I've been thinking....

[RC45]

I was not promoting 2 strokes as car engines - simply sayign that rapidly opening reeds and spinning discs have been around for ages and can withstand stress, heat and vibration.

And with regard to wether I woul;d like a 2 stroke Vette?

If it was a 5.7l 2 stroke V8... HELL YES!!!!! -- I remember scaring myself shitless on a friends RG500 Gamma square 4 500cc 2 stroke GP replica... almost leaving my stomach behind when mucking about on a mates RZ500V V4 500cc 2 stroke and about killing myself of an obscene 750cc Kawasaki KH triple... (that one felt like it had a hinge in the frame it was so spindly - a 1974 or 5 model I think)

And the sound of an open pipe 2 stroke 5.7l V8 would be insane...

[neilo63]

lol nice 8)

[saadie]

wow .. must of been a nice experience eh RC ?

talking abt carbon fibre ..... the main problem is it isnt completly smooth .....
the man blocks can be made with ceramics ...... why kill the valves when they work good enough .....
anywayz theres another idea .... bake the whole block with carbon fibre and add 1inch of ceramics arround it .... this will smothen everything up and weight would also be reduced ....

[Wutputt]

Originally Posted by RC45 Originally Posted by Wutputt this system is a bit more complex as the current system, something you don't want due to reliability issues and high revving situations. Then explain why the big noise about OHC being "better" than a simple push rod design? Seems that by your logic the OHC idea is not a good one

Well, a (D)OHC has les moving parts (no pushrods, and with a DOHC no rocker arms). So less complex. But of course the main reason to opt for OHC's is the lower weight of the valvetrain, so lower inertial forces and better suited for high revving.

But on the other hand a pushrod OHV system can less 'complex' than a (D)OHC for a V-engine. That's, according to me, one of the reasons (besides compactness for a V-engine and lower center of mass of the engine) why some engines still use pushrods It's just a matter of how you interpret 'complex'. Do you look at the whole system and count all the parts or do you look at the actuating mechanism?

And besides, the complexity is only one aspect on which one can judge a new system. But a main rule is still: try to do it as simple as possible. Only if the complex system has some major advantages, you can opt for it.

[RC45]

Originally Posted by Wutputt Originally Posted by RC45 Originally Posted by Wutputt this system is a bit more complex as the current system, something you don't want due to reliability issues and high revving situations. Then explain why the big noise about OHC being "better" than a simple push rod design? Seems that by your logic the OHC idea is not a good one Well, a (D)OHC has les moving parts (no pushrods, and with a DOHC no rocker arms). So less complex. But of course the main reason to opt for OHC's is the lower weight of the valvetrain, so lower inertial forces and better suited for high revving. But on the other hand a pushrod OHV system can less 'complex' than a (D)OHC for a V-engine. That's, according to me, one of the reasons (besides compactness for a V-engine and lower center of mass of the engine) why some engines still use pushrods It's just a matter of how you interpret 'complex'. Do you look at the whole system and count all the parts or do you look at the actuating mechanism? And besides, the complexity is only one aspect on which one can judge a new system. But a main rule is still: try to do it as simple as possible. Only if the complex system has some major advantages, you can opt for it.

Strangely then - why is every street OHC V8 heavier and physically larger than it's push-rod counter part?

[Sir_GT]

Originally Posted by neilo63 2 stroke anything would probably be out of the question because of emission laws. 2 stoke jet skis i know are becoming forcefully extinct for this reason. Carbon fibre uses plastic resins to bond the CF fabric mats so i dont know what kind of plastic could take XXXX dec c temps for extended period. wouldnt the resin be thermoset meaning it can only be formed once and then if heated it will just burn and give off black smoke? and CF has a low density compared to say steel so it would need to be thicker? also CF is very brittle so how can you overcome hairline cracks i see this being a problem in a minor accident where a normal engine might just dislodge off its fixings but a CF one could develop cracks? Interesting thread even if we go off topic

It is in an interesting topic. I was reading an official report done by some scientists, and they seem to point towards the "brittle issue" as something that depends more on the process towards an intended finish. Meaning that the brittle-ness can be overcome by changes in the processing, because apparently, certain Japanese CF companies are incorporating it into infrastructure to help counteract the loss of rigity and stability brought about by the height of the structure, and at the same time, developed a process to help the CF withstand earthquakes.

The thermoset topic was exactly what I was thinking. If CF has to be thermoset, can you thermoset it to a possible level that could withstand the heat brought about by the engine?

One thing I did not think about was the lack of smoothness though. The ceramic over the CF seems like an interesting approach, especially since the new developed carbon ceramic is nearly fireproof.

Also, CF's lack of density is supposedly its trump card over steel. Supposedly, you need less CF as compared to the amount of steel required to do the same job. IIRC, CF is 9 times lighter than steel, but 3 times more rigid.

[ZfrkS62]

The thermoset topic was exactly what I was thinking. If CF has to be thermoset, can you thermoset it to a possible level that could withstand the heat brought about by the engine?

the thermals are only one part of the equation though. you also need to think about how CF will transmit vibration compared to aluminum. If the CF deadens the vibration of spark knock, then your knock sensors won't pick up pinging/detonation. and not being able to control that could cause some serious problems.

Also, setting the threads for the cylinder head bolts may prove to be a problem when you take into account the heating/cooling cycles.

in the long run i think ceramics would prove to make a much better block than CF.

