Age old debate.. 2.5" vs 3" exhaust...

[Lstruck03]

Well, the time has come that I feel I need to do exhaust upgrades. On my current setup, I made 700/767 with kooks 1 5/8" lt's, 2.5" o/r prochamber and 2.5" bassani's dumped.

My thinking is that at my power level, there will be power to be had by switching to a 1 3/4" to 1 7/8" stepped header and full 3" exhaust with magnaflows. Somewhere around 20hp would be perfect.

thoughts?

 

[mach1033]

What is your current set up engine wise? I'm going with 17/8 kooks with 3 inch Dr gas x pipe and magnaflow 3 inch race mufflers through 3 inch dynomax tails. My engine will finally be done next month and it will have an eagle crank, stock rods, diamond pistons, custom cams, stage 3 port, return fuel and topped off with a whipple 2.9 with a 3.2 pulley.

 

[Lstruck03]

my current setup is 2.3 whipple at 23psi, 9.5:1 284cid teksid, cnc navi heads with big valves, comp stg 2 cams, ported lower intake.

 

[08fordgt]

In my opinion-anything over 500hp can use 3" exhaust.
Go for it!!

 

[evolve]

Do it! Let her breathe!!!!!

 

[mach1033]

my current setup is 2.3 whipple at 23psi, 9.5:1 284cid teksid, cnc navi heads with big valves, comp stg 2 cams, ported lower intake.

Very nice!!! Which tails are you going with? I'm willing to bet you will pick up more than 20hp. Here is a mock up of my cat back
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[Silverboost]

Why not put the money towards a bigger blower instead? Sell the 2.3 and get a 3.4 or a 2.9. You would pick up more power that way instead of redoing the exhaust

 

[evolve]

This would give the best power for the $$ but since he asked about exhaust, I gave him my opinion. But you are correct^ OP: there is always Lysholm

 

[zeusha]

Depends on how much air your engine is moving and how good your heads flow. PERIOD. OVER camming or OVER exhaust does NOT help performance.

 

[8URZ-28]

Couple of questions......Who did your heads and how much do they flow? What did you have to go through to get the lower manifold to fit?

PS: I ran Kooks 1 7/8 LT with 3" x-pipe to Custom 3" catback and never looked back, so go for it!

 

[Lstruck03]

Very nice!!! Which tails are you going with? I'm willing to bet you will pick up more than 20hp. Here is a mock up of my cat back
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well my car has a SRA so I will be using the 3" flowmaster kit for 79-93 cars and modify the rear hangers and replace the mufflers with the same mufflers you have.

Why not put the money towards a bigger blower instead? Sell the 2.3 and get a 3.4 or a 2.9. You would pick up more power that way instead of redoing the exhaust

while that is true, I can spend less than a grand out of pocket and pick up another 20-30hp with my current setup. a power adder change is not financially available right now.

This would give the best power for the $$ but since he asked about exhaust, I gave him my opinion. But you are correct^ OP: there is always Lysholm

i thought about lysholm, but they are not offering the killer price anymore! Plus, I would still need an exhaust upgrade.

Depends on how much air your engine is moving and how good your heads flow. PERIOD. OVER camming or OVER exhaust does NOT help performance.

believe me, the heads are flowing plenty and my engine is pretty effecient. My 2.3 is pullied for 25psi (2.75/4lb gen 2) and it peaks 22 on cold days. 21 in normal weather.

Couple of questions......Who did your heads and how much do they flow? What did you have to go through to get the lower manifold to fit?

PS: I ran Kooks 1 7/8 LT with 3" x-pipe to Custom 3" catback and never looked back, so go for it!

m2 race systems did the heads. The flow sheet looks amazing. they flow over 300cfm on the lift of my cams (.475") For the intake, we had to put it on a mill and take material off in between the ports to fit on the navi heads, then we port matched to the navi gaskets and had to trim the gaskets as well since the coolant ports are different.

 

[8URZ-28]

m2 race systems did the heads. The flow sheet looks amazing. they flow over 300cfm on the lift of my cams (.475") For the intake, we had to put it on a mill and take material off in between the ports to fit on the navi heads, then we port matched to the navi gaskets and had to trim the gaskets as well since the coolant ports are different.

Nice! I figured it was alot of work. My plans are to run GT Supercar heads with big blower but gotta figure out how to make this lower work.

 

[evolve]

Depends on how much air your engine is moving and how good your heads flow. PERIOD. OVER camming or OVER exhaust does NOT help performance.

I would have a hard time considering a 3" exhaust too much.

 

[speeddemon2000]

Very nice!!! Which tails are you going with? I'm willing to bet you will pick up more than 20hp. Here is a mock up of my cat back
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Can you post up some more details on this setup? It' pretty sweet.

 

[mach1033]

Can you post up some more details on this setup? It' pretty sweet.

I dont want to hijack the OP thread but I will have a new thread started once my motor is done with pics and video of the installation and tune. I'm also gonna do a Borla 3 inch cat back and see how that sounds.

 

[Competition]

I think at your power level you will benefit having a 3" system over a 2.5" though with less power like I have, I think 2.5" is better. My car makes 444rwhp and had a 3" MAC system on it. I recently swapped it out for a 2.5" Magnaflow Magnapacks setup and the car feels like it has more power now.

 

[KINGCOBRA86]

If any one could benefit from a 3" setup it would be your combo.

If and when you want to sale your lts pm me

 

[Lstruck03]

I think at your power level you will benefit having a 3" system over a 2.5" though with less power like I have, I think 2.5" is better. My car makes 444rwhp and had a 3" MAC system on it. I recently swapped it out for a 2.5" Magnaflow Magnapacks setup and the car feels like it has more power now.

I agree. I had a mac 3" at one point when I was at 517rwhp with a port, and switching to dumped 2.5" bullets made the car feel a bit faster.

If any one could benefit from a 3" setup it would be your combo.

If and when you want to sale your lts pm me

true. And I believe I will start buying the parts I want. I sent a pm about the headers.

 

[GodStang]

Some things to think abou some cars have the have an aftermarket kmember to run 1-7/8" so when looking at price think about that. Swapping from 1-3/4" and 2.5" system to 1-7/8" and 3" system cost me $4K. Pulleying a 2.3L for 25psi is extremely bad for it and most likeily will not last long. So you may want money on the side for that. The 2.5" is good for 650rwhp and once you hit past that point you will see bigger gains. More past that more gains you can see.

 

[Lstruck03]

Some things to think abou some cars have the have an aftermarket kmember to run 1-7/8" so when looking at price think about that. Swapping from 1-3/4" and 2.5" system to 1-7/8" and 3" system cost me $4K. Pulleying a 2.3L for 25psi is extremely bad for it and most likeily will not last long. So you may want money on the side for that. The 2.5" is good for 650rwhp and once you hit past that point you will see bigger gains. More past that more gains you can see.

I do already have a qa1 kemember, so fitment shouldnt be an issue. Also, I will not be buying the parts quite as expensive as you. Posi's group buy on kooks gets me headers shipped to me for $990, and i am buying the 3" flowmaster kit for the 86-93 lx which includes an x pipe for $570. Add a couple hundred for better mufflers and That is still less than $2k, not including the money I get in return for selling my current setup.. All labor will be done by me, so no money spent there. And I agree about the pulley on my 2.3, thus it is my race only setup. My street setup is the 3.5"/4lb that makes 16psi. I am hoping on the race tune to see at least a 20hp increase.