FD Turbo'd Rotary Engine: CCP, the central challenge
02-11-09, 09:22 AM
#1
Racing Rotary Since 1983
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FD Turbo'd Rotary Engine: CCP, the central challenge
being in high school in the 50's was absolute heaven for a car guy. all of a sudden the 55 chevy Power Pack burst onto the scene. overhead valve engine. solid lifter Duntov cam, two four barrel carbs, 7000 RPM in a world of flatheads and black sedans. chartreuse and white! wow.
and the big story?
one hp per cubic inch!
guess what, things haven't changed all that much for the normally aspirated piston engine.
the 2009 Corvette LS7 ZO6 motor is:
hand built by Chev.
has:
titanium valves and rods
6 bolt main bearing caps
dry sump lubrication system
and every bit of engineering Chev could throw at it.
and it makes 1.18 horsepower per cubic inch!
the 2009 Dodge Viper SRT10 makes 1.17 hp per cu inch.
both 2 valve motors. 4 valve motors make 27% more hp & torque...
more air makes more ponies.
the 2009 4 valve Lambo Murcielago ($440K) makes 1.59 hp per cu inch
o k let's add more air...
enter the 2009 Corvette ZR1
supercharged and approx 40 K more than the ZO6... 1.69 hp per cu inch.
how about a 4 valve twin turbo 2009 AMG Merc SL65 AMG?
1.81 hp per cu inch.
each of the above mega price/mega hp offerings could have been tuned up for more hp but the manufacturer made a decision as to where to say NO to more power with a consideration to engine reliability.
normally aspirated piston engines:
it looks like the balance point is around 1.18 hp per cubic inch.
forced induction:
around 1.75 hp per cu inch. (the 27% differntial between 2 valve and 4 valve is in-operative on force fed motors for obvious reasons.)
so what does all this have to do w understanding our turbo'd FDs?
simple: 255 flywheel hp divided by 159 cubic inches equals 1.6 hp per cubic inch!
our engines are right there w AMG's 2009 twin turbo Mercedes tuner option that sells for $440,000. don't even bother asking what Merc/AMG did w the internals to make the motor live... cubic dollars.
we need to re-think how we understand our motors...
so stock is 1.6 hp/cu inch.
stock? not many of those around. you have ditched the heat retaining precat at minimum and are probably seeing a bit more boost... say 13-14 psi. and are making 300 rwhp.
that'd be 2.26 hp per cubic inch!
more likely you run a mid sized single... and wishing to be a tad "conservative" are making
375 rwhp... that's 2.71 hp per cubic inch!
maybe you really want to rip and are running 17 psi and making 470 rwhp... about the limit on pump gas before kaboom...
that's an astounding 3.39 hp per cubic inch!
a full 87% more than the AMG twin turbo 4 valve!
double the supercharged $116,000 ZR1!
and now it is time to meet CCP.
Combustion Chamber Pressure.
torque is a direct product of CCP and when related to RPM determines HP.
CCP correlates directly to heat.
since we are making more torque/hp per cubic inch we are creating more CCP and therefore HEAT.
simply stated the FD engine is alot more toward the race side of the continuum than we think. our motors are at the edge of current state of the art tune and when we add a few mods we are much further than we suspect along the high CCP state.
gasoline, any gasoline including racegas, auto-ignites at a mere 495 F. as we raise hp levels we are moving closer to auto ignition/knock/breaking apex seals. especially when our motors are over-carboned up w a combo of the external oil pump injecting the wrong kind of oil to lube our apex seals and the factory's fuel settings... (overly rich to cool the CCP). carbon deposits are irregular and often form small spikes which can glow and ignite fuel prematurely.
so there is no mystery as to why we incur engine failure. it isn't because it is a rotary per se. it is because it is a small displacement (159 cu inches or 2.6 liters) engine that is being pumped up w turbo'd air and it is really easy to turn up the boost for even higher output levels.
yes, the apex seal is a bit more fragile than a piston ring.
so that's the deal. sounds scary. but there is a fix and if properly applied the heat generated w the high CCP can be completely offset.
you can then have it all.
please see my thread in the 3rd Gen section for the FIX. since the thread is now over 200 posts, and i have edited out over 140, please DO read post one...
