LetsHopeItFits

Active Member
So having owned a 3.9 V8 Discovery 1 for a while, and having fed it petrol every 300 miles (if Im lucky) and having had its electronics completely break, I went and had a look for a 300tdi instead.
I found one not too far from me, and went to have a test drive. I knew it wouldnt be as quick as mine, but I was shocked. There was a brief moment in the rev range where its not too bad, but either side of that its awful.
So Ive done some googling, and it turns out that they can be fiddled with (increasing the boost pressure, tweaking the fuelling, etc) and they make slightly more power, but having raced my V8 disco against my mates 90 (which had 300tdi disco running gear and those afformentioned mods) its still nowhere close, despite my disco being what, 400kg heavier?
So I looked further, VNTs and larger intercoolers, and the twin port inlet manifold to stop it blowing a headgasket seem to be the next logical steps - but can someone quantify what these changes would do? A rough power figure? Because the 117hp standard 300tdi that I drove felt more like a JCB, compared to the relatively car-like performance of my 180hp V8. My mate reckon his 90 was making 130-140hp, but I very much doubt that, because that leaves him at 80-87hp/ton, and my disco was at 85-90hp/ton (cant remember how much fuel was in the tank) but the gap in performance was vast. I wouldnt be supprised if my V8 would have towed his defender quicker than it moved.
I get that the 300tdi is a completely different engine to the V8, designed to last forever, at the lowest cost, unlike the V8 which is basically a 1960s muscle/sports car engine.
I dont want to just crap on the 300tdi, I want to know if it can be made good. Well its already good, can it be made to go quickly? The V8 does 0-60 in a smidge over 10 seconds, and from personal experience, I can report that it will hold the speed limit up a very steep hill with a very heavy trailer (albeit in 3rd gear). These are the metrics by which Id like a modified TDI to compare, even if it cant beat them, if it can get close, but do it whilst using half the fuel, thats a win.
 
Okay, answering my own question, but Id still appreciate peoples best guesses as to an actual BHP figure.
So heres what to do - Get a standard 300tdi, and make sure its in good condition, fresh coolant, of the correct type, mixed in the correct ratio, no blocked radiators, not obstructed by any spotlamps or anything. Also with no fuel pump tweaks, no boost fiddling, no snorkel, completely unaltered.
Then fit an EGT gauge, hitch up a nice big heavy trailer, find the longest, steepest hill you can, on the hottest day of the year, and drive up and down it repeatedly, trying to get those EGTs as high as you can without making any mechanical or aerodynamic changes. Voila, now you have the maximum EGT figure. Also get a figure when just driving around normally, no trailer etc, to see what it does normally.
Then when you go bolting on a VNT, intercooler, snorkel, winch bumper, spotlamps, and adjust the fuelling, you now know what the EGTs must not exceed. If you find them getting too hot, change something, get rid of the spotlamps, whatever. And I think Im right (please correct if not) that generally, colder=better for EGTs when just driving around, so long as theres no smoke (which indicates its running too rich).
Thanks
 
While egt's are a very important measure - it's not the only one

I can get 650 while doing 2000 rpm in thick sand very quickly - but if i am doing 120 kph I don't want to see over 550 on even the steepest hill
4 th gear and 3000 rpm will get you to 700 very quickly without the right foot pressed to the floor

I agree about getting a base line for your vehicle - but a vgt and big intercooler will change the characteristics a lot so the baseline might become useless

If you are adding more air and cooler to boot that will result in your motor running at it's best and not produce much more power at all

Then you can start messing with the various screws on the injector pump - which gives more fuel to match the extra air available

I dought you will get figures the same as a td5 in std form though - you can but the motor isn't going to last long

I have had an egt guage for about 15 years now and it is worth every penny
my smoke screw is turned up by about 10 minutes and I have the same adjustment on the top of the injector pump boost chamber

I have a slightly modified turbo compressor wheel and the next level intercooler from a well known british company who's name escapes me now
 
Last edited:
If you want the v8 power, unless you are doing high yearly mileage I would stick to the v8 as the cost of all the upgrades to the 300 would buy an awful lot of petrol without the disappointment
 
I personally think the v8s are pants, fuel gulping disappointment, sound good though! but no matter what you do you wont get a 300tdi anywheres near what a v8 will be capable of.
 
