SPERRYsan

iTrader: (1)

my 12a with s4 turbo,12lb tweakit flywheel,autonomics 1000cfm tb with 460 cfm inserts, and four 52lb injectors running at 20psi
it idles yet i get this wierd poping/shudder noise that slowly develops
i know it is not from the fuel mixture at idle because ive tried every variation to that
and my ignition timing is set right on the marks
im wondering if 800 is a bit low for my ilde speed with my 12lb flywheel on there
any turbo guys or megasquirt guys got ideas?
i will post sound clips later today
and also my ms files

muythaibxr

the light flywheel will make it harder to get a smooth idle...

Generally I get a good idle with around 12:1 AFR and between -5 and 3 deg ignition advance.

turbosa22c

Popping Out Of The Intakeside, Your Lean. Out The Exhaust Your Rich. Ive Also Heard Bad Seals Pop Out Of The Intake

renns

Your symptoms sound like the idle fuel is collecting on the runners of the intake, and dribbling into the combustion chamber. This can happen if the injectors are mounted back from the ports and squirt into runners that have little airflow. If squirting directly at the runner wall, the problem will worsen. The result will be an initially smooth idle, but quickly transitioning to rough running if left at idle for any extended period. By revving the engine, and 'clearing its throat' to burn off the excess unmixed fuel in the runner, you can then return to idle for another few seconds.

If this sounds like your situation, then here's some options:

1.) Add progressive throttle body linkage that completely closes the secondary runners at idle, and allows primary throttle motion only for the first 1/3 or so of pedal travel. This is similar to the oem scheme. Be sure to use the staged injection option in MSnSExtra, and set for TPS-based transition at a point well after secondaries open. This ensures you only squirt fuel into the active runners when airflow is low. This page shows how to rig the Autonomics for progressive action:
http://www.mez.co.uk/turbo9.html

2.) If progressive throttle linkage is difficult with your setup, try to at least adjust the mechanism to close the secondaries first, so idle air flows through the primary throttle plates only. Code setup as above.

3.) If any fast-idle or closed-loop idle air circuit is used, that will reduce the airflow through the throttle plates at a given idle speed, and worsen the symptoms.

4.) Add diffusers under the injectors similar to what Mazda uses to aid in low-speed fuel mixing.

5.) Increase idle speed. Obviously this has its limits, but you'll likely see an improvement with increasing idle speed. It may not be ideal, but if it improves drivability while you search out other solutions, it's worth a shot.

Hope that helps.

Terrh

iTrader: (7)

your fuel pressure sounds (to me) like it's too low. Most OEM fuel injection systems use 37-45PSI, the injectors may not function correctly at only 20PSI.

SPERRYsan

iTrader: (1)

thank you for all you information that will give me a good start on this
i will post any more information i can
fuel pressure for tbi setups should be alot lower than multiport shouldnt they
i dont see why higher pressure would be bad considering the injectors are designed for it.

Another isssue that ahas come up is that my oxygen sensor is not working
I have bought two new bosch oxygen sensors and the readings never even budge in megatune
the ground to the engine is good and the continuity to the relay board is also good
the oxygen sensor is mounted at the collector right before the turbo so there is plenty of heat for readings

would a 2 or 3 wire maybe work better?

autopaul

as far as i know 3 wire is good for initial startup as it has a heating element inside it, but once your car warms up there shouldn't be much difference.. it could be a bit off since the heating element will also keep it a constant temperature..

Paul

2713ddddavid

iTrader: (1)

I thought the sensor should be mounted AFTER the turbo. My Bosch wideband sensor (Inovate LC1) says to mount it where it will not see more than 900 degrees f.

muythaibxr

david: Narrowband sensors require a lot of heat to work. Widebands are damaged by a lot of heat. He is correct to mount his narrowband before the turbo.

However, I have no idea why you're not seeing a reading unless the input circuitry is not working.

I would suggest putting the MS on the stim and making sure that when you turn the O2 pot, the O2 gauge in MT moves.

If it does, then you know the problem is likely to be wiring.