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P38 engine swap ideas/experience. TDV8 maybe?


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Bit of a back story. I’ve had a 4.6 P38a for a number of years. And while it often annoys the hell out of me when things stop working on it. I do very much like it. 
 

However I’ve been seriously contemplating replacing it with a supercharged Range Rover Sport. Although covid has created havoc with prices (also looked at TDV8’s). Step forward a bit and I used my Uncles L405 TDV8 full fat Range Rover for 550mile for a trip to Wales and back. 
 

I have discovered that as great as it was. The newer generations probably aren’t for me. Far too car like to drive with high window lines and enclosed interiors. Much to my surprise I prefer the p38. I know I don’t have as many gadgets and modern tech. And way less power. 
 

The 4.6 in mine is a Thor and runs great. Been on a dyno and making all of its rated horse power. That said a bit more poke would be welcome, it always is. 
 

But it’s the mpg or lack thereof really. I’ve been doing some off roading recently and the readout is currently 12.1mpg!!! It’ll normally return about 15mpg for my local use. And will just about creep up to a max of about 19-21mpg on a good run. 
 

The 4.4 TDV8 returned 32mpg with ease. Which makes me wonder. How feasible or easy would it be to get one of these engines running in a p38? Or would it be better to consider something like the BMW M57 6 pot?

Open to suggestions/advice or if you know someone who has done something similar. 
 

The RV8 is an awesome engine. But there is no denying the real world mpg is certainly a heavy expense with current fuel prices. 

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I think there will be 2 major hurdles to your idea

1 - Getting a TDV8 running outside of its host car. I know Bell Auto managed it with a TDV6 but I don't know of anyone who has managed with the TDv8?

2 - The TDV8 is quite a high engine and as a result of this the RHS front drive shaft actually goes through the sump. With a beam engine P38 that obviously won't be possible

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Sounds like a fun enough project. But won't be easy.

18 hours ago, Chicken Drumstick said:

The RV8 is an awesome engine. But there is no denying the real world mpg is certainly a heavy expense with current fuel prices. 

I think you'll be able to buy a whole lot of petrol for the price of the conversion...

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So comparing CD's experience of a TDV8 on a run = 32mpg with P38 4.6 on a run = 19mpg with fuel costs according to the RAC @ 1.89 for petrol & 1.97 for diesel... over 10k miles that's £1700 saved, which feels like not as much as the cost of a conversion by a long chalk.

Not sure what would happen to those numbers off-road, and not sure about the maintenance costs.

Maybe @Ed Poore can shed some light on the TDV8 ownership experience?

The P38 that donated its 4.6 to our ambulance claimed nearly 24mpg on the drive home, which surprised me, but even in the ambulance it can happily hit 19mpg on a motorway run and that's not hanging around behind trucks.

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I have run my 4.4TDV8 L322 for 6 years and near enough 60k miles and my real MPG (not the porkies the car tells you) is typically in the 25-27MPG range. I don't drive it like I stole it but I I do make full use of the engine's power and make sure both turbos get a regular workout :) 

I think unless you get given a known good engine and have access to spectacularly competent auto electrician who will give lots of time for free then I can't see the maths  (even man maths) working for a conversion on fuel economy grounds.  😕  Even then, you might need a power bulge in the bonnet to fit it in over the axle as has been said.

The other thing to consider is what will you put behind it? The 8 speed ZF box is fantastic but not sure the P38 will have space for it?

Having written all that, have you driven an L322? Very different beast to the L405. Replacing the P38 with an L322 might be your best bet ?

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2 hours ago, bishbosh said:

Having written all that, have you driven an L322? Very different beast to the L405. Replacing the P38 with an L322 might be your best bet ?

Whilst I think a TDV8 in the P38 would be a fun project I think this probably hits the nail on the head. I have had the older 3.6 for 7 years and my old man the 4.4 for the same amount of time. The 4.4 is certainly the better one to have as there is more power but also better economy due to the extra two ratios in the box. Big diesels suit the L322 really well and I prefer our diesels to the old petrol L322 I had. 

