VVT/VVL for pushrod engines.

[HashiriyaR32]

Just putting it down, because pushrod engines with VVT do actually exist. It'd be nice if we could do this in Automation as well.

Examples:

GM's LZ4 and LZE V6's
Chrysler/Dodge Viper V10 (2nd-gen and on)


GM also experimented with pushrod engines that had two cams in the block for multivalve/VVT purposes.

[Daffyflyer]

VVT probably should be available yeah, although as its a bit of a bitch to implement on an OHV engine it might require a bit of extra research.


VVL on the other hand, unless someone can show me a cam profile switching setup for an OHV engine, I don't believe its practical

[Kev2442]

It's not quite the same, but it's still about VVT/VVL :
Didn't you say there was a problem with 5 valves/cylinder ? How is it coming ?

[oppositelock]

VVL on the other hand, unless someone can show me a cam profile switching setup for an OHV engine, I don't believe its practical

Delphi developed a 2 step OHV valve lift system a few years ago. They had a pretty good technical description on their website but it doesn't seem to be working now, I don't know if they went bankrupt or what. It looked fairly production-ready to my untrained eye, but I can't remember the exact details of how it worked.

[autofrank]

Viper has a pushrod engine?! American cars are such garbage.

[loady740]

have you looked at the horsepower and torque numbers for it ........ read all the facts before you judge dude

[T-5 Killer]

Viper has a pushrod engine?! American cars are such garbage.

HUH? Pushrod doesn't equal crap. It has its place. Look at the GM LS series of engines who have great power. Hell they are even smaller and lighter than OHC engines, thats why GM went with them instead of OHC. Compare early LS motors VS early Ford OHC Modular V-8s untill recently the OHC was down on HP.

I love my pushrod Ford Windsor V-8 motors.

[loady740]

i love my pushrod LA 318

[Daffyflyer]

Pushrod has issues, its really hard to run more than 2 valves with it, so valve area is limited, and the extra valve train mass makes it A: difficult to rev hard without breaking something and B: waste a lot of power opening the heavy valve springs needed to control all that valvetrain mass.


Where it does have an advantage is size though, OHV motors are a lot smaller - This is a good example http://www.honda-perf.net/images/tech/5 ... arison.jpg

[autofrank]

have you looked at the horsepower and torque numbers for it ........ read all the facts before you judge dude

Yes, because 640bhp from 8400cc is awesome

[Kubboz]

I'm not taking either side, because I know nothing about Viper engine, but i believe that power to capacity ratio is overrated way of rating the engine performance. I'd check power to weight ratio instead. Or power to engine dimensions.

[Killrob]

Well, you can produce 6500hp from a pushrod 8L V8 too if you want... and that IS pretty awesome. But yeah, you'd probably be able to make some more from a DOHC engine, being much larger though.

[T-5 Killer]

have you looked at the horsepower and torque numbers for it ........ read all the facts before you judge dude

Yes, because 640bhp from 8400cc is awesome

Horray for Ricer math where HP per Liter really matters.

Check up on what happens when smaller motors make lots of HP.
No area under the curve so it ends up being peaky and lacking mid and low range power. For Example Look at a dyno graph of any high HP 2JZ MK4 Supra and you will see a shit ton of lag and huge spike in power before redline. Now compare that to a Large displacement engine making the same HP.

[thereddaikon]

It's not great, but it's not horrible either. It makes a higher specific power than any of the NA LS engines. It's also worth pointing out that intentionally making a larger displacement engine allows you to run lower octane for the same power and also detune it to increase life. Just because you can have 100hp/l doesn't mean you should. The engine builder should make it clear that a high specific output motor will have a shorter life unless you over build it and then costs go up quite a bit. You can get away with this in Ferraris because of their cost, or in the Honda S2000 because it's an I4 and will always be cheap due to size. The Viper and Corvette are far cheaper than Euro exotics but are expected to have comparable power. The only way to retain reliability and keep the costs in check is to use a big ass motor. I don't want to think how much a Ferrari V8 costs to make or maintain. An LS is cheap to build and is stupid cheap to keep going, even the supercharged models. Mercedes does a very similar policy on their motors, but they aren't quite as detuned. It's actually hilarious how much extra power an AMG motor will make with just an ecu retune.

http://www.renntechmercedes.com/www/node/754

This was all intentional. When you build a car you have certain goals you wish to achieve and certain constraints you have to sit within. If you have a cost is no option approach and your engineers get to go wild then you get a ferrari. There are very few companies that get to do this though, even Porsche doesn't get to go that wild and it shows in how bulletproof their flat-6 motors are.