So I have race school tomorrow, it has a strict 93db sound limit and with the WR Race header, T1R B-pipe and T1R 50S exhuast I was getting pretty close to the limit even with the silencer in.

So I bolted up the stock muffler to see if it could curb the sound a bit... the results were interesting.

I have to say it was crazy quiet compared to what I was used to and also I noticed the engine response picked up right away. It has a solid blast of power of the line, but as soon as you shift and goose it again in 2nd gear it is lag city. But depending on how you accelerate it feels like you can coax more power out of it than with a free-flowing muffler.

Basically I think the Fit benefits from some back pressure, but not too much. This kind of verifies what we saw on the dyno last year when we noticed the Fit made MORE power with the silencer in rather than out.

I am thinking about trying to tune it with the stock exhuast for this summer, it sure drops my car off the suspect list when it comes to police profiling and with sound limits at all the courses I don't really want to be bolting and re-bolting the exhaust all the time.

Any thoughts?

 

FI>NA all the way.

 

tagged for interest

and I, for one, am glad that there's someone trying to push the L15a to it's potential without automatically subscribing to the school of "zomg nub! b00st or Sw@P is the only way to be fast"

Driving school is possibly the best "mod" you could do to improve your lap times

 

From what I've read it appears as though some amount of "back pressure" can be good for midrange response, but it will come at the cost of top end power. Perhaps more accurately; exhaust gas speed is very important, and large pipes can cause low exhaust gas speed at lower RPMs. Exhaust flow ends up being a compromise, surprise surprise.

I'm not a professional at this stuff but I suspect that matching the exhaust gas speed to the engine's torque/horsepower peaks is the way to produce optimum results. IOW if you're still running a stock motor, with no major changes such as cam/bore/stroke/compression ratio, your hp peak and torque peak aren't going to move much; so tune the exhaust to hit those points.

Some links I found useful:

Advanced Exhaust Tech I - Team Integra

http://www.hondacivicforum.com/forum...ead.php?t=3064

The myth of exhaust backpressure - My Pro Street

 

FI is a good option; but I am not totally sold on any of the tuning options yet.

Besides in Autocross it throws your car into a class that is way too competitive.

I did a full 8 hours of driving school today, was freaking awesome. I learned a lot of good techniques to get me through the course faster without burning more tread. I think the Fit surprised the hell out of everybody.

A couple of quotes from the instructors;

"I am absolutely shocked at how fast this car is through the course"

"The suspension on this car is totally dialed in"

"What? These are street tires!!"

"What? You don't have a suspension kit, only springs!!!"

lol, I was posting AMAZING times for this car. This year is going to be awesome!!


I would tend to agree with this 100% actually, I can feel a much better initial response but it does feel like it suffers once it is up and going.

 

I wish there was a racing school in chicago. I just can't find one

 

Get your local autoX club to bring these guys in!
SoloPro Driving School LLC -

As long as you have a good lot to use & 18 people interested it should be no problem. It was a bit pricey, but it is a really good program and worth every penny IMO.

I finished my second day yesterday... the Fit is freaking amazing!!!

 

A cable controlled flapper valve would enable exhaust tuning and wit a 24" glass pack muffler you'd still by quiet with it open.... The low end torque gains from a more restricted exhaust flow would make a Fit with automatic transmission and paddle shifting kick ass on a very tight course..... I saw my first parking lot time trial back when Austin-Healey Bug Eyed Sprites ruled, and what is now called auto cross was a gymkhana. That was fifty years ago.

 

God I can't wait to go to one of the AutoX school days that have here sometimes.

The other day I was thinking about stock exhaust tuning as well, Looking forward to anything you find out.

 

Isn't power based on the proper "exhaust velocity" and not "back pressure"?

Back pressure by itself is turbulence where the exhaust velocity is a balance of flow.

Just thought I'd throw that out there.

