homemade 2.5 mandrel exhaust pics

slipknot1212121

Registered User
well, decided to make the rest of the exhaust from the resonator back...i put the resonator on a few months ago,i got it off a supercoupe at a pick and pull, its a magnaflow but it has 2.5 out instead of 3?anyways bought one stick of 2.5 and one 2.5 small u-bend and one large 2.5 u-bend, made a y-pipe out of the small u-bend and hacked up the large u-bend for bends, not completed but tacked together,for the y-pipe i think im gona cut it at the right angle and flip it so the pipes go sideways like stock, instead of both goin straight back like in the pic,what do yall think??
 

Attachments

  • Photo_#15.jpg
    Photo_#15.jpg
    29.3 KB · Views: 787
  • Photo_#16.jpg
    Photo_#16.jpg
    51.7 KB · Views: 622
Last edited:
i know:(

but i was goin for cheapest exhaust possible! and the magnaflow only has a 2.5 out,it was only 4 dollars on a half off day.If i didnt get this one i would have bought one new and the 3 inch one.as i sit, im only 60 bucks into it, resonator back, now if i wanna add mufflers, which i think i will,thats another 100....
 
Blk89TBSC said:
Very nice but you should have went to a 3" :D


3" isn't always the answer. If you have too little back pressure you can loose power/performance, especially on our blown setups. Looks nice slipknot.
 
pablon2 said:
3" isn't always the answer. If you have too little back pressure you can loose power/performance, especially on our blown setups. Looks nice slipknot.


What? Who told you that? That is 100% wrong.

Less backpressure = More power
 
Blk89TBSC said:
What? Who told you that? That is 100% wrong.

Less backpressure = More power


Boost is a measure of back pressure. So less boost = more power? :) My point is you can over do your exhaust to a fault.
 
acb92sc said:
NOT ALWAYS TRUE. ONLY TO A CERTAIN EXTENT, THEN YOU LOOSE INTAKE PRESSURE AND POWER...

You lose intake pressure because the exhaust has become more effecient.

Take two setup's that are identical. One has a 2.5" exhaust and one has a 3" exhaust. The 3" exhaust will make more power.

That's why your boost gauge reads lower boost when you do exhaust. Your supercharger is still pumping out the same PSI it did before you opened up the exhaust. The exhaust is just more effecient.

You guys see where i'm coming from?

Edit - Here.. I found this for you

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm
 
Last edited:
I don't like the way you did the y pipe, the single pipe just dumps into that U and doesn't flow smoothly into the twin pipes. If you cut the U right in the middle and flip the pieces so they point to the sides of the car like stock, you can see how to cut each pipe on a angle so they meet in the middle. The cut can be made so the opening can match the 3" pipe (less cut larger opening, larger cuts make smaller opening). Start with less cut and trim down to the right size. Then the pipes make a nice curve from the 3" into the 2 1/2's. John
 
You can however loose low end torque with a large exhaust but in this case a single 3 inch wouldnt of been to large.

I would try to transition the rear Y pipe a little better..Thats like hitting a brick wall. Otherwise nice
 
DamonSlowpokeBaumann said:
You can however loose low end torque with a large exhaust but in this case a single 3 inch wouldnt of been to large.


A 3" exhaust is perfect for our engines. Would we lose alittle low end? Possibly but it would be gained on the top end. Something our cars desperately need.
 
When I went to a true 21/4 dual exhaust with only mufflers I lost boost. But the car wond up a lot faster. I may even go with straight pipes to the back who needs mufflers?:eek:
 
Nice Job

GOOD JOB MAN! That horseshoe shaped pipe you made sure outflows the factory turns to the dual pipes outback. Plus, you didn't have to spend an extra 45 bucks for a y pipe from summit or jegs.

You did it yourself and its going to improve the performance. I hoped you learned something along the way.

Please answer this - where did you get your pipe bender????

Ted
 
Well, i dont have a pipe bender, it was a pre-bent U , and the mid pipe, i i cut sections out of one to make the turns,my brother works for flowmaster welding cases so, we used a hoose clamp for a guide and a sawsall....ill get a closer pic of the bends...
 
Blk89TBSC said:
A 3" exhaust is perfect for our engines. Would we lose alittle low end? Possibly but it would be gained on the top end. Something our cars desperately need.


The point I was trying to make is that if you open your exhaust then you should increase your boost to make more power. My understanding is the boost increase is an indication of more efficient cylinder scavenging from increased turbulence and ultimately more air moved. If the exhaust is too large the exhaust air will poop out when it hits the large opening and then you'll lose the efficient scavenging. This is how I understand it to work anyhow. I do agree that a 3" center pipe is good for our cars especially if modded. Maybe a bit much for a completely stock engine though.
 
heres a close up of the bends, just tacked together for now,i figured 2.5 should be enough as i dont plan to race it out,i have a 3/4 fast freddie top and a homemade cai...i want a pulley next but only 5%, and im sure thats all i would wanna run anyways with 2.5 exhaust....not a full out race car, just a lil more efficient:)
 

Attachments

  • Photo_#17.jpg
    Photo_#17.jpg
    8.5 KB · Views: 108
...as for the y pipe, i think i will cut it in the middle and flip 'em like AnnivSpeCpe said,first time doin this stuff so good lookin out.
 
On a boosted engine scavenging isnt as much an issue..However in stock form we have so many oteh rissues to worry about then 2.5 or 3 inch exhaust:O)
 
Back
Top