FAST Supercharged 928
07-09-2002, 07:35 PM
#16
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Join Date: Apr 2002
Location: Hobbs, NM (or lovington)
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The problem I have though is the AFM so it would have to be moved in front of the supercharger, like its in front of the turbo on a 944. I have to convert my car to a MAF syStem somehow, and it costs the same for an sds as a ARC2 air fuel controller.
07-09-2002, 08:35 PM
#17
The MAF is better, but you don't have to switch to it from the AFM. You also don't have to move the AFM to the front of the supercharger. I have no idea why so many people think that the AFM won't work with a supercharger blowing through it, but it will. The supercharged '78 I mentioned before uses the stock CIS system, with the AFM in the stock location, has the Vortec supercharger blowing through the AFM with 11 psi of boost, and it works fine.
07-09-2002, 11:31 PM
#19
The same amount of air would be going through it whether it was in front of or behind the supercharger, so why would it make a difference? The car I saw this past weekend didn't have any problem with it being behind the supercharger.
The size of the injectors depends on how much power is going to be made. If you do a web search for "fuel injector size" you'll find information on it. Since fuel injector flow depends on fuel pressure, use information that takes into consideration what your fuel pressure will be. One fuel injector size calculator is at: <a href="http://www.stealth316.com/2-air-fuel-flow.htm" target="_blank">http://www.stealth316.com/2-air-fuel-flow.htm</a>
The size of the injectors depends on how much power is going to be made. If you do a web search for "fuel injector size" you'll find information on it. Since fuel injector flow depends on fuel pressure, use information that takes into consideration what your fuel pressure will be. One fuel injector size calculator is at: <a href="http://www.stealth316.com/2-air-fuel-flow.htm" target="_blank">http://www.stealth316.com/2-air-fuel-flow.htm</a>
07-11-2002, 10:10 PM
#20
Rennlist Member
We have one local whipple charged twin intercooled 5.0 two valve 928 built 6 years ago...
Makes 490ish rwhp, uses a motec and has been running for years, and running hard. I have little doubt hat it could run at that rwhp for one hour straight on a brake dyno.
And another one on the way but at full tilt will generate over 550 rqhp. Again, after market fuel injection supported by our DTA fuel and ignition contrlols. BTW, the first DTA powered 928 will be on display at DEVEK days.
Good luck.
Marc
DEVEK
Makes 490ish rwhp, uses a motec and has been running for years, and running hard. I have little doubt hat it could run at that rwhp for one hour straight on a brake dyno.
And another one on the way but at full tilt will generate over 550 rqhp. Again, after market fuel injection supported by our DTA fuel and ignition contrlols. BTW, the first DTA powered 928 will be on display at DEVEK days.
Good luck.
Marc
DEVEK
07-12-2002, 01:03 AM
#22
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Location: Palo Alto, CA
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Mike:
Generally speaking, you don't want to blow through a AFM because the air coming out of a turbo/supercharger can be very turbulent. AFM's don't accurately read turbulent air, so it should be avoided if possible. Depending on the bost and supercharger design you may or may not feel the difference, but there is a difference.
As an aside, most AFM's have screens or air guides in them. One of the first mods a lot of people do is to pull out the screen (thinking it is just to block debris), or machine out the air guides for more flow. Well, it's all there to "straighten" out the air, so the are diminishing the accuracy.
Abdul
Generally speaking, you don't want to blow through a AFM because the air coming out of a turbo/supercharger can be very turbulent. AFM's don't accurately read turbulent air, so it should be avoided if possible. Depending on the bost and supercharger design you may or may not feel the difference, but there is a difference.
As an aside, most AFM's have screens or air guides in them. One of the first mods a lot of people do is to pull out the screen (thinking it is just to block debris), or machine out the air guides for more flow. Well, it's all there to "straighten" out the air, so the are diminishing the accuracy.
Abdul
07-12-2002, 04:20 AM
#23
I know that it's probably better in most cases to have the AFM before the supercharger, and draw air through it rather than push it through. I was just trying to say that it can work the other way too. I've heard people say that it can't work with an AFM at all, and that isn't true.
Turbulent air can be an issue with both the AFM and MAF. On the 928 supercharger installations that I've seen, where the air is blown through the air measuring device, there has been a fair distance between them. The superchargers were at the front of the engines, and the air measuring devices were at the rear of the engines. This should give air flow that's very turbulent from going through the supercharger some chance to smooth out to a degree. Not the best way to do it in my opinion, or the way that I'd do it, but it can be made to work pretty effectively that way.
Turbulent air can be an issue with both the AFM and MAF. On the 928 supercharger installations that I've seen, where the air is blown through the air measuring device, there has been a fair distance between them. The superchargers were at the front of the engines, and the air measuring devices were at the rear of the engines. This should give air flow that's very turbulent from going through the supercharger some chance to smooth out to a degree. Not the best way to do it in my opinion, or the way that I'd do it, but it can be made to work pretty effectively that way.
