Power/economy button on VS

[AttaBoy]

Hey all,

I had an argument with a mate (not in a bad way) about fuel economy when using power feature on the tranny.

He reckons it improves fuel economy by having the power 'on' instead of on economy mode.
I don't agree - as power makes your car more responsive by letting the tranny shift later or higher in the RPM range which means more fuel.

I'm going to give it a test starting next week in one full tank of fuel with power 'on' and see if economy improve which I doubt.

I normally get around 400km in one tank in economy mode. This will be interesting!!
Will post the results in a week or till emty tank.

[Grennan]

To be honest i hardly notice a different at all in fuel and "power" whenever mum gets in the car she always insists i turn it to economy but yeah i dont ever notice any difference.

I think one would assume though... power is less economical than the economy mode... otherwise the button is rendered absolutley pointless...

[NickVR]

It just changes the way it shifts and when/if overdrive is engaged

POWER
Will hold first a little longer (more noticable in VR's than VS's)
Will shift harder
When left in [D] overdrive will engage at about 85/90kmph

Economy
Won't hold first for as longer very short in comparison (more noticable in VR's than VS's)
Shifts smoother
When left in [D] overdrive will engage at any speed above 40/50 (not sure which).

Fuel economy won't change much if at all, if you want to effect the economy go lighter on the right foot. Hope this helps.

[V-ahhh]

i know this is a little of topic.. but is it a bad thing that overdrive engages so early?

[crazywog]

i prefer using economy mode aswell ataboy i own a vs acclaim myself and find i get more to the tank in eco then pwr mode i only use pwr when im using premuim and when im on the track and racing. but then again i dont understand y make such a button when they could of just built a tranny to last the same or inbetween the pwr and eco mode instead of having a button to press the tranny does it itself thats my opinion.

[14secvp]

ok i sort of tested the theory a while ago on my vp in 3rd it sits in the 30kpa map sensor range which has about 40 degrees timing and minimal ve as soon as it goes into 4th it goes to the 40kpa map sensor range which has way less timing and more ve so its going to use more gas and make less torque cause of the timing but if you break the speed limit on the highway it will come back down too the 30kpa area but anything under 110 it uses more gas and sits in the 40kpa so it is highly possible that in power you could use less gas.my boss used to allways say keep out of overdrive unless doing more than 100 or its going to cost more gas just cause the engine is more loaded up where as in third its just freely spinning away so i never have the car in 4th apart from on the highway and its damn economical .

[sganro]

I just leave it in economy mode now. Dont think it ever made much difference to fuel ecconomy using power.

[Cheap6]

i prefer using economy mode aswell ataboy i own a vs acclaim myself and find i get more to the tank in eco then pwr mode i only use pwr when im using premuim and when im on the track and racing. but then again i dont understand y make such a button when they could of just built a tranny to last the same or inbetween the pwr and eco mode instead of having a button to press the tranny does it itself thats my opinion.

Funny you should say that as my understanding (based on quotes from GM engineers in magazine reports when the VR was released) was that the button is primarily for marketing purposes - to be able to show the customer that the car now has (had) an electronically controlled trans., going from VP-VR. The GM engineers reckoned that they could tell from the sensor inputs to the PCM what shift regime to use = no use for a pwr/econ. button.

ok i sort of tested the theory a while ago on my vp in 3rd it sits in the 30kpa map sensor range which has about 40 degrees timing and minimal ve as soon as it goes into 4th it goes to the 40kpa map sensor range which has way less timing and more ve so its going to use more gas and make less torque cause of the timing but if you break the speed limit on the highway it will come back down too the 30kpa area but anything under 110 it uses more gas and sits in the 40kpa so it is highly possible that in power you could use less gas.my boss used to allways say keep out of overdrive unless doing more than 100 or its going to cost more gas just cause the engine is more loaded up where as in third its just freely spinning away so i never have the car in 4th apart from on the highway and its damn economical .

That sounds backwards. As a general rule, lower engine speed (lower friction losses) and higher manifold vacuum/VE (lower pumping losses) help fuel economy. At the risk of getting off topic, what are the injector flow rates/duty cycle in 3rd and 4th?

[calais_cruzin]

im in agreeance with spanners, i drop back into 3rd on my vp when ever i go under 100km, y, because the car doesnt have as much strain on it, it may be in 3rd at 2600rpm doin 100km, but in over drive that 1850rpm, with half a foot to get the fuel in to get the power needed to sustain the speed it had when it was in 3rd.maybe not half a foot, but its still alot more than if in [D]. Once i get cruzin i chuck it into [D] n will only drop i back again if i need sum accel.

I hate sittin in [D] at 85km just when the convertor locks up, turns the car into a slug, but drop it back to D n she is away.

Funny you should say that as my understanding (based on quotes from GM engineers in magazine reports when the VR was released) was that the button is primarily for marketing purposes - to be able to show the customer that the car now has (had) an electronically controlled trans., going from VP-VR. The GM engineers reckoned that they could tell from the sensor inputs to the PCM what shift regime to use = no use for a pwr/econ. button.

