Doc_Z

Hey guys,

Hoping you can give me some advice please. I'm running ART test pipes and a custom exhaust. The exhaust was too loud and then after changes it is now too quiet. I'll explain the setup and hopefully someone can advise on how to improve the sound. I can make some sound clips if that will help.

Setup 1)

Ok so like I said, art test pipes. I then had a custom cat back manufactured, based loosely on the motordyne dual system. So 2.5" y-pipe, into a 3" resonator, followed by a flat oval silencer with 3" entry and dual 2.5" exits. From there it splits into 2x2.5" pipes ending in 2x3" mufflers that are about 5" I diameter with dual 115mm tips.

This setup sounded very nice, but very loud. ZERO rasp, but a heavy boom between 2.5k and 3.5k rpm. Interestingly the exhaust sounded quieter as the rpm increases. At wot at 7k it was very mellow.

Made good power too. Around 265whp untuned.


I then decided to change the system

Setup 2)

Same setup as before, but changed the rear silencers to 2x2.5" larger mufflers. Around 8" diameter with 4" tips.

Car sounds good but a very close to stock. Outside the car it sounds pretty nice but inside you can almost not tell that the exhaust isn't stock. Sounds a bit like a 330i bmw. I know a lot of people would like that, but I would like to enjoy my exhaust too, not just the people outside the car.

Also, I feel that power is a bit down. Will do a dyno run tomorrow to confirm, however that will also be untuned, so I think the results could be misleading.


Now, would removing the resonator chamber behind the y-pipe introduce any unwanted effects like rasp? Will it improve power?

Or should I change the 2 rear silencers to maybe 3" again, but with a slightly smaller diameter than the current 8" ones.

Thanks

Deteria

iTrader: (2)

You should order the Meisterschaft exhaust. It will solve your problem.

stuartc323

if you have the cash for that, if not get the motordyne.

Bmurray350z

iTrader: (34)

HRs make around 260-265whp bonestock. Just FYI.

The_Assassin

HRs make 265 stock so with custom exhaust you should be making more Even untuned. So I say your custom exhaust is crap just ditch it for a motordyne true dual.

Z-Crazy

you need to find a resonator and muffler that suits your exhaust.

it is not just the mere size difference of mufflers but different mufflers are made to block certain sounds frequencies.

your 1st set of mufflers seem to block frequencies at higher end but not so much at the lower end. it needs to work the other way round, Was it quiet while idling?

Your 2nd set of mufflers obviously seems to block most of the sound since they seem huge, quieter car may give a feeling that the power is less. Power should not drop much by just changing the mufflers.

Either keep trying different mufflers and resonators or just buy an aftermarket exhaust and then tailor it to your needs.

I say this because you either need lot of experience to do this or you need a lot of equipment to test various sound frequencies.

Doc_Z

Thanks for the input. The reason I didn't buy a motordyne exhaust is that it would cost way too much to ship it to my country. So buying an aftermarket one is not an option.

As for the power, different dynes read differently. On this dyno most 370z's do about 255whp which is why I was happy with the untuned figures for the hr.

On the motordyne xyz pipe, what effect does removing that first resonator have on the sound? I think maybe 8" was a bit of an overestimation of the size of the rear mufflers. See pics below.

Doc_Z

Went back to the dyno shop. Power is pretty much the same. Have lost a few nm torque below 5krpm and gained a fraction up top. But could just be weather. 178.4kw translates to about 240whp and corrected for the altitude we are at it equates to 279whp at sea level. Torque fell a bit from 250lb/ft to 245lb/ft.

The dyno graph shows the system with the 3" rear silencers on the dotted line, and the larger silencers with 2.5" entry and exits on the solid lines.




Here are two dyno videos comparing the 2 exhaust setups. Notice how the sound gets a bit quiter at higher rpm.

First one is with the 3" rear silencers. 4.5" tips. I'd say the silencers were about 4.5" diameter.


Next video is with the larger but 2.5" silencers. I measured these. Diameter is 6.2" and length is 13.8".

stogey420time

iTrader: (1)

I can't help but to notice, the tiles in your garage floor is money

Doc_Z

Haha. Thanks. Makes operating a trolly bed under the car interesting though....