Thread: Electric Cutout Discussion

I've done some searching through the site and have found some information on the topic. Most of it however, doesn't fully explain everything about the performance aspects of an electric cutout on SR20s and how they relate to particular setups. My goal is to pool all of the knowledge some of you guys have on the topic through experience into this thread.

I'm currently running a stock RR SR20 in my B15 Sentra and would like to keep the stock exhaust system from the primary catalytic converter back. My plan is to get an "eBay" 2.5" style 4-2-1 header and have a 2.5" electric cutout installed on the downpipe before the catalytic converter. Future plans will probably involve a small 50ish wet shot of nitrous which I'm sure the cutout will go well with due to the increased cylinder pressure.

My question is how will an electric cutout effect the performance and powerband with the setup stated above in N/A platforms? I seem to be getting conflicted reviews and testimonies of people who have gained power and some who have lost power and especially torque throughout the powerband. I assume the results are similar to running open header, the difference being you have some length of exhaust pipe from the header downpipe before reaching the cutout.

Ideas, insights, recommendations, tech articles, testimonies, personal experience welcome.

subscribed...i will be running a cutout on my rwd det which i believe will be beneficial on a turbo motor...but on your setup i think you will lose power due to backpressure but dont take my advice on it as i never ran a cutout im sure someone with experience can chime in i'd also like to know more info on this

Hopefully, we'll get a few more replies with the light of a new day. Cheers.

I have one on my car, unless you are boost or have a real nice header+compression not really worth it. BTW you either have to plce where the cat is at because it will hang much lower. I have one on my car right now with a VVL, just makes a crapload of noise. BTW knock sensor will pick up knock, but it is just the vibration from the exhaust, I disengaged knock feedback.

I bought a 2.5" one hoping to use it on my turbo car, but decided it wasn't worth the hassle. I then just started messing with mufflers and got a decently good flowing STI muffler.

Cut outs are good for a track day, or if you have time to open it every time you want to take it out on the street. If I did a cut out again I would wire it to my TPS, so that it opens automatically based on throttle, manually opening it FTL.

I plan to place it just before the secondary catalytic converter. I'm guessing the more piping I have, the more back pressure I'll get. Then again, a standard header funnels to a collector. I would think that anything after this collector, in theory, is irrelevant for performance and just relief for emissions and noise.

I understand the factory knock sensor is a bit sensitive, but I don't see how running a cutout would cause the sensor to detect false noise. I haven't heard that claim before. Yes, it will be very loud and you will get vibrations in the cabin from having the exit below your seat, but I don't see how that translates to more vibrations at the engine. Where is your cutout located?

Thanks again for the input.

I plan to get an electric cutout (QTP), which opens and closes via a switch in the cabin. My goal is the keep the factory exhaust system for daily driving and then have the cutout open when I want to have some fun or run at the track. Best of both worlds I guess. I'm just trying to review testimonies from people who have tried the setup and had success.

Thanks for the reply.

It is not irrelevant. Stick a banana in your tail pipe and tell me it is irrelevant.

Or you know, put a cut-out there and tell me it is irrelevant.

I don't quite understand your analogy. I understand back pressure is important to maintain a certain amount of torque and on most vehicles. I'm just wondering if a 2.5" cutout installed downstream on a 2.5" downpipe from the header will yield favorable results.

Exhaust has nothing to do with back pressure and everything to do with velocity. On a turbo engine everything after the turbo is some what of a moot point. But on NA the exhaust size and length has everything to do with cyl scavenging and proper flow rates. A cut out on an NA engine will do nothing but hurt performance. Case closed.