HAHAHA wouldnt be surprized if that was the case.

[Cheap6]

im in agreeance with spanners, i drop back into 3rd on my vp when ever i go under 100km, y, because the car doesnt have as much strain on it, it may be in 3rd at 2600rpm doin 100km, but in over drive that 1850rpm, with half a foot to get the fuel in to get the power needed to sustain the speed it had when it was in 3rd.maybe not half a foot, but its still alot more than if in [D]. Once i get cruzin i chuck it into [D] n will only drop i back again if i need sum accel.

Don't confuse throttle opening with fuel consumption, it doesn't always work that way. It is possible to lug an engine at too low rpms but generally lower is better. Again, a look at the injector flow rates/duty cycle will tell the story.

[calais_cruzin]

Yeah tru, but it does help with a bit of indication on how much it mite be using.

Ok it mite be using a lil less could be the same, u really dont know, i just feel that its more eccon to drop it back, also lees stress on other components coz its not under as much strain from being a low rev in top gear.

I hate it when me dad drives me car in [D] i just dont sound healthy.

[AttaBoy]

Normally I just put in D in normal driving conditions and use the 3 for overtaking.

[quiksilv3r]

Only time mine goes out of D is for the quarter. Pwr button stays off all the time. Revs out to 5500 before changing in "economy" mode, any higher would be way out of the torque.

It is an auto - if you can control your right foot you can get it to drop back whenever you want at whatever time you want.

[AttaBoy]

Ok, half a tank have been consumed and so far the car done 148 kms. With power on.

[14secvp]

ok just checked an old aldl log the IFR reading in the aldl stream goes up from at 34kpa 1.58 and into 4th gear goes too 44kpa and gets a reading of 2.32 not a lot but more thats for sure after 110 it dips back into the 34kpa area in 4th its all got too do with load not revs once over 110 its back into the powerband a bit more and doesnt strugle so much too keep it rolling

[AttaBoy]

Tank is almost empty and so for the car clocked up 318kms.

[cxcxcxvcvcvc]

the only time the econ/power button is used in our car is when comeing onto the high way! when the button is pressed the car feels as though its dropped back a gear and the revs go higher! also the car becomes definately more responsive!!

[cxcxcxvcvcvc]

Only time mine goes out of D is for the quarter. Pwr button stays off all the time. Revs out to 5500 before changing in "economy" mode, any higher would be way out of the torque.

It is an auto - if you can control your right foot you can get it to drop back whenever you want at whatever time you want.

im pretty sure that if you boot it, even in econ mode the computer in the trans/car detects the sudden high increase in revs and automatically engages the power override feature? (it supposedly can do this without pressing the button) wich i spose would make the button pointless in most cases

[AttaBoy]

im pretty sure that if you boot it, even in econ mode the computer in the trans/car detects the sudden high increase in revs and automatically engages the power override feature? (it supposedly can do this without pressing the button) wich i spose would make the button pointless in most cases

That is exactly what i thought. But the car seems to go a little better in power because of the shift points even if you are not booting it.

[cxcxcxvcvcvc]

That is exactly what i thought. But the car seems to go a little better in power because of the shift points even if you are not booting it.

i think that may be due to the reaction time of the computer and the auto power engage system, e.g if you put the car into power mode the auto changes the shift points accordingly and holds them there untill power mode button is disengaged, whereas if you get up it the computer has to realise whats happening and then change from econ mode to power mode (automaticaly) holds the shift points and once the throttle is backed off the computer then rengages economy mode.

[crazywog]

cheap6, yes but y didnt they build that in the latest cars eg vt and onwards not vr and onwards. i think they already have in the new cars im pretty sure they have. but i find it useless either on or off doesnt make a diffrence if ur car has been shift kitted.

[commsirac]

Agree with cheap6 here. Throttle opening,isnt everything.
With the inst fuel consumption read out on my vx have been able to see what holding the car in gear with the trans does on long hill climbs, when maintaing the same forward speed lower gears use much more fuel.....lots more, I was suprised how much more......even though in the lower gear the car felt more comfortable and responsive. The same effect was noted when pressing the power button on the transmission where at some speeds it selected a lower gear for the same road speed and incline. Information on how the computer comes to its numbers is thin on the ground, does it give real values based on air intake speed, throttle position and road speed.....or does it have predetermined numbers set within that correspond to throttle position road speed and gear selected. Im suspecting its the former as so far the trip computer gets the sums right every time when looking at the actual fuel used and kms travelled.
My VX wont engage overdrive until 70km/h is reached in power or economy.....others suggest overdrive in earlier models engages at 40-50km/h. Is this correct operation for the VX?. Consumption at 70kmh is 1L/100km less than for 60kmh possibly solely based on being in overdrive.
In regards to attaboy's trial, unless the use is totally stopping and starting and going through the gears or climbing long inclines, then I dont think there will be much of a difference.