Multi-valve engine

[vnberlwagon]

Does anyone know why Holden hasn't released a multi-valve V8? Is the current Ford "Boss" engine better or technically advanced than Holden current engines?

 

[vztrt]

Does anyone know why Holden hasn't released a multi-valve V8? Is the current Ford "Boss" engine better or technically advanced than Holden current engines?

The Boss produces more power per capacity than the pushrod but the current holden V8's are still a quicker engine. They're also cheaper to get more power out of. But that could be because the 5.7 has been out longer than the Boss motors.

 

[MBS206]

It's just a choice they choose to make.
Multivalves effectively make the engine more expensive. You need to run OHCs usually due to the amount of push rods you'd need to run if it weren't OHC. It just isn't feasible at the moment...

To run OHCs, means that the engine mounts all have to be modified, as the engine begins to sit alot higher (hence the bulge in the BA Falcons bonnet onwards)
Then when they change to an OHC setup, they also need to fu'ck around with the suspension as the CG has been moved in the car, and so has the "pivot" point.

 

[1991_Vn2nV]

Pushrod isn't necessarily a bad thing. Its technology thats been tested and proven over many decades. Look at the new alloytec engine, in comparison to the Ecotec its technologically much more advanced, but not neccessarily a better engine. Pushrod engines don't tend to rev as high as a OHC engines, but that seems to be the problem with the new Alloytecs which get their max power at 6500rpm which means you really have to rev the guts out of them and actually redline the engine to get maximum power, unlike the pushrod engine on my VN for instance that gets max power at 4800rpm

 

[vztrt]

Pushrod isn't necessarily a bad thing. Its technology thats been tested and proven over many decades. Look at the new alloytec engine, in comparison to the Ecotec its technologically much more advanced, but not neccessarily a better engine. Pushrod engines don't tend to rev as high as a OHC engines, but that seems to be the problem with the new Alloytecs which get their max power at 6500rpm which means you really have to rev the guts out of them and actually redline the engine to get maximum power, unlike the pushrod engine on my VN for instance that gets max power at 4800rpm

OHC isn't exactly a new technology, as the first OHC engine was produced around the start of the 20th century. Pushrods if I'm not mistaken are a cheaper motor to produce also easier to engineer.

 

[vt1538]

You can still multi valve an engine with pushrods. They just need a bridge running between the valve tips.

 

[1991_Vn2nV]

OHC isn't exactly a new technology, as the first OHC engine was produced around the start of the 20th century. Pushrods if I'm not mistaken are a cheaper motor to produce also easier to engineer.

I never said OHC was a new technology. But new OHC cam engines such as the quad cam, DOHC Alloytec engine, are normally more technologically advanced than a pushrod engine.

 

[burnz]

Does anyone know why Holden hasn't released a multi-valve V8? Is the current Ford "Boss" engine better or technically advanced than Holden current engines?

is there realy a point small gains in hp
all lost on restictive intake and exhaust
some times i think it's just braging right's to sell a car

 

[vnberlwagon]

is there realy a point small gains in hp
all lost on restictive intake and exhaust
some times i think it's just braging right's to sell a car

I think you're right, after reading what other members have said it seems that all other car manufacturers are doing is using technical jargon to sell their vehicles, much the same as what Holden and Ford do when they say their cars can achieve 300kw's. What speed and rev tally has to be achieved for that 300kw's to be reached.:driving:

 

[pandaman]

You can still multi valve an engine with pushrods. They just need a bridge running between the valve tips.

True, but the valves then don't open independently, the only advantage is the extra area granted by using two smaller valves instead of one big one. Some Jap engines take advantage of the valves being independent of each other, which can easily be done with OHC technologies if memory serves. GM actually do have a 3 valve per cylinder pushrod V8, used in trucks, you've probably seen pictures and such doing the rounds, for a while there was a rumour that it would replace the gen3.

vztrt, the first OHC engine was the late 1920's I think. Still you are correct, not a new technology. First high profile application of it that I can remember is Jaguar's 6 cylinder back in the late 50's/60's/can't remember(kinda drunk), that family of engine lasted a loooooong time.

Now, the real issue, this used to be a big argument on the old fordforums, pushrod (OHV) versus OHC. Bottom line is that the two technologies are just good for different purposes. Now the following involves a lot of generalisation and inaccuracy, if anythings too dodgy, please let me know. OHC with the easier implementation of multivalve technology and larger valve area and hence higher flow rates tends to make for high power with smooth low end (especially with variable timing and lift). All the pushrod engines I've driven have been more targeted towards building a fair bit of lowend and midrange, perfect example being the current VN 5L.

There are of course exceptions on both sides. The gen3 can make incredible power, for an OHV engine, thanks to some very well thought out design in terms of gasflow. Likewise with the old 4V clevelands, massive ports gave huge flowrates and massive power, but bottom end suffered. On the other side there are OHC engines that make good torque and not much power, eg the humble ford I6 that i'm always on about. I'm focusing on domestic engines, because I know even less about foreign shite.

Eventually someone will bring up the fact that all the big HP drag cars run pushrod V8's. Thats kinda different, but still a good point. I'd then point out that ferrari/lamborghini etc. all run DOHC and haven't produced a pushrod engine for quite some time. It's all horses for courses ya see. Now, if the rest of the country would just see things my way, many arguments could be avoided.