930: where to connect boost gauge?

obrut · 08-18-2002, 09:33 PM

Where is the best place to connect a VDO boost gauge in a 930?

My mech tee'd it into the brake booster and it only showed 0.5 bar flat out in 2nd gear. The standard (ie. in the speedo) qauge shows 0.8 at this speed/gear/throttle.

We are thinking of running a line all the way back to the intercooler. Any BTDT's?

Cheers- Ryan

WydRyd · 09:48 PM

Hi Ryan,

I bought the VDO/NHS Boost Gauge (clock replacer) & Install kit from PelicanParts. It's the kit that also taps into the brake booster.

I read approx the same peak boost as my Apexi AVC-R Boost controller (0.7-0.75bar), however sometimes, I find the NHS Gauge indicates boost spikes also, cause it sometimes shows closer to 0.8-0.85bar.

They aren't 100% accurate, but better than nothing I guess.

obrut · 08-18-2002, 09:51 PM

Thanks Merv - was the kit anything but a tee piece and some line? (I ask because I think my mech has basically done exactly that).

I thought the problem might be due to measuring boost pre (ie brake booster) vs. post (ie intercooler) throttle???

I'll let you know what happens when we run the line back to the i/c.

hobieboy · 08-19-2002, 05:53 AM

I am contemplating exact same thing on my 87, and am inclined to connect it to the intercooler. Any suggestions on where to run the hose? Through the "rear" firewall?

I think a simple tee would work?

thx...
Patrick.

obrut · 08-19-2002, 11:36 PM

Thanks for the replies guys - here are the results.

Connected gauge directly to the i/cooler near where the factory gauge elec sensor is. Ran the car through the revs in 2nd gear with full throttle and it showed 0.8bar with a spike to just over 1bar as the throttle closed during gear change to 3rd. This was mirrored by the factory gauge. When it was tee'd to the brake booster it showed a max of 0.5bar (spiked to 0.6) under the same test conditions.

Conclusion - I think connecting to the i/cooler is the preferred option (and I now know for sure I have a 0.8bar spring).

Re: the spikes - what do you think of blow off valves (ignoring the ricey psst noise) ?

WydRyd · 08-19-2002, 11:43 PM

Good research there Ryan, thanks for sharing.

If you want to increase the life of your turbo, then definately fit a BOV on. Whether you have it fit between the turbo -> IC or IC-> Intake, it really doesn't matter all that much, however, I chose to have it installed between the IC and Intake.

You don't have to have that Pssshhhhht sound if you get a BOV with an air collector device on it, allowing you to vent the air wherever you want. Typically it's vented back into the intake.

Hope that helps.

dean · 08-20-2002, 04:33 AM

I hooked mine up to the stock turbine outlet location. 75 930 There are 3 locations for the hookup, not including the brake booster. Before the intercooler, after the intercooler and after the throttle. You can measure the pressure drop in the sys. by the different locations.

I don't know what car you have but you should have at least a compressor bypass valve. If you want to put a BOV in and if you have the CIS I think you need to dump the BOV back into the intake or the metering will be messed up. I might be wrong about that. I put a 993 CBV in mine and under certain cond. I get the pssst sound and I love it. It remindes me of when I used to hear the 935s at Lime Rock. Ah mamorys ;-)