Science Abuse Posted February 14, 2003 Report Share Posted February 14, 2003 Cuz I think I'm missing something. I'm living under the imperssion that the Horsepower per liter ratio is the measure of how much work you're making an engine do, how much stress you're putting it through. Now, somethng that I don't get. 1.3 liter, 600 hp, there's more then 1 or two or 10 out there, that's 461 hp per liter. Trouble is, things tend to break on those reputedly fragile rotaries. The slightest little fuel or timing mistake causes them to pop, even the little 300-400 hp ones. But thats still 230-300 hp/L. Now, first off, find a street driven, highway lovin' 1300-2200hp small block V8. Once you've found one, run it a little lean under boost, and tell me what happens? Same damn thing. So, why are Rotaries crap? Quote Link to comment Share on other sites More sharing options...
Guest stevil Posted February 14, 2003 Report Share Posted February 14, 2003 HP per liter isn't really how much work or stress the engine takes, more about how well it breathes. The stress relates to longevity and strength. Rotaries are a totally different thing than convetional motors, so it's tough to compare them. And you're right, an out of tune boosted engine can lead to disaster, whether it's a rotary or not. I've heard that NA rotaries last a long time, and totally bone stock turbo rotaries not lasting past 100K. Compare that to stock GNs, Supras, Cobras, and other factory boosted cars, they tend to last longer. Why aren't there any high power NA rotaries? there may be, so lemme know Quote Link to comment Share on other sites More sharing options...
20G TSi Posted February 14, 2003 Report Share Posted February 14, 2003 Originally posted by Moltar: Now, first off, find a street driven, highway lovin' 1300-2200hp small block V8. Once you've found one, run it a little lean under boost, and tell me what happens? Same damn thing. So, why are Rotaries crap? If you're going to compare, compare correctly. 1.3 = 2.6L piston motor. I ran my supercharged 302 lean for a year before I broke a compression ring and mangled the piston crown. Quote Link to comment Share on other sites More sharing options...
20G TSi Posted February 14, 2003 Report Share Posted February 14, 2003 Oh, and I'm leaning my 4G63T out to .88v / 1625F degrees - its holding up (550cc's go in today graemlins/bubbrubb.gif ) Quote Link to comment Share on other sites More sharing options...
Rotarded1647545491 Posted February 14, 2003 Report Share Posted February 14, 2003 Originally posted by Moltar: So, why are Rotaries crap? Cuz you don't have one! Quote Link to comment Share on other sites More sharing options...
Science Abuse Posted February 14, 2003 Author Report Share Posted February 14, 2003 Originally posted by Hoosier Daddy: I've heard that NA rotaries last a long time, and totally bone stock turbo rotaries not lasting past 100K. Compare that to stock GNs, Supras, Cobras, and other factory boosted cars, they tend to last longer. LOl, way to comapre apples to cast iron oranges tongue.gif I've heard of bone stock NA piston engines not lasting past 50K And, there are high power N/A rotaries out there, some aproacing 500. The way a roatry is designed, it just loves boost, it could proobably run on compressed air alone. Ok Jason, you're right, there are 2 sides firing at once. But is a 600 hp 2.6 any less impressive? tongue.gif Quote Link to comment Share on other sites More sharing options...
excell Posted February 14, 2003 Report Share Posted February 14, 2003 You would be surprised how lean you can run a SUpercharged 3800 without it going *POP*. Even heavily modded. After I got my cam, when I killed my fuel pump I was seeing O2's of .500-.600v at WOT. Good non-piston popping O2's should be .890-.910v. I ran the car wide open throttle with O2's dangerously lean for quite a few extended bursts. Why? Because I didn't know what was happening. I thought my S/C belt was slipping causing the surges in power-loss. But in reality it was my fuel pump not being able to keep up. I only found out later this was happening when I stopped and checked O2 logs. This was not on a stock 6-7lbs of boost either. I was running around 11 pounds of boost, or a 3.0" pulley. Our motors catch a lot of shit for being weak due to our Hyperutectic pistons always losing a chip under lean conditions. However this was not the case. I had my motor dangerously lean far longer than it should have with far too much boost and yet it did not blow. To add to it my motor has 111k miles too. What relevance it has to the discussion? Not sure, just tossing ideas out there. smile.gif Quote Link to comment Share on other sites More sharing options...
