IEP - Why fit low powered diesel engines?

[Envoy]

I understand that the IEP trains on order for GWR will now all be hybrid versions but will come with diesel engines that can only do up to 100mph. Would it really cost so much more to have more powerful engines that can enable these trains to do 125mph when off wire?

When the line to Swansea is electrified, then all electric - apart from one coach having a ‘modest’ diesel engine underneath for emergency use - would be suitable. This was indeed going to be the original order but the delays in getting the wires up has caused the switch in order to more hybrids. So, let us assume that the entire line to Swansea is finally electrified and the opportunity now exists to make a further order for more IEP’s which will run on electric power. That being so, the ‘low powered’ hybrids could be switched elsewhere - such as to Cross Country. But, if that were to be the case, they would not be able to offer the same speeds as the present Voyagers and would also be slower on the Devon banks.

Surely, spending a few bucks now on more powerful diesel engines on these hybrids would give greater flexibility for any future cascades to other routes?

 

[JN114]

I understand that the IEP trains on order for GWR will now all be hybrid versions but will come with diesel engines that can only do up to 100mph. Would it really cost so much more to have more powerful engines that can enable these trains to do 125mph when off wire?

When the line to Swansea is electrified, then all electric - apart from one coach having a ‘modest’ diesel engine underneath for emergency use - would be suitable. This was indeed going to be the original order but the delays in getting the wires up has caused the switch in order to more hybrids. So, let us assume that the entire line to Swansea is finally electrified and the opportunity now exists to make a further order for more IEP’s which will run on electric power. That being so, the ‘low powered’ hybrids could be switched elsewhere - such as to Cross Country. But, if that were to be the case, they would not be able to offer the same speeds as the present Voyagers and would also be slower on the Devon banks.

Surely, spending a few bucks now on more powerful diesel engines on these hybrids would give greater flexibility for any future cascades to other routes?

It's been done to death in the IEP thread already, but to repeat here - once the GW wiring is done there won't be any non-electrified 125mph line on the GW. No need to add £££ to the already astronomical price tag for these units on engine power that simply isn't required.

 

[richw]

Why do they need 125mph ability, nowhere out of the initial wiring has 125 running as far as I'm aware.

 

[LNW-GW Joint]

This has been covered ad nauseam on the IEP threads, but the gist is that all lines over 100/110mph are in the process of being wired.
So there is no call for full-throated 125mph on diesel.
Cardiiff-Swansea is irrelevant - none of it is over 100mph, the 125mph finishes at Stoke Gifford (Box on the Bath route).
The interim period before the wires reach these points will be "interesting".

 

[ainsworth74]

As well as the good points above I feel it's worth pointing out that the SETs will have engines capable of propelling them at 125mph but that the engines will be derated by the on board computers to improve reliability (with the option to uprate if an engine fails to compensate for the loss of power).

The GWR ordered AT300s have exactly the same engine as the SETs and are capable of 125mph as their engines are going to be used with any derating.

 

[jimm]

As well as the good points above I feel it's worth pointing out that the SETs will have engines capable of propelling them at 125mph but that the engines will be derated by the on board computers to improve reliability (with the option to uprate if an engine fails to compensate for the loss of power).

The GWR ordered AT300s have exactly the same engine as the SETs and are capable of 125mph as their engines are going to be used with any derating.

Though in the case of the AT300s, running the diesels on full power all the time is to give them maximum oomph for climbing the gradients between Exeter and Plymouth (and the Cotswolds), rather than for speed-related reasons.

 

[TGV]

It's not just "spending a few bucks" to uprate the engines. Yes they're the same physical GU assemblies as a non IEP AT300, however the maintenance plan is designed around the engines having an output of 565kW for a given number of hours' operation (based on known diagrams etc.). If the power is upped to the full 700kW (~950bhp) then the maintenance regime changes, which has a far bigger cost implication than just a software mod. It's also affecting the GU life cycle costings and time between overhauls etc... It's a huge problem.

 

[Envoy]

Many thanks for all your responses.

 

[ainsworth74]

Though in the case of the AT300s, running the diesels on full power all the time is to give them maximum oomph for climbing the gradients between Exeter and Plymouth (and the Cotswolds), rather than for speed-related reasons.

Yes true I could have made that a bit clearer. The 125mph thing is more a byproduct than the intended result.

 

[TheKnightWho]

I think calling them low-powered is quite misleading - even underrated they're slightly more powerful than a Voyager. I'm guessing it's the gearing that causes the speed discrepancy between the two classes, which means they're likely to be even quicker off the mark!