paul r

My wastegate must be weak I get 0.7bar initially, but this soon falls down to a disappointing 0.3bar as i approach the redline. My car is a standard '86 951. Since I'm going to have to pay for a refurbished wastegate anyway I thought why not get a shimmed (preloaded) refurbed unit. I guess there's little difference in cost.
My questions are who can sell me one?
How much cost?
How much boost?
Do I need to also use a bleed valve on the air pipe to the wastegate?

si

youre spring is indeed weak.
My 1991 951 didnt respond too well to some chips (ie boost didnt really increase) so I shimmed the wastegate. There is some advice in the 944 garage website. However briefly jack the car up and locate the wastegate, then remove. this essentially means removing the 2 sets of 4 13mm bolts which go into the pipework entering the wastegate, also undoing the short sections of the next join in this pipe work (10mm bolts) and then the boost hose which connects to the wastegate.

Once removed undo the 3 allen bolts and insert some washers between the 2 halves of the wastegate, i shimmed mine by approx 4mm, yours probaly needs 7-8mm!!
You DONT need to make up an accurate shim design like that shown in the 944 gge, since there is no air leak between the 2 halfs of the wastegate. Then just replace the wastegate.
You do need some good quality well fitting sockets, a UJ and some long extensions, since the bolts will be tight and rusted (from the heat). With good quality stuff you wont need to grind down the socket as suggessted in the "gge".

Anyway good luck, any probs -post.
ps 1 bar boost is all the headgasket can take

si
91 951s

Brent 89 - GT

Instead of trying to help a bad wastegate, why not replace it altogether? I don't know about the UK, but here in the US I am going to get mine from Paragon Products. The wastegate is $400 and the manual boost controller is $60. I suspect you need a good boost gauge at this point too. Mine boosts much better than yours but I too can watch the boost fall.

txhedg

I agree on the new, upgraded wastegate. I replaced mine a year ago with a used, stock WG, and now wish I had spent a few hundred$ more and gone with the lindsey WG and boost controller. I think this is the one Paragon sells, also. MUCH more performance and adjustability. Plus a bolt-in install with no mods required.

aka 951

The LR wastegate is awesome. Easy install (less than an hour) and works perfectly.

Erick

paul r

I had thought about the Lindsey wastegate. But decided against it because it holds the same boost pressure right up to the redline.
I know the above sounds ideal, but I have been told by a UK company who race prepares 951's that my 220bhp smaller turbo will be spinning too fast if full boost is achieved at high rpms. This will shorten it's life.
Can any of you comment on shortened life of my small turbo providing say 0.9bar boost at 5500rpm.

paul r

I like to check out 944 garage, anyone know the link?

Steve Cooper

Porsche 944 Garage

aka 951

you're right - you have to get a bigger turbo to run boost safely at high rpm.

Erick

toddk911

What is the difference in shimming the wastgate and adding an LBE?

Danno

There are two forces that work on the wastegate valve to open it. One is the pressure-operated diaphram that is controlled by the boost-controller (LBE) to push open the valve. The second force is the exhaust pressure. Therefore, it's the sum of these two forces that opens the wastegate.

At low RPM/low boost-pressures/low exhaust-pressure, the diaphram is not open and the spring holds the valve closed. In the mid-range when max-boost is hit, the LBE will allow pressure through to open the diaphram and regulate boost. In the high-RPM/full-throttle/high exhaust-pressure range, the exhaust pressure adds additional pressure to the valve and a weak spring can allow the wastegate to open prematurely, even with zero pressure from the boost-controller. This high-RPM boost drop is pretty typical of stock wastegates and manual controllers.

This is where electronic boost-controllers come in. At high-RPM, they will actually learn NOT to send any pressure to the wastegate diaphram at all, even IF the desired boost pressure has been hit, because it knows the wastegate is ready to leak.

So a good minimal upgrade would be to both shim the wastegate AND get an LBE. A step up would be an electronic boost controller. Finally the ultimate upgrade would be an electronic controller with an aftermarket wastegate. IMO, manual-controllers with aftermarket wastegates are silly.

See here for a discussion on wastegates and shimming: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=000541" target="_blank">Topic: Dual Port Wastegate Question </a>