cheers, at 1800rpm i'm at 56mph in 5th, if i could get 60mph with more rolling diameter then i would be a happy man
I've got the 115bhp version of the 2.5 I5 TDI (AAT engine in the non quattro A6). Does about 45mpg average when commuting which is about 17miles of motorway mentalness and 7 miles on urban crawling twice daily. Not idea conditions for economy. Could probably get 50mpg if I stuck to lane 1 and kept the speed down on the motorway, but that would mean being late for work more often. When taken on a lazy A-road tour the consumption improves to about 50+ mpg though I don't really trust the MFA that much. Tried some additives a while back and didn't seem to do much. Tempted to try ECU/Injectors trick to up the output to 140 and see what it does to economy.
Is yours 5 speed or 6 speed as think that makes a difference Mines a 6 speed I keep looking at newer cars but none of the new 2.5 are any good on mpg , be lucky to see 40 mpg So sticking with mine as long as possible I used to have a new a3 tdi , but that only last until 123k and the turbo went I also use mine as a company car and the rates they pay for 2.5 derv is much better than 2.0 so gain a fair amount
It's only a 5, would like a 6 for the motorway dash (though I've heard a rumour that the 6 speed boxes aren't as durable) as I think the longer ratio would curb my tenancy to change speed. I've also got the stalks for a cruise-control retrofit, though have yet to fit it. I may end up having to use mine for work if I continue to cause our fleet manager headaches..
What are the obvious diesel-specific things to check to ensure your MPG is as good as it can be. Obviously, tyre pressures, tracking, binding brakes, fuel leaks, driving style, etc are the same with any car. - Pump timing - Cam timing - Thermostat / running at the right temp. - Head gummed up with tar - Boost leaks? What else?
Check and clean inlet manifold, intercooler, turbo. Remove or beat out soot filter (not dpf!) and remove as many restrictions in and out of the engine as possible. Engines are a giant pump and only as good as the amount of air they can shift in and out as possible.
Reckon you can ditch the cat if it's got one. Another thing to add to your list Mike would be checking the injectors - opening pressure and spray pattern. VAG com can give an idea of injector opening times I think..
Not on the new mot regs you can't, beat the middle out yes but it still needs to be seen to have a 'cat' if one was fitted from factory
^^ That's exactly what I'm planning. It was nowhere near the limit on the emissions test at the weekend.
Cars pre 2001 with a diesel soot filter often mistaken as a cat (it looks the same) are only visually checked to make sure they are fitted if oem, and have to pass a visual smoke test. The soot filter does what it says on the ton, it filters out the soot by collecting it up on warm up, slowly blocking up, forcing it to get very hot, when it reaches a certain temp the metal reacts with the heat and breaks down the soot into smaller particules and remains at this constant temp range until shut down. It does not do anything to the nox emmisions etc. A DPF does both and can't be removed atall, and is tested by the assessor. Most Mot stations I have used don't even notice or care that the filter is removed in my experience. However, even an emptied filter does not flow as well as a straight through pipe, I have welded a pipe of the correct diameter inside my cat, so the flow is uninterrupted and continuous down the whole exhaust system, while retaining the oem look.
Don't get me wrong, it's a pig to do, and you have to use a dremel or somthing like that to grind back the flange welds, but once done it looks great, and the filter case could be painted to look like stainless steel if you have a full system as its now insulated and not getting as hot. Flow is much improved and turbo onset and response is hugely improved once the soot up stream from the newly free'd up system is blow through
Accelerometer showed a 2bhp gain consistently, which, accurate or not, it's still an improvement, regardless of the figure.
That only applies to vehicles that are subjected to a full cat test - I looked into this on hearing about the change in regs, and my own cat-removal treatment earlier this year. See this thread/post
Ah cool, even better. 2.5 system is ideal, much bigger and the exhaust velocity slows down. It's true that diesels don't need back pressure (no scavenging) but they do need a small amount to maintain turbo seal integrity.
It is a catalyst not a soot filter.... The catalysed reactions do reduce soot levels a bit though. DPF does nothing for NOx, a dpf is a soot filter. Cars with DPF's also have diesel oxidation catalysts fitted which help on CO and Hydrocarbon emissions.
