Turbocharging vs. Supercharging

[CSSHEGEWISCH]

The fate of some of the SP SD39's shows them to continue in low-speed service. Some wound up on an Arizona short line hauling copper ingots and two are on the IHB in transfer service.

[M636C]

Mark,

I've been to all the management courses where one is told that you can only make decisions based on results and not on intentions, and I don't mean to waste the forum's time on speculation.

The other problem is that locomotives are not always used for the service that management may have intended when deciding to place the order.

Certainly, the considerations in buying a GP39 rather than a GP38 advanced at the time, possibly even in "Trains" were that the fuel consumption savings would be traded off against the possibility of higher maintenance costs due to the additional complexity of a turbocharger.

Since then, many turbocharged sixteen cylinder locomotives have been rebuilt for secondary service by removing the turbochargers, giving a medium power locomotive in place of a high power but high maintenance unit.

The turbocharged twelve cylinder was always a minority unit in the US domestic market, but has had a niche role in export markets.

In New Zealand and in Queensland, Australia, entire classes of units with blower type twelve cylinder engines, suitable for the lighter track and smaller trains of twenty years ago, have been recently rebuilt with turbochargers (and larger radiators), giving a 50% power increase for a few tons in weight (which is still critical in those narrow gauge systems).

Extraordinary rebuilds are occuring since privatisation in Britain, where many former Sulzer engined units are being rebuilt with 12-645E3 engines. It has been reported there that more rebuilds would have been carried out but there weren't enough turbo twelves available.

In Australia, 16-645F3s are being fitted in place of 16-645E3s, and these in turn are replacing blower type engines in even older units.

Australian (and British, and South American) clearances and axle loads don't allow the direct adoption of surplus US domestic locomotives, so one possible solution is upgrading by replacing blower engines with rebuilt turbo engines, and enlarging the cooling system to suit.

Another Australian rebuild uses just the frame and trucks from an ALCo engined unit, where the 2000HP 251C is replaced by a GE FDL-12 rated at 3000HP (removed from former Conrail C30-7 units).

I think the point that I'm trying to make is that for a number of reasons, the availability of good used locomotives of relatively recent design and construction, as applies in the US Domestic market, does not apply elsewhere. As a result, the very reverse is occurring with some locomotives, where a blower is being removed and replaced by a turbocharger, to make an older locomotive suitable for the more strenuous conditions now applying.

In this case, EMD's engine, with the ability to rebuild it for further service, (and the ready supply of rebuilt engines and replacement parts) is reducing the penetration of GE in financially stretched export markets (even with the exceptional case I mention above of the ALCo to GE rebuild).

Anyway, thats the view from down under, I guess!

Peter

[Anonymous]

Mark and everyone else, the turbo soakback pump supplies the turbo with oil during fuel priming and after shutdown it runs for 5 mins. It basicly keeps the turbo from cooking the bearings with the excess heat.

[Allen Jenkins]

Yes, but my Pulling For You! GP40's were in the shop in the mid seventies just short of their french grey paint jobs from catastrophic turbo failure, and my road bought in to the utility high horsepower competitor. Hot doggin', wild catin' what was it? Stock holdings? Competitive demographics?