why do rx7's run lower boost?
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why do rx7's run lower boost?
sup all, i'm new to the rx7 world.. been lounging mostly at supraforums.com, so i decided to come and take a look at rx-7's, since they seem to be the other good high-end jap sports car. (3000gt's are a little too fat for my tastes, 300zx too crude?)
anyway, so my question is why do rx7 engines run significantly lower boost? I've seen talk about mostly 12-15psi or so, whereas supras run up to 20 on pump gas, 30 on race gas... for street cars
does it have something to do with the design of the rotary engine?
anyway, so my question is why do rx7 engines run significantly lower boost? I've seen talk about mostly 12-15psi or so, whereas supras run up to 20 on pump gas, 30 on race gas... for street cars
does it have something to do with the design of the rotary engine?
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That's a pretty broad generalization. Most people will run lower boost to preserve their engine to some extent. The RX7 doesn't need to run wild boost numbers to be a fast street car... but they can.
For the most part, an rx7 with 450 rwhp is gonna be just as fast (straight line here fellas) as a MKIV with 600+ rwhp. The power to weight ratio is better.
There is a myriad of possible responses to this...
For the most part, an rx7 with 450 rwhp is gonna be just as fast (straight line here fellas) as a MKIV with 600+ rwhp. The power to weight ratio is better.
There is a myriad of possible responses to this...
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as a general answer i think piston owners cant destroy there motor with a single ping (detonation) and therefore are prepared to run much closer to the wind than rotary owners are.
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Originally posted by HWO
as a general answer i think piston owners cant destroy there motor with a single ping (detonation) and therefore are prepared to run much closer to the wind than rotary owners are.
as a general answer i think piston owners cant destroy there motor with a single ping (detonation) and therefore are prepared to run much closer to the wind than rotary owners are.
#5
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A turbo rotary, yes. If you're lucky, you get three or four pings, and if you're really lucky, you let off after the first couple and before the fatal one.
My N/A detonated dozens of times and it still lives strong. It sounds absolutely horrible, the car kicks back and it makes a noise that's a cross between a belt chirp and a bone snapping.
My N/A detonated dozens of times and it still lives strong. It sounds absolutely horrible, the car kicks back and it makes a noise that's a cross between a belt chirp and a bone snapping.
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Originally posted by krazyjl
a single detonation will kill a rotary???
a single detonation will kill a rotary???
a) brake an apex seal, or
b)crack an end plate
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Originally posted by HWO
one single ping is enough to either
a) brake an apex seal, or
b)crack an end plate
one single ping is enough to either
a) brake an apex seal, or
b)crack an end plate
so it seems the apex seal is the achilles heel of the engine
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Originally posted by peejay
A turbo rotary, yes. If you're lucky, you get three or four pings, and if you're really lucky, you let off after the first couple and before the fatal one.
My N/A detonated dozens of times and it still lives strong. It sounds absolutely horrible, the car kicks back and it makes a noise that's a cross between a belt chirp and a bone snapping.
A turbo rotary, yes. If you're lucky, you get three or four pings, and if you're really lucky, you let off after the first couple and before the fatal one.
My N/A detonated dozens of times and it still lives strong. It sounds absolutely horrible, the car kicks back and it makes a noise that's a cross between a belt chirp and a bone snapping.
Anyone try a MSD knock-alert on a rotary??
Max
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The Apex seals "are" the achilles heal of the rotary engine. Ask yourself this question, and this question only. Why haven't we heard of an FD running over 1000HP on the stock seals? Not even fine tuning will help the rotary. 600-700 on a dual rotary is what you'll ever see, right before detonation. That type of HP will get you down the 1320 real quick, although the engine is as temporary as a styrofome cup in a microwave. 2-3 runs and it's all over. REBUILD TIME. Carl...
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Originally posted by wankawankel
The Apex seals "are" the achilles heal of the rotary engine. Ask yourself this question, and this question only. Why haven't we heard of an FD running over 1000HP on the stock seals? Not even fine tuning will help the rotary. 600-700 on a dual rotary is what you'll ever see, right before detonation. That type of HP will get you down the 1320 real quick, although the engine is as temporary as a styrofome cup in a microwave. 2-3 runs and it's all over. REBUILD TIME. Carl...
