Only 1.4 bar boost

arnebret · 04-30-2002, 09:00 AM

Hmm, under full throttle my car will only build up .4 bar of boost. While .8 bar is normal. Somehow the computer is holding the boost back because he is missing input from sensors or something. Anybody? I did the 'blink-code' test, but nothing came out.

Scott R · Scott R's Garage

Check the boost to KLR fittings on the manifold. They are on the back of the manifold on the passenger side. There is a small banjo bolt there with two vacuum lines check them both. Then ckeck that the wastegate is attached securly to the cycling valve and that the KLR vacuum line is attached and not leaking. If all that looks good then go after your wastegate, it might be shot like mine was.

arnebret · 04-30-2002, 11:38 AM

I just did another test run and the pressure only came up to 1.2 bar. I noticed that my TPS connection is not too good. Because, at idle, when i touch the connection of the tps and fool around with it a bit the idle speed will rise up to 1200rpm. It seems like the signal is bad. I'm thinking of putting a new TPS on, they are pretty nasty buggers on these cars and tend to go bad when they are still on for about 15 years

As i said, i did the blink test, wich tests all things related to KLR, boost, wastegate and the complete control of it. It comes out with nothing at all. I'm sure it works, because when i detach the TPS it will do a 4-1 blink, indicating the TPS is not giving a signal anymore. The factory manual says that if there is no blink code one may expect that all things controlling boost are fine. But it seems they aren't...

porscheboi928s/c944t/n · 05-01-2002, 06:35 AM

when i touch the connection of the tps and fool around with it a bit the idle speed will rise up to 1200rpm.
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it's only an ON and OFF switch...not variable......well atleast mine is...

porscheboi928s/c944t/n · 05-01-2002, 06:36 AM

And another problem is on the wastegate...the spring is weak.....

arnebret · 05-03-2002, 07:43 AM

Well, the TPS'es on 1988 Turbo's have an all-range sensor. The KLR gets this reading and compares it with other readings it's getting and allowing (or not) a certain amount of boost.

But i think i found my problem. The controller hose (from timing valve to wastegate) seem to have lost it's hose clamp at the wategate side... now this means that at about 1.4-1.5 bars the wastegate isn't opening any further, thus not allowing more exhaust pressure in the turbo resulting in lower intake pressure.

Any ideas on this... i'm pretty sure all other things concerning boost are fine.

Scott R · Scott R's Garage

I had the same problem and just replaced the entire hose. When I purchased my new wastegate and manual boost controller from Lindsey Racing it came with several feet of Blue vacuum hose so I replaced it with some of that.

arnebret · 05-03-2002, 11:47 AM

I just bought a new Porsche genuine... (AHUM) hose for... 10 bucks. I know, those guys at Porsche know how to turn a bit of ordinary bent plastic hose into gold

arnebret · 05-03-2002, 11:51 AM

Just another question... how the HELL do i get that hose of at the timing valve side. It seems to be completly stuck... and do i need to unbolt the hose at the wastegate as it seems this side is pretty stuck as well..

arnebret · 05-04-2002, 07:14 AM

Damn it! I just checked and replaced the connection at the timing valve and wastegate, but it doesn't matter. I'm getting 1.5 bar now. But it seems my 0-60mph time is about 6 seconds. Factory specs say 6.3 secs. I have no HP upgrades whatever, so it seems all is ok, might the boostgauge be broke or something...

Scott R · Scott R's Garage

If your using the factory boost gauge then yes! They are know to be off. If you want to check for accuracy go and get a Autometer or VDO gauge to verify your dash gauge.

arnebret · 05-04-2002, 08:10 AM

Well, i'm still using the one on the regular dashboard. I just did a timed 0-60 with my brother and a full fuel tank. My brother is about 70 kilos, i'm about 80 kilos and i have about 60 liters of fuel in tank. So, 70+80+60=210kilos+1320kilos=1540kilos netto weight. 1540kilos is about 3400 pounds all-in.
We came up to 6.92 secs and 7.05 secs in two runs. So take 7 seconds as 0-60. I know the factory spec is 6.3, but this is with one driver (will probably shift better than i) and not too many fuel in the tank.
Any thoughts on the 0-60 time?

arnebret · 05-04-2002, 08:15 AM

Where will a second boost gauge intercept the pressure? In other words: how will a second gauge be connected to the turbo-system to get a good reading?