Engine almost stalls when fan turns on

[karolko]

I wonder if this can be fixed within the XFI, thus i am asking here.

When i start the car and let it warm up, when in IDLE, and the fan is triggered, the engine boggs down really hard and almost stall, it then recovers and goes back to idling just fine.

Is this something i can tune out with the XFI or is it a wiring problem?

Someone i spoke to mentioned that i might not have a large enough wire going from the alternator to the battery? Can anyone comment please.


Adrian

 

[norbs]

Yes you should change it to at least 4 AWG, what size alternator do you have? You might be able to tune it out by adding ve to the cells where this is happening, or adjust the voltage offset table ever so slightly, but this will supposed cause errors in % o2 correction.

 

[Mike E]

Datalog battery voltage when it happens.

Is your ignition and fast power and ground hooked directly to the battery?

 

[HighPSI]

Mean Mike hit it on the head. Datalog it, then adjust the injector offset vs battery voltage to keep the A/F clean. You will see the voltage drop momentarily then recover. Watch the A/f closely when it drops.

 

[norbs]

You may also want to data log HR PW. to study this more closely too. The bigger gauge alternator wire will not hurt anything.

 

[karolko]

i am running the stock turbo6 alternator, which i think i 105amp.

i have a 10AWG wire going from the alternator to the starter and then i have a 4awg going to the battery. I also have a 10awg wire going directly to the fuel pump.

I am running a stock wiring harness, go i do not have wires going directly to the battery.

I will log this all when it happens and post back, but this will take a month as i am overseas right now.

is the injector offset vs battery voltage a XFI 2.0 addition, i forget. I ordered it from you Cal, but have yet to install it.

on my last datalog of a full run, i am only getting 13.9volts logged at WOT. Could this be a issue of too small of wire from the alternator to the battery?
Is it okay to go through the starter or should i go directly to the battery?

Thanks for all the advice.

Adrian

 

[Mike E]

i am running the stock turbo6 alternator, which i think i 105amp.

i have a 10AWG wire going from the alternator to the starter and then i have a 4awg going to the battery. I also have a 10awg wire going directly to the fuel pump.

I am running a stock wiring harness, go i do not have wires going directly to the battery.

I will log this all when it happens and post back, but this will take a month as i am overseas right now.

is the injector offset vs battery voltage a XFI 2.0 addition, i forget. I ordered it from you Cal, but have yet to install it.

on my last datalog of a full run, i am only getting 13.9volts logged at WOT. Could this be a issue of too small of wire from the alternator to the battery?
Is it okay to go through the starter or should i go directly to the battery?

Thanks for all the advice.

Adrian

Injector offset vs. battery voltage is not new.

13.9 at wot is fine. But when the fans kick on the voltage probably drops down considerably. Enough that everything sensitive to voltage takes a hit. Ignition, injectors, fuel pump etc.. Your alternator wire being small shouldn't have much affect on this .

If your battery is in the trunk and you have a disconect switch, the charge wire from the alternator needs to go all the way back to the + post on the battery. Otherwise your disconect switch is useless because the alternator will run everything when the switch is off.

 

[karolko]

Mike, the batterey is in the stock location. No shut off switch, just factory stuff.

Would everything run nicer with more voltage. I remember the voltage running in the 14's at idle, so i am curious why it drops at higher RPM?

I checked the log, and my fan was already running throughout the pass, so i did not see a voltage drop or anything when something turned on, just a straight line.

Would a 140amp alternator makes everything happier?

Adrian

 

[GNVenom]

Are you using dual fans, or a single fan? The power sag is almost certain when using dual fans, unless you stage them (five second delay works well).

If using dual fans, be sure to use two relays and stage one of them.

 

[TurboDave]

Except for the ramchargers fans, right John?

 

[karolko]

i am using a single S-blade fan. the specs say it draws 19amps. I am running a Magnafuel pump, XFI and MSD DIS4 nothing else too major. Thus my confusion with the large drop in RPM's.

 

[TR Custom Parts]

I have the "miracle" 200amp alternator from a source that remains nameless with #4 wire back to the battery along with dual Spal fans with the staged relay harness from Caspers. No change from the stock alternator and wire. Still get a slight drop when each fan kicks on.

 

[karolko]

Mark, when you say slight drop, how many RPM does it drop? Does it sound like it is about to stall or is it similar to what happens when the A/C clutch fan turns on for the first time?

Adrian

 

[TR Custom Parts]

Never really checked it. Next time I have the laptop connected to it I will try to remember to record where the fans come on. It isn't enough to stall the car but it is noticeable.

 

[Street Lethal]

MeanMike is correct, and its a very common issue. When the fans kick on you will immediately notice that the FAST system will have up to 20% O2 correction for a fraction of a second because of the heavy load of the fan(s), and that is because of the voltage drop to the pump, injectors, etc....

 

[karolko]

I will do what cal and Mike recommended. I will log when the fans turn on and then adjust the injector offset vs battery voltage. I do not expect to get it perfect, but i would like to make it better. At the moment when the fans turn on, it sounds like the engine is running on two cylinders fo a second or two before it recovers.

Adrian

 

[HighPSI]

is the injector offset vs battery voltage a XFI 2.0 addition, i forget. I ordered it from you Cal, but have yet to install it.

It is a new feature for the 2.0 You may or may not have already had it since I may have given it to you in a beta version.

my last datalog of a full run, i am only getting 13.9volts logged at WOT.

Keep in mind, unless you've rewired the fans, they should be turning off when you are at WOT.

 

[karolko]

$hit i did rewire the fans, how would i go about checking to see if they are infact shutting off at WOT and could you tell me how to rewire it if i had to. it makes sence to have them shut off and save voltage for othr more important things. currently i only have one relay, no high/low and delay. i got rid of that stuff. you know, weight savings

no i did not get the beta version so i have to wait to get the 2.0 put on the computer. i will call you once i am home to finalize the 2.0 install.

PS is there a 2.003 version?</p>

 

[HighPSI]

You can check it, by warming the car up until fans come on (or lowering the turn-on point in the program). With the engine off, key on, floor the throttle and see if they turn off.

I will get you the "latest" software when we meet up in Calgary or Bowling Green, whichever comes first

 

[karolko]

thanks cal for the info. I will try it once i get home.

Adrian