Td5 mpg

danam1 · Jan 1, 2015

I've just finished a fairly accurate mpg check and thought it would of been a little better tbh.
I've had a dynachip remap and EGR removal but am still only getting 22.5 mpg, this is a combination of short runs and motorway driving (55-60mph). I'm not too fussed but thought it would of been slightly better? Any ideas appreciated.

thebiglad · Jan 1, 2015

danam1 said:
I've just finished a fairly accurate mpg check and thought it would of been a little better tbh.
I've had a dynachip remap and EGR removal but am still only getting 22.5 mpg, this is a combination of short runs and motorway driving (55-60mph). I'm not too fussed but thought it would of been slightly better? Any ideas appreciated.

That sounds low but mpg depends VERY much on driving style and conditions.

Is yours manual or auto? I've had both and my manual cars all did at least 10% better mpg.

danam1 · Jan 1, 2015

thebiglad said:
That sounds low but mpg depends VERY much on driving style and conditions.

Is yours manual or auto? I've had both and my manual cars all did at least 10% better mpg.

sorry, its auto. I drive it quite light footed too

ldrego · Jan 1, 2015

Getting 29 on my manual since the remap. Was getting 22 before.

thebiglad · Jan 2, 2015

danam1 said:
I've just finished a fairly accurate mpg check and thought it would of been a little better tbh.
I've had a dynachip remap and EGR removal but am still only getting 22.5 mpg, this is a combination of short runs and motorway driving (55-60mph). I'm not too fussed but thought it would of been slightly better? Any ideas appreciated.

1. Are you sure the mpg calculation is correct? Are you brimming the tank then doing at least 300 to 400mls then brimming the tank again, so that you have an accurate measure of the fuel used, as well as the distance covered?

2. If no.1 is accurate, what percentage of distance travelled is motorway?

3. When on motorways, does the autobox go into Torque Converter lock-up mode at approx 55mph? It feels like it's going into a higher gear and the revs drop.

4. When was your air filter last changed? If in ANY doubt, change it now.

5. When was the MAP last cleaned? If you don't know, do it now.

6. When was the ECU red plug last checked/ cleaned? If in doubt, do it now.

In my opinion there is a design fault with the TD5 autobox, namely the torque converter (TC) used. With all torque converters there is a design parameter called "stall speed". This is the rotational speed at which 100% of the input power reaches the output. Now with the TD5 version of the TC, the stall speed is 2600-2800rpm. In other words below those rpms, there is constant slip and loss of power through the gearbox to the driving wheels - therefore inefficiency, therefore poor mpg.

However, on the v8 autobox the TC is larger and with a stall speed of 2200-2400rpm. This means that with this TC you are more of the time within a more efficient band of power transmission.

Wouldn't it be nice if you could put this v8 TC into a TD5? Would it be even nicer if someone did a kit for this conversion including a stronger faceplate?

Well there is!!!!! See here : http://www.ashcroft-transmissions.c...nverters/td5-heavy-duty-torque-converter.html.

I've driven a couple of TD5's with this modification and it totally transforms the vehicle. It feels more connected, less revvy, more powerful and just so much better. Not cheap but very good.

Cheers
Dave

danam1 · Jan 2, 2015

Thanks for the reply Dave,
I got 400 miles from 80.7 litres of fuel i.e. a full tank.
I would say 40% of traveling was motorway driving.
TC cuts in at about 53-55 mph.
Not sure when air filter was changed, I assume it was done on last service (4,000 miles ago?) I will change it though.
MAP not been cleaned by me so I will buy some carb cleaner and do it.
ECU plug cleaned when dynachip remapped her.
As for HD TC I imagine the labour costs would be higher than the actual TC which is £315ish.

thebiglad · Jan 2, 2015

danam1 said:
Thanks for the reply Dave,
I got 400 miles from 80.7 litres of fuel i.e. a full tank.
I would say 40% of traveling was motorway driving.
TC cuts in at about 53-55 mph.
Not sure when air filter was changed, I assume it was done on last service (4,000 miles ago?) I will change it though.
MAP not been cleaned by me so I will buy some carb cleaner and do it.
ECU plug cleaned when dynachip remapped her.
As for HD TC I imagine the labour costs would be higher than the actual TC which is £315ish.

You know a full tank is actually 95 ltrs, but I'm assuming you mean you did the calculation based on brim-to-brim?

For the MAP I normally use Brake & Clutch aerosol cleaner from Tool Station, at £2.50 per 400ml can. Leaves no residue and is sufficiently cheap that you can use it to clean just about anything 'claggy'.

Changing the TC is a job you could do yourself it's not complicated, just heavy !!!

danam1 · Jan 3, 2015

No, I put £100 worth of fuel in her which was 80.7 litres and then noted the the mileage (I waited for the yellow light to come on then filled her up then noted the mileage when the light came back on).
I thought the TC would be a gearbox or transmission off jobby

!!

thebiglad · Jan 3, 2015

danam1 said:
No, I put £100 worth of fuel in her which was 80.7 litres and then noted the the mileage (I waited for the yellow light to come on then filled her up then noted the mileage when the light came back on).
I thought the TC would be a gearbox or transmission off jobby!!

