With only a little 2&3/4 stroke and the factory red line at 6500. Assuming the engine is strong enough to deal with it, what would be required to increase operating RPM to 10,000 or higher?
Would a 10% increase in intake/exhaust flow achieve that?20%-30%? Camshaft operating parameters? Higher lift, longer duration?
Valve control is king.
Valvetrain control and oiling are typically the 2 biggest issues with significantly increasing RPM (beyond basic mechanical durability). What it would take to make power up there is a secondary concern, particularly if you expect to spend more than a couple seconds at a time at those RPMs.
In reply to rslifkin :
The factory tested it stock to 8300 rpm before any sign of valve float for 3 hours.
There are lighter and bigger) valves and titanium retainers available off the shelf. Isky sells valve springs that are stiffer ( and cost less than stock) but Formula 1 ( Cosworth) valves springs are available for about what the dealerships sells them for
Assuming that works. What camshaft specs are called for as well and flow numbers or percentages? Timing?
At 24 hours LeMans 8500 RPM was used with that lousy French pump gas (85 octane?)
Remember that the forces applied as you increase speed are squared. It may have been tested for hours at 8300 rpm, but that doesn't mean 10,000 is a linear change in force. You're not adding 20% more stress to the reciprocating assembly and valvetrain. You're adding exponentially more.
At those revs you also have to consider block material and construction. If you do that to an engine designed from the ground up to spin to 10k and can take the vibes, great. Some blocks are not up to handling the harmonics. Think of it like an opera singer hitting that high-F-sharp and the wine glass breaks. It's quite possible the block in question can take the vibes, just something to consider.
Without knowing more details (although I would guess we're talking about something that starts with the letter "Jag" and ends with the letter "12"), I would say that dry sump oiling would be almost a necessity. That's the only way I can imagine getting enough oil volume without whipping it into foam. Not sure if you can find heads that will flow enough to get you there, or at least not make much power up there. Cam duration will be immense to the point where it would likely idle at 2000 RPM and not make much torque until 7000, meaning it would likely need to be paired with an ultralight vehicle and/or unobtainium gear ratios. When you shift power up, the torque peak goes up as well, so the torque production should be matched to the vehicle's weight, gears, intended use (street/race). Just know that you'll be building a strictly race engine that can't exist anywhere but on a track. I'm guessing that is already the case and that you already know that, just mentioning it. There are plenty of 10k engines on the street, but they are in crotch rocket bikes that weigh 600 lbs with the rider and have a 25:1 first gear final drive ratio.
You'll need a dedicated transmission that can take the revs. Many of the OEM offerings are not engineered to take those RPMs and could lose their guts in a leg-amputating fashion.
TL;DR... it takes about [insert incredibly large dollar figure] in parts and a truckload of engineering; valvetrain, oiling, intake flow, making sure the block and transmission don't give up the ghost, and that doesn't even take into consideration tuning the fuel curve - carb or EFI.
Which is why I'm happy to be part of GRM because you'll probably find a way to do it for $2000.
Boost.
RPMs cost cubic dollars. At some point you cross a line the engine can't mechanically handle. The piston speed and acceleration pulls things apart assuming the valves haven't already gone flying.
There is a reason they slap a turbocharger on everything. Most engines will handle more torque and torque = power.
I agree on the boost thing. Getting to a HP goal is almost always easier on the internals with boost than RPM. Corky Bell does a better job of explaining it mathematically, but it has to do with BMEP and when the peak pressures occur in the cylinder.
Getting a HP goal with RPM means unavoidably altering the torque curve potentially outside a realm of logical powerband for the application. If you're just looking for RPM for a power goal or for the uniqueness of it (a perfectly valid goal, IMO), one just needs to accept the negatives that come with it.
Trust me... if you're building a V12 for 10k RPMs, I will buy you a good microphone so you can send me a recording. :)
Curtis73 (Forum Supporter) said:Remember that the forces applied as you increase speed are squared. It may have been tested for hours at 8300 rpm, but that doesn't mean 10,000 is a linear change in force. You're not adding 20% more stress to the reciprocating assembly and valvetrain. You're adding exponentially more.
At those revs you also have to consider block material and construction. If you do that to an engine designed from the ground up to spin to 10k and can take the vibes, great. Some blocks are not up to handling the harmonics. Think of it like an opera singer hitting that high-F-sharp and the wine glass breaks. It's quite possible the block in question can take the vibes, just something to consider.
