what does it take to push 10 grand redline
11-17-06, 10:40 AM
#26
There are a few notable exceptions, but the kind of porting it takes to get power at those rpms are usually reserved for racing. It will generally not have much usable low end, thus making it not a very good street car. If you actually want to build a bridge ported NA for the street, then thats great and more power to you (I would if I had the time and money) but it seems like this guy is just wanting to get 10k for the sake of running at 10k, which is stupid IMO.
Also, don't you you have ITB's? Thats part of why your engine goes as high as it does.
Also, don't you you have ITB's? Thats part of why your engine goes as high as it does.
11-17-06, 10:56 AM
#27
The mystery of the prize.
Originally Posted by Sideways7
Also, don't you you have ITB's? Thats part of why your engine goes as high as it does.
yes, I have 48mm throttles.... it was part of the process of getting it to make good power at high rpm, shorter intake and better flow. I did mention paying attention to the intake tract in my earlier post
it just seemed like you were saying 10,000+ rpm has no place on the street, and i drive vehicles on the street all the time at > 14,000 rpm and it's terrific!
I'm surprised more people don't just slap bike throtles and a megasquirt on their 6 port motors... the outcome can't be far off from what I have right now, hell might even turn out better with 4 throttles, one per side housing...
11-17-06, 11:04 AM
#28
Originally Posted by pengarufoo
i drive vehicles on the street all the time at > 14,000 rpm and it's terrific!
Anyway, its not that 10k has no place on the street, its just that what it takes to make it useful makes the car not very good on the street. To actually make good power at 10k you really do need a bridgeport, which will lower the low end power and hurt around town driveability.
For some people this doesn't matter, but basically anyone that starts a "I want to rev super high" thread is just doing it because its cool and they don't know what it actually entails. Its one of those "if you have to ask you shouldn't do it" kinda things.
11-17-06, 11:09 AM
#29
The mystery of the prize.
Originally Posted by Sideways7
Motorcycles dont count!
Anyway, its not that 10k has no place on the street, its just that what it takes to make it useful makes the car not very good on the street. To actually make good power at 10k you really do need a bridgeport, which will lower the low end power and hurt around town driveability.
For some people this doesn't matter, but basically anyone that starts a "I want to rev super high" thread is just doing it because its cool and they don't know what it actually entails. Its one of those "if you have to ask you shouldn't do it" kinda things.
Anyway, its not that 10k has no place on the street, its just that what it takes to make it useful makes the car not very good on the street. To actually make good power at 10k you really do need a bridgeport, which will lower the low end power and hurt around town driveability.
For some people this doesn't matter, but basically anyone that starts a "I want to rev super high" thread is just doing it because its cool and they don't know what it actually entails. Its one of those "if you have to ask you shouldn't do it" kinda things.
but there are tricks to make motors tuned to have good VE at very high rpms have good tractabilty at lower rpms for street use... butterfly valves in the exhaust comes to mind as one very simple approach to the problem, and it's used by high-end sport cars and bikes alike. When vehicles like these get tracked, all that nonsense gets ripped off due ot the additional weight they add, but the gain makes it worth having that weight when you street it.
a system built like this obviously isnt going ot make great power outside of the range that is 'on cam' but as long as it's docile, smooth, and has good tractability outside that range it's still perfectly fine for street/traffic use... and when the revs get 'on cam' it will turn into a monster.
11-17-06, 11:15 AM
#30
Yeah, I guess there are ways of making them useful for street driving. I honestly don't know much about that side of things, though. The only bridge ported ones I've been in were pretty twitchy around town, but it was track-optimized. I can deal with low power, but the way it drove was what got to me.
11-17-06, 03:54 PM
#33
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ok from what yall are sayin though is that better than pushin 10,000 redline i should go for more around 9,000 an try more for the hp an torque to go with it then?
11-17-06, 04:21 PM
#34
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Just a question I had I duno if it helps the post or not but, since the E shaft turns 3 times for every one rotor rotation doesn't that mean at 10k RPM the E-shaft will be spinning at 30k RPM? I'm not sure if I have that right or not since I don't know where the tach reads it's signal from. I figure since this is related I might be able to get away without starting a new thread. I would post a silly thing like I have 10k RPM redline right here --------------10,000RPM ------------------- But that may get deleted. I too would like to see someone homebrew a +10k rpm rotary.
11-17-06, 04:28 PM
#35
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Why are you even so worried about redline anyway? Just build an engine for the factory redline and you'll be fine...
Engine speed is measured at the eccentric shaft.
Just a question I had I duno if it helps the post or not but, since the E shaft turns 3 times for every one rotor rotation doesn't that mean at 10k RPM the E-shaft will be spinning at 30k RPM? I'm not sure if I have that right or not since I don't know where the tach reads it's signal from. I figure since this is related I might be able to get away without starting a new thread. I would post a silly thing like I have 10k RPM redline right here --------------10,000RPM ------------------- But that may get deleted. I too would like to see someone homebrew a +10k rpm rotary.
