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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Originally Posted by cole930 View Post

I am excited to see the progress and adjust-ability the DWUR affords us. I feel
it is not necessarily the total answer for making a CIS well work on a Moded 930
but is defiantly a usefully tool that gets us closer.
I have an 80 930 that I've owned for 20 years or so. I disassembled it for
paint and am now putting her back together. I'm updating the bodywork to
replicate the 964 Turbo S LeMans GT, old school Group 5 Tail and all.
Engine wise I've done most of the popular mods and I am concentrating on
optimizing what's there to create a good reliable street car that is as fast as
it can be with the mods it has without being a hand grenade. I've tried to add
the correct mods and equipment to avoid detonation. I have the 3.3 euro motor
with SC cams, a little head work around the valves, Koklen IC, 934 short track
headers, Factory K28 11/11, 964 BOV setup, moded CIS, greedy boost controller,
MSD 6Al, MSD Boost Timer, onboard LM1 wideband logging a/fr, rpm, map, and
a short track 4 speed. DWUR is coming.
I wanted to pick your brain on the BOV set up. When I changed to the
964 BOV is saw a significant difference in throttle response and am planning to
try to improve on it even more. The 934 K28 11/11 has a left side hot housing
and I will be relocating the CIS to the right rear of the engine compartment
like the 934's were. My thought is there is advantage to the shorter intake
plumbing to the turbo on the 934 set up. I plan on putting a Synchronic BOV
on the 964 elbo and dump it back into the intake. The Bov will be within 2 ft.
of the Turbo inlet. You mentioned gaining some low end throttle response
by manipulating he BOV. Im interested in you ideas and opinions on this.

Wow, what a car.

I do not know the BOV you note. Dose it have a sliding piston design with a larger piston on the top faceing the vac line? If so and the upper piston has several times the surface area as the botom piston you could copy what I did.

I sent my Compresor Bypass Valve (CBV) up so it would stay open most of the time keeping the turbo spinning faster than it normaly would. When I say most of the time I mean with at idle and cruse. Then it would close when I wanted to accelerate.

I fliped the orintation so the pressure from the turbo was trying to push the small piston of the valve open and the vacunum from the intake maniflod after the throtle body and before the intake valve would pull the big piston with manfold vacunm at idle/cruse.

It has to have a larger piston in the upper chamber so when you open the throtle to accelerabe the vacunm goes away and boost pressure will start to replace it. It is the boost pressure and the adjustable spring above the large piston that closes the CBV.

I used a hand vac pump to set the adjusable spring in the CBV at different levels to efect how fast it operated. I liked my turbo to get just a little sping befor my valve closed.

As cruse I woud get instant .5 bar boost With sport shifts I did not lose any boost on my .7bar max factory gage.

This with a stragegy I came up with to quickly lower my CP upon acceleration to motivage the metering plate to get moving totaly woke up my car off the line and from cruse.

Hope this make sense.
Old 03-06-2009, 12:33 PM
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