Theoretical exercise RRC engine swap

[Mercguy]

Let's start with a few basics before I launch into a monologue....

1. Oct 1991 build RRC 3.9 v8

2. BW viscous xfer case

3. Standard differentials.

OK.

the Theoretical Challenge is to devise a list of required modifications to enable te fitment of either a diesel (turbo) inline 6 engine or a larger displacement OHC v8 from another manufacturer - in this case Mercedes-Benz.

engine #1 is well known in diesel circles as OM606. I also have access to OM603's but would prefer the DOHC.

engine #2 is high compression 5.6L M117 SOHC petrol engine. Known to be almost indestructible and makes reliable power. Can be supercharged without messing with internals.

The theory behind the swap is simply to improve low end torque and fuel economy.

The existing 3.9L v8 is a bit of a gutless wonder I find. It always needs encouragement to go up hills on the legal highway speed limit, and often drops 10-15km/h if the throttle application is not correctly timed or sufficient - or for example when you have less than favourable traffic in the left lane and you need to get past going uphill and towing a small boat.

So I have a spare v8 Mercedes engine, and it's a good'un, but my concern is simply whether the ZF and BWTC can handle the extra torque.

I can access an OM 606, but dimensionally I have concerns about the length and engine bay fitment.

I have seen the TDV6 swap in P38A, but I am not interested in common rail piezo injectors. If I run the OM606, it will be with a modified 603 pump, possibly with 7mm elements just to enable a little more boost without worry.

So after the basic bits - getting engine mounts sorted, bellhousing adaptors etc... I have to wonder if the auto and transfer case will take the punishment... and if they can, then what about the axles & CV's?

These are the things I am not sure about. So feel free to throw in some ideas or if you have information to add, please do.

Right now the swap is theoretical only. the 3.9 is working fine, albeit with a thirst and not a great deal of mumbo. I can live with that for now.

So feel free to add your suggestions.

[loanrangie]

I have been drooling over some of the om606 lr conversions on some of the uk forums, they fit in a defender so an rrc should be ok.
Auto would be ideal but i think you would have to use zf hp24 for it to last, from my little research the om606 is no easy to find in oz.


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[Mercguy]

For me sourcing a 606 is a doddle. It's pretty much the least of my concerns, however they are becoming increasingly sought after, so it makes them more and more expensive these days.
an OM603 would still be okay, but for that kind of swap I'd rather drop the v8 in.
Done the m117 into a Gwagen before so not worried, but since I'm an RR novice so to speak, I think the concerns for me are whether or not the ZF auto will last, whether the ratios are any good for a 5.6 v8, or if I should utilize the bulletproof 722.6 mercedes auto and programmable shifter.

Then I guess it would simply be easier to have bought a Gwagen instead, so perhaps just a 606 would do for the moment.

The BW transfer case is a concern because I do not know how much power it can handle or how good they actually are.

diffs / cv's I can live with until I learn some more about which are strongest and whether or not I swap out whole axle assemblies or just gut the internals.

I would like to do something about wheels & tyres down the track, so one of the key criteria for the swap will be if I can run a nice 33 or 35 MT or centipede etc and 'try' to keep it stock looking.

[loanrangie]

I would ditch the BW for an LT230 then there are no concerns, HP22 wont last long with 250 plus HP going thru it which is why i mention the HP24 even though it will need an after market controller.

If you look on LR4x4 there are a few OM conversions.

[Mercguy]

I think if I were to pursue the OM606 route, then I would be utilizing a 722.6 transmission, not the ZF. Mostly because I am extremely familiar with the 722 series MB transmissions (and they are pretty much unbreakable if fluid & filter service intervals are followed).
If I go with my spare m117 5.6, then the 722.323 that sat behind it would be utilized, - All MB transmissions can have the valve body modified (remove a couple of check balls and springs) to have manual lock out in gears and also the 1st gear start (most 722.3/4/5/6 transmissions start in 2nd gear for sedan applications)
the only major differences between the sedan transmissions and the Gwagen (w461/463) are the depth of the sump on the trans pan (identical bolt pattern, just deeper) and the manual gear lock modes.
Of course, using one of these means the transfer case must be divorced from the rear housing. I'm not entirely sure it's a good idea, but it does complicate things further, in terms of mounting etc. It does provide some alignment freedoms, but I have seen this become more of a problem than a boon in the past.
Another issue seen with the 5.6 swap, is torque loading.
In the 'G560' (was a 280GE) the amount of torque at idle loaded up the drivetrain in the G, so that holding the brakes and applying the tiniest amount of throttle, compressed the suspension by almost 4" of travel. Of course, G's have incredibly short diff ratios, and this was the primary cause. Burnouts however, in 1st, 2nd and 3rd gear were just a matter of applying a decent amount of wellie.
1st gear was deemed too short for anything but quite serious offroading, and low range outstanding. The vehicle really needed a set of 35" tyres, but it wasn't mine... so it remains to be seen how the owner contends with the short final drive issue.

