TDI 170 + 140 Acceleration

[jakerade]

Quick question for TDI 170 Manual owners (fwd if poss) and 140 owners if they want to comment.

I just want to check its not my imagination and I am not expecting too much of my car. Had lots of exhaust sensor problems so just want to compare with others as i have a feeling its still not right.

At a constant 20mph in 3rd gear, I put my foot flat to the floor and not a lot really happens until it creaps up to about 30mph and then it starts accelerating with a little more vigour

At a constant 30mph in 4th its the same until it hits about 40mph

Its like it bogs down with no torque.

Thanks

[frankc]

It's called turbo lag, you need the exhaust gasses to build up before you get the resulting boost from the turbo.

Usually need to get the diesel engines up to about 1800-2000 rpm for optimum boost giving the best torque for acceleration.

[jakerade]

Ive been driving the car for 33 months now and i know all about turbos! Just seems not anywhere near as fast as it used to be so checking against others

[theskyfox]

Gotta admit, does sound like good old fashioned turbo lag :P. Is the car engine hot when you do this? i.e. The engine will be noticeably more sluggy when the oil is cold. As a rough guide though, is it worth getting someone in the car with you to time your 0-60 and comparing it to the published stats? I realise theyre not gospel..but maybe it might help?

-Andrew

[jakerade]

Had DPF exhaust sensor issues (burnt out from being too hot!) so I am wondering if the DPF is restricting the exhaust gases more than before which would obviously increase the Lag. I reckon if it drove like it does now when i test drove it I wouldn't have bought it which makes me think somethings wrong still. Once its accelerating its ok (although not great), just no low down grunt. It really just does crawl forward slowly until the boost comes in.

I had a 140 TDI Multi-tronic for the last week. Bring it back, all is forgiven.

Drove an A6 177TDI last week and it was a rocketship in comparision. Touch the throttle in 3rd at 20-25mph in traffic and you would run into the back of the car in front.

[andybloke]

At 20mph in 3rd mine is only at around 1400 rpm, the acceleration isn't great in any gear with revs that low but as soon as it gets above about 2000 rpm the turbo kicks in and the car really takes off. This was the same in all the 170's I test drove before I bought mine.

[robtt09]

Even the 3.00tdi has lag.Coming out of a side road,as I do every morning, onto a main A road she takes a second or two before launch speed is reached ! Before the Audi had a Merc C Class 3.00tdi and that was the same but she fished tailed up the road with rear wheel drive when you gave her the full beans !

[jakerade]

i think thats a different type of lag - the multitronic I borrowed was awful out of junctions as you cant rev it up to get the turbo spinning and dump the clutch. Tried all sorts of methods including holding the hand brake and left foot braking! A manual is much better out of junctions.

My issue is in-gear pickup. Seemed much better this morning when it was cold compared to last night when it was hot after a long drive.

[Hammy969]

Jakerade

Is your 170 is a PD engine and not a CR?

From my experience (I previously had a 170 and 140 A3s) the 170 PD engine needed more revs to get full acceleration due the larger turbo on the 170.

My current A4 has a 143 CR engine and is considerably smoother and a wider power band and kicks in at lower revs, with no pronounced step up, the way you get with the PD engines do.

IMHO it may actually be the fact you have driven newer cars, with CR engines which may be affecting your perception of how your A4 operated prior to the problem you had with DPF problems.

Hope this helps.

Ham

[jakerade]

Hi

Its a CR170 rather than a PD.

[Hammy969]

That knocks that theory on the head!!!

[STEWY L]

Had DPF exhaust sensor issues (burnt out from being too hot!) so I am wondering if the DPF is restricting the exhaust gases more than before which would obviously increase the Lag. I reckon if it drove like it does now when i test drove it I wouldn't have bought it which makes me think somethings wrong still. Once its accelerating its ok (although not great), just no low down grunt. It really just does crawl forward slowly until the boost comes in.

I had a 140 TDI Multi-tronic for the last week. Bring it back, all is forgiven.

Drove an A6 177TDI last week and it was a rocketship in comparision. Touch the throttle in 3rd at 20-25mph in traffic and you would run into the back of the car in front.
Jakerade, from what you are reporting," exhaust sensor issues"-(burnt out by being too hot),i would tend to agree that the problem was related to exhaust restriction.
on saying that, i must tell you that i'm not "up to speed" on dpf's, their function,location, or relation/effect on catalyst, or indeed,if it has dpf, does it still have a cat?
i have a lot of experience of industrial/forklift diesel engines with "spark arrestors",fitted to the exhaust ; they are a large box with ,basically,wire mesh inside preventing sparks reaching the atmosphere, and are used widely in the "petro-chemical" industry.
these often,over time,block up and this presents it'self,usually,as "difficult starting"at first, leading to "no, or slow response to throttle, culminating ;should it not have been addressed in time,
by injectors" blowing back"" (they fail and allow combustion gasses to blow back into the fuel system and they won't run at all!!)
i'm thinking that if you have a "cat" it may be blocked,or if the dpf does the same thing,then it may be u/s, causing the exhaust sensors to burn out.
what gets me is --why a garage would change "burnt out sensors"--without rectifying the root cause of the --"burnt out sensors"???

[jakerade]

I have to agree on the blockage theory although it seems to clear itself from time to time. I drove to Ipswich (35 miles) this morning and it was the same as it has been since they brought it back on Thursday (terrible!). At least a 1-2 second delay in throttle response in 3rd gear at 40mph (2200rpm'ish). On the way back however it has gone back to pretty much normal with instant throttle response and picks up nicely in 3rd from under 20mph.

I have no idea why they are only treating the symptoms and not the cause. It seems like they dont take anything I say seriously. They had it for a week to test drive and i suspect that was only to shut me up. It goes forwards and backwards so that will be fine!

[markp306]

I tried this test with my 143 yesterday and have no real issues to share. At 20mph in 3rd, it is clearly out of the power band, but putting my foot to floor doesn't cause the car to bog down. It pulls cleanly enough and picks up smoothly and swiftly, although its not going to pin you into your seat of course. At about an indicated 26mph you can hear and feel the turbo cutting in. It then very quickly passes 30mph and so on. FYI, the car was 4-up (wife and kids on board) and I didnt really try 4th gear at 30, but often drive at 30 in 4th with no concerns. Previously I have had petrols (i.e. 1.8T) and wouldn't have expected the car to be able to do this type of driving.

Which is your local garage by the way?

[jakerade]

Thanks for checking. When mine is working it does the same. Went back to its bad old ways this morning and then perked up again for a short while.

Local garage - umm, im not sure whether i should name at this point but it was very, very near where i drove in my last post....

[STEWY L]

if you have exhaust sensors burning out, then in my humble opinion, you have something causing this,yes?
is it dpf u/s, or have you got a blocked cat?
i have no idea what so ever;---BUT I WOULD EXPECT A DEALER, OR A DECENT INDEPENDENT,charging anything between £50--£100 per hr labour should be able to tell you why it's happening ?
regards,
stewy.

[jakerade]

Thanks Stewy - its under warranty still but and its being going on since May. If they dont sort it this time then I will go else where!

[jakerade]

thread continues here...

http://www.vwaudiforum.co.uk/forum/showthread.php?122261-Intermittant-partial-power-loss-on-2.0-TDI-170