How to get the best out of the Auto.

[old Jack]

As the title says "How to get the best out of the Auto" this thread is for the PB/PC owners with auto trans. It is not the best auto in the world in fact for a Smart Auto it is old technology and as such has some limitations that you need to be aware of but there are things you can do differently to get the best out of it.

The first problem I will address is fuel economy or lack of it!, manual Challengers reportedly get great economy as low as 7lt/100km and normally around the 8-9lt/100km, the autos however are a different story.

The best I could get around the city was 15lt/100km until MM fixed the communication error between the Engine and AT ECU's, once this was fixed the 13.5 to 14 was the normal long term consumption on the RV meter which is quite accurate on my PB. I am heavy at 2450kg kerb weight, run aggressive AT/MT tyres but they are standard diameter.

I have been experimenting with how I drive the car and even driving like a very very old Jack in "D" this is what I get.



So today I did a 30 min drive through the city using the sports mode, changing up at 2000rpm to 2200 rpm and a gentle throttle, 1st, 2nd & 3rd gears to 62kph and then into 4th and ease off the throttle to sit at 60 kph GPS at 1610 rpm with the torque convertor locked up, I have a TC lockup meter and this is what I got in a 30 min cross city commute.
Best I have ever had for this sort of driving.



So several hours later on the return commute I drove in "D" with a gentle throttle not exceeding 2200rpm and let the Auto do the work, ending up in 5th gear without the torque convertor locked up and 1650rpm. This is what I got!



Now this is only one trip so I will use the sports mode around the city for the next week or so to see what my long term average is. Certainly the engine feels more comfortable in 3rd at 30kph to 55kph and 4th at 60 to 65kph. It is certainly more responsive when you need to get out of the way in traffic.

So this is a thread/blog for the Auto trans PBer's so please respect this as we all know about the sub 10lt/100km from the manual Challengers and both the Auto and Manual Pajero's. Those with PB Autos feel free to post your figures, feedback and questions.

If I can get an average of 10lt/100km then my range is 700km up from the 520km at 13.5lt/100km and at $1.60 per litre and saving 3.5lt/100km and doing 15,000km PA that equals $840.00 after tax! Not a bad pay rise for moving a stick instead of being lazy.

cheers, old Jack.

[unknown]

Interesting concept, I will try it out and post findings here.
I wonder if ambient temp would also play a role?
Interesting to see the 28 vs 22 c in the photos.

cheers

[old Jack]

Interesting concept, I will try it out and post findings here.
I wonder if ambient temp would also play a role?
Interesting to see the 28 vs 22 c in the photos.

cheers

Agree, I will continue my test but from my research a 6C change in fuel temp is only 4.8% change in density and even with higher intake temps (less dense air) I would be surprised if it was the 30% difference I saw today.
Here are 2 threads, one is on the RV meter and the other is on temperature VS fuel consumption.

http://www2.pajeroclub.com.au/forum/showthread.php?t=36894

http://www2.pajeroclub.com.au/forum/showthread.php?t=36781

cheers, old Jack.

[Quadcam]

As the title says "How to get the best out of the Auto" this thread is for the PB/PC owners with auto trans. It is not the best auto in the world in fact for a Smart Auto it is old technology and as such has some limitations that you need to be aware of but there are things you can do differently to get the best out of it.
...cheers, old Jack.

If I can add a comment or two as an outsider so to speak (Outlander 6 speed auto), my observations with both the Pajero 5 speed auto (same as your Challengers I would expect) and Outlander 6 speed auto would correlate what Old Jack has reported.

Both autos (in normal mode) unlock the converter relatively quickly and persist in a higher gear with the converter unlocked. Shifting either to Sport mode and down a gear would lock the converter and drop the instantaneous fuel consumption noticeably. They would also hold the converter locked for much longer in Sport mode, even up significant hills. The downside with the 5 speed auto was forgetting the lever was in Sport when taking off from a stop and the auto not shifting thus ruining any fuel consumption gains.

[old Jack]

Comments in blue

If I can add a comment or two as an outsider so to speak (Outlander 6 speed auto), my observations with both the Pajero 5 speed auto (same as your Challengers I would expect) and Outlander 6 speed auto would correlate what Old Jack has reported.
Ths Challenger has a Jatco auto trans and not the Aisin auto that is in the Pajero and only has TC lockup in 4th and 5th gears unlike the Pajero that locks up 3rd, 4th and 5th (NT & NW). The Challenger has a high slip TC with a stall ratio of 1:2.04 compared to the Pajero's 1:1.85 stall ratio.

Both autos (in normal mode) unlock the converter relatively quickly and persist in a higher gear with the converter unlocked. Shifting either to Sport mode and down a gear would lock the converter and drop the instantaneous fuel consumption noticeably. They would also hold the converter locked for much longer in Sport mode, even up significant hills.
Agree, but due to the high slip TC it is very difficult to easily know when the TC is locked or unlocked. Unless you have one of these.

http://www2.pajeroclub.com.au/forum/showthread.php?t=35928

The downside with the 5 speed auto was forgetting the lever was in Sport when taking off from a stop and the auto not shifting thus ruining any fuel consumption gains.
Agree, but it is just like driving a manual without the clutch and with practice it is not a chore

cheers, old Jack.