11-17-06, 05:16 PM
#36
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Nobody has mentioned a feature the rotary posseses that no piston engine does and no race engine needs: aux ports.
There has been one or two ppl who have mentioned or contacted me about doing a streetport with a aux bridge and still keeping the sleeves functional which would allow more top end without sacrificing the bottom. Of coarse I have not seen any dyno results either and the sleeves look to be very restrictive compared to the size of the open port. Just estimating from other stuff I've flowbenched I don't think they could flow more than 75-100 cfm with the sleeves in which would probably limit the potential gains to about 20 hp per rotor. All hypothetically speaking of coarse, I'm also ignoring the relevance on why this post started.
I think the 10k number is highly over rated and thrown out there just to shoot down the idea. Yea if you payed someone else to the whole project for you probably but if you have any real knowledge or skills and planned things out I think you can do it fairly easily for 5k or less.
There has been one or two ppl who have mentioned or contacted me about doing a streetport with a aux bridge and still keeping the sleeves functional which would allow more top end without sacrificing the bottom. Of coarse I have not seen any dyno results either and the sleeves look to be very restrictive compared to the size of the open port. Just estimating from other stuff I've flowbenched I don't think they could flow more than 75-100 cfm with the sleeves in which would probably limit the potential gains to about 20 hp per rotor. All hypothetically speaking of coarse, I'm also ignoring the relevance on why this post started.
I think the 10k number is highly over rated and thrown out there just to shoot down the idea. Yea if you payed someone else to the whole project for you probably but if you have any real knowledge or skills and planned things out I think you can do it fairly easily for 5k or less.
11-17-06, 05:26 PM
#37
Also, I'm pretty sure that the rotor turns 2 times for every 3 turns of the e-shaft, so at 9k, the rotors would be at 6k.
Now, to answer the original poster's most recent question, my advice to you would be to get a good street port, s5 rotors, and keep the s4 lim and TB (to keep the aux ports and mech. omp functioning) but use the s5 UIM. This will get you the maximum power attainable with the stock ECU. I'd say you might be able to hit 160-170 at the wheels if the housings are in good condition. Later on you could megasquirt it and maybe hit 180-190 with a good tune. Thats pretty much the limit of the NA engine without radical porting (bridge/peripheral) or an expensive ITB setup.
Edit: You could also bridge the aux port to get a little more power, but I have no experience with that.
Now, to answer the original poster's most recent question, my advice to you would be to get a good street port, s5 rotors, and keep the s4 lim and TB (to keep the aux ports and mech. omp functioning) but use the s5 UIM. This will get you the maximum power attainable with the stock ECU. I'd say you might be able to hit 160-170 at the wheels if the housings are in good condition. Later on you could megasquirt it and maybe hit 180-190 with a good tune. Thats pretty much the limit of the NA engine without radical porting (bridge/peripheral) or an expensive ITB setup.
Edit: You could also bridge the aux port to get a little more power, but I have no experience with that.
11-17-06, 07:40 PM
#38
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To answer the question of how SCCA RX7 RACER revs to 9000rpm on the stock ECU, well he doesn't, he's got a Megasquirt, as can be evidenced by his posts in that subforum.
11-17-06, 08:53 PM
#39
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Originally Posted by gus5891
i just want to be able to have one of the most badass 7's in town an be able to challenge just about anything an give it a run for its money
-Ted
11-17-06, 08:54 PM
#40
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Originally Posted by Sideways7
Also, I'm pretty sure that the rotor turns 2 times for every 3 turns of the e-shaft, so at 9k, the rotors would be at 6k.
Tach RPM's is eccentric shaft RPM's.
BUT...the rotors do spin at 1/3rd the speed of the eccentric shaft...
Thus, at 9kRPM...the e-shaft is spinning at 9kRPM, but the rotors each spin at only 3kRPM.
-Ted
11-17-06, 08:55 PM
#41
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Originally Posted by Black91n/a
To answer the question of how SCCA RX7 RACER revs to 9000rpm on the stock ECU, well he doesn't, he's got a Megasquirt, as can be evidenced by his posts in that subforum.
I don't go into that sub forum... :P
-Ted
11-17-06, 09:14 PM
#42
I know that the tach rpm is the e-shaft rpm, but I swear I read that the rotors make 2 rotations for every 3 of the e-shaft, meaning when the e-shaft is at 9k, the rotors are effectively at 6k. I'll go look it up to see if I can find it.
Edit: Your right. I don't know where I got that idea. This is gonna bother me all night....
Edit: Your right. I don't know where I got that idea. This is gonna bother me all night....
