Supra Forums banner

1 - 5 of 5 Posts

·
Banned
Joined
·
4,144 Posts
Discussion Starter #1
Hey guys,

Now maybe this has a reasoning to it, but I'm just not seeing it. Here's the trend....

Install a single turbo with a 3 inch ID discharge, and route the piping to a Greddy 4 Row. Then, the piping exiting the interecooler, going to the TB is now 4 inch ID. I'm confused as to how this is at all benificial since the cooler, denser air, now has to fill a much larger volume in the 4 piping. Is it because it has to mate up to a 4 inch TB? I've seen turbos as small as an SP67 with this massive pipe leading into the TB.

Personally I run a 3 inch ID piping from turbo to TB, and I see not as much lag as I would have expected. 3rd gear full boost is around 5500 on a GT47 88mm, and I have to wonder if the piping diamete plays a lot into it.

Just curious, it all works either way, but I am wondering the logic behind it.

Eric
 

·
Banned
Joined
·
4,144 Posts
Discussion Starter #3
Well, I read the thread you refered me too, and it seems that no one has a real answer, just that it's sort of the thing to do now. I'm still in the dark on how this is benificial if the turbo discharge, and intercooler ends are 3 inch. Is it "Bling"?

Eric
 

·
Member Thingy
Joined
·
1,120 Posts
I think the problem is that most people assume 3" intercooler endtank outlets to be the most beneficial. I would argue they are manufactured that way for othe reasons, such as uniformity of required materials, and versatility to the end user. I'd be led to believe that the intercooler endtank intake should be Identical in size to the compressor outlet, and depending on piping length, generally the intercooler endtank exit should be identical to the throttle body ID.

There is room for variation based on setup, such as intercooler core type and dimensions, and particularly endtank and intake manifold design, but as a general rule I'd say the below is the best universal fit.

Compressor outlet ID = Intercooler endtank intake ID

Throttle body internal area at butterfly minus frontal area of butterfly when open = area of intercooler endtank exit, whatever diameter that works out to.
 

·
Getrag Gearhead
Joined
·
1,872 Posts
Eric, You are right on target about the limitation is the smallest opening. I myself would rather run a smaller piping from the intercooler to the throttle body than the exit of the compressor. The intercooler is making the charge cooler and denser and packing it tighter anyways. The 4" throttle bodies already do reduce the progressive feel of the throttle (driver's prospective) so it isn't like the throttle body is much different from individual throttle bodies or rotary-barrel throttle control.

The see only one advantage to increase the piping from the intercooler to intake to 4" and this would include enlarging the exit outlet of the intercooler as well. If the air going to the intercooler is expanded to help increase its cooling efficiency then having it collapse back to the same outlet will not be much help. Now if the outlet was increased from here the restriction is on the piping from the compressor to the intercooler. If anything the larger piping should help motivate the air on the smaller inlet side to move across at a faster rate. However, doing so is also making the overall volume of the piping larger and is affecting the spool. Although a dyno may say different than the driver. The dyno isn't seeing the area under the graph, only the top of it. So the drivability of the vehicle may go a different direction than desired or may require adjustment inorder to work accordingly.

Donno if this helps but I figured its worth mentioning.

Joe
 
1 - 5 of 5 Posts
Top