The New Rx8 Rotors?
12-26-2002, 03:11 PM
#13
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Join Date: Dec 2002
Location: San Diego, CA
Posts: 10
There is a lot that goes into turbocharging other than just compression folks. You also have to think about static compression vs dynamic compression. When the motor is spinning, you never actually get that full 9.5:1 compression because you don't have 100% volumetric efficiency. If you get to 100% volumetric efficiency, then you actually are getting 9.5:1. If you get over 100% then obviously you get over 9.5:1. This is speaking of natural aspiration of course.
With a turbo charger, you also have to think about how much the compression is going to increase with boost on top of higher static compression, and what that will do to increase the probability of knock.
Another thing to think about is this: In a full race turbocharged piston engine, which will always run very high octane fuel, high compression is used to make the engine capable of spooling a larger turbo than a low compression engine of the same displacement. On pump gas, lower compression with a little more boost will make more power reliably than higher compression and lower boost.
While it is true that higher compression will make more power at the same boost level, you are that much closer to the detonation point than you would be with more power at a higher boost level, on lower static compression. I think you guys all should be putting TII rotors in your motors, you already have enough exhaust energy to spool a turbo that is so large that you never get it up into it's peak efficiency island on pump **** anyway...
By the way, hi, I'm new here. :wave:
With a turbo charger, you also have to think about how much the compression is going to increase with boost on top of higher static compression, and what that will do to increase the probability of knock.
Another thing to think about is this: In a full race turbocharged piston engine, which will always run very high octane fuel, high compression is used to make the engine capable of spooling a larger turbo than a low compression engine of the same displacement. On pump gas, lower compression with a little more boost will make more power reliably than higher compression and lower boost.
While it is true that higher compression will make more power at the same boost level, you are that much closer to the detonation point than you would be with more power at a higher boost level, on lower static compression. I think you guys all should be putting TII rotors in your motors, you already have enough exhaust energy to spool a turbo that is so large that you never get it up into it's peak efficiency island on pump **** anyway...
By the way, hi, I'm new here. :wave:
12-28-2002, 01:57 AM
#14
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Join Date: Apr 2002
Location: IL
Posts: 2,930
Originally Posted by 1Revvin7' date='Dec 19 2002, 06:15 PM
[quote name='l8t apex' date='Dec 19 2002, 09:58 AM']While you are correct I beleive the whole concept of turbo is raising compression. Every psi converts over to compression pionts.Static compression ratio of 9.5:1 add 2lbs boost its now compression10.8, 6lbs boost now 13.4 compression. FYI 14lbs boost on static compression of 9.5:1(FD rotors) is now 18.5. I would guess you couldn't or need to boost as high with a higher compression. This is plagerizedfrom Turbo magzine Nov. 1994.
No I'm not Rainman.
No I'm not Rainman.
the problem is the higher the compression inside the motor the more likely you are to preignite/detonate. It's easier to just run low compression rotors and bump up the boost, then cool that compressed (heated) charge with a FMIC then let it go into the engine, you see you don't have anything helping you with cooling the air/fuel mixture when the rotors are compressing it.... you could get into water injection and other things though, but this is a pretty big subject matter.
you certainly can run high boost on high compression, it's just more complicated and risky. but the idea of a high CR turbo rotary makes me moist in the panties, if I had panties it would anyways... there would be more power off boost than with lower compression rotors.
01-04-2003, 01:35 PM
#15
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Join Date: Jul 2002
Posts: 2,315
well i thought that the renesis aquired the relocation of the intake to the top instead right above the exhaust...right? doesn't this affect porting? i mean if the enter and exit points are different would the intake port just move its position or what? and what about the honda 2000? i know it has high *** compression but they do make turbo's for it....how the hell do they make that work? or is it just different with piston engines? damn i need to start learnin more bout the "other" engine
01-04-2003, 01:47 PM
#16
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Join Date: Oct 2001
Location: Peoria, AZ
Posts: 10,906
I don't think the Renesis move the port positions, just went from pp exhaust to side port exhaust. What would happen if you changed where the exhuast or intake ports were? I mean like move the exhaust ports down the side/rotor housings like 2 inches.
