Question For The Car Gods

[The enchanted broomstick]

Evening to all, i have a 406 sri turbo as some of you may of seen on here. Anyways i've noticed how crap my fuel consumption is and was wondering about getting a boost controller. Im thinking if i can turn the boost pressure to 1psi or 0psi then im going to save loads of fuel for when i feel like driving normally. Will this cause any problems though....? After putting my car above 11 - 12psi of boost i get turbo cut and havent tested it at the bottom end of the scale yet.

As always any help appreciated, Stu

[TomR]

Drive more carefully, at what revs does the turbo kick in? just stick below that when you can.

[MadChikken]

Have a slightly less concrete right foot might help ur fuel consumption....lol

Usually the cause of high fuel burning, and as above, just change gear earlier and keep the revs low enough so the turbo isnt spooling right up!

[djb]

Though the theory is sound, assuming your car is set up correctly for high boost, turning down the boost will simply result in massive overfuelling for the low boost situation and not change your mpg that much.

I may be wrong as all tuned engines are made to work differently and i'm not so hot on turbo set-ups but from what i've read/heard from mates about turbo'd cars the fuelling should be set up for specific boost, reduce the boost and the performance all goes pear shaped and unless you remap your ecu the fuelling will stay at the high boost level which could lead to other problems. Don't quote me on this, but I think i'm in the right ball park.

Edited December 4, 2006 by djb

[Heatsink]

Isn't how you drive going to have the biggest effect?

An IC engine is typically it's most economic around 50 mph, or was it 60mph? If you're motorway driving at a reasonable speed then you'll get the most out of your tank. Loads of short journies around town, and high speed driving will use up that expensive fuel the quickest.

Steve

[CurtisRider]

Isn't how you drive going to have the biggest effect?

An IC engine is typically it's most economic around 50 mph, or was it 60mph? If you're motorway driving at a reasonable speed then you'll get the most out of your tank. Loads of short journies around town, and high speed driving will use up that expensive fuel the quickest.

Steve

yuppity, short journeys suck up the most fuel per mile, so advoiding them (as hard as it is) is a good way to save fuel. ive found with my car, obviously if i drive with my pedal right down to the floor, it sucks up more juice, but just taking it to 3/4 of the way, saves BIG style amounts of fuel and it doesnt really make the car accelerate much slower. also learning to know when to take your foot off for corners, so you have to brake less/not at all helps alot, tis also kinda fun on the roads i live on another 1 is too knock the car out of gear and let it roll, ok they tell you not to do that in your test, but on a nicely rolly bit of road i manage to knock my car out of gear at 60 and go on for a good mile.... every little helps

also advoiding the turbo....in my car thats near impossible, it engages nearly immediately, and im guessing as your cars upgraded to go speedy, then you will find it hard to advoid it wihtout changing at 1000rpm or something

[manuel]

also - feathering the throttle when on those town journeys is also bad - as an engine is most efficient under load - so about 2/3 - 3/4 is best i believe ....

and if you are that worried about fuel consumption why did you get a turbo'd car ?

just rag the shit out of it all the time and dont worry about it.

[Prawny Baby]

Im thinking if i can turn the boost pressure to 1psi or 0psi then im going to save loads of fuel for when i feel like driving normally. Will this cause any problems though....? After putting my car above 11 - 12psi of boost i get turbo cut and havent tested it at the bottom end of the scale yet.

sadly, i dont think this is going to work at all....

being a turbo engine, it will be low compression, so fuel effiecieny will be FAR worse than the n/a version of you rengine if you were to run no boost. also, with a boost controller fully closed you will still run standard boost i think, which i guess will be 6-8psi.

also, being low compression, if you were able to 'turn off' the turbo, it would be SERIOUSLY slow, as the compression is so low to allow it to run the turbo effectively.

just drive more sensibly, it CAN be done i assure you....

in my A3 turbo i get around 20mpg around town, and 30ish on a run driving NORMALLY (not quickly)

yet on a good long motorway journey, if im acreful to keep the air con off, and stick below 95, i can return 45mpg, as i did over a 300 mile journey from northampton to cornwall.

also, no matter HOW hard you try to drive economically, you can do better....

i drove to frome in somerset to see Si the physio, and i managed to make 36mpg on the journey, which i thought was awesome considering it was the whole way up the windy coast road!

my mum drove back, normally, in the same time i did, and somehow got 38mpg

its literally about driving slowly and sensibly..... no matter how hard i try, i just cant drive as economically as my mum, im just too used to going faster.

