JohnA Posted July 4, 2005 Author Share Posted July 4, 2005 Sod the fuel consumption..... I don't think you understood my point. Anyway... dont forget a supra is a high performance engine with 2 turbos its not really built for economy........ It's a 3litre engine that uses boost to think it's 4 or 5 litres big. It's only 6 cylinders, and designed well enough to be efficient for the horsepower. Off-boost it doesn't do more than a few dozen horsepower anyway, so the only 'impediment' for decent mpg is the weight and wide tyres 200miles from this tank during mild cruising is unacceptable. This is not an 8 or 12-cylinder 7litre twin turbo, that would be expected to do high tens even off-boost, with all those cylinders to fill, and all those surfaces to cool. I very much doubt that this consumption is normal for a Supra, just because so many people have come to accept it. Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted July 4, 2005 Share Posted July 4, 2005 I don't think you understood my point. Anyway... I do I just cant see the point worrying about it, you a buy a supra for performance and not for economy It's a 3litre engine that uses boost to think it's 4 or 5 litres big. It's only 6 cylinders, and designed well enough to be efficient for the horsepower. Off-boost it doesn't do more than a few dozen horsepower anyway, so the only 'impediment' for decent mpg is the weight and wide tyres 200miles from this tank during mild cruising is unacceptable. This is not an 8 or 12-cylinder 7litre twin turbo, that would be expected to do high tens even off-boost, with all those cylinders to fill, and all those surfaces to cool. I very much doubt that this consumption is normal for a Supra, just because so many people have come to accept it. Again its a sport car so consumption will not be good, name me one sports car woth good consumption......+ ive just seen your car is BPU which is going to use miles more fuel than stock anyway. cars tend to use more fuel when they age as well....there are a whole host of factors you need to take into consideration mate Quote Link to comment Share on other sites More sharing options...
Alex Posted July 4, 2005 Share Posted July 4, 2005 Off boost the TT engine has to work harder than an NA cause it's low compression. So you have to give it more gas to keep it at speed. I thought at 1bar it was acting like an engine of double the capacity? Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted July 4, 2005 Share Posted July 4, 2005 Agreed Alex, If you want speed it comes at a price........more hand in the pocket action when it comes to buying fuel Quote Link to comment Share on other sites More sharing options...
The Hornet Posted July 4, 2005 Share Posted July 4, 2005 Agreed Alex, Me friend did a calculation for me and said at 1.2 bar its equivalent to over 7 litres or something. Dont ask me how I didnt work it out. Mine seems to be running fine. I do a 36 mile round trip to work each day on country B roads which are never busy with traffic. If i take it easy for the whole tank I get around 240-250 miles per tank. If I drive as I normally do i get around - 200-210 per tank, but I have had it as low as 180 miles on one tank Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted July 4, 2005 Share Posted July 4, 2005 If you think thats bad dont ever go to the Ring, I get 5 laps to a tankful! and some others on here maybe even get less! ? With a Supra your better not to work out the mpg, just drive and enjoy. I once managed 220 miles on £64 of BP ultimate, I was well pleased :-) Quote Link to comment Share on other sites More sharing options...
The Hornet Posted July 4, 2005 Share Posted July 4, 2005 I see I'm not the only one to drive on the slightly quicker side thought there was something wrong with me racing around everywhere, all the time. (Safely mind you ) Quote Link to comment Share on other sites More sharing options...
