Project Gemini - Naturally Aspriated version of 200TDi?

[twodoorgaz]

Under project Gemini, Land Rover allegedly planned to build petrol, N/A diesel and turbocharged versions of the "200"-series direct injection engine. In the end (due to its vast superiority) only the turbo-diesel survived and became the 200TDi which we know and love.

However, if they had put a N/A version into production, I'm curious as to what differences there would have been between this and the TDi? Clearly, like all LR engines there would need to be some degree of parts-sharing between the units.

Really I'm looking to identify all those parts of the 200TDi which have been optimised for forced-induction so that, in building a new engine, one could (by carefully choosing different diesel engine components from the Land Rover parts bin) build a true naturally aspirated project Gemini engine.

Obviously I'm aware that the "200Di" (a 200TDi with the turbo removed) has gained some degree of popularity in Series Land Rover circles, though this is very much an adapted turbo engine. If Land Rover were to have optimised this engine for natural aspiration on a large scale - what changes do you think they would have made?

• A new exhaust system and manifold would be needed, both to remove the turbo mount and also to optimise for the breathing characteristics of the different type of engine (a good exhaust manufacturer could make this based on the 2.5 NAD system, for short run production, a tubular manifold could be made, large scale would be cast steel).
• Inlet manifold... I'm not sure on this one. The discovery 200TDi engines, and all later 300TDis feature a beautiful aluminium (?) inlet manifold - clearly this is expensive to produce. Am I right in thinking that in the absence of a turbo, a standard four branch manifold would be more than sufficient - like the one on the Defender engine albeit without a turbo?
• The compression ratio could stay the same (it is 19:1 - other manufacturers have maintained the same compression ratio in similar engines between their N/A and forced-induction engines, the example I have is the ford transit 2.5 Di engine).
  • ...which means that the compression chamber could remain unchanged (no work to the head) and the piston shape and size (offset-bowl pistons) could remain the same - Though I'm not sure if changing the pistons for a different type would benefit the engine.
• Crank and con-rods are plenty strong and the throw need not alter so could remain unchanged. I can't think of any way that these would change between a N/A and turbocharged engine.
• It has been said that the blocks of 200TDis are similar to outgoing models, but they have different part numbers - again, I can't think of any way that these would change between a N/A and turbocharged engine.
• Timing? I would like to see a chain on a simplified engine, but not sure if NAD parts are interchangable with TDI.
  • fuelling and timing would need to be properly set-up on a dyno.

Fundamentally, to do the job 'properly' and build a properly-engineered 2.5 N/A 'direct injection' engine - I think it would be just a case of starting with a TDI, fully reconditioning it, producing an appropriate inlet and exhaust manifold and putting the unit on a bench dyno to set timing and fuelling correctly.

Sorry for the brain-dump but this has kept me up all night. Anyone have anything they would add ti this setup?

[Maverik]

Sorry for the brain-dump but this has kept me up all night. Anyone have anything they would add ti this setup?

HAHA oh dear, I thought I was bad...

Whats you getting at here out of interest?

Mav

[western]

to have absolute commonality of parts, LR would probably just left the turbo off the TDi as we know it, that variation has been proved to work quite well in Series LR's as you've mentioned.

plus a lot of 200tdi internals are common to the older TD engine,

[Retroanaconda]

What's the benefit? All you'd have is a slightly less powerful engine surely?

[twodoorgaz]

HAHA oh dear, I thought I was bad...

Whats you getting at here out of interest?

Mav

Hi Mav.

I am ready to build an engine for my rolling chassis. I'm really excited about this and have been devouring books on engine blueprinting and nagging my local engine machine shop for insight and advice. Going to this level of detail and given that I have yet to order my wiring loom or cooling parts means that I have relative free reign to build something a bit special. I also think it would make a great build-thread for the forum.

I have, up to now, been looking at building a 2.5 NAD dressed to look like a 5MB 2.25 diesel. This is my foundation and I've beem getting some great advice on this over in the Series forum.

However, the dream is to build a land-rover based diesel engine which would produce similar power to a 2.25 petrol (I categorically do not want any more than 130 lb-ft running through the drivetrain), be bomb-proof in terms of long term reliability (250k mile lifespan) and return frankly amazing fuel economy (circa 35mpg).

