How many restrictions to exhaust?

[jarred15801]

How many noise or gas restrictions are there on a q45? I have a 97 so i donno if the ehaust is any different from the previous years or not? But to me it looks like there is the suitcase muffler, 2 resonators, and 4 cats. Is that correct?

[maxnix]

Yes, but the "restrictions" are around 2% -3% of air flow. Probably the most restriction is in the headers.

[jarred15801]

Yeah i read that it wasn't a very restrictive exhaust before but just looks real cluttered. There are no after market headers made are there?

[elwesso]

impul apparently makes headers for the Y33 VH41 but they are for RHD cars and stupid expensive. You'd be better off having them custom made. Exhaust modifications wont do you any good unless you want a little bit more noise.

[Q45tech]

The physical FACT to always keep in mind is the farther from the engine [distance] the less important a restriction is!

Exhaust restrictions only reduce power because some old burned gases are not fully purged from cylinder limiting the amount of new fresh air inflow. But the exhaust temperature is so high [1500+F] that this heat expansion pressure overcomes a tremendous amount of backpressure.

Always measure back pressure in front of cats and after cats to get an idea and calculate what improvements can do and cost per HP gained.

On average a mechanical change costs $100 per horsepower gained once you have crossed the built in [designed in safety restrictions].