My original plastic diverter valve broke, so I ended up picking up a Turbo-XS type H-34 diverter valve to replace it. When I first put it in the car I had to add a bunch of shims to try and keep it from stalling out the car when shifting or coming to a stop. Only problem with adding the shims was now I have bad compressor surge at part throttle which causes the car to "stutter" in time with the surge. Yesterday I took the shims out to drop it down to 1 shim and the spring, fixed the stutter and surge issue, but now it acts like I'm running a vta setup. My afr's dip down to around 10.2:1 and it stumbles for a few seconds then catches itself and starts heading back toward the 14.7 mark. Does anyone have any tips on where on the fuel/timing map I could tweak to help speed up the recovery?

 

Why dont you just run a IX bov??

 

+1

i picked one up in the for sale section for $50. the deals are out there

 

I have a stock VIII D.V. if you really need one. $40 shipped.

 

I would've if I could have gotten one at the time, and gotten it fast. I've been playing around with the timing a little bit back in the low load areas, and it seems to have helped a little. Also, another thing I noticed...I had forgotten to change the low octane maps to match the high octane ones, and the valve has a tendency when it blows off to trigger my knock cel (registers like 3 counts exactly when it pops off), so I have a feeling the ecu was pulling timing and adding fuel right at the moment after the valve let off, and created the bogging down situation. I just reflashed the ecu with both sets of maps set almost identical (I left the extreme load points a few degrees less timing and a hair more fuel just in case) and the car runs 100 times better and seems more responsive. I still have to go over my logs to see what load I'm hitting and timing and afr, but so far so good.

 

Wait, so you're running it back into the intake, not VTA, and your having this problem?

 

Exactly. It's smoothed out quite a bit now since before after playing with the maps, but it still has a slight bit of stumble and my afr's drop to around 10.8:1 where it'll catch itself quickly and shoot them back up to high 13's pretty quickly. I'm also wondering if using the narrow band output off my lc-1 might help it recover faster due to having a "true" afr signal.

 

so your high and low oct maps are the same?

 

unless you have done something with your narrow band o2 sensors using the wideband for narrow band simulation isn't necessary.

its unlikely the recirc diverter is impacting your afr.

I'd suggest a shop look at the car or log what is happening. Maybe you installed something else recently too?


check your short term trims, you may be out of wack on your latencies.