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Old 03-02-2011, 09:50 PM   #1
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Default Running lean

I recently picked up a 2000 Miata. It came with a Jackson Racing M45 supercharger, JR Boost Timing Control, an ELF piggyback controller, a BRP 62.5mm pulley on the SC, an upgraded fuel pump (not sure what make/model, I'm basing this on paperwork/emails that came with the car), stock exhaust, and the restrictor pill removed from the fuel line. Car ran like crap.

Took it to a dyno shop (Pruven up in Milford, CT). Even after tweaking the ELF, it is running horribly lean. A/F is over 18 when you get on it, never drops below 15. Uncorrected max 140.43 hp and 116.15 ft-lbs of torque.

Obviously, I need more fuel. The guys at Pruven immediately recommended I install a boost dependent fuel pressure regulator, but I suspect there's something wrong. Pruven didn't measure the fuel pressure at the rail while under boost, which I think should be my next diagnostic step. (Based on some input from the forum, I should be seeing 60psi at the rail even under boost.) ASSuming fuel supply is okay, is there anything else I should be looking at apart from the ELF?

On a side note, I've learned that the '99-'05 Miatas don't have a fuel return line, the pressure regulator is in the back, inside the fuel tank. "Fuel comes from the pump, through the filter, and then to a tee which leads up front to the rail as well as back into the tank and into the regulator. The fuel rail itself is a dead-end, with no return line." Folks on forum recommend that if I want to add a bdfpr, that I'd need to change it over to a return system; that sound logical?
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Old 03-03-2011, 08:30 AM   #2
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sounds like the typical response. you need to upgrade the fuel pump to a 255HP LPH, toss in larger injectors, and tell the ELF to do something.
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Old 03-04-2011, 12:42 PM   #3
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Can someone please comment on the fuel restrictor pill OP mentions? Is this only on certain models, and where is it located (actual fuel line or vac line to the fpr)? I've never seen this mentioned before in any of my research, and a search didn't turn up any answers on the turbo wiki page.

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