Tuning $0D for Vortec TBI 357

[woody80z28]

Changed header gaskets from the cheapos to the expensive ones and found out the cheapos had sealed fine, and now the expensive ones are leaking. Damn it. Swapped the lifters and now the valvetrain is nice and quiet.

Also did some logging and found that the truck runs much better in open loop than in closed. If I let it idle for ~5mins it will pull the BLM down to 90 and stall. On restart it will idle at 2000 down to 1500 until you start driving it for a while and then the idle is fine. So I'm gonna get the wideband on it since my o2 does not seem trustworthy. I pulled it out of the Beretta and now I just need to wire it in to the truck.

 

[woody80z28]

Changed header gaskets again and now all is good. Installed the wideband and it is super rich at idle...in the 11:1 range. Needs AE too, it spikes lean hard when you open up the throttle...but I'm sure it was even leaner before and that's why the rich tune has better driveability. Got 6.7mpg on my first tank though, so it needs a lot of fuel trimming! haha

 

[woody80z28]

Ok, I added a pin to the ECM connector at B16 for my wideband signal and it does not show up in the datastream. Any idea why this would be? The $0D XDF has a comment with instructions to send the signal to B16 and I know the Factor, etc are right. I just took this same wideband off my Beretta with $A1 and it was reporting to the datastream correctly.

 

[woody80z28]

Fixed. Had to enable "Linear EGR" in the BIN so that it would report to the datastream. Pulled out VE in the idle table and added 125% AE across the board and it ran awesome tonight. Now it's time to look at the log with the wideband data and really dial it in.

 

[Chris]

Any update man? Sorry I haven't been around.

 

[woody80z28]

Truck has been running great...got me 14.9mpg on the road (still only 9mpg for my commute). But this cold spell this week has me adjusting it again. On a dead cold engine at 0F the driveability was terrible. And since I live a mile from work, that's where most of my driving is...on a dead cold engine. So I added AE in coldest part of the AE temp multiplier. Thinking about adding a MAT sensor to get a more accurate AF when the engine is warming up and the air is still frigid. I checked my intake manifold the other day when it was up to operating temp and the runners were fairly warm (not nearly 195F though)...and the TBI was ice cold.

So I need to find a MAT table for a 4.3 S10 and add a MAT pin to the ECM.

 

[Chris]

Are you still running the stock air intake? If not you may want to find one and hook up the thermac pipe. Mine would be a little sketchy at -5F or so without it.

 

[woody80z28]

No. Intake manifold is a carb Vortec one (with no coolant passage under the runners) and the filter is a 14x3 open element. I have found there is a factory 454TBI adapter that is heated with coolant that I could use in place of my spacer and adapter...but my issues are when the engine is stone cold and then the 1mi drive to work. So anything heated by coolant would not help.

Is this thermac pipe you speak of some sort of hot air pipe (from exhaust I assume)? IIRC there was some kind of heat shield on the stock manifold that looked like it could hook up to a pipe. Those are long gone now though and I'm running headers.

 

[Chris]

Yea that's exactly what I'm talking about. It makes a HUGE difference believe it or not when it's cold as space outside.

 

[woody80z28]

Well, that's not really an option now that I have headers. I suppose it could be done, but it would take some fabrication.

I'm going to give the MAT route a shot. I did some reading on TGO, and since the TBI setup is a wet flow intake the air/fuel charge in the runners can be 40-60* cooler than ambient temp under certain conditions, which will be way off from the coolant temp that the ECM uses...so I think it's a worthwhile addition to blend the MAT with the CTS. Especially considering I have no coolant passages in the runners now and no thermac.