If you want the v8 power, unless you are doing high yearly mileage I would stick to the v8 as the cost of all the upgrades to the 300 would buy an awful lot of petrol without the disappointment
This was my thought exactly when I bought the V8, especially when at the time it was almost £600 cheaper to insure the V8 than in was the diesel, and there was an LPG station near me, and at the tipe petrol was 104.9p/L because covid.
But within a year, I was paying over £1.90/L, and it was costing me 70p/mile in fuel alone.
At todays prices, Id buy the diesel. Especially since Ive got the space to make my own diesel from veg oil (would twin tank for reliability) and since Im older, insurance isnt as horrific as it was a few years ago.
The thing is, the V8 is nice, fast, and refined enough to use everyday. The standard 300tdi isnt. At todays prices (circa 145p/L, or £6.60/gallon) the V8 costs about 45p/mile in fuel. So even with moderately low use, 5000 miles a year, thats still £2250 just in petrol. Obviously the diesel isnt free, but Id reasonably expect it to cost half as much, just running on diesel from the pump. Thats over £1000 a year to be saved, if the diesel can be made nice enough to drive everyday, rather than only when the Landy is needed.
I personally think the v8s are pants, fuel gulping disappointment, sound good though! but no matter what you do you wont get a 300tdi anywheres near what a v8 will be capable of.
They do drink fuel. Personally, thats where the downsides stop. The 3.9 V8 is a fast old bus, itll sit at over 100mph, itll do 0-60 in just over 10 seconds, as a utilitarian vehicle, even modern machines struggle to match it. Its quicker than the 3.2L Ford Ranger, and I reckon with some relatively minor modifications, itd outrun a V6 Amarok. Obviously itll probably drink more than both combined...

So what Im gathering then really is "no" - the 300tdi will never keep up with the standard 3.9 V8.
Does anyone know how much boost a stnadard 300tdi engine can take? Because thinking about it, its basically a strengthened, turbocharged verson of the 2.5NA military engine, which makes 67hp without any boost, and Im told the standard engine has slightly less than a bar and makes 117hp, which suggests that with a bar of boost it should make 134hp, less the increased pumping losses and the inefficiency of other components, call it 125-130. So if it can take 2 bar, or 29psi, it should make almost 200hp, but Im guessing it cant take 2 bar...
 
This was my thought exactly when I bought the V8, especially when at the time it was almost £600 cheaper to insure the V8 than in was the diesel, and there was an LPG station near me, and at the tipe petrol was 104.9p/L because covid.
But within a year, I was paying over £1.90/L, and it was costing me 70p/mile in fuel alone.
At todays prices, Id buy the diesel. Especially since Ive got the space to make my own diesel from veg oil (would twin tank for reliability) and since Im older, insurance isnt as horrific as it was a few years ago.
The thing is, the V8 is nice, fast, and refined enough to use everyday. The standard 300tdi isnt. At todays prices (circa 145p/L, or £6.60/gallon) the V8 costs about 45p/mile in fuel. So even with moderately low use, 5000 miles a year, thats still £2250 just in petrol. Obviously the diesel isnt free, but Id reasonably expect it to cost half as much, just running on diesel from the pump. Thats over £1000 a year to be saved, if the diesel can be made nice enough to drive everyday, rather than only when the Landy is needed.

They do drink fuel. Personally, thats where the downsides stop. The 3.9 V8 is a fast old bus, itll sit at over 100mph, itll do 0-60 in just over 10 seconds, as a utilitarian vehicle, even modern machines struggle to match it. Its quicker than the 3.2L Ford Ranger, and I reckon with some relatively minor modifications, itd outrun a V6 Amarok. Obviously itll probably drink more than both combined...

