Engine Power Calculations: Debugging Speed


See John Cadogan, our Metric Facinated Australian Car Critic. I give him a constant hard time on You Tube and the FourEyed Pride forum, because with a Friend of the AustralIan car industry like this, who needs enemies?

Check out this guys "B@st@rdized BMEP" on his latest video.


Compare it to the late Vincent/ Repco Technician Phil Irvings Aspiration Index Calculations.

The specific power per engine size and rpm had been dropping for years, now it's on up again.

All Because of Boost Ratios and Direct Injection. A little history lesson:

Aspirations Index is a term for efficiency. In a non metric environment, it's best determined by ((A cubes Times[*] B rpm)/C hp [net crank dyno figures].

This gives = Ai [a real number]. For Met(ric) Heads Your B.BMEP figures are bracketed.

See how real specific power for every rev and cube has improved from 1932 to 2003, then started getting worse because turbo boost and direct injection is forcing car makers to detuned the normally Aspirated power before the turbo or supercharged boost is added.

When its calculated on a 1932 221 Flathead Ford, its was high as 11500 or a Briggs and Stratton like 3.96.

A smog spec 1980 4.2 Mustang V8 has 9643 or 4.72

A smog spec 1980 3.3 Mustang L6 has around 8675 or 5.24 B@BMEP

A smog spec 1980 5.0 LTD V8 has 8427 or 5.40.

We have an pre emissions Aussie 250 Falcon (1974) 1-bbl with 7089 ( 6.42 B@BMEP),

A smog spec 1985 5.0 HO EFI has about 6174 (7.37)

A smog spec 1985 4.1 EFI Falcon has about 6097 (7.46)

A 74 De Tomaso GT5 with its Cobra Jet HO 351 has 5760 (7.90)

An '89 Ford SHO Taurus has 5157 (8.82)

An LP400 Countach (1974) with 5120 (8.89)

A smog spec 1992 4.0 SOHC Falcon XR6 has about 5058 (9.00)

A 243 2008 Falcon EFI Twin Cam VVT with 4869. (9.34)

The best non supercharged US 5.4 engine, a DJR 320 Falcon, gives almost 4000. (11.27 actually)

A NASCAR would run about 4000, the same as the best DJR 320.

Interestingly, the old 3 lit(re) 183 cube F1 non turbo engines reving to 18000 rpm, and getting 850 hp, got only 3875, or 11.74.

Larry Widmeyers Soft Head 498 8.168 lit(re) engine made 860 hp at 5700 rpm without a turbo...3301 aspirations index or 13.78 B@rstardized BMEP. No turbo. No Direct Injection.

When its calculated on a lowly old Australian Vee Eight Super Car Touring cars 2 valve per cylinder 5000cc EFI V-eight made 630 hp at 7500 rpm, that's a 3631 Aspirations Index, or 12.53 B@stardized BMEP.

Beeep MEEeeep....
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Here is a recent video on a 284 hp 225 Sant Six Uncle Tony''s Garage comented on.

284 hp at 5700 rpm, 1.26 lb-ft per cube, 60 though over 3.445 x 4.125, 231 cube six with three DCOE 45 Weber with 40 mm chokes. That 56 year old engine puts out better specific out put than a 2021 Kia Sorento V6.
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The Eaton/Rootes M90 Supercharged 8.7:1 compression GM3800 engine is also exactly 231 cubes. ..just like the overbored 225 Slant six. Stock with 16 degrees advance and 91 Research Octane over Motor Octane, it puts out 282 hp gross and 291 lb-ft on the dyno. Just like the 56 year old 225 with Triple Webers on 95 RON/MON with 10.5:1 compression

Here is Richard Holdeners latest re-test on an L32 headed L67 3.8 liter.

Before adding more than the atock timing and some othet modifications, his test in West Tech showed no progress over the Independent Runner Port on Port Slant six. Both engines make the same power and torque at the same revs. The V6 is supercharged to match the Triple 45DCOE's

Aspirations index for 282 hp at 5700 rpm from almost 231 cubic inches displacement is 4669, or a B@BMEP of 9.74. That's SAE Gross dyno horsepower, which is usually 14.7 to 16.6 percent below DIN or Certified SAE net.

Concidently, in 1983 the last Argentina made Renault Torino GR 230 used a three Weber 45DCOE''s with 38 mm chokes and made 248 hp DIN net at just 5000 rpm. Nearly the same Aspirations Index and B@BMEP as those two 241 cube sixea. The Renualt engine is the old M175 AMC troop carrier or Kaiser based Nash engine, SOHC, but with a better seven bearing, fully counterweighed crank.

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