Steve W2 Posted February 24, 2005 Share Posted February 24, 2005 Maybe I should stop reading that Hilliers Fundamentals of Motor Vehicle Technology book I got for Christmas!!! I agree, th point is proven by all the quotes of MPG in this thread. Where has the TT exceeded the NA on MPG? You also have to remember the gearing is different on the two cars, i would think that would have an effect too (relative RPM's etc) Quote Link to comment Share on other sites More sharing options...
China Man Posted February 24, 2005 Share Posted February 24, 2005 and air condition on or off? surely that takes some fuel as well? China Quote Link to comment Share on other sites More sharing options...
TLicense Posted February 24, 2005 Share Posted February 24, 2005 It's all down to the brake specific fuel consumption (as I've been finding out recently) This is basically a measure of how much fuel an engine takes to create 1 HP in lb/hr. (You can multiply this by 10.2 to get cc/min) How you then use that HP is down to all the other variables of an engine. (ie air con, gearing, frictional losses, drag etc) Turbo charged cars have a BSFC of 0.6-0.65 meaning it will take 0.65lb/hr of fuel to create 1 HP. Supercharged cars have a BSFC of 0.55-0.6 and NA cars have BSFC of 0.5-0.55. So basically, a turbo charged engine is less efficient than a NA. Quote Link to comment Share on other sites More sharing options...
Steve W2 Posted February 24, 2005 Share Posted February 24, 2005 It's all down to the brake specific fuel consumption (as I've been finding out recently) This is basically a measure of how much fuel an engine takes to create 1 HP in lb/hr. (You can multiply this by 10.2 to get cc/min) How you then use that HP is down to all the other variables of an engine. (ie air con, gearing, frictional losses, drag etc) Turbo charged cars have a BSFC of 0.6-0.65 meaning it will take 0.65lb/hr of fuel to create 1 HP. Supercharged cars have a BSFC of 0.55-0.6 and NA cars have BSFC of 0.5-0.55. So basically, a turbo charged engine is less efficient than a NA. Although this figure will change over the rev range, and the figure for the TT may be given as an average. it will likely be lower when not generating boost. Quote Link to comment Share on other sites More sharing options...
tbourner Posted February 25, 2005 Share Posted February 25, 2005 I agree, th point is proven by all the quotes of MPG in this thread. Where has the TT exceeded the NA on MPG? Well I average just over 20mpg around town with the odd blast up a sliproad and onto a motorway. I always reset my 'b' trip odo when I get fuel and I always put in £30 and get 286km (roughly ) on it. And I got to Nottingham and back on just over 3/4 tank all motorway - that's about 32mpg. Still 400+bhp as well!! Quote Link to comment Share on other sites More sharing options...
tango Posted March 4, 2005 Share Posted March 4, 2005 Yes, TT surely better fuel the NA, I get about 30mpg average, on motorway driving 80-90 I still get 33mpg. Quote Link to comment Share on other sites More sharing options...
250horses Posted March 5, 2005 Share Posted March 5, 2005 Roughly I'm getting 21mpg from my NA manual without any motorway driving. Improves a bit on the motorway. That's with Super Unleaded which I always find less economical than normal 95. Exactly what I got from my na TT seems to be about 1 mpg less - even if i hammer it Quote Link to comment Share on other sites More sharing options...
Soop Dogg Posted March 5, 2005 Share Posted March 5, 2005 Yes, TT surely better fuel the NA, I get about 30mpg average, on motorway driving 80-90 I still get 33mpg. Ermmm......sure you do!! http://www.mkivsupra.net/vbb/showthread.php?t=34048 Quote Link to comment Share on other sites More sharing options...
Steve W2 Posted March 7, 2005 Share Posted March 7, 2005 Yes, TT surely better fuel the NA, I get about 30mpg average, on motorway driving 80-90 I still get 33mpg. No No No No NO!!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Steve W2 Posted March 7, 2005 Share Posted March 7, 2005 Doing almost identical trips to work and back until I ran out of fuel from a full tank the mileages were as follows: 1993 GZ TT Auto = 244 Miles 1994 SZ-R Manual 5sp = 308 Miles Both cars completely stock engine wise, except for RSR exhaust on the NA. But it still has its cats in so probably no real change in consumption. The TT was running on a tank of Optimax and the NA running a tank od Sainsbury's normal unleaded. You should also note there was a significant difference in the cost of the petrol as well. Quote Link to comment Share on other sites More sharing options...
tbourner Posted March 7, 2005 Share Posted March 7, 2005 Auto vs Manual? tut tut! Only joking, I yielded after the technical answer was given in response to my gas flow reason for fuel consumption!! Quote Link to comment Share on other sites More sharing options...
