Aftermarket Front Pipe Restriction - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

sw20kosh · 07-10-2013, 02:47 PM

Has anyone been measuring their front pipe diameters? The way they are designed to mate up to the midpipe, it looks like there is a restriction. I see it on every front pipe designed to hook up to the stock midpipe.

I was thinking of removing that small piece of pipe that is sticking out of the front pipe and using a gasket to mate up with the mid pipe. Has anyone found a solution like this?

Or am I tripin about this downsizing? I have FI and I would feel better about not having the pipe go from 2.5 ---> 2.2 just so it can interface with the stock midpipe (which is not even there on my car).

qoncept · 07-10-2013, 03:03 PM

I don't know what gains you'd see but you don't ever want to decrease exhaust diameter after the collector (or turbo). Ideally the diameter gets bigger.

mrk1 · 07-10-2013, 04:52 PM

thats really an extremely minimal reduction, its there to work with the factory donut gasket.

You could cut it off a use a normal 2 bolt gasket but the donuts allow for bit of misalignment and flex under impact. That is when they are installed correctly.

qoncept · 07-10-2013, 05:13 PM

Quote:

Originally Posted by mrk1

thats really an extremely minimal reduction, its there to work with the factory donut gasket.

It's a 20% reduction in cross section and a source of turbulence. The real world gains may or may not be worthwhile but it's clearly not ideal.

FAER · 07-10-2013, 05:30 PM

I would like to see Companys release full 3" systems with their kits. (well the kits that will make big power) no "this will bolt up to stock... blah blah.." crap

qoncept · 07-10-2013, 05:31 PM

Quote:

Originally Posted by FAER

I would like to see Companys release full 3" systems with their kits. (well the kits that will make big power) no "this will bolt up to stock... blah blah.." crap

Totally. Who is replacing their overpipe before anything else?

coyote · 07-10-2013, 05:58 PM

We sent our first brand X front pipe back and replaced it with brand Y, which we modified to ensure smooth flow from the brand Y over pipe.

We then modified the centre section of the brand X cat back to taper the step down from the brand Y front pipe.

Brand X was advertised as 2.5", but it was 60mm and less at the join. We deemed 60mm as sufficient once the gas was half way down the car and a lot cooler, but those big step downs are undoubtedly costing people power.

Why bother paying for beautiful smooth welds when at the joins you're smashing gas into a smaller pipe?

sw20kosh · 07-10-2013, 06:38 PM

yeah and it is not a smooth step down from 2.5 to 2.2. It is literally a 2.2" pipe inserted into a 2.5" pipe. There is a lip created in there with an actual gap between the two pipes of 2-3 mm all the way around.

That can't be ideal for flow? Especially if you are nearing the limits of 2.5" piping with FI... Boggles my mind. I think I'll modify mine and take out that 2.2" pipe.

coyote · 07-10-2013, 06:57 PM

Yep. It actually made me wonder, if they think that's okay ... what do the muffler internals look like?

The stuff is so much cheaper than what you could make it for yourself though.

jamesm · 07-10-2013, 07:46 PM

I installed a j2 front pipe yesterday and it doesn't have the piece out past the flange like the one in that picture (and like the stock piece has). It just mates flat to the mid pipe and overpipe.

sw20kosh · 07-11-2013, 06:36 PM

Quote:

Originally Posted by jamesm

I installed a j2 front pipe yesterday and it doesn't have the piece out past the flange like the one in that picture (and like the stock piece has). It just mates flat to the mid pipe and overpipe.

I am going to gut mine!!!!

RiskyTrousers · 08-24-2013, 05:51 PM

Does anyone not mind all the vendors advertising a 2.5" frontpipe, yet they fail to mention the 2.2" bottleneck?

I was pretty disappointed when I got my over/frontpipe to see this horrible and abrupt step down to 2.2", not to mention the craptacular fitment.

Anyway, doesnt seem like any shop is making a proper full 2.5" system, they're just letting people assume thats what they're getting. All about the $$$ I guess.

mad_sb · 08-24-2013, 06:06 PM

Quote:

Originally Posted by sw20kosh

Has anyone been measuring their front pipe diameters? The way they are designed to mate up to the midpipe, it looks like there is a restriction. I see it on every front pipe designed to hook up to the stock midpipe.

I was thinking of removing that small piece of pipe that is sticking out of the front pipe and using a gasket to mate up with the mid pipe. Has anyone found a solution like this?

.,..

Or am I tripin about this downsizing? I have FI and I would feel better about not having the pipe go from 2.5 ---> 2.2 just so it can interface with the stock midpipe (which is not even there on my car).

I've been thinking about this as well.. I know my nameless frontpipe uses the stock gasket.. I'll have to figure out what to do when i do my custom catback. I'll probably modify the nameless and the catback and leave the stock stuff alone.

sw20kosh · 08-24-2013, 06:10 PM

Quote:

Originally Posted by mad_sb

I've been thinking about this as well.. I know my nameless frontpipe uses the stock gasket.. I'll have to figure out what to do when i do my custom catback. I'll probably modify the nameless and the catback and leave the stock stuff alone.

