[BomberCamaro]

Just curious if anybody has any info on how much the suitcase under the trunk is holding us back aside from weight. I put a lot of highway miles on my car (2,000 a month minimum) so I would like a nice quiet drone free cabin so I can jam out to my music Definitely going catless downpipe, so a slight bit of sound is expected. l plan on shooting this car over 300whp. I know mufflers normally don't restrict a ton of power, but I've also never seen one that I could use to sail across the ocean.

If it is actually very restrictive, I'll just straight pipe it. No huge deal. I refuse to spend the money for an axleback system that is essentially just pipes with some tips and a brand name. I love the sleeper aspect and it would be nice to be more a surprise to my foes

[Bluecyclone]

Do remove the ugly mufflers and do cherry bomb like resonators. I did this to an 83 Caprice with Dynotech headers. It had 5.0 with Edlebrock aluminum intake, Edlebrock 600 cfm 4bbl carb, Accel ingition, and other mods for a Chauffeur car I built in Houston,Tx. It was stolen and never found.

[rickwelch69]

Originally Posted by BomberCamaro

Just curious if anybody has any info on how much the suitcase under the trunk is holding us back aside from weight. I put a lot of highway miles on my car (2,000 a month minimum) so I would like a nice quiet drone free cabin so I can jam out to my music Definitely going catless downpipe, so a slight bit of sound is expected. l plan on shooting this car over 300whp. I know mufflers normally don't restrict a ton of power, but I've also never seen one that I could use to sail across the ocean.

If it is actually very restrictive, I'll just straight pipe it. No huge deal. I refuse to spend the money for an axleback system that is essentially just pipes with some tips and a brand name. I love the sleeper aspect and it would be nice to be more a surprise to my foes

I did a catless downpipe and still have the stock exhaust, most everything I've seen online about restriction says little or none. my exhaust sounds great and with age will only sound better! the weight factor for me is that this car is just about perfectly balanced front to rear and corner to corner and I LOVE the way it handles, so will keep BIG muffler so the balance stays the same, otherwise that would be more weight on the front. as for see that big ass muffler from the back? I just sprayed it with matte black engine paint, cannot even see it now. If I paid 800+ for an exhaust system and it sounded like stock or crap that would SUCK! $$ better spent in other areas......my 2 cents

[Michigan1LTRS]

Amen Rick!!

[Adp2017]

Mishimoto ran test and noticed no restriction compared to their catback exhaust. I have a catted DP installed for a week now and put 1000km's on it. The exhaust sound has depended and there is some nice pops and burbles coming from the stock suitcase now. If I didn't already throw down some good $$ for a magnaflow catback I would keep stock exhaust and paint it black like rickwelch69 did.

[BomberCamaro]

Originally Posted by rickwelch69

I did a catless downpipe and still have the stock exhaust, most everything I've seen online about restriction says little or none. my exhaust sounds great and with age will only sound better! the weight factor for me is that this car is just about perfectly balanced front to rear and corner to corner and I LOVE the way it handles, so will keep BIG muffler so the balance stays the same, otherwise that would be more weight on the front. as for see that big ass muffler from the back? I just sprayed it with matte black engine paint, cannot even see it now. If I paid 800+ for an exhaust system and it sounded like stock or crap that would SUCK! $$ better spent in other areas......my 2 cents

That's an awesome idea Rick, I'll probably go the same route. Thanks for the input!

[ChicagoTommy]

Originally Posted by Adp2017

Mishimoto ran test and noticed no restriction compared to their catback exhaust. I have a catted DP installed for a week now and put 1000km's on it. The exhaust sound has depended and there is some nice pops and burbles coming from the stock suitcase now. If I didn't already throw down some good $$ for a magnaflow catback I would keep stock exhaust and paint it black like rickwelch69 did.

That doesn't seem right to me. There are only 2 possible theories. Either GM mad a BAMF hella flowing exhaust from the factory, which is unlikely. Or Mishi who last I checked wasn't an exhaust company, has a product with poor flow. That seems much more likely. Why would anyone fork over their hard earned money for an exhaust that doesn't flow better than stock? That would be downright negligent.

