Miata scroll supercharger (homemade setup)
#21
That 30 degrees absolutely DOES matter, because the intercooler works the same way as the compressor (given identical conditions), only cooling the air X total number of degrees, so if the compressor outlet temp is 30 degrees cooler, the intercooler outlet temp will be 30 degrees cooler.
This is assuming that the intercooler isn't over sized for the application and that the charge isn't approaching ambient temp already. If you're already approaching ambient IATs, obviously you're not going to see a drastic temp drop. I'm in no way saying that OP shouldn't duct his intercooler/ rad. Merely pointing out that it's foolish to say that drawing cooler air doesn't have an effect on IATs.
This is assuming that the intercooler isn't over sized for the application and that the charge isn't approaching ambient temp already. If you're already approaching ambient IATs, obviously you're not going to see a drastic temp drop. I'm in no way saying that OP shouldn't duct his intercooler/ rad. Merely pointing out that it's foolish to say that drawing cooler air doesn't have an effect on IATs.
#24
Colder air before the supercharger will have a direct effect on the air coming out. This is for a turbo but it's pretty much the same deal.
Tout = (Tin + Tin x [-1+(Pout/Pin)0.263]) / efficiency
Tin: temperature before compressor (In Rankin)
Tout: temprature coming out of the compressor (in Rankin)
Pin: pressure in (asbolute, in psi. ~14.7 psi)
Pout: pressure out (absolute, in psi. ~14.7+boost, ~25.2 in this case)
efficiency: I don't know the % for these, say 0.6
For my turbo setup, at 10C in, out at 54.5C. At 40C in, out at 89.3C. So delta in, 30. Delta out 34.8C. The lower the efficiency, the higher the "out" delta becomes.
So cool air intake doesn't matter, or does it ?
Tout = (Tin + Tin x [-1+(Pout/Pin)0.263]) / efficiency
Tin: temperature before compressor (In Rankin)
Tout: temprature coming out of the compressor (in Rankin)
Pin: pressure in (asbolute, in psi. ~14.7 psi)
Pout: pressure out (absolute, in psi. ~14.7+boost, ~25.2 in this case)
efficiency: I don't know the % for these, say 0.6
For my turbo setup, at 10C in, out at 54.5C. At 40C in, out at 89.3C. So delta in, 30. Delta out 34.8C. The lower the efficiency, the higher the "out" delta becomes.
So cool air intake doesn't matter, or does it ?
#27
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Ambient temps of 77 and IAT of 210. Lets assume the temps at compressor inlet were elevated quite a bit by being drawn from inside the bay, like perhaps 100 degrees?
10.5 psi of boost
77 F = 298 K
100 F = 305 K
210 F = 372 K
((25.2psi / 14.7psi)^0.2857)-1
__________________________ = 84.9%
(372K / 311K)-1
((25.2psi / 14.7psi)^0.2857)-1
__________________________ = 84.9%
(xK / 298K)-1
x=356.435
So if you were to get the compressor inlet temp down to ambient (77F or 298K) you would be rewarded by having the compressor outlet temps drop to 356K, or 181 degrees Fahrenheit.
Thats a 29 degree drop in temp at the outlet from a 23 degree drop in temp at the inlet
10.5 psi of boost
77 F = 298 K
100 F = 305 K
210 F = 372 K
((25.2psi / 14.7psi)^0.2857)-1
__________________________ = 84.9%
(372K / 311K)-1
((25.2psi / 14.7psi)^0.2857)-1
__________________________ = 84.9%
(xK / 298K)-1
x=356.435
So if you were to get the compressor inlet temp down to ambient (77F or 298K) you would be rewarded by having the compressor outlet temps drop to 356K, or 181 degrees Fahrenheit.
Thats a 29 degree drop in temp at the outlet from a 23 degree drop in temp at the inlet
#29
Thanks guys for debating
Form my point:
-CAI is not enough efficient to drop down the air temp entering in the engine. That's why IC must be installed.
But,
-feed the supercharger with fresh air (high O2 concentration)will give you hot air with high O2 concentration at the oulet and give you a better efficient supercharger.
Actually, my air filter takes underhood air (so, more than ambient, maybe more than 100°F) :(
IC + CAI, is the dream team to give a good gain of horsepower.
I will need bigger injectors to follow the gain of O2 entering in combustion chamber.
I planning on 600cc running E85, sounds good?
Form my point:
-CAI is not enough efficient to drop down the air temp entering in the engine. That's why IC must be installed.
But,
-feed the supercharger with fresh air (high O2 concentration)will give you hot air with high O2 concentration at the oulet and give you a better efficient supercharger.
Actually, my air filter takes underhood air (so, more than ambient, maybe more than 100°F) :(
IC + CAI, is the dream team to give a good gain of horsepower.
I will need bigger injectors to follow the gain of O2 entering in combustion chamber.
I planning on 600cc running E85, sounds good?
Last edited by phenixmt; 10-18-2011 at 03:57 AM.
#31
The new setup looks good. Just don't forget the sealed ducting as has been previously mentioned, which ought to begin inside the bumper cover mouth and extend to the radiator to be effective.
As for E85, yes, 600cc injectors ought to be enough to handle it with your setup. However, I have no idea how much airflow that supercharger can produce (and can't find it in a quick search), so what you need to do is some math related to actual airflow you are measuring vs fuel needed to support it. Here is a handy rule-of-thumb list that can help you see some injector sizes and what they can theoretically support in terms of airflow in lb/min. Do keep in mind that when you use E85, you'll also need to increase your fuel pump capacity by up to 30% just to maintain current power levels without running too lean.
As for E85, yes, 600cc injectors ought to be enough to handle it with your setup. However, I have no idea how much airflow that supercharger can produce (and can't find it in a quick search), so what you need to do is some math related to actual airflow you are measuring vs fuel needed to support it. Here is a handy rule-of-thumb list that can help you see some injector sizes and what they can theoretically support in terms of airflow in lb/min. Do keep in mind that when you use E85, you'll also need to increase your fuel pump capacity by up to 30% just to maintain current power levels without running too lean.
#38
Hi everyone,
I have goal in sight :
Last things are done, I think I'm gonna stay with this setup.
I have a ride last sunday. Results of the FMIC was there!
In full throttle from 3500rpm to 4500rpm:
Manifold air temp was 64°F (Unfortunatly, I didn't remember the outside air temp)
Boost was at a constant 8 psi
I'm pretty satisfied of the results.
I'm gonna rebuild my B6 this winter and then I will go further in rpm.
I have goal in sight :
Last things are done, I think I'm gonna stay with this setup.
I have a ride last sunday. Results of the FMIC was there!
In full throttle from 3500rpm to 4500rpm:
Manifold air temp was 64°F (Unfortunatly, I didn't remember the outside air temp)
Boost was at a constant 8 psi
I'm pretty satisfied of the results.
I'm gonna rebuild my B6 this winter and then I will go further in rpm.