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-   -   RX8 injector idle woes (https://www.miataturbo.net/megasquirt-18/rx8-injector-idle-woes-105550/)

JohnnyHess86 07-14-2021 12:24 PM

RX8 injector idle woes
 
1 Attachment(s)
Good morning all,

I have been having issues getting my 99 with RX8 injectors to idle anywhere below 1200-1300rpm. Yes, they are REAL RX8 injectors. I had a bad enough experience with the knock-off units that flowed slower than piss through an erection.
Anyway, I cannot seem to get the engine to idle at 850 or even 900 when warm. It always wants to be around 1200-1300, regardless of my CLI settings.
There is an exception. If I turn the fuel way up in my VE table's idle cells, it will go down to 900. However, my AFRs wind up in the 11s, and I'd rather not foul out plugs due to excessive fueling. My injector dead time is set at 1.1ms right now. What sort of correlation might these two things have?
Is this sort of high idle just a fact of life with RX8 injectors on these 1.8 motors? Or is there something (or perhaps many things) I am missing? I've read on some forum posts that it is, and yet other folks seem to have dialed them in for a "smooth as stock" idle.

Current tune attached. Thanks in advance for any and all advice.

andym 07-14-2021 02:29 PM

Have you adjusted the throttle body screw to open / close the bleeder valve for Idle? You might need to mechanically tighten the screw more to let less air bleed past the throttle body.

JohnnyHess86 07-14-2021 02:59 PM

Just smacked my forehead because it's the ONE thing I hadn't yet considered doing.

Just went outside and tried this. Sure enough, with about half to 3/4 of a turn, the idle settled right down to 900. I'd heard of people doing this but was advised against it. Is there any real disadvantage to adjusting the idle screw?

andym 07-14-2021 04:14 PM


Originally Posted by JohnnyHess86 (Post 1604366)
Just smacked my forehead because it's the ONE thing I hadn't yet considered doing.

Just went outside and tried this. Sure enough, with about half to 3/4 of a turn, the idle settled right down to 900. I'd heard of people doing this but was advised against it. Is there any real disadvantage to adjusting the idle screw?

My procedure, and I don't know if it is necessarily correct, has been to disconnect the IACV and adjust the throttle body screw to 50 rpm below my target idle rpm. Then reconnect the IACV and start tuning the closed loop idle initial values to the new parameters and also readjust the idle duty valve settings for min and max if they have changed.

Some people prefer to do what I outlined above but they set the rpm via throttle body equal to target rpm.


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