Bret 944

Well, thanks for the results Jeff. But, you ran the car with the CV connected, right ? Did you try the other suggestion to block the CV line that goes to the wastegate and see if you can build up boost ? I think that's the only real way to eliminate the possibility of the CV being bad.

TurboTommy

I love danno's explanation; I've seen it before. Excellent.

A thing to note: the CV duty cycle is controlled by the KLR, which in turn is getting a signal from the TPS which tells the whole system the load and therefore it says "it's time to up the boost". If the TPS is not working properly you will get the classic 1.2 bar absolute max boost.
It's happened to me.

Rich Sandor

My 87 is only boosting to 1.2-1.4bar, and it's driving me nuts. I just put in another shimmed wastegate but it didn't make any difference. I think I'm going to try bypassing the CV and see if it makes any difference.

I'm learning so much from you all. You guys rock.

Especially special tool and Danno. Where else can you have someone offer to help fix something for free after being told he was being harsh, and have another guy explain how something works with elaborate diagrams.

This is the kinda stuff that makes rennlist rock. I gotta get my membership renewal to John and Jen asap.

Bret 944

Rich, Jeff, I figured out my only boosting to 1.2bar problem today !!! I bypassed the CV - Took off the hose that goes from the CV to the wastegate, and inserted a small tool i had laying around into the end of the hose, leaving nothing on the end of the CV. Knowing I didn't have overboost protection, I waited until I got in 3rd gear, and rolled onto the throttle. Once I saw it go to near the end of the factory boost gauge, I let off. THE DAMN CV HAS TO GO. Ordering boost controller as we speak...any suggestions ?

Danno

Rich! When did you pick up a second car??? I get busy and don't check in an all of a sudden you've cloned your car!

Yeah, simple test is to clamp shut the line going to the wastegate, personally I think it's easier and faster to just crawl under and disconnect it. Then gently do a couple of full-RPM runs, starting at about 50% throttle and increasing to 75% as RPMs build past 4000rpm, watch your boost-guage. Do another run starting at 60% throttle going to 80%, etc. At this point, you should be getting full-boost in the mid-range and if you gradually increase throttle with RPM, you'll be able to keep that boost all the way to redline.

If you're not getting full-boost, immediately jack up the car after the last run and feel the wastegate dump-pipe to see if it's warm. Even with the hose disconnected, exhaust-pressure in the upper-RPMs can still force the wastegate open, but it takes about 35-50psi in the crossover-pipe to do this depending upon how week the spring is and how much you've shimmed it.

BTW, there's a difference between static and dynamic (flowing) pressure. So I gotta hook up a second gauge in my crossover in the short elbow going to the wastegate because I suspect pressure there is different than in the main crossover itself.

Porsche-O-Phile

I did not get a chance to try blocking off or otherwise "pinching off" the wastegate line; I checked the J-boot first since I suspected some of the connections might've been loose and the sucker just crumbled apart in my hands - it's worthless. I placed an order for a new one today (that's another story, I'm a bit torqued at Zim's right now but suffice to say it's coming probably by Friday).

Once that's done, I'll try it and check for boost. If that doesn't work, I'll pinch the line and check for boost, if that works I can try to narrow it down with the TPS.

NZ951

Tracking number is PP489474266NZ went air mail you should have it in a week.

mroberts

Can someone point me to the hose that runs from the CV to the wastegate ? I'm suffering form loss of boost adn I'm trying ot work out if it's an electrical issue with the system in safe mode, or if I have a leak somewhere.

Thanks.

Rich Sandor

The CV to wastegate line should be on the nipple on the CV closest to the firewall.

I just disconnected mine and the car is developing full boost again.

mroberts

Doesn't that mean you are running completely uncontrolled boost ?

I was just outside playing aorund, and discovered that my CV doesn't switch when I drop 12V across it. According to the manual that's abad thing, and indicates it is shot. I whacked it with a screwdriver a couple of times, and was able to get it to switch, a coupel of time,s but that was it.

I'm thinking that's the root of all my current problems. Sorry for the hijack, but thanks for the thread, this has been enlightening.

Porsche-O-Phile

This is good info all!

NZ951 - you rock!

See my other thread for details but here's the summary:
- Got new J-boot
- Installed new J-boot
- Drove car
- STILL only got 1.2 bar of boost
- Drove home
- Disconnected wastegate line from CV
- Plugged wastegate line
- Drove car
- STILL only got 1.2 bar of boost
- Drove home
- Put hand vaccum pump on wastegate line
- Put 25psi of vaccum into wastegate line to force wastegate valve shut
- Drove car
- STILL only got 1.2 bar of boost
- Drove home
- Parked car
- Banged head on wall until bloody
- Went upstairs
- Bandaged forehead
- Drank beer
- Wrote this post.

or something like that. . . more or less. . .

NZ951

Just another Saturday night then...