JTso

iTrader: (2)

I went to the dyno today to see if the cat provides any gain before I bolt up the custom A-pipe. This way I know what works and what not. Today's temp is about 10 degrees F hotter than the last dyno. So I kind of expect some variations. Here we go...

No peak gains but that also means the big bore TB still providing the same peak hp and repeatable. The cat actually causes come loss from low to mid range prior to vtec. I wonder if this is the result of component mismatch as I'm still using the stock catback exhaust. I believe other members felt some gains with their aftermarket catback system. So, based on this result, the cat is off until I can test it again with a catback system. I probably wont' install the custom A-pipe until then.

Dan Martin

Hmmm... not the results I was looking for but thanks for getting the dyno done!

JTso

iTrader: (2)

It's possible that some tunning is required to take advantage of it. But that means waiting for the K-Pro...

madmanmax3000

thats brings up a good point...are all of the parts for the '06 engine going to fit on ours? Cause if not, does that mean no K-Pro ever?

Asahi

What do you mean by custom A-pipe? It this somehow to avoid doing an actual header upgrade? I'm still learning what works and why.

I am not surprised the cat dropped low end tq like that. But am not sure what to expect fom the exhaust.

dzuy

i wonder if i would gain any hp with the high flow cat.

dzuy's setup:
comptech i/h/e
hondata reflash
hondata intake manifold gasket

JTso

iTrader: (2)

The custom A-pipe is another project that I'm working on to go with the high flow cat with matching pipe ID. The idea is to bolt up to an aftermarket catback with the same inlet ID.

https://acurazine.com/forums/showthread.php?t=24293

artmcd88

Gains usually arent that great if you just replace a single part of your system. The most effective way is obviouly to increase the flow from the exhaust ports back. Otherwise its not going to provide much performace at all. If you think about it like breathing through a straw, if you increase your lung size your still not going to be able to breath any better untill you increase the straw diameter.

Tsx536

Looks like I won't be doing this mod. I definitely don't wanna lose low/mid end torque.

I bet having a aftermarket exhuast would help. I'll be interested to see what happens when you get a new exhuast.

Thanks for doing the dyno Jtso. Saves me some time/money

rmpage

Man, that's strange, I wonder how big a bottleneck the stock catback is.

Thanks for the graph.

kurt_bradley

It's bad. If you go with a one-muffler design, you'll see some serious gains. For the most part, aftermarket cat-back systems haven't yielded too wild of gains. They've all been in the range of 8-10 whp, but, of course, most of the buyers of these systems are going after tone more so than gains.

Chris_F

8-10hp? i thought it was more like 1-3hp if any at all (assuming your talking a dual outlet design)

Single outlet would be the way to go.

rmpage

I should try doing two pulls with the catback disconnected to get the most accurate comparison between the two cats.

If I knew how to get around the fact that it would look extremely silly, I'd have a custom single exhaust on my car by now. Magnaflow resonator and straight-through muffler would be the sexy sweetness.

Dan Martin

I think you could get around the silly look by using the rear bumper from the Euro Accord. I don't remember which model has it, but one comes stock with a single exhaust.

vidgamer

On Comptech's site, their dyno hardly shows any gain. I think a lot of people would get very excited to see 10 whp! Which system does that?

http://www.comptechusa.com/dyno.htm#tsx

Maybe the stock system isn't that bad. Of course, the only way to be sure is to dyno with everything else upgraded, and change the catback last, and dyno again.... Recently, someone suggested that you need to upgrade the whole system to see results? Well, it'll be interesting to see any dynos that test these theories.... :-)

vidgamer

Or, keep the bumper stock and just have a "dummy" muffler and tip on one side.

So, what's the problem with two mufflers? Not enough backpressure or something?

Dan Martin

Not backpressure, low exhaust velocity.

rmpage

The fact is that the exhaust system is just that - a system comprised of several different parts and reliant upon the performance of each one individually to perform well as an aggregate. Thus the overall ability of the exhaust tract to get rid of the exhaust volume is only going to be as good as its most restrictive part. If the biggest bottleneck is in the header, changing the cat and catback may help a tiny bit but won't really be worth it unless you do the header too. If there is a bottleneck upstream, anything replaced downstream will be a waste of time. That's why most people go intake, header, cat, catback when they upgrade for performance increases - following the natural flow of the air through the car makes the most sense. Generally speaking, the cat is the most restrictive part of the tract, so a catback will do no good from a performance standpoint until you eliminate the cat bottleneck.

I wonder how much that Y pipe screws up the rhythm of the exhaust pressure waves. It's a pretty acute 90 degree bend outboard to either side.

DaveWhyman

With a single exhaust you can smooth out the flow where you would have had that Y-pipe. You could probably also save 40 lbs. IMO dual pipes on a car with only one exhaust bank is purely an esthetic issue. You don't see many dual exhaust 4 cylinder race cars...

vidgamer

What do y'all think of the "No Loss Exhaust" article here: http://www.ntpog.org/articles/index.shtml

If I read that correctly, once past the resonator, the exhaust simply needs to flow sufficiently.

You might replace the header and cat and still find that replacing the catback does nothing for you because it just isn't that restrictive. Maybe! Is there a dyno showing an exhast change after someone has completed header & cat mods?

For an amount of air flowing out of the engine, you're going to reach a case of diminishing returns at some point.

My guess is that the header is restrictive, but the other parts, less so. I will be curious to see the dynos that prove otherwise!

rmpage

Absolutely. I meant that changing the catback before you change out a restrictive header would be by and large a waste of time until the upstream bottlenecks are widened.

dzuy

rumor has it that someone witha 6MT who has intake, exhuast, header, hondata, hondata intake manifold gasket is now acquiring a high flow cat.

i wonder how much that would put down.

:troutslap

Tsx536

Thatz phat Dzuy.

Chris_F

did anyone end up finding out about the exhaust outlet cover in the other thread with the red accord from europe?

That'd be an ideal solution.

dzuy

thx.

i might have my first autox experience aug 27 in jacksonville florida - i have to look it up