Odd engine braking

Something a bit odd happening with the D40. As I go down hill for an extended period of time, the engine braking seems to come on significantly. Thats not the best description.
As I'm coasting down hill, it suddenly brakes, engine revs go up, and according to my Scangauge, Kws drop to 0.00. Its like the motor has switched itself off - but obviously it hasn't as its reving away. And the vehicle is slowed dramatically? I then hit the accelerator and with a slight delay, it re-engages?
Is this normal - sort of like its dropping down a gear by itself? Almost Prius like?

When mine did something similar I thought it was a nifty thing that I'd probably lose the next time a mechanic got his hands on it, but it turns out that it's a D40 feature.

Mine behaves a little differently to your description. If I come over the crest of a hill and do not touch the brake at all then my car does nothing "different" - it will gravity-accelerate down the other side. Note, my left foot is never used to brake and I often curl it towards the seat, so I cannot ever make the mistake of accidentally riding the brake.

If I am driving on a downhill slope and touch the brake, the gearbox will kick down and I can release my foot from the brake. My Nav will hold the speed unless the hill is too steep.

I think it only kicks back to third, and no lower. It will not kick back if I turn the overdrive off.

I happen to like that. It's not rough, or harsh braking - it's very smooth. If yours isn't, it might need some adjustment?

Tony is right and his description follows exactly what my Nav does. I'm more used to just dropping the foot off the loud peddle and whether it's on the brake or not the engine brake takes over which is the way trucks do it but the Nav is slightly different. Can't say I've noticed what the Scangauge is reading and I don't often have it reading kws anyway but I shall look tomorrow.

Thanks guys - sounds all normal. Still new to the vehicle.

rambada said:

according to my Scangauge, Kws drop to 0.00

Click to expand...

Fuel cut. That's why in modern cars it's more efficient to keep it in gear downhill rather than idle in neutral - idling consumes more fuel.

Does the D40 have a variable vane turbo? Is it starving the engine of air to brake rather than closing off the exhaust?

As far as I was aware it's a variable vane. It's a Garrett GT2056V (the 6 might be a B, I'm not sticking my head that far in and my eyes aren't what they used to be). Garrett don't list the 'V' version on their web site so it might be a "special order". The manual doesn't say much about it either.

However, it's been mentioned several times to me that it is a variable vane turbo. I guess that's what the 'V' is for? Someone else might have a more definitive answer.

D40 turbo is variable vane. should be some pictures around of it.
the variable part is ONLY on the exhaust side. it closes to increase gas speed to spin the turbo faster. so it could possibly close the vanes to increase backpressure to help with engine braking.
however cutting the fuel does a fairly good job of that. those with EGT guage will notice the big drop in EGT's when the fuel is cut.

i thini the ecu has a couple of different fuel cut modes. as a driver you can use that to your advantage. ie tap the brakes going down hill, fuel cut kicks in, then keep off the throttle untill the last possible moment. save a bit of fuel but your driving might look a bit erratic.