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I have spent all weekend, going through all old threads on dawes devices and abbott racing MBC, trying in my non technical capacity to figure out which one is going to be best.

I cannot tell which is going to be better for my car which is a 91 CSE 2.3 FPT.

I know people have fitted them to there own cars, but has anyone fitted both and noticed any improvment in one or the other.

Also why does the dawes device only have 2 connection points and the abbott MBC have 3 ?

sorry another question, what is the advantage of a Dawes device dual stage boost controller as seen here. http://www.j-w-racing.co.uk/acatalog/Dawes...Controller.html

thanks in advance for any help
 

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With the Abbott device, all three pipes attached to the APC solenoid connect instead to the MBC. Thus eliminating the "unreliable" APC from the equation, I've not seen a Dawes device fitted to a 9000 so can't comment.
 

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Originally posted by Jason (Mr Torque-Steer):
[qb]I've not seen a Dawes device fitted to a 9000 so can't comment. [/qb][/b]
I have, and the results- a new engine required!


The Dawes basically holds off the pressure from the wastegate until a preset pressure is reached, and then it opens fully.

If everything is functioning OK, then I would recommend a bleed valve rather than either of the above. Basically it stops the wastegate from seeing the full pressure from the APC solenoid and thus provides a controllable increase in boost across the range whilst still retaining a reasonable amount of APC. It is fitted in the "W" tube from the APC solenoid.

The MBC effectively removes APC, and provides you with a tuneable boost. The Dawes effectively raises your base boost, but adds little to the top end performance unless you set it to silly levels which have the result I outlined above.

Basically, I wouldn't touch a Dawes on a Saab with APC. It's not worth the risk. £100 or so for a new APC valve (less s/h) is a lot less than shelling out for a new engine...
 

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Originally posted by Leon (9-5 stg2):
[qb]Was the Dawes Device the culprit in the ngine blow out..
or simply badly setup dawes device?

I think the latter...  [/qb][/b]
A bit of both, really... if you're only using a Dawes, you can only really raise the base boost ie the point at which the wastegate opens. So, it's fine for low boost but when you want to increase max boost it can only do so across the band. Higher up the rev range your standard turbo will run out of puff and become very inefficient, increasing the intake temp and inducing knock that the APC won't be able to curtail. That's how the engine I'm referring to was killed.
 

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Originally posted by Mark E:
[qb] QUOTE
Originally posted by Leon (9-5 stg2):
[qb] Was the Dawes Device the culprit in the ngine blow out..
or simply badly setup dawes device?

I think the latter...  [/qb][/b]
A bit of both, really... if you're only using a Dawes, you can only really raise the base boost ie the point at which the wastegate opens. So, it's fine for low boost but when you want to increase max boost it can only do so across the band. Higher up the rev range your standard turbo will run out of puff and become very inefficient, increasing the intake temp and inducing knock that the APC won't be able to curtail. That's how the engine I'm referring to was killed. [/qb][/b][/quote]Which is why when my APC was dead, I used a MBC set to a lowly 10psi (base plus a couple) to keep my engine alive until the APC was back in order.

Didn't Alan kill one of his pistons with an MBC set a tad high???

Andrew
 

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I thought that was just a vanilla bleed valve. With the bleed valve if you bleed too much boost away from the wastegate actuator your going to lean it out badly, which is what Alan did and he melted a piston.


*edit* with any of the devices we've mentioned so far, they all require the installer to set the device within sane limit's. Unless you buy an MBC with a very limited range of movement.
 

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Originally posted by Scaero (Maptun stg3):
[qb][Didn't Alan kill one of his pistons with an MBC set a tad high???[/qb][/b]
Yup, that's what I was referring to. I'm certain it was a Dawes he was using.

I perhaps ought to add that you can safely get high perfromance levels out of an MBC set up as long as you are careful.

I was nudging 300hp using the Abbott MBC but I also had an uprated intercooler and water injection to combat pre ignition problems.
 

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Supplier info:

MBC like Abbott supply: Forge Motorsport (£18+VAT)

This can also be used as a bleed valve by putting it in the W pipe only and leaving the bottom port venting to atmosphere.

2 port brass bleed valve:
Jondel Motorsport
RPM Motorsport

Note that the Forge/Abbott MBC is really nothing more than a 2 port bleed valve with a stem to connect another tube to, and is also sometimes referred to as a 3 port bleed valve.

There's a school of thought that says brass is better than aluminium as it has a lower coefficient of thermal expansion, and thus the rate of bleed will stay constant regardless of temp, whereas with an ally one expansion might alter the internal gap and thus rate of bleed.

I'd go for a 3 port brass bleed valve/MBC myself.

HTH
 

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But are you choosing MBC because your cars dosnt have Trionic enginemanagement? I still havent upgraded my 97´9000 2,0 LPT as I am 90% happy with the engine as it is now except for standstill acceleration! Could a two stage MBC be the answer for my needs? That way I could keep the engine standard except when I what a quick start??
 

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I still get surprised when I read threads like this!!!

Why spend lots of money on a car with one of the best engine management systems on the market and then not let it do its job? MBC is a "tuning tool" from the 80's - why use it 2003?

Isn't the facts about melted pistons enough...

Wait until you have the money to get an upgraded ECU instead!
 

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Fair comment, Friberg, and it's never something I have recommended as a wholly reliable route for tuning.

The APC system provides valuable safeguards and you cna be surew that it will have been over-engineered for safety. Thus if you are prepared to take a small risk, there are modest increases in performance (circa 10% or less) that can be had from "playing" with the OEM setup.

Thre fact that a significant number of Saabs do happily run with this sort of setup is testament to the validity of this approach.

However, if you wish to seek a significant increase in performance then you should utilise a revised ECU mapping.
 

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Thxs for putting me in place Frieberg!!!!!!

I am just a ignorant fool, think how bad things could be if I didnt have wise guys like you to corret me!!!!!!!!!!!!

I just whant to be shure that I am doing the right thing before I spend 7000 Sek with Maptun
 

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The thing is that it's only on english-speaking forums I read about MBC... As soon as a newbie asks a question about that on Swedish forums they get this kind of reply all the time!

>>Sören
I guess that you can read Swedish quite well even if you maybe can't understand when we speak. Check out www.stcs.nu - there are a few danish guys there already
 

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Thxs Friberg,

yes I do already follow www.stcs.nu and its quite interesting! And yes I know that just the thougt of a MBC will make the swedes go ballistic, thats why I used this forum to check the concept.

Søren
 
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