Forced Induction Superchargers | Turbochargers | Intercoolers

Cold Side Pipe Size Step

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Old Aug 18, 2010 | 06:20 PM
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Default Cold Side Pipe Size Step

Would I be looking at any kind of pressure drop if I had to step from a 3.0" pipe to a 3.5" pipe between the intercooler and throttle body? Reason I ask is because the entire system I'm finishing up is 3" but the TB elbow inlet is 3.5".

TIA.
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Old Aug 18, 2010 | 09:32 PM
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on my builds i go from 3-4" with no issues in drop of pressure that is noticable. i did noticed a drop in iat
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Old Aug 18, 2010 | 09:55 PM
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I am sure with the right equipment you can record a pressure drop. It would only be logical. But what we need to keep in mind is pressure is only a messurment of restriction. The same amount of air will be delivered, but at less velocity. If you port your heads and everything else was equal, you should see it takes less pressure to make the same HP. If I saw a pressure drop at that point I would be looking into up sizing the piping in order to make my system more efficient. Otherwise it is a mute point. Again, I doubt there will be enough of a drop to matter. Nor would I expect it to be much more then a few inchs of water colum drop.
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Old Aug 18, 2010 | 10:20 PM
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I guess my worry is causing a velocity stall, but I am also looking at it as a move that's only 1/2 inch in diameter and thus not that much overall volumetric area. Going to all 3.5" pipe for one would SUCK because I just bought all the 3" pipes, but for two, my intercooler is a 3" in and out, so it would kind of be pointless because it would be cutting it down at the intercooler.

That said, it's enough not to worry about, and I'm just going to run the 3" up to the elbow and use a reducer. I've got it mocked up right now and it (the step at the elbow) looks ridiculous, so I'll probably get a 3.5 inch setup for the top side at least the top side of things to make it look more uniform.

Thanks for the help guys.
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Old Aug 18, 2010 | 11:23 PM
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Pretty much all the builds Ive seen have people using 3" pipe and using a bending reducer at the TB, me included. I have no issues
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Old Aug 20, 2010 | 12:13 AM
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Originally Posted by XtremeDime
Pretty much all the builds Ive seen have people using 3" pipe and using a bending reducer at the TB, me included. I have no issues
When you say bending reducer do you mean a 90 degree with one end 3.5" and the other 3"? I am sure it was the peice I bought but I use to have one of these. I had a bad problem of the darn thing callapsing if i nailed the throttle. It wold choke the engine back off. I am stating this just so the OP knows if he goes this route be sure to get a nice heavy one that does not bend very easy so he will not have the same issue I had.
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Old Aug 20, 2010 | 12:58 AM
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Ya thats a bending reducer. Alot of use get decent ones from a non-vendor, I havent had any issues.
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Old Aug 20, 2010 | 01:00 PM
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Originally Posted by XtremeDime
Pretty much all the builds Ive seen have people using 3" pipe and using a bending reducer at the TB, me included. I have no issues
Same here
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