Luke

We have had a lot of technical chitchat.... "To Drill or not to drill"etc. I fitted mine and have driven it a bit.I drilled the hole to 1.mm. Stretched the spring a bit.
How far down have most of you got it wound down???ie how many turns to go before end of thread?? Yes it is faster when i get to the 4.5.6k rpm range. But can it be made to come in earlier???

Anyway. How do you find it has changed the way you drive your car. There has been many warnings about "Be carefull its scary" at first. Hav'nt found that yet.

Luke

t

catflap

Thinking of getting one myself, along with their air fuel sensor, it seems pretty cheep.

How good would you rate the mod? its cheep enough does it make the acceleration faster?
My car is standard apart form de-cat and end can

Dizzy

er omg.. what are you onabout ?

catflap

i made perfect sense ........didn’t i?????????????// LOL

Luke

top

SPEN555

Luke,

My two pennies worth.

Because I have upped the boost I find myself having to keep an eye on the rev counter to make sure I don't redline it.

What I now need is for John Banks to come up with a device which bleeps at say 6,500rpm to advise me to change gear. LOL!

Seriously though as the majority of my mileage is in 30mph traffic I don't really get to compare it properly. The car is going on the rolling road on 3/2/02 so I will see if it has made a difference then.

Damian.

T-uk

do not know about the bleeps but a dash mounted light which comes on at 6000rpm would be good.

what sort of budget should we give him?,may be a fiver .

Luke

Dont even think about Starting John "stickyback" (Johns new Nickname!!)Banks off !!!

20 of you got these and only a few are "Feeding Back"....
Come on guys!!


Luke

john banks

HowardB I think made a circuit for a shift light using a PIC, which he is trying to dig out for me for RPM decoding routine using a PIC. But I am a crap driver and can easily manage to change at my target engine speed. So it can't be beyond you lot. If I am absolutely hammering the car, I change up between 6000 and 6500rpm. Surely with >700rpm to go before the red line you can manage this one? Change up lights/buzzers are for racing drivers (or people that like useless flashing lights) IMHO No offence but get a life

Jay m A

iTrader: (2)

Feedback from a MY95 WRX

Very pleased!

Spool up does seem quicker than before, bearing in mind I have a full Scoobymania exhaust and K+N panel filter with the resonator removed. Before fitting the Dawes I could get peak and held boost to differ by over 0.1 bar in some cases, but now there is hardly any difference .

I have found fuel cut at around 1.1 bar so the Dawes is set to 1.0 bar - this is on my gauge so it may be a tad higher real world.

I am running the larger TD05 turbo (the old, big, laggy one) so neglected to drill out the hole or use a bleed valve in-line. Drivability is more than adequate in my setup IMO, granted it may be too manic for the TD04 guys. I don't suffer from 'part throttle - full boost' instances, if I squeeze the throttle in 5th when cruising at 3500rpm the boost will rise to 0.5-0.7 bar or so...all be it rising quicker than before. Not too sure why though! I think its because I squeeze then back off a tad .

ECU resets! I started another thread airing my concerns. My99 onwards don't really need to reset but should you ever want to (like I do, cos I'm like that ) please note that the ECU limits boost via the boost control solonoid immediatly after a reset whilst it calculates the quality of your fuel. Since the Dawes bypasses the solonoid its up to you to limit the boost. So don't rag it straight after an ECU reset. That is purely my advice based on my understanding of ECU reclibration after a reset - not gospel!


Justin

Luke

More donations required today!!

PeterPerfect

Very impressed with the performance improvement of the Dawes.....
But.....over the last 3 weeks I've noticed less boost being generated.
I'm gradually winding the Dawes back up again to get the same boost.
Is this the weakening spring problem I remember reading about ?(search facility off line).

Ta P.

john banks

I stetched my spring a bit (ooeeer ) and since I have not had to adjust it. For what seems ages now I haven't fiddled with the Dawes at all and it still makes 17.7-18PSI every time. Maybe 17.5 in 2nd gear.

It is probably just bedding in and the spring is settling.

Luke

About the "How far the end" bit. Can anyone tell me how close to the end they are. ie how far have you wound it down???
With the big turbo will drilling the hole to 1.mm make much difference???

john banks

If you are happy with it leave it alone. Before I stretched the spring the Dawes was almost totally screwed in. Now it is about half way.

More importantly Luke - you need to do it by boost gauge not by number of screws in!

PeterPerfect

I'll try stretching my spring a bit as well....is the heat that caused it to weaken ????
Luke - my Dawes was wound out three complete turns from fully closed....this did not invoke the fuel cut
John - LOL, you may not have physically fiddled with the Dawes for a bit but I'm sure you have in you're mind

Any idea if the wastegate spring could be wound up to give the same effect as a Dawes....i.e. with a pipe going directly from turbo to wastegate, it's spring set to open @17psi ?

P.S. I think John needs his own forum on ScoobyNet were he can hold 'consultations' about our boost related problems

Cheers Pete

john banks

It could be but apparently there are problems. The only reason I've not tried it is because it would be slower than a Dawes because of wastegate creep

I don't think the spring was damaged just getting a bit squashed whilst bedding in.

