A question about rotorys - TriStateTuners.com :: Home of Tristate Auto Enthusiast

Cardriverx · 07-30-2007, 11:18 PM

Ive always wondered, is engine knock as damageing to them as piston engines? What happens, can it like crack the rotor? Is the timeing generaly the same in rotorys vs piston? Or do rotorys fire the spark way before/after TDC?

240sxDann · 07-30-2007, 11:29 PM

there is no TDC, or BDC. Remember, its not going up and down, its spinning. And dont quote, but I dont see how you could have knock besides running too much boost. On an NA rotary I dont think its possible to have knock. However, knock is knock no matter what its in so I dont think it could be too good for it.

Cardriverx · 07-30-2007, 11:35 PM

by TDC, I mean the point at which the ignition side of the rotor (power stroke in a piston) is the closest to the houseing. does that make sence?

Cardriverx · 07-30-2007, 11:39 PM

also, would it be possible for a diesel rotary? could it stand the high compression it would need? all it would need is direct injection.

240sxDann · 07-30-2007, 11:42 PM

http://auto.howstuffworks.com/rotary-engine4.htm

foss · 07-31-2007, 12:32 AM

wait for NOPSTNS. he knows everything about rotaries.

240sxDann · 07-31-2007, 01:28 AM

^ pretty much sums it up

peteyturbo · 07-31-2007, 02:16 AM

yes. no. no. no...Good day.. Detonation is what kills a rotary engine..They have the tendancy to blow apex seals when detonated which is the sealing surface in the combustion (and all) cycles, which is kind of like the equivelant to a piston ring..The rotary has a top dead center but it really is not top ,dead, or center comparitively.Knock is the grandson to detonation, and in rotary engines, it climbs a family tree like nobody's buisness

BradC · 07-31-2007, 07:58 AM

Quote:

Originally Posted by peteyturbo

yes. no. no. no...Good day.. Detonation is what kills a rotary engine..They have the tendancy to blow apex seals when detonated which is the sealing surface in the combustion (and all) cycles, which is kind of like the equivelant to a piston ring..The rotary has a top dead center but it really is not top ,dead, or center comparitively.Knock is the grandson to detonation, and in rotary engines, it climbs a family tree like nobody's buisness

Yup, what he said. Detonation can kill a rotary in a few pings.

NOPSTNS · 07-31-2007, 06:13 PM

damn i am too late.....i need to start whorin these threads more! petey turbo hit the nail on the head...

knock is DEADLY to a rotary. yes NA's can knock and die. pull an injector connector or run reall pissy gas and see what happens. the knock sensor is pretty sensitive on the rx8s (mounted on the rear rotor housing bc thats the one that is hotter) bc they want to reallyt keep that junk in check. there is only a 2mm thick piece of metal holding ur compression in check, crack that sucker and metal pieces will be spinnin in ur engine and ruin ur day. in a piston engien u have the piston face and like fourty rings holding compression in check. light knock in those things will take a few b4 u see real damage. in a rotary u have....well, the apex seal will take a royal **** on u. they dont like knock, which is ONE of the reasons they r tuned wicked rich from the factory, rich is safe....

on the older rotaries the apex seal would prolly leave somewhat quickly bc the exhaust ports are in the rotor housings, in the rx8 ur not so lucky. they moved the exhaust ports (and doubled them) and moved them into the front and rear end plates and the intermediate housing. they did it on purpose to recycle oil unused oil and fuel for the next combustion event. downside of that is if u got forgeing material (ie APEX SEALS!) floating around, ur done dude.
so yes, knock is dealdy to rotaries even more so than piston engines.

ok lets dive into what TDC is....ill use the renesis engine as an example.

they fire WAY ahead of TDC, at idle they are about 5 degrees BTDC and at WOT at 9k they jump to 60 degrees BTDC (if ur runnin premium fuel which u SHOULD BE!) idle is the only time the trailing plugs fire before the leadings, once u tap the throttle they switch to leadings first then trailings...

rotary engines have TDC and BDC its just flipped on its side.....for a better idea think of boxer engines how the spark plugs are on the sides...so are rotaries. their TDC is on the side of the engine but its still the top of the combustion chamber....

timing on rotaries are a lot like pistons engine but u need to remember that a rotor spins 1/3 the speed of the eccentric shaft but the internal gear of the rotor has 2 teeth for every three teeth on the external gear of the E shaft...so the timign is WAY early.....

so a rotary running at say...60 degrees BTDC isnt too crazy bc the rotor spins much slower then the e shaft 60 degrees on rotor is like 20 degrees on piston....

and yes diesel rotary has been tried, theres a reason it aint around.

