6.97@197mph Sporty Motorsports 13B RX7
11-18-08 | 07:08 PM
#203
So what makes it beneficial to do so much compression of the fluid (air) using a rotodynamic pump, and so little with the positive displacement pump? When you say "Low!" I am guessing somewhere around 7.5:1? And they are running something like 50 psi boost, right?
So that’s a pressure ratio of 3.3:1 as the fluid passes the compressor, then exchanging heat with the intercooler, then pressurizing an additional 7.5:1, making the total compression ratio with respect to atmospheric 25:1 (7.5*3.3=25). Why not just run 12.5:1 compression ratio rotors (if they existed) and a boost pressure of 15psi (PR=2:1). Your air charge would still be 25:1 (12.5*2=25). Or for that matter why not run 25:1 compression ratio rotors with no turbocharger at all. You would no longer build up the total pressure ratio progressively as you wait for the turbo to spool up.
I think I know the answer to these questions, and I think it has to do with adiabatic efficiencies and PV=mRT and the act of INTER-cooling, but I would like to hear other peoples answers.
Also, does anyone know what type of transmission Sporty is using? What engine series?
So that’s a pressure ratio of 3.3:1 as the fluid passes the compressor, then exchanging heat with the intercooler, then pressurizing an additional 7.5:1, making the total compression ratio with respect to atmospheric 25:1 (7.5*3.3=25). Why not just run 12.5:1 compression ratio rotors (if they existed) and a boost pressure of 15psi (PR=2:1). Your air charge would still be 25:1 (12.5*2=25). Or for that matter why not run 25:1 compression ratio rotors with no turbocharger at all. You would no longer build up the total pressure ratio progressively as you wait for the turbo to spool up.
I think I know the answer to these questions, and I think it has to do with adiabatic efficiencies and PV=mRT and the act of INTER-cooling, but I would like to hear other peoples answers.
Also, does anyone know what type of transmission Sporty is using? What engine series?
-J
11-18-08 | 07:17 PM
#204
Joined: Dec 2006
Posts: 1,763
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From: bayamon pr, orlando fl, paterson nj
i think 
11-18-08 | 09:13 PM
#206
Joined: Dec 2006
Posts: 1,763
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From: bayamon pr, orlando fl, paterson nj
11-18-08 | 09:37 PM
#208
InsaneRotaries.com
Joined: Feb 2002
Posts: 2,748
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From: Westchester, NY
I was hoping for some good news.
11-18-08 | 10:16 PM
#215
11-18-08 | 10:39 PM
#217
Joined: Dec 2006
Posts: 1,763
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From: bayamon pr, orlando fl, paterson nj
11-18-08 | 11:17 PM
#218
Full Member
Joined: Apr 2002
Posts: 203
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From: New Zealand
Lower comp = less power all other variables being the same.
These people are only glorified mechanics so you cant expect them to know what they are talking about
let alone explain it to you
I literally laughed my **** off when someone said it has "more volume and hence will make more power"
Does anyone know why the 13B is rated at 654cc? regardless of compression ratio? smart people do, none of them are into drag racing or make products for it
These people are only glorified mechanics so you cant expect them to know what they are talking about
let alone explain it to you I literally laughed my **** off when someone said it has "more volume and hence will make more power"
Does anyone know why the 13B is rated at 654cc? regardless of compression ratio? smart people do, none of them are into drag racing or make products for it Anyway... You get your rotor & lower the compression (by removing material from the rotor face) & do a before & after with your grains of salt or whatever you are using to see how much more air & fuel you can now cram into that chamber you have now enlarged in the rotor face (even more under pressure).
You have taken material out out of the rotor face & Air Fuel mixture will now fill that gap!
Sorry - but thats about as simple as I can get it for you keyboard warriers!! LOL
11-18-08 | 11:56 PM
#219
-in any otto cycle engine, rotary included, the compression is considered adiabatic, meaning no heat exchanged from the gas/air mixture to the surroundings so by the gas equation of state (gas law) since the volume is reduced both temperature and pressure increase.
-the higher the static compression ratio, the higher the temperature and pressure of the mixture at the end of compression
-an external compression device (turbo/sc) followed by an intercooler takes a lot of the heat out of the compressed mixture
-this allows a lower compression engine to achieve the same final compression but at lower temperatures and pressures compared to the higher compression engine
-lower temps and pressures make tuning better/easier (reduce detonation)
makes sense?
-the higher the static compression ratio, the higher the temperature and pressure of the mixture at the end of compression
-an external compression device (turbo/sc) followed by an intercooler takes a lot of the heat out of the compressed mixture
-this allows a lower compression engine to achieve the same final compression but at lower temperatures and pressures compared to the higher compression engine
-lower temps and pressures make tuning better/easier (reduce detonation)
makes sense?