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3 hours ago, FridgeFreezer said:

So comparing CD's experience of a TDV8 on a run = 32mpg with P38 4.6 on a run = 19mpg with fuel costs according to the RAC @ 1.89 for petrol & 1.97 for diesel... over 10k miles that's £1700 saved, which feels like not as much as the cost of a conversion by a long chalk.

Not sure what would happen to those numbers off-road, and not sure about the maintenance costs.

Maybe @Ed Poore can shed some light on the TDV8 ownership experience?

The P38 that donated its 4.6 to our ambulance claimed nearly 24mpg on the drive home, which surprised me, but even in the ambulance it can happily hit 19mpg on a motorway run and that's not hanging around behind trucks.

Thanks and I concur.

Although if being honest, for the same journey that the TDV8 got 32mpg, I think the p38 might be more like 17'ish. I know the RV8 can in some scenarios be ok on fuel, but an automatic, lifted suspension and MT tyres certainly knock it back. And running about non road trip usage it really is 15mpg or under. Don't really know what the TDV8 would do in this scenario, but I'd suspect more like 26-28mpg. And that's with the TDV8 in a vehicle that weighs quite bit more than a p38.

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18 hours ago, L19MUD said:

I think there will be 2 major hurdles to your idea

1 - Getting a TDV8 running outside of its host car. I know Bell Auto managed it with a TDV6 but I don't know of anyone who has managed with the TDv8?

2 - The TDV8 is quite a high engine and as a result of this the RHS front drive shaft actually goes through the sump. With a beam engine P38 that obviously won't be possible

TBH, I hadn't really thought of the physical size of the TDV8. Not really had anything to do with them. But that might just be the decider.

I did stumble across this post, which looked like it had promise. But the story was never concluded by the looks.

 

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2 hours ago, bishbosh said:

I think unless you get given a known good engine and have access to spectacularly competent auto electrician who will give lots of time for free then I can't see the maths  (even man maths) working for a conversion on fuel economy grounds.  😕  Even then, you might need a power bulge in the bonnet to fit it in over the axle as has been said.

The other thing to consider is what will you put behind it? The 8 speed ZF box is fantastic but not sure the P38 will have space for it?

Having written all that, have you driven an L322? Very different beast to the L405. Replacing the P38 with an L322 might be your best bet ?

Ta, the manmaths is more about spending some money on what I have, rather than spending it on another vehicle. The fuel savings would be from a different pot of money if you know what I mean.

e.g. buying another car will cost 'x' amount. But if I spend part of 'x' on the p38 instead. Could I get a better vehicle for my needs overall?

L322, I have nothing against them. Although 3 mates have them with TDV8's in, so I'd not really want the same. I also think they are too far towards a car in how they do things having driven a few over the years. Great vehicles, but again, I honestly prefer the p38 on multiple levels.

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41 minutes ago, L19MUD said:

Whilst I think a TDV8 in the P38 would be a fun project I think this probably hits the nail on the head. I have had the older 3.6 for 7 years and my old man the 4.4 for the same amount of time. The 4.4 is certainly the better one to have as there is more power but also better economy due to the extra two ratios in the box. Big diesels suit the L322 really well and I prefer our diesels to the old petrol L322 I had. 

I do like petrols, although there is no denying a turbo fed diesel with lots of low and mid range grunt does rather suit a Range Rover. Getting more power from the RV8 certainly isn't an issue. Not particularly cheap, but could be done either with some na mods or maybe a supercharger kit. But none of these will help the running costs. Yesterday the read out was a massive 12.5mpg, despite having done some gentle road miles. Pence per mile, there is a huge difference between mid 20's mpg and sub 15.

I don't know anything about this vehicle, other than it has had an M57 swap.

