Gearbox Recondition and 6-Speed Conversion
- Thread starter timmus
- Start date
timmus
A2OC Donor
That does flesh things out nicely, Spike. Thank you!
MikeMars posted the 'onion curves' for the 1.9TDI somewhere on here. When I drove Mike's car, he had his ScanGuage set to display engine load. Surely enough, if you try to drive too slowly in 6th gear, the engine starts to chug and the load reading goes up, resulting in more fuel being burnt. With my previous 0.659 5th, I'd try to time the change-down to 4th such that I used 5th for as long as possible, but without entering this zone. After the change to 4th, the car would rev a little higher than ideal from an economy perspective.
However, with a standard 5th as well as a 6th, the downwards change feels much more normal and requires less thought, as the gap between the gears isn't stretched. Consequently, if I enter a 50mph limit on an incline, where 6th starts to splutter a bit, I simply change down into 5th, keeping my engine spinning in a low-consumption part of the BSFC graph (onion curve).
Cheers,
Tom
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MikeMarsUK
A2OC Donor
For reference, here is the chart:
http://ecomodder.com/wiki/index.php...aps#Volkswagen_Jetta_TDI_1.9L_ALH_1999.5-2003
I find that the sweet spots are:
* 1250rpm for very low load (downhill, steady low speed driving, etc),
* 1400rpm for steady medium loads
* 1750rpm peak efficiency (gentle hills, 60mph, 197BSFC on the chart)
* up to 2000/2200rpm when you want to accelerate (torque peak)
I drop down a gear if I anticipate a need for extra engine load (for example, getting ready to overtake)
Every once in a while the engine needs a proper workout, all the way to the red line, to keep it free of soot.
As Spike says, it is stressful for the gearbox to be at low rpms & high load.
MikeMarsUK
A2OC Donor
If you want to try out mine, my offer still stands
(Only requirement is to make sure that your insurance covers my car at least 3rd party). A 6th gear upgrade is very expensive, granted, but far cheaper than buying a new car (=depreciation for less than one year).That's an open offer - if anyone wants to try my 6th gear, just ask at a social or if you happen to be passing though north Hampshire or west Surrey.
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jarmoke
Member
My personal opinions, based on my 1.4TDI 75hp.
I would not recommend to drive under 1600rpm (not at least with 4th and 5th gear) because from engine sound it can clearly be heard that it is not good rpm value for this motor, running of engine sounds heavy and "not optimal". Of course in 1st and 2nd gear lower rpm's can be used. Lower RPM's can be also used with very low load as MikeMarsUK mentined.
Mentioned 1750 and above is very good when there is up hill or something heavier.
I have driven the car over 3000km and when I bought the car it was not nice to drive under 1800rpm, so situation has become better. In beginning I also tried to drive so that the driving style could clean the engine a bit, and it seemed to help (I also used some 2T oil with diesel). So possibly there is (but I do not believe there is) still something different in my car than the others, but based on my experience of small (under 2 litres) diesel engines low rpm's are not very good with factory settings. -> Situation becomes different after car is tuned with dyno or some similar test bench, for example our other car with 1.9TDI changed a really really lot after tuning (can be driven with any RPM over 1000 if wanted but that is not good for power transmission parts)). When I have time to do it, A2 will also be tuned and after that I believe lower RPM's are usable.
As mentioned, this is just my opinion based on only one 1.4TDI A2.
Maso
Member
Interesting Jarmoke.
I have a TDI90 and i do run under 1500rpm at times with 4th & 5th but mostly when no load on engine such as downhill or straight roads that slants very little degree downwards.
I tend to go with the feel of the engine to where is starts to vibrate a lot and "cough" when under gas it is of course isnt well for the engine staying on low rpm's. Mostly i feel that which to my surprise wit my TDI90 is that it in general isnt made to go under 1700-1800rpm due to that the engine vibrates a lot with much noise when u give gas and when this happens i change down a gear but often tend to land on råm above 2000rpm which ticks me off. Will look to optimize the curve n to tune up the engine with a new software/chip to make it more optimized since i have heard it here on this forum that it does a lot for the drive characteristics.
I have a TDI90 and i do run under 1500rpm at times with 4th & 5th but mostly when no load on engine such as downhill or straight roads that slants very little degree downwards.
I tend to go with the feel of the engine to where is starts to vibrate a lot and "cough" when under gas it is of course isnt well for the engine staying on low rpm's. Mostly i feel that which to my surprise wit my TDI90 is that it in general isnt made to go under 1700-1800rpm due to that the engine vibrates a lot with much noise when u give gas and when this happens i change down a gear but often tend to land on råm above 2000rpm which ticks me off. Will look to optimize the curve n to tune up the engine with a new software/chip to make it more optimized since i have heard it here on this forum that it does a lot for the drive characteristics.
jarmoke
Member
It seems that we have common view and understanding here and figures seems very reasonable for remapped car (I assume).
