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Discussion Starter · #1 ·
I though I would have a little fiddle, not that my car was feeling slow but, when the option of being able to adjust the boost control, it would be considered rude not too.

So I did.......


The car felt very different, once we got over seeing the boost gauge flicking off through the red (very exciting-lots of girly giggling) the car felt more laggey than normal, but the boost was certainly higher and lasted longer through the rev range (the car being a 2.3 FPT rather than an aero).

We then pulled over to stop and adjust further, but upon opening the bonnet part of the turbo was glowing red, at this point I was scared so adjusted the MBC back to its previous setting.
I have heard that it is not rare to see the turbo glowing when driven hard, but being relatively new to saabing caution plays a strong part.

So the question is -
1- Is the performance increase worth it, in respect of extra lag?

2- Should I expect the turbo to be glowing after spirted driving?

3-Any ideas as to what psi increase I would get per turn?? will be nicking my mates boost gauge.

4-What psi are other people running?

Cheers Dulux
 

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Adjusting the MBC will not result in any increased lag to reach the same pressure as before; it will just increase the max boost pressure, which will take longer to reach.

Proceed with caution though- without the software (do you have standard or upgraded software?) specifically mapped to cope with the extra boost, you run the risk of running too lean. /john's pic is in extreme circumstances of running WOT under max load. In your case I would say that the glow is a possible indication of your EGT being too high. Even if you are not suffering from knock/det (remember the APC is disabled) then having too high an EGT will place a stress on many components.
 

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my turbo glows quite a bit.... and from what i have read.. it is quite normal. it glowed at stock 11.5psi, and glows about the same at 16psi. i still have APC on my car.
 

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I was flicking through a car mag (forget which) in the local newsagent recently, and there was an article on AMG that showed them testing one of their engines (V12 turbo?). The whole manifold, turbo and downpipe were glowing bright orange, almost yellow!
 

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Discussion Starter · #8 ·
I must admit the glowing is just something I have never seen before, so just a little concerned.

But is there going to be a marked improvement in power by adjusting the MBC, surely higher psi= more power?????

Dulux
 

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My turbo, manifold and exhaust look similar to /john's when on the dyno. That is probably because my 9-3 is very similarily modded as his. Hirsch said that my car runs about 925C max during the dyno runs, which is considered about the max safe level for a street tuned car. There is no reason to say that a glowing turbo and exhaust means that the EGT's are too high. Due to differences in turbine housings and materials of the turbo and pipes, some will glow more than others. Maarten's TD04 equipped GM900 does not glow nearly as much as my 9-3 since the turbine section is much larger and he has no cat to be putting back pressure on the exhaust flow. This does not mean his EGTs are any lower though. As with comments from others I would have to respectfully disagree with Mark E that the glow may be an indicator that EGTs are too high. He is correct though that you should tune the MBC with the proper equipment to monitor what is going on with the air/fule ratio and such. The only way to check this stuff is to have the car dynoed with a wide band O2 sensor checking things out. Getting your hands on a good boost gauge will help out as well.

I too did not like the feel of the way boost came on with a mbc in my car. It did seem to be somewhat delayed to start moving upward compared to the APC system, however once it started going, boost would shoot up quite quickly.

Anyways, an mbc can be a cheap way to extra hp but you need to be careful using it to not run lean as mentioned. I do feel though, that a proper software upgrade is the best way to better performance. As for more pressure=more hp, that is true to a point but if you try to run too much pressure, the backpressure from the turbine will overcome the boost going in and therefore the cylinders will backfill with exhaust causing extreme EGTs and lower power levels due to less intake air getting in.

Well, those are my thoughts, I hope it helps a bit.
 
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