Will this change help, hurt, or neither???

Here's the deal. I had a few import cold air intakes laying around that were just taking up space. My blower inlet "dryer duct" for the S-Trim had gotten crushed a little by misplacing a jack oh so slightly. Anyway I decided to take the nice mandrel bends of the cold air intakes cut and splice them together to replace the dryer ducting. Come to find out the dryer ducting is 3.5" and the CAI's are only 3". I did it anyway and the new tubing turned out really nice. I put a huge K&N filter on the 3" and honestly I can feel no SOTP difference. I wasn' really looking for gains, I just wanted a project.

My question for all of you is: Do you think I should be worried about the 1/2" reduction of the tubing diameter hurting performance? I haven't had a chance to get up to full boost but everything seems to be normal.

Not sure how much that "dryer duct" is corrugated, but if it is then the actual internal diameter may be close to only 3" anyway. I wouldn't bother with anything less than 4" anyway, but that's just my 2 cents.

Thanks for the input. I know it's not effecting it much, but I'm going to put it to the test on the dyno on the 29th just to be sure. As far as 4" it wouldn't help the inlet of the S-Trim is only 3.5 so it's only going to flow so much.

Isnt the blower inlet housing and the 90 deg elbow that feeds it, both 3"? If that's the case, then a short run with mandrel 3" bends should do fine.

3" smooth tubing with mandrel bends will flow better than 3.5" corrugated ducting. the best way to tell if its helping or hurting is to see how much boost it is making now compared to before. i only have a 3.5" induction setup on my t-trim(should be running 4"), but i still picked up 7psi of boost when i built that intake to replace the old corrugated tubing/smaller filter setup that was on there

As far as 4" it wouldn't help the inlet of the S-Trim is only 3.5 so it's only going to flow so much.

That is incorrect. Piping flow numbers are determined by the diameter and length of the piping in question. By using a larger inlet pipe, even if you have to step it down to enter the blower, the less inlet pipe flow loss and the easier it is to get the blower ambient air. When the blower has to work harder to overcome inlet pipe frictional losses, heat goes up and power goes down.

3" smooth tubing with mandrel bends will flow better than 3.5" corrugated ducting. the best way to tell if its helping or hurting is to see how much boost it is making now compared to before. i only have a 3.5" induction setup on my t-trim(should be running 4"), but i still picked up 7psi of boost when i built that intake to replace the old corrugated tubing/smaller filter setup that was on there

WOW! 7psi is a lot of boost to pick up. Just from my short drive after completing the job I could not really tell if I had more or less boost. You would think I would have noticed something if I were going to pick up even half of the boost you picked up. I guess I'll find out for sure once I get it on the dyno. I will run the data log on the Gen VII, that way I will know for sure.

Do you have any photo's or at least a diagram you can PM me?

TIA

That is incorrect. Piping flow numbers are determined by the diameter and length of the piping in question. By using a larger inlet pipe, even if you have to step it down to enter the blower, the less inlet pipe flow loss and the easier it is to get the blower ambient air. When the blower has to work harder to overcome inlet pipe frictional losses, heat goes up and power goes down.

Thanks for explaining this. I guess I thought for the most part that at part throttle I was still going to get plenty of air so the decrease in diameter would not be an issue. Then once I get into boost the blower is going to shove all the air into the engine that it can handle, I didn't even think about the increase in temp due to friction. What is interesting is that my IAT now is actually lower than before, so I guess maybe this tells me that the change was a good one and that the Vortech dryer tube really does suck.

Again thanks for the explaination.

Thanks for explaining this. I guess I thought for the most part that at part throttle I was still going to get plenty of air so the decrease in diameter would not be an issue. Then once I get into boost the blower is going to shove all the air into the engine that it can handle, I didn't even think about the increase in temp due to friction. What is interesting is that my IAT now is actually lower than before, so I guess maybe this tells me that the change was a good one and that the Vortech dryer tube really does suck.

Again thanks for the explaination.

You're welcome, but I still think you've misunderstood. The increase in air temp is a result of the blower working harder (in this case to get air INTO the blower). Any time the blower has to overcome inlet or outlet restrictions, the heat goes up.