What should my air/fuel be at idle
07-20-09, 09:42 PM
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What should my air/fuel be at idle
Ok ive tried to search for this but i am just not getting the answer I need. I have a brand new engine done by atkins rotary. I have 600 miles on it. I have removed all emmisions and have a catless exaust. The car runs very good but im sitting at 12.6 when warm. Is this normal or should i be closer to stoch. When I am driving I have noticed under wide open throttle I am seeing low 11s to upper 10s. I do not want to cause any damage to this engine. I have also not been able to make a pull more than 4500 or so as the engine still needs another 500 miles or so to break in. Any input would be greatly appreciated.
07-21-09, 12:05 AM
#2
at idle it should be around 14.5 on up to 17:1 air to fuel ratio. you can run richer down to 12.5:1 or even in the 11's but it's not necessary to be that rich unless the engine has **** poor compression in which case it will need more fuel to idle smoothly.
you could simply have some vacuum leaks or need to adjust your variable resistor.
11:1 at WoT is normal.
you could simply have some vacuum leaks or need to adjust your variable resistor.
11:1 at WoT is normal.
07-21-09, 12:10 AM
#3
Actually, your idle should be smoothest when around 12-13 AFR, so you are experiencing normal idle. This is coming from a question I posted before and answered by a good member here. The engine of course is going to be running rich at WOT, especially if this is an NA. It's safe, you need to worry if that number starts to go high which is lean.
07-21-09, 11:22 AM
#6
already said what i have to say, take it or leave it. it's ok, i guess i have been gone a while.. S4 TIIs are the lowest compression of all rotary engines so keep that in mind also, since it was never mentioned so you may have to be in the 12.5-13:1 area for a smooth idle, with a high mileage worn engine possibly as low as 11:1 AFR if compression is getting into the 70's.
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07-22-09, 01:11 PM
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This topic is a bit confusing to me. Karak knows what he is doing so I don't understand the suggestion that a rotary can idle from 14.7 to 17:1. In all the years I have been doing this (10) I have never seen a rotary that will idle well in the 14s. After about 13.5 they become unstable and closer to 14 the idle wants to wander, requiring a lot of idle valve to keep it steady. At around 14, any additional load (like an e-fan) will cause the idle to drop like a stone. I can't imagine idling leaner then that, so 15, 16 or 17:1 sounds very odd to me.
The best idle ratio is as lean as you can go without the idle wandering around or becoming unstable when the engine sees a bit of load. In my experience, this is around 13.5:1 if you have an idle valve, and high 12s if you don't.
As always with tuning, your mileage may vary.
The best idle ratio is as lean as you can go without the idle wandering around or becoming unstable when the engine sees a bit of load. In my experience, this is around 13.5:1 if you have an idle valve, and high 12s if you don't.
As always with tuning, your mileage may vary.
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