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Cosworth Starter Motor Drawing Too Much Power
lordbenny - 9/11/12 at 11:05 AM

Ok, I have another thread running on my starter issue but I need a quick answer to this question:

Will a Cosworth starter motor draw more power than a standard motor. I have a Cosworth one on my 2:0 Zetec Westfield and it seems that the ECU may be cutting the spark because the starter motor, although cranking over beautifully, may be using up too much power taking the required power below what is needed for the ECU to work?

Could this problem be solved by simply bolting on a standard motor?

[Edited on 9/11/12 by lordbenny]

matt_gsxr - 9/11/12 at 12:22 PM

Is your ECU wired back to the battery?

lordbenny - 9/11/12 at 12:25 PM

quote:
Originally posted by matt_gsxr
Is your ECU wired back to the battery?


When you say 'back to the battery' do you mean directly? If so, no, so I pressume the power comes through the starter which is why I have asked the question re: power drain.

MikeRJ - 9/11/12 at 12:36 PM

Simple answer is no, if it's in good condition, especially as the Cosworth YB is a pretty low compression engine. However, it's quite possible to have a shorted winding with the motor that would cause it to take excessive current.

MikeRJ - 9/11/12 at 12:38 PM

quote:
Originally posted by lordbenny
quote:
Originally posted by matt_gsxr
Is your ECU wired back to the battery?


When you say 'back to the battery' do you mean directly? If so, no, so I pressume the power comes through the starter which is why I have asked the question re: power drain.


He is asking if your ECU power connection goes back to the battery terminal (via relays etc.) rather than to the starter connection. Any voltage drop across the starter cable will then not affect your ECU.

snapper - 9/11/12 at 12:51 PM

Proper Cosworth starter draw more than a Pinto, often used as an upgrade for high compression engines
The biggest issue is usually a bad earth, you need a good thick earth cable from battery to starter mounting bolt and another good earth to the chassis
The gearbox on a Sierra is also earthed with thick cable from the gearbox central mounting bolt

big-vee-twin - 9/11/12 at 12:59 PM

Have you checked your battery voltage when cranking?

lordbenny - 9/11/12 at 01:51 PM

Just had the battery checked and initially its drawing around 350 amps then down to 300 amps on cranking. Apparently thats a bit to much so Im having the armature swapped for a freshly wired one. I hope this does the trick.

[Edited on 9/11/12 by lordbenny]

MikeRJ - 9/11/12 at 03:35 PM

quote:
Originally posted by snapper
Proper Cosworth starter draw more than a Pinto, often used as an upgrade for high compression engines


A motor will only draw what current it needs for a given load. I very much doubt a Cosworth starter is so inefficient that it draws significantly more current than a Pinto starter for the same load.

BaileyPerformance - 9/11/12 at 05:24 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by snapper
Proper Cosworth starter draw more than a Pinto, often used as an upgrade for high compression engines


A motor will only draw what current it needs for a given load. I very much doubt a Cosworth starter is so inefficient that it draws significantly more current than a Pinto starter for the same load.


Mike is correct...

In fact the later cosworth starters are a geared starter, it turns the engine over slightly slower than a pinto starter and pulls less current that a pinto starter.

Cosworth starters are not really any more powerful than a pinto starter - any starter motor will produce massive torque assuming the battery can deliver the required current, the way starter motors are wound means it will keep pulling more and more current until the battery voltage falls or it burns out!

The cosworth starter was developed for smooth cranking, there is no reason to assume a cosworth engine need more energy to start it as it as a compression ratio of 8.3/1 standard.

britishtrident - 9/11/12 at 05:35 PM

Any starter drawing 300 amps will start to give off smoke and then glow.
It is drawing huge current the starter is stalled --- basic DC motor theory.
It is stalled because it is fighting the engine which is trying run backwards because the ignition is over advanced at cranking speed.
If the Engine wants to run backwards it will always beat the starter.

I have a theory that the ignition is because you have a Fiesta or Focus carb CVH ignition system.

[Edited on 9/11/12 by britishtrident]

lordbenny - 20/11/12 at 10:19 AM

So, after fitting new battery and re-con starter motor how do I adjust my ignition advance when cranking?

Seems that there's too much when I'm trying to start the car as it takes ages to start (that's if the battery dosn't go flat first!)

It's an MBE ECU. Can the ignition be made to be less advanced when cranking only? Do I need to take it to a specialist?