The Rapid 1

OK this real stupid I know, but why when I put my fans on does the tickover drop.

They aint mechanical so no extra loading on engine.

Would it be something to do with current loading on alternator as they do pull quite a current I spose.

so if this true then if was racing and fans on can it affect performance ?

When drag racing ill normally sit in the fire up lane just b4 staging and get my engine to its best operating temp which sometimes means putting the fans on for a bit but then turn em off b4 racing, but on odd occasions the engine been too hot and they have been on while racing.

If it is to do with the alternator, still same question how does it make the engine drop in revs, maybe this is getting more tecqunical spose if u got a loose fan belt and put your lights on then yes this does induce more of the screaming from the belt.

So ok, simply, why does it, does it somehow induce more magnetism in the rotor somehow making it harder to turn ?

Steve

Christian and Beccy

iTrader: (14)

When mapping Omex systems, we map a compensation for Battery Voltage Drop.

If you watch the Air/Fuel Ratio on a car that hasn't had a compensation for this and turn on the heaters/fans etc, then you can often see if go lean. This would be the same for the Cooling fan/s. You imagine if the car has been mapped fairly close to its limits, then on one occasion you drive it hard with the Headlights, Wipers and Heaters on etc. It could potentially be fatal.

Some might say that this is negligable, and some systems don't have the facility to compensate, but we do it because our Omex systems are capable.

Each to their own I guess.

Hopefully that might shed some light on your question.

CraigN

the fans draw a lot of power which in turn draws power from the alternator which is extra load on the engine

Chipperx2

Yeah this happens to me if I turn my headlights on too and the inside fan, A/C is the biggest power sap affects the performance quite alot tho i can imagine

Stu @ M Developments

iTrader: (12)

Fusebox tails will be corroded and on their way out in most cases Steve and this is dropping current from the ecu when they kick in.

This problem, when left, can cause a whole engine meltdown, so best find the cause ASAP.

The Rapid 1

But how or why does the alternator atually put the loading on the engine.

That omex sounds pretty cool then but again how would the alternator make a car run lean, does it affect the injectors as well then can see this more than the loading due to it taking power away from the injectors, but probably aint that simple

Steve

The Rapid 1

My fans are fed from a totaly seperate relay which is controlled by a switch inside the car and the original temp switch on the rad, but all other wiring for fans is direct from the battery through a fuse to the relay and then onto then fans themselves ok the only weak link may be where i joined to the fans original wiring

Steve

foreigneRS

did you never have dynamo lights on your bike?

Stu @ M Developments

iTrader: (12)

The issue though is still that the current draw from the battery is affecting the ECU compensation.

A decent running and well mapped cossie wont do much iof anything at all when the fans kick in.

Best thing to do, IMO, is to check the battery voltage at the ECU when the fans are in, and see what transpires from there

Theres a big post about this in the tech essays forum i recall

Karl

Hi,

There are two main issues at idle to deal with here. One is engine torque compensation, the other voltage compensation.

With regard to engine torque compensation, when we demand extra current flow from the alternator this puts a direct increased load on the engine. In order to maintain the same idle speed, we need to increase engine torque to compensate for the increased load. This is done on simple fuel injected cars either through the ISCV or throttle (if motorised throttle applications) or in more modern ecu's by adaptive ignition as well. Effectively what we do here is allow an increase in air flow to maintain the same engine rpm. If you are running your base idle speed above that of your target ISCV speed (i.e. mapping) then you will see a reduction in rpm at idle when you increase electrical load.

The other issue as mentioned is voltage compensation. As electrical load increases we see a loss of voltage at the ecu. This reduction in voltage increases the injector 'dead time' (or response time for a simpler explanation). This means that the injector response on time is less for a given calibrated value as ecu voltage falls. We compensate for this by using voltage compensation within the fuel calibration, which effectively increases injector duration as voltage falls, so that the same amount of fuel actually leaves the injector.

