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kye · Posted: Sun Aug 29, 2004 7:26 pm Post subject: boost gauge plumbing preferences?

well, i've finally managed to get the time, weather and materials to get my new boost gauge installed in the car, and took it for a rather fun test drive..

but while plumbing it in I was faced with the question of pre or post throttle.
I am aware of what the issues are (the gauge is boost only, so it doesn't need to be post throttle) but the rest of it seems to come down to what you want to measure.
as far as my understanding of it goes, it seems that if you measure pre-throttle you're measuring the output of the turbo which is available for the car should you open the throttle to let it get some, and if you measure post-throttle you're measuring the boost that you're allowing the engine to have, or what it's currently using to make power.

I plumbed it in post throttle (because that's where the little pipes were that I had parts for) and during the test drive it only ever registered boost when I had my foot almost all the way to the floor.. as soon as I backed off to about 2/3rds it would just drop to nothing, which I assume means the engine would no longer be getting boost.

my question is, which thing is more useful to measure?
i'd lean towards knowing what the turbo is prepared to give, because that way you'll know when you've got the extra juice sitting there ready for you to use, rather than it just telling you that you're actually using it (which I can tell because I am pressed back into my seat when using it!)

where do you guys have it plumbed in?

(and if anyone wants a factory clock that doesn't keep time, just let me know!)
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dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

Kye,

Mine is a boost/vacuum guage so I connected it to a manifold (post throttleplate) line.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

Paul · Posted: Sun Aug 29, 2004 11:56 pm Post subject:

An easy place to connect it is the over boost switch. Just pickup a 1/8" NPT T at your hardware store.

Turbos only make boost when the throttle is open. At full throttle you should see boost start to build around 2800 and be at max (7 psi in a US car) by 5500 rpms.

mr. dude · Joined: 14 Feb 2008 Posts: 111 Location: Michigan

Hey guys, I'm reviving an old thread here. The reason being is that I have the same question as Kye. I'm am planning on hooking up a boost gauge and I think I am going to do what Paul suggested. Does this sound like a good idea to go from the overboost switch? I just want to read boost only not vacuum pressure.

Thanks,
Jeremy
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1986 Porsche 944

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

This is where the boost gauge was plumbed in on my UWB project when I picked it up. Seemed to work pretty well, and doesn't require any modification to the car.
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erstwhile owner of just about every 924 variant ever made

Cedric · Joined: 27 Aug 2004 Posts: 2829 Location: Sweden

Mine is connected vi a T- connector where the blue hose is, closest in the picture. (I didnt mount the blue stuff, dont blame me for the color

)
But i will change it, by putting a T connector on the line wich goes to the transistor box and take the boost/vac that way instead.

Heres a tip on how to make something useful of that ribbed speaker center console thing.

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1980 924 Turbo
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Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I drilled and tapped my upper charge tube for the fitting that came with the VDO boost gauge kit (boost only, not vacuum/boost).

I like Paul's suggestion as well, though. You can actually buy an adapter and barb fitting for that location from Porsche (parts 29, 30 & 31).

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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

mr. dude · Joined: 14 Feb 2008 Posts: 111 Location: Michigan

Thanks guys! Awesome, I really like this option as well due to not having to splice in anywhere.

Rasta, thanks for giving me the info on that fitting.

Cedric, Nice looking console gauge panel.
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1986 Porsche 944

Buwani 931 · Joined: 31 May 2004 Posts: 308 Location: Napa California

This was mine years ago. I have since moved it as I now have a vacuum-boost combo gauge.

I also cleaned everything up and replaced that crappy looking hose.

Shawn
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1980 931
That's thirty minutes away. I'll be there in ten.

emoore924 · Joined: 13 Apr 2004 Posts: 2822

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

vexed73 · Joined: 05 Oct 2007 Posts: 187 Location: EASTERN, nc.

Splineless · Joined: 01 Apr 2008 Posts: 86 Location: New England

I just placed a 5'' tach in the opening....I was embarrassed - I'm too old for that kinda thing. Sold it on CL.

Nav. system would work nicely.

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

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Hehe, no nitrous for me, thank you

But I can think of plenty of things to put in there. On my 951, I have a two-gauge A-pillar pod, which I plan to fill with a boost gauge and volt-meter. But I also want to install an oil temp switch-and-gauge, but have no place to put it (don't want to delete the A/C). And, when I get around to putting in a wideband O2 setup, an A/F gauge would be nice too. So, plenty of things could go there

On the UWB, I'm prob'ly going to go with a lightweight f/g racing dash. Haven't decided yet what to do about gauges ... re-install period correct VDO gauges, or go all-out race with new instrumentation...still up in the air.
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erstwhile owner of just about every 924 variant ever made