Date: Fri, 02 Oct 1998 15:57:13 +0100 From: johnnopsam16.co.uk (John) Subject: Re: Looking for 8V intercooler kit
Thanks for the comments rob - no offence taken - I'm new to news groups and am enjoying throwing in comments and ideas and having them challenged or aggreed with , my suggestion that the intercooler on the saab is more for economy than performance was probably a bit cynical and based on the fact that the 900 intercooler is not very efficient and basicaly not as good as it should or could have been unlike the 9000 one. Some more thoughts; The Saab turbo charging project was always geared to economy and drivability in everyday situations ie mid range torque, to this end they have progresivley increased the compression ratio of their turbo's to give better pick up response and better fuel economy. Increasing the compression ratio on a turbo is no good if you want to pile on the boost and go realy fast it just makes the engine more knock prone. I had an 8v with apc but with the 7.2:1 compression engine, the boost would go easily into the middle of the red and stay there - it was very fast and fierce but sluggish round town and very heavy on fuel even if I did not thrash it. When Saab rallyed the 99 they had 6.5:1 compression which allowed them to get 1.6 lb of boost giving 240bhp at 5700rpm it must have been fast but not much fun to drive off boost. So if you want more power out of a turbo engine with a 8.5:1 compression ratio you have to massivly cool the charge to stop detonation ie a huge and efficient intercooler and or water injection. You can reduce knock by retarding the ignition but this causes the engine to run hotter kind of defeating the object, pumping in more fuel on boost cools the charge slightly but it also reduces the flame speed in the combustion - reducing the power as well as using loads of fuel. I hope this makes some sense of things but I am still sure you will be dissapointed if you fit the standard 900 intercooler its just not good enough - go on make some mods to the front of the car and squeeze in that 9000 cooler!. Cheers John (I am just going outside to bypass mine with the direct pipe from my first 900)
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