Valve overlap

[Dantheman]

Do F1 engines have any valve overlap? There just doesnt seem to be enough room when you consider the length of stroke and the compression ratio. There only seems to be millimeters left between the top of piston and the combustion chamber, surely the valve lift must be more than that?
I would have thought F1 engines would have had quite a bit of overlap considering thier speed.

Danny.

[Carlos]

Dantheman - Welcome to the forum. These 3 articles will give you an introduction to the basics of valve overlap and camshafts of a wide variety of engine types - would you please post them to the Software,books,links...thread afterwards - it's on the front page today - that is if I haven't already

http://www.chevyhiperformance.com/techa ... ne_basics/

http://auto.howstuffworks.com/camshaft.htm

http://www.sportrider.com/tech/146_0306_art/

[Dantheman]

Hi. I understand what valve overlap is, what I'm asking is do F1 engines have valve overlap? There doesnt seem to be enough room between the top of the piston and the comustion chamber for both valves to be open when the piston is at TDC.

[Carlos]

One of my favourite subjects - intake/exhaust tract/combustion chamber/piston design - This manufacturer makes a brief mention that F1 engines - do in fact - incorporate valve lap - many books and links deal with this greneral subject - but factual data is almost non-existent - not in the domain of the general public - how do I know this as fact? Using several search engines your query reference was generally in the top 6 sightings 3 times! - Good question - Oddly few F1 engine designers or corporations seem willing to release information. They seem to have their secrets and lack generosity. Human nature - often a dissapointment

http://www.zenperformance.co.uk/p/engine-components

Reference to the company"s production of pistons and a comment on clearences - if you find the Books , link, software thread, I included a site that offers a wide variety of engineering search engines - perhaps consult the Forum Index for that thread. I started a thread on the Heron head design, partly out of consideration of the problems you mention - perhaps compression ratio/combustion chamber volume is the restricting factor.

[Dantheman]

I've seen pictures of F1 pistons and there are recesses in the top face but I cant tell whether they are to allow clearance for the valves in thier closed state or to allow them to be open when the piston is at TDC.

[zac510]

I've seen pictures of F1 pistons and there are recesses in the top face but I cant tell whether they are to allow clearance for the valves in thier closed state or to allow them to be open when the piston is at TDC.

The latter.

[checkered]

Once again, the Harley

boys seem to have some applicable information. But don't cross these people; they have an "Eat ---" feature on their web page. Seems they're not kidding either.

But I quote:

"The amount of time, expressed in crankshaft degrees, that describes the window of time between the the Inlet Cam's opening point BTDC (before top dead center) and the Exhaust Cam's closing point ATDC (after, well you get my drift...). This figure can vary between zero degrees on some stock cams to as much as 70 to 90 degrees on some race motors. In general most street engines will have 20 to 30 degrees of overlap and most performance cams will have 50 to 60 degrees of overlap. Increasing the degrees of overlap tends to move the powerband up the RPM band. Increasing the overlap can increase peak power, but only if the exhaust system is properly designed to scavenge the cylinder. Decreasing the overlap tends to boost lower rpm performance."

They also have some calculators on their pages that are fun to play with. Don't know to which extent all this applies to F1, but I surmise most of it goes. Oh, almost forgot the link ...

http://www.rbracing-rsr.com/camshaft.html

[Dantheman]

Found this pic while searching the net, thought you you lot might be interested aswell. Notice the "pimples" on the piston in the valve recesses, never seen that before.

[Ciro Pabón]

Wow. Thanx, Dantheman.

[flynfrog]

that picture only had 4 valves per hole though but the clutch looks to be like an f1 clutch

[andylaurel]

I thought i read somewhere that F1 engines can't be 5 valve?

In response to the overlap issue, for any engine to operate efficiently at high RPM, valve overlap is essential.

So you might say, that an F1 engine would need considerably more overlap than even conventional race engines.

[Steven]

that picture only had 4 valves per hole though but the clutch looks to be like an f1 clutch

True, all F1 engines have 4 valves per cylinder, as obliged by the FIA.

Anyway, I have that picture too here, it's a BMW engine from a few years ago.

[flynfrog]

that picture only had 4 valves per hole though but the clutch looks to be like an f1 clutch

True, all F1 engines have 4 valves per cylinder, as obliged by the FIA.

Anyway, I have that picture too here, it's a BMW engine from a few years ago.

did they go to 4v after the switch to v8s ?

[Carlos]

The switch to 4 valve cylinderheads evolved in the mid '60's - The Repco was the last 2 valve that won a championship, Maserati built a 3 valve in about 1967, all other engines since have been 4 valves - Yamaha flirted with a 5 valve cylinderhead - but 4 valves has been the convention - the FIA rules stipulate a 4 valve head - probalby to contain costs - many suggest that the power advantage of a 5 valve head is not that pronounced, not worth the development costs and added complexity.

[andylaurel]

a 5 valve head would be unlikely to cost a great deal more than a 4 valve head when you consider that the valves are servo actuated these days. The advantages of a five valve head are that if you reduce the size of each valve, they can be lighter and therefore accelerate/decelerate quicker. Having 3 intake valves means you can have the same valve intake area but have lighter valves.

Toyota were successful with their 20valve 4AGE's in the late nineties producing 165 BHP from a 1600cc engine at around 8000 rpm. Not bad of a passenger car engine that runs on 95 RON and has only got a CR of 11:1.

It may be worth noting that Yamaha has designed every one of Toyota's "G" heads, including the silvertop and blacktop 20 valve engines.