 

Velocity itself is speed and key to intake and exhaust function. It is in some minds confused with volume like in the days of huge valves intakes and exhaust headers. In the 1930s there were racing cars that in addition to super chargers used exhaust scavenging pumps to pull in more fuel during cam overlap, evacuate all of the burned gases and prevent reversion.... During the mid 1980s KTM motorcycles came out with a wing shaped device that was installed in the reed valve cage in front of the intake port to increase velocity and lower end torque to broaden the power band with out hurting power at the top end.... Cherry Bomb is presently marketing a "wing plate" muffler that I would assume does the same thing on the exhaust end.... Just some things to think about.

 

I just installed a T1R header and b-pipe. These are in combination with the stock cat and axle-back.

The car now has more oomph in the midrange. I can't comment about differences at the top end because I pretty much never go there. Sound levels haven't changed much at all; a slightly throatier sound noticeable inside the car, nothing really different sounding outside the car.

Like Sugarphreak I'd like to back up the butt dyno with real dyno numbers, but so far I'm very happy. I wanted more grunt without attracting the popo or polluting the air, and that's what I got.

 

You are running pretty close to what I had last summer. I was also running the 50S cat back with the T1R header & B-pipe. The sound levels were very reasonable actually, only after I deleted the cat did I notice a huge surge in sound.

 

This is some very interesting and surprising information. Cool.

 

I am almost thinking to take the time and dyno test with the 50S against the stock muffler to see if the extra back pressure makes any kind of real difference... it will be a few extra bucks though

 

Cat delete is not something I want to do. I kept the cat on my STi so I'm darned well going to keep it on the Fit! But I do wish that somebody would make a high flow cat for the little guy.

Noise is something I'm happy to do without on the Fit, especially inasmuch as it attracts John Law. I have a very long, very late-at-night commute, and I swear there are at least as many police on duty at 2am as there are at 2pm -- but 1/20 the number of cars on the road. So the cops at night are all bored out of their gourds, looking for something -- anything -- to do. It's not enough to do the speed limit, not at 2am in Pennsylvania.

Back on topic. I took another spin today, down the hill to drop off some drain oil and back up the hill to home. Really fun twisty roads pretty much the whole way. Had my usual amount of fun in the Fit, and definitely noticed the additional torque. It's not a lot, but it's enough to allow me to stay in a higher gear while climbing without losing speed, whereas before I would have had to downshift to hold my speed. This is going to be interesting.

 

After the Japanese took over the motorcycle market there were a lot of old neglected Triumphs in garages all over the Dallas area that cold be had for a song. I was able to buy a few of them with a lot of after market parts and many different exhaust configurations. The smallest 1 3/8" pipes with a cross over pipe into reverse cone megaphones were by far the best. They produced power through the whole power band, but were very loud. I think about it now and can't believe I never got a ticket on that bike, but it was beautiful music to me. The stock mufflers weren't bad either, but the larger the pipe the worse usable you had the worse the power loss somewhere in the power band..... 1 3/4 pipes were crap at any RPM...... I am not sure if I will ever change out my stock exhaust manifold unless I upgrade the boost on my car to 10 PSI. It is possible that the stock muffler actually increases the flow velocity. Thanks for keeping us informed.

 

So I did a bit more playing around today with combination

I popped back in the 50S exhuast, the upper end returned but the lower end kind of felt hampered as if I lost some response... pretty much the same as before.

So this time I yanked the silencer out (mostly just to see how crazy noisy it was, this is the first time I pulled it out ever with the cat delete)

Another surprise.... massive immediate gains in the low end A stronger pull throughout the bandwidth, but oddly enough similar sound levels as before!? I can't believe how fast it takes off from a dead stop all of a sudden.... so weird.

When I had the response header & cat in I did notice the silencer made it much more toned down and civil, it was almost a must because it didn't really impact performance and kept the sound down.

But opening up the entire system wide open with a un-interrupted 50mm exhuast this time didn't really make it louder... although gains are very noticeable.

Anyway, just thought I would share.

 

With it running so strongly as it is, I hope that it meets the 93 decibel limit. Thanks for sharing your findings.

 

lol, I am borrowing a sound meter next week to check

I think I might actually be ok