john banks

http://www.i-club.com/forums/showthr...postid=1134941

It seems that our i-club counterparts have been having trouble with progressive loss of performance after fitting MBC very like the Dawes devices product. Apparently they are quick for a while and then the performance drops off to below standard. Theories behind this are the ECU pulling timing as a result of detonation on part throttle/full boost conditions which is not a state the original ECU's fuelling is set up for. It seems that the exhaust gas temperatures can rise quite high suggesting lean running. It seems that the closed loop system is not capable with dealing with this abnormal state.

It strikes me that the safest way to install the Dawes is therefore to install it in-line with the factory boost controller - ie between the turbo "nipple" and the brass restrictor, leaving the factory solenoid in the picture, and therefore running at OEM boost levels, but reducing wastegate creep by running the Dawes at low levels. If the boost is then desired to be raised it could be done with an additional bleedvalve either in this line or probably better in the line off the T-piece running to the factory solenoid.

Of course these are only my ideas, and still somewhat theoretical.

The same think would also apply to Electronic boost controllers presumably unless you can set targets for various throttle openings/RPM.

I would value any input here....

john banks

Forgot to say, this would make it tricky to also raise the boost at high RPM thus limiting any extra power that this device might safely give in the rich environment of wide open throttle conditions, which was one of the reasons for doing it...

Also, these guys are referring to MY01's, and I don't know if they have all their cats. This could make the problem worse for us or better I cannot work it out, just thought I would throw it in as a thought...

Can anyone that has run an EBC comment on whether they see full boost at much lower throttle openings than previously and whether they see any knock or lean running? Nito? Mr Tang?

john banks

Can anyone tell me if I'm talking complete rubbish here or not?

Thx.

HarryBoy

John,
I have been running the Dawes Device for about 2 months on a MY00 Wagon.

I can confirm that the car feels sharper on part throttle, the boost seems to rise quicker than before. I have set the peak boost to 15PSI and it is now held for longer than standard, only the natural roll-off of the TD04 causing boost to fall, 14 then 13PSI, at the top end.

At PE the car was fueling correctly no sign of det. I am running Optimax, always! I mounted it between the Turbo nipple and the wastegate actuator, then plugged the duty (boost) solenoid pipe.

The only issue I have had is a sticking spring/ball causing the boost to go way high, there was no fuel cut!!

Harry

john banks

Presumably at PE though you were only testing at full throttle?

There was talk on the I-club thread of 20% throttle leading to 15 PSI instead of the usual 5PSI. Maybe I am flapping about nothing...

[Edited by john banks - 20/11/2001 15:26:07]

HarryBoy

Hi John,

Yes at PE the RR run is done at WOT. And yes you can hit 15PSI at part throttle, I presume it is under this type of condition that is the main cause for concern?

I don't know what my car's CO% is under these conditions. I need to get another run done as the first was without the SS DP that I now have and I would like to be reassured that all is OK....

Harry

PS John, I have just re-read the i-CLUB thread and I don't get the drop off in peerformance noted there.....



[Edited by HarryBoy - 20/11/2001 16:15:02]

john banks

Thanks Harry that is helpful to know. I originally thought that the ECU would work out the required fuelling from MAF, MAP and lambda data.

I don't know when the ECU goes open loop, but apparently the problems occur over about 10PSI on part throttle with EGTs of 900 degrees C. [edited as I realised they were talking in deg F]

Does the ECU go open loop at certain boost, or is it dependent on load/RPM as well?

Will a car with a MBC running at 15 PSI be quicker than one which holds 17PSI in the midrange in 4th and 5th gear but drops things more at the top end than the MBC car?

[Edited by john banks - 20/11/2001 20:31:58]

HarryBoy

John,

"Does the ECU go open loop at certain boost, or is it dependent on load/RPM as well?"

Good question, that's one Bob Rawle could answer. I recall him saying that a UK spec cars goes open-loop around 4K RPM but I have no idea if it is linked to boost pressure, Bob are you reading this?

"Will a car with a MBC running at 15 PSI be quicker than one which holds 17PSI in the midrange in 4th and 5th gear but drops things more at the top end than the MBC car?"

Another good one! It may depend on how you drive the car, on the road my feeling is that more boost in the midrange is what you want for flexible day to day driving, if on the track you may want more power at the top end....

