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Kozy
Original Poster
2,014 posts
87 months
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Nerdy friday afternoon thread, and a spot of PH top trumps!
Everyone is familiar with specific power, i.e. the Ferrari 458 is the current top dog with 127bhp/litre. What you may not be so familiar with is the fact that this is an easily cheated figure, you simply rev the piss out of an engine and voila, you've got motorbike engines producing 140bhp/litre. Impressive no doubt, but not really a useful comparison.
What is not so easy to cheat is specific torque, most naturally aspirated engines will top out at around 75-80lbft/litre. The aforementioned 458 again tops this chart with I believe 88.5lbft/litre. It is certainly possible to get more, but it's in the realms of serious engine tuning...
What interests me is the specific torque of turbocharged cars, and how closely linked it is to boost pressure. My thinking here is that 1 bar of boost is effectively 200% VE, or double the engine size, so the specific torque of a turbocharged engines effective capacity should still be around 75lbft a litre.
I'm interested to hear what the vast array of cars on PH put out in this respect, wether they be NASP, forced inudction or heavily modified.
I'll start off with two of mine
1600cc 118lbft = 73.8lbft/litre
2200cc 159lbft = 72.3lbft/litre
Both Honda engines, renowned for being good on specific power but are also pretty good in terms of specific torque.
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Marf
22,907 posts
110 months
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Last time my MR2 was on the dyno, 265lb/ft so 132lb/ft per litre without factoring in your 200% VE
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Kozy
Original Poster
2,014 posts
87 months
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Marf said: Last time my MR2 was on the dyno, 265lb/ft so 132lb/ft per litre without factoring in your 200% VE That was at 1 bar? If so that would make it 66lbft/litre corrected?
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V88Dicky
4,570 posts
52 months
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Torque per ton much more telling, surely? Anyway, mine's 65lb/ft per litre but.... 220lbs/ft per ton 
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Kozy
Original Poster
2,014 posts
87 months
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V88Dicky said: Torque per ton much more telling, surely? Anyway, mine's 65lb/ft per litre but.... 220lbs/ft per ton No it's pure as a comparison of engine efficiency. It's linked to BMEP which is a sort of industry standard, but specific torque is a lot easier to understand. Torque to weight is no use compared to power to weight.
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Marf
22,907 posts
110 months
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Kozy said: Marf said: Last time my MR2 was on the dyno, 265lb/ft so 132lb/ft per litre without factoring in your 200% VE That was at 1 bar? If so that would make it 66lbft/litre corrected? 0.9 bar 
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Kozy
Original Poster
2,014 posts
87 months
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So 2000cc * 1.9 (Absolute pressure) = 3800cc = 69.5lbft/litre.
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jfdi
297 posts
44 months
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Passat 2771cc NA petrol 207lbft = 74.7lbft/litre
Alfa 147 1910cc FI diesel 225lbft = 117.8lbft/litre (no idea of pressure)
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Blayney
443 posts
55 months
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If you can find out the pressure of the turbo in a Renault Twingo I'll be happy to add it in...
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brt900
152 posts
37 months
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my remapped arosa 1.4 tdi is 186 lbft so thats 138.2 lbft/litre
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Gaz.
47,132 posts
120 months
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S20000 = 153 = 76 per litre
Celica = 133 = 73.8 per litre
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Crusoe
2,645 posts
100 months
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BMW 130i NA - 2996cc - 232.3 ft.lbs and 261bhp
So 77.64 lbft/litre
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Leins
1,193 posts
17 months
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BMW M3 CSL => 273 lb-ft / 3246cc = 84.1 lb-ft/litre
Alpina C2.5 => 188 lb-ft / 2494cc = 75.4 lb-ft/litre
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spitfire4v8
1,306 posts
50 months
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I spent a week trialling inlet lengths and cam timing on our tvr t350 race car. I ended up with 310lb.ft at 5500rpm as a peak number. 310 from 3.6 litres = 86lb.ft/litre
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RenesisEvo
1,834 posts
88 months
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320Nm is about 236 lb ft, 1781cc so a specific peak torque of...
132.5 lb-ft/litre. I've no idea what the boost pressure is to get a ratio of VE for comparing to NA engines.
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Zwolf
22,321 posts
75 months
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'90 BMW 750i: 330 lb ft / 4,988 cc = 66.16 lb ft/litre '98 BMW 323i: 181 lb ft / 2,494 cc = 72.57 lb ft/litre '12 Focus 1.6i: 111 lb ft / 1,596 cc = 69.55 lb ft/litre All naturally aspirated petrol engines. The Focus will be replaced in due course with the new 1.0 EcoBoost engine and having now driven it, can't wait: '12 Focus 1.0T: 125 lb ft / 999 cc = 125.13 lb ft/litre. It also has "transient overboost" for 30 sec spurts of overtaking, which makes for: '12 Focus 1.0T: 148 lb ft / 999 cc = 148.15 lb ft/litre. Evo review of the Ecoboost 1.0. which provides some technical insights: article said: The engine is a long-stroke three-cylinder, with direct injection, variable timing for both inlet and exhaust camshafts, and a tiny turbocharger that’s able to spin at up to an incredible 248,000rpm.
...
The 'brake mean effective pressure' is the ultimate measure of engine efficiency. A naturally-aspirated engine usually measures around 150psi here (that's the peak pressure on the piston crown), a good turbo well over 200psi. This tiny EcoBoost scores an extraordinary 348psi, all from an engine whose cast-iron block is small enough to sit on a sheet of A4 paper.
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otolith
19,345 posts
73 months
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The Saab does 273lbft in overboost at (I believe) 1.5 bar from 2.3 litres = 118.7 lbft/l unadjusted, 47.5 lbft/l adjusted.
The Nissan does 268lbft from 3.5 litres = 76.6 lbft/l
The Lotus does 133lbft from 1.8 litres = 73.8 lbft/l
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StottyZr
4,073 posts
32 months
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I think thats quite a good calculation. I wonder if the results actually show anything.
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RenesisEvo
1,834 posts
88 months
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Zwolf said: All naturally aspirated petrol engines. The Focus will be replaced in due course with the new 1.0 EcoBoost engine and having now driven it, can't wait: '12 Focus 1.0T: 125 lb ft / 999 cc = 125.13 lb ft/litre. It also has "transient overboost" for 30 sec spurts of overtaking, which makes for: '12 Focus 1.0T: 148 lb ft / 999 cc = 148.15 lb ft/litre. Evo review of the Ecoboost 1.0. which provides some technical insights: article said: The 'brake mean effective pressure' is the ultimate measure of engine efficiency. A naturally-aspirated engine usually measures around 150psi here (that's the peak pressure on the piston crown), a good turbo well over 200psi. This tiny EcoBoost scores an extraordinary 348psi, all from an engine whose cast-iron block is small enough to sit on a sheet of A4 paper. Impressive - the bmep figures are often very hard to find, but that sounds good (assuming it's not inflated, erroneous marketing numbers). Hopefully there will be some data soon on real-world economy for the 1.0Ecoboost, early reports suggest much better than the Fiat TwinAir but it's still too early to know.
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vrsmxtb
1,207 posts
25 months
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Standard Fabia VRS - 120lb ft per litre. Mazda MX5 18 - 61 lb ft per litre No wonder the Fabia feels twice as quick... 
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