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Old January 4th, 2010, 01:19 AM  
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True Dual Exhaust

as i was talking about making custom precats/j pipe for my car with a buddy of mine who owns a well known performance shop around illinois.

we started talking about him just doing a 2.5 inch pipe from both sides getting rid of the stock precats. so the car would be catless basically. he also would add 1 resonator on each pipe and one muffler at the end of each pipe as well.

his other idea was doing a 2.5 from each stock precat, eliminating the j pipe. he said that would cause enough backpressure and that would keep the CEL away, andd also i wouldn't need any mufflers or resonators, cuz it would be as loud as my current setup which is just a 2.5 inch straight pipe from j pipe.

chime in ur ideas guys i wanna make this happen. he also has a dyno dynamics dyno that we could work with. so help me out guys

thanks a lottt
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Old January 4th, 2010, 01:33 AM  
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wow, this will be nice, just with giving us another source for pre-cat deletes will be awesome
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Old January 4th, 2010, 01:44 AM  
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exactly. or maybe even keeping the stock precats if doing this setup. cuz stock precats would provide enough back pressure. i just need ideas and im willing to be test dummy lol.
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Old January 4th, 2010, 02:15 AM  
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exactly. or maybe even keeping the stock precats if doing this setup. cuz stock precats would provide enough back pressure. i just need ideas and im willing to be test dummy lol.
actually this has already been done before. dual 2.5 pipes would be overkill IMO. i think you would be better suited with 2.0 all the way back.

in regards to keeping the stock precats, your still going to need resonators + mufflers cause trust me, its going to be wayyyyyy louder than your current setup. i dont see how your buddy thinks its going to sound the same

here are some pics of sick6speeds dual setup that was done over 4 years ago and yes, his car was LOUD as fvck

its full custom piping from stock cats back, 2.0 iirc, into tanabe mufflers.











i thought it was a real clean setup, but i would have done the piping differently in the rear. not a big fan of it.
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Old January 4th, 2010, 02:19 AM  
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all the work was done at labree motorsports. his work is second to none and he's the one that made my custom jpipe a few years back.


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Old January 4th, 2010, 02:40 AM  
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yup i was just reading up on that actually on azine. and i was about to PM u.

do u think theres gonna be a drastic power difference between this and my current setup?

2.25 sounds ideal to me for this setup, especially if i did a muffler on each tip with no resonators.
and about that H pipe, is that needed?
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Old January 4th, 2010, 08:12 AM  
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I don't remember your current set-up (apologies) but are you planning on doing some heavy forced induction or much bigger displacement?

Dual 2.5" is a LOT of flow for 3.0L of displacement. My worry is that you would lose a lot of usable power under the curve, for a (possible) small increase in the peak #.

There is a lot of engineering that goes into an effective exhaust design, and bigger isn't always better. It all comes down to flow velocity versus flow volume, and my worry is that your guy isn't taking some thermodynamics laws into effect.

Here is a very basic idea without going into Reynolds #'s or anything silly like that (***I'm no expert, just done a lot of research for my other cars***)

The circular area of your pipes would be as follows.
Single 3" pipe = 3.14x1.5"x1.5"=7.07"

Dual 2" pipe = 3.14x1"x1"=3.14"x2=6.28"
Dual 2.25" pipe = 3.14x1.125"x1.125"=3.97"x2=7.94"
Dual 2.5" pipe = 3.14x1.25"x1.25"=4.91"x2=9.82"

Basically, by going to dual 2.5", you are adding almost 40% more flow vs a single 3"!

For another simple comparison, a 3.0L engine making much more power than ours, and one that's even more sensitive to exhaust restrictions (2JZ-GTE) seems to have a rule of thumb of about 650 rwhp. More than that, go to single 4", less than that, use a single 3".

The fact that this 3.0L motor can make over 650 rwhp on a single 3" exhaust, tells me dual 2.5's is WAY too much for your application.

If you HAVE to go true duals (remember you'll also be adding about 30-40lb worth of piping and muffler plus the cost of extra welds, extra tubing, and an extra muffler) my vote would be on two 2" (or even 2-1/4).
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Old January 4th, 2010, 09:40 AM  
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i dont have a problem going 2". i just wanna know if its effective at all. i wanna know if itl be worth it doing a true dual on my practically stock j30a4
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Old January 4th, 2010, 10:43 AM  
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IMHO, no.