Harry

john banks

Sounds like this is a particular worry if you still have the up-pipe cat before the turbo as in MY01. Then it can melt is and bit of dead cat fly round your turbo and shatter it into your engine (apparently).

[Edited by john banks - 20/11/2001 19:07:38]

Bob Rawle

edited as double post

[Edited by Bob Rawle - 20/11/2001 22:04:31]

Bob Rawle

Car goes "off lambda" ie sort of open loop as soon as you get to about 0.2 bar, revs are not involved although I would hope that above 5500rpm its not being controlled to stoich as it would det at those revs even on zero boost.

What will happen is that if boost pressure is higher than intended at part throttle and you achieve a higher boost than normal for a given throttle then the efficiency point chosen (from the map) will be different to the norm. This could then mean the ecu fuels the car less as although the boost is higher the throttle opening is less. The maf sensor "picks the point" for open loop control but uses throttle position to determine efficiency, map is used for boost control only (unlike some aftermarket ecu's like Link) and so does not greatly influence the amount of fuel provided.

The trick has to be to set the system up so that you achieve approximately the same "efficiency" point but taking advantage of the extra boost and not leaning the fueling out too much.

WREXY

Hi John,

I don't know if this helps. As I've said before, I'm running a Blitz DSBC electronic boost controller on my MY00, together with a 5 Zigen exhaust mid section (catless mid) and backbox and APS cold air induction kit. I've set the boost on 1.2 kg/cm2 which is 1.17 bar. The boost is higher on part throttle than standard, around 1.05 bar, this can be programmed, (it's called the gain) and the knocklink shows no detting. Certainly nice throttle response.

I've run the car like this for over a year now and there has been no performance loss at all. To give an example, I friend of mine has a MY00 with PPP, falkland twin down pipe, HKS exhaust manifold and APS induction kit. He got 271bhp and 35kg torque don't know what that is in foot pounds, on a RR. Actually that figure is without the APS kit. So maybe he has a little more now.

We gave them a bit of a squirt from a rolling start at 3000 rpm. Although he got about half a car length start on me I managed to catch up to him and just get him by a nose, just shifting in to fourth gear.

So I have no detting according to the knocklink, no problems and no performance loss yet.

Cheers,

Wrexy.

WREXY

John,

Just re read the thread and noticed 15psi at 20% throttle. With my car at 20% throttle I see around 0.78bar. As the throttle is increased it goes higher. By around half to 3/4 throttle I see around 1.05 bar. When cruising on a straight (level that is) road or downhill and not applying an increase in throttle, but just holding the throttle, even to just under 1/2 or 50% throttle, boost goes in to the minus area, that is under 0 boost, unless I'm going uphill ofcourse where I may see 0.3 bar again depending on throttle.

You can't set the gain, that is, program the boost controller to bring on boost for different revs or fuelling, You can only program the boost controller in the way or how sudden or less sudden it brings on the boost.

Cheers,

Wrexy.


[Edited by WREXY - 20/11/2001 22:15:22]

john banks

Thanks Bob and Wrexy very helpful stuff.

Wrexy - my car is very similar to your friends except vanilla K&N 57i and no manifold.

You have a dual solenoid boost controller from the looks of it, so does it link to the TPS to determine which solenoid to use? Can you set the throttle position where you want full boost? Doesn't look like you can do this with HKS EVC IV, but the guys running this also run about 1.2 bar so presumably they reach this on part throttle (without problems apparently)? Your data at least tells me that 15PSI at part throttle will prob be OK.


SORRY CROSS POSTED. Will check out my figures when the MBC goes on and hope they are ballpark to yours. Any other thoughts let me know here... Thanks.

[Edited by john banks - 20/11/2001 22:16:39]

WREXY

John,

The Blitz DSBC bypasses the standard solenoid. It has it's own box (solenoid). One pipe comes out from the turbo and goes into the solenoid and the other pipe comes out of the solenoid and goes into the actuator. The pipe that came out of the airbox area, which used to go to the standard solenoid is blocked off, so that it does not lean out the mix.

You can program the boost controller for full boost settings at the throttle positon you want, after experimenting, but when you floor it fully, the boost will go crazy, so moderation is needed. You can't set it for full boost say at 3/4 throttle and then maintain that at full throttle. It will go over at full throttle.

As for my car and my friends car there was not much in it. As you read, I just got him, that time. They are that close that maybe on a different day he could have got me.

Cheers,

Wrexy.