Downhill-coast question

[New2Import]

Why does the M seem to hold its rpms while going down hill or at a coast? I put it in neutral just to see the difference and it speed up and rpm drop to idle which it should do. Seem like this is a waste of gas and harder on the transmission. This is something that needs to be programmed out for sure. BTW does anyone offer custom tuning for the M?

[jankenpo30]

Why does the M seem to hold its rpms while going down hill or at a coast? I put it in neutral just to see the difference and it speed up and rpm drop to idle which it should do. Seem like this is a waste of gas and harder on the transmission. This is something that needs to be programmed out for sure. BTW does anyone offer custom tuning for the M?

I noticed that on mine too....especially when gas was close to 5/gal. I pop it in neutral and noticed almost a 1k rpm difference.

[palincal]

Grade logic. Most newer heavier cars use engine braking on downhill to prevent overheating of brakes and picking up too much speed. Engine and transmission are designed to take that beating for a sustained downhill drive while brakes are not.

[fiveliterbeater]

Grade logic. Most newer heavier cars use engine braking on downhill to prevent overheating of brakes and picking up too much speed. Engine and transmission are designed to take that beating for a sustained downhill drive while brakes are not.

exactky what he said; most newer luxury cars can sense when you are on a down-grade and therfore use engine-braking to help slow the car down without wearing down or over-heating the brakes. i had two previous lexus cars that did the same thing, one was a 00 ES and the other was an 03GS

[New2Import]

Well I guess Im not use to the this luxury thing. I dont like it. Takes the control of the driver away for one and its a waste of fuel. Are there any programmers out that can custom tune the PCM yet on these cars?

[ken in az]

Are there any programmers out that can custom tune the PCM yet on these cars?

Nope....not even the big name tuners have cracked the CAN communication system to control the TCM. TCM is the transmission control computer and it works indipendantly of the ECU and communicates with it via a network just like a LAN for office computers only a little different.

They may crack it someday, but as far as I know I'm the first M45 in the USA to have their ECU tuned....and it's been a month and a half since I started with uprev and still nothing - starting to have my doubts about it even coming to fruition.

[palincal]

Takes the control of the driver away for one and its a waste of fuel.

Waste of fuel? As long as you are coasting downhill without having to step on gas, you are not using any fuel. With grade logic, your decent is much more controlled.