I had always discounted this as a pipe-dream but it now looks like this dream is achievable - 200di engines tick these boxes but the conversions I've seen have been a bit hurried - the trick is making sure that I haven't overlooked anything and I get a bit obsessive about efficiency - not MPG, but rather ensuring that the engine is running as cleanly and easily as possible (power and fuel-economy are a by-product). Hence me trying to put together a 'formula' for this engine in the same way that Land Rover would have done it.

Regardless of which engine I go for, I have already made arrangements for the engine to be mounted on a bench-dyno and set up to perfection.

Massively OTT for a Land Rover, but this is as much an exercise in engineering as anything else.

[twodoorgaz]

What's the benefit? All you'd have is a slightly less powerful engine surely?

Hi Retroanaconda - yes, exactly. A 2.25 petrol has plenty of power for me - and will muster all the speed I need (though a 2.25d would not cut the mustard) and the drivetrain has been proven to this level of torque over the last 50 years. The 200 'di' set up will offer similar power and torque but with the benefit of a diesel torque curve and massively improved fuel economy (35 vs 22 mpg). I would have absolutely no concerns whatsoever that I had placed additional strain on the drivetrain and would feel comfortable keeping all other areas of the vehicle standard (applying the KISS principal here).

Many, many people can not understand using a TDi without a turbo, their key (and valid) argument being "why go to all the effort of an engine conversion for virtually no power gain?"

I can understand this point, however I am not doing an engine conversion - my car has no engine, nor a wiring loom or fuel lines. As such, I will be sourcing and rebuilding an engine from scratch and selecting all ancillaries - this makes me the ideal candidate to select the best possible engine setup for my needs (long-term owner covering high annual miles but wanting to keep the feel of a classic Landy whcih I know and love).

I think that if I can make this setup meet the standards I would look for in terms of attention-to-detail, that it may well prove to be perfect.

The argument of 200TDi vs 200Di has been covered ad nausem on various forums and websites - the Glencoyne website covers many of these arguments perfectly: http://www.glencoyne.co.uk/200difaq.htm.

Rather than debating the virtues of one engine conversion over another I'm more looking for specific advice on any alterations during the build of the engine that would optimise its running with natural aspiration over forced induction.

PS I really like your website sir - it has provided a fantastic source of information during my Land Rover projects. Many thanks.

[Daan]

For your use, I would use a 200 tdi, with the turbo, but with reduced fueling from the pump. That is the only way to achieve better mileage and reliability. Basically let the engine run part throttle all the time, rather than full throttle without a turbo. it will last much longer that way as well.

Also run high gearing and good intercooling, that will give you good results I reckon.

Daan

[western]

just leave the 200tdi as LR intended at standard factory settings, mine has been fine over 18 years, no major disasters.

[Phil Hancock]

Hi Mav.

I have, up to now, been looking at building a 2.5 NAD dressed to look like a 5MB 2.25 diesel. This is my foundation and I've beem getting some great advice on this over in the Series forum.

Been there, seen it and done it, its sitting in my 88" and it has helical gears in place of a timing chain. Compared to the 14J in my 109" i prefer the governor characteristics of the hybrid lump as a DPA pump(2.25) is a constant speed governor and a DPS pump(2.5) is a constant power governor.

[Eightpot]

Sometimes it's just nice to have a project isn't it.

Personally I don't think you'll gain much, and practicaly it sounds like you're potentially going to spend thousands to gain a few mpg, which doesn't pay off.

You can get 35mpg out of a TDi if you pump the tyres up, empty the weight out of your car and drive slowly. You can put less power through the drivetrain by simply not opening the throttle all the way. If you want it to look like an old 2.25 engine simply mix old engine old, sand and feathers in a bucket, open the bonnet and hurl it in.

but wheres the fun in all that.

[RustyNissanPrairie]

I see the point, I have a 11J in my 110 (1991 MOD) but fitted with a gas flowed head and massive Donaldson air cleaner. It did pull like a train for a good 6 years and has taken me all over the place. Its now pretty worn though (original 22 year old engine-not a MOD rebuilt one), I was seriously considering rebuilding it but then I happened upon a really low mileage Defender200tdi engine so aim to fit that instead. I like the simplicity of a non turbo/NA engine especially if speed isnt your main consideration.

