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Hello,
I'm currently helping a friend tune his ITB miata, the engine setup is the following :
- mild cams http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=233&CAMSETUP_id=969
- 11:1 comp ratio
- 4AGE ITBs
- MS2 ECU
Somehow, I can't get the car to idle at a low RPM with the stock timing (10 - 14°), it keeps climbing to 2.000 RPM.
If I lower this value to 0°, the car purrs at around 1.000 RPM.
Is this a normal behavior ?
No that's not normal behaviour. It sounds to me like you have too much air bypassing the itb's when the throttle is closed and this is resulting in the high idle speed. You're then artificially fixing this by retarding the timing whihc reduces engine torque and hence idle speed. I'd start by making sure there are no vacuum leaks anywhere in the intake system post throttle plate. If there are no leaks, ensure that the throttles are closing completely. There are adjusters on the 4AGE itb's for this purpose, however if they are still in their stock location they normally don't require adjustment.
Hi
It was my thinking too, the vaccuum value is pretty low (but that may be a combination of TB leak & mild cams).
We'll investigate tuning the TB position.
Thank you.