Really to get a truly accurate reading of fuel consumed, you need to fill the tank until you see the fuel level, then do lots of miles, then re-fill to the same level.

To replace the TC you are right - you need to remove the autobox as the TC is within the bellhousing.

Bennehboy · Jan 3, 2015

Some other things which can reduce fuel economy...

* Thermostat, if it's failed open the coolant will take a lot longer to come up to temperature, as a consequence the ECU throws in extra fuel to increase EGT and help warm up faster.

* Failing temp sender - these fail gradually with age, so the ECU again throws in more fuel... ONLY FIT GENUINE BOSCH senders, all the others are utter crap.

* Failing fuel temp sender - see above, if you've replaced the FPR lately this will have been renewed, but if it wasn't a genuine replacement item chances are it has a crapola temp sender in it.

* Dirty Intercooler - over time the intercooler gets coated with a film of oil which is blown out of the breather and into the turbo inlet, you should remove the intercooler and flush it with a solvent at least once a year imho. The oil film reduces the heat exchange capability of the intercooler which means the inlet air is not as cool or dense as it could be. The cooler (and therefore more dense) the air is, the more there is to mix with the fuel and ensure more complete combustion.

diver · Jan 3, 2015

I've got a manual TD5. Average consistently 28mpg. Thats 25 miles per day driving into work, usual stop/start traffic into London. 120 miles at weekend down to the coast so a mix of traffic and motorway. Thats on standard Pirelli Scorpions. I did have some Maxis All Terrains fitted (can't remember what size) and I was getting ~ 24mpg.
Surprised me. Nearly 20% difference. Worth checking your tyres.

steveyorks · Jan 4, 2015

I have a remapped TD5 manual and my driving is all around town. With any car I own a generally get the published urban figure for fuel consumption. With the disco I get about 25mpg but I dont drive it with a light foot if I am honest. All these gearbox mods etc are very well but if the OP has a concern with mpg because of cost he is never going to get the money back he would spend on all that work.

beerdude · Jan 25, 2015

I have a td5 auto with 140000 miles, I have blanked the egr. lately I have been towing a 3.5 ton trailer with much shunting around and mostly country road and stop/start driving and I'm getting a little under 18mpg.

danam1 · Mar 24, 2015

So I've been continuing to check my mpg. I've done what thebiglad suggested and been brim to brim checking so I'm very accurate. Lately I've been doing mainly short runs but I'm only getting 20.5 mpg! Just to recap:- I've removed the EGR valve, had an engine remap from dynachip, cleaned the red ECU connector and seen that the intercooler is fairly clean. Still got to change the air filter and clean the MAP sensor but will these two things really make that much difference?

Bromsgrove Defender · Mar 24, 2015

danam1 said:
So I've been continuing to check my mpg. I've done what thebiglad suggested and been brim to brim checking so I'm very accurate. Lately I've been doing mainly short runs but I'm only getting 20.5 mpg! Just to recap:- I've removed the EGR valve, had an engine remap from dynachip, cleaned the red ECU connector and seen that the intercooler is fairly clean. Still got to change the air filter and clean the MAP sensor but will these two things really make that much difference?

If the air filter is clogged up. Yes.

Are your tyres flat?

thebiglad · Mar 24, 2015

danam1 said:
So I've been continuing to check my mpg. I've done what thebiglad suggested and been brim to brim checking so I'm very accurate. Lately I've been doing mainly short runs but I'm only getting 20.5 mpg! Just to recap:- I've removed the EGR valve, had an engine remap from dynachip, cleaned the red ECU connector and seen that the intercooler is fairly clean. Still got to change the air filter and clean the MAP sensor but will these two things really make that much difference?

These are the two things you should have done first.

Plus ensure your tyre pressures are up to at least front 32psi; rear 38psi.

danam1 · Apr 7, 2015

Front tyres were fine (32psi), rear were only 30psi so pumped them to 38psi, MAP was filthy so cleaned it with brake cleaner and air filter was black!! Now replaced. I'm in the the middle of the new mpg check so will post back here with the results. Thanks

td5nut · Apr 7, 2015

danam1 said:
Front tyres were fine (32psi), rear were only 30psi so pumped them to 38psi, MAP was filthy so cleaned it with brake cleaner and air filter was black!! Now replaced. I'm in the the middle of the new mpg check so will post back here with the results. Thanks

28psi front-38 rear

danam1 · Apr 7, 2015

thebiglad said:
These are the two things you should have done first.

Plus ensure your tyre pressures are up to at least front 32psi; rear 38psi.

^^^^^^^^^^^

td5nut · Apr 7, 2015

td5nut said:
28psi front-38 rear

just what it says in the handbook

Td5 mpg

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