So what Im gathering then really is "no" - the 300tdi will never keep up with the standard 3.9 V8.
Does anyone know how much boost a stnadard 300tdi engine can take? Because thinking about it, its basically a strengthened, turbocharged verson of the 2.5NA military engine, which makes 67hp without any boost, and Im told the standard engine has slightly less than a bar and makes 117hp, which suggests that with a bar of boost it should make 134hp, less the increased pumping losses and the inefficiency of other components, call it 125-130. So if it can take 2 bar, or 29psi, it should make almost 200hp, but Im guessing it cant take 2 bar...
If I remember correctly standard TDI turbo can make between 1.25 and 1.45 bar maximum
 
If I remember correctly standard TDI turbo can make between 1.25 and 1.45 bar maximum
Yeah, Im quite happy to change the turbo, Id just like to know how much boost/power I can expect the engine to cope with. If Im going to hate driving it because its got no power, no matter what mods I do, then Ill stick with the V8, and see if theres anything I can do to make it use less fuel.
 
Fuel cost doesn't matter much if you don't do many miles.
I could get my Mustang down to 5 mpg if I tried hard enough.
Think you are expecting too much from a TDI, except it for what it is or move on.

.
 
So having owned a 3.9 V8 Discovery 1 for a while, and having fed it petrol every 300 miles (if Im lucky) and having had its electronics completely break, I went and had a look for a 300tdi instead.
I found one not too far from me, and went to have a test drive. I knew it wouldnt be as quick as mine, but I was shocked. There was a brief moment in the rev range where its not too bad, but either side of that its awful.
So Ive done some googling, and it turns out that they can be fiddled with (increasing the boost pressure, tweaking the fuelling, etc) and they make slightly more power, but having raced my V8 disco against my mates 90 (which had 300tdi disco running gear and those afformentioned mods) its still nowhere close, despite my disco being what, 400kg heavier?
So I looked further, VNTs and larger intercoolers, and the twin port inlet manifold to stop it blowing a headgasket seem to be the next logical steps - but can someone quantify what these changes would do? A rough power figure? Because the 117hp standard 300tdi that I drove felt more like a JCB, compared to the relatively car-like performance of my 180hp V8. My mate reckon his 90 was making 130-140hp, but I very much doubt that, because that leaves him at 80-87hp/ton, and my disco was at 85-90hp/ton (cant remember how much fuel was in the tank) but the gap in performance was vast. I wouldnt be supprised if my V8 would have towed his defender quicker than it moved.
I get that the 300tdi is a completely different engine to the V8, designed to last forever, at the lowest cost, unlike the V8 which is basically a 1960s muscle/sports car engine.
I dont want to just crap on the 300tdi, I want to know if it can be made good. Well its already good, can it be made to go quickly? The V8 does 0-60 in a smidge over 10 seconds, and from personal experience, I can report that it will hold the speed limit up a very steep hill with a very heavy trailer (albeit in 3rd gear). These are the metrics by which Id like a modified TDI to compare, even if it cant beat them, if it can get close, but do it whilst using half the fuel, thats a win.
So there is a lot to answer here.

I like V8's (currently own 4 of em, not just Rover's, but all OHV's). The Rover V8 isn't a bad engine for 200-250hp targets, although from the factory they make a lot less. Most V8's are autos which hamper performance and mpg being slightly over geared, although the torque converter and no need to lift of the throttle kickdowns can make them more capable in some situations.

Most older RV8s are also a bit worn with a worn cam and/or followers, which can knock the HP back a lot to well below factory stock levels. However, anything 3.9 EFI or newer has potential to make 180-200hp in good running order with little needing to be done to it.

A TDI is only 111bhp standard (slightly more for the EDC version in the Disco 1 autos). As you say, you can make lot of tweaks for some easy gains, although much of the gain is what I'd call "below the curve". Peak power doesn't increase massively, but the torque and HP below Peak rpm does, which makes it feel like you picked up a lot more than you really did. This makes them much more driveable and capable as tow vehicles, so long as you don't let the EGTs get too high.

My Uncle has a 300Tdi in an F plate pickup, it was converted many many years ago, long before people started doing this sort of thing. And had it tuned by Jermey J Fearn along with a big intercooler, it feels quite peppy to drive and towing has bested a number of V8's when having a bit of a side by side run up a long motorway drag. Although part of this is likely gearing when the V8's have been autos.

As for actual output claims, lots of places used to claim circa 135hp for a tweaked Tdi and big intercooler. Although after a while you'd also see claims of 150+hp Personally I think 150hp claims are a little unrealistic.

At our club we have done a couple of Dyno Days. I can't vouch for the accuracy of the numbers as dyno's don't direclty compare to factory figures, but all of the Tdi's where sub 140hp. And interestingly like for like mods all of the Td5's made about 20hp.

