Exhaust GURU's Take a look.
06-09-2011, 04:29 PM
#1
Staging Lane
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Exhaust GURU's Take a look. Well long story short, I have a Grand National with a stock 6.0-lq4.
Now for the long part of the story.
I swapped out my factory GN exhaust with a single 3" exhaust system which I made.
I have the exhaust manifolds from a firebird (for fitment).
My concern is with my Y-Pipe.
Essentially, my exhaust pipe(2-1/4") on the drivers side comes down and back just enough to cross under the torque converter.
Then it goes strait across and merges side by side with the Passenger side exhaust pipe(2-1/4") directly into a 3" pipe(which is made oval to match up). It then goes back about 15" before meeting up with the rest of the 3" system, which continues back and over the axle and out the rear with a magnaflow 5X8 oval-14" long with 3" in/out at the end.
Biggest problem is the massive amount of torque that was lost from the previous system.
The previous system: drivers side same. except it T'd strait into the passenger side. (all 2-1/4") Then continued back for about 18-20" all collected in a single 2-1/4" before splitting into the factory GN exhaust of duel 2-1/4" over the axle into single muffler out to duels tips.
After the fact, I have now read up a lot on exhaust velocity and how important it is for tuning your torque curve regarding scavenging. However, I kinda need to know what lengths the y pipes should be when they meet or if changing the Y-pipe size is best or even returning to the single 2-1/4, for a certain length, before dumping into the 3"
Everything I have built has been turbo so all my knowledge for N/A is book stuff. I eventually will turbo this car but, in the meanwhile I want my bottom end back! This is a Daily Driver.
I hope this isn't too confusing I just typed while I was thinking.
Joe
Now for the long part of the story.
I swapped out my factory GN exhaust with a single 3" exhaust system which I made.
I have the exhaust manifolds from a firebird (for fitment).
My concern is with my Y-Pipe.
Essentially, my exhaust pipe(2-1/4") on the drivers side comes down and back just enough to cross under the torque converter.
Then it goes strait across and merges side by side with the Passenger side exhaust pipe(2-1/4") directly into a 3" pipe(which is made oval to match up). It then goes back about 15" before meeting up with the rest of the 3" system, which continues back and over the axle and out the rear with a magnaflow 5X8 oval-14" long with 3" in/out at the end.
Biggest problem is the massive amount of torque that was lost from the previous system.
The previous system: drivers side same. except it T'd strait into the passenger side. (all 2-1/4") Then continued back for about 18-20" all collected in a single 2-1/4" before splitting into the factory GN exhaust of duel 2-1/4" over the axle into single muffler out to duels tips.
After the fact, I have now read up a lot on exhaust velocity and how important it is for tuning your torque curve regarding scavenging. However, I kinda need to know what lengths the y pipes should be when they meet or if changing the Y-pipe size is best or even returning to the single 2-1/4, for a certain length, before dumping into the 3"
Everything I have built has been turbo so all my knowledge for N/A is book stuff. I eventually will turbo this car but, in the meanwhile I want my bottom end back! This is a Daily Driver.
I hope this isn't too confusing I just typed while I was thinking.
Joe
06-09-2011, 05:38 PM
#2
10 Second Club
Just to compare....
My 2005 Silverado (LQ4) has 3" duals (looks like 3") all the way back to the muffler and then a single out. This is a 6-7000# 2500HD and the torque is good.
On my Camaro with the 406 (old school motor) I have 2.5" duals with an H-pipe...no need to mention TQ here
I think you will need to step up the pipe size right at the manifolds/headers and make a merge box to connect to your 3" single ???
My 2005 Silverado (LQ4) has 3" duals (looks like 3") all the way back to the muffler and then a single out. This is a 6-7000# 2500HD and the torque is good.
On my Camaro with the 406 (old school motor) I have 2.5" duals with an H-pipe...no need to mention TQ here
I think you will need to step up the pipe size right at the manifolds/headers and make a merge box to connect to your 3" single ???
06-10-2011, 03:54 AM
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Staging Lane
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Yea but it was also crinkle bent rust bumped inside and the muffler was rotted and all the baffles were just laying in the bottom of the muffler. I think the 3" is good for the 300hp I got. I believe it's the y-pipe tune thats the problem.
