I was considering 3.5" before as well but then when I couldn't find a good presilencer in 3.5" in oval form decided to go 4" which Borla has a nice big oval that fits just perfect (although tight). The 3.5" would have been a canister which would have stuck out under the car since it was 6.25" tall (if I remember correctly) which I did not want.

thewird

 

I've seen similar results myself, this is why our turbo kits come with 3.5" downpipes standard....

 

my borla is 3.5 in and oval????? fits perfectly!

 

http://www.streetsideauto.com/p/borl...GoogleShopping


I got mine as a blem for about 80 bucks because there was some plastic melted onto a small spot of it.... this is it tho... then magnaflow out back.

Elliot I am very happy with 3.5 in! thanks I'm sure I will be even when i put my dump tube back into the exhaust!

 

Since I wanted the best sound suppression, I wanted their XR-1 multi-core and not the sportsman. Yes, there is a 3.5" oval in the sportsman variety but I chose to go 4" to get the multi-core.

part #400069 http://www.borla.com/products/produc...?cat=5&type=76

Also, if anyone is interested, Borla claims their XR-1 mufflers are built to withstand great sustained temps. "They can with stand constant temps of 2400 degrees with short burst of 2800 degrees.".

thewird

 

Im going 4" on my car also. T04Z 1.06 rear housing.
currently 3.5" into twin 2.5" withon eresonator each side then back into single 3.5" wiht one big rear carn
now im going to 4" dump into existing rear, but then also doing a striaght through 4" section to replace the mid twin 2.5" section for track work, will have also converted all joins to v band.
wastgates feed back into current 3.5" dump, but going to change it so when current mid section is used, WG feed back into mid section, then when runnign 4", WG will vent to at.

 

All this talk about bigger exhaust got me a thinkin'! I'm currently 3" all the way back Magnaflow in the midpipe and RB duals in the back... wonder how much power is being left on the table.

 

zaridar did you have any luck with your ticket? That sounds pretty loud to me lol

 

I didn't end up showing the judge the video... however I did get the ticket dropped since i have Hobbyist plates... The District attorney was a dick and upset when the judge said im throwing this out Haha

 

that articles pretty cool, but a 3.5 would only make gains on cars with higher hp right?

 

that articles pretty cool, but a 3.5 would only make gains on cars with higher hp right?

If the car has a turbo there will be gains from the larger exhaust.

An issue with a smaller turbo (I assume what you mean by lower hp car) will be that the gains are so great you will not be able to control the boost creep with the wastegate(s) you have.

 

While we are on the topic of larger exhaust for performance and possibility of increased decibels does wrapping the downpipe have an audible impact?

I know its for heat management but I was curious if anyone noticed a decrease in sound.

 

I used to have a ceramic coated and thermo wrapped 3" downpipe with twins, it was much quieter than the 4" naked one I have now. But only in the engine bay area.

 

I had a 4" all the way back with 2 magnaflow mufflers on my 20b and it was loud as hell. How much power will I lose if I go 4" dp and mp and a 3" racing beat cb? I don't mind upping the boost to make up for the loss if the noise is reduced....

Any thoughts?

 

why not 4" dp with 3.5" mp and cb? it's what I have from SMB and it's moderately quiet. of course I'm still on stock twins!

 

Stock twins themselves act as a fairly good muffler especially in sequential. I remember when I installed the aspec 500r-sp the car got noticbly louder with nothing else changed

thewird

 

If you have an open WG, I would be willing to bet it would only cost you 4 % power.

 

The gains where really beneficial above 500rwhp as stated in the article. Also consider this, larger exhaust will lower your spool time even with low rwhp. These are all pluses. Only negative is keeping it quiet the bigger you go.

 

True but if you think about it i would assume that a 500whp rotary engine is moving as much air as a 650whp piston engine.

 

Thanks for all the tips even though this is not my thread. I noticed I have a 4 in dp going to a welded cat which is welded to a 4 in cutoff and that continues to a welded 3.5 in y pipe which leads to a 3 in split exhaust with flowmaster tips. Should I make the y pipe and piping to the tips 3.5 in? Or keep them their respective sizes

 

Thanks for all the tips even though this is not my thread. I noticed I have a 4 in dp going to a welded cat which is welded to a 4 in cutoff and that continues to a welded 3.5 in y pipe which leads to a 3 in exhaust with flowmaster tips. Is that a good setup for my 13b-t with full bolt ons and top mount

 

I run a full 4" exhaust that is actually relatively quiet. The trick was splitting it into dual 3" at the mufflers, which has more cross-sectional area than a single four, while also having a much higher muffled surface area. I built the mufflers and rolled the perf tube myself to ensure as much sound reduction as possible and the end result was better than expected!

 

pictures? im very interested plus your a local

 

Nice i would also like to see pictures!

 

Some more food... This is at ~300 rwhp power levels and it had gains of 15 rwhp going to a 4" from a 3". Can't wait for spring when I get to test my new 4" exhaust

http://www.turbo944.com/bbs/config.c...ames;read=3942

thewird