Without knowing more details (although I would guess we're talking about something that starts with the letter "Jag" and ends with the letter "12"), I would say that dry sump oiling would be almost a necessity. That's the only way I can imagine getting enough oil volume without whipping it into foam. Not sure if you can find heads that will flow enough to get you there, or at least not make much power up there. Cam duration will be immense to the point where it would likely idle at 2000 RPM and not make much torque until 7000, meaning it would likely need to be paired with an ultralight vehicle and/or unobtainium gear ratios. When you shift power up, the torque peak goes up as well, so the torque production should be matched to the vehicle's weight, gears, intended use (street/race). Just know that you'll be building a strictly race engine that can't exist anywhere but on a track. I'm guessing that is already the case and that you already know that, just mentioning it. There are plenty of 10k engines on the street, but they are in crotch rocket bikes that weigh 600 lbs with the rider and have a 25:1 first gear final drive ratio.
You'll need a dedicated transmission that can take the revs. Many of the OEM offerings are not engineered to take those RPMs and could lose their guts in a leg-amputating fashion.
TL;DR... it takes about [insert incredibly large dollar figure] in parts and a truckload of engineering; valvetrain, oiling, intake flow, making sure the block and transmission don't give up the ghost, and that doesn't even take into consideration tuning the fuel curve - carb or EFI.
Which is why I'm happy to be part of GRM because you'll probably find a way to do it for $2000.
Those parts I'm not worried about. nor is 10,000 rpm the holy grail. If I want to play with the big boys I need to get more power. Power I can't figure out how to get in any affordable way otherwise .
Transmission wise I've got sitting on the shelf a Seinz that can safely deal with whatever I throw at it. And it has gears that can be changed in minutes like a quick change rear end. Slide the old gears out. Slide new ones in and you've just changed ratios. So staying on top of the cam won't be a problem. The aluminum flywheel is only 7&1/4 inches with triple disks.
Finally it won't work on my XJS. Too heavy, too bulky.
4piston.com and enough money
Toyman! said:Boost.
RPMs cost cubic dollars. At some point you cross a line the engine can't mechanically handle. The piston speed and acceleration pulls things apart assuming the valves haven't already gone flying.
There is a reason they slap a turbocharger on everything. Most engines will handle more torque and torque = power.
" At some point."
Since you don't have the parts in front of you, you can't conceive how well they are made. Plus with a short stroke (2.75) piston speed even at insane RPM is not fast enough to be a problem. I realize that common engines with 3-4 inch strokes can generate mega tons of force starting and stopping those pistons. The reason NASCAR engines are 100% specially made racing parts.
The engine I'm talking about are Shockingly cheap. Plus I've already got several. So if I make a mistake and it goes bang. I find out what failed, sweep the pieces up and grab the next one in line.
The Turbo is the best, cheap answer for power but sadly not allowed.
Paul_VR6 (Forum Supporter) said:4piston.com and money.
I know these pieces are massively overbuilt. Running at 8000 rpm could be done with stock parts. Perhaps to be safe I should use forged pistons although with only a 2.75 stroke it's still inside safety for the stock pistons.
If you couldn't use boost, What affordable approach would you use? Back in the 80's they were getting 800+ horsepower out of the engine for 24 hours using cheap French pump gas (85 octane) I'm not limited to that. I can use E85
Porting is just time. The heads I've cut apart allow me to remove over .030 on the walls of the ports before I even approach getting too thin. (.125) In some spots almost .100 can be removed. There is a free site on the web that has a JPG of porting of the race winning heads. So do I go as big as possible? When I tried that approach on my XKE I was disappointed the size went up by over 20% but power barely hit 10%. I now know It was wrong not to bell mouth behind the seat.
Plus 2 dozen of the intake manifold used were recently recast. They even look better candidates for racing than the stock ones.
I know Group 44 never used more than .500 lift, I think .460 max. I don't know TWR. Or Lister.
The heads need to flow. I watched an episode of Engine Masters compairing 3rd generation Hemis. The early heads flowed 260 cfm on the intake. The late model heads flowed 330 cfm. They wereable to take advantage of that with a bigger cam that rasied the peak power. The two engine's profiles mimiced each other, except the late engine had about 100hp advantage untill the early engine peaked, and tge late engine ran away with the numbers.
The reason everyone says forced induction is because it can overcome crappy heads.
Use an Rx-8 stationary gears & eccentric shaft, get the rotors lightened, and some portwork. Don't forget to underdrive the water pump and alternator and you should be good for easily 12k.
Oh, wait.... You want up and down, not round and round :P
WonkoTheSane said:Use an Rx-8 stationary gears & eccentric shaft, get the rotors lightened, and some portwork. Don't forget to underdrive the water pump and alternator and you should be good for easily 12k.
Oh, wait.... You want up and down, not round and round :P
I've been out of the rotary game for many years (and didn't know that much when I was in it). Is a 12k RPM rotary really a thing? If so-what kind of thing? A drag racing thing, endurance thing, street thing? Oh-and of course, how much power?
