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Looking at compression ratios for my cars...
The engine that came with the '91 Caprice Classic (later transmogrified to Biscayne SS) was a 305 cubic inch L03 V-8 with a 9.3:1 compression.
87 octane was its fodder and it ran no different if you gave it the more premium blends.
10 to 1 was unheard of in street engines from the OEMs back when I was coming up.
Guys did it.
Older cars from before the dark times had it, but...
The magazines had dire warnings about compression ratio and octane.
Now?
This is one place I really like computers in cars.
I like electronic fuel injection. I like sequential multi-port injection.
Motors that last past 100k miles are nice and ditching carburetors (and throttle body injection) was a key factor in increasing engine longevity.
Marv and I were marveling at engine builders getting power from 325 ci (5.3l) engines that needed 400 plus cubes just not all that long ago.
OK... it was a LONG time ago, but I'm old and it seems closer than it is.
But I remember when 1 hp per cubic inch was a worthy goal and took some doing to achieve.
That LO3 sure didn't. 170 horsepower.
The 350 cubes in The Biscayne's LT1 didn't. 260 ponies.
The 350 I swiped from a pickup and put into my old '79 Camaro didn't. I "made do" with 300.
Now it's nearly routine.
The L77 does fall a little short. 362 hp from 364 cubes. But still...
Even back in the year 2002 GM was making some pretty good engines. The Ramjet 350 crate motor I had was just 9:1 compression, small valves, batch fired port injection and still used a distributor, but it made 350 HP from 350 CI and 400 lb-ft torque. Plenty to be able to break a few transaxles. - Marv
ReplyDeleteThe 5.3L V8 (around 325 CI) in my wife's Silverado is factory rated at 355 HP which is more than 1 HP per CI. It's "direct injection". The first thing she did when she got it was go to the parts counter and order GM's performance exhaust and air box because she said it was "too quiet". I made her install them herself with minimal assistance from myself (a few things require two sets of hands, mainly getting the original exhaust off). She thought I was being lazy... but now she can say "I did it myself". Those actually made a difference you could feel, probably mostly from the intake, the original was super restrictive looking. The 2015 5.3 has noticeably more get up and go than the 2010 5.3 that we had. 313HP vs 355HP is part of that but it's no small matter also that a bunch more things are aluminum, composite or carbon fiber on the 2015 and according to the specs it lost close to 700lbs (a big chunk of that being the engine block which went from cast iron to aluminum).
ReplyDeleteThe LS3 in my C6 is 6.2L which is around 377 CI and rated at 430 HP.
Surprisingly even the tiny little 2.8L I4 (around 170 CI) in my little red Colorado is rated at 175 HP. That's more than a lot of "sporty" cars from the 1970s and 1980s, and given its surprisingly low curb weight (around 3600 lbs) and it being a 5-speed (New Venture Gear 1500), it will actually surprise a few people. The biggest limitation for it is that it direly needs a posi upgrade to the rear end. I've gotten super spoiled by everything else I've had in a long time having some kind of posi or traction control.
-swj
Knock sensors and CFD have enabled engineers to push higher compression and more optimized combustion. From the Ford side, a 5.0 Windsor from 1990 is about 180 HP, the 5.4 Triton in my 02 pickup has 9:1 compression for 260 hp out of 330 CI. The 5.0 Coyote truck engine has 10 5:1 compression and 360hp out of approximately 302 cubes
ReplyDeleteAt the extreme the Mazda Skyactiv in my car runs 13:1 compression and makes 180hp out of 151 CI or the same power as a 1990 5.0 V8 with half as much engine