Its just a pity of being limited to 2.5litre, a nice 4 litre lazy NA would be nice!

[twodoorgaz]

Thank you RustyNissanPrarie.

Yes this engine seems to polarise Land Rover enthusiasts - who fall into two camps:

1) those who like myself who recognise that the vehicle was designed with adequate performance and had transmission, brakes and suspension to suit. This camp see the vehicle as a whole and independant of the owner - I need to know that whether the vehicle is driven by myself or by someone unfamiliar to it that the drivetrain is nicely matched. A 200Di (or any other engine with a similar output, size, ruggedness) would suit this and has the added benefit of delivering that power just a little bit further down the rev range, with the benefits of diesel power [simple ignition and resistance to water] and at a much higher level of efficiency thanks to the direct injection).

2) those, like many other enthusiasts who have an equally valid point of view. This camp see that when going to the bother of fitting a later TDI engine that it would be foolish not to take advantage of a wonderful level of performance and to whom the idea of putting in extra work to actually reduce that power is silly. They know that with a bit of mechanical sympathy and sensible driving that a 200TDi can be run for a long time.

Both valid points - I'm firmly in camp 1.

Quote: "Sometimes it's just nice to have a project isn't it."

Thanks mate - yep a project is always nice.

I'm going to try and push the thread back on topic...

Cost isn't a factor, if you have a look at my post you will see I have already committed to sourcing and building a fully reconditioned engine for the project as it is currently a rolling chassis and came without an engine or wiring loom. After spending around 1000 hours restoring every other aspect of the vehicle, I want a freshly built engine too.

I could source and build something easy, such as a 2.25 petrol, or for little additional effort and cost I could source and build the engine I have described which would be a little bit special, a bit of an engineering project and superior in every way. Either way I will be going to the trouble to find, buy, collect, strip, assess, machine, build and test the new engine so why not take a little extra time to plan and produce a vehicle which I can use every day without bankrupting myself.

I'll be keeping this vehicle for the rest of my life, so a few hundred quid more at build stage is frankly not a factor. I like driving series Land Rovers - warts and all - I'm even comfortable with their performance. Though the fuel saving may seem small (22mpg vs 35mpg) - at 5000miles per anum this is a £500 saving, at 10000 miles per annum this jumps to £1000. I cover somewhere between the two. In series Land Rovers. By choice. And I plan on living for a long time. That gives quite a budget to cover a more efficient engine - as a rule of thumb £900 will allow me to buy and work with my engine machinist to fully rebuild a 2.25 or a 2.5NAD. To do the same with a 200TDi this will be closer to £1600. Cost difference is around £700 - if the difference were double or triple that it would still pay for itself in a couple of years.

As I've explained I'm really, really not looking for a debate on the virtues of the engine or advice on whether such a conversion is worthwhile, merely any technical views on how to optimise the engine for natural aspiration on the engine I've already chosen.

Based on the above posts I'm guessing that I'm correct in my initial understanding that all that would be necessary to fully convert from forced induction to NA would be to: replace manifolds and exhaust with a properly engineered replacement and set the timing and fuelling (accurately) to suit (I'd be going as far to do this on a bench dyno).

Many thanks indeed for your input.

[twodoorgaz]

For your use, I would use a 200 tdi, with the turbo, but with reduced fueling from the pump. That is the only way to achieve better mileage and reliability. Basically let the engine run part throttle all the time, rather than full throttle without a turbo. it will last much longer that way as well.

Also run high gearing and good intercooling, that will give you good results I reckon.

Daan

Hi Daan,

yes this is definately an option, and from an engineering standpoint a very, very good one.

The people who will doing the dyno testing for me have explained that they could easily alter the settings to dial in any level of power I like.

The argument in my head is whether is is worth the complication of neatly fitting a TDi radiator/oil heat exchanger and intercooler only to not really use them...

But it is a valid argument none the less.

[Eightpot]

Well I'll be very interested to see the results when you're finished. I used to run a n/a and wanted to fit a stage 3 head etc to try and get more oomph from the engine, which was woefully slow, but did ok on fuel, usually 30mpg.

