Let's clear-up that 3" vs 2,5" Catback thing for the LSJ.
11-13-2011, 01:32 PM
#126
Senior Member
Thread Starter
Join Date: 07-22-05
Location: Quebec City, Quebec
Posts: 1,591
Likes: 0
Received 0 Likes
on
0 Posts
Everything happening downstream of the turbo should be consider similar to a supercharged application IMO. Both are opened to atmosphere and are trying to get rid of an X amount of burned air fuel mixture (all other factors being equals such as EGT's).
11-13-2011, 02:31 PM
#127
Giving an example of a turbocharged regal gs is not a clear indicator that a 3" exhaust will make more power on the SS/SC (which is what this thread is about). Like I've said before, I agree that a 3" exhaust will make more power on some applications, but a 2.5" exhaust will still provide optimal flow and exhaust gas velocity for most setups on the SS/SC.
11-13-2011, 04:55 PM
#132
One individual recently dyno'd their LNF on a stock LNF muffler and then with a cut out. The gain was around 30-40whp...
Though, his setup was on a larger turbo if I recall... None the less, turbo'd balts would benefit much more from a open dp or opened up exhaust relative to the CFM of their setup.
Though, his setup was on a larger turbo if I recall... None the less, turbo'd balts would benefit much more from a open dp or opened up exhaust relative to the CFM of their setup.
11-13-2011, 07:07 PM
#136
so yes thats the power level. I took off the 3 inch. I did not make less power. you can look at the flow numbers already published and see unless you are trying to get above 350 with an LSJ the 2.5 is fine. LNF are different, but make over 380 wt all day on stock exhaust. the rear muffler is straight through, so replacing it is just a means of making noise not power.
I guess WS Frazer is the dyno king around here with 348 whp on an LSJ , ask him.
http://www.******************/forums...lsj-parts.html
put in red line forums.com to make the link work.
11-13-2011, 08:27 PM
#138
this is an LSJ thread. i run 320 whp on the lnf cat back. I dont publish my dyno sheets, area47 has done the work with the car and thats all i need.
so yes thats the power level. I took off the 3 inch. I did not make less power. you can look at the flow numbers already published and see unless you are trying to get above 350 with an LSJ the 2.5 is fine. LNF are different, but make over 380 wt all day on stock exhaust. the rear muffler is straight through, so replacing it is just a means of making noise not power.
I guess WS Frazer is the dyno king around here with 348 whp on an LSJ , ask him.
http://www.******************/forums...lsj-parts.html
put in red line forums.com to make the link work.
so yes thats the power level. I took off the 3 inch. I did not make less power. you can look at the flow numbers already published and see unless you are trying to get above 350 with an LSJ the 2.5 is fine. LNF are different, but make over 380 wt all day on stock exhaust. the rear muffler is straight through, so replacing it is just a means of making noise not power.
I guess WS Frazer is the dyno king around here with 348 whp on an LSJ , ask him.
http://www.******************/forums...lsj-parts.html
put in red line forums.com to make the link work.
This is what I have been trying to make clear the whole time.
11-13-2011, 08:46 PM
#139
I understand. Lnf is different platform so the same can't be said. I guess ecotecs are just kinda weird. I know with the k-series honda, you need something close to a 3" when your near 300whp. My friends m62 SI sedan gained 15 whp moving from 2.5"-3"
But that's a diff car completely.
But that's a diff car completely.
11-14-2011, 07:08 AM
#140
I understand. Lnf is different platform so the same can't be said. I guess ecotecs are just kinda weird. I know with the k-series honda, you need something close to a 3" when your near 300whp. My friends m62 SI sedan gained 15 whp moving from 2.5"-3"
But that's a diff car completely.
But that's a diff car completely.
11-22-2011, 09:26 PM
#146
Banned
Join Date: 08-24-08
Location: Nebraska
Posts: 2,103
Likes: 0
Received 0 Likes
on
0 Posts
I put an new magnaflow 14326 and at wot sounds horrible. When I installed it, it didn't have an tip and sounded deep, and now I have an tip welded on it sounds raspy. Im using jbp header, 2.5 catless dp, stock CB to the new muffler. What's an good resonator to put on? And should I replace the new res with the stock res? Or keep the stock and weld in new one on the dp?
