Sevenman's TVR (was SAAB) Blog

February 25, 2006

New Brakes Arrived

Filed under: Saab — Administrator @ 10:35 am

2 big parcels arrived from Elkparts containing front and rear disks and pads.
Fitting is still booked for Thursday, but here are some pics before they go on the car.

February 22, 2006

Brakes ordered

Filed under: Saab — Administrator @ 8:34 am

In preparation for the trackday in May I have been looking at replacing my brakes which have been well-cooked in the past.

Changing for bigger disks/calipers is expensive and won’t fit behind standard wheels. Since I want to keep the car looking standard this isn’t an option.

Following discussion with Elkparts and reading posts on Saabscene I settled on Brembo disks and EBC Redstuff pads, which I have ordered from Elkparts.

I am currently running Brembo disks, but since the 2004 Anglesey trackday they have the effect of vibrating under braking when very hot. However many others have reported good behaviour, and I suspect that the lack of bedding-in time before the trackday was a factor.

These should be fitted next Thursday and so have 3 months before going on the track.

The EBC Redstuff pads have also had good reviews, so I will be interested to compare them with the Ferodo DS2500 pads I am currently running. The DS2500 are about £20 more/set, make lots of dust and have a tendancy to squeal under light braking. They have never faded though.

February 19, 2006

New Dump Valve

Filed under: Saab — Administrator @ 8:28 am

I fitted my new Forge recirculating dump valve today.

I advise fitting when the engine is warm. When cold I couldn’t remove the old valve – the jubilee clips are unnecessary, it really isn;t going anyywhere.

When warm after a drive the valve came out with the use of a fair bit of force.

Fitting the new valve takes a couple of minutes and it looks nice and shiny.

Went for a short drive – the valve does what it should, making a slightly sharper noise than before – could be releasing boost faster than thr OE valve due to the larger piston?

February 9, 2006

Behaving properly

Filed under: Saab — Administrator @ 2:59 pm

Received a package from Elkparts today.

Immediately fitted the replacement APC valve and took the car for a drive on some interesting Worcestershire roads. The car now performs properly with lots of controlled boost :)

I also have a Forge recirculating dump valve to fit and a DIN mount for 3 gauges. I have a boost gauge ready to go in but need two others to fill it. I think oil pressure and water temperature might be useful. My 9000 has the unresponsive temperature gauge which never gets hot. Would be interesting to have a more responsive gauge. Equally there is an oil-pressure warning light, but it might be nice to know the extra info.
However this may just give me more things to worry about.

I added my name to the 2006 Saabscene Trackday being held in May at Croft (see Saabscene for details). I need to replace my brakes for this since the current set of disks have suffered from previous trackdays.

February 6, 2006

APC Function

Filed under: Saab — Administrator @ 2:34 pm

Having done a little research I think I now understand the working of the wastegate and APC.

Wastegates allow exhaust gas to bypass the turbo. Without a wastegate opening a positive feedback loop is formed which should be able to destroy an engine.

Wastegates are opened by an actuator. This is connected by some vacuum hose to the compressor side of the turbo. When the compressor reaches a certain pressure the wastegate opens. The wastegates in Saabs are set at about 0.5 bar and this is known as base boost.

Saab has a more sophisticated system using a number of sensors and the APC solenoid valve to allow greater boost pressures than this base boost, and to vary them according to a number of factors such a fuel quality.

The APC valve has 3 pressure connectors, one to the compressor (C), one to the wastegate (W) and one to atmosphere (R). It also has 3 electrical pins connected to the ECU. These operate an induction loop which moves a piston inside the valve.

If there is no electrical signal, air is allowed to flow freely from C to R, effectivly giving base boost performance.

I believe that after some period of normal operation my valve jammed here for a while.

During Friday’s testing, after I disconnected and reconnected the valve it jammed in such a position that the C port is sealed and now air moves freely from W to R. I have tested this by blowing through the various connectors.

This is a dangerous setting, giving me silly levels of boost but at great risk to the car, as I discovered.

I have now ordered a replacement and am returning the failed valve. I also decided that a new Forge dump valve and a 3 gauge din mount would be a good idea…

February 4, 2006

Progress

Filed under: Saab — Administrator @ 9:11 am

Recieved an e-mail from Elkparts (those guys were still working at 6:45pm on a Fri night).

There are a couple of tests for a working APC valve.

1) The resistance from the centre pin to the ones either side should be 2-3 Ohms.

I checked this and it was 2.5 on each side. Same for my old valve.

2) You should be able to blow from the C to W connector but not from W to R.

This didn’t work. C to W is sealed and W to R flows freely.

I believe this means the piston is jammed. I don’t understand the workings of this valve, but the effect doesn’t seem to be good. I will therefore put my old valve (which doesn’t hold much boost) back on until a replacement arrives.

February 3, 2006

Hopefully Solution

Filed under: Saab — Administrator @ 5:39 pm

Another chat with John at WMSS leads me to believe that the replacement APC solenoid may be faulty and causing the problems.

As the wastegate functions for the base boost setting, the APC solenoid seems the most likely solution – I can’t think of anything else, but I don’t know all the intricacies of the turbocharged Saab engine.

I gave Elkparts a call (still there at 17:20 on a Friday) and discussed the symptons with them.
They were very helpful and are going to look into the problem and send me another valve to test.

For now I will leave the car set to base boost (which still seems fairly brisk), and update this site when some progress is made.

Scared Myself….

Filed under: Saab — Administrator @ 2:58 pm

Having left the battery disconnected for 2 days to reset the ECU I had Friday afternoon off to fix the boost issues.

So I reconnected the battery and went out for a drive – car still only boosted to the start of the end of the broken yellow/red section.

To check that the car could actually hold boost I disconnected the wastegate pipe for the APC solenoid valve. I gave the car a couple of short bursts and the boost gauge went merrily past the red.

Having done that I reconnected the pipe tothe APC and drove on – only to find I now had lots of boost – needle past horizontal boost.

I worried that maybe the wastegate had stuck closed. I went home and swapped the APC valve for my old valve which wasn’t holding boost. True to form it only boosted to the end of the yellow.

I then replaced it with my new valve and carried on. It was still producing worrying amounts of boost.

I gave it a run through the rev-range in 2nd gear. This culminated in a loud bang, smoke out the back and the engine dying.

I coasted to a halt outside someones house and looked under the bonnet to see if my engine was still there. Thankfully it was and no bits were missing. I gave it a few minutes, and it started fine.

Drove home gently and gave John at WMSS a call. He suggested sticking wastegate or faulty APC valve. A suggestion was made to unplug the APC electrical connector and that should produce base boost. I did this, and the car boosted to the end of the yellow (still felt fairly quick).

From these problems the likely explanation seems to be a faulty APC solenoid valve – I am not sure what else could cause the symptons.

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