Tannhauser Posted July 4, 2005 Share Posted July 4, 2005 Economy is always an issue in my book. It reflects fuel efficiency, proper combustion, which is a GOOD thing. An engine running rich for no good reason fills itself up with carbon deposits and loses efficiency fast. Even the valve clearances vary with such deposits, you could end up with burnt valves when a clean engine might have got away with it. A quick recap of why John is interested in his mpg, for some who appear to have missed it. It's not just a question of resenting paying for the petrol. Cliff Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 4, 2005 Author Share Posted July 4, 2005 A quick recap of why John is interested in his mpg... Yeah, it's like nobody wants to see the real issue, but are blinded by an urge to show off their willingness to pay for 'power', as opposed to the tight pikey whingeing over a few pence... Yeah, thanks for the info, at 1 bar the engine is the equivalent of 6 litres, and at 2bar 9iltres (hello, that's whole blody point of turbocharging! ) But that's at full throttle mate, not poodling around town or lazily going down an empty motorway at a steady 80mph. The throttle is almost shut then, and the engine is running closed loop, ie AFR 14.7. There is only so much fuel a 3litre engine can use up efficiently in such conditions, it's not a sign of virility to use up TWICE that. It's a sign of bad adjustment, and the situation will snowball eventually as the extra fuel has to go somewhere. Some of it will cover the combustion chambers (setting the stage for pre-ignition), some will stick under the valves (increasing pumping loses), some in the exhaust ports (making them smaller), some on the oxygen sensor (poisoning it), the inside of the EGCV (check the replacement cost first), etc etc. Not all excess fuel will go straight into the atmosphere. So don't mix up fuel consumption under full boost with that on idle or low throttle. They are two different worlds. Quote Link to comment Share on other sites More sharing options...
b_have Posted July 4, 2005 Share Posted July 4, 2005 I went to Cornwall last week, did almost 200 miles at less than 90mph, pretty much off boost (nervous gf) on half a tank. At Siverstone track day, I got less than 2 miles/ltre! Have to say, Im happy to get under 10mpg IF the afr's are good at this consumption, means lots of ponys! My afr's are reasonable at both ends of the scale here. getting > 25mpg @ off boost cruising and Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 4, 2005 Author Share Posted July 4, 2005 ...Would LOVE to get to 6mpg at 12:1 afr! yeah, but that doesn't tell the whole story does it? If you're talking of full-throttle operation with a single and high boost, then we're looking at a substantial Volumetric Efficiency, and at AFR 12:1 that would be quite a lot of fuel (to compliment all that air!) What I was talking about was off/low-boost lazy driving/idling on stock twins. VE is very low at those conditions, and the ideal AFR for them is 14.7. The fuel to compliment that tiny amount of air should be just a trickle. AFRs on their own don't tell much, do they? (thought you had me there Charlie eh?) Quote Link to comment Share on other sites More sharing options...
Alpine Posted July 4, 2005 Share Posted July 4, 2005 yeah, but that doesn't tell the whole story does it? If you're talking of full-throttle operation with a single and high boost, then we're looking at a substantial Volumetric Efficiency, and at AFR 12:1 that would be quite a lot of fuel (to compliment all that air!) What I was talking about was off/low-boost lazy driving/idling on stock twins. VE is very low at those conditions, and the ideal AFR for them is 14.7. The fuel to compliment that tiny amount of air should be just a trickle. AFRs on their own don't tell much, do they? (thought you had me there Charlie eh?) YOU WHAT? I thought this was an inglish speaking foreum? Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 4, 2005 Author Share Posted July 4, 2005 http://www.max-boost.co.uk/stuff/word_yo.jpg Quote Link to comment Share on other sites More sharing options...
b_have Posted July 4, 2005 Share Posted July 4, 2005 yeah, but that doesn't tell the whole story does it? If you're talking of full-throttle operation with a single and high boost, then we're looking at a substantial Volumetric Efficiency, and at AFR 12:1 that would be quite a lot of fuel (to compliment all that air!) What I was talking about was off/low-boost lazy driving/idling on stock twins. VE is very low at those conditions, and the ideal AFR for them is 14.7. The fuel to compliment that tiny amount of air should be just a trickle. AFRs on their own don't tell much, do they? (thought you had me there Charlie eh?) Yeah but...... Oh bollox, too tired to argue. and goodnight! Oh, BTW many thanks for the wheels John, love em to bits! Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 5, 2005 Author Share Posted July 5, 2005 Bling bling Quote Link to comment Share on other sites More sharing options...
