At Star (similar readings to Powerstation - about 20bhp lower than PE) today I got 257 bhp 257lb ft 162bhp at the wheels running 1.2 bar. At 2500-4000rpm I have 1.2bar and then it drops smoothly towards 1.0bar at 6000rpm. This is with a Dawes set to 1.2bar.

Wondering if it was the Dawes I unplugged my wastegate completely I still do not make any higher boost from 4500rpm up.
(CAUTION - do not unplug your wastegates).

A Superchipped car was running and managed to hold onto its boost better - it held about 1.2bar until over 5000rpm and thereafter was 0.05-0.10 bar higher, although my car made more power at the flywheel, the wheels and more torque at the top end.

The only thing I can put it down to is exhausts - we both had panel filters, same octane AFAIK, and full decat - he had full Magnex, I have Magnex DP, Prodrive decat centre and backbox (as part of PPP).

Could the exhausts explain this difference? Cars are both MY99/00.

Now I am happy that my car is producing more power with less boost, but want to know why. Presumably my Prodrive ECU is giving better fuelling and / or ignition at the top end and this makes up for the lower boost easily.

Didn't you try out the EBC on the rollers?

I didn't have it developed enough. It was my first time on the rollers and I knew the Dawes held steady and safe boost and there would be no surprises. I would need to put a few miles under the EBC before I would be confident about it going on the RR.

As it was my boost only reached target at 3000rpm whereas it reaches it in 4th gear at 2400-2500rpm on the road - they did not turn the load on the rollers until too late IMHO. Also the TMIC fan was woefully inadequate and there were a few tiny flat spots which we think were ignition retard. It was a few miles on the road before it felt its usual perky self again which would back this up. Another car was audibly detting on the rollers which doesn't on the road.

I would have thought that exhausts would make a difference.... Only a like for like would show otherwise??????

As I said in the other thread - I've just fitted the Dawes. It holds at 1.1 bar and steadily drops to 0.9 at about 6000rpm just for info.....

Not sure any of that was any help :confused: :rolleyes:

John

It could be that the Superchipped car had the wastegate rod adjusted.
This would make it hold more boost top end.
When you disconnected your wastegate pipe, the spring in the actuator would become the pressure controller. Weaker spring = less boost.
Maybe you could try shortening the wastegate link bar, this increases the tension on the spring and holds boost higher.

5 minute job if you know where it is !!

Andy


[Edited by Cosie Convert - 1/20/2002 6:20:03 PM]

The rod was one of my thoughts but neither Superchipped car had it adjusted. Perhaps it is just off a bit on my car. Can you explain in any more detail how to do it? I can see the rod and what looks like a nut on it.

If I can't work it out I'll need to pay you a visit :)

[Edited by john banks - 1/20/2002 8:23:09 PM]

perhaps the rod is adjusted as part of the superchip fitting.



[Edited by T-uk - 1/20/2002 10:38:51 PM]

john,

just re-read your lead post,

quote,"although my car made more power at the flywheel, the wheels and more torque at the top end."

for fcuk sake your results are better,chill :p

The rod length adjustment may well be part of the Superchip 'package' how else do they up the boost ? It's not in the ECU.
Do they fit a bleed valve with the Superchip ?

LIMITING BOOST FALL OFF AT HIGHER RPM

If you remove the turbo heat shield you can access the adjuster rod.

1 - Carefully remove the tiny circlip with a small screwdriver (if you drop it you will never find it !)

2 - Slacken the 10mm locking nut on the rod end

3 - Push the rod towards the rear of the car to take the tension off it, at the same time gently lifting the rod off the wastegate
arm.

4 - Screw the clevis (bit with the round hole) up the threaded rod.
You can normally take it 3 - 4 turns initially, then subsequent finer adjustments are required as you fine tune the boost.

5 - Reverse of above to complete.

If you push the wastegate rod after each adjustment you will feel the difference in tension and available travel.

Any problems, I can do it for you.

I would recommend that you keep an eye on charge temperatures as what I've read leads me to believe that the TD04 starts producing more heat than boost at higher RPM ??
Also, you may need to re-adjust the Dawes to compensate.

Andy
Oh, final tip, don't do this when the car is hot !! Ouch.

CC,

the superchip does use a bleed valve as part of the kit.the rod could still be adjusted though,lets face it,tuners will not give away their secrets to the public,just because people have discovered the components to a superchip does not mean that is all thats done.

T

I'm not sure that the wastegates are set very accurately from the factory anyway.
When I changed my downpipe recently, I had a poke about the turbo and noticed that the wastegate was not fully shut, I could rotate the disc valve with my fingers !
I had to adjust the rod just to get the valve to seat properly.
It did not look like it had been tampered with since new as the nuts were 'creaky' tight.

No wonder it was gutless !!

Thanks all, esp for the instructions CC.

