I used to rev the T100C engines so hard they would fry the zener diode - no tacho, just WOT all the time. But certainly more bottom end than ohc.
OHV vs OHC, difference? Benefits?
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Originally Posted By: otis24
What is the difference between the Overhead Valve and Overhead Cam engines, in layman's terms? What are the advantages/disadvantages of one over the other?
Lot's of truth and some partial truths here.
Ford hasn't built a Overhead Valve (i.e. pushrod) engine in a long time. GM still makes pushrod engines and is about to introduce another new one soon in the next generation Corvette.
Originally Posted By: asand1
In the beginning there was the L head (flat head) engine. It is still common in low end lawn mowers.
I don't think L head engines are "common" any more even in cheap lawnmowers. I don't know if Honda or Briggs and Startton make any L head engine any more. Even the Chinese knock offs are OHV or OH. Except of course for the thousands and thousands of old Briggs and Stratton engines that are still running.
Originally Posted By: Bamaro
Dont OHV engines generally produce their power at lower RPMs and the OHCs, come on at much higher RPM?
Generally yes, but then there are NASCAR pushrod V8s that run over 9000 rpm all day long (well, only one day !)
Packaging (fitting the engine in the space available) IS typically easier for a pushrod engine. Look under the hood of a new Mustang 5.0L (which is really the old 4.6L DOHC with a bunch of improvements) and compare it to an old Fox body Mustang 5.0L (302 cid).
Twin Independent Variable Cam Timing (TIVCT) can only be easily done on DOHC engine and TIVCT is very important for optimal power/economy.
What is the difference between the Overhead Valve and Overhead Cam engines, in layman's terms? What are the advantages/disadvantages of one over the other?
Lot's of truth and some partial truths here.
Ford hasn't built a Overhead Valve (i.e. pushrod) engine in a long time. GM still makes pushrod engines and is about to introduce another new one soon in the next generation Corvette.
Originally Posted By: asand1
In the beginning there was the L head (flat head) engine. It is still common in low end lawn mowers.
I don't think L head engines are "common" any more even in cheap lawnmowers. I don't know if Honda or Briggs and Startton make any L head engine any more. Even the Chinese knock offs are OHV or OH. Except of course for the thousands and thousands of old Briggs and Stratton engines that are still running.
Originally Posted By: Bamaro
Dont OHV engines generally produce their power at lower RPMs and the OHCs, come on at much higher RPM?
Generally yes, but then there are NASCAR pushrod V8s that run over 9000 rpm all day long (well, only one day !)
Packaging (fitting the engine in the space available) IS typically easier for a pushrod engine. Look under the hood of a new Mustang 5.0L (which is really the old 4.6L DOHC with a bunch of improvements) and compare it to an old Fox body Mustang 5.0L (302 cid).
Twin Independent Variable Cam Timing (TIVCT) can only be easily done on DOHC engine and TIVCT is very important for optimal power/economy.
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Originally Posted By: theoldwizard1
Originally Posted By: asand1
In the beginning there was the L head (flat head) engine. It is still common in low end lawn mowers.
I don't think L head engines are "common" any more even in cheap lawnmowers. I don't know if Honda or Briggs and Startton make any L head engine any more. Even the Chinese knock offs are OHV or OH. Except of course for the thousands and thousands of old Briggs and Stratton engines that are still running.
On the single cylinder, vertical shaft LM engines, Briggs has dropped the OHV line and gone back to the L head design... I had a '03 OHV Briggs, when it need a head gasket in '07, all the LM engines I saw at the dealer were flatheads...
Originally Posted By: asand1
In the beginning there was the L head (flat head) engine. It is still common in low end lawn mowers.
I don't think L head engines are "common" any more even in cheap lawnmowers. I don't know if Honda or Briggs and Startton make any L head engine any more. Even the Chinese knock offs are OHV or OH. Except of course for the thousands and thousands of old Briggs and Stratton engines that are still running.
On the single cylinder, vertical shaft LM engines, Briggs has dropped the OHV line and gone back to the L head design... I had a '03 OHV Briggs, when it need a head gasket in '07, all the LM engines I saw at the dealer were flatheads...
Originally Posted By: TFB1
On the single cylinder, vertical shaft LM engines, Briggs has dropped the OHV line and gone back to the L head design... I had a '03 OHV Briggs, when it need a head gasket in '07, all the LM engines I saw at the dealer were flatheads...
I dono about that. Over at http://www.briggsandstratton.com/engines/push-mower/ it's about 50/50 L head and OHV.
On the single cylinder, vertical shaft LM engines, Briggs has dropped the OHV line and gone back to the L head design... I had a '03 OHV Briggs, when it need a head gasket in '07, all the LM engines I saw at the dealer were flatheads...