This thread reminded me of what my engin builder mentor told me. It was that every engine can rev to 10k once.
frenchyd said:Toyman! said:Boost.
RPMs cost cubic dollars. At some point you cross a line the engine can't mechanically handle. The piston speed and acceleration pulls things apart assuming the valves haven't already gone flying.
There is a reason they slap a turbocharger on everything. Most engines will handle more torque and torque = power.
" At some point."
Since you don't have the parts in front of you, you can't conceive how well they are made. Plus with a short stroke (2.75) piston speed even at insane RPM is not fast enough to be a problem. I realize that common engines with 3-4 inch strokes can generate mega tons of force starting and stopping those pistons. The reason NASCAR engines are 100% specially made racing parts.
The engine I'm talking about are Shockingly cheap. Plus I've already got several. So if I make a mistake and it goes bang. I find out what failed, sweep the pieces up and grab the next one in line.
The Turbo is the best, cheap answer for power but sadly not allowed.
Forged pistons give up at about 5000 fpm. With your short stroke, 10k RPMs get you about 4500 fpm. That's under the threshold assuming your pistons are forged. Cast can't take that much speed.
Now you have to get the weight out of the valvetrain to keep them from floating. That's going to require some expensive bits.
I'm with Curtis. Build it and make a video. I, for one, would love to see it.
MrJoshua said:WonkoTheSane said:Use an Rx-8 stationary gears & eccentric shaft, get the rotors lightened, and some portwork. Don't forget to underdrive the water pump and alternator and you should be good for easily 12k.
Oh, wait.... You want up and down, not round and round :P
I've been out of the rotary game for many years (and didn't know that much when I was in it). Is a 12k RPM rotary really a thing? If so-what kind of thing? A drag racing thing, endurance thing, street thing? Oh-and of course, how much power?
I don't know about the RX8 engines, but the eccentric shaft in the 12a engines would start to flex at around 8500. Then the pointy rotor bits would hit the housing bits and everything would stop. At 8000 a 12a sounds like you are gutting one of the hounds of hell. It's glorious.
Appleseed said:The heads need to flow. I watched an episode of Engine Masters compairing 3rd generation Hemis. The early heads flowed 260 cfm on the intake. The late model heads flowed 330 cfm. They wereable to take advantage of that with a bigger cam that rasied the peak power. The two engine's profiles mimiced each other, except the late engine had about 100hp advantage untill the early engine peaked, and tge late engine ran away with the numbers.
The reason everyone says forced induction is because it can overcome crappy heads.
Thanks for that, if you look though the RPM range stayed roughly the same. I'm looking to go from 6500-10,000 or there abouts.
however I tried opening up the heads but careful enlargement of ports by 20% barely moved the power needle. I thought OK hand porting doesn't work so I'll open them up on my vertical mill. Then carefully flowed each port until they were uniform. The flow bench confirmed the uniformity and increase.
Nearly identical results. Now I'm working with smaller cylinders ( only 27 cubic inches per cylinder) but percentage wise I'm flowing up in the LS territory. 40 cu in cylinders.
Reading the various articles and spending an inordinate amount of time studying flow. I understand there is some added flow to be gained with a different approach to the bowl behind the valve seat. While real and understandable. We aren't making earth shattering changes.
MrJoshua said:WonkoTheSane said:Use an Rx-8 stationary gears & eccentric shaft, get the rotors lightened, and some portwork. Don't forget to underdrive the water pump and alternator and you should be good for easily 12k.
Oh, wait.... You want up and down, not round and round :P
I've been out of the rotary game for many years (and didn't know that much when I was in it). Is a 12k RPM rotary really a thing? If so-what kind of thing? A drag racing thing, endurance thing, street thing? Oh-and of course, how much power?
Sort of
dean1484 said:This thread reminded me of what my engin builder mentor told me. It was that every engine can rev to 10k once.
Easiest to do on a downshift.
Toyman! said:frenchyd said:Toyman! said:Boost.
RPMs cost cubic dollars. At some point you cross a line the engine can't mechanically handle. The piston speed and acceleration pulls things apart assuming the valves haven't already gone flying.
There is a reason they slap a turbocharger on everything. Most engines will handle more torque and torque = power.
" At some point."
Since you don't have the parts in front of you, you can't conceive how well they are made. Plus with a short stroke (2.75) piston speed even at insane RPM is not fast enough to be a problem. I realize that common engines with 3-4 inch strokes can generate mega tons of force starting and stopping those pistons. The reason NASCAR engines are 100% specially made racing parts.
The engine I'm talking about are Shockingly cheap. Plus I've already got several. So if I make a mistake and it goes bang. I find out what failed, sweep the pieces up and grab the next one in line.