CJ Posted March 7, 2005 Share Posted March 7, 2005 Yes, TT surely better fuel the NA, I get about 30mpg average, on motorway driving 80-90 I still get 33mpg. Methinks not Quote Link to comment Share on other sites More sharing options...
Guest jeb Posted March 7, 2005 Share Posted March 7, 2005 Heres how to find out your mpg!!!!!!!!!!!!!!! http://www.robinwhite.fsnet.co.uk/conv/mpg.htm?miles=215&litres=30&Submit2=Calculate Quote Link to comment Share on other sites More sharing options...
Guest Sakura Posted March 7, 2005 Share Posted March 7, 2005 Heres how to find out your mpg!!!!!!!!!!!!!!! http://www.robinwhite.fsnet.co.uk/conv/mpg.htm?miles=215&litres=30&Submit2=Calculate Damn! That means I get just 19.5mpg Must try harder Quote Link to comment Share on other sites More sharing options...
daz38 Posted March 7, 2005 Share Posted March 7, 2005 i get the same as weinelm. but its no fun unless the peddle is on the floor Quote Link to comment Share on other sites More sharing options...
250horses Posted March 7, 2005 Share Posted March 7, 2005 Damn! That means I get just 19.5mpg Must try harder 19 - 21, just what I got In my na BTW recent cold dry weather has let me boost upto 1.2 bar ....woopie.... just checked and have been gettin 16 mpg But its been fun Quote Link to comment Share on other sites More sharing options...
Steve W2 Posted March 8, 2005 Share Posted March 8, 2005 Using that calculator I got 24.3, I only entered 60 litres in as thats all it takes to fill up. My 60 litres is cheaper than yours though (if your running a TT). £6 Less per fill up Quote Link to comment Share on other sites More sharing options...
toyotasuprauk Posted March 8, 2005 Share Posted March 8, 2005 Doing almost identical trips to work and back until I ran out of fuel from a full tank the mileages were as follows: 1993 GZ TT Auto = 244 Miles 1994 SZ-R Manual 5sp = 308 Miles Both cars completely stock engine wise, except for RSR exhaust on the NA. But it still has its cats in so probably no real change in consumption. The TT was running on a tank of Optimax and the NA running a tank od Sainsbury's normal unleaded. You should also note there was a significant difference in the cost of the petrol as well. I would say the RSR makes its do a few MPG less even with the cats in. Quote Link to comment Share on other sites More sharing options...
Steve W2 Posted March 8, 2005 Share Posted March 8, 2005 I would say the RSR makes its do a few MPG less even with the cats in. Depends if the biggest restriction is the cats or baffle in the rear section of the standard exhaust. On a TT the cats are the most restrictive. Unless the design if that different for an NA. Quote Link to comment Share on other sites More sharing options...
Max Headroom Posted March 8, 2005 Share Posted March 8, 2005 I get about £50 to the week Quote Link to comment Share on other sites More sharing options...
Steve W2 Posted March 9, 2005 Share Posted March 9, 2005 I get about £50 to the week Thats very helpful not knowing what car you have, what mods you have, what petrol you using and how many miles you do a week Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 9, 2005 Share Posted March 9, 2005 A freer-flowing exhaust system should improve mpg as the engine becomes more efficient. To do the same road speed the engine wastes less power forcing the exhaust gases out. Of course, what people actually find it it boosts higher and goes faster, so it *seems* like it's less economical -Ian Quote Link to comment Share on other sites More sharing options...
stevie_b Posted March 9, 2005 Share Posted March 9, 2005 You know your stuff Ian! Do you think that applies to NA engines as well? Quote Link to comment Share on other sites More sharing options...
Digsy Posted March 9, 2005 Share Posted March 9, 2005 A freer-flowing exhaust system should improve mpg as the engine becomes more efficient. To do the same road speed the engine wastes less power forcing the exhaust gases out. Of course, what people actually find it it boosts higher and goes faster, so it *seems* like it's less economical -Ian I think the power gains would more than eat up the reduced pumping losses. The cylinder pressure change during the exhaust stroke is very low. Less than that during the induction stroke. I was trying to find a pressure versus volume curve on the web that showed this, but I can't. Quote Link to comment Share on other sites More sharing options...
Digsy Posted March 9, 2005 Share Posted March 9, 2005 I think the power gains would more than eat up the reduced pumping losses. The cylinder pressure change during the exhaust stroke is very low. Less than that during the induction stroke. I was trying to find a pressure versus volume curve on the web that showed this, but I can't. OK, scratch that. I still think the net effect would be a decrease in fuel efficiency, but I can't show it directly from the P/V curve. I did stumble across this though. Quote Link to comment Share on other sites More sharing options...
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