[teaston]

I contacted TDI Tuning to find out when they'll have their M40d tune available, to which they said soon but it will be a Twin Channel box instead of the current Triple Channel I have on the 335d.

I've looked at their website and they only list a Twin Channel box for the 335d now too, so I asked why and his reply was "The only difference between the twin and triple is the amount of connectors that the engine requires so it wont make a difference to the performance or economy, it will still work fantastically for you"

Now that sounds like BS to me, the third channel monitored engine revs which they market as improving power delivery, so does anyone understand what's going on? :

[KCH1984]

I was always under the impression that the triple channel boxes didn't deliver any more power than the dual channel boxes as the mechanism for doing so was the same in both cases (increased fuelling). However, the triple channel was supposed to make for a smoother delivery as the box could vary the amount of increased rail pressure depending on engine speed as opposed to just looking at accelerator position.

On the 30d engine I've run both dual and triple channel boxes and the triple channel is a definite improvement. With the dual channel box I suffered from fuel cut where I assume the box was asking for fuelling at higher rpm the stock fuel pump just couldn't deliver.

I wouldn't have been surprised to see the first boxes appear for the m40d being dual channel, but it surprises me they've dropped the triple channel box for the 35d.

Edit - triple still available for the 30d

[teaston]

I questioned his answer and this is what he came back with:

"It comes down to each specific engine and what it requires to work as efficiently as possible, the vehicles that require the triple system need to extra information so the system can work perfectly, our technicians have informed me that they envisage that your new vehicle will only require the twin system, we will have more information within the coming weeks so we can refine the performance and economy stats, if at that point they decide it requires the triple set up that is what we will make available for yourself."

[NISFAN]

Cost savings.

All a diesel needs for more power, is increased air flow (higher boost pressure) and/or higher fuel enrichment (fuel rail pressure). The stock ECU already controls how and when to give these....the box just turns the volume up.

You only need revs if you want to add or subtract the above at particular revs to, say, limit torque.
Most will end up whacking it up to map 10 anyway (full power everywhere), where the intricacies of rev dependant control does not work. So why offer a more costly option, when most wont even use it?

[teaston]

Originally Posted by NISFAN

Cost savings.

All a diesel needs for more power, is increased air flow (higher boost pressure) and/or higher fuel enrichment (fuel rail pressure). The stock ECU already controls how and when to give these....the box just turns the volume up.

You only need revs if you want to add or subtract the above at particular revs to, say, limit torque.
Most will end up whacking it up to map 10 anyway (full power everywhere), where the intricacies of rev dependant control does not work. So why offer a more costly option, when most wont even use it?

Thanks for that explanation Gordon, it makes complete sense. I have mine one setting below max, but I guess these rules still apply, so I’ll be ok with the twin channel one.

[KCH1984]

Originally Posted by teaston

Thanks for that explanation Gordon, it makes complete sense. I have mine one setting below max, but I guess these rules still apply, so I’ll be ok with the twin channel one.

I think the module is the same anyway so am guessing when they reprogramme it for you all it will need is the dual channel harness?

[teaston]

Originally Posted by KCH1984

I think the module is the same anyway so am guessing when they reprogramme it for you all it will need is the dual channel harness?

Yes they said they can reprogram mine to Twin Channel and the new harness is included in the £119.99 charge.

[NanasBack]

Two possibilities spring to mind.
It's nigh impossible to get to the speed sensor.
Or it's only necessary to know when the rpm is above a certain level and this can be determined from the other two signals.

[teaston]

Originally Posted by NanasBack

Two possibilities spring to mind.
It's nigh impossible to get to the speed sensor.
Or it's only necessary to know when the rpm is above a certain level and this can be determined from the other two signals.

Speed sensor and boost sensor are right next to each other so just as difficult to get to, on the 335d that is.