AC and Jerky Gear Changes

[x_paradoxal_x]

I rarely put the AC on in my car, even when it is hot, but the other day I noticed something odd. When the AC is on, not even full blast, the gear changes are jerky as hell no matter how careful I am with the clutch. I turn the AC off, and the gear changes go back to being very smooth. I have also noticed a noise in the car when you turn the AC on, I reckon this is the AC motor/unit/whatever-it-is-called. I have read bits and pieces on this forum that the AC in the GTI is a power leech, which is not a huge surprise.

Has anyone else with a manual GTI noticed this?

 

[stuck24]

yes... the revs drop VERY quickly and you must compensate with quick shifts and giving the throttle a bit of a push as you let off the clutch...

It'l take practice... be patient, but do realize those revs drop fast w/ the a/c on.

 

[zecpull1]

I could understand with an Auto. But it would seem weird with a Manual,as the only thing that would make it Jerky is how you let out the clutch. I have a Manual and have not noticed the AC making any difference in my car.. and it doesnt even effect mileage that much.

 

[Hilfloskind]

It's a huge difference. I have to assume it's by design so the compressor feeds off the engine power in a parasitizing way, likely to aid in efficiency. At least I hope that's it so I don't feel like it was shitty decision making and engineering.

 

[norsairius]

yes... the revs drop VERY quickly and you must compensate with quick shifts and giving the throttle a bit of a push as you let off the clutch...

It'l take practice... be patient, but do realize those revs drop fast w/ the a/c on.

It's a huge difference. I have to assume it's by design so the compressor feeds off the engine power in a parasitizing way, likely to aid in efficiency. At least I hope that's it so I don't feel like it was shitty decision making and engineering.

I believe both of you are correct. It's not a result of bad decision making or engineering, it's just how it works. I've noticed this in the manual cars I've driven before. This is normal.

I think automatics are a bit better because they can adjust for you. Plus, slushboxes are, well, slushy so you won't notice it. The DSG on the other hand, well, that thing shifts so quickly anyway it doesn't seem to matter how quickly the revs drop.

With a manual, you will need to compensate (the car's computers won't help you here since you control the shifting). You could try getting on the throttle a bit sooner while shifting to see if that helps.

 

[x_paradoxal_x]

I could understand with an Auto. But it would seem weird with a Manual,as the only thing that would make it Jerky is how you let out the clutch. I have a Manual and have not noticed the AC making any difference in my car.. and it doesnt even effect mileage that much.

See that is what I thought at first as well, I thought it was just me not being careful enough with my left foot. But as I tested it with the AC on and then off (this is all city driving by the way, so stop and go), I noticed it was jerky with the AC on. I haven't really noticed the mileage drop on the MFD too much, usually it changes by 1 or 2 less on the current reading. But even then, it may just be my imagination. I know the AC uses fuel, I may not be able to see it, but it has to get power somehow. When I do use the AC I use it on for a few minutes, then off again.

Anyways, thanks for the input guys. I will try to shift quicker when I have the AC like you mentioned.

 

[x_paradoxal_x]

I believe both of you are correct. It's not a result of bad decision making or engineering, it's just how it works. I've noticed this in the manual cars I've driven before. This is normal.

I think automatics are a bit better because they can adjust for you. Plus, slushboxes are, well, slushy so you won't notice it. The DSG on the other hand, well, that thing shifts so quickly anyway it doesn't seem to matter how quickly the revs drop.

With a manual, you will need to compensate (the car's computers won't help you here since you control the shifting). You could try getting on the throttle a bit sooner while shifting to see if that helps.

I've been driving TDI manuals for 2 years now, and just got a GTI a couple months ago, and the way you have to shift is completely different. In my TDI Golf, you have to let the revs drop between shifts, where as in a petrol engined car you can shift very quickly. So when I drive my GTI I have to remember I can shift much quicker, although I have to be more careful to get the shifts smooth. I have been living in a country where AC is not needed, so this whole driving manual with AC on is new to me. South Carolina is getting bloody hot.

 

[VEGASVWGTI]

I have been living in a country where AC is not needed, so this whole driving manual with AC on is new to me. South Carolina is getting bloody hot.

Just be grateful you do not inch along in traffic at 5pm in June when temps are in excess of 115 degrees. If you think your manual is bad try a DSG on for size under these conditions. Never again as long as I live in any place where the day time high exceeds 90 degrees. "Jerky" is an understatement.

BTW stage 1 brings back alot of smoothness under these conditions in the manual.

