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Possible obstacles in tuning ITB's for daily driver?

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Re: Possible obstacles in tuning ITB's for daily driver?

Postby PeteD » April 7th, 2018, 6:05 am

Hi & welcome to the forum!

Quinn Kizis is a local (CT) guy who has an ITB car that was really dialed in; I don't have his contact info, but maybe you can find a another forum member to get in touch with him for some 1st-hand advice.

The little I do know about ITBs is theory on how they operate with the ECU. Since there's no intake manifold, there's usually no good (e.g. steady) source of vacuum for the MAP signal to the ECU. As a result, you'll need an ECU that supports Alpha-N (tps-based) control strategy.

This is where the susceptibility to weather and altitude variations can come in. Alpha-N control strategies use throttle-position as an ECU input (along with inputs, like RPM) to estimate how much air is coming in the engine and calculate the amount of fuel to inject. Since there's no direct measurement of incoming air (like there is on speed-density [MAP-based] or mass-air-flow [MAF-based] control strategies) when atmospheric pressure changes, the estimation is less accurate ... and then the fuel calculation becomes less accurate. Resulting in running a bit more rich or a bit more lean, than the day it was tuned. This is quite analogous to how carburetors work (and also their pitfalls).

I don't think there's anything inherent about ITBs that make them illegal for emissions in CT (depending, of course, on the year of your car) ... it will just need to be tuned well enough to meet the tailpipe test.

I think that ITBs would make a really interesting & challenging project to take on. The results - the look, that sound & throttle-response would definitely make it worthwhile in the end! I hope you'll keep us posted as you go ahead on this project!
-- Pete

white '94; 140hp & 122ft*lbs NA --> only memories now
red '93; 143hp & 135ft*lbs SC --> object of affection
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Re: Possible obstacles in tuning ITB's for daily driver?

Postby 3miataFamily » April 10th, 2018, 4:16 pm

Quinn is running a Adaptronics ECU on his ITB 99...no issues..except there is no OBD connectivity...at all.

He just hemmed and hawwed when asked how he gets the 99 registered...

as of right now...94 and older need NO emission test at all...
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