This voltage compensation has the most significant effect at very low injector operating times (i.e. idle and very light load areas)as the injector dead time as a percentage is a more significant proportion of the calibrated on time. Thus on boost where injector on times are much longer, the relatively small change to injector response (dead time) by falling voltage is very small as a percentage of the total injector on time and will not cause you any real issues. (in other words dont worry about having the fans on when using boost as its effect on overall fueling will be VERY small)

However to cure your problem, you need to either lower you base idle speed to the calibrated ISCV range, or remap the voltage compensation and/or the ISCV range as well. (Assuming of course there is'nt a loom issue which is always possible!!)

Stu @ M Developments

iTrader: (12)

Just to clarify:
The effect the fans have on fuelling is actually huge if you have a problem with those tails i mentioned earlier. Karl and I are talking about 2 totally different issues here in case anyone doesnt realise.

As said earlier, theres a great post about it here:
https://passionford.com/forum/viewtopic.php?t=53903

With the happy conclusion here:
https://passionford.com/forum/viewtopic.php?t=54413

The Rapid 1

wow this a bit more complex than i was bargaining for lol

Best I go start reading there then

Think reading what Karl just put its the first time i ever realised just how complicated being a mapper must be, just how many things u gotta know about and take into account

Not to dis anyone but u get someone like Phil (who I respect for having a go) who gonna map there own car do they really apreciate all what is involved (hope they do)

Maybe i have exageratted my problem (not that i even realised i had a problem actually, was just curious ), when i say revs drop, i cant even see my revs at that low a point (due to an obstruction ) but I hear a slight change in tone of the engine, would that be normal then

Steve

Karl

Hi Steve, Does'nt sound like you have much of a problem, but probably best to get the car setup if nothing else if you're worried about fueling issues.

As Stu has said above I was talking about calibration issues, and if as Stu has said theres a wiring issue then I certainly would advise getting things sorted!!!

EssexBoyRacer

if its of any use. There was a product a little while ago go Alterpower I think, it would disconnect the alternator and force the car to run off the battery alone, which meant less load from the alternator on the engine.

it had a safety trick that would bring the alternator back in if the battery dropped too low etc..

I've never used it however or known n e one that has.

Stu @ M Developments

iTrader: (12)

Steve,
I expect both Karl and I imagined you to have the common problem where the fans come on and it starts revving up and down uncontrollably

Your issues sound minimal, but best get em looked at just to be certain

If mapping garbage interests you, make sure your up to speed with this old topic:
https://passionford.com/forum/viewtopic.php?t=93911

The Rapid 1

Well i wasnt

Never had any problems with wiring, car only done just over 60,000 miles, ye i know the wiring still 14 years old but if hasnt had so much use surely it will still be in better shape than a car with 100,000 +

Seriously tho dont think i got any fueling issues specialy on boost, if anything car runs a bit rich for safety

Steve

The Rapid 1

Well from just reading the above posts from Stu And Karl surely that a bad thing if the engine aint been mapped for use with that.

Ill get a chance to go read them other topics shortly, mind u just Karls explanation above gave me a head ache lol

Steve

Stu @ M Developments

iTrader: (12)

You learn fast pal


When you read the wiring topic, take note of the mileage and condition of Jim Greens car

The Rapid 1

Not sure i gonna like this am I lol

Stu @ M Developments

iTrader: (12)

The Rapid 1

wernt so bad
Was expecting to see a horror story lol

Never had any issues with any of my wiring, and even the fan question, far as far back as i can remember (ive had the car 8 years my sis 2 years b4 that) they always done it , was just sat there this morning and flicked em on and off a couple times and it that small a change I had to do it a couple times to prove it was doing something, but once running youd never know if it had changed or not.

So dont think ill b worrying about my wiring at the mo I aint wanting to go look for problems I dont know I've got, ill stick with the ones I know I have for now

Steve

Stu @ M Developments

iTrader: (12)