Class 175 (and 180) "Boost mode"

sw1ller said:

Possibly a Sunday between wolves and Crewe via stafford. Can get a bit rickity. There was one unit running around with rather poor (but serviceable) suspension the other day and even I was glad to get off it.

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Ah yes, I always forget that one - and I've not had the pleasure of working it yet.

sw1ller said:

Yes, there’s a difference between 3 and 4. Nothing major, but It’s noticeable.

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That's interesting because I was previously under the impression that there was no difference except Notch 4 would've given Traction Boost had it not been disabled.

It now seems not only is Notch 4 different to Notch 3, but it isn't how Traction Boost is selected and furthermore Traction Boost hasn't been disabled either.

Erniescooper said:

Because you have sent a signal to the ECM to let it know that you require traction boost it can increase the fuelling rate above what it would when it was rated at 450hp

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So it generates the additional power simply by increasing the fuel rate and dropping the HVAC load?

Something else I've recalled - I think Class 175s have a speed set, yes? If so is it routinely used or not?

They were built with it, but it never worked. Sure it was diconnected some time ago. The notches on the controller do not realy mean anything, as the power demand is infinately variable between 10% & 90%.

hexagon789 said:

Something else I've recalled - I think Class 175s have a speed set, yes? If so is it routinely used or not?

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I’ve had one driver tell me he’s found one that’s worked, but I’ve never bothered and Believe it’s been disabled on most/all of them.

The notch 3/4 difference is noticeable when you drive. When you know you’ve moved from 3-4-3 you can hear the engine note change slightly. I’ve also tested getting to 50 at certain points using 3 or 4 and there’s also a noticeable difference. It’s not huge though.

The main thing about notch 4 is power control. If you move from 4 to 3, 2 or 1 then it takes about 5 seconds for the engine to actually respond (4 to power off is immediate) where as 3 to 2 or 1 is immediate. So if you’re trying to control your speed on hills, it’s not an ideal notch to be in. But it’s not much of an issue at all.

Tynwald said:

They were built with it, but it never worked. Sure it was diconnected some time ago. The notches on the controller do not realy mean anything, as the power demand is infinately variable between 10% & 90%.

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Unreliable for some reason?

Quite a few newer units seem to be like that, the power settings have notches but they can be ignored.

sw1ller said:

I’ve had one driver tell me he’s found one that’s worked, but I’ve never bothered and Believe it’s been disabled on most/all of them.

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A "special" unit then?

sw1ller said:

The notch 3/4 difference is noticeable when you drive. When you know you’ve moved from 3-4-3 you can hear the engine note change slightly. I’ve also tested getting to 50 at certain points using 3 or 4 and there’s also a noticeable difference. It’s not huge though.

The main thing about notch 4 is power control. If you move from 4 to 3, 2 or 1 then it takes about 5 seconds for the engine to actually respond (4 to power off is immediate) where as 3 to 2 or 1 is immediate. So if you’re trying to control your speed on hills, it’s not an ideal notch to be in. But it’s not much of an issue at all.

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Interesting that going 4 to a lower notch rather than to Off should work like that, a quirky of the throttle set-up perhaps?

If it's shall we say a 'subtle' difference between 3 and 4, is it a case of 4 places a greater load on the engine rather than increasing engine revs?