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Have fun, JR |
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CIS is more environmentally friendly than MFI and meets later, more stringent emissions stds. EFI is much better than either in that regard.
CIS is also gives much better fuel economy. CIS was a significant advance when first introduced by Bosch for the technology extant at the time in terms of fuel mileage. If (for some reason) you have an old Volvo and want to keep it stock (period correct) then CIS is the way to go. CIS is not a good choice for a sports car* and I'm told it is more susceptible to EtOH fuel problems than MFI, EFI or carbs. MFI is a period-correct, concoursmobile correct performance injection system. Direct injection is top dawg right now, but for the best performance on our old air colled motors, just take a wad of $10,000 bills to Motec and PMO. * yes, MFI is derived from a diesel tractor system, and yet somehow... |
Nobody mentions one of the biggest feats of MFI:
MFI has the best throttle response money can buy in terms of classic 911 engines. "money can buy" is pun intended, because it's more expensive to get a non or poor running mfi injection to work, if the pump is out of wack, it's probably going to get costly.. whereas CIS will probably work out cheaper...afterall, CIS was the mass production thing, it was not about performance, at all. |
Why is this in OT?
It should be in PARF! The MFI people are religious fanatics! reporting to the mods :mad: |
Oh, and MFI sounds better then anything else.
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CIS was good enough that Porsche used it for the 930s entire run and into the '90s, well after everything else in their lineup was using motronic.
That seems like a pretty good endorsement to me. |
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I agree electronic, direct fuel injection is best. |
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we know they were way short on $$ during that time period |
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However, MFI injects fuel only into the cylinder that needs it. Have you ever studied the inner workings of an MFI pump? They have a cam like the cam actuating the intake and exhaust valves. These push plungers in the right sequence and at the right time to increase the pressure in the fuel lines to overcome the MFI injector's spring loaded valve and spray fuel just in front of the intake port. Then there is the 3D space cam that works with the flyweights and throttle position and barometric compensator and the thermostat to change the fuel delivery based on load, engine speed, air pressure, etc. |
= meets later, more stringent emissions stds, Flieger
improved fuel economy also translates directly into lower CO@ emissions, tho that danger was not well appreciated at the time I thought you were an engineering student - has this not been covered in the curriculum anywhere? |
My BMW is pretty dirty. It just squeaks by 1983 emissions but I am not allowed to improve the fuel injection by California law. I wouldn't say CIS is doing it any favors.
That is why I was talking about the speed of the cars. If you drive a car hard you will use more energy and so more fuel. CIS cars are tuned pretty anemic, so they can't go so fast (accelerate as hard). I venture that since MFI has much more precise fuel control as far as pulsed injection that MFI has lower brake specific fuel consumption. I think the oil and stuff old cars burns is probably more polluting than the part of the exhaust that is actually combustion products. |
the oil and stuff old cars burn = gross polluters
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And, if you look at the BSFC curves, CIS cars yielded 20% better numbers, give or take. Cheers, JR |
Whatever. I can't convince you to mend your CIS ways so I will continue having fun in the MFI 911 which is so much more fun than the CIS BMW. Idles better, better throttle response, doesn't stink like fuel.
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In seriousness, though, you should check out how MFI works. It is basically EFI done mechanically. The space cam is the fuel map and there are various sensors that input into the MFI pump which can be seen as a sort of mechanical computer.
Actually, some EFI systems and ignition systems do not differentiate between cylinders like MFI does. Throttle body injection, wasted spark. MFI is quite sophisticated. My thoughts on the MFI to CIS transition was cost and ease of setup. I see no reason why properly tuned MFI needs to waste more fuel than CIS. |
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Why is this in the OT forum? the subject has been discussed ad infinitum on the 911 BBS since 1999. David E. Clark even consolidated the thread into one massive thread.
Come on, let's discuss something interesting like hookers and blow, legs and butts. |
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