Since then I've had lots of TDi's, much more powerful and again around 30mpg.

I installed an Isuzu 2.8 TDi, which I think is a more refined and better engineered engine than Land Rovers - tuftrided, balanced, chrome liners, higher revving, manifolds looked more efficient, and a crossflow design. Again I got 30mpg.

The workload involved in pushing a heavy brick with loads of gears and heavy spinning metal bits seems to level out any efficiency gains between engines in terms of mpg (excluding the petrol engines which were even worse)

Over the last few years I've driven lots of different n/a engined Defenders as well though, usually ex military, and the difference in performance is pretty big. Some are utterly sluggish, and the one I'm using at the moment is equal performance wise to a 19j TD I also have, apart from a slight drop off uphill. So by making one as good as it could possibly be, plus making a few improvements, you would end up with a very driveable engine.

I'd still just pop a TDi in though

[twodoorgaz]

Thanks matey - I'll be sure to report back with an update

[Maverik]

I actually just re-read your thread twice, good to see you've got a solid direction to go in.

With regard to a 200tdi as a base I think you're not going to get any better than that as an engine to utilise as many standard LR parts as possible.

With regard to optimising it for NA running, it might be worth looking into different piston designs as they are optimised for the type of inducted air, i.e turbo'd is higher pressure/denser and the swirl pattern in the chamber needs to be optimised for that...

I'm not an expert but I've done a wee bit of research into it.

But if you're looking at pistons then you should consider the shape of your combustion space which you can't change that easily...

With regard to your exhaust and inlet manifolds... quite an important factor I think, as you now have the opportunity to make a rather sweet optimised manifold with regard to air flow, this factor really shouldn't be overlooked.

When I first read your post I was a little sceptical as to what you were trying to do, but actually you've won me round and rather intrigued at your build

Mav

[Turbocharger]

I don't think there's any disbenefit in running a unit as a 200Di, though you could use the turbo, intercooler etc at a low boost to reduce stresses in the engine. The combustion principles are the same so there's no need to look for different head flows, different pistons or similar - the turbo'd air is just more dense to allow more fuel.

As far as derating the engine goes, just disconnect and blank the boost compensator on the injector pump and it'll fuel it correctly as an N/A engine - though you might be tempted to tweak that later for a little more power, until it begins to produce black smoke.

[Adam001]

Based on the above posts I'm guessing that I'm correct in my initial understanding that all that would be necessary to fully convert from forced induction to NA would be to: replace manifolds and exhaust with a properly engineered replacement and set the timing and fuelling (accurately) to suit (I'd be going as far to do this on a bench dyno).

Many thanks indeed for your input.

Bear in mind that a bench dyno is purely for use for initial calibration on heavily modified engine / new builds. What works on the bench dyno will not be optimised in a car. You need to do it twice, on the bench then on a rolling road....then to be completely accurate. adjust it on the road. All 3 scenarios having very different flow characteristics

[Simon Smith]

I drove my old 110 home without the turbo connected once (who forgot to do the jubilee clips up then?) anyway although it felt sluggish, it was still quicker than my old 2.25 petrol S3 so I think it's perfect for a series LR. Also with the limited space under the shorter bonnet losing the turbo, intercooler and all those pipes would make for a neater and easir to work on engine.

So Im in neither of your groups really, I love the 200Tdi as it is, but also think a well thought out 200D ( I thought the I stood for intercooled) would be perfect for what you want.

[Daan]

The argument in my head is whether is is worth the complication of neatly fitting a TDi radiator/oil heat exchanger and intercooler only to not really use them...

Dont agree with not using the intercooler, it will make a lot of difference for it running lean. effectively, cooler air means more mass, creating leaner mixture. The more lean the mixture is, the better and efficient it will run. Also, the TDI oil cooling system is very good, with a thermostat i believe, and the turbo heats up the oil much quicker from cold.

Daan

[Turbocharger]

But if he's not running a turbo, there'll be nothing heating the air up so no temperature difference to cool it down.

If he's going to run the turbo but at lower boost (probably the way I'd go with this) then I'd definitely fit the intercooler too.

[twodoorgaz]

But if you're looking at pistons then you should consider the shape of your combustion space which you can't change that easily...