01-04-2003, 01:49 PM
#17
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Join Date: Oct 2001
Location: Peoria, AZ
Posts: 10,906
Originally Posted by pengaru' date='Dec 28 2002, 02:57 AM
[quote name='1Revvin7' date='Dec 19 2002, 06:15 PM'] [quote name='l8t apex' date='Dec 19 2002, 09:58 AM']While you are correct I beleive the whole concept of turbo is raising compression. Every psi converts over to compression pionts.Static compression ratio of 9.5:1 add 2lbs boost its now compression10.8, 6lbs boost now 13.4 compression. FYI 14lbs boost on static compression of 9.5:1(FD rotors) is now 18.5. I would guess you couldn't or need to boost as high with a higher compression. This is plagerizedfrom Turbo magzine Nov. 1994.
No I'm not Rainman.
No I'm not Rainman.
the problem is the higher the compression inside the motor the more likely you are to preignite/detonate. It's easier to just run low compression rotors and bump up the boost, then cool that compressed (heated) charge with a FMIC then let it go into the engine, you see you don't have anything helping you with cooling the air/fuel mixture when the rotors are compressing it.... you could get into water injection and other things though, but this is a pretty big subject matter.
you certainly can run high boost on high compression, it's just more complicated and risky. but the idea of a high CR turbo rotary makes me moist in the panties, if I had panties it would anyways... there would be more power off boost than with lower compression rotors. [/quote]
So is boost the same thing as raising the engine's compression? If so i don't understand why you can't just add boost to a higher compression engine. it would be the same thing as adding a lot of boost to a lower compression engine. Right? **** im lost.
01-06-2003, 11:56 PM
#18
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Join Date: Oct 2002
Posts: 378
Originally Posted by 1Revvin7' date='Jan 4 2003, 11:49 AM
[quote name='pengaru' date='Dec 28 2002, 02:57 AM'] [quote name='1Revvin7' date='Dec 19 2002, 06:15 PM'] [quote name='l8t apex' date='Dec 19 2002, 09:58 AM']While you are correct I beleive the whole concept of turbo is raising compression. Every psi converts over to compression pionts.Static compression ratio of 9.5:1 add 2lbs boost its now compression10.8, 6lbs boost now 13.4 compression. FYI 14lbs boost on static compression of 9.5:1(FD rotors) is now 18.5. I would guess you couldn't or need to boost as high with a higher compression. This is plagerizedfrom Turbo magzine Nov. 1994.
No I'm not Rainman.
No I'm not Rainman.
the problem is the higher the compression inside the motor the more likely you are to preignite/detonate. It's easier to just run low compression rotors and bump up the boost, then cool that compressed (heated) charge with a FMIC then let it go into the engine, you see you don't have anything helping you with cooling the air/fuel mixture when the rotors are compressing it.... you could get into water injection and other things though, but this is a pretty big subject matter.
you certainly can run high boost on high compression, it's just more complicated and risky. but the idea of a high CR turbo rotary makes me moist in the panties, if I had panties it would anyways... there would be more power off boost than with lower compression rotors. [/quote]
So is boost the same thing as raising the engine's compression? If so i don't understand why you can't just add boost to a higher compression engine. it would be the same thing as adding a lot of boost to a lower compression engine. Right? **** im lost. [/quote]
im no turbo expert....but the bassis of it...is if you ran turbo on a high compression motor...it would defeat the purpose of it...b/c you couldnt cram as much air/fuel in there....the lower compressoin the more you can cram in there and the turbo becomes effiecitent. You can run a turbo, supercharger, n20 on a crazy comp. motor...but you only could run low boost or low doses of n2o.
01-06-2003, 11:59 PM
#19
Senior Member
Join Date: Oct 2002
Posts: 378
its kinda like...on a boinker motor for example...if you run some domed pistons that are giving you big compression numbers...theres going to be less space between the top of the piston and the cyl. head...givin you higher compression....which also decreases how much boost you can cram in there?
am i wrong??
am i wrong??