rotary engines kinds cant really go above 10:1 compression so a 20:1 diesel really aint gonna work. it has to do with surface area : volume ratio. the rotor face is huge and the space it fills is small so it has a .....for lack of a better term....."wide" combustion area. which is ONE of the reasons they run so damn rich. and why they need two spark plugs per housing. u can run one one plug, believe me, ive done it, but ur emissions and ur power are really gonna take a dive.

and direct injection is next for the rotary engine. they have been tinkering and testing with it for years and in 2010 when the next rx8 comes out itll be in that....more power, less emission, no more flooding...yay!

peteyturbo · 07-31-2007, 06:31 PM

I know it was either Dave at kd rotary or one of his customers were making a custom one off direct injection setup on an S5 13b..I think it was the guys that makes those caterham cars or whatever they are out near media or the blue route somewhere..He also owns an RX8 and is one hell of an engineer..

Quote:

Originally Posted by NOPSTNS

damn i am too late.....i need to start whorin these threads more! petey turbo hit the nail on the head...

knock is DEADLY to a rotary. yes NA's can knock and die. pull an injector connector or run reall pissy gas and see what happens. the knock sensor is pretty sensitive on the rx8s (mounted on the rear rotor housing bc thats the one that is hotter) bc they want to reallyt keep that junk in check. there is only a 2mm thick piece of metal holding ur compression in check, crack that sucker and metal pieces will be spinnin in ur engine and ruin ur day. in a piston engien u have the piston face and like fourty rings holding compression in check. light knock in those things will take a few b4 u see real damage. in a rotary u have....well, the apex seal will take a royal **** on u. they dont like knock, which is ONE of the reasons they r tuned wicked rich from the factory, rich is safe....

on the older rotaries the apex seal would prolly leave somewhat quickly bc the exhaust ports are in the rotor housings, in the rx8 ur not so lucky. they moved the exhaust ports (and doubled them) and moved them into the front and rear end plates and the intermediate housing. they did it on purpose to recycle oil unused oil and fuel for the next combustion event. downside of that is if u got forgeing material (ie APEX SEALS!) floating around, ur done dude.
so yes, knock is dealdy to rotaries even more so than piston engines.

ok lets dive into what TDC is....ill use the renesis engine as an example.

they fire WAY ahead of TDC, at idle they are about 5 degrees BTDC and at WOT at 9k they jump to 60 degrees BTDC (if ur runnin premium fuel which u SHOULD BE!) idle is the only time the trailing plugs fire before the leadings, once u tap the throttle they switch to leadings first then trailings...

rotary engines have TDC and BDC its just flipped on its side.....for a better idea think of boxer engines how the spark plugs are on the sides...so are rotaries. their TDC is on the side of the engine but its still the top of the combustion chamber....

timing on rotaries are a lot like pistons engine but u need to remember that a rotor spins 1/3 the speed of the eccentric shaft but the internal gear of the rotor has 2 teeth for every three teeth on the external gear of the E shaft...so the timign is WAY early.....

so a rotary running at say...60 degrees BTDC isnt too crazy bc the rotor spins much slower then the e shaft 60 degrees on rotor is like 20 degrees on piston....

and yes diesel rotary has been tried, theres a reason it aint around.

rotary engines kinds cant really go above 10:1 compression so a 20:1 diesel really aint gonna work. it has to do with surface area : volume ratio. the rotor face is huge and the space it fills is small so it has a .....for lack of a better term....."wide" combustion area. which is ONE of the reasons they run so damn rich. and why they need two spark plugs per housing. u can run one one plug, believe me, ive done it, but ur emissions and ur power are really gonna take a dive.

and direct injection is next for the rotary engine. they have been tinkering and testing with it for years and in 2010 when the next rx8 comes out itll be in that....more power, less emission, no more flooding...yay!

Cardriverx · 07-31-2007, 09:22 PM

Quote:

Originally Posted by peteyturbo

I know it was either Dave at kd rotary or one of his customers were making a custom one off direct injection setup on an S5 13b..I think it was the guys that makes those caterham cars or whatever they are out near media or the blue route somewhere..He also owns an RX8 and is one hell of an engineer..

You mean the guys with that beastly rotary powered monster that was built from the ground up? Where are they located? I wanna take a drive over there.

Thnaks nopstns, I have herd rx8 sales havent been the best ever, so I hope mazda continues with another rotary car. I already had a good understanding of how rotarys work, but now I know much more =). Now for swaping a 13b in my car..

TurboTagTeam · 08-01-2007, 11:55 AM

Rx-8 sales have been bad becuase of recalls and stupid owners.