I ended up grinding that restriction out and re-used the donut gadget. Works fine.

07-10-2013, 02:47 PM	#1
sw20kosh Senior Member Join Date: Jul 2012 Drives: 2013 Black FR-S Location: SF Posts: 3,030 Thanks: 881 Thanked 2,014 Times in 990 Posts Mentioned: 153 Post(s)	Aftermarket Front Pipe Restriction Has anyone been measuring their front pipe diameters? The way they are designed to mate up to the midpipe, it looks like there is a restriction. I see it on every front pipe designed to hook up to the stock midpipe. I was thinking of removing that small piece of pipe that is sticking out of the front pipe and using a gasket to mate up with the mid pipe. Has anyone found a solution like this? Or am I tripin about this downsizing? I have FI and I would feel better about not having the pipe go from 2.5 ---> 2.2 just so it can interface with the stock midpipe (which is not even there on my car).

07-10-2013, 04:52 PM	#3
mrk1 Senior Member Join Date: Mar 2013 Drives: Sterling BRZ Ltd Location: New England Posts: 1,702 Thanks: 403 Thanked 1,389 Times in 671 Posts Mentioned: 21 Post(s)	thats really an extremely minimal reduction, its there to work with the factory donut gasket. You could cut it off a use a normal 2 bolt gasket but the donuts allow for bit of misalignment and flex under impact. That is when they are installed correctly. __________________ The Build Thread GT28RS - eBoost2 - 3.91 Final Drive - Supra LSD

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07-10-2013, 05:30 PM	#5
FAER Banned Join Date: Mar 2013 Drives: Silver BRZ Location: Texas Posts: 361 Thanks: 22 Thanked 118 Times in 86 Posts Mentioned: 10 Post(s)	I would like to see Companys release full 3" systems with their kits. (well the kits that will make big power) no "this will bolt up to stock... blah blah.." crap

07-10-2013, 05:58 PM	#7
coyote Senior Member Join Date: Oct 2011 Drives: Slowly Location: brisbane.qld.au Posts: 1,064 Thanks: 212 Thanked 539 Times in 235 Posts Mentioned: 21 Post(s)	We sent our first brand X front pipe back and replaced it with brand Y, which we modified to ensure smooth flow from the brand Y over pipe. We then modified the centre section of the brand X cat back to taper the step down from the brand Y front pipe. Brand X was advertised as 2.5", but it was 60mm and less at the join. We deemed 60mm as sufficient once the gas was half way down the car and a lot cooler, but those big step downs are undoubtedly costing people power. Why bother paying for beautiful smooth welds when at the joins you're smashing gas into a smaller pipe?

07-10-2013, 06:38 PM	#8
sw20kosh Senior Member Join Date: Jul 2012 Drives: 2013 Black FR-S Location: SF Posts: 3,030 Thanks: 881 Thanked 2,014 Times in 990 Posts Mentioned: 153 Post(s)	yeah and it is not a smooth step down from 2.5 to 2.2. It is literally a 2.2" pipe inserted into a 2.5" pipe. There is a lip created in there with an actual gap between the two pipes of 2-3 mm all the way around. That can't be ideal for flow? Especially if you are nearing the limits of 2.5" piping with FI... Boggles my mind. I think I'll modify mine and take out that 2.2" pipe.

07-10-2013, 06:57 PM	#9
coyote Senior Member Join Date: Oct 2011 Drives: Slowly Location: brisbane.qld.au Posts: 1,064 Thanks: 212 Thanked 539 Times in 235 Posts Mentioned: 21 Post(s)	Yep. It actually made me wonder, if they think that's okay ... what do the muffler internals look like? The stuff is so much cheaper than what you could make it for yourself though.

07-10-2013, 07:46 PM	#10
jamesm Banned Join Date: Mar 2013 Drives: 2013 FR-S Location: Orlando, FL Posts: 2,929 Thanks: 1,166 Thanked 2,294 Times in 1,180 Posts Mentioned: 313 Post(s)	I installed a j2 front pipe yesterday and it doesn't have the piece out past the flange like the one in that picture (and like the stock piece has). It just mates flat to the mid pipe and overpipe.

08-24-2013, 05:51 PM	#12
RiskyTrousers Senior Member Join Date: Nov 2011 Drives: '87 Corolla GTS, '13 FR-S 6MT Location: United States Posts: 364 Thanks: 54 Thanked 146 Times in 67 Posts Mentioned: 7 Post(s)	Does anyone not mind all the vendors advertising a 2.5" frontpipe, yet they fail to mention the 2.2" bottleneck? I was pretty disappointed when I got my over/frontpipe to see this horrible and abrupt step down to 2.2", not to mention the craptacular fitment. Anyway, doesnt seem like any shop is making a proper full 2.5" system, they're just letting people assume thats what they're getting. All about the $$$ I guess.

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