I dono about that. Over at http://www.briggsandstratton.com/engines/push-mower/ it's about 50/50 L head and OHV.
I was working in a mower shop 5 years ago, sure there were ohv engines, but the majority were sidevalve, and I never saw an ohv Chinese knock off, they were all sidevalve. Of course NZ is a budget market, so your results might differ.....
What over head cam engine is not over head valved??
They are not opposed terms.
They are not opposed terms.
Originally Posted By: Blkstanger
Originally Posted By: supercity
Ohv pushrod large capacity v8 works. It makes sense. For about every other engine configuration it doesn't. Problem is large capacity v8s are not suitable for all applications
I would have to disagree with you. It worked great on both the Harleys I owned and it works great in my 4L V-6 Ranger too. I would rather have low end torque any day over a high revving OHC.
The 4.0L came in both pushrod and OHC variants. While they made pretty good low end torque, they got poor fuel economy.
The newer Ford 3.5L/3.7L V6 engines make more power and are more efficient. Adding extra ratios to the gear box (6 or more ratios is pretty much standard on all automatics these days) helps offset any loss in low end torque. Intake and exhaust manifold tuning along with twin independent variable vale timing also helps low end torque.
Originally Posted By: supercity
Ohv pushrod large capacity v8 works. It makes sense. For about every other engine configuration it doesn't. Problem is large capacity v8s are not suitable for all applications
I would have to disagree with you. It worked great on both the Harleys I owned and it works great in my 4L V-6 Ranger too. I would rather have low end torque any day over a high revving OHC.
The 4.0L came in both pushrod and OHC variants. While they made pretty good low end torque, they got poor fuel economy.
The newer Ford 3.5L/3.7L V6 engines make more power and are more efficient. Adding extra ratios to the gear box (6 or more ratios is pretty much standard on all automatics these days) helps offset any loss in low end torque. Intake and exhaust manifold tuning along with twin independent variable vale timing also helps low end torque.
For a thousand times, it has been said before: DOHC does NOT mean a lack of low end torque.
If tuned that way a DOHC motor could easily equal the torque of a comparable pushrod motor. Many already do, see Overkill's BMW M5 for example.
Comparing a 4.0 design that was very dated with a new "clean sheet of paper" design is not the best example for sure.
If tuned that way a DOHC motor could easily equal the torque of a comparable pushrod motor. Many already do, see Overkill's BMW M5 for example.
Comparing a 4.0 design that was very dated with a new "clean sheet of paper" design is not the best example for sure.
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Originally Posted By: SteveSRT8
For a thousand times, it has been said before: DOHC does NOT mean a lack of low end torque.
If tuned that way a DOHC motor could easily equal the torque of a comparable pushrod motor. Many already do, see Overkill's BMW M5 for example.
Comparing a 4.0 design that was very dated with a new "clean sheet of paper" design is not the best example for sure.
Bingo
For a thousand times, it has been said before: DOHC does NOT mean a lack of low end torque.
If tuned that way a DOHC motor could easily equal the torque of a comparable pushrod motor. Many already do, see Overkill's BMW M5 for example.
Comparing a 4.0 design that was very dated with a new "clean sheet of paper" design is not the best example for sure.
Bingo
Originally Posted By: SteveSRT8
For a thousand times, it has been said before: DOHC does NOT mean a lack of low end torque.
If tuned that way a DOHC motor could easily equal the torque of a comparable pushrod motor. Many already do, see Overkill's BMW M5 for example.
Comparing a 4.0 design that was very dated with a new "clean sheet of paper" design is not the best example for sure.
Agreed. Vvt has changed how engines perform,as well as intakes able to direct air between short and long runners,so if starting with a clean sheet as Steve points out what could a manufacturer do with today's tech.
Obviously it depends on what car it's going in. The heads on a ford 5.0 are so big that that engine wouldnt fit in a corvette and maintain the same hood line.
Application dependent is what dictates who does what with whatever tech is available.
For a thousand times, it has been said before: DOHC does NOT mean a lack of low end torque.
If tuned that way a DOHC motor could easily equal the torque of a comparable pushrod motor. Many already do, see Overkill's BMW M5 for example.
Comparing a 4.0 design that was very dated with a new "clean sheet of paper" design is not the best example for sure.
Agreed. Vvt has changed how engines perform,as well as intakes able to direct air between short and long runners,so if starting with a clean sheet as Steve points out what could a manufacturer do with today's tech.
Obviously it depends on what car it's going in. The heads on a ford 5.0 are so big that that engine wouldnt fit in a corvette and maintain the same hood line.
Application dependent is what dictates who does what with whatever tech is available.
