john banks

Whilst on the way to trying to do something electronic to calm down the spool up of the turbo on part throttle or small throttle movements, I decided to try again a restrictor valve with the Dawes. Previously I tried this after the Dawes but the boost was all over the place. I think this was because the restriction had to be quite tight to make a difference and this meant the feedback system was too slow to open the wastegate to avoid a peak.

However, today I tried my restrictor valve off a T-piece after the Dawes. I closed the valve entirely and then set the Dawes to about 13PSI - about std for a normal ECU - it really felt slow! Then I gradually opened the bleed valve until I was back to 17-17.5PSI held boost. It had to be opened about half way (5 turns).

The net result is very good indeed. The spool up is still very brisk, but the wastegate now opens gradually in the last 4PSI as it reaches target boost. This results in no overshoot at all. None of this was expected. What I wanted to achieve was slightly less mad throttle response on part throttle on part boost. This has also occurred - the response is softened and it is a bit less manic on corners now. It does also seem to need more throttle opening to get full boost which some of the I-club guys said. It still tapers the boost at the top end.

Notably when running at 13PSI with the bleed valve closed the torque curve felt very flat indeed with no huge wallop in the midrange compared to before, and it genuinely felt as though it was quicker at the top end again - almost a normally aspirated feel as opposed to a small turbo. Felt quite good surprisingly with obviously more torque coming in until about 5000rpm from the feel of it, but the hump in the midrange is what makes it go really quickly.

Certainly I would recommend doing this to anyone that wants to make their Dawes more civilised. I may even not bother doing any fancy electronic control now it is that good.

This is effectively the setup of the TurboXS HP-MBC.

The other good feature to this is that it is much easier to turn a valve to make an adjustment as other posters have pointed out rather than undo the Dawes hose and twist the device until you get the boost you want.

Also, if the overboost spikes are less or absent then it will make me a bit more confident that the thing is not going to overdo it and make me more likely to run well into the 17s PSI. When I see peaks over 18 I am unhappy. If I keep the peaks low I can bring the held a bit higher. But I'm not going over 1.2bar - no point with this turbo.

[Edited by john banks - 12/23/2001 5:37:29 PM]

Sam Elassar

all very impressive and every thing, but why are you so parnoid with a little of overboost ? 1-1.5psi overboost is not really going to hurt your car in anyway, shape or form. a little bit of overboost is good i think .

sam

john banks

Indeed not Sam if it is predictable, repeatable and independent of environmental factors. Which with an MBC without bleed it patently isn't. And sometimes 17.5+1.5 peak is getting very close to fuel cut on PPP although I think it needs to be sustained for a fair old time. The factory boost control solenoid would be going mad at this level of boost if it was connected. I would also be concerned if the ECU is pulling back the timing because of spikes. But without a spike it seems a heck of a lot smoother and I am wondering maybe even a little quicker overall. Certainly the end resulting boost is the same as before, just takes slightly longer to get there. The main intent was actually to soften throttle response. Now by adjusting the contribution from bleed and ball-spring you can set your spool up enthusiasm to suit. With the MBC as stock it is just a bit too snappy. Like this it drives as smooth as OEM with a great shaped boost curve, is not twitchy in bends and seems to be much more controlled. Best £25 + £10 I ever spent. I know people knock these MBCs but this setup is really impressive. And sometimes 17.5+1.5 peak is getting very close to fuel cut on PPP although I think it needs to be sustained for a fair old time.

Of note I was seeing 5PSI peaks with the restrictor valve in line rather than bleed config and it was unpredictable and horrible to drive.

It may be that the Dawes behaves better if it can open and stay open properly when on boost rather than crack open and perhaps oscillate. The boost holds more steadily in this config.

[Edited by john banks - 12/23/2001 11:36:31 PM]

T-uk

john,

no more excuses ,get it up to Star so we can just how smooth the boost is.I think Sam is organising a mini-day in the new year to get figures on his new car,so ask him nicely if you can take part.if you do get some figures send them to teknopete in the scottish forum and he will put them on his site to compare with others.I personally feal the power@wheels and torque to be the important ones.

john banks

Beastie suggested that Dynos can damage your tyre sidewalls - any comments? Subject to being reassurred about this I will put it on the dyno. Sam?

It will certainly be no monster power machine, but I would hope to see a nice torque curve. But even if it said 180bhp at the flywheel I know it is vastly quicker than stock on the road - not a great believer in dynos I have to say.