Rotaries burn oil. Some people just cant grasp this. Rotaries inject oil into the combustion cycle to help lubricate the apex seals and housings. Soooo, because they inject oil, they burn oil. Soooo, if you dont keep an eye on your oil level...no more rotary 4 u. As far as I know there was a problem with the "oil level light" on some RX-8's. So alot of them went boom.

Personally I have never liked RX-8's. I driven one and it felt like a cadillac compared to my FD. My FD was more like a fighter jet with no wings. I was REALLY upset that the RX-8 was NA. What an upset slapping the RX name badge on that car after the FD. Plus I HATE that stupid suicide door they have.

Okay...knock.... Yes, rotaries knock very easily if not tuned right. The basic rule with an REW motor(3rd gen) is that if you heard it knock, call you motor distributor because your engine is toast. I went through many engines in my FD. It's not all that bad though. A REMAN short block is only 2200.

13b in a miata??? Very good idea. Just make sure it's boosted. All motor rotaries bore me.

peteyturbo · 08-02-2007, 04:36 AM

I have watched a mildly swapped miata with a 13brew wun a mid 10 second pass at island dragway, awesome car.. Also, yes, the guy I am referring to builds his own line of cars from the ground up. They look like the caterham 7's but I can't remember the name, they use an S5 turboII factory reman engines and they are awesome to say the least, he located somewhere off the blue route near media or something..

Quote:

Originally Posted by Cardriverx

You mean the guys with that beastly rotary powered monster that was built from the ground up? Where are they located? I wanna take a drive over there.

Thnaks nopstns, I have herd rx8 sales havent been the best ever, so I hope mazda continues with another rotary car. I already had a good understanding of how rotarys work, but now I know much more =). Now for swaping a 13b in my car..

NOPSTNS · 08-02-2007, 07:30 AM

they make engine swap comnversions for the 13b into the miata. i think its mazsport or somebody....the miata was made for a rotary...

and turbo tag team, i agree with everything u said....rx8s and rx7s shouldnt even be said in the same sentence they r so different. and i cried myself to sleep for yrs when they announced itd be NA!

Raven18940 · 08-02-2007, 07:39 AM

NOPSTNS, bring back the "boost in, apex seals out" pic.

NOPSTNS · 08-03-2007, 07:28 AM

since i always love changing my avatar faster than u can say 'boost creep'...here ya go raven....

9 Ball · 08-03-2007, 07:55 AM

Quote:

Originally Posted by NOPSTNS

and i cried myself to sleep for yrs when they announced itd be NA!

I think we all wept openly when we found out it would be an N/A.

NOPSTNS · 08-03-2007, 05:57 PM

the days of turbo rotaries from the factory might be over fellas....im about 75% sure the next gen rx8 is NA as well......continue ur cryin, as i do now, with each 9500 rpm shift i hear no release of boost pressure....sigh....

su_maverick · 08-06-2007, 02:06 PM

NOPSTNS- as far as you were talking about with the need for 2 spark plugs per chamber. This was really a cheap way out from Mazda rather than optimal. If you look at the position of the rotor when the trailing plug is fired, it is very close to the apex seal and has been shown to actually slow down the movement of the rotor in the housing and put stress on the trailing apex seal. With a good tuner who knows what they are doing in this case, they can put in plugs that will work for this particular situation and eliminate the trailing plugs by tuning them out. The whole idea of the combustion cycle in a rotary is to spin the rotor faster and thus create more HP (sorry if some of this stuff is redundant to you). By firing late on the rotor you are actually creating the combustion on the trailing size of the rotor and putting the majority of the pressure on the trailing side rather than the leading. Granted, it will take a very good tuner who knows exactly what heat range plug to use to make this work correctly but you should actually see better low end torque with this setup.

I agree that the days of turbo rotaries are probably a thing of the past. The problem is that the rotary is a sensitive engine and as you stated before, the general public is not equipped with enough knowledge or common sense to properly maintain them. You have to keep on top of maintenance for all fuel, oil and cooling related systems on the car to ensure engine longevity. By adding a turbo to the mix, all three of these systems now have a lot more variability to them since the turbo is a completely reactive system that is hard to regulate precisely. To be honest, I think a rotary car would benefit more from a supercharger setup than a turbo. A supercharger is controlled directly from the eccentric shaft which would mean that the compressor wheel speed is link directly to engine RPM’s and can be tuned a lot better. A supercharger would also give the rotary something that it inherently lacks, torque. Rotaries have always been great motors for turbochargers because of their exhaust output and high rev limits but the flipside cannot be said. Turbos have not been kind to rotaries.

