Took the 95 out for a drive this afternoon. I just recently rerouted the fuel system using an external regulator. The throttle body is fed regulated fuel via a 3/8" hose only and there is no longer a return line coming from the throttle body. The pump supplies the regulator, regulated fuel goes to the throttle body, and all excess fuel goes through the regulator and down the return line to the tank. This made a world of difference and actually cured the incurable lean bog I was having on heavy throttle jabs. Anyway, after doing this I finally put it back into closed loop and installed a new Denso 02 sensor.

So I went for a drive with PE disabled and all in all it ran very well. From a roll or even from a dead stop I can get on it and go through the gears and pull up to 5000+ just fine and in that instance my wideband is actually showing in the 11.5-12.0:1 range. It showed to still be in closed loop but had a commanded ratio of 12.7:1 for some reason. I was hoping to log it in closed loop at 14.7:1 at WOT and see what if any changes needed to be made. Anyway, got back to the house and decided to see if it would break the tires loose. Power braked it and it immediately went lean. I was at 60% throttle, 96 kpa, 1500 rpms, 5600 hz and it was showing 20:1 and actually died on me. This doesn't seem to be because of a lack of AE either. I slowly rolled into the throttle when doing this. So that being said how can it be running at stoitch under normal driving and even WOT acceleration but when power braking it at the same HZ it runs so lean it dies. The only thing I can think of is lack of fuel pressure or volume. The pump is a 96 chevy truck 350 vortec pump running at 30 psi. I find it hard to believe that it needs more fuel at 1500 rpms at 96 kpa then it does at 5500 rpms and 96 kpa. So all that being said whats the deal? Am I missing something?

 

Seems to me the load would be higher "stalled" than rolling so could just be the fuel table needs bumped up in the low RPM, High Kpa area.
Its always hard for me to get those cells good without a vertical climb.
Is the new regulator vac referenced?
If so I was just thinking manifold Vs. ported vac source might cause a fuel pressure difference at different air flows.
Not a TBI guy in depth but figured I'd throw some thoughts at ya.

 

I'm not running speed density, I'm running mass air. Regulator was not vacuum referenced, fixed at 30 psi.

 

What was the temperature outside? With TBI, sometimes it can appear to be "lean" under load, when in fact the fuel is dropping out of suspention and wetting the manifold walls and causing a lean condition. I ran a dedicated manifold air temp sensor for the AE for that reason, so I could smother it in fuel when the manifold is cold and not have it go lean. Try this: do it again, and see if the engine goes lean. If it does, immediately close the throttle and see if the WB goes really rich (~8-10:1). If it does, then the manifold is where all teh fuel is going.

When you snap the throttle all the way open, does the fuel pressure stay steady?

 

That could be but how long does it take to establish a layer of fuel on the intake walls? I had it power braked for several seconds before it leaned out to the point of stalling. The short term fuel trims were adding like crazy but it just wasn't happening. Seems like the temperature was around 40-45 and the manifold temp probably in the teens to 20s. I do have a manifold air temp sensor in the plenum but its a bird cage style temp sensor.

Fuel pressure has a very slight 1-3 psi dip on the gauge which I kind of expect but nothing like it had before I rerouted the fuel system. I actually hooked the vacuum back up to it the other day and scaled the VAFPR table and I was surprised just how accurate it was but being that the pressure was lower at part throttle (about 23-24psi) it did create a big lean condition which I corrected for. In the heart of the table from 4000-7000 hz I added a lot of fuel, as much as 8-9 grams in some cells. I haven't had a chance to drive it yet to see what changes but it seems a little more promising.

 

My setup requires a lot of heat to the intake manifold and TB. Fuel dropping out of suspension is happening for sure. My IAT was previously attached to a radiator fan support now it is in alum tube intake tract at the "black dot" in this photo. Car is barely drivable when air temps are under 45dF until heat soaked throughly. Adding to the issues is no heat crossover in my RPM heads. When I use the N20 I see the enrichment occurring on WB then it goes lean when air temps <45dF. N20 is jetted rich(75 hp shot) and I run a GM TPI pump. N20 in summer retained rich on WB. I think the spray again is pulling fuel out of suspension. Logs of IAT show temp at sensor like 55dF and coolant at 186dF with a 185 thermostat. Again with environ temps at 40dF. Other than runnin a traditional round AC to get more heat not much I can do. right?

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Ronny it appears you are running TBI. You really need to consider a manifold air temp because everything outside of whats going on in the intake is pretty well null and void. When fuel is introduced to a vacuum inside the intake it begins to flash off and change over to a vapor. I'm assuming this is the point it begins to cool too. The effect is much like venting a can of A/C refridgerant. In the can it could be 100 degrees but allow it to switch from a liquid to a gas and it gets cold. TBI is similar in that it keeps the air charge very cool because of the gas within the intake. Anyway, point is even on 40-50 degree ambient air temp days I routinely see MAT temps in the teens to 20s. At idle with the single plane high rise I've yet to see it crack 140 in the summer. The climate inside the manifold is always changing and you need to be able to see that change, not whats going on before the air even gets to the throttle body. On dry flow stuff it works having the IAT somewhere in the air intake but not on TBI.

 

where might I add that sensor? Will EBL support a manifold air temp sensor? Maybe I email dynamicefi.

http://www.holley.com/data/products/...arge300-49.jpg

 

My TBI code has logic to handle this. The current code uses the TFT, but it could be routed to the IAT as well. The IAT isnt needed as much as the manifold wall temp as the setup is MAF. Youll loose some control over the spark, but its possible to reroute teh manifold temp to the IAT sensors location so you can have the manifold temp to directly control the AE compensation. I still have a sensor somewhere that I made for this.

 

I only struggle with the above maybe 60 days of the season. So month of April and November. It is not as big of an issue as I may have suggested.