PeterPerfect

How would wastgate creep occur if the spring was set to open @17psi ?
In theory I'd expect the results to be no different to a Dawes.
I'm just wondering because it would be a more discreet modification

If the Dawes spring needed stretching because it was bedding in, whats to stop it needing stretching again after it beds itself in again after the stretch ?

john banks

Wastegate open enough @17PSI to cause equilibrium. Dawes closed completely and therefore wastegate closed completely until about 1 PSI before your set point. Massive difference.

PeterPerfect

So are you saying that even with the wastegate spring fully tightened it is not strong enough to stay closed until 17psi ?
Any idea what psi the wastegate spring will remain fully closed until ?

john banks

Standard wastegate spring is fully open between 8 and 10 PSI it seems. But it will dump boost earlier than a Dawes setup would as the Dawes keeps the wastegate fully shut and is only linear/log/possibly sigmoid shaped over the last few PSI I reckon. Result would be slower spool up. I am going to see if T-uk wants to try it on his car with a needle valve and solenoid disconnected and we compare it with Dawes on the RR.

PeterPerfect

What about fitting a stronger spring to the wastegate

john banks

Yes, but it will still dump boost earlier than the Dawes. The Dawes has the wastegate closed until almost at target boost. A stronger wastegate would just open by the same amount but at a higher pressure, but at low pressures you would still be wasting boost. So at 8 PSI even a strong wastegate spring that took you to 16PSI would be inducing wastegate creep.

A valve is easier to fit and adjust although less stealthy. But a stealthy mod would be to reduce your restrictor size and disconnect the factory solenoid or indeed change the wastegate spring or adjust the actuator.

PeterPerfect

Hehe...my own 'private' consultation session with Dr Banks about my boost problems..LOL

Thanks for being 'patient' with me John...I get the idea now.
Guess I'll just stick to the Dawes then

Oh, one last thing...do you know what I'd need to tap into to get an bi-state LED to light green @16psi and red @17psi?

john banks

MAP sensor middle pin (if MY99/00 don't know about others) or pick up at ECU with a Scotchlock -see link ECU manual for pinouts.

Put it into an op amp and set a comparator voltage (pick up a handy 5V reference or make your own with a chip). If you use the supply voltage for the sensors make sure you don't overload it - R=V/I if you make the current about 1mA R = 5K. In other words use a 5K pot or higher - connect one side to 5V other to 0V take your tap off the middle for the comparator. If exceeded the output will go high which will power the LED through a resistor. Use a second setup for the second LED. You'll need to think more about how to use a tristate LED - depends on type. Clearer with two LEDs I reckon. Use fast action LEDs. Don't short anything esp if you use the voltage ref from the ECU or it could be very nasty indeed.

Better than all of that build a setup as per my AFR meter project and use a neat 10bar display and run from say 13-18 PSI in 0.5PSI steps. It is linear. The chip has the voltage reference on board and high impedance inputs >10Megaohms.

According to Bob Rawle - MAP output is 0.88 at -1.0 bar to 4.84V at +1.8 bar and is linear in between. This tallies with my readings also. 14.5PSI==1bar. Work out your voltages - about 4V is the region you will be looking at - you might need to experiment with different pot values for T1 and T2 in the AFR meter circuit. But you need exactly the same circuit as you don't want to read from 0V but say (not worked it out exactly) 3.6 - 4.2V


[Edited by john banks - 1/12/2002 6:48:11 PM]

john banks

We tried T-uk's car with solenoid disconnected and smaller restrictor sizes. Boost was all over the place. You need different restictors at different RPMs - hence a different solenoid duty cycle at different RPM to get flattish boost curve.

I am currently investigating the working of the Link, Unichip, HKS and AVC-R boost controllers to come up with my killer plan. Link seems to use a base wastegate duty cycle and RPM mapped boost targets which it then homes in on to avoid offsets. Unichip so far seems to use a static duty cycle map based on RPM and suffers from gear and environment dependent offsets. HKS has adjustable offset and self learns parameters so is less obvious. AVC-R uses RPM dependent duty cycle AND target boost, as well as duty cycle offsets for different gears. Latter needs a lot of input from the user.

I might go for static duty cycle for all revs which is ballpark with it being adjusted by a PI algorithm which should correct for gear and environment and avoid offsets.

Luke

John. Steve Lawson phoned me today!!!! He is going to fit and set up 2 next Saturday. His clients are going to a session at "Power Engineering" I hope to meeet up and get him to sort mine out with a gauge. Imagine the "Kudos" "Mine was fitted by Steve Lawson!!!!!

I bet he has been reading all your posts for info. If I ever make it on to "Who wants to be a Millionaire" If it comes to any technical questions .I'm calling you!!!


Luke

john banks

I would be very interested to know if any of the cognoscenti have any opinions re Dawes, apart from the obvious worries of people not being sensible with the boost. At least on late model UK cars most of the time the upper limit of boost is due to the turbo, and fuel cut stops you going silly in the midrange.

Cosie Convert

Pete

You can actually fine tune using the Dawes and the Wastegate adjusting rod. The Dawes effectivly sets the low to midrange boost and the wastegate rod/ spring tension can adjust the drop off at the top end. ( or eliminates it if you have a bigger turbo such as a TD05 )
I wouldn't recommend tampering with the wastegate rod on a TD04 as the turbo is just too small and you risk serious damage by trying to hold more boost top end.
On my 95 WRX I bypassed the factory solenoid valve and adjusted the wastegate rod ( before fitting any dawes valve) to hold 15 psi from 2800 to 7000 rpm.

cc