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/making-case-rotary-powered-fd-fix-806104/
BTW, just so as to avert any mushroom shaped clouds here, i am not knocking the other engines but using them to make the relative point re the rotary. run whatever you wish.
howard coleman
and the big story?
one hp per cubic inch!
guess what, things haven't changed all that much for the normally aspirated piston engine.
the 2009 Corvette LS7 ZO6 motor is:
hand built by Chev.
has:
titanium valves and rods
6 bolt main bearing caps
dry sump lubrication system
and every bit of engineering Chev could throw at it.
and it makes 1.18 horsepower per cubic inch!
the 2009 Dodge Viper SRT10 makes 1.17 hp per cu inch.
both 2 valve motors. 4 valve motors make 27% more hp & torque...
more air makes more ponies.
the 2009 4 valve Lambo Murcielago ($440K) makes 1.59 hp per cu inch
o k let's add more air...
enter the 2009 Corvette ZR1
supercharged and approx 40 K more than the ZO6... 1.69 hp per cu inch.
how about a 4 valve twin turbo 2009 AMG Merc SL65 AMG?
1.81 hp per cu inch.
each of the above mega price/mega hp offerings could have been tuned up for more hp but the manufacturer made a decision as to where to say NO to more power with a consideration to engine reliability.
normally aspirated piston engines:
it looks like the balance point is around 1.18 hp per cubic inch.
forced induction:
around 1.75 hp per cu inch. (the 27% differntial between 2 valve and 4 valve is in-operative on force fed motors for obvious reasons.)
so what does all this have to do w understanding our turbo'd FDs?
simple: 255 flywheel hp divided by 159 cubic inches equals 1.6 hp per cubic inch!
our engines are right there w AMG's 2009 twin turbo Mercedes tuner option that sells for $440,000. don't even bother asking what Merc/AMG did w the internals to make the motor live... cubic dollars.
we need to re-think how we understand our motors...
so stock is 1.6 hp/cu inch.
stock? not many of those around. you have ditched the heat retaining precat at minimum and are probably seeing a bit more boost... say 13-14 psi. and are making 300 rwhp.
that'd be 2.26 hp per cubic inch!
more likely you run a mid sized single... and wishing to be a tad "conservative" are making
375 rwhp... that's 2.71 hp per cubic inch!
maybe you really want to rip and are running 17 psi and making 470 rwhp... about the limit on pump gas before kaboom...
that's an astounding 3.39 hp per cubic inch!
a full 87% more than the AMG twin turbo 4 valve!
double the supercharged $116,000 ZR1!
and now it is time to meet CCP.
Combustion Chamber Pressure.
torque is a direct product of CCP and when related to RPM determines HP.
CCP correlates directly to heat.
since we are making more torque/hp per cubic inch we are creating more CCP and therefore HEAT.
simply stated the FD engine is alot more toward the race side of the continuum than we think. our motors are at the edge of current state of the art tune and when we add a few mods we are much further than we suspect along the high CCP state.
gasoline, any gasoline including racegas, auto-ignites at a mere 495 F. as we raise hp levels we are moving closer to auto ignition/knock/breaking apex seals. especially when our motors are over-carboned up w a combo of the external oil pump injecting the wrong kind of oil to lube our apex seals and the factory's fuel settings... (overly rich to cool the CCP). carbon deposits are irregular and often form small spikes which can glow and ignite fuel prematurely.
so there is no mystery as to why we incur engine failure. it isn't because it is a rotary per se. it is because it is a small displacement (159 cu inches or 2.6 liters) engine that is being pumped up w turbo'd air and it is really easy to turn up the boost for even higher output levels.
yes, the apex seal is a bit more fragile than a piston ring.
so that's the deal. sounds scary. but there is a fix and if properly applied the heat generated w the high CCP can be completely offset.
you can then have it all.
please see my thread in the 3rd Gen section for the FIX. since the thread is now over 200 posts, and i have edited out over 140, please DO read post one...
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/making-case-rotary-powered-fd-fix-806104/
BTW, just so as to avert any mushroom shaped clouds here, i am not knocking the other engines but using them to make the relative point re the rotary. run whatever you wish.
howard coleman
02-11-09, 10:11 AM
#5
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+1 to howard's post. i highly encourage anyone who is new to rotaries or simply has an FD to look into his auxiliary injection thread. its a HUGE and valuable step into making our FDs reliable even while being heavily modified.
02-11-09, 11:00 AM
#6
+2, I'm going to take this info to my professors at my school. I am an automotive Technology major (4 yr program) and I try to bring the rotary up as much as possible but NO ONE seems to give one ****. They all think it is unreliable and a POS. "No torque...apecks seals blow, blah blah".
