Did a little searching and couldn't find anything in regards to this:

I've seen multiple times, on here and other forums, that ITB's are recommended against for a daily driver. For multiple reasons, mainly that they come out of tune very easily, that they get horrible MPG because of the necessity of running very rich at lower rpms, and of course that they don't make much power for the money unless your set up is highly tuned.

However, there are certain cars that have itb's from the factory. I.E. E39 M5 and E30 M3. I know these engines require more attentive maintenance than the non M non ITB cars, but they still have fairly high service intervals and do not need nearly as much recalibration etc as, per se, a built b series with ITBs.

My question is this: What is the difference between the stock and aftermarket set ups that yields this difference? Why do aftermarket ITBs get such bad gas mileage and need such frequent calibration whereas a stock ITB set up doesn't? Does the greater ease associated with the stock set up have a direct relationship to lower performance gains from having ITB's over a single TB vs aftermarket ITB's over a single TB, all things aside?

None of this affects me in any way as I don't own an N/A car; I was just curious.

Thanks

 

You can get good mileage and reliability if you have them tuned perfectly.

Many cars come from the factory with ITB's. All the M series BMW's, Pulsar SR20's, RB26's, 20v 4AG Toyota motors...

All of these cars are designed and tuned from the factory to run ITB's. They would get bad gas mileage and run shitty if you put an intake manifold and single throttlebody on.

The reason you hear about so many horror stories from people about daily driving ITB's, is that 90% of people with ITB's do not tune them correctly.

 

 

Thanks