 

 

I'm wondering if this might be a better bet. I know it isn't a V8. But I'd guess the M57 should be able to bolt up to the ZF HP24 without too many issues?

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I'm doing a lot of zooming around on short and hilly journeys at the moment (quite often towing) and the 4.4TDV8 seems to be averaging about 23mpg. Bear in mind though that my drive is steeper than the vast majority of the hills in Surrey and Hampshire. 50% of my journeys exit the east bound which involves a hairpin on a hill that the only vehicles I haven't seen spin a wheel (if keeping on their side) are Land Rovers. The other 50% head west and there's a similarly steep hill out of the local village but no hair pin. I've driven Box Hill in Surrey and both main routes from my house are steeper. All I'm saying is the hills here are proper ones so may not be representative of most people's local routes.

I towed a tri-axle 20' trailer down to @reb78 last year I think it was and that averaged 35mpg for the journey which considering the hills on the M4 and in Devon was pretty good. That was being a good boy.

I've got close to 40 mpg out of both the 3.6 I had and now the 4.4 but boy was it boring. More importantly perhaps is I've really struggled to get it below 20mpg, I mean since the last fill up I've been driving like a hooligan, didn't quite adjust the handbrake properly when I changed the discs so had a slightly rubbing brake shoe and been loaded up quite heavily and its still doing 24mpg. 

I'd have said that you'd probably not see a massive difference in using the 8hp over the 6hp gearbox, the top two gears are really tall and normally only kick in from what I've seen above 60mph. Real world difference in having the two gears extra probably doesn't matter but for economy / emissions tests it made the difference.

So in summary it may not be doing any better at the top end but even on a **** day its still better than than the typical upper limit of what people normally get out of a sensible run in a petrol 4.6. Towing there's not much of a competitor, there is oodles of torque pretty much straight away.

I recall hearing from one of the engineers at JLR that ZF officially only rate the 8hp for 700Nm at the input, in reality the 4.4 outputs a little bit more (something like 25Nm more) and the engineers spoke to the ZF engineers and they said it'd be okay as there's a fair bit of margin. The net result was the 4.4TDV8 conveniently outputs exactly the maximum torque supported by the gearbox...

Another aside is I've worked with someone who was looking into replacing an engine on a production hydrofoiling boat. I've had a blank as to the original engine but it was already marinised by the manufacturer (may even have been a supercharged petrol) but end of life. He led a team that looked into various engines both marine and non and they bought a couple of crate engines from Ford of the 4.4TDV8 and ran trials after narrowing it down as a possibility. It was the most suitable engine that offered the power to weight they were after. The petrol ones didn't really offer the low down grunt and were more difficult to marinise as well as ending up a physically bigger package overall.

Unfortunately everything fell through as Ford turned around at the last minute and went back on their deal as they said they couldn't supply engines quickly enough for the Range Rover let alone supplying someone else.

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20 hours ago, Chicken Drumstick said:

for the same journey that the TDV8 got 32mpg, I think the p38 might be more like 17'ish. I know the RV8 can in some scenarios be ok on fuel, but an automatic, lifted suspension and MT tyres certainly knock it back.

If the TDV8 was lifted with MT's would it have gotten 32mpg???

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Well the first time I've done a "normal" drive in the Range Rover in a while yesterday. Ran down to Devon to collect 4 doors for the Defender.

Sitting at let's say comfortable RR cruising speeds with a mixture of decent runs on the cruise control, heavy traffic, fast and slow country lanes it averaged 28mpg according to the on board computer which is pretty accurate I've found. That was from filling up in Crediton to home on the Pembrokeshire border with slightly oversized ATs on the RR.

The same journey but sat more consistently at 60mph (had today tyres then) but towing a 20ft trailer with some pallet racking for @reb78 it did 35mpg. So cruising speed and smoothness of driving play a big part.

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Left field suggestion but what about something like a 1UZ or 3UZ?