The small-displacement OHC engines in both cars (Chevy is DOHC with dual independent VVT, Honda is SOHC with i-VTEC cam phasing) both fall flat on their faces at higher RPM's. They're not high-RPM screamers. Mid-range power is their forte, and they both have a strong midrange from about 2000-5000 RPM. I'll take that over an OHV 2.5l Iron Duke that was anemic much above 3000 RPM. Well, a 1989 Iron Duke was just an anemic engine in general, so it's hardly a fair comparison.
Given packaging concerns, I'll take OHC in a small inline engine instead of cam in block OHV. That Iron Duke was quite large for a 2.5l inline-4.
Given packaging concerns, I'll take OHC in a small inline engine instead of cam in block OHV. That Iron Duke was quite large for a 2.5l inline-4.
Yet my old Fiero with an Iron Duke based motor was a real screamer. With some inexpensive machine work it easily pulled the redline in top gear.
Oh, and the redline we used was 7200 rpm!
That's why I was trying to tell everyone that things like cam specs, head design and the like have much more effect on engine personality than cam location.
Oh, and the redline we used was 7200 rpm!
That's why I was trying to tell everyone that things like cam specs, head design and the like have much more effect on engine personality than cam location.
OHC allows for more valve area and better flow as a result, also you can do variable valve timing on individual cam shafts, and they rev higher. Downside is they are larger and can have long timing chains or belts which don't hold up as well as the short chains on OHV motors.
OHV is more compact and cheaper to manufacture. AFAIK only GM is sticking to it, but I suspect the reason for that is they are well broke and have other things to invest money in at this time.
One way to shrink OHC engines is to do a W motor like VW, but quite frankly those are packaging abortions.
OHV is more compact and cheaper to manufacture. AFAIK only GM is sticking to it, but I suspect the reason for that is they are well broke and have other things to invest money in at this time.
One way to shrink OHC engines is to do a W motor like VW, but quite frankly those are packaging abortions.
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Originally Posted By: Bamaro
Dont OHV engines generally produce their power at lower RPMs and the OHCs, come on at much higher RPM?
Nah only little screamers like the 4 cylinders that a lot of cars come with these days. They have to rev because they don't have much displacement to make up for it. An OHV 4 cylinder isn't much different in this regard.
Now a big OHC motor more so one that's boosted like a Mercedes V12 makes all its torque at I think about 1,500rpm, or right off idle.
Torque down low is really what matters unless its a track car, because your not going to be exploring a torque peak at an 8k redline going to pick up a gallon of milk...well you could but come on. Usable power in real world driving is all down low.
Dont OHV engines generally produce their power at lower RPMs and the OHCs, come on at much higher RPM?
Nah only little screamers like the 4 cylinders that a lot of cars come with these days. They have to rev because they don't have much displacement to make up for it. An OHV 4 cylinder isn't much different in this regard.
Now a big OHC motor more so one that's boosted like a Mercedes V12 makes all its torque at I think about 1,500rpm, or right off idle.
Torque down low is really what matters unless its a track car, because your not going to be exploring a torque peak at an 8k redline going to pick up a gallon of milk...well you could but come on. Usable power in real world driving is all down low.
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If you're referring to the Mighty M275 - it's a SOHC, 3-valve, twin-turbo, intercooled V-12...and max torque is at 1,800 RPM...the max torque (stock) is 590 ftlbs (800 NM)...
The feeling is much like an old, large displacement muscle car OHV V-8...only smoother...and faster...much, much faster...
The 5252 is a conversion factor. Torque x RPM = HP and the factor allows the conversion of english (non-metric) units so that the equation works...based on that relationship; the torque curve defines where peak HP happens...and that curve is influenced by bore vs. stroke, cam profile, valve and ignition timing, boost (if any), port design/flow, intake runner and exhaust design, even rod length...
The feeling is much like an old, large displacement muscle car OHV V-8...only smoother...and faster...much, much faster...
The 5252 is a conversion factor. Torque x RPM = HP and the factor allows the conversion of english (non-metric) units so that the equation works...based on that relationship; the torque curve defines where peak HP happens...and that curve is influenced by bore vs. stroke, cam profile, valve and ignition timing, boost (if any), port design/flow, intake runner and exhaust design, even rod length...
Originally Posted By: Astro14
If you're referring to the Mighty M275 - it's a SOHC, 3-valve, twin-turbo, intercooled V-12...and max torque is at 1,800 RPM...the max torque (stock) is 590 ftlbs (800 NM)...
The feeling is much like an old, large displacement muscle car OHV V-8...only smoother...and faster...much, much faster...
