Cruise Control

[Kimberley Scott]

Read and reread the entire driving manual. No mention of decent control (no suprises there). It mentions that the car will brake using engine braking alone when going down hills. Given this and the fact that the recommended changing speed for six gear is 85 to 90 km/h. Then I can only deduce that the cruise control system is coasting downhill using engine braking to keep it within a couple of km/h of the set speed and then firing up again to maintain speed. Giving me a intermittant hesitation.

As far as the driveline shunt everyone keeps refering to, yes I have felt it and at first it pissed me off. Then I looked at when it happened. I can only conclude that it happens when I have been lazy and slightly depressed the accelerator before fully releasing the clutch past its friction point. I drive a nissan patrol as well and when I do this there is a driveline shunt as well. As well there should be because this behaviour is mechanical cruelty. Given that the XR6T is a performance car with small tolerances for mechanical cruelty. I would suggest that most of the problems experienced are mainly driver error.

Just putting it out there guys, we are not all 100% of the time red hot drivers. Try it and see for yourself.

Expecting a bit of flack over this, but keep up the good work guys enjoying the site.

Scotty

[BA_Turbs]

Read and reread the entire driving manual. No mention of decent control (no suprises there). It mentions that the car will brake using engine braking alone when going down hills. Given this and the fact that the recommended changing speed for six gear is 85 to 90 km/h. Then I can only deduce that the cruise control system is coasting downhill using engine braking to keep it within a couple of km/h of the set speed and then firing up again to maintain speed. Giving me a intermittant hesitation.

As far as the driveline shunt everyone keeps refering to, yes I have felt it and at first it pissed me off. Then I looked at when it happened. I can only conclude that it happens when I have been lazy and slightly depressed the accelerator before fully releasing the clutch past its friction point. I drive a nissan patrol as well and when I do this there is a driveline shunt as well. As well there should be because this behaviour is mechanical cruelty. Given that the XR6T is a performance car with small tolerances for mechanical cruelty. I would suggest that most of the problems experienced are mainly driver error.

Just putting it out there guys, we are not all 100% of the time red hot drivers. Try it and see for yourself.

Expecting a bit of flack over this, but keep up the good work guys enjoying the site.

Scotty

<{POST_SNAPBACK}>

Seriously mate, you're missing the point, that's what I said in the first place.

[Kimberley Scott]

I dissagree.

[Antisocial]

I too have a 6 speed manual.

I do not use the cruise control when going down steep hills, as this same thing you are describing sh!ts me to tears.

The cruise only applies the throttle.

The PCM controls the injector duty cycle and ignition.

As far as I am aware most modern cars turn off the fuel and ignition to various cylinders when the car is coasting under certain circumstances. Those being the car is at normal operating temp, the road speed is above 50km/h, the throttle is not pressed and of course the car is not in neutral or the clutch is in.(if either of these occurred, and the motion of the car was not causing the engine to turn it would stall)

You can notice this effect when coasting down hill with all of the above met, look at the instant L/100 on the trip computer. Then shove it into neutral and you will see the L/100 go from about 0.3 in gear, to a few L/100 in neutral.

This is because it takes more fuel to Idle than to coast...

Remember to put it back into D not R for you Car steerer's...... manual Driver's can just put the clutch in.

Given the above I think there is a bit of hysteresis or overlap in this situation where the cruise effectively gets on and off the go pedal all the time, the PCM turns the cylinders on and off in response, and this combined with the drive train slack or "clunk" exacerbates this situation.

[Falchoon]

You can notice this effect when coasting down hill with all of the above met, look at the instant L/100 on the trip computer. Then shove it into neutral and you will see the L/100 go from about 0.3 in gear, to a few L/100 in neutral.

This is because it takes more fuel to Idle than to coast... 

<{POST_SNAPBACK}>

Are you sure that's right Alex? Im sure in my auto BA n/a work ute the fuel consumption is less when putting it in N and coasting down a hill.

As for Kimberley's original question, sorry I can't help, never experienced it, my car is auto anyway.

[Antisocial]

Are you sure that's right Alex? Im sure in my auto BA n/a work ute the fuel consumption is less when putting it in N and coasting down a hill.

<{POST_SNAPBACK}>

Bet you it's not.....

[seventytwo]

Not sure if this is related but at very light throtle openings my 6 speed tends to surge a little and I put this down to throtle body being controled digitaly. As it it may not be able to match the accellerator position exactly

as I believe the throtle body only has a set number of postions so it may be jumping between two of these postions creating the slight surging.

back to the cruise control, maybe the shudder you are feelin is, when you are traveling down a hill the cruise control is using engine braking to slow the car ie the butterfly is fully shut. Now if you where having this throtle postion jumping it may feel like a shudder like you discribe.

note: this is just a theory and I have facts or data to back it up so draw your own concultions

[tab]

Are you sure that's right Alex? Im sure in my auto BA n/a work ute the fuel consumption is less when putting it in N and coasting down a hill.

<{POST_SNAPBACK}>

Bet you it's not..... :banghead:

<{POST_SNAPBACK}>

Bet you you're right YCL

[Kimberley Scott]

Cheers guys

[fraggle]

Not sure if this is related but at very light throtle openings my 6 speed tends to surge a little and I put this down to throtle body being controled digitaly. As it it may not be able to match the accellerator position exactly

as I believe the throtle body only has a set number of postions so it may be jumping between two of these postions creating the slight surging.

back to the cruise control, maybe the shudder you are feelin is, when you are traveling down a hill the cruise control is using engine braking to slow the car ie the butterfly is fully shut. Now if you where having this throtle postion jumping it may feel like a shudder like you discribe.

that's what I would have said I normaly use the cruise in the suburbs in 3-4 at 50-60kms on long streets ( no speeding notices ) and when you go down an incline or hill you do get a surging feeling.

I also have a six speed if going on a hilly section of road cruising I my self only use fifth use sixth for the flat stuff and the high speed stuff

As for the sudder it might be you are at the point that the car needs to give a little throttle then off then on agian some time with in seconds of each other.

Hope this helps and if its a problem I hope you get it fixed