This is quite interesting. Howard, I'm curious as to what your stance is on the whole rotary being a 1.3 liter vs a 2.6 (13b)?
the rotary has a power producing event everytime the combustion chamber reaches top dead center. the piston engine fires every other time the piston reaches TDC making the rotary a 2 cycle motor V the piston engine being a 4 cycle motor. to fairly compare the 2 you must double the displacement of the rotary. yes the rotary displaces 1.3 liters so call it a 1.3 liter motor from that aspect. since it has double the power events it is a 2.6 liter motor in my book. take your pick. howard///
This is quite interesting. Howard, I'm curious as to what your stance is on the whole rotary being a 1.3 liter vs a 2.6 (13b)?
the rotary has a power producing event everytime the combustion chamber reaches top dead center. the piston engine fires every other time the piston reaches TDC making the rotary a 2 cycle motor V the piston engine being a 4 cycle motor. to fairly compare the 2 you must double the displacement of the rotary. yes the rotary displaces 1.3 liters so call it a 1.3 liter motor from that aspect. since it has double the power events it is a 2.6 liter motor in my book. take your pick. howard///
Last edited by Howard Coleman; 02-11-09 at 12:23 PM.
02-11-09, 12:15 PM
#7
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kindly show them the thread howard linked in this one. it tells a story at how well the rotary engine performs in the 24hr Daytona.
piston engines: blown out, idling at 5k RPMs.
rotary engines: idling like they got off a cruise around town and ready for more.
just a couple highlights of his story there
piston engines: blown out, idling at 5k RPMs.
rotary engines: idling like they got off a cruise around town and ready for more.
just a couple highlights of his story there
Trending Topics
02-11-09, 11:25 PM
#8
A few more numbers from other Japanese turbocharged cars... including modified setups.
2.5L Subaru WRX STI: approx. 300 crank HP with stock setup... 300HP/152ci = 1.97 HP/c.i.
Quite a few shops are getting 450whp out of them (not sure if this is with pump gas, race gas, water/meth injection, or a combination...) assuming 500hp at the crank that's about 3.28 HP/c.i.
Apparently the Mitsubishi and Honda guys are making about that much power as well, with slightly less displacement. Those crazy Supra guys making 800whp with a 3.0L engine should be seeing 4.37 HP/ c.i.
-s-
2.5L Subaru WRX STI: approx. 300 crank HP with stock setup... 300HP/152ci = 1.97 HP/c.i.
Quite a few shops are getting 450whp out of them (not sure if this is with pump gas, race gas, water/meth injection, or a combination...) assuming 500hp at the crank that's about 3.28 HP/c.i.
Apparently the Mitsubishi and Honda guys are making about that much power as well, with slightly less displacement. Those crazy Supra guys making 800whp with a 3.0L engine should be seeing 4.37 HP/ c.i.
-s-
Last edited by scotty305; 02-11-09 at 11:30 PM.
02-12-09, 08:03 AM
#9
Racing Rotary Since 1983
Thread Starter
iTrader: (6)
this central message of this thread is too important to clutter w a sidetrack re the rotary displacement. it is what it is. it is 1.3 liters displacement and based on combustion events which are 2X that of a 4 cycle motor it should be compared to a 2X 4 cycle motor or 2.6 liters.
any further displacement conversation you wish is entirely welcomed in another thread.
i deleted our detour including my posts. please do not take this personally but this thread, along with the "Fix" thread, is important for all turbo'd rotary owners.
the key here is that 300 rear wheel FD horsepower is presently considered a quite conservative state of tune.
NOT.
300 rwhp is 345 flywheel is 2.17 horsepower per cubic inch!
compare that to the supercharged $116,000 Corvette ZR1 at 1.69 or the AMG Mercedes twin turbo at 1.81!
and we are talking about a 300 rwhp FD.
up the hp/cubic inch and you up the Combustion Chamber Pressure (CCP) and HEAT.
it is no accident that our engines fail. it is not due to them being rotaries. it is due to the fact that they are pumped up w alot of air.
while this sounds depressing there is actually a FIX. it is, of course Auxiliary Injection-AI, the addition of a highly efficient cooling substance to the fuel mix... water, alcohol or a mix.
