Old Engines are inefficicent at creating power/torque,WHY? 3

[mechanicat16]

Why do old engines produce such little power for their displacement, for example, the 1968 426(7.2L) hemi produced 425HP.The modern 6.1 L hemi produces about 425 HP, the same as the 7.2! Why is this?

 

[TheBlacksmith]

I had a 1970 Olds 442 (L69 option) with a 455 4 BBL and turbo 400 automatic. No ram-air, no eotic parts, but it was well maintained and tuned to factory specs with quality parts. I have no idea how much horsepower it made, but I suspect it was more than the 365 at 4600 Olds claimed. I outran more guys with big dollar engines on the street that were carboned up, backfiring, missing at high rpm than I can count. It would also start and run at temperatures below zero (F) in Buffalo NY winters.

 

[LionelHutz]

So... Agreed that time marches on and things change. However,I'm sorry, but 1.7hp/cu.in. in a NA, two valve, pushrod domestic V8 running on 91 octane gasoline is just more than I can accept without some REAL numbers from a reputable, believable source. I'm sure you are convinced in your belief...So be it. I choose to remain skeptical until proven otherwise.

Ya, I've a few dyno numbers for Vette's with around 450 to 500 crank hp from stock displacment LS1's (350 cu-in) that would still run on Sunoco 94, but I don't recall ever seeing anything at 600hp without a displacement increase.

I see a lot of people who go "I remember back in the day..." and describe how awesome the old American muscle cars were. It's mostly looking back at those times with rose colored glasses. For the most part, the muscle cars from the 60's and 70's had poor chassis and suspension technology and crappy tire technology with engines that needed high octane fuel and badly polluted and constantly went out of tune and tended to quickly wear out, typically needing a rebuild before the 100k mile mark.

To compare, many of todays engines will easily run 200k miles plus with only oil changes and a couple of spark plug changes.

At a car show last summer, I saw a old Charger (probably about 69-70 vintage) that had the whole floor cut out and then the body was welded over a new Charger chassis. That's certainly one way to make an old muscle car perform as well as many people remember they do.

As already stated, every aspect of building a new engine from design to finished product has been improved. Time does march on and better does happen. It'd be naive to think an old engine design will perform as well as a new design. The old design can be updated using the new technology but that's a different arguement.

 

[ornerynorsk]

Well said Pat. Mind you, I am known for an ample supply of BS . . . and absolutely, dynos do vary. But, that said, a fearful amount of horsepower can be wrung from an engine when all the factors are in harmony with one another.

 

[evelrod]

"Do you doubt the V8 Supercars claimed 650HP?"

No sir, I do not doubt that the numbers they quote are actually numbers they may have seen on their dynos. Mainly because I recently watched a NASCAR 358 Ford running at 750hp on a Superflow...it was totally strung out, too.

Was what I saw accurate? Is what the Supercar guys claim accurate? Are the numbers I just got today on our Lotus/Cosworth accurate? Probably NOT. Leave the high hp numbers to the salesmen and the dorks that believe all this crap. A dyno is only good for comparison. Anything else is subject to interpretation.

Does all this change my mind about an old school domestic iron block 360 @ 600hp on 91 octane? Nope.

Rod

 

[Marquis]

"Why do old engines produce such little power for their displacement, for example, the 1968 426(7.2L) hemi produced 425HP.The modern 6.1 L hemi produces about 425 HP, the same as the 7.2! Why is this? "

I've been involved in the development and homologation of some high performance modern engines. I've recently moved to the USA and have been getting into old American Muscle- looking really deeply into the engines- trying to build GT power simulation models of my 440 R/T DOdge and a 426 Hemi, I also know the new twin plug Hemi very well.

