After dyno'ing the car this past weekend and finding out that, somehow, adding a 52mm throttle body has caused my a/f ratio to drop from 11.7 down to 10.4 and/or lower at times - i'd like to put together a checklist to track down possible causes.

So far i've read that:

1) Leaks before the 02's
2) Possible restriction at my blower inlet?
3) Bad 02's - not used in WOT tho correct?
4) Vaccuum leaks


I'm sure that there are more but those are what i've found quickly using Search.

I have a small leak at the back of the intake manifold (THE dreaded oil leak) which I fixed 2 years ago. It's an easy fix, but, could this cause an issue with my A/F dropping so much?

Maybe we can talk someone into "sticky'ing" a Rich/Lean checklist - I think it would be beneficial to the board.

Anyone have more to add to the checklist?

Thanks

 

Somehow I don't think a generic "rich/lean" stickie list is necessarily going to solve the problems on a 120mph blower setup.

How is the extra fuel added for the blower..... PCM programming, FMU, boost referenced FPR????? Where is your MAF located? Is there any chance you are losing air somewhere between the MAF and the intake manifold? Is your boost as high as it was before the TB install? If you have a leak in the blower system, after the MAF sensor, and you are using PCM tuning to add the extra fuel, its going to run rich. Since you changed the TB, is there any chance you've got an air leak?

 

has the car been tuned since the new tb install?

 

Fred - the fuel is being added via PCM programming. The MAF was located down below on the intake pipe but after examining it - I found that the MAF is coated in oil. My setup is: Valve cover is vented via 1/2" hose to an oil catch can down to the intake tube on the blower after the MAF, but when the car is shut off the excess oil rolls down the tube onto the MAF - could this cause a problem with the MAF reading AFGS? I'm thinking so - but i'm also going to look into some other possible leaks before I head to the dyno.

I'm in the process of moving the MAF back up top to make it a blow thru. This should help with the oil coating.

Now that you mention a leak beyond the MAF - what about the valve cover venting that I have? Also, the bypass valve is vented back into the hard intake pipe past the MAF as well. I was under the impression that this is how it had to be ran because the air had already been metered once and would not have to pass thru the MAF again?

Sounds like I don't have this configuration setup correctly still. I've had the blower for about 6 months now and it's my first so i'm still learning a lot of stuff here.

Should I vent the valve cover to atmosphere?

 

Forgive my artistic flaws but this is the best that I could do right now.

 

A coated MAF sensor will cause the sensor to read less than actual flow, and that would make it run leaner, not rich.

I'm no S/C expert, but your crankcase vent system looks backwards, and inviting high oil carryover. Normally, the blower cars I have seen put a breather on the valve cover, and connect the PCV vacuum source to the blower inlet duct rather than the stock location on the drivers side of the intake manifold (93-94) or under the throttle body (95-97). You would put the oil separator in the line gonig from the PCV valve to the blower inlet duct.

What did you do with the port on the side of the TB that connected to the line to the valve cover?

 

That line is blocked off

So it looks like the entire evac is backwards? I'll try it the way you say and see what happens. Still not sure about the rich condition tho - unless the evac being pumped back into the engine is causing it?

Thanks for the help Fred

 

Fred, my PCV valve consists of a "U" hose the valve in the forward most hole - is this correct? And, you're saying to take a line from the vaccuum side (side without the valve??) and run that down to my SC inlet? What about the other end of the PCV that would now be open?

I'm sorry if I am misunderstanding you on this - but your help, or anyone else running a SC is greatly appreciated.