The Apex seals "are" the achilles heal of the rotary engine. Ask yourself this question, and this question only. Why haven't we heard of an FD running over 1000HP on the stock seals? Not even fine tuning will help the rotary. 600-700 on a dual rotary is what you'll ever see, right before detonation. That type of HP will get you down the 1320 real quick, although the engine is as temporary as a styrofome cup in a microwave. 2-3 runs and it's all over. REBUILD TIME. Carl...
I am pretty sure you'll find the puerto rican guys are making similar HP, the difference is, they know how to make that kinda HP, and the rest of people DONT.
#12
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Originally posted by HWO
time for a quick update - Rice Racing's 13BPPT is currently making 830HP, not bad for a 2 rotor
I am pretty sure you'll find the puerto rican guys are making similar HP, the difference is, they know how to make that kinda HP, and the rest of people DONT.
time for a quick update - Rice Racing's 13BPPT is currently making 830HP, not bad for a 2 rotor
I am pretty sure you'll find the puerto rican guys are making similar HP, the difference is, they know how to make that kinda HP, and the rest of people DONT.
#13
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Originally posted by wankawankel
The Apex seals "are" the achilles heal of the rotary engine. Ask yourself this question, and this question only. Why haven't we heard of an FD running over 1000HP on the stock seals?
The Apex seals "are" the achilles heal of the rotary engine. Ask yourself this question, and this question only. Why haven't we heard of an FD running over 1000HP on the stock seals?
Answer... they're freakin' tiny engines and they don't rev as high as a full-out race boinger. Unless *you* figure out how to make a 13B live at 17k. Torque or RPM, you need to make more of either or both to make more HP... you make more torque with more displacement or higher combustion pressures, and you can't get more displacement out of a 13B.
#16
Originally posted by wankawankel
Not to rain on anyone's parade, but that 830 HP rotary will probably last 3 runs before rebuild time. That was my whole point. Rotaries don't boost up because of longevity. Carl...
Not to rain on anyone's parade, but that 830 HP rotary will probably last 3 runs before rebuild time. That was my whole point. Rotaries don't boost up because of longevity. Carl...
I happen to know a few people that are making well over 700RWHP and running with stock seals that are not rebuilding their motors after 3 runs. It just so happens that a very good friend of mine have over 60 runs on his motor and he's running at 40+psi. One of the top rotary runners in the US is making well over 790RWHP and he's not rebuilding his motor after 3 runs!
As mentioned before by HWO(Shane) correct tuning is the key to motor longevity may it be piston or rotary!
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I think the eventual limiting factors would be the stationary gears, and the ability keep the housings clamped tightly, to stop them from shifting and what not, the eccentric shaft is pretty beefy and being that it does need see the entire load from from the rotors mostly just the thrust load, some of the load is carryied by the gears, it can handle alot of power. Eventually though the rotor faces do collapse from excessive boost as illustrated by racing beat, but psi alone is not what makes power, so as rotary port technology gets better along with better turbocharging tech, we should see rotary power increase with reduced boost levels as we have seen thanks to people brave enough to slap t04e's and what not on the sides of the their motors..
I really don't think people are rebuilding their motors every 3 races, there simply are not enough core motors and parts in North America to support such numbers, such numbers would have driven the cost of parts through the roof..Max
I really don't think people are rebuilding their motors every 3 races, there simply are not enough core motors and parts in North America to support such numbers, such numbers would have driven the cost of parts through the roof..Max
#18
Originally posted by Maxthe7man
I think the eventual limiting factors would be the stationary gears, and the ability keep the housings clamped tightly, to stop them from shifting and what not, the eccentric shaft is pretty beefy and being that it does need see the entire load from from the rotors mostly just the thrust load, some of the load is carryied by the gears, it can handle alot of power. Eventually though the rotor faces do collapse from excessive boost as illustrated by racing beat, but psi alone is not what makes power, so as rotary port technology gets better along with better turbocharging tech, we should see rotary power increase with reduced boost levels as we have seen thanks to people brave enough to slap t04e's and what not on the sides of the their motors..