11-24-2011, 01:19 PM
#147
Senior Member
Join Date: 06-05-05
Location: Marlborough Massachusetts
Posts: 1,181
Likes: 0
Received 0 Likes
on
0 Posts
Figured I’d post this graph here. Was having trouble getting anymore power than 408 out of my car with the 2.5” exhaust w/resonator and gutted cat due to having too much back pressure which ended up causing my resonator to explode (pictures on twincharged thread) Ended up putting on a 3” exhaust from where the cat was gutted straight back and reduced to 2.5 a foot and a half or so before the turbo to create some velocity. Also we eliminated the resonator. Car is now extremely loud and first run on dyno (not on graph) made about 350hp and lost 4psi or so. So right off the bat with the same tune I lost about 58whp just from switching to a larger exhaust. After some tuning we were able to get a best of 384hp which was AFTER we turned the boost up to 28psi. (which was 1psi more than I had before on the 2.5” exhaust making 408hp) The tune was very rich so he leaned it out a bit and lost more hp bringing us into the 360’s to 370’s as where it stand now. So the car is still at the shop til he can figure out whats going on. The only benefit shown on graph from the 3” exhaust is the power band up to 4500 rpm. After 4500 power is lost and we have no idea why.
11-24-2011, 10:42 PM
#148
As Staged says below it varies from application to application, but, easily, more than half of the M62 LSJ's on this site are not making enough power to warrant a 3", it's just not realistic, and not needed. I still have friends who drive LSJ Cobalts that will argue to the death that they need a 3".. I just let it go and carry on usually..
11-24-2011, 10:52 PM
#149
You're comparing apples to oranges here.. Of course you're resulting higher horsepower with a 3".. On a turbo car. Less backpressure, faster spool.. Power comes on faster. End of story.
As Staged says below it varies from application to application, but, easily, more than half of the M62 LSJ's on this site are not making enough power to warrant a 3", it's just not realistic, and not needed. I still have friends who drive LSJ Cobalts that will argue to the death that they need a 3".. I just let it go and carry on usually..
As Staged says below it varies from application to application, but, easily, more than half of the M62 LSJ's on this site are not making enough power to warrant a 3", it's just not realistic, and not needed. I still have friends who drive LSJ Cobalts that will argue to the death that they need a 3".. I just let it go and carry on usually..
11-25-2011, 02:26 PM
#150
Figured I’d post this graph here. Was having trouble getting anymore power than 408 out of my car with the 2.5” exhaust w/resonator and gutted cat due to having too much back pressure which ended up causing my resonator to explode (pictures on twincharged thread) Ended up putting on a 3” exhaust from where the cat was gutted straight back and reduced to 2.5 a foot and a half or so before the turbo to create some velocity. Also we eliminated the resonator. Car is now extremely loud and first run on dyno (not on graph) made about 350hp and lost 4psi or so. So right off the bat with the same tune I lost about 58whp just from switching to a larger exhaust. After some tuning we were able to get a best of 384hp which was AFTER we turned the boost up to 28psi. (which was 1psi more than I had before on the 2.5” exhaust making 408hp) The tune was very rich so he leaned it out a bit and lost more hp bringing us into the 360’s to 370’s as where it stand now. So the car is still at the shop til he can figure out whats going on. The only benefit shown on graph from the 3” exhaust is the power band up to 4500 rpm. After 4500 power is lost and we have no idea why.
There is no way you are losing that much HP at your level with a 3" exhaust over a 2.5" exhaust. Something else is wrong there...its not the exhaust.
Hell my car runs 20" of 3" pipe (3" collector) and then it dumps to atmosphere, my car is all-motor and makes 193whp. TQ was nearly 160wtq at 3000rpm as well, peak 179wtq at 4800rpm.
No loss in low end TQ or power for me.
Everyone should just run 3" cutouts and then this won't be an issue, they make more power than any exhaust combo.
Thread
Thread Starter
Forum
Replies
Last Post
Jesse
Problems/Service/Maintenance
2
09-28-2015 12:51 PM