07-30-2007, 11:18 PM	#1
Cardriverx Tri-State Addict Join Date: Jun 2007 Location: media Member #5090 My Ride: 1993 Miata Turbo ; 2001 Saab 9-5 Aero Wagon iTrader: (1)	A question about rotorys Ive always wondered, is engine knock as damageing to them as piston engines? What happens, can it like crack the rotor? Is the timeing generaly the same in rotorys vs piston? Or do rotorys fire the spark way before/after TDC?

07-30-2007, 11:39 PM	#4
Cardriverx Tri-State Addict Join Date: Jun 2007 Location: media Member #5090 My Ride: 1993 Miata Turbo ; 2001 Saab 9-5 Aero Wagon iTrader: (1)	also, would it be possible for a diesel rotary? could it stand the high compression it would need? all it would need is direct injection. Last edited by Cardriverx; 07-30-2007 at 11:41 PM.

07-31-2007, 02:16 AM	#8
peteyturbo Tri-State Post Whore Join Date: Feb 2006 Location: NE Phila. Member #1450 iTrader: (0)	yes. no. no. no...Good day.. Detonation is what kills a rotary engine..They have the tendancy to blow apex seals when detonated which is the sealing surface in the combustion (and all) cycles, which is kind of like the equivelant to a piston ring..The rotary has a top dead center but it really is not top ,dead, or center comparitively.Knock is the grandson to detonation, and in rotary engines, it climbs a family tree like nobody's buisness __________________ To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures. To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures. To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures. To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures. Last edited by peteyturbo; 07-31-2007 at 02:21 AM.

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07-30-2007, 11:35 PM	#3
Cardriverx Tri-State Addict Join Date: Jun 2007 Location: media Member #5090 My Ride: 1993 Miata Turbo ; 2001 Saab 9-5 Aero Wagon iTrader: (1)	by TDC, I mean the point at which the ignition side of the rotor (power stroke in a piston) is the closest to the houseing. does that make sence?

07-31-2007, 06:13 PM	#10
NOPSTNS Tri-State Post Whore Join Date: Dec 2006 Location: Los Angeles, CA Member #3176 iTrader: (0)	damn i am too late.....i need to start whorin these threads more! petey turbo hit the nail on the head... knock is DEADLY to a rotary. yes NA's can knock and die. pull an injector connector or run reall pissy gas and see what happens. the knock sensor is pretty sensitive on the rx8s (mounted on the rear rotor housing bc thats the one that is hotter) bc they want to reallyt keep that junk in check. there is only a 2mm thick piece of metal holding ur compression in check, crack that sucker and metal pieces will be spinnin in ur engine and ruin ur day. in a piston engien u have the piston face and like fourty rings holding compression in check. light knock in those things will take a few b4 u see real damage. in a rotary u have....well, the apex seal will take a royal **** on u. they dont like knock, which is ONE of the reasons they r tuned wicked rich from the factory, rich is safe.... on the older rotaries the apex seal would prolly leave somewhat quickly bc the exhaust ports are in the rotor housings, in the rx8 ur not so lucky. they moved the exhaust ports (and doubled them) and moved them into the front and rear end plates and the intermediate housing. they did it on purpose to recycle oil unused oil and fuel for the next combustion event. downside of that is if u got forgeing material (ie APEX SEALS!) floating around, ur done dude. so yes, knock is dealdy to rotaries even more so than piston engines. ok lets dive into what TDC is....ill use the renesis engine as an example. they fire WAY ahead of TDC, at idle they are about 5 degrees BTDC and at WOT at 9k they jump to 60 degrees BTDC (if ur runnin premium fuel which u SHOULD BE!) idle is the only time the trailing plugs fire before the leadings, once u tap the throttle they switch to leadings first then trailings... rotary engines have TDC and BDC its just flipped on its side.....for a better idea think of boxer engines how the spark plugs are on the sides...so are rotaries. their TDC is on the side of the engine but its still the top of the combustion chamber.... timing on rotaries are a lot like pistons engine but u need to remember that a rotor spins 1/3 the speed of the eccentric shaft but the internal gear of the rotor has 2 teeth for every three teeth on the external gear of the E shaft...so the timign is WAY early..... so a rotary running at say...60 degrees BTDC isnt too crazy bc the rotor spins much slower then the e shaft 60 degrees on rotor is like 20 degrees on piston.... and yes diesel rotary has been tried, theres a reason it aint around. rotary engines kinds cant really go above 10:1 compression so a 20:1 diesel really aint gonna work. it has to do with surface area : volume ratio. the rotor face is huge and the space it fills is small so it has a .....for lack of a better term....."wide" combustion area. which is ONE of the reasons they run so damn rich. and why they need two spark plugs per housing. u can run one one plug, believe me, ive done it, but ur emissions and ur power are really gonna take a dive. and direct injection is next for the rotary engine. they have been tinkering and testing with it for years and in 2010 when the next rx8 comes out itll be in that....more power, less emission, no more flooding...yay!