Sam Elassar

i don't knock the MBC, think it is very good value for money. if it was not so hard to get one of these i would have tried one myself for mean while.

if you don't like RRs bring it to track then .

on a more serious note though, i don't know how many are interested yet, i thought PETE's car was going to be finished but it is not, so if you want i can phone jim and arrange couple of runs, if you tell me when is suitable for you ?

i don't see why would the RR damage anypart of the tyres ? unless it is not setup correctly.

have you fitted the lambda link yet ? what are you runing at the top end?

sam


[Edited by Sam Elassar - 12/24/2001 12:02:59 AM]

john banks

Greg (Beastie) took some pictures. It doesn't look pretty as I only added the bleed valve today, I have three different colours(fashion victim) of pressure hose and there is a dodgy tie holding the bleed valve in position. These will all be remedied, but functionally it works a treat.

john banks

A RR on a Saturday morning would be best for me but could also do a weekday afternoon with notice.

I am running my own "LambdaLink". Am getting >7-8%CO at anything over 1 bar boost. Reaching 1.2bar at 2500rpm depending on gear, and it falls off after 5000 to 0.9bar at 6000rpm and downhill from there! I think this is about the sensible limit on a TD04L.

T-uk

okay john,

I'll let you use my wheels and tyres ,I'll even change them over for you as I am about 10mins from Star

Sam Elassar

lol t-uk

john
can you run through how is this fitted again ? i know there is a lot of threads about it but i did not read them as they were too long
it looks like your 2 port soleniod is not connected there? does the mbc fit between the turbo outlet and the wastegate and then you adjust it to the desired boost kind of thing. does the MBC bleed the excess air somewhere then ? i suppose if it did it will just be a bleed valve

sam

john banks

Don't worry I'll use my own wheels and tyres. But I will be very cross if it shows a crap figure! Anyway, how do Star figures compare with PE or Powerstation?

Sam the two port solenoid is capped off as you spotted. I do tend to ramble in posts - sorry.

The Dawes is a ball bearing on a seat kept closed by a spring, the tension being adjusted by turning the barrel and then locking it in position. With the present setup the wastegate basically stays pretty much shut until around 13 PSI when the ball bearing is pushed off its seat. It is then connected to the wastegate actuator which would then open and hold boost at 13PSI as long as the turbo could (with sufficient throttle opening). However, the bleed valve coming off a T-piece after the Dawes makes the wastegate open more smoothly and gradually over the last 4.5PSI. You could set the contribution of the bleed valve to higher figures to slow the response more. I quite like it how it is.



Having tried bleed and restrictor valves before this is nothing like. At this boost level the factory boost controller kept pulling back the boost by changing the duty cycle, and if you are raising your boost much it tends only to increase the peak boost, and the response is wildly different in different gears. If you used just a bleed valve with the factory solenoid disconnected there would be massive wastegate creep and spool up would be too slow.

Of course if I do want to make this better I could use a solenoid (?factory one) instead of the bleed valve and change the duty cycle depending on throttle position and include some closed loop feedback too. I'll see how this one drives for a while and make sure it is reliable.

[Edited by john banks - 12/24/2001 9:48:22 AM]

T-uk

john,

I think that Star use the same type of rolling road as Powerstation,but you still cannot compare them as the operators use them differently,Jim @ Star will follow your power at wheels on his computer and once it starts to fall shut down the run where others may rev the car far higher after the drop,allowing for some high power@fly wheel figures,Star seems to be very consistant,my power at wheels has always been the same and others a few either direction.he can also plot fuelling and boost curve.

john banks

Well if there is access to others' charts in various states of modification it might be an interesting comparison. It would presumably fall short of the very best Linked TD04 cars as although the fuelling and boost seem pretty ideal from what I can tell, I am sure it wouldn't run quite so much ignition advance. Beastie thought it felt c.280bhp butt dyno, but whilst I think in the real world it is as quick as a P1 that is probably not because of outright power but having more power lower down and in I hope most of the midrange.

T-uk

you might keep with a P1 on the road but you would struggle on track,there is one doing K/hill with only a decat and up the straight it was not far behind Sams car when at 230@wheels.the guy is bloody quick on the corners too.

john banks

On the track the peak power must be more important I guess. And I meant a virgin fresh unmodded P1.

The Evos seem to do well with just breathing mods at Star.

Sam Elassar

hi there
i think jim's RR is on the conservative side compared to the rest of them, very simlar to PS. it is quite accurate for sccobs but it is not very accurate for EVOs. but as long as you compare like for like it is a very good reference point to wheather you mods are effective or not.

even if you have the same power as the P1 ( unlikely due to the size of the turbo) they will still be quicker due to the shorter gearing. if you think it feels like 280bhp on the road it is most likely 280lb/ft that you can feel.

i will phone Jim just now and see what he says re some dates.

sam

john banks

I'm sure you are right Sam. Dates would be good. £30 a shot or thereabouts still?