What's your thoughts
What's your thoughts
06-11-2011, 02:12 AM
#7
Staging Lane
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No, but I can run dual 2.5" side by side all the way back to the beginning of the exhaust at the crossmember. The crossmember only has room for the exhaust on the passenger side. Plus I will go turbo eventually and only need single exhaust.
thanks
Keep Ideas flowing
thanks
Keep Ideas flowing
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06-11-2011, 03:46 PM
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Staging Lane
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Does anyone have some hard data on velocity of the exhaust and what pipe size and how long they should be to get better low end torque for the stock 6.0
06-11-2011, 04:33 PM
#11
I Totally agree. Unfortunately I've been STUCK in Hawaii on vacation for two weeks. I'll be back around the 16th or so.
Does anyone have some hard data on velocity of the exhaust and what pipe size and how long they should be to get better low end torque for the stock 6.0
Does anyone have some hard data on velocity of the exhaust and what pipe size and how long they should be to get better low end torque for the stock 6.0
06-11-2011, 04:51 PM
#12
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Different combination but I substantially free'd up my exhaust and made more torque - I had headers running into cats into 2.25 full dual all the way back (functionally my stock BMW exhaust system from the cats back)
I went to a pair of 2.5" spun cats, a 2.5 dual into single 3" spintek suv muffler and 3" all the way back - back to back dyno difference was 10 more lb/ft across the ENTIRE power band with the bigger exhaust and more peak hp as well.
getting every little bit out of an exhaust can take tons of calculations and testing but getting a fairly good, make it fit under the car setup is fairly standard across any engine application.
if i'm understanding your application why don't you just run an x-pipe and leave dual 2.25 throughout and get rid of that 18-20" section of single 2.25 pipe. or if you now have the 3" back system run a y-pipe or a good 2 into 1 muffler as a y pipe from the 2.25 and back to the 3" system
I went to a pair of 2.5" spun cats, a 2.5 dual into single 3" spintek suv muffler and 3" all the way back - back to back dyno difference was 10 more lb/ft across the ENTIRE power band with the bigger exhaust and more peak hp as well.
getting every little bit out of an exhaust can take tons of calculations and testing but getting a fairly good, make it fit under the car setup is fairly standard across any engine application.
if i'm understanding your application why don't you just run an x-pipe and leave dual 2.25 throughout and get rid of that 18-20" section of single 2.25 pipe. or if you now have the 3" back system run a y-pipe or a good 2 into 1 muffler as a y pipe from the 2.25 and back to the 3" system
06-12-2011, 02:49 AM
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Yea I now have the (2)2.25" run right into the 3" as soon as they meet. I think the exhaust needs to stay in the 2.25" a little longer (to scavenge) before it dumps in the 3"
I like your Idea Doug G
Any other Ideas appreciated.
I like your Idea Doug G
Any other Ideas appreciated.
06-12-2011, 11:13 AM
#14
Um... That is a $500 part Doug! Not trying to be cheap but I like to work in budgets... Why not use a Flowmaster Merge for 10% of the price instead of the one from Dynatech?
I agree. How about you come here, work my job for the next two weeks and I'll chill in Hawaii on vacation for the same time. We can simply trade lives for a couple weeks. 
06-12-2011, 02:44 PM
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Staging Lane
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Yea as far as the part goes I'll just make my own. I'm working on my welding "skills"
As far as the pipes go....focusing on torque.
What would be the best combo:
(2) 2.25" all the way back to the crossmember where it'll merge directly into the 3".
Or Merge the the 2.25 as a normal y-pipe (right where it crosses under the trans) into a 2.5 then back to the crossmember where it'll merge into the 3"
Remember looking for my torque back.
GoFastWClass I only got two days left. I most likely won't get another real vacation for another 2-3 years. So, I'm keeping this one. lol
As far as the pipes go....focusing on torque.
What would be the best combo:
(2) 2.25" all the way back to the crossmember where it'll merge directly into the 3".
Or Merge the the 2.25 as a normal y-pipe (right where it crosses under the trans) into a 2.5 then back to the crossmember where it'll merge into the 3"
Remember looking for my torque back.
GoFastWClass I only got two days left. I most likely won't get another real vacation for another 2-3 years. So, I'm keeping this one. lol
