Helix Down pipe install
 

Total time from prep to install and clean up took about 1 ½ hours. Difficulty: easier than changing a header on a Honda. Only difficult part is knowing how to put the DP back on if you work alone with a house jack.

1. You will need an extension (about a foot) to reach the spring loaded bolts at the donut gasket point. You do not need to take the plastic under tray off.
2. You need to take the two tie bars off.
3. You will need a factory jack to hold up the cat and mid pipe since they don’t have any hangers once the DP is off otherwise it will damage the 2nd O2 sensor wires. (Pic)
4. Loosen all the bolts i.e. spring bolts, hanger bolts and the bolts to the cat to the point where you can unscrew them by hand. Then unscrew the hangers. While holding the DP so it won’t drop, unscrew the rest of the bolts.
5. Once the DP is off make sure the donut gasket is still on the O2 housing.

You can use the 3in gasket to the cat or the stock gasket if you have a stock cat. I prefer the stock gasket since the stock cat’s opening is small. The 3in gasket will only seal towards the edge of the cat while stock gasket will seal everything. I would save the 3in gasket for future use with 3in cat.

Install is just doing the opposite but must be careful how the bolts go on. Screw all the bolts with hand but only to sit and align the DP (don’t tighten all the way). Once all the bolts go in and the DP has a clean install, tighten the bolts; but when tightening the spring loaded bolts, you will need to tighten them together that is tighten one side a bit then the other side and so on. This is if your DP uses the stock donut gasket since donut gaskets are round and need to sit properly.

Helix DP review
 

The Helix DP is very nice and the quality is very high.
You will not notice much power loss at low end but 2k and above feels alot better and at high rpm Evo pulls harder than before.

This DP or any other 3in DP will not clear the oil pan by much. Helix fits very tight since it clears the factory tie bars. (Pic)
In fact, the Helix I got was rattling against the upper chasis. It sounds just like a grinding noise due to high vibration of the engine. You would have thought the thing was touching the rear drive shaft or the clutch was going bad. This problem was easily fixed by slight mod on the hanger rods (I have experience in making parts fit when they don't from all the Honda days :lol: ).

If you run tracks, 70mm DP is the way to go such as the Works or HKS. But for those daily drivers who only need that extra power once in awhile 3in is great.

Pros:
Helix will clear the tie bars, very nice quailty, and great price.
Cons:
Helix fits very tight. If the tolerance is off just a bit, it will touch. It's not for track use as it sits close to oil pan.

I haven't seen other DP upclose so can't compare it.
Overall, I am pleased.