supRo Posted July 11, 2005 Share Posted July 11, 2005 I just thought I'd report on my o2 sensor change and AFR adjustment. I'm no tecchie so please excuse the lack of details, understanding or figures!! I have been getting very poor fuel economy (BPU Jap TT) - Similar to what John has been getting. I changed the o2 sensor for a new one. The first thing I noticed was that the car was running much smoother and seemed a little faster!! I haven't had a chance to run it much before checking the AFR yesterday at Thor so I can't make a direct comparison from the old o2 sensor to the new one. The car was running a little rich. I have had the AFR's checked/adjusted on a previous occassion with the old o2 sensor but the fuel economy was always pants. Anyway - Driving from Thor to home - it was much more economical on the fuel! I drove like my nan yesterday from Farnborough to Portsmouth and back and ending in Luton.... I manage to get just under 160 miles from half a tank of petrol!!!!!!! My fuel economy has never been this good!! Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 11, 2005 Author Share Posted July 11, 2005 well as I said on another thread, despite the (likely) old age of my oxygen sensor, the car idles an runs off-boost in ideal mixtures, so in my case the sensor doesn't appear to be a factor. I've got a new one going in though, so we'll see if it still makes a difference. Quote Link to comment Share on other sites More sharing options...
Winston Wolf Posted July 11, 2005 Share Posted July 11, 2005 Really intersesting thread guys but have we got an abbreviations refrence somewhere?I am struggling to follow all the points being voiced here!! Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 11, 2005 Author Share Posted July 11, 2005 There's one in the FAQ mate Quote Link to comment Share on other sites More sharing options...
penguin Posted July 11, 2005 Share Posted July 11, 2005 Bit weird... but i changed my plugs for the ngk coppers, gapped to 0.8mm... and fitted a boost gauge.... made sure i didnt hit boost and for 26 litres of optimax... i got an ASTONISHING 28.8 MPG... ALL local driving..... thats the BEST i've ever had.... she was running very rich before, and the best i got was 17mpg on a very long drive to leeds with very little boost.... Quote Link to comment Share on other sites More sharing options...
Bobbeh Posted July 11, 2005 Share Posted July 11, 2005 Its those damn thirsty autos Manuals allow much nicer MPG if you're an angel John does it smell like its overfuelling? Check the plugs and the back end for smoke. Quote Link to comment Share on other sites More sharing options...
penguin Posted July 11, 2005 Share Posted July 11, 2005 guys, is it hard to change the o2 sensor?? and prices/part numbers would be nice too Quote Link to comment Share on other sites More sharing options...
JohnA Posted July 11, 2005 Author Share Posted July 11, 2005 Its those damn thirsty autos well yes, the auto transmission eats up more power, that's no secret. I'm trying to like it but I can't help longing for a 'proper' 6sp The only advantage I find is in start/stop traffic, the auto is much better. John does it smell like its overfuelling? Check the plugs and the back end for smoke. Mine? Naaaah... It's spot on 14.7 mate. Quote Link to comment Share on other sites More sharing options...
Bobbeh Posted July 11, 2005 Share Posted July 11, 2005 The only advantage I find is in start/stop traffic, the auto is much better. Couldnt agree more, traffic is a bitch Quote Link to comment Share on other sites More sharing options...
Homer Posted July 11, 2005 Share Posted July 11, 2005 Hope this isn't a hijack, but... I just found out my odo is running in km not miles, this means I'm getting around 14 mpg lately From what I've seen in this thread it looks like I may have a problem with the o2 sensor being faulty or fouled up. (It was running with a very high fuel pressure for a couple of months and seriously sooted up my old ik24 plugs) Is it possible (or even sensible) to try cleaning the o2 sensor before going for a replacement? Also is the o2 sensor the probe mounted in the exhaust manifold just before the first cat pipe? Quote Link to comment Share on other sites More sharing options...
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