I really don't think people are rebuilding their motors every 3 races, there simply are not enough core motors and parts in North America to support such numbers, such numbers would have driven the cost of parts through the roof..Max
I think the eventual limiting factors would be the stationary gears, and the ability keep the housings clamped tightly, to stop them from shifting and what not, the eccentric shaft is pretty beefy and being that it does need see the entire load from from the rotors mostly just the thrust load, some of the load is carryied by the gears, it can handle alot of power. Eventually though the rotor faces do collapse from excessive boost as illustrated by racing beat, but psi alone is not what makes power, so as rotary port technology gets better along with better turbocharging tech, we should see rotary power increase with reduced boost levels as we have seen thanks to people brave enough to slap t04e's and what not on the sides of the their motors..
I really don't think people are rebuilding their motors every 3 races, there simply are not enough core motors and parts in North America to support such numbers, such numbers would have driven the cost of parts through the roof..Max
The E-shaft is much weaker than you think and is presently a problem for high HP rotaries. I've seen one break and many bent in the middle. Some people have figured out how to make a center bearing work and that should help. As for the rotor faces collapsing, that only happens when detonation/pre-ignition have occured.
I've seen more stock motors with dented rotors than I've seen in high hp motors. It's all about the tuning!
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In that case, is any one interested in tuning a T88 powered FD, with a Power FC for a computer? I have the car running well for daily use, but I blew the motor during the 1320 under 17 psi. Now I have a new stock rebuild, and ready to get those high HP numbers you guys are talking about. Carl...
Any takers?
Any takers?
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Interesting, it looks like a substanial piece considering it doesn not reall hold any of the static load of the rotors, or deal with the directional change of the rotors 100%, I should throw my RB book out the window I guess, they say that e-shaft failure is rare, except in the FC3s motors when pushed to the limit, apprently that oil cooling passage with the thermowax valve/stat is the weak link, out of interest what e-shaft are you using?
I can't really argue with you on this one, your sig says it all, but some of the pics I have seen of collapsed rotors had the apex seals intact, some unfortunate souls found the combustion pressure limit of a rotor face, and they simply collapsed, this is not intrinsic though to rotaries, this also happens in piston engine when the dome is simply not thick enough to with stand the force applied to out, even with perfect combustion, both rotors showed the same destruction in one motor, apparently at 30 psi of boost, but this could also depend on exactly what motor it was, and what generation, the FD stuff looks beefier than the FC stuff...Max
I can't really argue with you on this one, your sig says it all, but some of the pics I have seen of collapsed rotors had the apex seals intact, some unfortunate souls found the combustion pressure limit of a rotor face, and they simply collapsed, this is not intrinsic though to rotaries, this also happens in piston engine when the dome is simply not thick enough to with stand the force applied to out, even with perfect combustion, both rotors showed the same destruction in one motor, apparently at 30 psi of boost, but this could also depend on exactly what motor it was, and what generation, the FD stuff looks beefier than the FC stuff...Max
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yes that is exactly the point, the apex seals didn't break, the end plates didn't crack, so the next weakest link - the rotor's face gave in.
Where is Peter in a time like this, he'd come up with more data than you can poke a stick at about how much HP each part of the motor can handle.
His 13BPPT making 830HP is only at mild boost and not running on super juice yet. he seems very confident it'll make over 1000HP when he gets it sorted.
Where is Peter in a time like this, he'd come up with more data than you can poke a stick at about how much HP each part of the motor can handle.
His 13BPPT making 830HP is only at mild boost and not running on super juice yet. he seems very confident it'll make over 1000HP when he gets it sorted.
#23
Originally posted by Maxthe7man
Interesting, it looks like a substanial piece considering it doesn not reall hold any of the static load of the rotors, or deal with the directional change of the rotors 100%, I should throw my RB book out the window I guess, they say that e-shaft failure is rare, except in the FC3s motors when pushed to the limit, apprently that oil cooling passage with the thermowax valve/stat is the weak link, out of interest what e-shaft are you using?
