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FM O2 signal modifier

FM O2 signal modifier
FM O2 signal modifier
Prevents the stock ECU from pulling fuel under boost.

Exclusive to Flyin' Miata

Availability: In stock



A stock ECU can pull over 30% of its fuel if it thinks the engine is running rich. The actual amount depends on the model of car. This is a problem when you have a boosted car and you`re trying to deliver more fuel. At best, this means poor driveability until the computer goes into open loop mode. At worst, it can have catastrophic and expensive results. The signal modifier prevents the ECU from seeing a rich condition under boost. Simple installation and no effects when the car is not generating boost. Actually, we recently redesigned it for better reliability, easier installation and a smaller footprint!

A popular addition to cars equipped with Powercard fuel management as this solves a characteristic lean mixture at part throttle. Not needed for the Voodoo Box.

Also very useful for Mazdaspeed MX-5 turbo cars with aftermarket intakes. This helps solve a characteristic hesitation problem that appears when the car spools up faster than stock.

Intended for use only with stock ECU. Not required for cars with full replacement ECUs such as the Hydra Nemesis, FM221 or Megasquirt. If you have a "narrowband" A/F meter that uses the stock O2 sensor, it will read incorrectly when you are in boost - well, more so than usual. Sorry, the little baby Miata is not included.

 Please note that we cannot ship this product to California as it will not meet emissions regulations.

Additional Information

Additional Information

Part number 07-46300
Fits: 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004 (non-MSM), 2005 (non-MSM), MSM, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
Manufacturer Flyin' Miata
Flyin' Miata exclusive Yes
Fits Exocet? Yes
Proposition 65 Warning: Cancer and reproductive harm
California emissions Not emissions legal in California

Customer Reviews 8 item(s)

2nd best thing I've ever bought for my Miata
I was on the fence about buying this because another reviewer didn't have luck using the O2 modifier in conjunction with his FFS PC Pros. I'm glad I bought it though, my experience differs greatly.

The O2 modifier not only completely eliminated the lean tip that I occasionally experienced (maybe 1 out of 5 WOT accelerations), but the throttle response has been improved to a degree I did not believe possible.

I have a 2004 with an FFS kit and PC Pros, I understand that it can be very difficult to tune out lean tip in with the NB2 ECUs, but FM's O2 modifier is the ticket. I am so happy with this product.
Review by Spurius Maelius / (Posted on 6/23/2020)
FFS Powercard fix, no dice.
Didn't work for me, used in conjunction with FFS powercards to try and fix a lean TPS blip, tried everything, no difference.

Note from FM: There is no reason why the signal modifier would not work with a powercard, but if there are other reasons for a lean condition on a throttle blip it may not solve those problems.
Review by Andre / (Posted on 11/13/2019)
Works as claimed. Helped with tuning consistency.
And Im running a boosted 1995 Ford (Mazada) Escort!
Review by Heyoldguy2002 / (Posted on 7/7/2019)
Pleasantly surprised
Say goodbye to the dreaded bog
Review by Josh / (Posted on 5/9/2019)
Didn’t work
Did absolutely nothing no matter what I adjusted it to. This has also been the case for a lot of other users. Skip this for a real ECU and tune

Note from FM: A real ECU is a good option, but it's not always an option.
Review by Alex / (Posted on 5/13/2018)
I love this product!
I received this piece from purchasing the FM MSM Intake Kit, and I am really happy with the results. I was a little bit lazy in the beginning, because after the intake installation, I just truely forgot and put it aside until now. The MSM has the NOTORIOUS boost hesitation, but once I installed this to my car (Stock ECU), my car was not hesitating AT ALL. This piece is pricey to purchase on it's own, but I believe for the price you're paying for, it is really such a great deal!
Review by Sam / (Posted on 3/4/2018)
Very low hysteresis O2 signal modifier.
It's functionally similar to the older version that used a Hobbs switch with a 0.3v reference generator, but this one has hysteresis so small that it's practically unmeasureable. So you get consistent results whether you're rolling into or out of the throttle. However, as with the Hobbs switch version, the diaphragm is limited to one bar of boost.
Review by Ray / (Posted on 1/25/2018)
Too expensive.
Buddy.... 129 dollars? Its literally just a pressure switch. I dont wanna be rude but......

Note from FM: It's not just a pressure switch. It's a custom made electronic controller that alters the signal from the O2 sensor. There's a pressure sensor as part of it and it's integrated into a single component, but it's not just a pressure switch. If you try to replace this item with a simple switch, you will get errors due to a missing O2 sensor signal.
Review by Lolo / (Posted on 6/1/2017)
Click here for instructions for this part.

Why stop here? Consider this upgrade.