200Tdi Rev Limit

Both my 200Tdi's seem to have a rev limiter at 4500rpm. Wether deliberate in the injector pump or accidental I don't know, but it certainly won't rev past 4500

Alex

Of course they have - it's called a governor and all diesels have them. Very much intentional and certainly not accidental. In this case it's inside the pump.

The 'throttle' pedal on a diesel is a speed control. This compressses a spring which is balanced by forces created by rotating governor weights. You should therefore get a constant engine speed at each pedal position regardless of the load on the engine (within its capability). The governor allows more fuel to be injected when the speed is lower than than intended and cuts it when higher. There is a mechanical stop which limits the maximum speed that can be set - it is this limit that you recognise.

There is a second stop on a diesel which limits the amount of fuel that can be injected. This limits the power output and controls cylinder temperatures, smoke etc..

I tried to find a nice article which explains these things and failed pretty comprehensively but this has some reasonable pictures and explanation halfway down the page at the heading 'Diesel Distributor-Type Fuel Systems':

Thanks.

The reason I asked was that I could have a rough idea of what the maximum revs on no-load condition would be to see if the tacho is reading right or not.

If there was a governor/rev limiter, if I knew what that was set to, at least I would have a rough idea.

Cheers

Peter

Your reasons were fully understood. Most of the comment was for Alex.

I think that Alex has given you the answer - his figure sounds about right. It's probably close enough to allow you to sort out your multipliers.

The governed speed may have been set differently for the Disco/Defender versions. If no-one here can provide a definitive answer your 'friendly LR dealer' or a Bosch fuel injection place should be able to help. Arm yourself with the engine number and any numbers on the fuel pump itself if talking to Bosch.

In message , Alex writes

Speaking from experience it certainly will if you accidentally put liquid propane through a regulator designed for vapour take off and introduce the output into the air intake !!!!!!

You can tell when it has reached its limit by the loud bang :-(

If you have a copy of RAVE then the data should be in there. I don't have the 200Tdi manuals but the max engine speed for the 300Tdi is quoted as 4600rpm (+40/-120). Idle is 720rpm (+/-20).

HTH

IMHO 720 seems a little low for the 300tdi, I wound the idle up to nearer 850, it was a lot less lumpy at idle.

Alex

Interesting - so I could supercharge my Tdi with a bottle of propane?

Alex

On or around Wed, 22 Apr 2009 17:52:57 +0100, Alex enlightened us thusly:

Yes, but if you do it wrong you'll blow it up.

It's called fumigation, been done for years on and off.

the trick is accurate control of the gas supply. Too much gas and you get it to over-rev rather impressively, for not very long.

I don't have an opinion on the figures ... just reporting what it says in the manufacturers workshop manual :-)

In message , Austin Shackles writes

No problem as long as you have a fuel cut off mechanism. My problem arose because we got liquid past the critical point which meant the cut off was ineffective.

Yup - that's what I did with mine and it was quite impressive. You need a very small mixer inserted into the air stream. Normal mixers use on petrol engines are too large. You can use a vapour take off tank and regulator but beware especially if you go off road cos if you get liquid into the system you will suffer the same fate as me. so I would recommend using a liquid take off and a normal small vaporiser.

Initially we controlled the low speed switch on/off with a micro switch mounted on the throttle arm on the pump, but them we went for a pressure switch on the turbo output. We used a propane flow meter to set it all up and accurately adjust the amount of lpg going in.

You can now get much more sophisticated (expensive) systems than the way we did it. But don't believe all the claims about economy.