Can't find any P1 results at Star.

T-uk

hi Sam,

was looking at one of you runs and saw that your car was only revved to just over 6000rpm and got over 220@wheels,makes me wonder how high your fly wheel would have been if it had been taken higher,like they do down south.

Sam Elassar

probably a little bit more 340 area, but again maybe not. the reason the power droped at 6000rpm because i dropped the boost off to 1.0bar at 6000 from 1.35 bar.

star not answering just now, they maybe shut for xmas. which is fair enough at the end of the day we all seem to sitting at home playing with our PCs instead of working as well

i will try them in few days.

merry xmas


sam

john banks

Cheers Sam, happy Xmas to you too.

T-UK feel free to mail me if you want to meet up meantime - 27th or 28th?

T-uk

I think Gordon Shek with his new P1 could be interested in a run at Star,but do not know if the mongoose is fitted yet.

Scott.T

iTrader: (2)

Hi John,

Glad to see you came round to my way of thinking in the end. If you remember that's how I had mine installed from day one.

At present my Bleed Valve is set closed, but I am going to crack it open half a turn just to calm things down a bit.

See last post on http://www.scoobynet.co.uk/bbs/thread.asp?threadid=53568&Page=1 (not 1st posting, as this way didn't work).

[Edited by Scott.T - 12/24/2001 6:52:59 PM]

WillieF

Evenin' all

I honestly believe Johns Car will produce a very nice power curve however put it on the track and I don't think it will be so impressive and I am not talking about sheer straight line speed.

My car produced very strange power curves at Star but I like it and am going to be trading it in later in the year so I ain't spending anymore money on it for the time being.

Where did you get the Evo Sam?

john banks

Happy Xmas!

Scott I think you put your bleed valve BEFORE the MBC which when I tried it didn't change the part throttle response/speed of spool up at all but just gave a larger boost spike than with the Dawes connected straight through if there was any significant bleed. This is presumably because you have limited the pressure that the MBC dumps onto the diaphragm when it opens, leading to overshoot. Depends how much you have the bleed open, but all it did on mine was increase the boost spike significantly (not as badly as a restrictor in line with no bleed after the Dawes, but similar to one inline before it) or have no effect if the bleed was fairly closed.

I don't think the part throttle full boost situation is anywhere as bad as many make it out to be, but the range of throttle position from say 5 to 15PSI boost at certain revs is small. Using a bleed after the MBC smooths this considerably, whereas using one before it didn't when I tried it.

The described method here (from I-club Gabedude's post) is with a bleed AFTER the MBC. This works completely differently and on my car at least the results seem better. Would be interested to see what you think if you try moving yours and if you get the same improvements. The folk on I-club seem to like it.

It probably wouldn't be good on the track because 1 crap driver 2 crap driver 3 crap driver 4 no eibachs 17s or big brakes which toyos and minor brake upgrade would not compensate for. Also the torque delivery is much more suited to a road car. But on the road it is very good fun for very little expenditure.

[Edited by john banks - 12/25/2001 9:50:06 AM]

T-uk

john,

okay,you have run out of excuses for doing a rolling road day,so now you are going to do one ,now it is time to talk you into a track day,
excuse 1,2,3-can all be taken care of by a few laps with a track instructor .
excuse 4-surely you can do better than this,I have no eibachs,big brakes and have only recently fitted 17's.god,people manage with 2pots for **** sake .decent front discs and pads help.
excuse 5 to 500-you know I am always going to be back pestering you .

john banks

You're trying hard T-UK. I'll put the car on RR. Shouldn't you be opening presents now ?
Sadly no Eibachs/17s/6pots/Link/VF23 in my stockings, but the usual socks and cuddly toys. Oh well

T-uk

too right I'm trying ,just dropped in to see haw busy scoobynet is,you must sleep in front of the thing.

Luke

John
Have you tried putting a t-piece in just after the Actuator and fitting a "Christmas Pudding" in line ( Cooked). It could be worth a try.....

Happy Christmas to the ""Dawes Device UK Crew"


Luke

T-uk

lol@Luke ,

don't give him any ideas

Sam Elassar

ho god that could be another thread about the effect of xmas pudding on the MBC do you think it will make a difference inline,before or after the DAWE ?


willie
i got it from ralliart, they have got few of them.