Stepper motors on Rover V8 SU HIF44E carbs

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n1tr0_9
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Stepper motors on Rover V8 SU HIF44E carbs

Post by n1tr0_9 » Sun Dec 03, 2017 9:46 am

Im rebuilding some carbs for a Rover V8. They are the later ECU controlled carbs with stepper motors on the side. Unfortunately i stripped them down before reading in the workshop manual that under no circumstances should they be separated from the carb bodies. The manual states they are set at factory and shouldnt be disturbed.

My question is what will happen if i just bolt them back on? They are held to the carb body by three screws with no external adjustability, so it must be an internal setting of the stepper motor. However I assume they are just some kind of port or orifice opening and closing device and therefore their basic settings would be broadly similar and any further adjustments made by the mechanical settings of the carb?

Anyone done it before?



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ChrisJC
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Post by ChrisJC » Sun Dec 03, 2017 5:17 pm

I can't answer your question, but I am intruiged by what they are from?

Since you have no choice, I would just chuck them back on and see what happens! I think all they do is control idle speed by opening the butterfly under ECU control.

Chris.
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Series IIA 4.6 V8
R/R P38 4.6 V8

n1tr0_9
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Post by n1tr0_9 » Sun Dec 03, 2017 8:47 pm

ChrisJC wrote:I can't answer your question, but I am intruiged by what they are from?

Since you have no choice, I would just chuck them back on and see what happens! I think all they do is control idle speed by opening the butterfly under ECU control.

Chris.
They are from a 1986 Rover Sd1 3500

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Post by unstable load » Mon Dec 04, 2017 4:40 am

The steppers will need to be "zeroed" at neutral/closed position otherwise it may damage them when the system powers up.

There is a way of doing it, but I am not familiar with it, only hearsay from a mate who did something similar with a modern throttle body.
Cheers,
John

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Post by n1tr0_9 » Mon Dec 04, 2017 8:38 pm

Anyone know how to do this?

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Post by unstable load » Tue Dec 05, 2017 4:24 am

I'll ask him where he found the info when I see him next.
Cheers,
John

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Post by n1tr0_9 » Thu Dec 07, 2017 10:41 am

unstable load wrote:I'll ask him where he found the info when I see him next.
Great thank you.

As a further update, I spoke to Burlen SU today and asked why they shouldn’t be removed. They weren’t sure. They sell replacement stepper motors for about £60+vat, so they must be reasonably interchangeable.

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