JDM Turbo Conversion Do I need BAC and why is it different? Running REALLY RICH!
 

I have done a complete S5 NA to JDM turbo conversion. The car is running and idling beautifully but it is idleing VERY VERY rich. No vacumm leaks, timing set, tps reading ok and set. Injectors were tested aftermarket fpr with stock TII fuel pump. How do I lean this thing out? It is the last item on the list.

Does the BAC effect this rich adjustment? ON the JDM BAC, there is no mixture screw and only one pipe coming out of it to feed the the intake pipe.

What is your base fuel pressure with no vacuum applied? Stock is 36psi

also, here's a question: I've never looked at a JDM throttlebody. Is there some kind of idle adjuster screw on there somewhere? This is a screw that controls air bypassing the throttle plates, same as the USDM BAC valve screw or the screw on top of n/a manifolds. The FD has the idle adjuster screw on the TB itself.

There is no idle adjust screw on the JDM BAC or anywhere else. You can only control the idle speed with a screw on the TB but not the mixture. I have the base fuel pressure cranked down to 20 PSI at idle. I thought this might be causing a rich condition, but it should not at that pressure.

when you say very very rich, what are we talking about here as measured on a wideband? also, is your water temperature sensor ok? sometimes when they go bad the computer will think the engine is always cold and put in extra fuel.

are you sure you are using stock 550cc primary injectors?

there should be an adjustment screw on the passengerside shock tower that will adjust the mixture. its usally covered so u have to break the seal to get to it. someone correct me if im wrong as this is off the top of my head

On the rich side I mean at idle it is smoking horribly and smells like raw fuel coming out of the exhaust. I dont think there is anything on the shock tower. Does anyone have an S5 Turbo TB unmodified that they want to sell. I did this modification and I am thinking I want to go back to stock with the thermo wax and throttle plates. It seems the more that is done to go away from stock, the worse the engine behaves. I really want to finally drive the car without smoke pouring out the back smelling like raw fuel.

You're speaking of the "variable resistor" which is a component found on S4 engines "only."

Theres no adjustment screw on a JDM... Never has been

ahh didnt realize it was only on the s4's. i thought they came on both s4's and s5's

not to thread jack but mines running extremely rich, exact same situation as yours, jdm engine, no way to fix it? any insight would help both of us,

Tossing my hat into the ring. I have a JDM swapped s5 which also developed fuel smell, running rich and then poor idle. My engine and situation may not be related to the thread. I paid a shop to do the swap for me and for a couple years the engine ran great, no fuel smell or rich running.

Part of my fuel smell I found was a fuel line I replaced when upgrading the pump and injectors. I know it's simplistic, but check your fuel lines for leaks, I thought I checked all of them.

As Arghx suggested I'm very suspicious of my electrical system and/or sensors. I'd check what he suggested. Around the same time I developed fuel problems and running rich I also replaced my used FD alt with a reman'd one. My OEM volt meter became very sporadic, most times barely showing above 12v. To toss another question mark and muddy up possibilities even more, I'm suspicious of my engine harness as well as my battery/starter harness. As I've been testing sensors I've found my harness dry and cracking, sometimes exposing the copper thru the insulation.

ok my assumption is also turned to the water thermostat because it makes sence for the most part, with it getting to much gas cause its reading cold.

any pics of the idle adjustment on the jdm

There is no idle adjustment on jdm....read above

did you fix your problem