With regard to your exhaust and inlet manifolds... quite an important factor I think, as you now have the opportunity to make a rather sweet optimised manifold with regard to air flow, this factor really shouldn't be overlooked.

When I first read your post I was a little sceptical as to what you were trying to do, but actually you've won me round and rather intrigued at your build

Mav

Thank you very much Mav - I posted on this forum due to it having a better level of technical knowledge than other forums. Comments like yours give me the confidence I'm on the right track.

I've been looking into the pistons myself and you have two factors to consider: shape (bowl, flat or domed) and its effect on the volume of the combustion chamber.

The 200 and 300TDIs have bowled pistons - in the 200, the bowl is off centre and in the 300 it is more centred.

The 2.5NAD and 19j engines shared the same con rod and the same crankshaft and had a similar type of piston but the pistons actually had different part numbers

They are shown in the following pictures:

It would be tempting to take the NAD or D-Turbo piston and use it in the 200DI - however... as the con rods are a different part number and the crank is a different part number it would mean either careful measurement to ensure the stroke remains the same as the 200TDi or alternatively swapping the crank, conrods and pistons... getting complex.

Changing the TDi to a relatively flat NAD/19j piston, rather than the bowled pistons would reduce the volume of the combustion chamber which (if I'm understanding this correctly) would increase the compression ratio - something I don't want to do.

I will ask the engine machinist's opinion on this, however I'm tempted to say that it would be best to keep the existing pistons - the existing deep bowl design would keep the same 19:1 compression ratio and would also "confines the diesel fuel spray for good, fast combustion" - at least that's what Google says!

Does this make sense to other people?

I don't think there's any disbenefit in running a unit as a 200Di, though you could use the turbo, intercooler etc at a low boost to reduce stresses in the engine. The combustion principles are the same so there's no need to look for different head flows, different pistons or similar - the turbo'd air is just more dense to allow more fuel.

As far as derating the engine goes, just disconnect and blank the boost compensator on the injector pump and it'll fuel it correctly as an N/A engine - though you might be tempted to tweak that later for a little more power, until it begins to produce black smoke.

Thank you - I'm hoping I'm not building in some inherent weakness in the system by not running a turbo - thanks for the tip on the combustion principals, I have a very limited understanding of this.

Yep - I'll be having the pump set along with the timing on the dyno - I'd like it to run quite cleanly so won't push the envelope for an extra few BHP.

Forgot to say folks - there's a chap in Denmark who has had a used, but well serviced 200Di dyno'd at 76.6bhp - this is absolutely perfect for me - about the same as a 2.25 petrol, though presumably that will come with a little more torque than the 120lb-ft than the petrol delivers. I wish I could see the power/torque curve for this test!

The torque figure I want is 130lb-ft. The most powerful engine used by Land Rover with the 'Series' drive train in a production vehicle was 134lb-ft this was produced by the high-compression 2.6 6-cylinder.

Land Rover did actually use a more powerful version with the SIIA NADA 109 6-cylinder fitted with the Weslake cyl head - this produced 142lb-ft of torque. The NADA was not a huge success - with its huge weight and Rover (non-salisbury) back axle, it was 'allegedly' prone to breaking halfshafts. Indeed Land Rover went on, I understand, to offer a Powr-Lok limited slip diff for the back axle in 1967/8 - reports are mixed, some say this was to improve off-road ability due to the car-derived engine producing power too high in the rev-range, while others say that it was an attempt to strengthen the Rover rear axle (the latter seems dubious to me as surely a halfshaft would give in before a diff).

Anyway... I digress. The point is that if the most torque that land rover put through the transmission without major issues was 134lb-ft, then who am I to argue? Also, this torque would have been delivered extremely smoothly from a 6-cyl engine - not the knotchy delivery of a 4-pot diesel - so I'll roll it back a bit to 130lb-ft.

In a SWB Series this should be plenty - better than anything ever produced by the factory, probably closer in terms of torque to a 2.25 petrol with a stage 1 head.

As such, given that a 200'Di' is already producing the power and (probably) the torque I am looking for, then if I was to fit the turbo and intercooler and then had the fuelling/boost altered to produce the 75-80bhp/130lb-ft I'm looking for, then I would guess that the dyno operator would end up turning the boost all the way off!

