Procharger FMU for 99 LS1???
#1
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My 99 LS1 engine has a returnless fuel system. Can someone explain how the Procharger FMU works on a returnless system? Boost closes the return line flow which in turn increases fuel pressure. So, how does the FMU keep fuel from returning to the tank on a returnless system? What am I missing?
#2
8 Second Club
iTrader: (34)
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The ATI setup gives you a braided return line to add to the car and an adapter to go by the fuel filter to hook it in. It pinches off the return pre-regulator. The very first kit I bought, one of the first ATI LS1 F-body kits, had the FMU and an inline boost pump (some kind of bosch pump). After having little luck with the FMU I swapped to 38lb injectors/MAFT (LS1 edit didnt exist at the time) and was able to get the car to run pretty well. Best ET/mph with the FMU was 11.7 @ 109 and with the bigger injectors/MAFT tuning it ran 11.30s @ 120 - wasnt bad for 2001 ![Winky](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_wink.gif)
Anyhow, avoid using the FMU over 5psi, plenty of good tuning solutions out there these days.
![Winky](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_wink.gif)
Anyhow, avoid using the FMU over 5psi, plenty of good tuning solutions out there these days.
#3
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I agree with KP, don't waste your time with an FMU. Larger SVO 42 lb fuel injectors, combined with a larger fuel pump and a good tune is the best way to go for your Miata. Bob
#5
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Thanks guys,
I had found a re-built Procharger head unit & was looking into fueling options. Found the FMU set-up on their web site & wondered about it. Am trying to avoid installing injectors because of already doing it once before to fuel the head/cam. Will probably wait until the 4L60E goes out before doing anything & then install the head unit w/ injectors & a new transmission. Thanks again for the information.
I had found a re-built Procharger head unit & was looking into fueling options. Found the FMU set-up on their web site & wondered about it. Am trying to avoid installing injectors because of already doing it once before to fuel the head/cam. Will probably wait until the 4L60E goes out before doing anything & then install the head unit w/ injectors & a new transmission. Thanks again for the information.
![Happy](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_stretch.gif)