The Turbo is the best, cheap answer for power but sadly not allowed.Forged pistons give up at about 5000 fpm. With your short stroke, 10k RPMs get you about 4500 fpm. That's under the threshold assuming your pistons are forged. Cast can't take that much speed.
Now you have to get the weight out of the valvetrain to keep them from floating. That's going to require some expensive bits.
I'm with Curtis. Build it and make a video. I, for one, would love to see it.
The factory tested the valve train to 8300 before anything started to float. There are lighter, bigger, better flowing valves available for a reasonable price and the valve spring size is the same as Cosworth Formula 1 ( plus those cost about what the dealers charge for stock springs).
In reply to frenchyd :
I'd expect that test was done with a stock cam. As you make the cam more aggressive, keeping the valvetrain happy will get a bit harder. In general, appropriately stiff valve springs and lightening the valvetrain anywhere you can is the answer.
My other big question would be at what RPM does the oiling system start to become a problem and need major mods. If nobody has tried to spin one that high before, you'll be a bit on your own to figure that out unfortunately and there's a definite risk of blowing something up in the process.
Toyman! said:MrJoshua said:WonkoTheSane said:Use an Rx-8 stationary gears & eccentric shaft, get the rotors lightened, and some portwork. Don't forget to underdrive the water pump and alternator and you should be good for easily 12k.
Oh, wait.... You want up and down, not round and round :P
I've been out of the rotary game for many years (and didn't know that much when I was in it). Is a 12k RPM rotary really a thing? If so-what kind of thing? A drag racing thing, endurance thing, street thing? Oh-and of course, how much power?
I don't know about the RX8 engines, but the eccentric shaft in the 12a engines would start to flex at around 8500. Then the pointy rotor bits would hit the housing bits and everything would stop. At 8000 a 12a sounds like you are gutting one of the hounds of hell. It's glorious.
Yeah, the real trick at the heart of it is the Renesis stationary gears. They're a lot harder from the factory than even the older aftermarket hardened stationary gears for the 13Bs. The 12A stat gears were the softest of the production engines, I believe, allowing the most distortion. The Renesis eshaft is better than the 12A ones, but I don't know that it's objectively better than, say, the REW ones... But it's easier to get a matched set if you're going to upgrade the stat gears anyway. Of course you need to lighten the load if you're going to live up at those RPMs, so lighten up the rotors, the Rx-8 ones are already scalloped from the factory, so might as well start with them too.
MrJoshua - According to what I've read, the stock Rensis is internally balanced well enough for 11k already, but you have to underdrive all of the OEM accessories, and the side port exhaust really limits how functional it is above 10k, even with porting...
So to build the rest of the package, get the 13B side plates and housings. Then you start porting.
My understanding is that you can keep them alive for club racing and such in the 9-11k range. Drag cars, well, those guys are nuts... They'll go full on peripheral port and spin it to 12-14k running ethanol or other crazy fuels. Of course, you have to idle at 2k, but, ya know.
Toyman! said:frenchyd said:Toyman! said:Boost.
RPMs cost cubic dollars. At some point you cross a line the engine can't mechanically handle. The piston speed and acceleration pulls things apart assuming the valves haven't already gone flying.
There is a reason they slap a turbocharger on everything. Most engines will handle more torque and torque = power.
" At some point."
Since you don't have the parts in front of you, you can't conceive how well they are made. Plus with a short stroke (2.75) piston speed even at insane RPM is not fast enough to be a problem. I realize that common engines with 3-4 inch strokes can generate mega tons of force starting and stopping those pistons. The reason NASCAR engines are 100% specially made racing parts.
The engine I'm talking about are Shockingly cheap. Plus I've already got several. So if I make a mistake and it goes bang. I find out what failed, sweep the pieces up and grab the next one in line.
The Turbo is the best, cheap answer for power but sadly not allowed.Forged pistons give up at about 5000 fpm. With your short stroke, 10k RPMs get you about 4500 fpm. That's under the threshold assuming your pistons are forged. Cast can't take that much speed.
Now you have to get the weight out of the valvetrain to keep them from floating. That's going to require some expensive bits.
I'm with Curtis. Build it and make a video. I, for one, would love to see it.
Since the factory ran the engine at 8300 rpm for 3 hours using stock parts. Maybe that should be my starting point?
Let's assume the engine will blow up at 8500 rpm.
To have the engine survive at any RPM under road racing conditions. I know a dry sump is called for. Cams will be required to make power because the stock cams start falling off at 5500 but with only a .375 lift at the valve and duration more in tune with mileage than power, that is straight forward to solve.
Increase flow through the ports? OK. How much ?
what's next?
Or just put an LS-based truck motor and call it a day.
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