View Full Version : Explanation of judder after chipping
I got this info from here:
http://forums.tdiclub.com/NonCGI/ultimatebb.php?ubb=get_topic;f=4;t=004119;p=1
The title of the thread is "Upsolute = 1800 WOT shudder?"
The copied explanation is:
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The judder at WOT in the rev range below 2200 rpm with a chipped car, has nothing to do with the clutch!
It is because of the 2-mass flywheel which has to cope with more torque as it was designed for. If the torque is getting to high at low revs itīs starting to produce vibrations instead of dampening them. A good chip doesnīt increase the torque that much in this region, so you donīt have the judder! (isnīt very good for the 2-mass flywheel either)
You can have about 235 lb/ft max. torque up to 2200 rpm without having judder problems. (it differs slightly from car to car) I personally prefer to have a car with a torque of about 225 lb/ft between 1800 rpm and 3000 rpm, rather than a car with a peak torque of about 250 lb/ft at 1900 rpm and than quickly dropping.
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So it would appear the problem is too much torque through the dual mass flywheel. Makes sense to me.
But doesnt the standard chip produce close to 225lb/ft ?, if so, it would seem like its not worth chipping diesels?, or can much be added above 3krpm?
Mosser, the standard Leon produces 173/lb/ft.
I got that from http://www.seatcars.net/leonspec.shtm
The problem would go away with a weaker chip.
Or upgrade the clutch and flywheel.
To be honest I'm struggling to understand how it can be the flywheel.
Clutch judder I can understand....but the flywheel oscillating????
These are dual mass flywheels.
A description of them is at:
http://www.standardtransmission.com/dmf.html
They do judder with a full load, in a chipped car, up hill, at peak torque with turbo spooled up. They are designed to do it to protect the transmission.
The copied explanation of what they do is:
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It is designed to isolate torsional crankshaft spikes created by diesel engines with high compression ratios. By separating the mass of the flywheel between the diesel engines and the transmission, torsional spikes can be isolated, eliminating potential damage to the transmission gear teeth.
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Also:
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DMF is designed to protect the transmission. It is also designed as a wear component and will fail if O.E.M. vehicle capacity is ignored.
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To see a very nice picture of a dual mass flywheel have a look at (about halfway down the page):
http://forums.tdiclub.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4&t=003953&p=2
More pictures at
http://forums.tdiclub.com/NonCGI/Forum27/HTML/000025.html
Didnt know they were that low on torque as standard!, must make a big difference to the driveability if you take the chip out again,
Has anyone told upsolute of these findings?, cos they should be able to produce a chip with less then 225lb/ft below 3krpm within a week i would have thought
Thanks Langers.....they do say you learn something new every day, and this was "it" for me.
Had no idea it wasn't solid.....and now the comments make sense.
Mosser - PD engines have upto 235lbs.ft as std......which you get in the Cupra150TDI only :(
And yes - I've seen Upsolute talking about "alternative" maps with less of a low rpm boost. Since diesels tail away from low revs anyway, I'd be far more interested in "flattening" the delivery as much as poss.....so a remap from 110bhp/173lbs.ft to 145bhp/200lbs.ft would suit me as well as the "std" remap which (in theory) peaks at 215lbs.ft.
This theory also suggests that it's not really the fault of the map....any upgrade which provides lots of torque at this engine speed will send the flywheel into harmonic oscillation......although in saying that....not everyone that remaps gets this vibration...... :confused:
Just a point of torques of the TDi's, the 6 speeed versions can handle more torque, and thus PD models with the 6 speed box have more torque, see below.
TDi 110 5sp - 173lb/ft
TDi 115 PD 5sp - 210lb/ft
TDi 115 PD 6sp - 229lb/ft
TDi 130 PD 5sp - 210lb/ft
TDi 130 PD 6sp - 229lb/ft
TDi 150 PD 6sp - 235lb/ft
In answer to a previous question, YES, putting the original chip back in feels horrid, like getting back in a small engined car. Going by the power figures mine is producing over 235lb/ft chipped, and it is nice to drive, the power is more petrol like with a strong pull at 1650rpm which gets gradually stronger until about 4500, then a very slight decline to 5000 (as standard it would give up at 4300, and hitting the 4750 red line was not worth it)
I've had a slightly reduced power chip put in, and although it has reduced the shudder, it feels at least as powerful after 2500rpm as the old one, if not better........shall report back after some more work has been done.
Impossible
19-02-2002, 20:23
hmm... the UPsolute 110 TDI chip is suppoesed to give 214Ft lbs torque and 143Bhp (these are guarnteed figures) so you may get a little more. But with Neils car we got about 156bhp i would need data logs below 2200rpm to find out what the torque figures are like,
Not sure on the PD figures has the car produces 230 ft lbs standard, Upsolute take it to 313ft lbs!!! The 150Pd rally car in Germany produces about 350-375 ft lbs Torque.
Mic