[Sir_GT]

Originally Posted by ZfrkS62 in the long run i think ceramics would prove to make a much better block than CF.

But aren't ceramics more prone to cracks than anything else?

[Wutputt]

Originally Posted by RC45 Originally Posted by Wutputt Well, a (D)OHC has les moving parts (no pushrods, and with a DOHC no rocker arms). So less complex. But of course the main reason to opt for OHC's is the lower weight of the valvetrain, so lower inertial forces and better suited for high revving. But on the other hand a pushrod OHV system can less 'complex' than a (D)OHC for a V-engine. That's, according to me, one of the reasons (besides compactness for a V-engine and lower center of mass of the engine) why some engines still use pushrods It's just a matter of how you interpret 'complex'. Do you look at the whole system and count all the parts or do you look at the actuating mechanism? And besides, the complexity is only one aspect on which one can judge a new system. But a main rule is still: try to do it as simple as possible. Only if the complex system has some major advantages, you can opt for it. Strangely then - why is every street OHC V8 heavier and physically larger than it's push-rod counter part?

I never said that, didn't I?

I said that the valvetrain mechanism of actuating the valves (pushrod, rocker arms, springs, etc) itself has more mass to move with a pushrod OHV, than with a (D)OHC. It's the connection between cams and valves that has most influence on of the inertial forces and thus revving capabilities. Ok the weight of the camshaft itself has also influence on the revving capabilities, but regarding a pushrod OHV this influence is minor compared to the actual actuating system.

I never said the total mass of the camshafts, rocker arms, pushrods will be less with a a (D)OHC. So a pushrod OHV system will have packaging advantages over a (D)OHC system on V-engines.



EDIT: I noticed I said in my first reply that the 'valvetrain' of an OHC would weight less than the one of a pushrod OHV. I used the wrong word. I actually meant that the actuating mechanism connecting the camshaft(s) with the valves weights less and not the whole valvetrain system.

[ZfrkS62]

Originally Posted by Sir_GT Originally Posted by ZfrkS62 in the long run i think ceramics would prove to make a much better block than CF. But aren't ceramics more prone to cracks than anything else?

pure ceramics yes, but i think that if you were to make a ceramic-alloy (much like the F1 carboceramic brake discs) you could probably over come that problem. You may have to use an Alusil cylinder sleeve, but those combined won't weigh much more than 20lbs put together for a V8.

with the main block being ceramic, you could run a leaner mixture and create more heat since ceramics make an excellent heat sink. More heat=more HP, less fuel means higher MPG.

[e46drew]

This is a 2006 c.a.r.b. compliant 996c.c. motor 2 cycle that produces 165 bhp
it is SDI (semi direct injected)

http://www.rotax.com/en/Media.Center....09.2004-2.htm

[RC45]

^^^ - excellent - simplicity at work..

[Sir_GT]

Originally Posted by ZfrkS62 Originally Posted by Sir_GT Originally Posted by ZfrkS62 in the long run i think ceramics would prove to make a much better block than CF. But aren't ceramics more prone to cracks than anything else? pure ceramics yes, but i think that if you were to make a ceramic-alloy (much like the F1 carboceramic brake discs) you could probably over come that problem. You may have to use an Alusil cylinder sleeve, but those combined won't weigh much more than 20lbs put together for a V8. with the main block being ceramic, you could run a leaner mixture and create more heat since ceramics make an excellent heat sink. More heat=more HP, less fuel means higher MPG.

Pardon my ignorance, but are carbon ceramic surfaces smooth enough for use in an engine? i.e. as you mentioned "wrapping the carbon fibre with ceramics"

This is actually pretty interesting.

[RC45]

Simply take a loom at what the motorcycle manufacturers are doing to get the scoop on the latest high tech tricks.

[ZfrkS62]

Originally Posted by Sir_GT Originally Posted by ZfrkS62 Originally Posted by Sir_GT Originally Posted by ZfrkS62 in the long run i think ceramics would prove to make a much better block than CF. But aren't ceramics more prone to cracks than anything else? pure ceramics yes, but i think that if you were to make a ceramic-alloy (much like the F1 carboceramic brake discs) you could probably over come that problem. You may have to use an Alusil cylinder sleeve, but those combined won't weigh much more than 20lbs put together for a V8. with the main block being ceramic, you could run a leaner mixture and create more heat since ceramics make an excellent heat sink. More heat=more HP, less fuel means higher MPG. Pardon my ignorance, but are carbon ceramic surfaces smooth enough for use in an engine? i.e. as you mentioned "wrapping the carbon fibre with ceramics" This is actually pretty interesting.

i think someone else mentioned wrapping the CF in ceramics..i'm not convinced that CF is suitble for engine materials other than intake pipes and maybe manifolds.

as i mentioned in my last post, you will prbably need to use an alloy cylinder sleeve to maintain the smooth surface required to keep friction down. Ceramics won't be able to handle the piston's rings constantly scraping the cylinder walls. Not to mention the risk of oil absorbing into the block due to the porusness of ceramics (forgive me if it is not porous, m knowledge of such things is not as vast as it is on regular engines) so you may still have to line the oil galleys and water jackets with metal. Even still, you will have a considerable weight reduction and heat dissipation advanage over a conventional aluminum block.

Granted at this point, this is all jackstand racing since this is all speculation. But i think a ceramic based block could prove quite useful and may be something to look into.