[Quadcam]

My Pajero was an NS petrol auto which had the Jatco auto. The stall ratio was 1.62 but it was easily discernible when it was locked. I would have thought it would be easier to detect with a greater stall ratio but maybe the extra diesel torque and the partial lock mode make it harder.

I don't know if your Challengers have provision for steering paddle shifters like the Outlander but when you select Sport mode with a paddle (rather than the shifter Sport gate) the auto goes back to normal mode when coming to a stop. It is a nice improvement and as soon as you activate a paddle Sport mode re-activates.

[Rosscomatic]

I have some questions...

The other day I towed our new camper trailer down to Myalup beach just south of Mandurah in WA. Anyone who knows the road will agree that it's flat. I mean really flat!

I was getting 13.5L/100 just leaving it in auto with cruise control on,travelling at about 100ks an hour.

The trailer is about 600kg empty and we had some stuff in it, but not much really. It was only a practice trip ��

Anyway, is that reasonable fuel consumption? Any tips to perhaps improve it?

Second question is, without extra gauges etc how do you know when the torque converter comes into play? And what exactly does it do?

Thanks everyone!

RossH

[old Jack]

In blue Rossco,

I have some questions...

The other day I towed our new camper trailer down to Myalup beach just south of Mandurah in WA. Anyone who knows the road will agree that it's flat. I mean really flat!

I was getting 13.5L/100 just leaving it in auto with cruise control on,travelling at about 100ks an hour.
Was that on the RV meter or tank fill? either way that is what I would expect from the Challenger. I travel with a mate who has a NW auto towing an off road camper (900kg) and he gets better fuel economy than me on a trip his 10.5 lt/100km towing to my 12.5lt/100km at GVM and only Maxtraxs on roof rack.

The trailer is about 600kg empty and we had some stuff in it, but not much really. It was only a practice trip ��

Anyway, is that reasonable fuel consumption? Any tips to perhaps improve it?

Second question is, without extra gauges etc how do you know when the torque converter comes into play? And what exactly does it do?
Only way to tell is by rpm at a given speed for a given gear or a TC voltmeter, here is a guide to TC slipping rpms and speeds;
To give you an idea of when the TC is in a "no slip" condition the following applies in theory and with factory diameter tyres,
2nd 40kph 2200rpm no slip, any higher rpm at this speed and the TC is slipping.
3rd 60kph 2280rpm no slip, any higher rpm at this speed and the TC is slipping.
4th 60kph 1610rpm no slip, any higher rpm at this speed and the TC is slipping.
4th 80kph 2140 rpm no slip, any higher rpm at this speed and the TC is slipping.
4th 100kph 2670 rpm no slip, any higher rpm at this speed and TC is slipping.
4th 110kph 2940 rpm no slip, any higher rpm at this speed and TC is slipping.
5th 100kph 1950 rpm no slip, any higher rpm at this speed and TC is slipping.
5th 110kph 2150 rpm no slip, any higher rpm at this speed and TC is slipping.
When towing or under load if you find the TC slipping and "not catching up" try keeping the trans in a lower gear and delay the upshift until you are at 2500rpm and have been at those revs for at least 30 seconds after there has been no increase in speed for the 2500rpm setting.


Thanks everyone!

RossH

cheers, old Jack.

[Toddyh]

In blue Rossco,

.....and he gets better fuel economy than me on a trip his 10.5 lt/100km towing to my 12.5lt/100km at GVM and only Maxtraxs on roof rack

cheers, old Jack.

I found with my last vehicle that maxtrax on the roof rack would increase my highway consumption by around 1.5-2L/100km. They seem to act like a parachute and increase the drag by a huge amount. I tried them upside down, right way up and even back to back. Nothing worked except taking them off and making room in the boot.

[old Jack]

I found with my last vehicle that maxtrax on the roof rack would increase my highway consumption by around 1.5-2L/100km. They seem to act like a parachute and increase the drag by a huge amount. I tried them upside down, right way up and even back to back. Nothing worked except taking them off and making room in the boot.

Was this with the Maxtrax's just on crossbars or on a platform rack or in a basket?

cheers, old Jack.

[Toddyh]

They were in a basket. The same basket that is on my Challenger now. That's why I specifically made under floor storage for the maxtrax as I don't want them on the roof ever again.

[old Jack]

They were in a basket. The same basket that is on my Challenger now. That's why I specifically made under floor storage for the maxtrax as I don't want them on the roof ever again.

I have found no difference between my empty platform rack and 2 sets of Maxtraxs whether stacked 2 or 4 high as long as they are length ways.
When I have a spare tyre and tube on the rack and the Maxtraxs then need to go across the rack 4 high then I lose about 1lt/100km but I suspect the tyre has a bigger influence than the Maxtraxs. Thanks for the feedback Todd.

cheers, old Jack.

[PBding]

More good research and info thanks OJ.

[Goodsy]

Might try this on the PJ and report results.

[grhyso]

I found with my last vehicle that maxtrax on the roof rack would increase my highway consumption by around 1.5-2L/100km. They seem to act like a parachute and increase the drag by a huge amount. I tried them upside down, right way up and even back to back. Nothing worked except taking them off and making room in the boot.

I have a pioneer platform and have my maxtrax up there when going 4wding. I think I'll measure today's consumption driving to work on the freeway and then fit them tomorrow and try again.