Way Low BLMs - 95-105 at cruise?

[subtlt]

Looking for confirmation on this one. Seems like it's leaning the mixture to compensate for too much fuel at cruise. Ran the T-link on the way to work this am (thanks Ken!), and noted that at 55-60 mph, BLMs were in the 105 range. I'm running a Jay Carters 93 chip for stock injectors. Very mild mods (combo in sig).

At 3-4V TPS, I'm getting 850mv O2 figures, which supports the rich BLM compensation if I understand correctly.

IAC numbers are a bit low (6-8) and TPS is at .48 idle. I'll tweak those first, then run again, then maybe drop the FP and see if I can get it in spec.

Just to confirm, am I looking for 128 BLM under ALL closed loop conditions?

 

[WarpSpeed]

Yeap, Ideally 128, however, that's like a dream come true. I'd set the TPS to .45 idle, car running,, first. Then maybe turn the fuel pressure down a tad. It's unlikely you'll get a perfect 128 at any load(LV) except for WOT. BLMs will even change with weather.

 

[Russ Merritt]

The car runs great though right? don't sweat blms, unless they're maxed out one way or another indicating a problem.

 

[NCTURBOS]

MAF Screens

How many screens are in your MAF? If both are still in there try removing one. That should clean up those BLM's.

 

[750H.P.V6]

Wayne,

Based on the BLM's you've stated there are 2 possible causes. The first is something you have control over and the other you don't. The easiest way to bring the BLM's up is to lower the fuel pressure. The second way is to have Jay change the injector constant in the chip you're running.

BLM's at cruise on flat ground should be somewhere around 128 but BLM's either going up hill or down hill will vary depending on load. It's not uncommon to see low BLM's on a decel prior to Decel fuel cut off (no fuel flow) and high BLM's in an instance where you load is increasing but you aren't in P/E yet.

Basically what I'm trying to get across is that BLM's won't be at 128 all the time although your cruise #'s sound low. How much fuel pressure are you running?

Neal

 

[subtlt]

getting better, but still not there

On the cruise in this am, the BLMs moved to the 105-110 range. Better, but still not there? I had the injectors cleaned on the Sun motorvac system on Saturday, and that solved a host of slight missing/hesitation problems, so I'm sure I'm getting full fuel flow.

I do have the DS header crack (very slight) which I'll be fixing shortly, perhaps that could cause the problem? My (limited) understanding is that it would have the opposite effect - high BLMs.

Last night I reset the IAC (was at 0 ) to 20, and the TPS at .42 Tweaked the fuel pressure down to 41 line off. Ran a couple of quick 0-70 blasts, no knock, upped the boost 1.5 psi, 0.5 knock at the 2-3 shift and 815MV O2. I'd be happy if it wasn't for the fact that this brings me to a whopping 13.5 psi per my westach gauge...

Obviously, I have some other gremlins to exorcise

To get the wastegate arm on the flapper I have to yank the thing out a good 1/4-3/8". Seems too far away compared to my last car. I'm wondering if maybe my cat is plugged?

 

[NC87GN]

What are BLM's @ WOT? Changing injector constant will help but there is a downside. If your running 128 @ WOT (perfect), and you do not have BLM lock, your WOT BLM's will change as a result of changing the injector constant. If your gonna change the chip to get the BLM's up then go into the fuel trim table to do it. If a header leak is apparent usually BLM's will read on the high side. Try to set the IAC above 10 but not over 50 at idle and pay close attention to MAF constant (keep between 5-6). HTH

Mike Banas

 

[750H.P.V6]

Mike,

Like you stated changing the injector constant in the chip will act as a blanket change across the board. I'm confused about your suggestion to change the BLM's by changing the fuel trim table. Which table is that? I think you might be talking about the P/E trim tables but then again this has no impact on the BLM's.

Based on the low BLM's stated above I'd doubt that the BLM at WOT would be at 128 unless there is a patch in the chip to reset the BLM at WOT. The BLM value in cell 15 is the value normally seen on a scan tool at WOT. This value is a trim for the P/E fuel flow and will change due to various conditions.

My guess is that Jay has already put a patch in the chip to reset the BLM to 128 at WOT otherwise it would be likely the car would run quite a bit leaner that the stated WOT 02 #'s.

I hope this makes sense.

Neal

 

[Dan Thompson]

I would get the header fixed before I did anything else.

As a matter of fact I did fix my header before I tried changing things. It made tune much easier.

 

[NC87GN]

Neal has a good point.. Change the injector constant but put the patch for BLM lock @ WOT. And the fuel table correction, on my part, was not meant for this post Sorry bout that. Got side tracked with another email reply...

 

[subtlt]

More work to do first

Thanks for the suggestions! The chip tuning thing is a bit beyond my abilities at this point; I'll try to fix the little things first then try again. Fix header crack, swap in test pipe for cat, then see what Turbolink has to say.