The dual 2" adds a lot of weight that would need to be overcome by the (hoped) gains.

If ultimate power were your main goal, I'd like to see a single 3" pipe (run with as little bending as possible) all the way back to a single 3" canister muffler (non baffled).

That should give you the highest peak HP #, with a possible loss to tq and power under the curve.

Either way, the J-pipe is a sizable restriction & I'd take care of that before spending any more money on the rest.
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Old January 4th, 2010, 10:49 AM  
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to be honest, cubanbob got close to 250 whp with stock j pipe and precat deletes with custom exhaust. i think if anything, i would rather buy precat deletes than j pipe.

a single 3 inch would be nice aswell. but at that point id rather stick with the 2.5 inch for now. im curious if that dude with the true dual made any power
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Old January 4th, 2010, 10:57 AM  
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yo Sean where is that place at... that is some nice work...
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Old January 4th, 2010, 11:50 AM  
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to be honest, cubanbob got close to 250 whp with stock j pipe and precat deletes with custom exhaust. i think if anything, i would rather buy precat deletes than j pipe.

a single 3 inch would be nice aswell. but at that point id rather stick with the 2.5 inch for now. im curious if that dude with the true dual made any power
Any reason why you are trying to stick with the stock J-pipe?

If you were willing to build/buy a complete new exhaust to eliminate (at best) a tiny restriction when yours works pretty well as-is, why avoid the minor cost and major restriction removal by sticking with the stock j-pipe?

This isn't a plug for Richie, get your shop to make as far as I am concerned, but I'm just curious why?

From your dual 2.5" idea it seems to me you're not going for torque or power under the curve, so if peak HP is the most important, you are leaving an awful lot of it on the table with the stock J-pipe.

And as far as Cubanbob goes, 250whp is impressive, no doubt, but he could just as easily be at 255 or 260 with an improved J-pipe. I don't think I've seen a dyno yet where Richie's piece lost any power.
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Old January 4th, 2010, 11:57 AM  
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so sick
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Old January 4th, 2010, 02:32 PM  
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No one has dyno'd a 3" exhaust on the Accord before also, we don't know how much that added on Cubanob's car. The Precats also add a lot of power. We have 1 other dyno (Richie's) with all the mods and compared to ANOTHER Accord 6MT, which isn't a good comparison because it's a different car.

I would like to do a dyno with my current mods. Still different place different dyno, but at least SOME comparison. Maybe sometime soon if I get a full time job in that time!

Six: If I were to go TD, no larger than 2.25". Even if you boosted I'd still keep the dual 2.25". I think there should be some good power gains out of it. No you don't need the 'H' or 'X' pipe, but it will sound like a Civic on 3 cylinders if you don't; because you'd have 3 cylinders going through each pipe! Also, it wouldn't be worth it to stick with the stock Precats and do the true dual IMO. There is a LOT of power added with the Precat Deletes.
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Old January 4th, 2010, 03:28 PM  
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= rice
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Old January 4th, 2010, 05:12 PM  
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^ if it makes more power its not rice
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Old January 4th, 2010, 06:14 PM  
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I just don't understand why you are so against getting an after-market jpipe. I guess if you go true dual and do custom piping for the pre-cats it won't matter but if you keep them you'd really see better gains with an aftermarket jpipe to go along with your exhaust. Trust me when you take off the stock one you'll understand, it is small in diameter and there is a huge crush in one of the pipes that is a severe restriction.
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Old January 4th, 2010, 07:28 PM  
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Just my opinion: I would start with the precat deletes, then the j-pipe, then worry about the exhaust. I would go in that order.
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Old January 4th, 2010, 08:30 PM  
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archangel thats the smartest idea.

but the thing is in my opinion, i see the j pipe gaining MAX about 3-5 whp. spending 300 bux on that just isn't worth it to me. i looked at the stock j pipe. and it seems like its 2.5 inch and nicely built, only problem with stock j pipe is the third cat which has an opening of like 1.75 inch, but my third cat is gone anyway, so i really dont see why i would spend that much for a j pipe.