I like the Tdi engine, abeit they are somewhat unrefined, but they are frugal, pretty sturdy and I like the power delivery they offer up. Mine is mildly modded, although I think the under the curve power gains let them perform better than the numbers suggest. My Tdi is over geared with a 1.2 transfer box, 33" tyres and tall gearbox gearing. But it is in a hybrid 88" coiler. Likely a little lighter than a 90. A mate has a Td5 90 on 235 tyres with big intercooler, turbo and lots of other bits. Alive tuning tuned it and it made about 190hp and similar on the dyno day with the club. On paper it makes lot more power than my 200Tdi. Although on the road he doesn't have enough power to overtake from a 20-80mph roll. And from a standing start I beat him 3 times with no losses. Albeit the standing start is possible more driver related than vehicle. But the Tdi had enough power to secure the wins.

Last year I also did a drag race (in field at an event) against a 2.7 auto Disco 3 an 86" coiler 3.9 EFI 5 speeder and an 88" coiler comp safari motor with a 3.9 carb engine and 4 speed manual. 1st race was close between the V8's and the Tdi with a photo finish, all of us lead at one point (I got a rubbish start, way too much wheel spin). 2nd race I got a much better start and won by a car length. Sadly no footage of it.

Back to power outputs. I feel you'd very well to get a 'real' 150hp+ from a road going Tdi, although with headwork and all the bolt ons it might be possible to see more. I've seen outlandish claims from people in the USA saying 200-250hp, but I think they are completely BS. It is possible to take the Tdi out to 2.8 litres which will help, but they just weren't designed for maximum output and don't really rev all that well, even for a diesel. I would say over the years there I have seen a huge variance in Tdi performance. Many stock ones go well while others are complete dogs. Even when new/newish. If you have an under performing one, even with all the usual mods, it'll still under perform. A friend (who now has the Td5) had one of these. And even fully modded I could with my 200Tdi pull bus lengths to football fields on him on a simple roll race.

I've never tried, but if Peak power is your goal, I suspect Nitrous Oxide might be quite interesting. I'd hope you could run a 25-50 shot on a tweaked Tdi and reckon it could make it quite a weapon (relatively speaking). But Nos is only good for wide open throttle and offers no part throttle gains.

Also things have moved on. If you have a 300Tdi (R380) gearbox, then a Td5 swap is not all that hard and relatively affordable. And as said earlier, like for like the Td5's all made an easy 20hp more than the Tdi's and you can mod the Td5 further.

The other option is the BMW M57 swap, bit more pricey than the Td5 although in many ways a simpler swap into a 300Tdi. A few mods and a remap and you have 230-250hp and potential for even more if you really want to spend some money on the engine.
 
If I remember correctly standard TDI turbo can make between 1.25 and 1.45 bar maximum
Do remember that boost is a measure of resistance and not flow. Therefore a higher boost figure does not always mean you are getting more air into the engine. It may also be hotter air too.
 
So there is a lot to answer here.

I like V8's (currently own 4 of em, not just Rover's, but all OHV's). The Rover V8 isn't a bad engine for 200-250hp targets, although from the factory they make a lot less. Most V8's are autos which hamper performance and mpg being slightly over geared, although the torque converter and no need to lift of the throttle kickdowns can make them more capable in some situations.

Most older RV8s are also a bit worn with a worn cam and/or followers, which can knock the HP back a lot to well below factory stock levels. However, anything 3.9 EFI or newer has potential to make 180-200hp in good running order with little needing to be done to it.

A TDI is only 111bhp standard (slightly more for the EDC version in the Disco 1 autos). As you say, you can make lot of tweaks for some easy gains, although much of the gain is what I'd call "below the curve". Peak power doesn't increase massively, but the torque and HP below Peak rpm does, which makes it feel like you picked up a lot more than you really did. This makes them much more driveable and capable as tow vehicles, so long as you don't let the EGTs get too high.

My Uncle has a 300Tdi in an F plate pickup, it was converted many many years ago, long before people started doing this sort of thing. And had it tuned by Jermey J Fearn along with a big intercooler, it feels quite peppy to drive and towing has bested a number of V8's when having a bit of a side by side run up a long motorway drag. Although part of this is likely gearing when the V8's have been autos.