Mensan Posted February 14, 2003 Report Share Posted February 14, 2003 How long did chevy play with the idea of the small block V8 before they did it right? Give the rotary some time. Hell, look at Ford's 3.8L V6, it sucks ass. Poor design. The rotary is a wonderful idea, and I think theres alot to come from it. Look at the Moller skycar. If it was meant to be, they'll work the design flaws out. Quote Link to comment Share on other sites More sharing options...
Guest nevarmore Posted February 15, 2003 Report Share Posted February 15, 2003 Originally posted by Mensan: How long did chevy play with the idea of the small block V8 before they did it right? Give the rotary some time. Hell, look at Ford's 3.8L V6, it sucks ass. Poor design. The rotary is a wonderful idea, and I think theres alot to come from it. Look at the Moller skycar. If it was meant to be, they'll work the design flaws out. work the design flaws out? i think its the exact opposite, rotaries were frist used in propr aircraft, which are run under very harsh conditions. youre at full throttle with lots of load on takeoff and climb, your fuel mix needs to change as you change altitude because of pressure (ie air density) differences. rotaries have been around a lot longer than the old 350. it seesm to me that the longevity of the rotary has to do with its simplicity. in a piston engine the direction of force changes from the up and down piston to a rotation of the crank, which causes wear and power loss. a rotary on the other hand, doesnt change liek that it jsut rotates. rotaries are a lot like some old ocmputer tech, it may have been a better idea, but no one would market/buy it so it isnt too popular. imagine if rotaries were in every car and people were nutting themselves over a piston powered fbody making massvie horsepower. Quote Link to comment Share on other sites More sharing options...
slow4now Posted February 15, 2003 Report Share Posted February 15, 2003 The moving parts in a piston engine are much more robust than the parts in a rotary. The fact of the matter is a piston engine WILL survive a little detonation 9 times out of ten.In most cases if you here pinging on a rotary, you can kiss it goodbye as it's already toast. I honestly don't know much about rotaries, but I'm willing to bet that the more fragile internal parts (apex seals, coolant seals) take a much higher amount of stress than the equivalant parts on a piston motor (rings and headgaskets). I'm also pretty sure that a rotor is going to be thinner than a piston, and a rotor housing thinner than typical cylinder walls.I believe the main purpose of the rotary was to save weight. I could be tottally wrong though, this is all semi-edjucated conjecture on my part. Horsepower per liter, or specific output as it's commonly called, is a way of comparing an engines efficiency much like MPG. As already stated it has everything to do with how well a motor breathes. S2000 = 120hp per liter! Not many production naturaully aspirated motors beat that (I know the E46 M3 does, as well as at least one Ferrari...not bad company.) smile.gif Quote Link to comment Share on other sites More sharing options...
SupraGlue Posted February 16, 2003 Report Share Posted February 16, 2003 Horsepower per liter correlates to stress, but not directly. For example, a forced induction motor making let's say 600hp at the flywheel on a 400ci small block turning 5500rpm sees much less connecting rod stress and possibly less peak cylinder pressure than an NA 400ci small block making the same hp turning 7000rpm. This is why you see such fantastic numbers for turbo and s/c motors when you think the thing should be flying apart. The biggest correlator for internal stresses is RPM (Ruins People's Motors). Double your revs and the connecting rod stresses SQUARE. Of course, more power does come with more RPM in a properly designed engine, but the relationship between stresses and power is not a direct one. Of course, the rotaries have no connecting rods, so in their case as the RPMs rise, the forces they are dealing with are the inertia of the apex seals and the force of the rotor on the eccentric shaft. This is much less than what you see in a reciprocating engine, therefore the rotaries can be revved much, much higher before encountering problems. In this way, Eric's argument is a decent one. The rotary can make a very large amount of power for it's size. Where the weakness of the design lies is in detonation resistance. The apex seal functions in the same way as does a piston ring, and like a compression ring, it is exposed to the full fury of the combustion chamber. Now, the ring lands on a GOOD quality pistion will provide plenty of support area to the compression ring, even under heavy detonation. Since the piston ring is circular, this also helps spread the load encountered during detonation. The apex seal however is cantilevered off the end of the rotor, and is a simple straight piece. This makes it much more susceptible to detonation caused by tuning errors (which all detonation is caused by, like it or not). Now, I'm sure everyone knows all that or a lot of it. Why I'm mentioning it is that the rotary engine is NOT destroyed by making too much power. It is destroyed by bad tuning. It has a much finer edge and must be dealt with more cautiously than a piston engine. This is the price you pay for an otherwise elegant and robust engine design. Witness the Le Mans winning 787B to see an example of the reliability of a well-tuned rotary engine. The real question comes in -- is it an appropriate choice for the average amateur performance nut? Probably not, but in the hands of someone careful and knowledgable, it will be fine. Quote Link to comment Share on other sites More sharing options...
