heavy electrical load stumble
 

basically i have a stock port with an LT10s. the problem is i have a lincoln 18" fan running off of a spal PWM controller. when the fan kicks on the engine bogs down and goes lean to the point where it wants to stall. i have compensated for the bog by adding fuel in the next load cell, which works ok but not the way i want. i am also not running a BAC.
i have to mention that i have had the same fan running the same way off the stock computer and it never bogged. is it just the maps that need to be adjusted? is there a way to compensate it in the microtech without running the BAC?

I'm assuming that the fan has it's own powersource of course and is being driven by a relay. My suggestion? You need a bigger alternator. I'd use an s5 alt (80 amps) or a s6 alt (100 amps). I also add a 4 gauge wire from the alt 12v+ to the (+) terminal on the battery.

The Microtech has poor resolution on the Matrix table and isn't very good and interpolating between values. This is what causes the issue. About the most you can do without a BAC is tweak all the surrounding load cells until you find a point where it's rich enough to keep the idle from drooping too much but not excessively rich. FANADD can be used to add a bit more fuel.

Best bet is to run a BAC, but unfortunately this means sending the unit back to Microtech.

A bigger alternator won't help. As mentioned, the FAN is on a FAN-PWM unit.

get rid of the controller.use the microtech to triggr the fan. and then youll be able to add fuel everytime the fan kicks in.
done.

i forgot to mention that i already have an S6 alternator, i think aaron is right with the map being low resolution. i already have the load cells around idle tuned so that when the fan kicks on it doesn't completely stall out, it idles normally around 12.8 to 13.1 afr. when the fan kicks on it dips sometimes to 14.x and leaner, to the point where it almost stalls.
why would i have to send the microtech back to control a BAC?
can i still utilize the PWM controller and compensate with fanadd?
i currently don't have the fan controller wired with a relay, should i do so? i was told that the PWM itself is a relay. and that it would make it redundant.
i guess i could just use the microtech to control the fan but i kinda didn't like the whole on/off thing. i like how the fan speed ramps up.
i think i am going to have to run the bac since i also want to run a/c.
i am thankful for all input, if you have any other suggestions please fill me in

this is the culprit
 

i have this run by a 60 amp fuse in the fuse box with heavy gauge wire, and switched power to the PWM by a check connector, is this not the best way? input please

I don't quite agree. The Microtech's fan control is simply abysmal compared to the FAN-PWM. The aux output on the Microtech is a good stop gap if you just need to control a fan and can't afford much more then a relay. But the FAN-PWM is a variable speed PWM controller that makes the electric fan act much more like a clutch fan with a speed proportional to engine temp.

I have the FAN-PWM on my car and it's resulted in much more steady temperatures and a more consistent load on the engine. It's made the idle area easier to tune because I'm not constantly fighting the inconsistent load of a relay triggered fan.

Do you have the FAN-PWM set correctly? Sounds like you have the fan speed set too high. The fan should not really "kick" unless the temperature of the car is at the high setting. There will be a kick as the fan initially starts but this should be a few degrees below thermostat temp anyway so you will still be running a tad rich as the warmup enrich finishes off.

If it's dipping to 14:1 and leaner, it's a tuning issue for sure. Check surrounding cells and I bet you'll find one too low.

I'm assuming the LT10 is the same as the LT8. If it is, and you did not order the BAC option, you need to send it back to Microtech to have it installed. Very, very stupid.

Sort of. If you set the fan temp on the Microtech to the temp at which your fan draws the engine down too much, you can then use FANADD to add a bit of fuel. But the aux output is still unconnected. I've not found this unnecessary.

You're half correct. The PWM itself removes the need for a relay (I don't even know how you would rig both of them up?) but is not a "relay" per say.

I agree. On/off fan control is far from ideal, and damn annoying as well.

You'll need a BAC for A/C unless...

But it sounds like you have two issues here:

1. FAN-PWM set to aggressively. What is your high and low point?
2. Still some tuning to be done.

Hey Aaron, thanks for replying. I do have the load cells tuned a bit odd. But that is so I am not idling unnecessarily rich at idle. I will take a pic of my matrix table and you will probably see better. I have the low speed on the pwm set at 90'C and high at 105'C, maybe a lower setting will just keep the fan on but stop it from cycling excessively.

Never had a problem using the microtech to switch fans on and off. look at most proper factory cars. fan on for a good 10/20 seconds then off again.

having variable speed fans is a luxury not required, bit of a waste of time, but this is my opinion.

Whoa...I think you will have overheating problems with those settings.

I have my low set to 80 degrees, and my high set to 92 degrees. Of course it depends on your fan. One thing you want to make sure is that your fan is on low speed at thermostat temps. This will keep the electrical draw very low, and keep temperatures very consistent.

Another benefit of the FAN-PWM is that it works very well to prevent intercooler heat soak in traffic. Even with the fan at low you will get enough airflow to keep it cool.

I have never had overheating problems with this fan. It is 18" yes "18" and I don't have specific flow ratings but it was claimed to pull 4800 cfm at 14v static. I have never had the temps even pass 95C. But I think I will lower the low setting, the fan will be running at 50 percent all the time but at least it won't keep cycling.
I figured since the fan is so powerful I could have the low setting higher. I happen to like the fan controller so it will stay in. Has anyone used the microtech to run a fan that draws as high current as mine? My fan supposed to have a 60 amp fuse from the Lincoln mark VII.

The amount of current the fan draws is immaterial to the Microtech as it's just providing a low level signal to switch a relay.

Setting your low point to just below or just at thermostat makes it mimic the clutch fan, which is what the FAN-PWM is designed for. You'll find it will keep your temperatures very stable.

I agree, those settings are too high (well, atleast for me). I have mine set at 185 F (85 C), and it doesn't turn off until 165 F (74 C). Although I'm using a relay, I'm giving an example of temps. You have your low set at 203 F and your high at 221 F !! The boiling point of straight water is 212 F (100 C). Granted, a mix of glycol and water raises the boiling point, but still!!
Consider this.

i have just changed the settings today to see how it will run. i have my low turn on temp set to 82/84 degrees and the high at 92/94C. so far on the ride home the temps never went above 86*C. the thing is that the fan cools too rapidly( not that i'm complaining). Since i have set the turn o temp lower it will still cycle on and off while idling. when i'm driving it remains more consistent.
i have also added another m/s of fuel in the 15"hg idle cell to compensate for the dip. it now dips the afr's to high 13's sometimes 14.0, which is livable. i just want to get as much driveability issues sorted before i go baseline on the dyno next week. then i put in the 35R!

The fan shouldn't cool too rapidly. The thermostat will keep the engine at a constant temp.

You can try raising your high point. Sounds like you fan is very large and can stand less speed at low temps. Bring your high point to 98 or something.

Tuning the fan controller is a bit like tuning the fuel curve. It takes some time to find settings that work well.

I agree that the fan needs "tuning". The fan's low setting is cooling the engine too rapidly. It cools to beyond the turn on temp and has to heat up again. I have tried the new settings and now the fan is not cycling as much, the temp is regulating at 84-86C.

Sounds like you're not running a thermostat, or it's stuck open.

no i am running an oem new thermostat, the new setting seems to do the trick.

doesn't the LT10s have BAC controls? i see that it can control pwm output.

I'm not sure if the BAC control is enabled or not when you purchase the unit. Someone who has used an LT10 can probably answer this. :) I stopped using Microtech except under specific circumstances due to the limitations of the unit...

on the lt10 it is enabled.

Yes I use it and it works fine. (LT10s)