Defender Air Intake, Power & Fuel Efficiency

[Sunray-I40]

I have a 1995 Defender 110 300 TDI and often tow an ex-Army Sankey MkIII trailer converted for camping.                                                              

Until late last year, I was averaging 26-27.5 MPG (see note 1)

My old steel military raised air intake (RAI – see note 2,  Bearmach or Mantec brand I think) with 2.5 inch internal diameter tube was rusty and needed replacing; and I replaced it with a Mantec polyurethane 3 inch tube RAI (with Donaldson Air Ram head).  This immediately increased my MPG to 27-28.5 MPG; I also noticed a small increase in power.  This set me thinking, and I explored the airflow inside the engine bay.

On the inside, the Land Rover air duct box and hose appears to reduce the cross-sectional area through which air flows, yet the air cleaner box has a 3 inch inlet (this applies to both the standard Land Rover air cleaner, and the military Wolf / Donaldson air cleaner box which I use —without the second filter safety element on UK roads).                                         

So I explored the question ‘what would happen if there was a 3 inch minimum cross-sectional area for air to flow from RAI head to air cleaner box intake?’

Before I could answer this question, I had to address the cause of an MOT failure (excessive emissions).  The expensive solution to this was a new turbo (the wastegate had seized on the old one), new fuel injectors (the old ones were 20-25 % out), fuel injector pump reconditioning and new glow plugs.  While I was at it, I also got my local garage to do an engine carbon clean! 

Doing all this took my fuel consumption to 28.5 - 30.5 MPG, produced a very noticeable increase in power —especially when towing uphill— and negligible emissions.

I could now answer the airflow question! 

I noticed that the air duct box for the 200TDI has a circular cross-section, as opposed to the rectangle of the 300TDI, and while the box is basically the same shape, it is a mirror image because the 200 TDI air duct is on the left hand side, whereas on the 300 TDI it is on the right hand side.

 
 

So I started looking for something similar to the 200 box which would fit a 300.  My research led me to the Nugget Stuff sealed air intake box which was designed for the Puma TDCI with a 90 mm outlet.  I had a chat over the telephone with Wayne Nielsen at Nugget Stuff, and he sent me a Puma sealed air intake box to try, with some 90mm hose, a stepdown ring and a length of 76mm/ 3 inch hose (superb quality hose!). 

Last week, the system was installed into my Land Rover.  I immediately noticed an increase in power and a lower tone in the engine sound; I could accelerate like a boy racer! 

The day it was fitted, I called Wayne and said that I expected my fuel consumption to increase because my right foot was enjoying the ability to accelerate so much more quickly!  After a day or two, I checked my fuel consumption (my local garage pump really does dispense exactly what it says; I have checked!), and sure enough I was doing 26.5 MPG (short school runs and local errands). 

 After a week, having now disciplined myself to be more ‘sensible' in how I drive —but I am still driving faster than I did —I am now doing 29.8 MPG.  That’s very close to my best ever 30.5 MPG which was achieved with less speed and engine power. 

Conclusion —the combination of a 3 inch RAI and minimum 3 inch air flow through to the air cleaner box on my Land Rover  has increased power and engine efficiency very noticeably, and given me a sealed system.   

 

Notes

1  On purchase in 2012 it was 18 MPG; the increase to 26 was achieved by fitting: full width intercooler (also increased power by 25%), full silicone hosing, EGR blanking plate, RAI and frequent tyre pressure checking.

2  In my view, an RAI only keeps the air intake out of the dust; and an RAI only becomes a snorkel when the air intake system is sealed for wading.

 

 

 

 

Edited May 30, 2018 by Sunray-I40
cut and paste went wrong

[Eightpot]

I'd say the improvements only came through getting a working wastegate, injectors and a decoke and probably improved timing from fitting a recon injection pump- if it was only doing 18mpg beforehand that's pretty dire for a tdi.  You're probably up there with performance as it should be now for a well set up engine.

