strudel

I recently bought a '79 930 (DP935), Andial twin plug, etc., The adjustable boost **** doesn't seem to work. I'm trying to turn the boost down. I've turned it in both directions until it stops. The gauge pegs at 1.8-2.0 bar, great acceleration. I've been using 1/3-1/2 trottle and backing off as soon as max boost is achieved. Andial suggested I run it at 1.0 -1.2 for longevity. Any idea how to adjust this, or what to check for.
Thanks
Harold

Sameer

Harold,
With good octane fuel, adequate cooling(bigger intercooler, oil cooler), enough fuel, I would'nt take it more than 1.1 bar of boost. Andial also told me to keep it at or below 1.1 bar. Most of us here run 1 bar of boost with slight fluctuations. I'd keep off the throttle till you have the problem rectified. It only takes a few seconds for detonation to occur.

PorschePhD

1.2 for longevity?? Hmm, I would suggest otherwise. 1.0 is it on a unmodified fuel head, unless you are running a stock turbo. Then the problem becomes maintaining that 1.1 bar. Which a 3LDZ will not. I would loose the "dial a death" and put a 1 bar spring in it, set the CO and call it a day.

strudel

"unmodified fuel head" if you mean fuel distributor, then it's stock along with the injectors. Andial confirmed they built the motor but can't confirm all that was done without the original owners name. The did confirm Group B cams. It also has a 12 plug distributor, twin stock cd boxes, twin plug heads, fuel enrichment box (adjustable), DP muffler, andial intercooler. I'm assuming the turbo charger is not stock, but not sure where to check.
What should be done to the fuel head? Also, where can I send the boost gauge to get it checked? I'll plug in the LM1 and check the a/f this weekend.
Thanks,
Harold
'79 930 (DP935)
'74 RSR replica race car w/3.4 twin plug
'73 S coupe
'68 VW Crewcab w/3.2 & 5 sp.

Sameer

Harold,
Stephen at Imagine Auto does the fuel head mod which flows 15-22% more fuel throughout the rev range. You can still use the Andial FEC along with that but I doubt you will need it. With your twinplug, good fuel octane and adequate cooling with fuel, I'd take it to 1.1 max but like Stephen mentioned, get rid of the boost **** and just put in a 1 bar spring and your all set to go.

pete77930

but 1.2 bar is soooo much fun.

Sameer

pete,
fun for a short time only, sad but true.

pete77930

more boost+ more fuel+ fire ringed heads = fairly safe...and if it blows, build it bigger and stronger and enjoy it untill it blows again. lol, go big or go home. I live by that one a little too much.haha

PorschePhD

Ah yes a lot of fun until it goes BOOM

pete77930

also if you were hitting way over 1 bar wouldnt the factory cut off switch kill the motor? I know I had to install an after market cutoff switch to allow the motor to run on 1.2 and overrun to 1.3 or so before it cut in. your boost guage might not be accurate, or some one reversed the vaccum lines running to your "dial-a-boost". those would be the first to things I'd check. maybe dissconnect the vaccum lines off the wastegate all together and see what boost pressure you get. if the vaccum line from the intercooler is plugged into the top side of the wastegate it wont allow the wastegate to open and you get crazy boost. hope this helps.

pete77930

I know, it went BOOM once already...we're on rebuild number 2.

I was planning on upgrading to EFI this past summer but ended up buying another sportbike. I have a funny feeling that once EFI is in place it'll go boom again. My mechanic tells me he's starting to see a pattern with me and advised me to drop a N/A motor in the car...sounds like the smart choice, just not the fun one.

PorschePhD

Most people unhook and ground the switch.

strudel

I was wondering if the boost gauge isn't reading right. When I turned the boost **** all the way in one direction the gauge read 1.3 bar and the next time read 1.8. Any recommendations as to who can check the gauge. It replaced the clock and has a tattle tell needle. I would like to retain the boost **** for the original look. I'm fine to run the car at 1.0 bar as I would like it to last. I will probably track the car once or twice a year to be able to wind it out in a safe enviorment, but it will stay a street car. We have a 74RSR (clone) race car with a 3.4 twin plug, carburerated motor w/appox. 300-320 h.p. so I have no desire to go beat the 930.

A930Rocket

What kind of wastegate and spring do you have? Could it be that it's too high and not allowing you to dial it down? Try a .8 spring.

nathanUK '81 930 G50

It sounds like the wastegate never opens to me.
Try connecting the tube from the intercooler to the lower connection on the wastegate. Let the top connection on the wastegate vent to the atmosphere.
See what boost you get after this.