Vacuum advance idle transition
I've got everything running well. Got the vacuum advance working and it helped the temperature 10 degrees at least. I think it is still relearning from that, but I would like to improve the idle transition.
It starts well cold and hot. Idle vacuum was around 7 at 850 before hooking up the vacuum. Now with the vacuum connected it wants to idle at 1,000, vacuum approx. 12. The MSD RTR canister starts pulling at about 11 and is all in at 15 with 10 degrees advance.
Besides the higher idle, I get a flair at start to about 1500-1700 then it settles back to 1000. Also sometimes pulling it into gear it drops to about 500 for a couple of seconds. Only once has it died though. IAC warm idle is 0-4. I've tried closing them down to raise, but that seems to cause other issues, starting, etc.
I think this is all caused by the transition from mechanical advance only at below 1000 rpm, to vacuum advance coming on. Once it is past 1000 all is good. Crisp and responsive. Any ideas to tweak?
Ray, are you using ported or manifold vacuum for the advance...should be manifold. Is the ECU controlling any part of the timing or is all the advance using weights/springs for mechanical along with the vacuum canister? Also, there should not be any mechanical advance below 1000 rpms, it should start about there, or a little higher and normally be all in by 2300-3000 depending on weight of vehicle, gears, trans and of course all the engine variables. At idle you don't want either the mechanical or vacuum advance changing the timing (unless ECU is controlling, but that's a different story). You need to get a vacuum canister that is all in at idle using manifold vacuum. I've attached a document that discusses all of this...hope you have a Chevy! Good luck!
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Hugger, thanks for the reply. No SBC. I've got a stroked B block Mopar. I'll read the article though. Maybe something in there that will help.
Yes I am using manifold vacuum. Fitech is not controlling any timing. It isn't compatible with my RTR distributor. Correct there is no mechanical below 1000. It is springed to be all in at about 2800. MSD tech told me the canister on the RTR starts pulling at 11 and is all in with 10 degrees at 15 vacuum.
I may be wrong but I'm thinking what is happening is due to the the advance starting to come in. It could be I need to keep working with the IAC. Or in Pro Tuning, Idle Control, Open IAC setting? Or Loop Rate settings?
I was hoping I would find someone that worked through this before.
Quote from ray230 on July 20, 2019, 7:36 pmHugger, thanks for the reply. No SBC. I've got a stroked B block Mopar. I'll read the article though. Maybe something in there that will help.
Yes I am using manifold vacuum. Fitech is not controlling any timing. It isn't compatible with my RTR distributor. Correct there is no mechanical below 1000. It is springed to be all in at about 2800. MSD tech told me the canister on the RTR starts pulling at 11 and is all in with 10 degrees at 15 vacuum.
I may be wrong but I'm thinking what is happening is due to the the advance starting to come in. It could be I need to keep working with the IAC. Or in Pro Tuning, Idle Control, Open IAC setting? Or Loop Rate settings?
I was hoping I would find someone that worked through this before.
Ray, if your distributor setup works with a carb, then no changes need to be made to the Fitech to work. If using manifold instead of ported vacuum, then of course your vacuum advance is coming in during idle.
Am I missing something?
I wasn't using the vacuum advance with the carb. So I don't know, but it would have probably had the same issue.
I started looking into using it with Fitech because it was running hotter with better AFRs. That really helped temps and runs good everywhere but idle transition.
Ray, did you ever get this working?