I was talking with my buddy last night who knows a lot about 2 stroke setups and expansion chambers. They are basically tuned in size and location for that motor setup with header, intake, carb and so on. Two stroke motors benefit greatly from expansion chamber tuning due to the motor relying on the downward stroke and expansion chamber to pull in fresh air and expell the gases. Tunning the exhaust expansion chamber optimizes the rate at which the air is pulled through the motor. The expansion chambers basically act as a suction device(scavenge) if designed properly. You don't typically start with the exhaust first and adjust the motor setup backwards. You'd do the exhaust near the end. Basically what Gernby has done and I applaud him for that. Take an OEM setup and make the most of it just like factory tuned race bikes. Now I'm having a hard time deciding if I'd like one and stay remotely OEM versus nice header + typical 70mm cat + 70mm or larger exhaust. I might be moving to cali which possibly means I'd have to modify the Gern-pipe with a cat for smog checks.

and while I think this gern-pipe is definitely worth the money for those with OEM'ish setups, I'm really interested how this reacts with head work and cams. I'd hope to see some mid range gains over typical test pipe and typical 70+mm exhaust. Technically, it should work well. Adding a header that does even more scavenging, may or may not help with an mild NA setup. supercharged would be another story.

 

I have been talking to a vendor about that, but no firm plans have been made. There would need to be lots of stars aligned to make it happen. The hard part would be finding a manufacturer that could build it at a reasonable price without requiring large production quantities.

 

@jh4db536 - Thanks for the additional feedback! I'm glad you are enjoying the pipe.

@berny2435 - You are correct that the physics behind the Gern-Pipe are the same as those for 2 cycle expansion chambers. However, the issue you mentioned about tuning from the engine down or from the exhaust back is not really relevant for this application. It's nothing like a single sylinder 2 cycle in that regard. Most of the gains from my mid-pipe are created by eliminating the plugging pulses that kill midrange torque.

 

Since the stock mufflers use unequal length pipes, left to right, would it not be better to have a custom y split made with equal length and possibly larger pipes to make for a nicer sounding exhaust?

Or does it not matter?

 

The stock exhaust sounds fine with unequal length pipes, since the OEM mufflers completely eliminate drone. The owner that has the OEM mufflers and Gern-Pipe, pmptx, really seems to like the way it sounds.

 

Agreed, drone almost non existant. A hint around 3500, but almost transient. I think the overall sound is a huge improvement, and the performance improvement is exceptional. The mid range improvement takes the car from "a civic under 6K" and makes it a more driveable care throughout the range and still keep the high end VTEC characteristics. The other benefit is that VTEC is more smoothly applied and linear so you miss the "kick" at 6K and instead get the performance benefit incrementally along the rev range. Basically more "usable" TQ from the tuning and pipe, and the ability to optimize VTEC engagement makes more useful power delivery.

 

I started tinkering around with different intake designs over the past couple weeks, and have tested 5 prototypes. My goal is to find an intake that really compliments the torque curve from my mid-pipe. I don't have much interest in developing a new intake product, but figured if I build one that worked well, I would just look at the other intakes currently on the market to see which one was most similar.

Well, I think I've found what I was looking for, but there are definitely NOT any intakes like it on the market. I'm not going to share any pictures until I decide what I'm going to do with it, but here are the dyno plots from back-to-back tests. Green is my intake, and gray is my PWJDM.

Four pulls with each intake.

Averages of the individual pulls from each

 

Greg, You ought to see if Honda needs an engineer for a new S build.
Maybe you can help with the next gen S3000 and get it tweaked out of the box, or at least have a pre set package of settings for it to be maximized.

 

How long is the tube from the TB to the opening.

Sent from my Galaxy Nexus using Tapatalk 2

 

If you've never lived in Cali before, I'll give you a heads up on the current state of smog. You can only replace the cat with a cat listed in the CARB database for your specific vehicle; right down to the manufacture and part number.

Yes, you can, and some have, make the car smog-legal, get it tested and go back to your everyday setup, but then you'll need to be careful of these:



Our lovely road-side smog checks.

Welcome to Cali!