Yes Maso, based on my experience with 1.9TDI remapping is must thing for smooth and relaxing driving. In my opinion only correct way to do engine tuning is remapping with Dyno or similar equipments where curves can be mapped individually for every car. I have no experience of "general chips/programs" which are just installed to car but not tuned up, except somewhere from year 2000 when curves were too agressive and not comfortable to drive in my friends VW TDI. For sure they are better that factory tuning, but at least in Finland there is no difference in price (almost not at all) and in general I do trust more the professionals (anyone can purchase needed HW and start to install some general maps without real tuning). And at last but not least, why not to do tuning by correct way when start to do it
Yes Maso, based on my experience with 1.9TDI remapping is must thing for smooth and relaxing driving. In my opinion only correct way to do engine tuning is remapping with Dyno or similar equipments where curves can be mapped individually for every car. I have no experience of "general chips/programs" which are just installed to car but not tuned up, except somewhere from year 2000 when curves were too agressive and not comfortable to drive in my friends VW TDI. For sure they are better that factory tuning, but at least in Finland there is no difference in price (almost not at all) and in general I do trust more the professionals (anyone can purchase needed HW and start to install some general maps without real tuning). And at last but not least, why not to do tuning by correct way when start to do it
Maso
Member
It seems that we have common view and understanding here and figures seems very reasonable for remapped car (I assume).
Yes Maso, based on my experience with 1.9TDI remapping is must thing for smooth and relaxing driving. In my opinion only correct way to do engine tuning is remapping with Dyno or similar equipments where curves can be mapped individually for every car. I have no experience of "general chips/programs" which are just installed to car but not tuned up, except somewhere from year 2000 when curves were too agressive and not comfortable to drive in my friends VW TDI. For sure they are better that factory tuning, but at least in Finland there is no difference in price (almost not at all) and in general I do trust more the professionals (anyone can purchase needed HW and start to install some general maps without real tuning). And at last but not least, why not to do tuning by correct way when start to do it
Great!
I hear you.
MikeMarsUK
A2OC Donor
Nice colour match I think...
One of the many jobs which Vince did for me last Friday
One of the many jobs which Vince did for me last Friday
dan_b
A2OC Donor
Oh I do like that! Jealous x2
Nice colour match I think...
View attachment 11668
One of the many jobs which Vince did for me last Friday
MikeMarsUK
A2OC Donor
Please don't tell me you need a six speed to get illumination!
This was the gearknob I picked, I liked it because it was very similar to the original (the illumination providing the OEM+ feel), recommended from the German forum.
http://www.innovativcar-tech.de/product_info.php?language=en&info=p504_1CA20.html
You do get the option of picking a 5 or a 6 gear emblem, so don't worry, you don't have to shell out for the kit as well!
Vince took the power from the ASR button which is close by. There was an issue with the leather gaiter - it had been installed at an angle so the leather was twisted, Vince modded it to correct it, and it was good after that.
Nope, just the gearknob. I actually usually keep the interior illumination to a minimum when I am driving at night, so the illumination dial is usually at the lowest setting ... just enough to see where the controls are and no more. For the photo I bumped it up to max.
Tom's idea of swapping the 6-speed emblem from an A6 gearknob is far more practical of course
Spending e70 on a gearknob was a bit of a luxury.
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timmus
A2OC Donor
Yes Dan, I have, but it's hard to be objective about it because I've done the upgrade in the middle of winter.
My most regular place of work is only 6 miles away. Given the roads between there and home, I was limited to 4 gears when I had the longer 5th. On that journey, I'm now able to use 5 gears, so I'm sure I've seen an improvement there. That said, the engine barely warms up, so those journeys are always guzzlers.
I've done a few two-hour return trips to Manchester Airport and Liverpool on the motorway and it would appear that I'm getting the same number of miles per quarter tank as I was with the longer 5th... but in near-freezing temperatures.
When the warmer weather returns, I'll be able to do a more objective comparison, though based on the evidence so far, I'm confident that my personal best efficiency records will tumble.
However, I'm delighted with the mod anyway, if only because the car's driveability is so much better than it was with the longer 5th. Perhaps the most remarkable thing about having 6 gears is how underwhelming it feels. And I mean that in a good way. It's just so intuitive. It just feels right. With the longer 5th, there's no forgetting which gear you're in because you're aware of the large gap between 4th and 5th. With a full set of 6 gears, I once again just change gear as needed, without giving it any conscious thought. When a mod makes you think the car should have left the factory that way, you know it's a good one.
Tom
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MikeMarsUK
A2OC Donor
dan_b
A2OC Donor
Argh. It's just such a costly upgrade...
If I need to get my 2nd/3rd gear synchro looked at and the clutch replaced at some point, I suppose it could be argued that the box will be broken out then anyway so why not, but....
If I need to get my 2nd/3rd gear synchro looked at and the clutch replaced at some point, I suppose it could be argued that the box will be broken out then anyway so why not, but....