AI is only injected in boost when you need it.
how well does it work?
last sep i made 498 rear wheel horsepower on 93 octane pump gas and AI and my knock readings averaged 9 (!) from 6000 to 8200! my egts were stable, not climbing, at 1550 F during the same period.
while i chose to use alcohol (methanol) as an AI injectant water works great to cool things down and is a bit easier to fixture and use.
either way AI solves the problem of the significant amount of CCP/HEAT generated from our turbo'd motors.
i recently pulled my motor after four years of usage just to take it apart to see how it was doing. it was running perfectly at the time. i found a virtually carbon free interior and a total 1 thousandths of an inch wear on my side seals. i could easily just reassemble it w new springs.
being carbon free is a big deal w rotaries. half of the motors i disassemble have sticking seals due to carbon. water steam cleans carbon away and alcohol disolves carbon. win win.
deal w CCP and you will have the same experience.
understand the real state of tune that exists within your motor.
deal with it.
kiss reliability issues good by.
read the "FIX" thread.
howard coleman
any further displacement conversation you wish is entirely welcomed in another thread.
i deleted our detour including my posts. please do not take this personally but this thread, along with the "Fix" thread, is important for all turbo'd rotary owners.
the key here is that 300 rear wheel FD horsepower is presently considered a quite conservative state of tune.
NOT.
300 rwhp is 345 flywheel is 2.17 horsepower per cubic inch!
compare that to the supercharged $116,000 Corvette ZR1 at 1.69 or the AMG Mercedes twin turbo at 1.81!
and we are talking about a 300 rwhp FD.
up the hp/cubic inch and you up the Combustion Chamber Pressure (CCP) and HEAT.
it is no accident that our engines fail. it is not due to them being rotaries. it is due to the fact that they are pumped up w alot of air.
while this sounds depressing there is actually a FIX. it is, of course Auxiliary Injection-AI, the addition of a highly efficient cooling substance to the fuel mix... water, alcohol or a mix.
AI is only injected in boost when you need it.
how well does it work?
last sep i made 498 rear wheel horsepower on 93 octane pump gas and AI and my knock readings averaged 9 (!) from 6000 to 8200! my egts were stable, not climbing, at 1550 F during the same period.
while i chose to use alcohol (methanol) as an AI injectant water works great to cool things down and is a bit easier to fixture and use.
either way AI solves the problem of the significant amount of CCP/HEAT generated from our turbo'd motors.
i recently pulled my motor after four years of usage just to take it apart to see how it was doing. it was running perfectly at the time. i found a virtually carbon free interior and a total 1 thousandths of an inch wear on my side seals. i could easily just reassemble it w new springs.
being carbon free is a big deal w rotaries. half of the motors i disassemble have sticking seals due to carbon. water steam cleans carbon away and alcohol disolves carbon. win win.
deal w CCP and you will have the same experience.
understand the real state of tune that exists within your motor.
deal with it.
kiss reliability issues good by.
read the "FIX" thread.
howard coleman
Last edited by Howard Coleman; 02-12-09 at 10:12 AM.
02-12-09, 08:10 AM
#10
Racing Rotary Since 1983
Thread Starter
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w regard to Scotty's post...
my point isn't necessarily that the turbo'd rotary makes more power per displacement than other turbo'd motors... just that it is making alot more hp per displacement than we think.
the real "magic" in the equation of course is the turbo. more air, combined w fuel means more ponies. and it is real easy to add air to the motor thanks to Garrett et al.
BTW, just to keep things consistant here, we are talking Flywheel hp on all of the above examples. to keep it simple just add 15% to rear wheel...
hc
my point isn't necessarily that the turbo'd rotary makes more power per displacement than other turbo'd motors... just that it is making alot more hp per displacement than we think.
the real "magic" in the equation of course is the turbo. more air, combined w fuel means more ponies. and it is real easy to add air to the motor thanks to Garrett et al.
BTW, just to keep things consistant here, we are talking Flywheel hp on all of the above examples. to keep it simple just add 15% to rear wheel...
hc
02-13-09, 12:07 AM
#13
Didn't mean to steal your thunder, Howard. I'm not too familiar with Hondas or Mitsubishis, but in speaking to someone who does a lot of work on STIs I was told that it's not uncommon for modified STI's to start dying around 60,000 miles. Suddenly I'm not so saddened that my original engine has been needing new coolant seals since about 83,000 miles.
IMHO, the significant difference is that the rotary acts like a two-stroke. The way I see it, the combustion chamber in a piston engine is only seeing a flame front once every other crank rotation. In contrast, the combustion section of the rotor housings and irons are seeing flame once per per revolution of the eccentric shaft. That's twice as often as the piston engine, or half the time to dissipate heat. By cooling the intake charge and/or keeping it cool, I agree that water or meth injection should do a great job of decreasing the probability of autoignition.