As for actual output claims, lots of places used to claim circa 135hp for a tweaked Tdi and big intercooler. Although after a while you'd also see claims of 150+hp Personally I think 150hp claims are a little unrealistic.

At our club we have done a couple of Dyno Days. I can't vouch for the accuracy of the numbers as dyno's don't direclty compare to factory figures, but all of the Tdi's where sub 140hp. And interestingly like for like mods all of the Td5's made about 20hp.

I like the Tdi engine, abeit they are somewhat unrefined, but they are frugal, pretty sturdy and I like the power delivery they offer up. Mine is mildly modded, although I think the under the curve power gains let them perform better than the numbers suggest. My Tdi is over geared with a 1.2 transfer box, 33" tyres and tall gearbox gearing. But it is in a hybrid 88" coiler. Likely a little lighter than a 90. A mate has a Td5 90 on 235 tyres with big intercooler, turbo and lots of other bits. Alive tuning tuned it and it made about 190hp and similar on the dyno day with the club. On paper it makes lot more power than my 200Tdi. Although on the road he doesn't have enough power to overtake from a 20-80mph roll. And from a standing start I beat him 3 times with no losses. Albeit the standing start is possible more driver related than vehicle. But the Tdi had enough power to secure the wins.

Last year I also did a drag race (in field at an event) against a 2.7 auto Disco 3 an 86" coiler 3.9 EFI 5 speeder and an 88" coiler comp safari motor with a 3.9 carb engine and 4 speed manual. 1st race was close between the V8's and the Tdi with a photo finish, all of us lead at one point (I got a rubbish start, way too much wheel spin). 2nd race I got a much better start and won by a car length. Sadly no footage of it.

Back to power outputs. I feel you'd very well to get a 'real' 150hp+ from a road going Tdi, although with headwork and all the bolt ons it might be possible to see more. I've seen outlandish claims from people in the USA saying 200-250hp, but I think they are completely BS. It is possible to take the Tdi out to 2.8 litres which will help, but they just weren't designed for maximum output and don't really rev all that well, even for a diesel. I would say over the years there I have seen a huge variance in Tdi performance. Many stock ones go well while others are complete dogs. Even when new/newish. If you have an under performing one, even with all the usual mods, it'll still under perform. A friend (who now has the Td5) had one of these. And even fully modded I could with my 200Tdi pull bus lengths to football fields on him on a simple roll race.

I've never tried, but if Peak power is your goal, I suspect Nitrous Oxide might be quite interesting. I'd hope you could run a 25-50 shot on a tweaked Tdi and reckon it could make it quite a weapon (relatively speaking). But Nos is only good for wide open throttle and offers no part throttle gains.

Also things have moved on. If you have a 300Tdi (R380) gearbox, then a Td5 swap is not all that hard and relatively affordable. And as said earlier, like for like the Td5's all made an easy 20hp more than the Tdi's and you can mod the Td5 further.

The other option is the BMW M57 swap, bit more pricey than the Td5 although in many ways a simpler swap into a 300Tdi. A few mods and a remap and you have 230-250hp and potential for even more if you really want to spend some money on the engine.
Thanks - Id happily say that my standard V8 manual is a lot quicker than an alive tuning 190hp TD5 defender 110, I know because Ive tested it, drag racing on a beach. Both with KO2 AT tyres, although mine was on 235/70r16 and the 110 had 235/85r16, but then the transfer gearing sort of makes up for it. I locked the center diff, dumped the clutch, and it just flew. Into 2nd and before you know youre doing 50mph and youve left everything else for dead. I also beat a supposedly 400hp Audi, but that was on road tyres, so it hardly moved.

I dont mind having to change down a gear or 2 to get the power, especially when the V8 has such decent low end grunt too, its not like it stalls all the time offroad. Ill probably fit 235/85r16 tyres for more clearance, but I probably wont fit a suspension lift, Ill just trim the bodywork. Im wondering if I could drastically upgrade my V8 and get more fuel economy - now obviously bigger tyres arent normally a good idea, but the same width and slightly taller would increase the gear ratios and drop the revs. Im also thinking that possibly an increased stroke would help, because more torque lower down means less need to rev. Now obviously increasing engine displacement and tyre size sounds like a daft way to try and increase fuel efficiency, but might it just work?

