Which intake would show most fuel efficiency gains?

[Frank Lee]

Originally Posted by zonker

this is true, but if the air was forced thru a throttle plate on a fuel injected car, the tps would still read the throttle opening as less than what air the engine is actually getting and deliver less fuel, much in the same way a large vacuum leak would, so you'd have a air/fuel mixture change that would reflect a leaner condition.

This is how DIY turbo kits added to a non-turbo designed motor/ecu contribute to engines that go clunk in the night.

The O2 sensing circuit wouldn't correct?

[Hubert Farnsworth]

Originally Posted by zonker

this is true, but if the air was forced thru a throttle plate on a fuel injected car, the tps would still read the throttle opening as less than what air the engine is actually getting and deliver less fuel, much in the same way a large vacuum leak would, so you'd have a air/fuel mixture change that would reflect a leaner condition.

This is how DIY turbo kits added to a non-turbo designed motor/ecu contribute to engines that go clunk in the night.

granted, you would not need to go thru all that kind of hassle if you just reprogrammed the ecu...

And by running too lean you can guarantee complete combustion for the few cycles it lasts before the temperature and pressure exceed the designed limits of the engine and it fails due to the extremely lean mixture + standard high compression ratio (assuming an n/a engine, and not one modified with a reduced compression ratio + proper air charge cooler/intercooler to help reduce the intake temperatures below that of the base engine.

[zonker]

Originally Posted by Frank Lee

The O2 sensing circuit wouldn't correct?

yes and no... O2 sensors on most cars are narrow band sensors that can only paint part of the picture.

It would however send a signal to the ecu that the car is running lean, and if the condition could not be remedied by an adjustment within the realm of what the ecu deems as acceptable behavior, then it will throw a code and the CEL will light.

And if it's pre 1996 OBD1 electronics, it will put the ECU in closed loop.

[Frank Lee]

I'm thinking it's unlikely for something like a venturi or whatever to generate enough psi for getting outside of the O2's band to be an issue... nowhere near turboing or some such.

[zonker]

it could in theory, or you could do one of those wacky leaf blower superchargers lol.

the thing is, the ecu looks at a variety of sensors to make it;s decision about fuel injector dwell and spark advance, so if one is giving a crazy signal (for example too much air past the throttle body plate), the MAF would register an higher than normal air speed reading as well as the o2 sending a lean signal, so it would probably at that point throw a code saying the tps is out of whack.

newer '96 up obd2 ecu's go one step further and actually to some extent ignore the crazy tps signal and "learn" it out of the equation, while throwing a code for it's signal error as well. thats why on newer cars, you can get a CEL and not notice any change in the way the car runs.

[Frank Lee]

I guess that bridge can be crossed when (if) anyone gets there...

[zonker]

yep - that mod is not on my front burner lol.

so frank, i'll make you a sandwich if you'll help me change out rear ends on the mustang

[Frank Lee]

You will need bacon and mayo if I'm going to drive that far!

[zonker]

ahh - bacon, the fairy dust of foods. put bacon with anything and it's deelish!

BLAT's are my fave (bacon lettuce avocado tomato). helps that were in the avocado capital of the US lol, they're like 15 for 5 bucks here.

[JohnnyRun]

WOW! Thanks guys, I'm just trying to save a few mpg's lol