 I wouldn't expect a slight improvement in inlet airflow to make a difference on a turbocharged diesel though, the turbo is whacking the air in at 15psi rather than being drawn through the system by cylinder vacuum.   Would be interesting to see some dyno printouts of different setups though. 

[landroversforever]

I'd have to agree with Eightpot mostly I'm afraid. Whilst the larger diameter RAI is going to help..... most of your gains will be from getting the engine back to running closer to factory spec with the pump etc.

I've also not worked out what the carbonclean/terraclean thing actually does, I suspect nothing and that its just snake oil. But that's just a feeling as I've not looked into it properly.

 

[neil110]

Ran a pair of 300 Tdi Defender 110 for 12-13 years. One was a very early 300 hard top, registered march 94 owned it from new, put over 300,000 miles on it, the other was a V8 Csw which had a used 300 transplanted into it.

The hardtop would do 36mpg all day long on motorways and at steady speed, on one occasion driving down through France with a stiff tail wind it managed 42MPG. Hacking in and out of central London dropped that to 30mpg. The CSW would do broadly the same hacking in and out of London, but never quite matched the hard top on longer motorway runs, typically managing about 33mpg.

 

Both had RAI, bigger intercoolers and had the pump tweaked for additional power, were serviced every 5,000 miles, used Millers synthetic oil, whatever diesel was cheapest and genuine parts for every other requirement. Tyres were 7.50 x 16 Michelin XZY on the hard top and 235/85 x 16 Goodyear MTR  on the CSW

 

 

Edited May 30, 2018 by neil110

[Sunray-I40]

On 5/30/2018 at 1:12 PM, Eightpot said:

I'd say the improvements only came through getting a working wastegate, injectors and a decoke and probably improved timing from fitting a recon injection pump- if it was only doing 18mpg beforehand that's pretty dire for a tdi.  You're probably up there with performance as it should be now for a well set up engine.

 I wouldn't expect a slight improvement in inlet airflow to make a difference on a turbocharged diesel though, the turbo is whacking the air in at 15psi rather than being drawn through the system by cylinder vacuum.   Would be interesting to see some dyno printouts of different setups though. 

Most of the improvements have indeed come from the things you refer to, almost back to 'as it left the factory', but the last 15% or so has come from the combination of increasing the RAI tube size and the air flow from inside the wing to air cleaner box, both of which were done after getting the engine to where it should be.  Defender2.net has an interesting thread on air flow http://www.defender2.net/forum/topic49178.html?highlight=air+intake

[Sunray-I40]

On 30/05/2018 at 4:21 PM, neil110 said:

 

The hardtop would do 36mpg all day long on motorways and at steady speed...

Both had RAI, bigger intercoolers and had the pump tweaked for additional power, were serviced every 5,000 miles, used Millers synthetic oil, whatever diesel was cheapest and genuine parts for every other requirement. Tyres were 7.50 x 16 Michelin XZY on the hard top and 235/85 x 16 Goodyear MTR  on the CSW

 

 

I'd love to know how to get to 36 mpg!  i have plenty of power and now I'm used to driving the 'new' engine am getting a shade of 30.9 mpg consistently.

[Lightning]

I’ve never managed anywhere near 36 mpg in a TDi

Although l managed 32mpg out of my TD5 while touring through Spain.

[neil110]

Possibly the way in which I drive. I didn't set out to specifically achieve high MPG and would typically drive at somewhere around 65-70MPH on the motorway. I rarely accelerate hard, by careful observation and allowing a reasonable distance between self and vehicle ahead, rarely need to use brakes. Make good use of the gears rather than holding onto a higher gear when speeds drop and acceleration is required. 

It all stems from reading an article in a bike magazine, many years ago. Not sure if it still the case but powerful motorcycles used to get through tyres at an alarming rate and the article described how to prolong the life of tyres, whilst still enjoying the full performance of the bike. I have tried to apply the same principles ever since

[BogMonster]

You chaps must have a light right foot, on successive 300Tdi vehicles I have owned (some new), I have struggled to get much more than 20mpg!