In light of this and assuming that the 'Danish' figure is correct, then it doesn't seem beneficial to have a complex intercooler/turbo setup fitted to the vehicle - they would simply be a bit of a liability and would not help me in my goals. As this will be used for long overland travel, surely an ultra simple NA setup would suffice.

(I hope this argument makes sense to other people and not just 'in my head' ha ha)

Bear in mind that a bench dyno is purely for use for initial calibration on heavily modified engine / new builds. What works on the bench dyno will not be optimised in a car. You need to do it twice, on the bench then on a rolling road....then to be completely accurate. adjust it on the road. All 3 scenarios having very different flow characteristics

Thank you sir, I was not aware of this. I had worked on the assumption that a 'bench dyno' was the Gold Standard in terms of engine testing. I may well do both (bear in mind that this project is a bit of an indulgence in engineering and not simply an exercise to produce an old Landy) providing that I don't get to scared to see my new engine revved to the required levels!

I drove my old 110 home without the turbo connected once (who forgot to do the jubilee clips up then?) anyway although it felt sluggish, it was still quicker than my old 2.25 petrol S3 so I think it's perfect for a series LR. Also with the limited space under the shorter bonnet losing the turbo, intercooler and all those pipes would make for a neater and easir to work on engine.

So Im in neither of your groups really, I love the 200Tdi as it is, but also think a well thought out 200D ( I thought the I stood for intercooled) would be perfect for what you want.

Thank you - yes I think its important to imagine the performance compared to a thirsty but lovely 2.25 petrol rather than a TDi.

T.D.I = Turbo Direct Injection in Land Rover parlance (everywhere else in the world I think you're right, the 'i' would be intercooled). So a non turbo is a "200 Direct Injection". Having said that the '200' represented the torque from the original project Genimi engine (195lb-ft rounded up to 200) - so maybe I should rename this engine to a "130Di" just to confuse everyone!

As you quite rightly say - the non-turbo setup could be done very neatly and will afford plenty of space around the engine.

Dont agree with not using the intercooler, it will make a lot of difference for it running lean. effectively, cooler air means more mass, creating leaner mixture. The more lean the mixture is, the better and efficient it will run. Also, the TDI oil cooling system is very good, with a thermostat i believe, and the turbo heats up the oil much quicker from cold.

Daan

Hi again Daan - totally agree, if I were to fit the turbo I would definately use the intercooler (I'm obsessed with reliability). However, as explained above, I don't think I'll need to use the turbo - I'll simply be using a standard Series radiator. Cooling will depend on which engine I choose:

• Defender 200TDI means that, with the right combination of pulleys, I can use a Series fixed fan on an adapted 200tdi or 2.5 NA water pump - it would look fantastic. But, it would mean I would have to cut an engine mount on my galv chassis

• Disco 200TDi will drop straight onto the existing mounts as the timing case is different and moves the injector out of the way... however as the water pump is off-centre and quite protruding (it can't be swapped for a 2.5 NA unit or anything else) the n I would have to use an electric fan. No probs with that, the 200TDi runs very cool and doesn't really need a fan - the electric one would be there for heavy towing/hot weather and may reduce fuel consumption/noise a touch. Disco engine's also cheaper.

But if he's not running a turbo, there'll be nothing heating the air up so no temperature difference to cool it down.

If he's going to run the turbo but at lower boost (probably the way I'd go with this) then I'd definitely fit the intercooler too.

Yep - nailed it - no turbo = no intercooler, fitting a turbo = intercooler too.

Really appreciate all the replies folks - there's a wonderful level of technical knowledge lurking in this forum!

[Retroanaconda]

Is the different piston design to do with the direct injection on Tdi models as opposed to indirect injection on N/A engines?

As far as I'm aware that's what makes the Tdis so noisy compared to the N/A as well.

[western]

combustion chamber on a tdi is in the piston, as it's a direct injection engine, whereas the TD is a indirect injection & the combustion chamber is within the cylinder head, thats why the pistons are different.

[Simon Smith]

Agree with western, You cant use TD pistons with a Tdi head, it would give you about 500:1 compression ratio at least I would use the Tdi engine as it is standard.