round town mpg on derv?

[optimusprimer]

what are the derv folk getting for round town mpg? Last week I had a mix of town and motorway driving and managed 45mpg (wasn't being overly gentle on the right peddle). This week I put in the same tenner's worth in and seem to only getting about 22mpg round town only.

I do short journeys with low revs, not much turbo action. The car is running SDI injectors, 19psi boost, decat and filter, is it this combo that could be reducing the mpg round town? Do the SDI injectors have much effect on the economy?

whilst the extra power is alot of fun I am toying with the idea of returning it to stock. What should I be getting round town as stock?

The reason I got a derv was for the economy aspect, the figure I'm seeing at the mo arent much better than I was getting out of my BMW 525 petrol.

OR is the low mpg pointing to something having gone boobs up?

[peterzs]

Does it throw out a bit of smoke if you boot it???

The SDi's will push more fuel in than the o/e injectors, thats where they give you the extra power. But at a cost to the mpg.

I had my one remapped, but still a bit of smoke.

Was getting 55+ mpg on mixed driving, but down to 45+ I reckon now, must admit not checked it.

Can you red line it, if you boot it and does it pull through all the gears. The MAF sensor can go and this will stop it revving freely. Makes it feel flat.

22 mpg seems low, I have a few fill up, receipts with miles on, in the car, just been a bit worried to work the mpg out! I'll go and get them and see what they say!!!!

:beer::beer:

[optimusprimer]

MAF is fine, it flies when you give it some stick and happily red lines. Very little smoke when you give it large too.

admittedly I have taken the reading from fuel light >£10> fuel light so not really the most scientific! I'll have to bite the bullet and brim to brim test it to get a better idea :D

[peterzs]

Just looked at my fuel slips, didnt fill it to the brim, just when the first stop on the pump.

Looks like my first one which included a bit of running with the new Sdi's and when he did the remap, I got 45.63 mpg.

After the remap and the new SDi's 38 mpg. thats over 545 miles. Mix of motorway and round town driving 2/3 motorway roughly.

What I thought, just a matter of deciding if the extra whoooomph and the 234 ft lbs torque, plus grin are worth it.

Yeah!!!!!!!!!!!! its worth it!!!!!!!!!!!

:beer::beer:

[zsserbia]

22 mpg is really bad, but the way you got to this result isn't reliable at all. Just going fast through corners could move the gauge up to 1/4 tank!

My derv is std and in worst traffic (stop and go, not more than 15 mph average) it still returns 33 mpg.

[optimusprimer]

I fully agree the method I used to gauge the mpg was rubbish! I notice when I drive quickly the fuel needle can go from quarter to red so I have taken the readings with a pinch of salt ;)

But after realising that 95% of my driving is round town I need it to be as good as it can be so the SDI injectors have been removed and the boost reduced to 17psi (I did have a moment where I adjusted the boost the wrong way and ended up with 23psi, that was a fun test drive!)

I will monitor the results and see what the difference is, if it is a marked improvement the injectors will get sold on I guess.:hmmm:

Sadly it now drives like an old woman rather than a young teenager :thumbsdown:

[peterzs]

Just filled my one up again, the figs are coming out at 43.24 mpg.

I do tend to boot it around, so all in all, considering the performance I'm happy with it.

Could drive at 55 mph on the motorways I suppose, but sooooooooo boring. Just have to keep the speed down a bit.

Have to do a proper mpg test on yours to see what you are getting now.

:rambo::rambo:

[C13URD]

Just filled my one up again, the figs are coming out at 43.24 mpg.

I do tend to boot it around, so all in all, considering the performance I'm happy with it.

Could drive at 55 mph on the motorways I suppose, but sooooooooo boring. Just have to keep the speed down a bit.

Have to do a proper mpg test on yours to see what you are getting now.

:rambo::rambo:

Peter i run the Derv for just over two weeks had quarter of a tank left filled it up with £56 to the brim worked out the mpg & to be honest was well gutted......... only got 40mpg not good at all..

been speaking to Matt Reidy about a map..
still in two minds at the mo i want it nippy but also want it frugal when required..the derv i used to have was mapped to 140bhp & used to return 45mpg no matter how hard i drove it got me thinkin perhaps these SDI's are not all that good if you want any sort of economy out of your diesel....what to do.

thinking of putting the standard injectors back in & having it mapped..
cant decide..

what do you think Peter.. help..

