Hey everyone, I am a long time reader of this forum (lot of good info!) but posting for the first time as I am a little confused by my car currently.
I have a 1989 325i that I turbocharged myself last year and last summer all was well, made about 280whp at 13 psi for most of the summer.
This winter I oringed the block, changed the HG (Elring), and put in a 284/280 (Ireland Engineering) cam as I want to get closer to the 400whp mark. After putting it all back together, firing it up, and making some Megasquirt tuning changes for the new cam, I feel like the car has a misfire at idle around 8-900rpm. It does not have a completely clean lumpy idle like I would expect, seems like it misses here and there. I do not notice this past like 1200 rpm or so and there is no hesitation to rev or anything else weird. I decided to do a compression test after checking the spark plugs, wires, distributor etc. and finding nothing. I got about 9 bar of pressure on cylinders 1,2,4,5,6 and 11 bar on cylinder 3.....I know the factory spec is 10-11 bar and it had prefect compression on all cylinders at the beginning of winter before it all came apart. I am assuming the lower compression result now is due to my longer duration cam but why do I have such a different and high number in cylinder 3? I checked my cam timing and it was correct. Could the difference in compression be related to the misfire I think I am hearing? Any idea what the correct compression test pressure should be with a 284/280 cam and why there is such a difference with 1 cylinder?
I have not taken the car for a drive yet this year, just idling in the driveway really because I am trying to understand what is going on.
I have a 1989 325i that I turbocharged myself last year and last summer all was well, made about 280whp at 13 psi for most of the summer.
This winter I oringed the block, changed the HG (Elring), and put in a 284/280 (Ireland Engineering) cam as I want to get closer to the 400whp mark. After putting it all back together, firing it up, and making some Megasquirt tuning changes for the new cam, I feel like the car has a misfire at idle around 8-900rpm. It does not have a completely clean lumpy idle like I would expect, seems like it misses here and there. I do not notice this past like 1200 rpm or so and there is no hesitation to rev or anything else weird. I decided to do a compression test after checking the spark plugs, wires, distributor etc. and finding nothing. I got about 9 bar of pressure on cylinders 1,2,4,5,6 and 11 bar on cylinder 3.....I know the factory spec is 10-11 bar and it had prefect compression on all cylinders at the beginning of winter before it all came apart. I am assuming the lower compression result now is due to my longer duration cam but why do I have such a different and high number in cylinder 3? I checked my cam timing and it was correct. Could the difference in compression be related to the misfire I think I am hearing? Any idea what the correct compression test pressure should be with a 284/280 cam and why there is such a difference with 1 cylinder?
I have not taken the car for a drive yet this year, just idling in the driveway really because I am trying to understand what is going on.
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