The 5252 is a conversion factor. Torque x RPM = HP and the factor allows the conversion of english (non-metric) units so that the equation works...based on that relationship; the torque curve defines where peak HP happens...and that curve is influenced by bore vs. stroke, cam profile, valve and ignition timing, boost (if any), port design/flow, intake runner and exhaust design, even rod length...
Yes, it's a wonderful engine.
But you boosted guys forgot to mention the most important part of any motor with positive manifold pressure, where does it start? Wastegate, turbo sizing, and even more need to be added to your list of variables, eh?
If you're referring to the Mighty M275 - it's a SOHC, 3-valve, twin-turbo, intercooled V-12...and max torque is at 1,800 RPM...the max torque (stock) is 590 ftlbs (800 NM)...
The feeling is much like an old, large displacement muscle car OHV V-8...only smoother...and faster...much, much faster...
The 5252 is a conversion factor. Torque x RPM = HP and the factor allows the conversion of english (non-metric) units so that the equation works...based on that relationship; the torque curve defines where peak HP happens...and that curve is influenced by bore vs. stroke, cam profile, valve and ignition timing, boost (if any), port design/flow, intake runner and exhaust design, even rod length...
Yes, it's a wonderful engine.
But you boosted guys forgot to mention the most important part of any motor with positive manifold pressure, where does it start? Wastegate, turbo sizing, and even more need to be added to your list of variables, eh?
Originally Posted By: SteveSRT8
But you boosted guys forgot to mention the most important part of any motor with positive manifold pressure, where does it start? Wastegate, turbo sizing, and even more need to be added to your list of variables, eh?
For my Marauder with 4.6L DOHC 32valve, it's at just above idle... Needless to say it has a abundance of low speed torque...
But you boosted guys forgot to mention the most important part of any motor with positive manifold pressure, where does it start? Wastegate, turbo sizing, and even more need to be added to your list of variables, eh?
For my Marauder with 4.6L DOHC 32valve, it's at just above idle... Needless to say it has a abundance of low speed torque...
Volkswagen's 103 hp 1.2 liter TSI has gone to 2-valve and single overhead cam to reduce friction and oil flow requirements, along with smaller main and rod bearings. The pump is immersed to reduce the capacity needed for priming. It also has an air-liquid-air intercooler, dual circuit cooling system with deactivatable coolant pump, electric waste gate and minimal valve overlap. In places where you have to pay over $100 for a tank of gas, these things make sense!
I think one of the earlier reasons why DOHC and 4-valves were adopted in mainstream cars was to get the spark plug in the center and make the combustion chamber more spherical and emissions-friendly.
I think one of the earlier reasons why DOHC and 4-valves were adopted in mainstream cars was to get the spark plug in the center and make the combustion chamber more spherical and emissions-friendly.
Originally Posted By: Astro14
If you're referring to the Mighty M275 - it's a SOHC, 3-valve, twin-turbo, intercooled V-12...and max torque is at 1,800 RPM...the max torque (stock) is 590 ftlbs (800 NM)...
The feeling is much like an old, large displacement muscle car OHV V-8...only smoother...and faster...much, much faster...
The 5252 is a conversion factor. Torque x RPM = HP and the factor allows the conversion of english (non-metric) units so that the equation works...based on that relationship; the torque curve defines where peak HP happens...and that curve is influenced by bore vs. stroke, cam profile, valve and ignition timing, boost (if any), port design/flow, intake runner and exhaust design, even rod length...
Awesome car BTW.
Yeah the power comes on really low, although I still do like the charm of the M120 which really does like to spool up!
You get an R1 kit into that motor yet and wake it up?
If you're referring to the Mighty M275 - it's a SOHC, 3-valve, twin-turbo, intercooled V-12...and max torque is at 1,800 RPM...the max torque (stock) is 590 ftlbs (800 NM)...
The feeling is much like an old, large displacement muscle car OHV V-8...only smoother...and faster...much, much faster...
The 5252 is a conversion factor. Torque x RPM = HP and the factor allows the conversion of english (non-metric) units so that the equation works...based on that relationship; the torque curve defines where peak HP happens...and that curve is influenced by bore vs. stroke, cam profile, valve and ignition timing, boost (if any), port design/flow, intake runner and exhaust design, even rod length...
Awesome car BTW.
Yeah the power comes on really low, although I still do like the charm of the M120 which really does like to spool up!
You get an R1 kit into that motor yet and wake it up?
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Honda's new 700cc streetbike has a 2 cylinder, 8 valve, overhead cam, engine with a 6800RPM redline and a torque peak WAY below that.
I rode one, and it's power is similar to a Harley in some ways. All low end, and zero top end.
Torque and RPM have nothing to do with pushrods or cam location.
I rode one, and it's power is similar to a Harley in some ways. All low end, and zero top end.
Torque and RPM have nothing to do with pushrods or cam location.
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