 

[x_paradoxal_x]

Just be grateful you do not inch along in traffic at 5pm in June when temps are in excess of 115 degrees. If you think your manual is bad try a DSG on for size under these conditions. Never again as long as I live in any place where the day time high exceeds 90 degrees. "Jerky" is an understatement.

BTW stage 1 brings back alot of smoothness under these conditions in the manual.

When I lived in the UK, one of my lease cars for my family was a TSI golf with a DSG. I hated driving it in bumper to bumper traffic on the motorway, it was so jerky I wanted to drive it into a wall. I can't even imagine that paired with AC and the heat. I used to live in southern New Mexico so I know how the hot weather is, it is a b**** in the summer for sure.

 

[Marvin]

In my last two Golfs, including the current one, I don't notice any change in engine speed, revs, jerkiness at all when the Aircon is switched on. If there were to be a change in engine revs, this is compensated by the engine's management system.
Perhaps your problems might be related to the ambient conditions which I guess are much more extreme in some US states. It can get hot here but rarely more than, say, 35°C (95°F) but my car is utterly smooth when it is on.
Perhaps for the person who says that he hardly ever uses his aircon, perhaps his system is buggered due to lack of use and thereby putting extra strain on the engine because of a damaged compressor.
When I used to have cars with cruder aircon systems, where you could actually hear the compressor engage when the aircon button was pressed, there was a slight fall in revs then but not with my MK5 or MK6 Golfs.

Maybe Golfs imported into N.America have higher rated compressors, resulting in more engine drag?

 

[ncelk]

My GTI does it and my Miata does it as well when the compressor is running.

 

[Marvin]

Perhaps it is because some of you guys have messed around with your cars removing the car's innate smoothness that is to be found in stock cars and not modified ones?

 

[stuck24]

^^^ NO, my car is stock. And the a/c is super ice cold. But with it on at first, it will drop revs like hard rain...

quick shifts and get on the throttle a bit quicker... my advice to OP

 

[VEGASVWGTI]

When I lived in the UK, one of my lease cars for my family was a TSI golf with a DSG. I hated driving it in bumper to bumper traffic on the motorway, it was so jerky I wanted to drive it into a wall. I can't even imagine that paired with AC and the heat. I used to live in southern New Mexico so I know how the hot weather is, it is a b**** in the summer for sure.

This is a very real problem. The only way to overcome some of the problems with this vehicle paired to a DSG under the circumstances I described above is to drive the vehicle in S mode and shift smoothly up 1-2-1-2-3-2-3-2 ect and down as traffic allows, similar to what you would do with the manual though the DSG does not replicate this as effectively and you also do not have the relief associated with neutral- it feels a bit odd compared to a true standard. Regardless of that though it works fairly well reducing the jerk which I think is mostly related to a dead throttle under heavily heat soaked conditions and responding late and you lifting off the gas to soon ect. The DSG is fantastic even if a bit boring at times and I loved mine on my 08 FSI GTI in the winter, but the vehicle performance in the summer paired to it was almost unbearable and that dog and pony show will never be repeated. So far the manual has proved to be worlds better in this regard as you control completely the gear change with the natural relief of nuetral and learn to carefully and consistently predict the performance of the throttle response including the hesitation/interruption dead spots in the powerband under adverse driving conditions.

With that said more extreme hot weather testing under real world conditions should be done with these cars as they are quite prone to temparture related performance interruptions.

Perhaps it is because some of you guys have messed around with your cars removing the car's innate smoothness that is to be found in stock cars and not modified ones?

Are you refering to ecu modifications? This has only reduced the problem, not added to it as there is more horsepower and torque available to compensate for the sapping of power in the summer. Makes it smoother to drive in the heat with the A/C on at least in the manual anyway.

 

[Marvin]

In all honesty I have never experienced this problem in any car with A/C. Maybe it is because I have never spent very long periods in traffic jams in hot weather with the Aircon on. I certainly have never had to adapt my driving technique (always cars with manual boxes) or change gear slower/quicker.
Perhaps you guys ought to have your cars seen to by the VW dealerships. Maybe the problem is worse on GTis or diesel cars.
I have only driven two automatic cars in over 55 years of driving and frankly have no wish to repeat the experience. Fine intitially until the novelty wears off but the DSG box is OK when in motion but its sudden uptake of drive is a nuisance and makes smooth progress not always possible - the Mechatronic units often play up and need replacing. My friend has had so much trouble with his Jetta and his DSG box!