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i just researched this to understand it myself Posted by Saabu [Email] ![]() ![]() In Reply to: 900s 2.1 head and 85 exhaust cams, 900 aero jet, Tue, 12 Jun 2007 16:11:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
and posted not long ago ie within the last 2 weeks so check out those posts. below i'm assuming using said exhaust cam and 86+ NA intake cam.
I"m no expert, this is just my 2 am take on things.
also you may want to go to how stuff works - some good basic writeups there.
I think the 85 cam was done in order to reduce exhaust emissions. The 85-86 head is known for its bad intake cam (from a performance point of view) which reduced intake, power and thus emissions.
basically, the 85 cam opens 5 degrees later and closes 3 degrees later than the 86+ ex. cams. this results in a longer power stroke and more exhaust gas venting.
it nets out to 2 degrees more duration (time the cam is opening the exhaust valves) which isnt a lot.
however, since the openging time is shifted later, the other effect is that the time the exhaust valves are open is now overlapping 3 degrees more with the time the intake valves are open (29 degrees vs 32). this will result in more scavenging (venting) of exhaust gases as the pressure of the turbo pushes the fresh intake air in.
any other take on this would be welcome. i just found these cams at the yard myself and installed them on a 2.1 head upgrade im doing on an SPG block that needed a head gasket anyway. bigger injectors, a larger turbo and better ECU fueling are all in the plans.
Wayne in Calgary
posted by 75.153.24...
_______________________________________ 1988 900 TC 2000 Viggen 1997 900 TC son has 2002 9-3 SET
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