[peterzs]

Hi Clive, what I found was that after:- decat, boost up a bit, MAF box, BMC panel filter, dodgy remap, where they sent the ecu away, Powerflow s/s exhaust cat back, I was getting 212 ft/lbs and 134 bhp, and 48 odd mpg.

Now SDi's and a Reidy remap, 234 ft/lbs and 159 bhp, still has black smoke and my last check was 43.24 mpg.

Tempted to get my o/e injectors refurbed, guy on ebay quoted £94 all in incl postage, and bung them back in.

Black bits over my boot annoy me, but I love the extra umpppppph when it gets over 1500 revs, driving like ZSSerbia said, get through gears 1 and 2 and push it from 3 onwards!!

Depends on your mileage Clive, more power = less mpg, less power = more mpg.

This is why I didnt get a V6 wasnt looking for power just good mpg, but...............

Least I havent got Dan pushing the limits and the bhp, any more.:yes::yes:

:laugh::laugh::laugh:

[optimusprimer]

Well this weeks less than scientific test, done to the same ropey standards as before has seen a return of 38.42mpg round town after the SDI injectors have been removed and boost turned down.

Thats a bit better!

[zsserbia]

Now that's more like it! Still, is it possible that SDI-s were a bit dodgy? Good think there was a cheap solution to it :box:

[Enright]

To OptimusPrimer:
My setup isn’t much different to yours.
The previous owner fitted a decat pipe (however I’ll be replacing this with a nice pretty (but probably empty) cat before my next MoT),
Standard exhaust with a Powerflow backbox,
SDi’s,
Conical air filter,
Boost set to 19psi max.
I’ve not had a remap.

Depending on how brave I am with “fuel-light roulette”, I can get up to £74 in at £1.37 per litre, which works out at 11.88gallons.
From that I usually manage between 460 and 500 miles, or 38.7 to 42.1mpg, although on occasion I’ve achieved 525 which is 44.2mpg (mind you, I’m not sure the stress was worth it)!
My commute is 22 miles each way per day, about half urban and half motorway. On the motorway I aim to maintain 80.
I’ve found on a couple of previous ZR TD’s that SDi’s usually cost you about 3mpg overall.
From figures available for Mk2 ZS TD’s on AutoTrader, the official numbers are as follows: Urban 36.2mpg, Extra Urban 65.7mpg, Combined 50.5mpg.
I don’t think I’ve ever seen as low as the lowest number, but then the other 2 just seem to be fantasy if you want to enjoy your driving at all.
I’m pretty sure that turning down your boost won’t help your economy as it makes no difference to the amount of fuel injected – the more air you get in there, the cleaner the burn will be, so conversely turning boost down just means you’ll get more un-burnt fuel (in the form of smoke) out the back.
As proof: you’ll usually see TD’s smoking the worst as the driver puts their foot down before the turbo spools up. Once they start to breathe properly they’re pretty clean.

As for “biting the bullet” about brimming it, what’s the logic? You’re going to use the fuel anyway, and there’s precious little difference between lugging it around for slightly longer as there is running backwards and forwards making 7 times as many trips to the petrol station. If anything you’re probably better off putting it in sooner rather than later as fuel prices almost always go up, so the earlier you buy in bulk, the cheaper you get it. Factor in time spent and wastage resulting from splashes, along with the ability to make a far more accurate average fuel consumption calculation, and it ought to be a no-brainer.

[C13URD]

Well after brimming mine again today & working out the mpg the SDi's are coming out on Monday & will be for sale....

[Enright]

Did you get 40 again? If it's not already had a remap, having one done might rein in the fuel that's going through them a bit and up your economy, so giving you the best of both worlds.

[optimusprimer]

As for “biting the bullet” about brimming it, what’s the logic? .

I can't afford to spend £70 in one go, simple as that