I like the idea of the viscous coupling, but understand the issues it comes with, but it's nice to have fulltime 4wd. an LT would obviously change that.
I have fitted quaife ATB centres to my MB's before and would think that this would be an ideal alternative to an open centre transfer case, but again, I do not know the strength of the LR parts, or what needs to be done to achieve that 'bulletproof' reliability.

The main issue I have with contemplating the swaps, is simply turning the vehicle into a bastardized unit. I see many conversions, LS's Cummins, duratechs etc... they all have their advantages, but they also come with a number of penalties that owners either persevere with or become frustrated with.

So while I simply have a single issue with the 3.9 in that it is a gutless wonder and drinks like a sailor, I can live with it, as it is simply a fuel consumption issue.
Mind you, I never had the same feeling in my old GQ, or even the old 78 series utes I used to drive (loaded with 2 tonnes of equipment) - and yes, the tojo was the 4.2 diesel.....

So, will the 606 be worth it? possibly. certainly has the torque and power spread to make the RRC get up and really boogie, with the added reliability of the inline 6 mercedes donk. But I do wonder...... is a diesel conversion actually worth it, when outlay versus consumption over say... a 5 year period of ownership is concerned.

To give you an idea of consumption..... I'm currently hovering around the 20L/100km without trailer attached and about 26-28 with. I do mostly highway work, and find that 4th gear is a waste of time with the trailer, except on flat pavement. It's actually not much different without the trailer in that respect, and I would opine that the 3.9 wouldn't pull the skin off a rice pudding when really trying to get it moving from 90km/h upwards. That includes kickdown etc. it just revs and doesn't accelerate, especially uphill where it even loses momentum under kickdown - especially at around 90-100km/h. If this is normal for an RRC, then fine, but I would expect some form of acceleration with the kickdown from 4th to 3rd (and sometimes 2nd?) when the momentum drops like a stone.

So yes, I think a 606 or 117 would be an instant cure for that. however, in my old lwb 560SEL the fuel consumption was around 14/100 and if driven really hard, about 17/100. In the SL, the consumption is between 17-22/100 because I drive it very differently (and it is a lighter car than the w126)
interesting to note though.... in both of those cars, the transmission ratios are identical as is the final drive (2.47:1 - tall) and yet it is exceptionally well balanced between outright acceleration and cruising efficiency - something the Gwagen never was (arguably still can't - look at the 6.3 consumption figures these days) designed for anyway.

and the 2.02tonne RRC is right there with the w126 - while the 126 is a bit lighter, It's not about the weight. it's about the torque that the m117 v8 provides so low in the rpm band. and with the redline of 6500 (and believe me it will get there very quickly and easily) the spread of power is good. downside? fuel consumption.... it would probably end up being around the same 20L/100 as the 3.9 - but perhaps more importantly, the torque would be much better and the acceleration would make the car more driveable.

So yes, it's still theoretical still. But perhaps there are other engines which are cheap, reliable and have maybe 'better' fuel consumption and good torque figures, and are more suited to swaps...

And I still haven't contemplated the idea of different transmissions.... I'd like it to stay automatic, but certainly wouldn't rule out a manual..... it's simply going to depend on what is easiest to mate to the donor engine.

I think we'd all love a 7 speed semi-auto and a double low range, but i can't forsee that as being a viable proposition... I'd have to find some portals and a set of 35's to make something like that work..... and then how useful would the car be as a tow vehicle? hmmm

[Scouse]

To give you an idea of consumption..... I'm currently hovering around the 20L/100km without trailer attached and about 26-28 with. I do mostly highway work, and find that 4th gear is a waste of time with the trailer, except on flat pavement. It's actually not much different without the trailer in that respect, and I would opine that the 3.9 wouldn't pull the skin off a rice pudding when really trying to get it moving from 90km/h upwards. That includes kickdown etc. it just revs and doesn't accelerate, especially uphill where it even loses momentum under kickdown - especially at around 90-100km/h. If this is normal for an RRC, then fine, but I would expect some form of acceleration with the kickdown from 4th to 3rd (and sometimes 2nd?) when the momentum drops like a stone.

If you're getting that sort of power/economy out of a 3.9, there's something seriously amiss. The air flow meter has been known to cause similar symptoms.

[Mercguy]

If you're getting that sort of power/economy out of a 3.9, there's something seriously amiss. The air flow meter has been known to cause similar symptoms.

