Can someone clear up this "myth" for me.
People talking about Hondas and Toyotas making a lot more HP than TQ need to read my previous post as well.
They have small displacement DOHC turbo motors. Their small displacement means small stroke, and the small stroke allows them to complete more cycles per minute - greater RPM's (if the piston has a shorter distance to travel, it will be able to achieve more cycles in a given amount of time).
Once again, HP = TQ x RPM / 5252
So even though they don't make as much TQ, they can achieve greater RPM's, which shows you why they can make so much more HP than TQ.
Picture it - Your HP is equal to the amount of force one cycle the engine makes, multiplied by the number of cycles the engine makes in 1 minute. The 5252 is just a constant used in converting the units between TQ and HP.
They have small displacement DOHC turbo motors. Their small displacement means small stroke, and the small stroke allows them to complete more cycles per minute - greater RPM's (if the piston has a shorter distance to travel, it will be able to achieve more cycles in a given amount of time).
Once again, HP = TQ x RPM / 5252
So even though they don't make as much TQ, they can achieve greater RPM's, which shows you why they can make so much more HP than TQ.
Picture it - Your HP is equal to the amount of force one cycle the engine makes, multiplied by the number of cycles the engine makes in 1 minute. The 5252 is just a constant used in converting the units between TQ and HP.
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
Originally Posted by Louie83
Wow, a lot of people making things harder than they need to be.
Let's take a 346 and stroke it to a 383.
HP = TQ x RPM / 5252
So keeping all other things equal, what we did was increase the stroke of the engine which will yield more TQ per stroke. Since other things were kept equal, the piston speed has not changed. It will now take that piston a little longer to move up and down the cylinder since the stroke is longer. Therefore, obviously you won't be able to achieve quite as high RPM's as before.
So we are gaining torque and losing a little bit of RPM's. Since everything else was kept the same, you are going to gain enough TQ that it will be worth losing the little bit of RPM's and overall you will gain some HP (which is what matters).
Let's take a 346 and stroke it to a 383.
HP = TQ x RPM / 5252
So keeping all other things equal, what we did was increase the stroke of the engine which will yield more TQ per stroke. Since other things were kept equal, the piston speed has not changed. It will now take that piston a little longer to move up and down the cylinder since the stroke is longer. Therefore, obviously you won't be able to achieve quite as high RPM's as before.
So we are gaining torque and losing a little bit of RPM's. Since everything else was kept the same, you are going to gain enough TQ that it will be worth losing the little bit of RPM's and overall you will gain some HP (which is what matters).
Woah! Let me understand you:
Since you have increased the stroke, the piston speed has not changed?
So...with a 3.62" stroke on a stock LS1 motor, the piston speed is the same
at 3000 RPM with a 4.0" stroke?
Gee, that's like saying a swimmer has 10 minutes to complete 10 laps in a 100 ft. length pool.
If the pool is extended by an extra 20 feet and he still has 10 minutes to complete 10 laps, does that mean he's still swimming at the same speed?
Last edited by Adrenaline_Z; Dec 7, 2006 at 03:35 PM.
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
Originally Posted by Louie83
People talking about Hondas and Toyotas making a lot more HP than TQ need to read my previous post as well.
They have small displacement DOHC turbo motors. Their small displacement means small stroke, and the small stroke allows them to complete more cycles per minute - greater RPM's (if the piston has a shorter distance to travel, it will be able to achieve more cycles in a given amount of time).
They have small displacement DOHC turbo motors. Their small displacement means small stroke, and the small stroke allows them to complete more cycles per minute - greater RPM's (if the piston has a shorter distance to travel, it will be able to achieve more cycles in a given amount of time).
So an 346 LS1 engine turning 5000 RPM has fired more power strokes than
a 382 LSx turning 5000 RPM?
Hmmmm...so if 5000 revs per minute is 5000 revs per minute... what happened
to those extra power strokes?
Last edited by Adrenaline_Z; Dec 7, 2006 at 03:37 PM.
Originally Posted by Adrenaline_Z
Woah! Let me understand you:
Since you have increased the stroke, the piston speed has not changed?
So...with a 3.62" stroke on a stock LS1 motor, the piston speed is the same
at 3000 RPM with a 4.0" stroke?
Gee, that's like saying a swimmer has 10 minutes to complete 10 laps in a 100 ft. length pool.
If the pool is extended by an extra 20 feet and he still has 10 minutes to complete 10 laps, does that mean he's still swimming at the same speed?
Since you have increased the stroke, the piston speed has not changed?
So...with a 3.62" stroke on a stock LS1 motor, the piston speed is the same
at 3000 RPM with a 4.0" stroke?
Gee, that's like saying a swimmer has 10 minutes to complete 10 laps in a 100 ft. length pool.
If the pool is extended by an extra 20 feet and he still has 10 minutes to complete 10 laps, does that mean he's still swimming at the same speed?
Originally Posted by Adrenaline_Z
Hang on.
So an 346 LS1 engine turning 5000 RPM has fired more power strokes than
a 382 LSx turning 5000 RPM?
Hmmmm...so if 5000 revs per minute is 5000 revs per minute... what happened
to those extra power strokes?