However, it's my opinion that autoignition in a rotary may be largely due to temperature as opposed to pressure.
IMHO, the significant difference is that the rotary acts like a two-stroke. The way I see it, the combustion chamber in a piston engine is only seeing a flame front once every other crank rotation. In contrast, the combustion section of the rotor housings and irons are seeing flame once per per revolution of the eccentric shaft. That's twice as often as the piston engine, or half the time to dissipate heat. By cooling the intake charge and/or keeping it cool, I agree that water or meth injection should do a great job of decreasing the probability of autoignition.
However, it's my opinion that autoignition in a rotary may be largely due to temperature as opposed to pressure.
Last edited by scotty305; 02-13-09 at 12:16 AM.
05-23-09, 09:48 AM
#15
Racing Rotary Since 1983
Thread Starter
iTrader: (6)
i am bumping my thread as it only has 695 reads and has vanished into the dustbin. while it may be somewhat repetitive relating to my "Fix" thread i think there is important new info in it and hope all get a chance to read it. please do read post one if you initially missed it.
hc
hc
05-23-09, 05:54 PM
#18
Hey, Howard. I reread the first post. I didn't realize you were older than me... I didn't start high school till 1961. Makes me feel better! Despite being so much younger, I do, however, remember the 61-62 chevy impala 409's and transition year vette's. They were a revelation...
Gordon
Gordon
It is interesting reading. I know it's off-topic from the OP's main point of CCP, and I don't have the data...but when you compare the FD's displacement to those other piston engines (especially the older cast-iron ones) I think engine weight vs. HP is also interesting. How many hp are produced per pound of engine weight?
01-06-10, 12:43 PM
#22
What are your thoughts on some sort of water injection on N/A rotaries? Of course they do not need the cooling benefit so much as with a turbocharged car, but Ive taken apart plenty of N/A engines that were plagued with carbon buildup, sticking seals, etc. I feel that a full time water injection system may be a waste, but maybe at least letting it ingest some at varying Rpms monthly or at some pre-determined interval may be key to keeping carbon from building up internally. Your thoughts?
01-06-10, 01:24 PM
#23
Sir Braps A lot
i just went into the garage and gave my motor a huge hug and a little kiss. Great post, i wish more people would understand this and just think about it but all the closed minded people will still bash on us.. o well at least we know whats going on
01-06-10, 01:43 PM
#24
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Has auxiliary meth and/or water injection been used on any turbocharged, rotary powered race cars? If so, I'd be impressed, since it would have to be iron clad reliable, but I don't think any of the racing RX-8s are using it (which are n/a I believe, so that's not unexpected). As much as I admire your work, Howard, you have so much stuff hanging off your engine and everywhere else I'd be worried something would fly off if you took it to the track.
I like simple. "The Fix" needs to be simple and 100% reliable or it's not a fix. Water injection at least seems fairly simple, but there is still a risk of something going wrong.
I like simple. "The Fix" needs to be simple and 100% reliable or it's not a fix. Water injection at least seems fairly simple, but there is still a risk of something going wrong.
01-06-10, 01:51 PM
#25
yes i do like to support the community and hype them up but i also know how touchy the rotary engine is, it is much less forgiving than piston engines are when not built and tuned properly resulting in heartbreak much more often than with most other engine type. simplifying them is the key but i and we also realize that most states are clamping down on those breaking emissions laws, here in california you can't upgrade the car and still make it smog legal really at all so this is all meaningless to the largest population state of 7 owners in the US. basically all i see is hype to modify a great car to offer more headache to owners to be pulled over and reffed resulting in a great deal of stress.
yes, everyone has their choice to break the law and pay for the result but i also see a comparison between a 225WHP car and one with twice that HP that is completely legal to drive here. do i wish legislators would release the death grip on california emissions in an effort to force people to buy new cars to save the failing auto industry? you bet i do! unfortunately i also know that that won't happen, so in the end you wind up with modified cars on the road who have the choice to not be selfish and run a smog pump and catalyst and save the air or to dump it all for power and fuel mileage/reliability. we already know what most people will choose..
i would rather see this state be more like others that don't pop your hood, where if your car passes the sniffer then it's all good. too bad that won't happen.
and yes, even adding an auxiliary injection system will fail you on the visual on a completely stock car.