[Mo Murphy]

I got 30mpg once in my old 300, following a 2 1/4 diesel to Wales on A roads !

Otherwise 20 to 25 mpg at best.

My current 200 does about 23mpg whatever I do. 

Lord know what the 3.9 will do when I put it in 😊

Mo

[dailysleaze]

I got 36mpg in Morocco driving 60mph. Best in the UK has been 33, averaging 31-32 (it's a 110, 180k miles).

When I first got it it was doing 26mpg. The biggest change happened when I fitted a turbo gauge. I too drive like neil110. I only use the brakes to slow down as a last resort. It's like a game 

[Snagger]

1 hour ago, BogMonster said:

You chaps must have a light right foot, on successive 300Tdi vehicles I have owned (some new), I have struggled to get much more than 20mpg!

On those roads, that's probably good!  I'd imagine you don't spend a great proportion in 5th with steady cruising, much more accelerating in low gears like town driving.

My Tdi in the 109 is undergeared using SIII transmission, and it has a lot of drag from the Brownchurch rack, spots, bull bar and so on, but it still returns 27mpg.  Sunray's 18mpg points to significant problems, and Mo's sounds like something is amiss.  My high mileage RRC Tdi returned a reliable 35mpg in mixed driving.

[FridgeFreezer]

20mpg? May as well bolt a V8 in and save money on fuel!

[reb78]

Glad to hear some other real life tdi economies on here - i was beginning to think there was something wrong with mine. I get the same as Mo, 20-25 mpg normally, as low as 19 mpg if i am towing a heavy load. 

Running on sunflower oil at the moment at 70ppl, so it almost halves the cost compared to diesel (mpg is not affected).

Edited June 12, 2018 by reb78

[dailysleaze]

7 hours ago, dailysleaze said:

I got 36mpg in Morocco driving 60mph. Best in the UK has been 33, averaging 31-32 (it's a 110, 180k miles).

When I first got it it was doing 26mpg. The biggest change happened when I fitted a turbo gauge. I too drive like neil110. I only use the brakes to slow down as a last resort. It's like a game 

I will caveat this by saying it's on a 1.2 T-box, commute is 50 miles B-roads/lanes & 30 miles motorway, EGR & cat removed, 235/85 BFG AT tyres, serviced every 6-9 months, mostly empty vehicle. I only measure it by filling one click on the pump (mostly the same garage) and using the speedo mileometer, which is whatever% out from true. https://fuel.io/ is what i use to track it.

The biggest things i've seen that drop my mpg, driving the same roads, have been fuel leaks (leak off pipes, injector union, injection pump spindle seal, fuel tank breather), heavy loads or constantly driving into a head wind. 

Mpg only matters to people who like efficiency (like me). If you like the being pushed into the back of your seat and hearing the roar of the engine then economy is not your thing and mpg values don't matter.

[Retroanaconda]

I have good real-world data (adjusted for speedo error) for the last four years or so of driving:

Average for normal driving (127,108 miles) is 30.8mpg.

Average for towing (5,741 miles) is 26.3mpg.

If it’s doing over 30 I’m happy - conditions such as head winds as mentioned above make a huge difference. 

[oneandtwo]

My 300tdi 90 is definatly down on performance since fitting the hideously expensive genuine Land Rover Puma raised air intake.

[landroversforever]

Snorkels are a huge restriction on the air intake. 

[Simon Smith]

200tdi 110 county. Big intercooler, tweaked pump janspeed exhaust and a steel tube snorkel. I drive fairly quickly and get around 28mpg running around to work etc and 30 on a decent run. 

[monkie]

Just for comparison as this will always be lower than a Tdi. My 2.5TD (19J) in my 110 gives me 22-23 mpg on a long run dropping to 18-19mpg on town driving carrying stuff about. I have the standard air intake system, no snorkel. I do have to work it hard up hills which is one of the reasons why I think it is low.