staringback05

iTrader: (8)

breath killer....you gotta remember not everyone knows your new to this stuff....alot of guys on here have been around these cars for a long time and they see these questions over and over again.....its like the "are we there yet" question

300bhp/ton

That's not true. It's all about specific output.

OHV push rod V8's have only ever had one thing as their main advantage - displacement. However the efficency of them is comparitivly very low.

Take the great Mopar 426ci Hemi it was officially rated at 425bhp but this was GROSS. But even taking that into account it's only managing 61bhp/litre from what is meant to be a race engine.

Today you can buy a 528ci Hemi with 610bhp. But that's only 71bhp/litre. Good for an old school engine but hardly Earth shattering. The Lsx line of engines is pretty impressive and will allow a state of tune to produce around 95bhp/litre for road use n/a.

But in reality 95bhp/litre isn't all that impressive for an internal combustion engine. Many multivalve engines are capable of 120bhp/litre in stock trim and 140bhp/litre+ modified for road use.

So displacement only wins providing it's backed by efficency. Hence a 7.7 litre DOHC motor can produce more HP n/a than a 8.3 litre OHV motor.

BrandonDrecksage

iTrader: (1)

On a side note, this is where gearing comes into place. Those 120 per liter engine have to have gearing that is very suited to them because generally they are peaky(like the honda s2000). If the s2000 had crappy gearing like a stock ls1 fbody, it wouldn't be able to over come that cause of the lack of low end torque. Now on a fbody, it sucks, but the low end torque compared with the top end breathing of a ls1 sort of fixes it.

basically, there are way to many varibles to say which cause would be faster.

99blancoSS

iTrader: (115)

You find me one 383 that has less power than a 350 and I'll eat it. This is getting semi ridiculous now. I'm out of this.

SHINER

iTrader: (18)

Chill out man I seriously thought he was talking about LSx type motors. I cant stand people like you that get to wrapped up in to arguments like yourself.

300bhp/ton

Well not quite.

Remember the S2000’s engine is only 2.0 litres displacement it’s also a fairly short stroke motor making ideal for high rpm use. So the fact that this particular motor is peaky doesn’t mean that all high specific out motors would be. A 2.0 OHV 2 valve per cylinder 4 cylinder engine would not be able to produce the HP the S2000’s DOHC motor does.


Multivalve engines will 100% match OHV’s in the low rpms but be able to carry the performance to higher rpms without running out of breath.

Example:

A 2 valve per cylinder engine (OHV/OHC/Vee/Straight/Flat/whatever

Stock it has an optimum operation rpm range of 1500 thru 5500rpm. After that point it really starts to run out of breath.

Sure you can add a high lift cam, bigger valves and heavier valve springs to control the increase lift and large valve mass. This will increase wear rate.

So modified the rpm range has been extended to 7000rpm at the top end, but down low it’s know dead before 3000rpm.

Stock 1500 – 5500rpm
Modified 3000 – 7000rpm

You can move the operational range but not extend it (not by much anyhow). This means engines become monsters or total pigs to drive with crappy idle and fuel economy.


A multivalve engine is able to do far more due to curtain area.

So stock a multivalve engine may have a operational rpm range of 1500-7000rpm. This means it can match a 2 valve setup down low (providing bore, stroke, displacement and other vital variables are consistant) but has the same ability as the modified 2 valve in the higher rpms. Best of both worlds.

Of course you can then modify the multivalve engine and exceed the 2 valve setup in every performance area.

The only downside to multivalve engines is complexity, size and weight. But all of these can be overcome as an entire package.

Hence many engines in the past which have been 2v OHV have been converted to 4v DOHC for competition use.

Imagine slapping some DOHC heads onto a Ls1. Sure it would make it a bit taller and heavier but nothing too detrimental as its already a compact engine. Plus the Fbody is a big car so even an extra 50-80lb of engine mass isn’t really an issue. But you could then run a setup that makes the same HP as a TREX cam but drives and idles like stock. Or indeed you could go a lot wilder than the TREX if you wanted and still remain very streetable.


Faster really isn’t the issue as quite evidently the LS1 is far more powerful than a 2.0 litre Honda.

Where it would get interesting is if Honda built a 5.7 litre/346ci DOHC V8 with the same specific output as the S2000 motor.

S2000 = 240bhp / 2.0 litres = 120bhp/litre

120bhp x 5.7 litres = 684bhp

So potentially a STOCK Honda 5.7 litre DOHC V8 could produce over 680bhp while still meeting all emissions requirements and running a stock exhaust system with stock like driveability.

Compared to the Ls1 5.7 OHV making 350bhp stock. Even the Ls6 with 405bhp looks puny by comparison.

This is purely hypothetical however, as no such engine exists. Honda simply doesn’t have a need for such an engine. But it doesn’t alter the possibility of it.

Real life example:

TVR 7.7 litre DOHC V12 was rated at 800bhp (although some sources say 880bhp) STOCK.

A Dodge Viper with 8.3 litres only manages 500bhp. Even jazzed up 650bhp n/a is hard work.

unit213

This is some mighty fine bench racing here gentleman. HP/L is discussed was covered.
Now all we need is fuel economy and a VTEC discussion to wrap things up nicely.

Cobras_Rule

iTrader: (4)

I agreed with you untill this point...

There is always a need...

Both Ford and Chevy need to get with the program...
Ford needs to stop bullshitting with displacement and make some real motors. Back to 5.0's and 5.8's I say... Just multi valve V8's. They had a 427ci V10 that made 500hp... WTF!?!... Put that **** in a car....

And Chevy needs to get out of the stone ages with this pushrod crap and make some multi valve 346's, 383's, 396's, and 427's...

Im just tired of hearing the hp/L comment from all the turbo imports.

Pro52R

iTrader: (15)

Why does GM need to make things more technical?

You can have 4 valves and still keep the cam in the block...No need for 2 miles of timing chain and 4 cams to buy. That just makes everything more expensive.

GM has just won a patent on a 3 valve head...also rumors of them making a block w/ 2 cams in it..??

Also..Those 4bangers might be badass and make tons of power...but how long are they goin to last on 20+ psi and making 500+ hp??

I am pretty sure an LS1 could last a pretty good while on 500hp. GM does know how to build some wicked DOHC 4bangers.Look at the Ecotech..there are guys making 1400hp on them..I hear the internals are good for 600 stock.

I always here..Theres No replacement for displacement..So peopke say yes..Its boost...ok..Boost the higher Displacement motor...and bam..Discplacement wins again.

Lets throw Diesel's into the mix. May only make 500hp..but your torque is close to 1200ft lb and thats right off idle. Plus you'll get 15-20mpg.

I mean there are crew cab duramax's close to 7700lbs running 12's w/ nothing more than tuning and a 150shot.

Cobras_Rule

iTrader: (4)

More technology = more power provided its built and programed that way.

As for the timing chains... you would have 2 that are not that long and 2 more chains much shorter. I guess having a motor with 32 pushrods would be better? Provided the pushrods stay the same legnth (7.4") thats barely shy of 20 FEET

SHINER

iTrader: (18)

Couldnt have said it any better!

staringback05

iTrader: (8)

ahh damnit dont give them any ideas

stokedporcupine

yeah, i was, and still am there too..... but i dont get pissy and cry when someone tells me something i said was stupid. i accept it and move on, because i know i DO say stupid things. i dont get offended and throw the finger at people....

grow some thicker skin

SHINER

iTrader: (18)

This thread is going no where and I have a feeling its going to be nothing but a long argument.


Locked.