post subject:

The Haynes often has you doing things the hard the way because they didn't have the time to find the easiest way (and in some cases they have you doing things just plain wrong because they didn't take the time to find the right way), so read it, but be aware there's often a better way..
Look at Bob Dodd's (Zuffen's) procedure for dealing with the valve under the title "Pop-off Valve, Removal and Installation" in the "4- Turbocharger" chapter of the "924 Technical Section" link above.
You should be able to check the valves' installation after removing just one end cap...
The valve (aka- "piston") is a cup shaped piece with a spring at its' opened end. Looking at it from the front, the opened end and spring should be located at the right side (spring at right, pushing the valve to the left)(there's also a spring guide to the right of the spring - not to be confused with the valve). If that's what you find, it's installed correctly. -And you should be looking elsewhere for the low-boost problem.
If you find the closed end of the valve at right and the spring and guide at the other side left of it, that would be wrong, and require removal of the valve, spring and guide to correct it.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England