Last edited by neit_jnf; 11-18-08 at 11:58 PM.
,
11-19-08 | 04:13 AM
#221
Banned. I got OWNED!!!
Joined: Apr 2008
Posts: 114
Likes: 0
From: Australia
It does sound like pete! Except he would have said a 13b is rated at 2600cc... LOL
Anyway... You get your rotor & lower the compression (by removing material from the rotor face) & do a before & after with your grains of salt or whatever you are using to see how much more air & fuel you can now cram into that chamber you have now enlarged in the rotor face (even more under pressure).
You have taken material out out of the rotor face & Air Fuel mixture will now fill that gap!
Sorry - but thats about as simple as I can get it for you keyboard warriers!! LOL
Anyway... You get your rotor & lower the compression (by removing material from the rotor face) & do a before & after with your grains of salt or whatever you are using to see how much more air & fuel you can now cram into that chamber you have now enlarged in the rotor face (even more under pressure).
You have taken material out out of the rotor face & Air Fuel mixture will now fill that gap!
Sorry - but thats about as simple as I can get it for you keyboard warriers!! LOL
11-19-08 | 11:47 AM
#222
Full Member
Joined: Nov 2007
Posts: 103
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From: Dearborn, MI
Are you for real?? How sure are you about your mathematics and theory? I'll bet you're not sure enough to build it. And I bet you're not sure enough to build it and then compete in the same series that sporty races..... Why? Because you wouldn't be competitve....at all. You're missing a few big things in your thinking......oh but I'm sure you knew that and you just wanted to see what everyone else had to say huh?
-J
-J
The only math “theory” I went into was multiplying compression ratios, and I'm pretty sure my multiplication is correct. I also mentioned the equation PV=mRT, which is in fact a real equation many people would recognize.
"you're not sure enough to build it"
Build what, my hypothetical 25:1 compression ratio engine? No I don't currently have the tooling to build those rotors, nor would I want to. Although I’m still not clear about what I am supposed to be “sure enough” of.
"...then compete in the same series..."
I didn't mention anything about competition.
Regarding the remainder of your post after that point...
Do you talk to people in real life like this?
11-19-08 | 07:31 PM
#223
"How sure are you about your math theory?"
The only math “theory” I went into was multiplying compression ratios, and I'm pretty sure my multiplication is correct. I also mentioned the equation PV=mRT, which is in fact a real equation many people would recognize.
"you're not sure enough to build it"
Build what, my hypothetical 25:1 compression ratio engine? No I don't currently have the tooling to build those rotors, nor would I want to. Although I’m still not clear about what I am supposed to be “sure enough” of.
"...then compete in the same series..."
I didn't mention anything about competition.
Regarding the remainder of your post after that point...
Do you talk to people in real life like this?
The only math “theory” I went into was multiplying compression ratios, and I'm pretty sure my multiplication is correct. I also mentioned the equation PV=mRT, which is in fact a real equation many people would recognize.
"you're not sure enough to build it"
Build what, my hypothetical 25:1 compression ratio engine? No I don't currently have the tooling to build those rotors, nor would I want to. Although I’m still not clear about what I am supposed to be “sure enough” of.
"...then compete in the same series..."
I didn't mention anything about competition.
Regarding the remainder of your post after that point...
Do you talk to people in real life like this?
My point is, the reason you wouldn't build it "nor would you want to" is that it's pointless to do so and be competitive on sportys level.
The reason I compared the two engines and being competitive is because YOU said you don't see the point in running all that boost when all you have to do is raise the compression ratio of the rotors and you'll get the same resualt. And I'm telling you you're wrong.
This isn't "real life"? Huh....strange...I'm pretty sure I'm sitting here at my REAL shop sitting at my REAL desk typing this on my REAL laptop.
-J
11-19-08 | 07:52 PM
#224
Banned. I got OWNED!!!
Joined: Apr 2008
Posts: 114
Likes: 0
From: Australia
Imagine the "Displacement" on 2:1 compression ratio
^ More CC's yo !
*dumb *****
You know that for the retarded there is Internetz yo! and you can make up for your lack of formal qualifications by reading what some geek has copied and pasted from actual people with qualifications and brains
Reducing compression ratio dose not increase performance due to "increased volume" yo! only a total ******* retarded **** with no education would type that ****, let alone say it to anyone who has a basic education or understanding of mechanical engineering.
^ More CC's yo !
*dumb *****
You know that for the retarded there is Internetz yo! and you can make up for your lack of formal qualifications by reading what some geek has copied and pasted from actual people with qualifications and brains
Reducing compression ratio dose not increase performance due to "increased volume" yo! only a total ******* retarded **** with no education would type that ****, let alone say it to anyone who has a basic education or understanding of mechanical engineering.