So who would like to run 14:1 compression and rev to 14k?
09-21-2002, 02:04 PM
#21
TECH Fanatic
Re: So who would like to run 14:1 compression and rev to 14k? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by flynbludream:
<strong>
Old SS: Why do you say that piston speed limits engine RPM? Seems to be that people around here are more concerned with floating valves at high RPM or piston slap. With this type of setup you eliminate a good portion of the frictional losses due to no camshaft and all of the valvetrain parts in the heads being gone. This means that there is basically the crankshaft, pistons and rods are the only highly stressed components in the engine. I'm not sure where you are coming from with this statement. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Dear Confused:
You hit on it; The crankshaft, pistons and rods can only take so much stress, even with exotic materials allowed in F1. Piston speed is a useful way to rate the RPM induced stress levels of the reciprocating parts of an engine.
Boring technical stuff:
Average piston speed depends only on RPM and stroke length. [ Piston speed in feet per minute = 2 x stroke (inches) x RPM / 12 ]. Generally 2750 ft/min doesn't overly stress commponents, but that's only about 4600 in an LS1. 4000 ft/min is quite high (6500 for LS1). At 7500 piston speed is about 4500 ft/min. A F1 engine at 16500 has about the same piston speed. That they are able to turn 19000 says that they have the best strength and strength/weight modern technology has to offer.
9400 rpm Winston Cup engines (with about 3.3 inch strokes) are exceeding 5000 ft/min, just about where F1 is at 18000. The are required to use flat tappet cams and pushrods, for goodness sake. They also use the absolute best (read strongest and lightest) bottom end parts they are legally allowed to use. By the way, at 9400, the pistons in a Cup engine are feeling about 5300 g's at TDC! This increases at the square of the rpm, so 7000 rpm is twice the g's as 5000 in your LS1. No wonder stock bottoms have a fairly short life when run at 7000.
Even if rollers, etc. were allowed in Cup, without bigger bores and shorter strokes, they would have major problems with another 1500 rpm.
Oh, yeah, NASCAR limits the Cup bore size to something like 4.190 or 4.200. That limits the minimum stroke to just under 3.25 inches if they want 358 cubes. I think NASCAR also has a minimum displacement of 350 or more cubes.
Conclusion:
My point is that valvetrains aren't the limiting factor in modern engines. Bottom end strength is, and piston speed is a good way to measure that.
If you have valve toss, a few hundred dollars worth of valve springs, valves, rockers, pushrods etc. should cure it. If you regularly run over your crankshaft, the cure is more costly.
Old SStroker's $.02
<strong>
Old SS: Why do you say that piston speed limits engine RPM? Seems to be that people around here are more concerned with floating valves at high RPM or piston slap. With this type of setup you eliminate a good portion of the frictional losses due to no camshaft and all of the valvetrain parts in the heads being gone. This means that there is basically the crankshaft, pistons and rods are the only highly stressed components in the engine. I'm not sure where you are coming from with this statement. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Dear Confused:
You hit on it; The crankshaft, pistons and rods can only take so much stress, even with exotic materials allowed in F1. Piston speed is a useful way to rate the RPM induced stress levels of the reciprocating parts of an engine.
Boring technical stuff:
Average piston speed depends only on RPM and stroke length. [ Piston speed in feet per minute = 2 x stroke (inches) x RPM / 12 ]. Generally 2750 ft/min doesn't overly stress commponents, but that's only about 4600 in an LS1. 4000 ft/min is quite high (6500 for LS1). At 7500 piston speed is about 4500 ft/min. A F1 engine at 16500 has about the same piston speed. That they are able to turn 19000 says that they have the best strength and strength/weight modern technology has to offer.
9400 rpm Winston Cup engines (with about 3.3 inch strokes) are exceeding 5000 ft/min, just about where F1 is at 18000. The are required to use flat tappet cams and pushrods, for goodness sake. They also use the absolute best (read strongest and lightest) bottom end parts they are legally allowed to use. By the way, at 9400, the pistons in a Cup engine are feeling about 5300 g's at TDC! This increases at the square of the rpm, so 7000 rpm is twice the g's as 5000 in your LS1. No wonder stock bottoms have a fairly short life when run at 7000.
Even if rollers, etc. were allowed in Cup, without bigger bores and shorter strokes, they would have major problems with another 1500 rpm.
Oh, yeah, NASCAR limits the Cup bore size to something like 4.190 or 4.200. That limits the minimum stroke to just under 3.25 inches if they want 358 cubes. I think NASCAR also has a minimum displacement of 350 or more cubes.
Conclusion:
My point is that valvetrains aren't the limiting factor in modern engines. Bottom end strength is, and piston speed is a good way to measure that.
If you have valve toss, a few hundred dollars worth of valve springs, valves, rockers, pushrods etc. should cure it. If you regularly run over your crankshaft, the cure is more costly.
