Is there a "how-to" assist when tuning with a wide band ?

[axisg]

Not 100% this should be in the how-to section. Depending on response I guess it could be.

My situation; I installed AEM Wideband on the car and finally got it hooked up this morning for the drive into work. I have started to manually record my readings and they seem ok to me. All the basics are done. Timing 34 deg all-in by appx 3000 rpms. Premium fuel. Carb set at the curb by highest vacuum reading at intake.

Motor
350ci SBC, est 10:1 comp, xr270hr retro roller camshaft, 1:6 rocker arms, patriot vortec heads, 1906 Qjet, dual snorkel air cleaner ( this I noticed as an improvement over stock via the butt dyno ), TES headers & Cat-back 2.5" exhaust
Trans-200r4 - Rear 3.73 with Auburn Posi - Tires 235-60-15 all around

Reading thus far
Cold Idle - 13.5
Cold cruise - 13.3
Cold wot - n/a

Warm Idle - 13.3
Warm Cruise - 13.0
Warm WOT - 17 to 15

When I slow to stop at a light the reading will drop to 10 or 11 for a few moments. Obviously I will data log for another couple days before any changes. But where do I take these numbers from here ? Fatten up the fuel mixture a little at idle and swap in the smaller rear jets on the rear hangers for more fuel at WOT ? I am also curious how running the AC and humid summer days will effect the A/F on the car.

 

[pontiacgp]

you need to lean out the idle, not fatten it up. It should be 14.7 parts of air to 1 part of gas. Once you lean out the idle that will affect cruise as well. If you are running e 10 the real gas will make it even richer. I try to have mine run low to mid 15's on the highway. For your WOT it looks like you will need some slimmer rods to richen it up a bit but I would get the primary side sorted out first. If your A/F is getting rich on braking I would check the float level.

 

[liquidh8]

I'll echo those statements. Though I will say some cams won't let you run idle at 14.7, it may idle real crappy, so try and get it there (14.7) without sacrificing a nice (as possible with your cam) idle.

After idle and part throttle are sorted, then you need to get WOT richer. Every vehicle/engine combo is different. Shoot for 12.8 average for WOT and go from there. Some engines like richer, some like leaner.

My 350 vortec headed, 10.5 comp (etc) loved 13.3 for WOT. I had the fastest trapspeed on the big end with that.

 

[axisg]

So I have about an hour driving and monitoring the readings. The gauge is jumping all over the place esp at idle

I took 1/4 turn in on the mixture adjustment and now it reads between 13 and 19 at idle in gear ( lumpy cam and low idle may be to blame ) then it smooths out to 14-14.9 at cruise. Drops to high 12's / mid 13's when I lean into it and cruises at high 14's mid 15's on the highway with the lockup on. I will turn in another 1/4 turn and see where I am at.

Any ideas why its reading so erratic ? Or do they all do that ?

 

[pontiacgp]

If you have a lumpy cam that could cause the erratic readings but before you adjusted you had a steady reading at idle so did the idle rpm change? What fuel are you running

I forgot to mention this before. The horn gasket isn't too hard to damage removing the horn to make changes to the main rods and jets even if yoiu have it coated with lithium grease. They don't sell horn gaskets separately here in Ontario and a rebuild kit is around $60 so that is an expensive way of getting a horn gasket. You might want to get a couple from this place

http://quadrajetparts.com/quadrajet-airhorn-gaskets-c-128_25_39.html

 

[axisg]

Thx for the link Steve. I will definitely order up a gasket or two ! I run either Esso or Petro 91 in the car. However I don't know what is up with the sensor and its erratic readings. The first day the numbers were fairly gradual ( jumping 2-3 points ), the next two days they were erratic ( jumping back and forth about 5 points on the scale ) . Now they seem to be coming back within the 2 point range. At idle it is still reading all over the place but once above 1500 rpms the reading comes more consistant.

So I am total 1/2 turn leaner on the mixture now.
COLD idle / cruise is roughly 12.9 - 13.9
WARM ( 3.7 kms to work ) and its 14.2- 15.1 range both idle / cruise
WOT and it drops to high 12's for a half second then as it builds power ( and the secondaries pull open ) that drops to mid 13's.

I can see how having access to a dyno would be beneficial at this point. Tuning this was has cured my occasional stumble when going to WOT from lower Rpm's, however the offset is that the car dieseled for a second at shutdown when I arrived a work today. I will bump it up a little and break out my timing light tonight to see where I am at. I would guess that the leaner mixture needs more timing.

 

[pontiacgp]

Since you are already running 91 try premium Shell, Canadian Tire or Ultrimar if the fuel your using is e 10 . The fuels I mentioned have no ethanol in them

 

[liquidh8]

Cold and warm idle and cruise look good, if it runs good drive it for a bit. Does it bog when the secondary's open?

I also second the air horn gasket. I can usually re-use one 2 or 3 times before I inadvertently tear it.

 

[axisg]

I tried to rule out the dieseling at this 14.2 - 15.1 setting by advancing the timing ( no luck ), then retarding the timing ( no luck but no worse ) so I am back to yesterday setting. I cruise at 13.5-14 and drop to high 12.5 - 13.3 at WOT. It feels like I am making the most power at this setting. It will light the tires from a roll and put down rubber on the 1-2 shift. Any leaner at the carb or messing with the timing advanced and it doesn't "pull" as well.

Def a cool game to play this summer.

 

[pontiacgp]

what about the fuel, if you are running e 10 the non ethanol gas will richen up the mixture without adjusting the carb and the engine will run better