Diesel engine remaps... The truth?

[Somnophore]

I keep seeing adverts for remaps, for disels especially that say they increase power and fuel economy, sounds like bks to me, what's the truth, and if it is true how can it be so, ie how can you get more power using less fuel.

[Bibbs]

With petrol cars, thin then mixture and you'll get more power. Adding more fuel lowers your power, but runs the engine cooler.

I'd assume diesels are the same.

[dnb]

The simple answer is that you trade off meeting type approval emissions requirements with fuel economy. The car only has to pass MOT emissions after it is sold from new.

[pilchardthecat]

Power, yes. Fuel economy, no.

Based on about 120k miles in remapped BMW diesels.

[Chris_w666]

Power yes.

Fuel Economy Yes, but only if you don't drive it quickly because of the extra power.

The big question is how much stress does the remap put on your components? I can guess some cars can cope with conservative maps very well, some will be under stress after even a minor remap, some remaps will take an engine to beyond its safe operating limit.

[pilchardthecat]

Chris_w666 said:

Power yes.
Fuel Economy Yes, but only if you don't drive it quickly because of the extra power.

Yes, that's what all the remap people say in their advertising.

It's bks though, in my experience... which is extensive, (see above).

[Welshbeef]

Were your BMW maps economy power or race maps? Were they autos and what about reliability?

[Chris_w666]

pilchardthecat said:

Chris_w666 said:

Power yes.
Fuel Economy Yes, but only if you don't drive it quickly because of the extra power.

Yes, that's what all the remap people say in their advertising.

It's bks though, in my experience... which is extensive, (see above).

48mpg before a remap, 55mpg after (Over 20,000 miles) I would say that proves it isn't always bks.

[Somnophore]

I just saw one for the Lupo 1.4tdi, remap takes it from 75bhp to 100bhp and more torque, and supposidly better mpg, just think a map that's added 33% more power doesn't sound likely to give better economy

Edited by Somnophore on Saturday 13th March 18:51

[Welshbeef]

The reason they give better economy is you can use a higher gear on average to give the same pace as previously or drive in 6 th for longer thus use less fuel in theory. Can owners use less power once they have it if not then economy would be the same or decrease

[jamiebae]

You need to know the car can take the extra power without breaking too. As an example I know the clutch and DMF on the (Euro market only) Mondeo Mk3 TDDi 90ps version are very marginal and will fall to bits if the car is remapped to 115+ps. I would expect the 1.4TDi Lupo to be similar, it's a 25% increase in power and I'm pretty sure the gearbox is a 1.4 specific one and not designed to deal with the extra power and torque a remap would give.

[y2blade]

Chris_w666 said:

Power yes.

Fuel Economy Yes, but only if you don't drive it quickly because of the extra power.

this is the part people don't understand

I can't speak for Turbo Diesel cars but
my petrol turbo is better on fuel since the remap in all situations APART from Wide open throttle...exactly what you'd expect

Edited by y2blade on Saturday 13th March 19:02

[TheEnd]

if you think about it as an improvement in efficiency, it'll all make sense.

[y2blade]

TheEnd said:

if you think about it as an improvement in efficiency, it'll all make sense.

exactly

[Welshbeef]

y2blade said:

TheEnd said:

if you think about it as an improvement in efficiency, it'll all make sense.

exactly

or in laymans talk you can drive up a hill for longer in 6th than you could do previously.

I'd love to remap my car but don't think I ever would as I prefer STD cars if you want a faster car buy one in the first place better brakes suspension etc

[nottyash]

I had a Skoda Fabia VRS, which I bought new and remapped after 6000 miles.
It is a standard 130bhp 1.9 VAG PDI unit, afterwards I had approx 185-190bhp, torque was massivly increased. I used the car on long motorway trips, and the car was 2 MPG better than pre remap. However it was 2 MPG worse around town. Its a very small price to pay for such a huge inrease in power. I was very impressed.
Manafacturers sell cars with MPG figures based on unrealistic driving speeds, mapping the engine accordingly, so on paper the figures look good to the buyer, when in reality if you drive on a motorway at higher revs the MPG is not at its optimum, so in effect you are mapping a car to be more efficient at a higher speed as well as increasing fuel, boost and engine timing to suit...if that makes sense. Another angle is manafacturers tune cars to run on poorer quality diesel than is available in the UK hence we are able tpo achieve that bit more.
You cant tar all diesels whith the same brush, as you will not make the same power gains across the board.
The VAG PDI engine, and Alfa/ Fiat diesels I know can achieve a lot more than standard.

[lewis s]

I have a mk3 mondeo turbo diesel, would that be safer to remap than the 95ps one stated earlier? It all seems a bit too good to be true tbh for the sake of a few hundred pound
s.

[cptsideways]

If you have an understanding of how modern diesels work you'll understand why its possible.

EG: Advancing the injector timing (& hence torque) raises EGT's but gives duff Nox emissions, changing the timing does involve adding more fuel.

Adding fuel on a diesel has the opposite effect to a petrol it raises EGT's not lowering it like petrol.

All modern cars are emissions restricted on their engine maps by a huge margin.

[jamiebae]

lewis s said:

I have a mk3 mondeo turbo diesel, would that be safer to remap than the 95ps one stated earlier? It all seems a bit too good to be true tbh for the sake of a few hundred pound
s.

I understand the 115ps version uses a different clutch and flywheel to the continental 90ps model. Mine was still going strong on the original clutch, pump and flywheel (TDDi model) at 150k miles when I got rid of it.

[Sir Bagalot]

I had mine done. Gained 25% in power, fuel economy I saw no difference whatsoever. The other difference I saw was a slipping clutch in a certain gear between a certain rev range.