T-uk the wastegate rod could be part of the explanation for some late cars being gutless then?

Mark V from EMS has been very helpful. I think I don't want any more boost at the top end on my weedy turbo. But I still might want to adjust the actuator to see if I can stop the boost dropping between 4000 and 5000rpm. What do you think? If I use my electronic controller I could use that to keep the boost safely down at the top end and tweak the actuator to allow me to keep it higher until 5000rpm.

I am still a bit puzzled - with all manual and most electronic boost controllers the wastegate will be shut at the top end. Is this safe if the turbo boost is appropriate - ie 1 bar @ 6000rpm?

Is it possible to get the same boost with the wastegate open a bit and would this prolong the life of the turbo?

Can someone that knows about turbos sort my head out please? ;)

John

Don't know that I'm the one to "sort your head out" !! Thought you may have more connections there !

But, back to turbos. If you feel the tension on the wastegate actuator rod, it is very little. Without sitting on the turbo, observing it at full boost I can only speculate here. I consider that, even with no pipe fitted, the wastegate actually opens slightly on it's own accord due to the backpressure built up in the exhaust turbine inlet. This backpressure is at it's highest at high RPM. That would explain why your boost still controlled over 5000 RPM on Sunday but you hit fuel cut at lower revs.

One way to check this theory is to adjust (increase) the tension on the wastegate actuator and observe the boost profile.


cc

john,

just trying to rule out another possibility.

could this have anything to do with the enlarged bleed hole on your Dawes.

Don't know what the factory tolerance for the wastegate actuator rod tension is, but in Saab turbos it's plus or minus one full turn of the endpiece: see the link pasted in below for explanation of how latest generation Saabs do boost management. They say each turn of the endpiece equals around 0.03 bar or about 0.45psi "base" boost -- the ECU or alternative boost controller will manage the peak boost.

http://216.78.172.244/Trionic/trionicpg1.htm

The wastegate is set "soft" to shape the boost curve and let it build progressively, and tweaking it 2-3 turns tighter does make a noticeable difference to low rpm pick-up, especially in the 2K to 3K rpm range. Once on the boost curve proper, the difference is marginal.

Thanks Brickboy.

John - It is nothing to do with the Dawes as it still did it with the wastegate unplugged - this is the highest boost any boost controller could give you which is why I unplugged it to see if the Dawes was the limiting factor.

[Edited by john banks - 1/21/2002 4:43:32 PM]

and you think you're brains goosed :o ,totally forgot you unplugged the wastegate.only excuse is it's been a slow day and I'm 1/2 asleep :) .

come and try my straight through centre first and if that does not work try my b/b :D .

Thanks guys!

I tightened the actuator by 3 complete turns and it works a treat. The spool up is maybe even marginally quicker, and even with the bleed/Dawes I sometimes get a tiny peak which would go with that.

The great thing is the boost now holds much better so that at 5000rpm it is still about 17 PSI, at 6000 about 14.5-15 PSI and thereafter just goes down as before to about 13.5 at 6500rpm. So not too much at the top end but a useful boost like the best TD04L boost curves I saw on the RR day.

I have not adjusted the Dawes and now it is about 18-18.5 rather than 17.5-18 as before. In 5th it can reach 19 but goes down pretty soon. No fuel cut. I'll watch it for a few days - might turn it down a bit, but it has to hold about 20 for a few seconds to cut out.

Goes like a rocket. Very pleased - for now.

I have been wondering though... My Dawes is off the turbo outlet. Because of this I would hope not to be overspooling the turbo as I might if the input was after the throttle. But even then at high boost and part throttle there would be quite a pressure drop across the throttle. Is this an issue do you think? I don't know what turbo surge would feel like? Any thoughts? Am I likely to be near? There are so many assumptions about volumetric efficiency and even finding a good turbo map is difficult.

Now who thinks I would now get >170 PAW? ;)

[Edited by john banks - 1/24/2002 2:09:16 PM]

John,

You can better adjust the Dawes to achieve a little lower max. boost and keep the wastegate in this position.

It will now suit also your boost controller with rev. dependant boost target! (the maximum possible boost should be a little higher as the target)

Mark Verhoeven.

Thanks Mark.

I think I need to increase the Dawes bleed hole some more and turn down the Dawes a bit - the part throttle response is very frisky again - can get full boost at 60% throttle - it felt like the Dawes did originally without the bleed.

I could write a book on mechanically tuning your boost curve ;)

I've got the rest of the bits to make the EBC on a much smaller board for permanent installation. Just to add the RPM code and self learning of boost targets from a manual duty cycle map and we are in business.

I have had one approach suggesting they could market it, but I think I'll keep it open source - then I am convinced it will be developed better. Anyway, it will not be fun any more if I get paid for it and I do doctoring to bring in the pennies.