For starters the homologation back then when the 440 6 pack was rated at 390 Bhp and the Hemi at 425 bhp- was optimistic. It's true that the 425 Bhp Hemi was 'under rated' by contemporary standards but if it were re-homologated by todays SAE J1349 or DIN standards it would still be lower than the rated 425 Bhp. (My colleague worked at Chrsyler and has the VE and fueling figures to hand- this is what I'm basing my GT power model on).

back to topic- the reason why things have progressed:

First of- engines breath alot better. 4 valve heads is an obvious one- but even if you compare a modern 2 valver with an older one- the flow for a given port size is alot better so the port mean gas velocity/flow compromise is better optimised.
The next is runner lengths- alot of these cars were running carburetteurs- with an intake manifold compromised for fuel flow distribution AND air flow distribution and no room for tuning. Even in the 80s Chevy ran fuel injected cars with no tuned intake lengths for the normal engine operating range.
Back pressures for alot of the more mundane Buicks and Oldmobiles were high compared to modern high performance machinary. The Aston Martin Vantage V8 has a peak power back pressure of only 350 mbar, an E39 BMW M5 has a back pressure of 250 mbar, looking at an LT1 engined 1996 camaro- I've measured the back pressure at 600 mbar. I know people WITHIN the big three that think that's a Good figure. The intake losses were high on many american domestic cars- the same Checvy LT1 engines thing has an intake losses of 80 mbar. A Jaguar XJ8 has an intake loss of around 33 mbar.

Sophisticated engine management systems have allowed higher compression ratios to be specified with fine knock control.
Cam profile design has come a long way- even staying with the pushrod configurartion- the new LS7 engine has a light valve system mass- a very high rocker arm ratio (1.8:1)- compare that with a 440 RB big block of 1.5:1, allowing a peak valve lift of 15 mm!! Piston masses have gone down- which in league with valve train design improvements--sees peak power speeds on V8s going up from the norm of 4800-5200 rpm to 5800- over 6500 rpm. If we start looking at Hondas and BMW M engines- MUCH much higher!
In cylinder charge motion has finely developed tumble motion optimisation which allows more ignition advance FOR A FAST BURN before the onset of knock.
Engine bearing friction has come down- if you look at the size of the bearings of an old Mopar- they're way oversized for the IMEP the engines made. The "RB" big block especially so- the 'B" Big block Mopar sizes would have been just fine.
So we've covered port flow, manifold design, CR, combustion, friction and ECU control of it all.
And that about sums it all up

http://www.auto-scape.com

 

[GregLocock]

Our engine designers used to get narky if the backpressure reached 6 psi, that's 400 millibar in the new money.

Now with Euro V coming our way I imagine that number has increased, just due to the extra cats, but I don't do engines or noise any more, so that may be misleading.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Five9dak]

I'd like to point out that the person who originally mentioned 360s did not sepcify displacement. The mopar small blocks can be built into some very large(~472ci) and very stout strokers.

I had some personal expereicne wiwth a pump gas 425" 360 that made ~540hp NA. That motor had a conservative cam choice as it was slated for EFI use. 600 is certaintly not out the question for an NA mopar small block on pump gas. 600hp with 360 cubes- I have not heard of, but I wouldn't mind being wrong.

 

[MastDesgin]

Engines have always been under rated from the factory if they were in performance models.

In Japan the 276HP LAW was inacted because there government thought that the 300ZX Twin Turbo was fast enough and governed that no car in Japan could be rated at any more so skylines, Supras, and NSXs all got down rated in japan though they were capable of much more, stock skylines and supras are capable of over 400 HP with a twist of a boost controller.

In America they underrated from the factory for insurance but the way they measure HP is different from how it used to be. What we think of as 505 from the new corvette would be much higher to them back then, a stock Z06 2010 vette would smoke any old stock muscle car.

This sorta relates to OP's question as to power, Cars have made huge leaps and bounds in technology and people are working on it more and more everyday, the next BIG tech to hit cars will be solenoids for there valves, the valve train sucks up to 25% of the engines true power output just to turn. But before that we will have DISI injection (direct injection similar to a diesel but much lower pressure). DISI allows for much leaner mixtures to be used at higher boost/compression to lower knock and increase fuel mileage.

So to answer the question: Humans got smarter and built better machines.

