What kind of mpg can a 13b bridge port get with ITB and fuel injection ? I know that I shouldn't think of fuel consumption with a Bridge port but we are considering fuel injection over a weber carb for a friends rx7 1st gen as he drives it more than once a week.
Thanks

 

it really depends on the ECU and how well you can refine the tune, i've seen some claim over 20mpg still with a bridge but most usually get in the 16-18mpg range on the highway, in town forget about it.

the issue is mainly with the MAP sensor signals being extremely spikey and AFRs all over the place. a carb can do the just as well if you can tune it, i've thrown together a few n/a bridges with holley carbs that ran further on the highway than some of the turbo FI cars.

 

Depending on the weather, 18-29mpg highway. Weather is a very large factor, the hotter it is the better the fuel economy is. I can generally expect 25mpg under normal conditions.

That is highway driving. In city driving, I get maybe 2-5mpg. I do very little city driving so this does not concern me. Cold start and idle are economy killers.

I drive the car maybe 600 miles per week plus regular 500-700 mile weekends, averaging about 20k per year. Fuel economy IS a major concern for me, since the less fuel it uses, the more I get to enjoy the car.

I have a slightly larger than "homologation" bridge port on the secondaries (appears to be the same port window as Racing Beat sells... heck they probably developed it for Mazda ) and due to the tiny primary ports I have to run, the primaries are slightly smaller but the eyebrows are still the full height of the port runner.

My throttle body is an old Holley 750cfm vac-sec carb (the ubiquitous 3310) that I milled the choke horn off of and modified for 1:1 mechanical secondaries. Bodged a TPS from a 2-valve Ford 4.6 on the side where the choke linkage would go. Vacuum signal for the EFI (I run speed-density, not alpha-N) comes from the port under the primary fuel bowl, and the signal is cleaned up with a restrictor orifice I made by gluing a piece of carb cleaner straw into a vacuum connector. It's still a little bouncy but nothing severe. The engine's bouncy anyway

 

A guy on the dodge neon forum had great success using this to get a good vac signal.



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Bridge port owns!