Pushrods vs Overhead Cams

[MasterOfReality]

Ummm not if those stats you gave are correct, because...

LS7 is 377kw @ 6300rpm and 637NM of torque @ 4700rpm with a 7000rpm redline. Whack a charger on that and use the LSX block and you're laughing

ahah, ok, what if it was based on engine size?

I believe the LS7 is a 7 litre and only produces 2kW and 7Nm more?

Therefore the AMG produces more hp per cubic inch.

 

[SweetWagon]

ahah, ok, what if it was based on engine size?

I believe the LS7 is a 7 litre and only produces 2kW and 7Nm more?

Therefore the AMG produces more hp per cubic inch.

well if were talking hp per ci, then bmw takes that one... new v8 4.0L, 309kw 400nm.

 

[HaMmErD]

well if were talking hp per ci, then bmw takes that one... new v8 4.0L, 309kw 400nm.

those torque figures are a bit lame for a v8 .... although considering its only a 4.0l .... id be dissapointed IMO :whistling

 

[SweetWagon]

dont really need torque when it revs out to 8000

 

[grigor]

Simplicity? Ha ha ha ha
VVTi...VTEC....**** me dead....how much **** can these guys come up with
I dont know where the simplicity bit comes in...

OK you've had your rant. I'll explain the simplicity bit for you.
The thread was pushrods V's OHC.
No one's argueing that enormous power can made in a pushrod engine.
But this is a Commodore forum and GM is told to get it's engines to pullute less, get better economy and at the same time make more power or nobody will buy the car.
So why has the latest V6 got OHC? To get the VVT to work.
Why did Ford toss the old SOHC and go twin cam? To get the inlet/exhaust VVT separation.
That's what I'm talking about simplicity. If GM could have made a cheap twin cam pushrod engine, don't you think they would have gone that way?
My engine experience goes way back to Lanz Bulldogs and 2-stroke Commers; I love simple engine designs, but they've all gone as they could never comply to today's tough pullution standards.

 

[klaw81]

do you think Holden should keep with the recipe they know, and continue working with Pushrod V8s, or jump to a OHC?

Well it's not really up to Holden, is it? When did Holden last design an engine from scratch? All of the current engines in the current Holden line-up are based on designs done overseas as far as I know. My guess is that GM in the US will keep going down the Gen 3/4/5 "more cubes, more power" route for a few years yet, and that Holden will keep importing them because it's far cheaper and easier than designing their own...unless the US car industry has to make some big changes to combat global warming.

There is nothing fundamentally wrong with pushrod engines but they WILL die eventually, because variable cam timing will become unavoidable (along with lots of other efficiency-boosting measures) to keep up with ever-tightening emissions laws. Also, sophisticated OHC configurations can be used to eliminate other inefficiencies...BMW has done away with throttle bodies entirely in some of their new engines and are using the valves as separate throttle bodies for each cylinder!

 

[50LTRv8]

This question really has 2 parts

Does it matter what config you have to make power?

The answer is no not really, you can create huge amounts of power from reach engine config.

Engine power and power derlivery depend more on stroke length and piston diameter than if it uses an ohc or pushrods.

Should Holden continue with pushrods?
The answer is no it can't, emission laws with force companys to cut the fat and overhead cams seems to be a good way of doing this.

For example the bf ford gets a 10% saving in fuel because they fiddled with the twin cam phasing which is pretty good if you ask me

50LTRv8

 

[J_D]

I noticed in last months Wheels mag that the 6ltr Clubsport got about 12.6L/100km on their road test, not bad fuel economy for an "old" pushrod engine.

 

[vlv8vic]

Not completely what you are talking about but...

badly tuned V8, over revved engine =
(they were nasty to get out.. no valve damage!)

 

[1991_Vn2nV]

I noticed in last months Wheels mag that the 6ltr Clubsport got about 12.6L/100km on their road test, not bad fuel economy for an "old" pushrod engine.

Exactly. When a 6.0L V8 HSV that weighs 2 tonne gets better fuel economy than a 2.0L 4 cylinder Evo Lancer which weighs several hundred kilo's less....