Avenger1647545502 Posted February 16, 2003 Report Share Posted February 16, 2003 The rotary motors used in old airplanes are not at all similar to the Wankel motors. The old rotaties had a fixed crankshaft, and the ENTIRE CRANKCASE AND CYLINDERS rotated around it. Somewhat like a radial motor, but the moving parts are reversed. Quote Link to comment Share on other sites More sharing options...
Science Abuse Posted February 16, 2003 Author Report Share Posted February 16, 2003 Originally posted by Avenger: The rotary motors used in old airplanes are not at all similar to the Wankel motors. The old rotaties had a fixed crankshaft, and the ENTIRE CRANKCASE AND CYLINDERS rotated around it. Somewhat like a radial motor, but the moving parts are reversed. true, but you got hte wrong motor. Those were used alot and for many years, but so were the traditional rotaries, AKA Doritos. YOu'll find most of the highest reving engines were developed for aircraft, or rely on parts develpoed for said planes. Quote Link to comment Share on other sites More sharing options...
Guest relvinnian Posted February 16, 2003 Report Share Posted February 16, 2003 Originally posted by Moltar: Ok Jason, you're right, there are 2 sides firing at once. But is a 600 hp 2.6 any less impressive? tongue.gif Compared with the Nissan RB26DETT which can probably match or exceed peak VE% of a 13B PP turbo. It cannot match the shape of the curve. It's gear ratios make up for this mostly. Everything else from peak power output (I know over 1000awhp c16), to RPM handling (10-12.5k), to reliability (of course), thermal efficiency, etc. 13B PP turbo, with lightning and balancing mods, upgraded bearings, seals, etc. will make power to around up to 10k with a huge 1.5 or larger A/R exhaust (a testimate to it's poor combustion dynamics) The main advantage of the rotary is it's cost. A jspec 13B-RE LONG BLOCK will run you $1800. You then have an engine who's "block", internals, intake manifold, and general infrastructure can support 9000-9500rpms in a 30 psi bridge port application. And with only the addition of around $1200 in parts and labor invested in stronger parts, clearanced rotors, electr. balanced assem., etc. (I excluded porting, because it is a DIYer task IMO smile.gif . Aftermarket is cheap, rebuild kits are cheap. Combine that with it's simplicity and it is hard to match. BTW, I'm trying to sell my RX-7. I need to pay some debts off (joe), and I want a celica all-trac. 3S-GTE/AWD = college car + speed. Also, the rotors are gears 3:1 to the eccentric shaft. So they spin a third the speed. (PS-13BPPT can make around 800rwhp-900rwhp max. On turbo alone around 850rwhp @ 45PSI. And you say doritos can't boost high ) Quote Link to comment Share on other sites More sharing options...
slow4now Posted February 16, 2003 Report Share Posted February 16, 2003 relivinnian .....where in the world have you been? smile.gif Quote Link to comment Share on other sites More sharing options...
SupraGlue Posted February 16, 2003 Report Share Posted February 16, 2003 Originally posted by bigbabyjesus: relivinnian .....where in the world have you been? smile.gif Same. smile.gif Good to see you back. Quote Link to comment Share on other sites More sharing options...
Conesmasher Posted February 17, 2003 Report Share Posted February 17, 2003 I have always thought that the rotaries have been prone to exploding due to the nature that they run so hott. But is the detonation just the following factor of the motor being to hot in the rotary. Quote Link to comment Share on other sites More sharing options...
Guest relvinnian Posted February 17, 2003 Report Share Posted February 17, 2003 They need more efficient combustion chambers, oiling systems, cooling systems, all aluminum housings/rotors. We need a 3liter (actual displacement) 4 rotor smile.gif . Hi peoples. graemlins/fruit.gifgraemlins/bubbrubb.gif Quote Link to comment Share on other sites More sharing options...
Berto Posted February 17, 2003 Report Share Posted February 17, 2003 hey brian, check the for sale section, a thread made by me, on a decen all trac...i know they are rare. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.