Rep Power: 296

I just recently took off my HKS axle back exhaust for the winter and decided to measure its piping. To my surprise it was a little less then 2" in diameter.

Im planning to get a custom midpipe this winter and was wondering what size i should get. ive searched and common conclusion would be a 2 1/4" pipe. but if the HKS is less then that, will it disrupt exhaust flow because its a smaller pipe? Should leave it stock?, get 2 inch piping or just get 2 1/4"?

I plan on getting nitrous in the future if that has any input on what you guys think. Thanks

 
Rep Power: 0

The HKS axle back have that diameter because when you use it you are only taking out one of the many restrictions on the stock exhaust system (just the stock muffler). You still having the little stock pipe, muffler-style resonator (big restriction) and stock CAT.
I would not remove the CAT, but if you are going to make a custom made job, using 2.25" piping with a hi-flo resonator and a good muffler like Greddy or Magnaflow will sound nice, deep and give you some horsepower and torque on the top-end. Don't expect many gains and be prepared for a little power loss from low end to 3500 RPM.
But I really enjoy and feel the difference from 4500-6750 RPM.

Good luck and I hope this helps.

 
Rep Power: 296

So your saying just ditch the HKS and get a muffler with 2.25 piping? Why cant i just get 2.25 piping and have it just funnel into the HKS exhaust. Its only about 1/4 inch less then diameter. I highly doubt i would lose hp and possibly retain torque because that small restriction could add some backpressure. My resonator is already chopped too BTW and im probably going to get ebay headers and megan racing downpipe.

 
Rep Power: 0

Well, bottle necks are not good in the exhaus system, but give it a try. If it's a custom setup you always have the choice of changing it if you think that it's not enough. And I'm not saying you should ditch your HKS, it was just a suggestion cause bottle necks are not good in there, and I mentioned Greedy and Magnaflow cause I know they perform well and really sound good and deep in a full exhaust system in our cars, but I've never heard an HKS in a 7thGen so I don't know how it sounds.

About your header... I would not buy an "eBay" header, nor a DC Header. OBX, HKS, Kamikaze Headers or those "Tuned by Matrix" are good choices for our cars. NOT ALL but many cheap headers on eBay just don't match well the head ports.

About the Megan Racing downpipe/resonator.... ummm GOOD CHOICE!!

Hope to see pics of your full exhaust soon!!

 
Rep Power: 363

a full 4-1 HP header is also a top choice

 
Rep Power: 296

Yea, I think i will just try the bottleneck. Unless it was a full race car, I dont' really care if it doesnt' perform optimally. Im sure going from 2.25 to a 2 inch pipe won't make too much of a difference. By ebay header i meant probably OBX because from what i heard they are good for the price. Im sure all this won't add much power, but hopefully it will compliment nitrous well. Thanks for all the help.

 
Rep Power: 296

Well plans changed, Im getting nitrous with 2.5 inch piping. Do you think I should just sell the HKS, buy a new muffler and get custom piping. Or just hack off the piping of the HKS and just weld 2.5 to the muffler? I THINK but im not sure that the inlet on the HKS for our cars is like 50 mm and not the standard 60 mm. Any help would be great.