Oil Burners - the great diesel debate!

With the increasing cost of fuel, it has to be said that diesel power makes a lot of sense, and with today's diesels offering a lot more in terms of power than before, with high torque to boot, then it's not surprising to find that there is a BGT in existence with a diesel powerplant.

First, though, the choice of diesels from the family is limited although the B series did appear as a diesel variant for commercial vehicles, but all that changed with the launch of the of the Perkins unit in the Montego/Maestro in the late 80s.  Essentially, as with the B Series, Perkins worked with Austin Rover to develop a diesel version of the O Series which became known as the Rover MDi or Perkins Prima unit. The engine was a ground breaker being one of the very first to get direct injection.  The Montego and Maestro in some instances got this in turbo form with a higher 80bhp output and the engine has become popular with the Land Rover owners wanting to replace their diesel units with apparently a more reliable and powerful engine.

The L Series was introduced in 1995 and has been the staple of the product range since, with development of the G Series very close to completion last year at the time of the MG Rover closure.  This engine was used in the Rover 25/45/Streetwise and MG ZR/ZS.  It offered 101Ps @ 4200rpm and a stonking 240Nm @ 2000rpm, the torque value being the same as the 2.5KV6 engines.

Having recently purchased an LDV 200 minibus, I am now more familiar with the Prima engine and I have to say that so far, apart from being a bit noisy, it is a work horse and will apparently keep going and going and going...and has many fans on the various LDV forums.

Obviously I could not help but think with its O Series roots the likelihood of it fitting a BGT engine bay had to be good.  So I emailed Roger Parker again to ask what options I had to upgrade the diesel in the old bus - as usual, Roger's answers are worth repeating here!  However, where Roger refers to the LDV the same can be said for the MGB and fitting the L Series Turbo would be very similar to fitting the T series Turbo.

"The diesel was developed in a turbo and non turbo form with the non turbo being common in the Maestro vans and saloons, with the Turbo version being standard for later Maestro cars and almost all Monty saloon and estates. The turbo engine developed 100bhp, the same as the revised L series that arrived in 1996 and was a leading edge engine still at the time with staged direct fuel injection and fitted to the then new bubble shaped 200. The L series features more electronic control, but it is still essentially the same engine and by modern standards is as distant from the modern standard as the B series diesel was from the L series. There is absolutely no connection to Peugeot 1.7 Turbo and 1.9 turbo and non turbo engines used in the XW series of Rover 200 and 400 cars.

The L series is still pretty much an O series so as far as I am aware will bolt into where an O series previously sat, be that petrol or diesel. Ancillaries is where any difficulties would occur and I know too little detail on that front to be accurate, but feel that most of the ancillaries were packaged in a similar way so there should be room.

100 bhp (240nm) spec L series is reasonably sweet running but the 112bhp (260nm) version from later has a more peaky feel as the difference between on and off boost power delivery is more marked. It is also quite noticeably harsher for the extra 12 bhp and 20nm or torque. Some years ago I did see a genuine 160bhp development engine running on a test rig in JE Developments in Coventry. It was a still born project to create a racing diesel engine to go into a Lotus 7 style chassis for a specific series, but the rules changes and it was dead. The bottom line though was that the engine was as rough as an old dog with such a tune level and the best set up point they found was around 125bhp, and around 300Nm torque that was done to an employee's R200, still harsher than standard, but quite acceptable and made for an indecently quick 200!

Take the lead from that and if you go diesel, and being as you can find L series back to 1996, restrict to that sort of level. The fitting of a gearbox should be much the same as with a petrol O series, and as the hole in the end of the O, M and T petrol and the Diesel cranks is huge there is really no issue in having a bush made to suit the input shaft size.

I have some extended experience with MAFAM from Rover Ron on a pal's 2000 75 diesel, and the results have been marked. This was a 116 bhp motor which we fitted with a MAFAM and also a TuneAM module for the common rail at a time before MGR crashed and just after I went to Scotland with an MGR press ZT 135 CDTi. The MAFAM spread the power band noticeably, just as described in Ron's web site, and the TuneAM set mid way seriously boosted the power. Some three years on and many, many thousands of miles the car has lost none of the extra zip, did not lose economy, retains the marked increased performance and has not broken down. One aspect of the changes was that the engine actually revs more freely and 'feels' as though it wants to go, rather than having to crack a whip to get response.

I have known of diesel MGs for a long time and figure the BGT with the B series diesel is the one by the father and son from Gloucester/Somerset way (See below for more info - Martin). They were looking at going O series diesel as I have spoken with them on a couple of occasions, and said to them that this would be a conversion that would give credibility to a diesel as the B series diesel does not give credibility to a diesel MGB except when able to drive past many filling stations before needing to stop. However the efficiency (or lack of it) for the B series diesel means an M or K series converted MGB can equal and in some instances beat the economy of the B series diesel engined MGB, an L series conversion at least provides 14bhp and nearly twice the torque of a standard B series petrol engine, so should provide the required performance boost.

Gearing is as critical to the driveability as the torque numbers and how it is delivered. You have to match them all to suit the performance profile of the vehicle your creating. The Sherpa is given short gearing in 1st to 3rd to allow it to climb hills in a laden state, indeed an over laden state as they knew that the likes of builders would look at loading the space even if the weight of the load was over the top. Reduce the weight the vehicle has to carry and you can work out what the optimum gearing needs to be and balance that with an ability to be able to cruise at comfortable speed with no need to change down at every incline just to maintain speed.

Having the wider torque curve is equally important to this equation and why in many respects modern diesels have to have a six speed gearbox as they do not have the rev range to deliver that balance of performance and cruising ability. The R380 in a Sherpa format will have these lower first three ratios and whilst I have used one with an MGB M16 conversion where the rev range and the torque band was wide enough to mask the negative effects of the gearing a narrow rpm band diesel may not and so a saloon car (Land Rover/RV8/etc) set of ratios would be better.

Roger Parker"

Thanks again to Roger's considered and very informative answers and again a good reason to join the MGOC to tap into his knowledge!

NB: Since writing the above, I have discovered that it is not as easy as first thought!  A relocation of the turbo is required!

However, for an article showing the fitting of the L Series into a BGT see here.

And now for something completely different...

Featured in totalMG in October 2004, the story of the upgrade is that Paul Gaster  (aka Madgasters to the online forum community) and his father fitted a 1.8L B Series diesel engine from a Sherpa van mated to the original box.

I believe, according to a forum post last year with photos (see below) an update is in the planning!

Hopefully Paul will provide more detail in the near future.

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