Ive not driven an auto, so I cant comment, but Im guessing theyre pretty awful.

TD5s, M57s, meh, not really my cup of tea. I did think about the M51 from a P38, with the mechanical fuel pump from an E34 BMW, or an OM-series mercedes engine, but the latter is so expensive, and the former doesnt sound like a significant enough upgrade to be worth the hassle.
 
Another thing has just sprung to mind, Ive only ever driven, and heard reports from people who drive in the UK.
How does the fuel consumption of the V8 and the 300tdi compare when driving offroad? Either low-range, technical driving, when I guess its more appropriate to measure fuel use in L/hour of gallons/hour, or when driving single track rough roads at relatively low speeds? I know the diesel uses alot less when on the open road, motorways and A roads, but what about when doing land rover things?
Thanks!
 
Obviously the V8 will use more.
You might be in low range but you might need your revs up for whatever reason.
A V8 is going to use a lot of fuel unfortunately, its a fact of life.
 
Ive not driven an auto, so I cant comment, but Im guessing theyre pretty awful.
The pre edc tdi autos are so slow it is unreal, edc tdi autos are also slow as standard, and the throttle is like an on/off switch with no go in either position! but chipped up they truly fly, this was a plug in chip, then I got it remapped by that tuning guy up north and it was better again, not massively so, but it pulled harder than the plug in chip.
If you want to be truly disullusioned then blag a drive in a td5 auto, loads of revs and no go.
 
Another thing has just sprung to mind, Ive only ever driven, and heard reports from people who drive in the UK.
How does the fuel consumption of the V8 and the 300tdi compare when driving offroad? Either low-range, technical driving, when I guess its more appropriate to measure fuel use in L/hour of gallons/hour, or when driving single track rough roads at relatively low speeds? I know the diesel uses alot less when on the open road, motorways and A roads, but what about when doing land rover things?
Thanks!
The difference (percentage wise) will remain. When I used to setup an RTV event, I'd spank £50 in fuel when using a 3.5 V8 Ninety. In a Tdi the same setup would cost about £20-25.

But it depends what you are doing really. If the V8 drops to say 8mpg off road, but you only cover 2-3 miles, does it really matter in the grand scheme of things?
 
More drivel :rolleyes: I cant be ar$ed to read it you smashed a 400bhp audi in a landy did he have a heart attack at the wheel.

300tdi is too slow for you, v8 is too expensive for you, td5 isnt good enough for you wots left a puma..........
 
More drivel :rolleyes: I cant be ar$ed to read it you smashed a 400bhp audi in a landy did he have a heart attack at the wheel.
It was on sand.... And I had All Terrain tyres, and a locked center diff. He had road tyres and a Haldex AWD system. Its amazing what you learn when you decide you can be arsed to read.

The difference (percentage wise) will remain. When I used to setup an RTV event, I'd spank £50 in fuel when using a 3.5 V8 Ninety. In a Tdi the same setup would cost about £20-25.

But it depends what you are doing really. If the V8 drops to say 8mpg off road, but you only cover 2-3 miles, does it really matter in the grand scheme of things?
Yeah, Im thinking more of doing a longer trip to somewhere sandy, thats where the extra power of the V8 will really shine through, or rather, its where the 300tdi will really struggle with only 112hp.

What about the 2.8L "internatioan/tgv" engine, which as far as I know, a stroked version of the 300tdi with a different turbo. Thats got 135hp as standard, the same as the early 3.5 carby V8 discovery. Looking at its dyno graph, it makes peak power quite low down, so what would need to be done to make that same torque higher up? Or does the 300tdi's head flow like a buckled hosepipe, and so no matter what, itll never hold its low rpm torque all the way and make peak power at 4000rpm?
The other very tempting option, since discos arent that expensive, is to just own both and see which one Id pick to drive in the morning, knowing Ill have to fill them up. If the V8 is so much more thirsty, and the 300tdi isnt that bad, then Ill take the 300tdi and can forget the V8. But if the diesel is so slow and horrid that I find myself taking the petrol most days, to hell with the extra fuel, then that too would say a lot.
 

Similar threads