pushrod vs. ohc

+1

Just compare hp/L figures between Corvette engines and other high-performance NA engines (any displacement). The fact that GM is still using pushrods and 2-valve cylinder heads is pretty pathetic.

 

Let's compare lap times and see who's got cash left over for dinner.

 

These guys made a big splash a few years ago:

http://www.coatesengine.com/csrv.html

but, since it hasn't had wide acceptance, it can't have an overall big advantage IMO.

Do an internet search on "rotary valves engine" and you should get quite a bit of stuff.

 

Who cares how many inches it is? What matters is HP/LB or HP/$$.

 

That's exactly why I said look at hp/L of various engines to compare efficiency.

Corvette, 72hp/L
Honda S2000, $5700 engine, 120hp/L.

That's just one example. These GM engines are just crap.

 

exactly and and MPG as well because the major auto makers need to mee the corpoate average standards and big slow turning engines get good milage. The vette gets 25 mpg highway or some crazy number like that.

 

Those are fine, but they're useless metrics for engine efficiency which is what this thread is about.

Why can't GM just go to overhead cam and 4-valve. There's no downside.

 

The downside is cost, weight, mpg.

 

Whgere did you get that number? google says used engines are bring more than that?

 

Vig- Your metric is worthless in the real world. The only real measures that count are weight vs hp, $ vs hp, and mpg, like Brian said, and the GM V8s do very well in those measures. Your measures have nothing to do with efficiency, but are techno-freak numbers like how fast your PC runs.

If I build a 1000 lb engine of 3 liters capacity that gets 200hp/liter, it is great by your measures and sucks by mine, since I have to carry all that mass around. The 7 liter LS7 engine weighs around 500 lbs and pumps out 515 hp and would provide far superior performance to the example above with fewer horsepower. Plus the engine gets very good mileage in a 3150 lb car because it runs on a whiff of throttle at cruise. The only other engine that comes close is the AMG 6.2 liter, which has similar numbers, except possibly cost.

The answer to why does GM not go to all DOHC, 4 valve engines is because the increase in cost has to be balanced against any increase in performance, and right now the pushrod V8s are doing fine and cost less to build.

Taz
Terry Phillips

 

Cost, yes. But it'll be a one time cost creating a new engine. After that they just have to develop it as they have been with this one.

Weight, no way. Going to ohc will reduce valvetrain mass and improve efficiency. It'll also reduce structural mass by allowing tighter packaging of the heads and block.

List price is for suckas. It's actually less than $5400.

http://www.hondaautomotiveparts.com/auto/jsp/mws/prddisplay.jsp?inputstate=5&catcgry1=S2000&catcgry2=2001&catcgry3=2DR+S2000&catcgry4=KA6MT&catcgry5=ENGINE+ASSY.+-+TRANSMISSION+ASSY.

 

Vig- The real world says you are wrong.

Taz
Terry Phillips

 

Italia had such as system in the 1910s. Go to this link and scroll about halfway down to learn about Itala's rotary valve system...

http://en.wikipedia.org/wiki/Itala#Itala_rotary_valves

 

no, it's the cost per engine that is the issue. more parts = more money.If you are talking about a single ohc 2V engine then you could come pretty close to the pushrod price, but 4V or DOHC, no way.

Nope. The valve train wieght is insignificant compared to engine weight and a pushrod engine has a lower total weight and lower center of gravity than an ohc engine of equal output.

Still not an engine....not even a true long block because your looking at another $1000+ to get the head on.

A brand new TURNKEY sbc???/ $2600 ready to run

http://www.crateenginedepot.com/store/350-Crate-Engine-290-HP-Deluxe-19244450-P2544C2.aspx

 

Why are we talking about a 1000lb engine? Are there any high-performance engines out there that don't do well in weight? The GM V8 is probably one the worse ones in this regard too since other high hp V8's are also aluminum, but are of smaller displacement and have a valvetrain layout that lends itself to tighter packaging.

The Corvette gets good mileage because it has a really long top gear. If you really want to compare engine fuel efficiency, we'd have to look at steady-state bsfc. Does anyone know for a fact that the GM V8 is better than others in this respect?

How much is a new LS7 long block from a GM parts dealer? I ask because I don't know.

I'm assuming you're addressing my last post. I admitted there's a cost involved with going to ohc. You don't think holding all else equal, getting away from pushrods would reduce mass and by virtue improve efficiency?

 

Google "coates", "fraud" and the "SEC" and you will have your answer.

 

Who cares about hp/L?

I care much more about absolute power output, efficiency, weight, torque, reliability. Let me know when someone else comes up with a 500hp engine that will go 100k miles without anything but oil changes, that get 25mpg and weighs less than most smaller engines.

Then I'll be impressed.

But, if HP/L is your thing, then here is your god... the highest HP/L production car ever made - the Suzuki Cultus!


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You really haven't thought this through, have you?
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The only things required beyond the head and shortblock assemblies are the head bolts, water pump and timing chain, $230. Everything else is there.

 

Vig- You are the one that used that measure, not me. Weight is not a consideration in your measure, which makes it pretty worthless in the real world. Take one of the measures Brian or I used and screw up the numbers if you can.

My 575M has a really long top gear, too, but it gets nowhere near the gas mileage of the Z06. I should know, I traded an 08 Z06 towards the 575M. The two LS7 Z06s I had were getting 23 mpg back and forth to work. Not going to happen in a 575M or 599, both of which have similar high speed gearing and bracket the Z06 in performance. The Z06 gets way better gas mileage around town, too, where you never reach 6th or even 5th.

An LS7 crate engine is ~$25K. remember that metric 500 lbs, 515 hp, and the LS7 is a very compact engine, the same size as the original 1955 265, but a whole lot lighter.

Performance pushrod engines are not dead by a long shot.

Taz
Terry Phillips

 

Google up "sleeve valve". In aero-form these were completely competitive with poppet valve engine in WW-II, in power, power to weight, and service live.

 

Would not fit under the hood of the Vette.

 

LS9 crate engine is $25K, 638 HP
LS7 crate engine is $12K, 505 HP

 

Vig, quit reading so many import tuner magazines. Go out in the real world and get a dose of reality.

 

You have no idea what your talking about. Leave the thread. OHC engine smaller and lighter??..show me...