Old SStroker's $.02
09-22-2002, 04:00 PM
#22
Launching!
iTrader: (1)
Join Date: Aug 2002
Location: IL
Posts: 298
Likes: 0
Received 0 Likes
on
0 Posts
Re: So who would like to run 14:1 compression and rev to 14k? I inquired about this engine several years ago, and the price was astronomical. I think like 30K for a Small Block Ford complete engine. They sent me the full info packet. Interesting read, but very expensive. Also the lack of cooling for the heads and tremendous RPM potential seem contradictory.
I too think the next great innovation in valvetrain technology will come in the form of electromagnetic valve actuation. With this, the valves can be timed and cyls fired such that no starter is needed. The articles I read indicated the noise and required magnet size were among the main obstacles to production. I think the big guys will get on board if they can save $$. No cam, no starter. Also it will be more fuel efficient due to the vast reduction of valvetrain friction.
i guess time will tell.
I too think the next great innovation in valvetrain technology will come in the form of electromagnetic valve actuation. With this, the valves can be timed and cyls fired such that no starter is needed. The articles I read indicated the noise and required magnet size were among the main obstacles to production. I think the big guys will get on board if they can save $$. No cam, no starter. Also it will be more fuel efficient due to the vast reduction of valvetrain friction.
i guess time will tell.
01-23-2003, 07:50 PM
#23
TECH Fanatic
Join Date: Nov 2002
Location: metro st louis
Posts: 1,317
Likes: 0
Received 0 Likes
on
0 Posts
Re: So who would like to run 14:1 compression and rev to 14k? I agree with Old SStroker. Bottom end is a problem, BUT the cam is a limiting factor as well. There has been research into servo's opening and closing the valves. Imagine being able to download a new cam program in 30 minutes! No more powerband issues. I personally think eliminating the camshaft is the next big step in racing. The prob is doing it cheap and making it reliable.
P.S. BMW last year spun their F1 mill to 19,500 rpms. I couldn't even imagine the material they use in those bottom ends. We won't see that technology in our cars for a decade, if at all.
P.S. BMW last year spun their F1 mill to 19,500 rpms. I couldn't even imagine the material they use in those bottom ends. We won't see that technology in our cars for a decade, if at all.
01-25-2003, 12:44 AM
#24
Teching In
Join Date: May 2002
Location: NorCal
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Re: So who would like to run 14:1 compression and rev to 14k? I agree that the Coates is old news.
however, I feel that the future valvetrain is going to be the new BMW V8 setup. They actually do NOT use throttle bodies, and simply rely on variable cam timing and lift to determine how much power to produce.
Very interesting concept, and if it is proven reliable, is the near future of the internal combustion engine.
-Brad
PS - Because NASCAR is limited to flat tappet cams and pushrods, they actually profile the cams to produce maximum power WITH valve bounce.
however, I feel that the future valvetrain is going to be the new BMW V8 setup. They actually do NOT use throttle bodies, and simply rely on variable cam timing and lift to determine how much power to produce.
Very interesting concept, and if it is proven reliable, is the near future of the internal combustion engine.
-Brad
PS - Because NASCAR is limited to flat tappet cams and pushrods, they actually profile the cams to produce maximum power WITH valve bounce.
01-26-2003, 10:01 AM
#25
TECH Fanatic
Re: So who would like to run 14:1 compression and rev to 14k? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by BRacing:
<strong> I agree that the Coates is old news.
however, I feel that the future valvetrain is going to be the new BMW V8 setup. They actually do NOT use throttle bodies, and simply rely on variable cam timing and lift to determine how much power to produce.
Very interesting concept, and if it is proven reliable, is the near future of the internal combustion engine.
-Brad
PS - Because NASCAR is limited to flat tappet cams and pushrods, they actually profile the cams to produce maximum power WITH valve bounce. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The BMW Valvetronic system is neat.
http://www.bmwworld.com/technology/valvetronic.htm
My take on NASCAR valve "bounce" is that the closing ramp is so steep and the valve is set down onto the seat quite hard, so some seat bounce is tolerated to get the lift in the available duration and the overall hp gain is positive. Perhaps this is mainly used with restricted engines.
<strong> I agree that the Coates is old news.
however, I feel that the future valvetrain is going to be the new BMW V8 setup. They actually do NOT use throttle bodies, and simply rely on variable cam timing and lift to determine how much power to produce.
Very interesting concept, and if it is proven reliable, is the near future of the internal combustion engine.
-Brad
PS - Because NASCAR is limited to flat tappet cams and pushrods, they actually profile the cams to produce maximum power WITH valve bounce. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The BMW Valvetronic system is neat.
http://www.bmwworld.com/technology/valvetronic.htm
My take on NASCAR valve "bounce" is that the closing ramp is so steep and the valve is set down onto the seat quite hard, so some seat bounce is tolerated to get the lift in the available duration and the overall hp gain is positive. Perhaps this is mainly used with restricted engines.