The AFM is clean as a whistle and working fine. there's no nasty purging of unburnt fuel or smell of rich running, Afaik, it was chipped according to Wade/Stuart. It's been serviced at Graeme Cooper's for the last 11 years prior to my purchasing - just over a month ago. It has no idle issues.

I live in a hilly area on the south coast, not far from Baz (or you actually) and the 20/100 is what I was told to expect by other forum members, and I can live with that. Towing the boat down from Qld netted me around 28/100. I expected something in the vicinity. This model has no O2 sensors fwiw.

The reason for the contemplation of the swap is primarily to reduce the consumption and increase the torque / power output.

the M117 v8 is good for 220kW and about 410Nm and a fuel economy of between 17-22L/100 when being pounded hard. in the 2.6tonne Gwagen it gets 20-22 with the short final drives, so I expect a fraction better if I were to swap into an RRC. However, the OM606 will provide more torque and lower in the RPM range, and the 5 speed auto works well with programmable shift. The issue with an MB engine swap is the transfer case being divorced from the transmission, thus creating extra annoying issues. And if push came to shove, then I'd probably ditch the BW and go for a VG150 from a w463. All in all, by the time that was done, I'd probably have been able to buy a 460.... Conversions are never cheap things to undertake.

I do have an opcon MX422 twinscrew supercharger here, but somehow I do not think a 3.9 engine would take 10psi of boost without heavy modifications.

would provide the extra torque though....

[Scouse]

The only time I've ever come close to 20l/100km is towing a loaded car trailer.
Normally it was around 14-15l/100km from my 3.9 RRC & never a complaint about performance - I reckon it'd leave our 4.6 P38 for dead.

[BigJon]

I like the idea of the viscous coupling, but understand the issues it comes with, but it's nice to have fulltime 4wd. an LT would obviously change that.

LT230 transfer cases are still fulltime 4wd. Just with a manually lockable centre diff, rather than a viscous coupling.

[Mercguy]

Yes, You are absolutely correct, and I was not very eloquent in my explanation of what I meant, and you have correctly explained what I didn't correctly explain. Thanks

Yes, I was referring to the viscous lock-up versus manually locking.

I also see that the LT has options.... ratio options, ATB centre diff options...

I see this as a good thing. like the VG150 is also a good thing in the w463.

But the day before yesterday I started looking at the Atlas 4 speed transfer case and just ummed and arred.
double selectors and hi-lo really got me thinking, except it's missing the most important thing.... a torque biasing centre differential gear.

Sure, it has advantages (locking each output shaft separately) but it has 2 achilles.... like we do!

1. cannot shift the 4 speed on the fly (i.e. below 5mph rolling) as there is no synchro
2. no centre differential - rather the expectation is that it is for locking the output shafts only, and that means not suitable for bitumen use in 4x4 mode.

I cannot think about the effect that wind-up would have on the atlas, quite possibly it would be minimal, and the driveshafts would all simply explode one after the other? It does look like an absolutely ripping unit for 100% offroad use.

I wonder what it would be like in rwd only.... because everyone's opinion that I have read, is that the Range rover was designed as an FT4wd and as such, taking drive away from the front wheels results in horrible handling traits....

I sometimes wonder if people who say these things speak from experience, or if it is conjecture. Perhaps they never drove a manually locking hub vehicle before, or maybe they have experienced extreme loss of front end grip as a result of having only rwd, and being completely used to the behaviour of a FT4wd unit?

anyway, that's slightly OT, but still relevant.

Also starting to look in more detail at axles & suspension. I'm looking at 33" road tyres at the moment. would love 35's but do not see the value as I'm not heavily offroading it at the moment.

The diesel versus petrol argument has effectively been settled. While I'd love an OM606, I already have the m117, and know it's in fantastic shape. I'm thinking about gearboxes & transfer cases. I have a 4 speed 722.3, and know it would be fine as far as automatics go. final ratio is 1:1, so that leaves calculations for transfer case and final drive to be done, so optimal operating rpm can be established.
This is where the 33/35" tyre discussion swings in, to either hinder or aid in the final operating rpm.

I'm starting to think that Defender owners have the best of both worlds when it comes to modifications.

but an RRC with 35"MT Bajas would look kickarse. And if I did the v8 swap 'amg-style' with some side-exit pipes for ****s n giggles I think it would be a real laugh to drive.

I'm amazed at how much room there is and how little needs modification to make it all work... and it seems the weight penalty overall will be very little.

so it looks like I need to make some tough decisions on the transfer case and transmission. which means I need to work out what to do with tyres, which means I need to look at suspension / flares / lifts / axle assemblies...
geez. talk about biting off more than I can chew right now....