So an 346 LS1 engine turning 5000 RPM has fired more power strokes than
a 382 LSx turning 5000 RPM?
Hmmmm...so if 5000 revs per minute is 5000 revs per minute... what happened
to those extra power strokes?
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
As stroke increases, piston velocity changes (it increases) relative to crank angle...
i.e. PS increases wrt to angle even before you have scaled it for the RPM in question:
In the graph:
R is half-stroke (the radius of the circle that the center of the crank pin traces out),
L is the rod length,
Vertical units are inches (position wrt crank center), inches/radian (velocity), inches/radian² (acceleration),
Horizontal units are degrees (crank position wrt TDC).
i.e. PS increases wrt to angle even before you have scaled it for the RPM in question:
In the graph:
R is half-stroke (the radius of the circle that the center of the crank pin traces out),
L is the rod length,
Vertical units are inches (position wrt crank center), inches/radian (velocity), inches/radian² (acceleration),
Horizontal units are degrees (crank position wrt TDC).
Last edited by joecar; Dec 7, 2006 at 08:04 PM.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
454 vs 454? So with the arival of the lsx block next spring there are now two ways to get 454ci out of a lsx block. one being a 4.125x4.25(lsx1) and the other is 4.25x4.00(lsx2). Ignoring heads and cams and all other things, look just at the rotating assembly. Since for a given revolution the lsx1 would have the piston travel further would it be a safe bet to say the rings would wear out more? The lsx2 block would be over square, so wouldn't it have a higher peak efficiency since a larger bore to stroke ration means a more efficient motor? The lsx1 would have a longer stroke so it should make more low end tq but the power band wouldn't extend as high as the lsx2 block. In the piston weight of the bigger lsx2 block more of an effect than the greater crank/rod weight of the lsx1? Any other idea's you could think of. This isn't for me but It jsut got me to wondering... perhaps one is better for all out power and one is better for longevity(many miles as a DD)
Here we go again......
Sounds like this could end up being a continuation of the "clear up this myth" thread.
But if it were up to me I would build the larger bore/shorter stroke. I would like to see what the difference would be of these new L92 heads and the larger valves flowed on a 4.125 Vs 4.25 bore. Would be interesting. I wouldnt expect much of a difference, but it should show up.
Sounds like this could end up being a continuation of the "clear up this myth" thread.
But if it were up to me I would build the larger bore/shorter stroke. I would like to see what the difference would be of these new L92 heads and the larger valves flowed on a 4.125 Vs 4.25 bore. Would be interesting. I wouldnt expect much of a difference, but it should show up.
Originally Posted by mzoomora
Here we go again......
Sounds like this could end up being a continuation of the "clear up this myth" thread.
Sounds like this could end up being a continuation of the "clear up this myth" thread.
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
you know what he was trying to say
absorbed that information and took it to the bank.
There are about 3-4 people in this thread that really know what's going on,
and post their knowledge to help everyone understand...then it gets lost
in a post that totally contradicts the facts with a little ego thrown in for
good measure.
It's nothing personal, it just gets annoying after a while.
Originally Posted by joecar
As stroke increases, piston velocity changes (it increases) relative to crank angle...
Oh well, you will still lose some RPM's so it doesn't change the result.
Originally Posted by Adrenaline_Z
Hang on.
So an 346 LS1 engine turning 5000 RPM has fired more power strokes than
a 382 LSx turning 5000 RPM?
Hmmmm...so if 5000 revs per minute is 5000 revs per minute... what happened
to those extra power strokes?
So an 346 LS1 engine turning 5000 RPM has fired more power strokes than
a 382 LSx turning 5000 RPM?
Hmmmm...so if 5000 revs per minute is 5000 revs per minute... what happened
to those extra power strokes?
All I am saying is this. A smaller engine with very short stroke is capable of greater RPM's than a larger engine with a very long stroke.
I don't see how this is so hard to understand.
Look at 600cc crotch rockets. They make a lot more HP than TQ and they do it at like 14,000 RPM for this very reason.
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
I don't see how this is so hard to understand.
As for the motorcylce analogy, it seems you may have "the cart before the horse".
Does the displacement of the motor lend any hints as to why such high RPM
is required to make power?
Let's not start comparing motorcylce engines to car engines. Rotating and
reciprocating mass is much less in a motorcycle engine.
Last edited by Adrenaline_Z; Dec 8, 2006 at 12:13 PM.
Originally Posted by Louie83
Take a deep breath and relax.
All I am saying is this. A smaller engine with very short stroke is capable of greater RPM's than a larger engine with a very long stroke.
I don't see how this is so hard to understand.
Look at 600cc crotch rockets. They make a lot more HP than TQ and they do it at like 14,000 RPM for this very reason.
All I am saying is this. A smaller engine with very short stroke is capable of greater RPM's than a larger engine with a very long stroke.
I don't see how this is so hard to understand.
Look at 600cc crotch rockets. They make a lot more HP than TQ and they do it at like 14,000 RPM for this very reason.
Originally Posted by mullenh
nobody disagreed that a smaller engine should have the ability for higher rpm due to a lower rotating mass. the argument was which method was better to 'increase' displacement ; stroke or over bore.