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School me on intercooler piping

Kombi said:
I think the calculation of 74ms and-you're-done is likely to be misleading here, what you've calculated is the time it takes an engine at WOT to evacuate a given volume. If the difference between the two pipe sizes was observable to the butt-dyno it would be most noticeable coming into throttle, coming into boost. You would need to calculate how long it takes the turbo to increase the two differently-sized intake tracts from off-throttle pressure to the target boost pressure, while the turbo's spooling up, and while there's air leaving the tract through the intake ports at a rate proportional to tract pressure.
Click to expand...

The time difference for filling the volume at 2" vs. 3" will also be a small fraction of a second. You can do the math using the same method I used above to see that.

Yes I did the calc at WOT / peak power but also assuming 10 feet of piping which is likely an overestimate. Without real data from the engine in question you can't calculate the exact time difference - just illustrating a point here.

Of course you should also include the intercooler volume if you want to know the absolute amount of time at a given airflow but assuming that stays constant, you can pull it out of the comparison.

The major two contributors to transient response (aka spool-up time) going from part-throttle to WOT are...

-Turbo rotor group inertia
-Turbine efficiency

And they both have equally significant and noticeable effect on the drivability and feel of the car. Time required to fill the intake tract is small potatoes in comparison.
 
mrjaybeeze said:
Hi

Another issue with smaller diameter piping is the velocity of the air inside the intercooler piping.
It should give you a little hint, the fact that Volvo chose pretty large pipes even if the stock power levels of the 230FT even are modest by todays standards....:roll:

YS
Jaybee
Click to expand...

This is true; one of the main parameters when choosing charge air tubing size is flow velocity. One target range you can use is 200 to 300 ft/second. Going too small will increase velocity but restrict flow and cause excessive pressure drops. Going too large will, to a very minute extent, increase response time from the turbo. But given the choice I always go too large vs. (potentially) too small.

Calculating charge air tubing diameter from flow velocity:

http://turbobygarrett.com/turbobygarrett/charge_air_cooling
 
...at the end of the day, a 1" difference in IC piping size won't make a lick of difference on a 13 to 15-second Volvo's quarter mile time, nor on it's power output.

Do what's easiest, or what you prefer.
 
Pressure is highest at the compressor outlet. Using too small of piping is going to cause a loss in flow. Using too large causes a loss in velocity but that doesn't really matter because velocity is measured at the outlet, the throttle body which won't change in size.

I'm doing 2.5" or 3" on my setup.
 
Don't forget all the measurements you guys are citing for tubing/piping are OD - 2" OD is only 1.75" ID at best. 3" OD is only 2.75" ID. The restrictive fast spool twinky turbos used by Volvo don't demonstrate any noticeable difference in response, in my experience with using 13c, 15g, 16T, 19T or even the Hybrid 20g. I would recommend using the largest piping you can fit - which is pretty easy on an RWD setup. I must have reworked my piping 3-4 times before settling with 3" hot/cold & 4" intake.
 
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