 

[YvesLLewelyn]

Not every computery/electronic new idea is an improvement (a lot are though). I doubt if we will ever see any production use of solenoid (or hydraulic) valve gear. DI is a possibility but I have heard that Commodore (GM) DI is no useful improvement over ordinary EFI.

 

[BrianPetersen]

Yves, direct-injection is already in production: VW FSI/TSI, Hyundai GDI (2011 Elantra), Mitsubishi GDI (many models), and several others.

And, Fiat's Multiair system appears to be a practical way of getting almost infinitely variable valve timing and lift. It still uses a camshaft, but uses a solenoid to regulate a hydraulic circuit between the cam and the valve. It's in production.

Direct solenoid actuation of the valves is not likely to see mass production in the foreseeable future. Multiair and other similar systems achieve the majority of the benefit at a fraction of the cost and electrical power demand.

 

[SomptingGuy]

Yep, GDI is becoming fairly common ... at least in Europe and Japan. But direct solenoid actuation of valves is likely to be limited to use on research engines, where full flexibility is desired.

- Steve

 

[YvesLLewelyn]

Brian/Sompt - Have a look at this road test on a new Holden Commodore with SIDI - not too impressive considering all the hype from Holden.

http://theage.drive.com.au/motor-news/bathurst-1000--with-a-twist-20091009-gqou.html

 

[BrianPetersen]

That engine is probably optimized for power and the transmission optimized for smoothness. Initial impressions of the new direct-injection 2011 Hyundai Sonata were favorable regarding its fuel consumption, and the VW 1.4 TSI is another good example.

 

[RossABQ]

All of Ford's EcoBoost models, I believe all GM engines 2.4L and above (not in trucks) are DI.

 

[YvesLLewelyn]

Brian - the Ford's engine is a full litre bigger than the Holden (4l against 3l), and the Ford is more than a second faster to 60mph - and yet the Ford uses less fuel - where is the SIDI Holden better? Unless there was something terribly wrong with the Holden this cannot be seen as a victory for SIDI.

 

[BrianPetersen]

All it means is that particular engine, in that particular drivetrain, in that particular vehicle, under those operating conditions, isn't all that great (and this isn't the first time I've heard that about the 3.0 litre version of the GM HFV6).

It shouldn't be considered a blanket condemnation of that engine concept. Your comments on the 2011 Hyundai Sonata, please.

- Best in class power output
- Best in class (gasoline non-hybrid) fuel consumption, and it was possible without too much difficulty for road testers to beat the US EPA estimates.

No doubt some is due to good aerodynamics and attention paid to weight reduction, but it's also the only direct-injection engine in its class in the North American market.

 

[GregLocock]

My guess is that the SIDI engine would have reasonable fuel economy IF they changed the trans schedule. The problem then is that the car would feel gutless and fail in the important tests, standing 1/4 and 0-100.

Fitting rather untorquey engines into fat cars is always going to be a bit of a gamble. 40 years of experience says you won't be particularly happy with the result, but the pimply faced youth managers will know better. Although of course the front-line engineers will get the blame when it only achieves two out of three program goals.







Cheers

Greg Locock


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[LionelHutz]

Which car is heavier, the Holden or the Falcon? They were driving around a road course presumably accelerating and decelerating a fair bit. This should give the ligher car the advantage.

They was also some comment about never going more than 60kph during the testing.

Take both out on a freeway and set the cruise at say 80kph or 100kph for a good run and see where the economy is.

 

[Ultraworld]

I own a '69 Torino Talladega clone with a 428SCJ. The entire car is brand new. The engine was carefully rebuilt with attention to the heads & the entire valve train. I also own a '05 GTO W/LS2, 6speed. This engine has very minimal mods. They both have the same tires/width. They have similar gearing.The GTO is faster, much faster. It turns in 18mpg in spirited driving. Don't ask what the Torino turns in. I'm considering installing an Edelbrock fuel injection system & a 6 speed trans in hopes of being able to use is more. Why is the newer car faster? Any ideas?

 

[evelrod]

It's already been said, but for those of you not paying attention---The engineers in the automotive field have not been asleep for the last forty years!

Rod