I have the Thermal Axel back connecting to my factory b pipe which I believe is 2.5 inches. The thermal is 2.25 and I am getting the 2.25 comptech 4-2-1 header put in as well. Will I loss power with the inconsistency of the sizes from the header to the exhaust? The great header test with the comptech 4-2-1 was also placed on an exhaust with 2.5 inch piping and still performed excellent. Will I gain similiar numbers or am I better off getting a 2.25 in B pipe made? Thanks!

 

First off the stock ITR exhaust is 2.25" OD but has its fair share of bottlenecks, the worse being a 1.75" ID/1.88" OD one at the cat flange and then opens to 2.25" OD. The Thermal unit is 2.25" OD. The Comp Tech header is a USDM header so the collector OD is 2.00" OD. The comptech header used in the header test was hooked to a 2.50" OD exhaust via a 2.25" x 2.50" stepped test pipe so don't expect the same gains with a 2.25" system.


[Modified by SMSP, 5:08 PM 6/26/2002]

 

huh?

 

what if I got a custom 2.5 inche piping....would my gains be a lot higher and close to the header test then? Thanks

 

That's a hard one to answer. It depends on the type of resonator/muffler you use, how the joints are made in the tubing, cat vs. test pipe, accuracy of the test, etc. I thik the Comp Tech did well due to the stepped test pipe and the exhaust. I think the results might be different if it was dumping into a 2-1/4" cat and then 2-1/2" tubing.

SMSP - Who still thinks if your modding a B18VTEC engine it should include a header with a 2-1/2" collector

 

Well, if I stayed with my factory b pipe and cat, installed the comptech 4-2-1 header, and also have the thermal axel back exhaust and AEM CAI, would I be making at least 10-12 whp?

 

Great...now we've got Dave speaking in the 3rd person...
Austin - who does it at times as it's easier to say some things

 

I honestly don't know but I think a new 2-1/4" cat should be part of the equation. They out flow the stock cat by about 40%.