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I have recently upgraded my 9-5 2.3lpt using a BSR update, Initially I was getting a severe hesitation which the guys at BSR said was my di Cassette. I have now replaced that and it has made a tremendous difference. I now however during hard acceleration the engine seems to be holding back slightly, if I lift the throttle pedal a little the engine then seems to accelerate briskly again.

Any Ideas?
 

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Originally posted by DWGriffith:
[qb] if I lift the throttle pedal a little the engine then seems to accelerate briskly again.

Any Ideas?

   [/qb][/b]
Sounds like my Aero, I think I have minimised the effect with good plugs and good fuel, but mostly I guess I've just got used to it after nearly two years of lifting off from full throttle for maximum


If you get an answer, I'd love to hear it, please?
 

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I only have a vague knowledge of this and little hands on experience. But is this a symptom of overfuelling?

I believe that some tuners set the system up to add excess fuel (which won't be burnt) at high load to cool the system. So at full throttle the air fuel mix will not be optimum. Lifting off will reduce the fuel and allow a little more air in at optimum air/fuel ratio so power increases.

I think it's related to reducing exhaust gas temperatures. Also the consequences of a lean mix with too much air at high temp could cause the metal to burn away!!
 

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engines are set on the slightly rich side mixture on wot open-loop state.
Hence the advantage if you can tune on roll road, then you can get closest to ideal mix = max power .
Either way, its something you should look into immediately as overfuelling is not good for cylinders.
It could also be a lack of air - choked air filter or other air intake blockage ?
 

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Hmmm funny this subject should arrise... I have just fitted a stage 1 bsr upgrade on my 2.0 9-5... have the smell of fuel every now and again too.

Im going to ask bsr if this is expected or not...
to get a definite answer.

Cheers
Michael
 

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Stock T7 Saabs run very rich towards top end to keep the combustion surfaces cool.

I'd wager it's a "glitch" in the software. T7 never runs at "full throttle" even when you push the pedal down all the way.

When you push the pedal down suddenly it will open the throttle quickly to get good spool up, but then close the throttle as boost comes on to attain the "ideal" boost value it wants.

It's very complicated and I could see a "glitch" forming quite easily. If I lived closer I'd offer to log your ECU to see what the throttle and boost are doing, but I'm on the other side of the pond in Southern California so.

For what it's worth, this is a data-log from my stock 9-3 Viggen ... the pink is throttle angle in percent, and the blue is manifold absolute pressure in inches of mercury:



Dubbya~
 
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