To the OP, just keep the stock muffler if you drive that much per month and don't want to listen to drone. I'd advise you to either install an electric, or a boost referenced exhaust cut out right after the downpipe. You would pick up more flow and RWHP, and you can keep the car quiet for those long rides.

[BomberCamaro]

Originally Posted by ChicagoTommy

That doesn't seem right to me. There are only 2 possible theories. Either GM mad a BAMF hella flowing exhaust from the factory, which is unlikely. Or Mishi who last I checked wasn't an exhaust company, has a product with poor flow. That seems much more likely. Why would anyone fork over their hard earned money for an exhaust that doesn't flow better than stock? That would be downright negligent.

To the OP, just keep the stock muffler if you drive that much per month and don't want to listen to drone. I'd advise you to either install an electric, or a boost referenced exhaust cut out right after the downpipe. You would pick up more flow and RWHP, and you can keep the car quiet for those long rides.

I have to agree with you that either Mishimoto fell short on designing an exhaust system, or there was some false info posted somewhere for him to find. Like you I agree there is an extremely small chance that GM got it perfect with that large of an application haha.

Regardless, I had considered an electric cutout, but have heard many stories of the motors burning up in them from exhaust heat, some as early as a few months after install. I know QTP makes a nice product, but the thought of it going toast on me sways me away from that route. I'll have to do some research on boost referenced cutouts.

[DarkFangz1100]

Originally Posted by ChicagoTommy

That doesn't seem right to me. There are only 2 possible theories. Either GM mad a BAMF hella flowing exhaust from the factory, which is unlikely. Or Mishi who last I checked wasn't an exhaust company, has a product with poor flow. That seems much more likely. Why would anyone fork over their hard earned money for an exhaust that doesn't flow better than stock? That would be downright negligent.

To the OP, just keep the stock muffler if you drive that much per month and don't want to listen to drone. I'd advise you to either install an electric, or a boost referenced exhaust cut out right after the downpipe. You would pick up more flow and RWHP, and you can keep the car quiet for those long rides.

I think Mishimoto fell off with the exhaust because I bugged them for about 3 weeks requesting an update but the guy never replied to the thread but posted on others. So, I have lost all faith with their exhaust production.

[Ashium]

I don't think anyone has measured out the stock system in detail. It seems the stock system is a 3" that y's into 2, 2.25" pipes. Two 2.25" pipes is bigger (not by much) then a single 3". In other words, You are not really going to find any power in the stock pipes. It's kind of hard to believe the muffler alone could be that big of a restriction. I'd like to see a muffler cut open, but I don't think Mishi was wrong.

Weight reduction in the system would more then likely be the biggest advantage.

[Corner carver]

Originally Posted by Ashiu

I don't think anyone has measured out the stock system in detail. It seems the stock system is a 3" that y's into 2, 2.25" pipes. Two 2.25" pipes is bigger (not by much) then a single 3". In other words, You are not really going to find any power in the stock pipes. It's kind of hard to believe the muffler alone could be that big of a restriction. I'd like to see a muffler cut open, but I don't think Mishi was wrong.

Weight reduction in the system would more then likely be the biggest advantage.

If its anything like the new mazda miata's suitcase it just dumps the exhaust into that giant chamber and lets the flow figure its own path out the two tips... Far from effecient, but likely great at sound suppression and cheap as dirt for GM to use...

[Corner carver]

Stock Miata muffler showen on the bottom... I'm assuming ours is similar

[Evil-Bee-NH]

I'll stand on the stock muffler is restrictive as hell side of the room. not to mention heavy and ugly as sin. I don't expect gains off of most cat-backs with this car but better sound and flow are 100% expected mishimotos leave a lot to be desired and I really do like them just this may have been a step in the wrong direction for them. As for drone axle-backs without modification of the stock midpipe shouldn't have any drone if you replace the mid-pipes they may drone not sure. As for cutouts i'm still so very torn on these I love the idea and understand the concept on what they're suppose to help with. I was looking at QTP's then took a look at the Noweeds diverter and find myself leaning closer to noweeds if I can confirm fiment of the universal application.

[Joe_A]

Anyone that replaced the suitcase muffler still have the original one laying around.
My be worth cutting opening up and seeing what is inside the original muffler. Might be able to remove some baffles and insulation and get something that sounds better and less restrictive for a lot less money just by modifying the stock muffler