Precat deletes i can def see helping and i agree with those. but the reason im looking at true dual is because precats are like 300 bux as well, but technically their just a piece of pipe which i can get made for 150. so im just seeing whats a good cheap way to make a solid exhaust. true dual may be over kill, it may be a breakthrough.

and yea sonnick so that would mean h pipe or x pipe is needed lol :-p
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Old January 5th, 2010, 10:10 AM  
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Six: The Jpipe is not meant to provide great PEAK horsepower gains. Where the Jpipe really shines is the power UNDER the curve. Basically, this means low/midrange torque. The difference between 2500-4000 RPM is almost 20-30 WHEEL torque on the TL with the ATLP V2. The XLR8 about the same, if not slightly more. RV6 Jpipe saw similar gains as well below the curve. If you are expecting 10whp out of the Jpipe you are mistaken. But, like you said probably in the realm of 4-5whp PEAK, but MUCH more under the curve. IF you look at the STi, WRX, Evo, E36 M3, etc..cars that are somewhat in our class, you will notice they all have a much better torque band than we do. Unfair because 3 of them are turbo lol, and can gain 100wtq just from an ECU, but you get the idea. We can't touch any of those cars from a low roll (unless stock) because of this. The Jpipe adds good low/midrange torque to help our torque difficieny.

Also...yes the OEM Jpipe isn't THAT bad in design, but aftermarket is much better. There are crimps in the piping, different piping diameters all over the place, which all slow down the air velocity. Air velocity is CRITICAL in producing low end torque, and that is why a better flowing Jpipe is a NECESSARY, yes necessary, part of your FULL aftermarket exhaust.
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Old January 5th, 2010, 10:55 AM  
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^yup mbr explained to me that the j pipe isn't really for top end power but more for making a more solid powerband which i understand.

anyways before i would get j pipe i would rather live with the rasp and getmyself some pcds. and even more so before that i wanna see what would happen if i just had my friend make me my own precat deletes.

how big is the diameter of your precat deletes sonnick?
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Old January 5th, 2010, 01:26 PM  
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2.25" primaries. WAY bigger than the factory precats. I had a comparison picture but for some reason can't get it on the comp. It's a big difference. If you can get your boy to do it cheaper then go for it, let us know how it turns out. You WILL need a resonator. If it's loud now, it's gonna be absurd after the deletes.
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Old January 5th, 2010, 02:29 PM  
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anyways before i would get j pipe i would rather live with the rasp and getmyself some pcds.
I think several people in this thread have given you more than plenty advice about this

some people are just dense
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Old January 5th, 2010, 03:06 PM  
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^
its not like i disagree with the j pipe. im just saying before j pipe i would get precat deletes.
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Old January 5th, 2010, 03:19 PM  
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any plans to dyno soon? looks sick BTW?
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Old January 5th, 2010, 03:37 PM  
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I went Exhaust and then JPipe. Exhaust was a nice gain, but ATLP v2 JPipe + Race Pipe was like a torque eruption. I'm in Cali so I probably won't do the PCD's unless I get a high flow 3rd cat, but JPipe is definitely a fun toy for the v6.
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Old January 7th, 2010, 04:00 PM  
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How hard are the pre-cat deletes to install anyway? I can see the one banking off the cylinder head fairly easily and don't think getting to that one would be too hard but I'm wondering about the 2nd one. Sonnick?
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Old January 8th, 2010, 10:55 AM  
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How hard are the pre-cat deletes to install anyway? I can see the one banking off the cylinder head fairly easily and don't think getting to that one would be too hard but I'm wondering about the 2nd one. Sonnick?
well i recently installed some deletes on my car and its funny i was sitting there for almost 45 mins trying to take out the factory cat in the back by the firewall and my buddy suggested to remove the heat shield and wut do you kno the thing came right out lol so i suggest removing the heat shield and it should come right out if not then require significantly less effort
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Old January 9th, 2010, 02:07 PM  
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here are some pics of sick6speeds dual setup that was done over 4 years ago and yes, his car was LOUD as fvck


Drew's car was deafening.
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Old January 9th, 2010, 02:14 PM  
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Dyno-d yesterday. I don't have a scanner so I can't post the results this second, but I peaked at 231 HP, 198 lb/ft. It was pretty consistent for all 3 runs. HP was totally linear from 2.5-6.5k rpms. TQ was flat all the way across. This is with NVA-V6 Short Ram Intake, ATLP v2 JPipe, ATLP Race pipe, 2.5" exhaust. The exhaust might be 2.25" though, owner told me 2.5 but i found a post where he said it was 2.25". Either way I might move towards a 3" soon.
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