08-01-2007, 11:55 AM	#13
TurboTagTeam Tri-State Post Whore Banned Join Date: Mar 2005 Location: Cell Block F Member #275 My Ride: constantly changes iTrader: (2)	Rx-8 sales have been bad becuase of recalls and stupid owners. Rotaries burn oil. Some people just cant grasp this. Rotaries inject oil into the combustion cycle to help lubricate the apex seals and housings. Soooo, because they inject oil, they burn oil. Soooo, if you dont keep an eye on your oil level...no more rotary 4 u. As far as I know there was a problem with the "oil level light" on some RX-8's. So alot of them went boom. Personally I have never liked RX-8's. I driven one and it felt like a cadillac compared to my FD. My FD was more like a fighter jet with no wings. I was REALLY upset that the RX-8 was NA. What an upset slapping the RX name badge on that car after the FD. Plus I HATE that stupid suicide door they have. Okay...knock.... Yes, rotaries knock very easily if not tuned right. The basic rule with an REW motor(3rd gen) is that if you heard it knock, call you motor distributor because your engine is toast. I went through many engines in my FD. It's not all that bad though. A REMAN short block is only 2200. 13b in a miata??? Very good idea. Just make sure it's boosted. All motor rotaries bore me.

08-02-2007, 07:30 AM	#15
NOPSTNS Tri-State Post Whore Join Date: Dec 2006 Location: Los Angeles, CA Member #3176 iTrader: (0)	they make engine swap comnversions for the 13b into the miata. i think its mazsport or somebody....the miata was made for a rotary... and turbo tag team, i agree with everything u said....rx8s and rx7s shouldnt even be said in the same sentence they r so different. and i cried myself to sleep for yrs when they announced itd be NA!

08-03-2007, 07:28 AM	#17
NOPSTNS Tri-State Post Whore Join Date: Dec 2006 Location: Los Angeles, CA Member #3176 iTrader: (0)	since i always love changing my avatar faster than u can say 'boost creep'...here ya go raven....

08-03-2007, 05:57 PM	#19
NOPSTNS Tri-State Post Whore Join Date: Dec 2006 Location: Los Angeles, CA Member #3176 iTrader: (0)	the days of turbo rotaries from the factory might be over fellas....im about 75% sure the next gen rx8 is NA as well......continue ur cryin, as i do now, with each 9500 rpm shift i hear no release of boost pressure....sigh....

08-06-2007, 02:06 PM	#20
su_maverick Tri-State Addict Join Date: Apr 2006 Location: Bergen Co. Member #1755 My Ride: 2001 Saturn SC1 iTrader: (0)	NOPSTNS- as far as you were talking about with the need for 2 spark plugs per chamber. This was really a cheap way out from Mazda rather than optimal. If you look at the position of the rotor when the trailing plug is fired, it is very close to the apex seal and has been shown to actually slow down the movement of the rotor in the housing and put stress on the trailing apex seal. With a good tuner who knows what they are doing in this case, they can put in plugs that will work for this particular situation and eliminate the trailing plugs by tuning them out. The whole idea of the combustion cycle in a rotary is to spin the rotor faster and thus create more HP (sorry if some of this stuff is redundant to you). By firing late on the rotor you are actually creating the combustion on the trailing size of the rotor and putting the majority of the pressure on the trailing side rather than the leading. Granted, it will take a very good tuner who knows exactly what heat range plug to use to make this work correctly but you should actually see better low end torque with this setup. I agree that the days of turbo rotaries are probably a thing of the past. The problem is that the rotary is a sensitive engine and as you stated before, the general public is not equipped with enough knowledge or common sense to properly maintain them. You have to keep on top of maintenance for all fuel, oil and cooling related systems on the car to ensure engine longevity. By adding a turbo to the mix, all three of these systems now have a lot more variability to them since the turbo is a completely reactive system that is hard to regulate precisely. To be honest, I think a rotary car would benefit more from a supercharger setup than a turbo. A supercharger is controlled directly from the eccentric shaft which would mean that the compressor wheel speed is link directly to engine RPM’s and can be tuned a lot better. A supercharger would also give the rotary something that it inherently lacks, torque. Rotaries have always been great motors for turbochargers because of their exhaust output and high rev limits but the flipside cannot be said. Turbos have not been kind to rotaries.