11-17-06, 11:42 PM
#43
this whole omg rotaries rev forever thing is a common misconception
I'm not some kind of expert, but I made 172rwhp in my N/A and it's fully streetable, with power falling off just at 7k. Not too shabby. It's just not worth the insane amount of money work and work to squeeze that extra 20 or 30hp that could be made with more aggressive porting.
Just get a 20B. You can do 500whp on pump gas easily, and it will cost the same amount as trying to make a 2 rotor rev to 10 grand.
I'm not some kind of expert, but I made 172rwhp in my N/A and it's fully streetable, with power falling off just at 7k. Not too shabby. It's just not worth the insane amount of money work and work to squeeze that extra 20 or 30hp that could be made with more aggressive porting.
Just get a 20B. You can do 500whp on pump gas easily, and it will cost the same amount as trying to make a 2 rotor rev to 10 grand.
11-18-06, 05:22 PM
#44
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ok well i have an s5 engine in my shed will all its internals just fix right into my s4 or are there some mods needed to do this? also by puttin the s5 internals in my s4 this will up my redline to 8,000 correct?
11-18-06, 06:52 PM
#45
The s5 internals will fit into the s4 engine without a problem. You need to make sure that you use the s5 rear counterweight (or s5 flywheel), though. To get the same power band as an s5 you will also need to use the s5 intake. The VID is part of what raises the powerband, nbot just the higher compression rotors alone.
11-18-06, 07:00 PM
#46
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Originally Posted by arghx
this whole omg rotaries rev forever thing is a common misconception
It's just not worth the insane amount of money work and work to squeeze that extra 20 or 30hp that could be made with more aggressive porting.
Just get a 20B. You can do 500whp on pump gas easily, and it will cost the same amount as trying to make a 2 rotor rev to 10 grand.
It's just not worth the insane amount of money work and work to squeeze that extra 20 or 30hp that could be made with more aggressive porting.
Just get a 20B. You can do 500whp on pump gas easily, and it will cost the same amount as trying to make a 2 rotor rev to 10 grand.
Ok, somebody explain this "INSANE amount of money bit" and how in the heck putting in a 20B will be just as cost effective...? I'm pretty sure that the build I'm doing will stay together at 10k just fine, not sure if it will make power at that rpm yet. If you put in the cost for all the new seals I'll need from Atkins I'll have right at about 2k into the motor with used TII rotor housings, rx-8 eshaft and stationary gears. I don't know how much someone would charge for building the engine because I'll be doing the port and build work myself. So lets say $3,500 if you pay someone to do the additional port work and engine assembly. I could see it hitting $5k to have a manifold fabbed with a larger throttle body added and doing megasquirt to control it playing your cards right and creatively. Yea that is a crap load of money but your going to spend atleast $3500 for a 20B not including freight, rebuild, fabrication, radiator, EMS, exhaust, custom driveshaft and that is assuming the engine came with a transmission and you are using the stock rear end. Unless you have the ability to do most of the fabrication on your own and don't need to rebuild the engine you are probably looking at double the amount.
Not to sound like the guy who always says strap on a turbo, but it is fairly cost effective over other alternatives and lets face it if you want to play your going pay.
11-18-06, 08:37 PM
#47
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Sorry, as much as this guy is going to end up blowing his engine up anyways, I feel the need to just add to this reply... 
Don't forget the FRONT counterweight too!
Actually, the VDI[sic] has nothing to do with the raised redline.
Compression has nothing to do with it either.
The primary reasons for the higher redline is the lighter rotors and closer tolerance machining of parts in the later model FC's...
-Ted
Originally Posted by Sideways7
The s5 internals will fit into the s4 engine without a problem. You need to make sure that you use the s5 rear counterweight (or s5 flywheel), though.
To get the same power band as an s5 you will also need to use the s5 intake. The VID is part of what raises the powerband, nbot just the higher compression rotors alone.
Compression has nothing to do with it either.
The primary reasons for the higher redline is the lighter rotors and closer tolerance machining of parts in the later model FC's...
-Ted
11-18-06, 11:05 PM
#48
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ok well the s5 intake is already on my s4. how long does the average rebuild take? i'm probaly goin to be doin this in a car port(just switchin the internals for now) an knowin my dad he will start complainin if it aint out of his car port in less than a week. i know times vary greatly dependin on how much time i have but whats the average rebuid time?mainly wonderin if its possible to be a weekend thing
11-18-06, 11:16 PM
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Originally Posted by gus5891
ok i have decided to buy this low milage 7 an rebuild mine as more of a street/drag car. i have heard you car push 10 thousand rpm's out of a rotary i was wonderin what kind of mods have to be done to push this kind of rpms???
11-18-06, 11:17 PM
#50
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If you can do the actual engine work inside in a clean room, you don't want to get bits of dust and dirt in the bearings. If you can't then I wouldn't be rebuilding it if I were you, because it probably won't last.