PeterPerfect

Thanks for the info cc.
How did your car drive with the wastegate set to 15psi....did you experience any creep (slow spool up)?

"....TD04 as the turbo is just too small...." LOL....I think John has already found this...18psi @3k chocking to 13.5psi @6.5k
I run about 16psi so am really in the same boat I guess..i.e. turbo will be maxed out @ high rpm.
So, does that mean anyone running the Dawes above 13.5psi will max out the turbo above 6k rpm ?

Just read scary postings by cc about piston pressure & outlet temperatures....
Knock, knock.....whos there?
Det, DET, BANG

FMIC anyone

Oh, does anyone know where the worlds biggest turbo is fitted ???

Cosie Convert

Pete

You want big turbos ??

The last ship I was on had 3 off GEC turbos 300KW each (402 hp) being transferred from turbine to compressor wheel. The compressor wheel was 480 mm diameter and the turbos complete weighed 1500 Kilos.
But then the engine they were feeding was 18,000 shaft horse power !
Yea, size matters I guess !!

I can't talk from experience on the TD04 on your car, all I would suggest is, as John says, monitor AFR, Det and charge temp before and during tweeking boost pressures.

For the record I didn't notice any difference in spool up whether controlled by a dawes in the supply line or by the wastegate spring. They both do the same thing, hold the wastegate valve shut until a preset pressure.
The drawback doing it on the wastegate only is that you can run out of travel on the (standard) actuator. This can cause the boost to continue to rise at high RPM (really don't want that !)
Fitting an uprated spring/ actuator is the way it's been done on Cosworths for years.

If in doubt..........don't !

cc

PeterPerfect

cc

Man they are BIG turbos...now I know why you think my TD04 is so small !!!!!!
I'd love to see some pictures of them...I'll see what yahoo can drag up !
I can just picture it now...John's car with one of the turbos strapped to the roof

Did you tweek your Cossie much ?
Is there any reason why the cossie folks use beefed up wastegate springs in preference to a Dawes ball/spring type device ?


If in doubt...PRAY

Yawn...bed time.

Cosie Convert

Cosworths tended to use uprated actuators because they were available ! Bleed valves are also very popular.

I guess the reason Dawes valves were not used was because they were not known about ?? The Cosie guys may be trying them now ??

I certainly have a steadier and more repeatable boost setting with the Dawes than I ever had with a bleed/actuator.

I used my Cosworth for circuit racing in the road saloon class, running approx 340bhp with 21psi boost. Reliable ? hell yes, It won 13 out of 14 races in the 98 season at Knockhill (the one it did not win was due to a brake fault)
59 second laps on road tyres, stock intercooler, stock T3 turbo and engine internals.
I'd like to think my Scoob could do that but I doubt it !

PeterPerfect

cc
340bhp @21 psi......figures I can only dream about with my poxy little TD04
Was it 4x4 transmission...or did it all smoke out through the rears

So do you plan to race the scoob..or just doing track days ?

Cosie Convert

RWD only.... great fun !

All very controlable though, I had a 1/4 turn 'V' ported ball valve
fitted in the wastegate bleed line. This was linked via a minature rose jointed rod to the throttle which is also 1/4 turn.

After a bit of set up involving different restrictors in the supply line, I had it so at 1/4 throttle, I had 1/4 boost, 1/2 throttle = 1/2 boost and so on, up to full throttle where the bleed was full open and allowed full boost.

The set up totally overcomes the part throttle boost spikes and the consequent power surge. Not so critical on 4wd but would still make it nicer to drive.
It also stops the dump valve squealing and recirculating so much hot air through the turbo.

I need to make up a similar set up for my scoob sometime !

PeterPerfect

Fantastic stuff cc...340bhp and rwd, oh AND road tyres
Your 1/4, 1/2, full throttle device thing sounds interesting. There are a few Dawes users who are experiencing too much boost on part throttle...resulting in high inlet temperatures.

john banks

High exhaust gas temps.

On a MY99/00 UK there is no leanness at part throttle from what I have observed if you put a 1.5mm bleed hole in the side of the Dawes and boost is quite linear.

Cosie Convert

High inlet temperatures ie charge temperature, not exhaust.

With the proportional control valve attached to the throttle linkage 90% throttle will give 90% boost.
With the dawes, if you try it at 3 - 4000 RPM you probably have 100% boost from 70% throttle upward ?? John ?
This is what adds to the 'over eager' power surge on wet roundabouts.

john banks

No I only get full boost at full throttle - probably because I am running so much boost for the turbo and the small additional bleed.

Before the bleed when I was running 17 PSI I could run 17 PSI on 3/4 throttle and all the last 1/4 of pedal travel would do was increase my richness by about 2% CO! Worrying. Doesn't do that now. It is just as smooth as stock - I swapped back to check.

Some aftermarket chips do not have TPS modulated boost control and work OK. I don't think I will get much better than the Dawes even with my EBC design, but we'll see.

"High inlet temperatures ie charge temperature, not exhaust." Problems the I-club guys have documented have been EGTs not charge temps by full boost part throttle. At part throttle for the same boost there is less charge per unit time hence more cooling by the same intercooler? So the inlet temps would be lower at the same boost on part throttle compared with full throttle, or have I missed something?

[Edited by john banks - 1/13/2002 10:41:44 PM]

Cosie Convert

The TD04 on your car is responding completely different to my TD05
which, I guess has to be expected.

With the TD05 I find it most difficult to hold, say 10 PSI in 2nd gear without going up and down a fair bit with the throttle pedal as the engine revs up and the turbo spools up to speed.

What the prop valve does is opens the wastegate at part throttle.

My understanding is that the Dawes will hold the wastegate shut until target (ie full) boost is achieved, regardless of throttle position.

The benefit (perhaps only on a bigger turbo) is that full boost is only generated when it's needed.
(In order to monitor this you need a gauge upstream of the throttle butterfly to see what pressure the turbo is pumping at)

As you say John, some OEM ECUs use TPS for this purpose.

Cosie Convert

"At part throttle for the same boost there is less charge per unit time hence more cooling by the same intercooler? So the inlet temps would be lower at the same boost on part throttle compared with full throttle, or have I missed something?"



Yes and no ! You are correct on the first point...but the dump valve is flowing like mad, recirculating hot, compressed air back to the turbo suction to be compressed and heated again, and again.
The EGT probably increases partially as a result of charge temp and partially because exhaust pressure is up due to the closed wastgate.

PeterPerfect

Should I drill my Dawes bleed hole to 1mm ?
What effect will it have on the boost/throttle ?

john banks

"Before the bleed when I was running 17 PSI I could run 17 PSI on 3/4 throttle and all the last 1/4 of pedal travel would do was increase my richness by about 2% CO! Worrying. Doesn't do that now. It is just as smooth as stock - I swapped back to check."

If you are running a MY99/00 I reckon 1.5mm is about right. It rids you of TD04L boost spikes and the above part throttle full boost issue completely.

PeterPerfect

Thanks John

PeterPerfect

Blimey John, that reply was quick considering the question !

I've been following your AFR thread with interest (even if I don't understand it all )
Guess I better blow the dust off my Maplin catalogue

Thanks again.

spelling

[Edited by PeterPerfect - 1/12/2002 7:23:34 PM]