[Smo™]

2nd at 20mph, 3rd at 30mph etc.

It's your best bet really mate.

[Prawny Baby]

2nd at 20mph, 3rd at 30mph etc.

2nd at 20? common sam, thats not driving sensibly!

when im in an economical mood, i hit second by 5mph and 3rd by 20 at the latest........

a big engined turbo like that sri should pull nicely in 4th from around 30mph, and 40-45 in 5th.

around town im always always just ticking over in 4th!

you need to self impose a rev limit i reckon, and also, dont allow your right foot to hit the floor at all unless your slowing down!

conciously make sure you dont ever reach what, and try and impose a 3000rpm rev limit.

it seems to work for me.

[Luke Williams!]

when i hit 30 am in 4th then put it into 5th, cruising baby

Also diesel power.

on 5th gear they had a test with the vauxhall astra VRX and its equivalent in diesel. they found that the diesel was only half a second slower than the petrol and actually recommended the diesel over the petrol because of fuel consumption etc.

Edited December 4, 2006 by LukeBrisaRider

[george_seamons]

another 1 is too knock the car out of gear and let it roll, ok they tell you not to do that in your test, but on a nicely rolly bit of road i manage to knock my car out of gear at 60 and go on for a good mile.... every little helps

On modern cars, that actually does more harm than good, especially on diesels.

Letting the car idle, by either dipping the clutch, or slipping it into netural, means the engine has to run off its own resources. Think about it, when the cars moving, its essentially driving itself. The wheels are turning because the car is moving, thus driving the crankshaft, and pistons, and the whole process is kind of powering itself.

Most modern cars' ECUs will actually partially cut off the fuel to the enigne if it doesn't need it all, so by coasting, you're forcing the engine to run all the fuel to keep the engine running itself, because there's nothing moving it.

...not to mention you have very little control over the speed of the car when you coast. You have no engine braking, which in an emerency, could mean the few extra metres between her and a cabbage-patch-kid.

[JTM]

^^^Basically you should roll up to lights in gear until the car is about to stall, then dip the clutch

[dave85]

You should roll upto the lights double de-clutching down the box for the sheer f**king hell of it

[TomR]

Yeah as said, most modern cars have some kind of fuel shutoff, as while coasting it can cut the fuel and the momentum will keep it rolling and it'll still be easy enough to start injecting fuel again.

Also coasting is technically illegal, so add that to using more fuel whilst out of gear i wouldn't really bother:p

[The enchanted broomstick]

I know the fuel is mainly because i spank it but i do actually drive sensibly, there is always a time and place for opening a car up and rural 30mph zones is certainly not the place for it.

The turbo cuts in at just under 2,000 revs and idling at 1,000 means i have you guessed it 1,000 revs to play with through change of gear. Even if i accelerate proper slow and the car is warm at 1,800 revs the dump valve will still make noise.

2nd at 20mph, 3rd at 30mph etc.

It's your best bet really mate.

Christ! im normally just about rolling by the time i get into 2nd gear on a casual pullaway. 3rd gear about 18mph 5th gear by 30mph

[Smo™]

2nd at 20? common sam, thats not driving sensibly!

I can never help myself

[Simon]

I get to 2nd at 10mph, 3rd at 20mph i think.

Now you mention it, i can't remember actually haha.

Although my car is a 1.4.

[The enchanted broomstick]

Anyyyyyways, back to the subject. Im not really going to be able to do what i was hoping.

I guess the other option i have is putting a mahoosive 92mm turbo on there and modifiying the bulk head to take it, that way it would wind up about 3,500 revs instead

[Smo™]

So long as you uprate your internals, otherwise if you give it some welly it'll pop pretty soon.

[Waynio]

an electronic boost controller would help, i havent got one, and really do need on. @ the going rate of this:

in 2 weeks i have gone through £200.00 worth of Optimax fuel 14 days and £200.00.

if you turn the boost down or off, it does save on fuel consumption, feather has one on his van, 4 position, usually his is set on 85% LOL!!!! so he has it on full boost MOST of time.

if you have got £220.00 to spare and maybe some labour for someone to fit (unless you can do it) go for it. i will do mine early next year (possibly) fund dependant

Waynio..........................