I've got one sat waiting for the roundtuits to finish the 6x6 and then install it into the 110. From my previous research on it you're looking at (in factory/standard form) tuned 4.6 power figures. Start fiddling with it and the sky is pretty much your limit, throwing turbos or superchargers on there will easily get you crossing TDV8 or even 4.2 supercharged territory.

Fuel economy in conversions doesn't seem to be any worse than the 4.6 but again potential for improvement (there's plenty of people who are claiming it is more economical but I'm having a hard time finding evidence to back it up). 

@Bowie69 can probably advise more since loves these engines.

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3 hours ago, Ed Poore said:

Well the first time I've done a "normal" drive in the Range Rover in a while yesterday. Ran down to Devon to collect 4 doors for the Defender.

Sitting at let's say comfortable RR cruising speeds with a mixture of decent runs on the cruise control, heavy traffic, fast and slow country lanes it averaged 28mpg according to the on board computer which is pretty accurate I've found. That was from filling up in Crediton to home on the Pembrokeshire border with slightly oversized ATs on the RR.

The same journey but sat more consistently at 60mph (had today tyres then) but towing a 20ft trailer with some pallet racking for @reb78 it did 35mpg. So cruising speed and smoothness of driving play a big part.

I guess what is even more impressive, is you are getting those mpg figures with 335bhp too!

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27 minutes ago, Chicken Drumstick said:

I guess what is even more impressive, is you are getting those mpg figures with 335bhp too!

The TDV8 is impressive, it is a shame they have dropped it in the L460 but you could get it right up to the end of the L405 (in SDV8 form) . I have never managed much over 30 with my 3.6 as at 70mph it is sitting at around 2,000 rpm. Easily get over 30 in the 4.4 as at 70 it is sitting at only 1400rpm. Those extra higher ratios really make a difference

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1 hour ago, Chicken Drumstick said:

I guess what is even more impressive, is you are getting those mpg figures with 335bhp too!

A friend of mine work(s/ed) at JLR and supposedly they've messed around with the tunes and got it close to 1000hp and 1000ftlb, standard components and cooling could cope in the UK. Just nothing downstream of it.

If I recall going down to Rich's it was actually averaging closer to 38mpg and it was the last stretch to his place up and down all over the place that knocked it back to 35.

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Maybe the oversized tyres help and perhaps the long journeys rather than shorter ones? Haven't checked for a while mind.

Think the tyres are 255/55R20s rather than 255/50R20s. Can't be bothered to check but I can if you want.

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On 7/25/2022 at 5:21 PM, Chicken Drumstick said:

I'm wondering if this might be a better bet. I know it isn't a V8. But I'd guess the M57 should be able to bolt up to the ZF HP24 without too many issues?

I'd say that is a bolt on solution, probably with a crashed beamer as the donor, you only need to get the ECU to work standalone. The best power according to wikipedia you can get from the 2006 version is 282hp with 580 nm.

Compared to the 4.6 giving you 226Hp, looks a good proposition for a project.

Tell us on here!

Daan

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Are the MPG figures you speak of (Ed, Bish, L19MUD) coming from the dash or physical fill it up and divide the mileage on that tank. As I always get below what the dash says at around 27-28mpg.

Steve

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@steve200TDi from the dash but the last time I checked it was pretty close (certainly within 1 MPG), I haven't checked for a while though.

Remember I'm running slightly oversized tyres these days because they were the only half decent AT pattern available for a 20" rim. Plus I absolutely hate Pirelli's with a passion, only tyre I've had that's split / bulged badly.

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@steve200TDi My quoted figure is a mental calc of distance divided by litres x 4.5 to get mpg (ish). My consumption is pretty much always between 5 and 6 miles per litre. I have never concerned myself with exact fuel economy, I just want to be reassured that it is relatively consistent as a sudden change would indicate something potentially wrong. I have never trusted the MPG figures from any car's dash as in my experience they are always high.

I suppose I could just use the dash figure now I've read what I've written! Would serve the same purpose! :D 

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