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lews930 02-09-2007 04:24 PM

30 years old and she is HOT
Hello all. I've waited a very long time to post these pics but I have problems with her.

Yes it is a 76. No that is not the original tail, note the garretson intercooler. I installed those two little goodies after replacing the warn out 3ldz with a K27 with 1 bar spring and upgrading to a GHL exhaust. The internals are 3.0 and just rebuilt (maybe 30 miles). the problem I have is over boost. I am hitting 1.2 bar almost immediately. I tested this with a manual gauge sitting on my lap. I was told to install the .8 bar spring but I dont think thatg will sove my problem. I think the waste gate will still open before I hit wide open throttle.

If this is enough info am I looking at a larger exhaust? if my thinking is correct, the GHL stuff is too small to allow the motor to breathe thereby creating too much boost.? The car was much faster before I had the motor rebuilt along with the rst of the car. Plus I was able to hold the pedal down as long as there was straight road ahead of me.

Thanks for any and all help


930turbo 02-09-2007 05:09 PM

It's good to see you got it on the road. I have the guards red '77 930 that was at the body shop the same time yours was there. I have the same engine build but without the headers. It's fair to mention here yours is an SRD example. Nice car. I doubt the exhaust has anything to do with the over-boost, it's probably waste gate related. It might not have full range of opening. I tested mine on the bench prior to installation on the car after installing the 1 bar spring. I applied 15 PSI and it opened up. Check the vent side for dirt dobbers.

Craig 930 RS 02-09-2007 10:02 PM

Stock wastegate before and after?

NathanUK 02-10-2007 06:01 AM

I'm thinking something is not hooked up right.

WERK I 02-10-2007 08:27 AM

This is a known problem with the GHL's. The problem is the design of the wastegate circuit. The diameter of the pipe from the flange to the wastegate is too small. The pipe can not bleed off sufficient gases to trim the boost levels. You can lower the spring setting on the wastegate to prevent the overshoot condition, but keep in mind the wastegate valve will start creeping open sooner too. I think the best solution is to use the Tial wastegate with a modified wastegate pipe. The Tial is compact enough that you can mount it closer to the turbo flange.
Also, are you using the factory boost gauge? These are not as accurate as the models that go into the clock housing....larger sweep area.

Craig 930 RS 02-10-2007 09:39 AM

Data point:

With stock WG in perfectly functioning condition - my B&Bs measured exactly .8 bar with .8 bar spring - using the HUGE factory test boost gauge.

With the Tial + .8 spring and the same headers - .15 OVER.
Be aware.

Lukesportsman 02-10-2007 05:08 PM


What size Tial?

Lukesportsman 02-10-2007 05:13 PM

Sorry, how rude of me........Lewis, beautiful ride and no one should blame you for improving a 76'.

WERK I 02-11-2007 07:00 AM


Originally posted by Lukesportsman

What size Tial?

Most of us are using 46mm.
It's a plug-n-play fit.

Lukesportsman 02-11-2007 09:00 AM

I realize that most are running a 46, but since we are comparing it to stock WG I thought it best to clarify. Just trying to narrow down variables on why the Tial wasn't controlling things as accurately. Craig has at least eliminated the header issue in his example. The initial thread starter doesn't have this convenience, but hopefully we give him some ideas if nothing else.

lews930 02-11-2007 03:34 PM

I'm no turbo expert but a .8 bar spring would only allow the waste gate to open faster thereby eliminating over boost. I know that overboost is BAD but I can only hold the throttle for 2 seconds. that is no fun. How do I make it so I can hold the pedal to floor like the days of old? I dont know what boost I was running then but WOW was she fast, fater then than now because I can only hold the pedal for 2 seconds.

I used the huge mechanical test gauge and had it on my lap while driving. Short of buying and trying which I'm not into as I've spent way TOO much on this car, I need an answer. I was told after I bought the GHL system about it's problem but it is a very nice system. I hate to sound pushy but Ive run into this problem before with a RX7 turbo. Buy this do that and so on.

thanks for all the help


lews930 02-11-2007 03:36 PM

930 turbo, what does SRD example mean? I have no idea


lews930 02-11-2007 03:43 PM

After going back and thoroughly reading the posts I have more info. prior to running the car My neighbor who is a Porsche mechanic but no turbo expert rebuilt the stock waste gate with a diapragm kit. he tested the wg prior to installing it on the car and after installing it. he said it was fine. 930 turbo, where are you located? close enough for a test ride to see my problem in action?


930turbo 02-11-2007 04:37 PM

SRD - Sun Roof Delete. Most turbos come with this option.

930turbo 02-11-2007 04:58 PM

Lew, I recently relocated to Sorrento - a few miles north of Orlando near Mt. Dora. I was located just down the road from Kieth's when our cars were in for paint. I'm all for saving a few bucks, I still doubt the exhaust is the culpret. GHL would have addressed this by now if that were the case. Also, your engine - and mine - are 10% smaller in displacement than what that system was designed for. If someone experienced insufficient bypass volume, chances are it was a monster motor consuming huge quantities of air. That's not likely on a stock 3.0. One other thing to consider, there is a 1.2 bar spring out there - is it possible you received a mis-pick when ordered? Does it level off right at 1.2? Has your factory over-boost fuel pump kill been disabled? It activates at approximately 1.0 -1.1. I had to disable mine because it would shut the pumps off momentarily @ full boost which created a very unsettling kaboom when the driveline goes slack. I have a fuel delivery problem that I am currently battling, if I had another like example to test, I'd learn alot more about my car. I'm not opposed to loaning you my wastegate for a quick test to at least identify or eliminate it as a possibility on your car. Maybe we could plan a test & tune day somewhere convenient for both of us. I'm reluctant to begin replacing fuel pumps without knowing for sure which one is bad ( save a few bucks) I just need to make some system pressure checks on a similar car. I have the proper tools. Tracy

dewolf 02-11-2007 06:00 PM

Mine did this a while ago after I'd rebuilt the wastegate. It was fine for a while then started overboosting and cutting out. I pulled the wastegate to find that the diaphragm had dislodged from it's seat. It was an easy fix.

mb911 02-11-2007 07:12 PM


Originally posted by Craig911
Data point:

With stock WG in perfectly functioning condition - my B&Bs measured exactly .8 bar with .8 bar spring - using the HUGE factory test boost gauge.

With the Tial + .8 spring and the same headers - .15 OVER.
Be aware.

Now take this with a grain of salt as I am a dealer for Tial but my 46mm is perfect dead on with my hand held digital boost gauge..

luke if you need one let me know

911boost 02-11-2007 07:15 PM

This thread is interesting, as my 92 3.3 turbo is doing this exact same thing. When I get on the gas easily, it is fine, but when I stomp on it, the overboost kicks in and my teeth just about impact the steering wheel. I am going to order a .8 bar spring for my Tial though, as I suspect that I have a 1.2 bar spring in there since my car has a ton of other mods, and the overboost sensor was grounded out when I bought the car.


Craig 930 RS 02-11-2007 07:20 PM

*B&B* headers plus Tial nearly always equals more boost than desired -

mb911 02-11-2007 07:21 PM

must be waste gate piping size then?

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