I can't really argue with you on this one, your sig says it all, but some of the pics I have seen of collapsed rotors had the apex seals intact, some unfortunate souls found the combustion pressure limit of a rotor face, and they simply collapsed, this is not intrinsic though to rotaries, this also happens in piston engine when the dome is simply not thick enough to with stand the force applied to out, even with perfect combustion, both rotors showed the same destruction in one motor, apparently at 30 psi of boost, but this could also depend on exactly what motor it was, and what generation, the FD stuff looks beefier than the FC stuff...Max
Interesting, it looks like a substanial piece considering it doesn not reall hold any of the static load of the rotors, or deal with the directional change of the rotors 100%, I should throw my RB book out the window I guess, they say that e-shaft failure is rare, except in the FC3s motors when pushed to the limit, apprently that oil cooling passage with the thermowax valve/stat is the weak link, out of interest what e-shaft are you using?
I can't really argue with you on this one, your sig says it all, but some of the pics I have seen of collapsed rotors had the apex seals intact, some unfortunate souls found the combustion pressure limit of a rotor face, and they simply collapsed, this is not intrinsic though to rotaries, this also happens in piston engine when the dome is simply not thick enough to with stand the force applied to out, even with perfect combustion, both rotors showed the same destruction in one motor, apparently at 30 psi of boost, but this could also depend on exactly what motor it was, and what generation, the FD stuff looks beefier than the FC stuff...Max
When it comes to high hp turbos you're on your own because no one has written a book mainly becasue most of the stuff is still new and everyday leads to a new discovery.
All the shafts are about the same with the early ones being the strongest. The same goes for the rotors. The 89 + rotors are the weakest mainly because of casting techniques for lightenning purposes from the factory.High boost is not responsible for dented rotors! DETONATION and PRE-IGNITION are. Like I said before I've seen more stock factory motors running stock boost with dented rotors.
The same is true for cracked end housings. There are many instances where people have cracked housings but not apex seals.
crispeed
#24
Originally posted by wankawankel
In that case, is any one interested in tuning a T88 powered FD, with a Power FC for a computer? I have the car running well for daily use, but I blew the motor during the 1320 under 17 psi. Now I have a new stock rebuild, and ready to get those high HP numbers you guys are talking about. Carl...
Any takers?
In that case, is any one interested in tuning a T88 powered FD, with a Power FC for a computer? I have the car running well for daily use, but I blew the motor during the 1320 under 17 psi. Now I have a new stock rebuild, and ready to get those high HP numbers you guys are talking about. Carl...
Any takers?
To get those high hp numbers first you need an ECU that can read above 17.5psi of boost!
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Originally posted by crispeed
The Racing Beat book is good source for begginers and NA stuff.The best book actually written about rotaries was "How To Modify And Race Your Rx-7". That book features info from the gurus like Jim Downing and the Rotary God himself Rick Engman!
When it comes to high hp turbos you're on your own because no one has written a book mainly becasue most of the stuff is still new and everyday leads to a new discovery
The Racing Beat book is good source for begginers and NA stuff.The best book actually written about rotaries was "How To Modify And Race Your Rx-7". That book features info from the gurus like Jim Downing and the Rotary God himself Rick Engman!
When it comes to high hp turbos you're on your own because no one has written a book mainly becasue most of the stuff is still new and everyday leads to a new discovery
Even the Turbo books, mention very little about rotary's and turbocharging, although I did find some very good SAE articles on it at the Library, the retail bookstore stuff, as thick and popular as they may be, are often not much more than a base primer on the aspects of turbocharging and basic combustion theory, its a good starting point, but one often finds themselves in literary pergatory when seeking hardcore info..
ON another note, do you see any increase in rotor blowby with mondo high boost levels, or do the side seal seem to be able to control it well enough, I had heard about some corner seal problems, but the side seals never seem to get mentioned...Max