Found my HP problem - ZR-1 Net Registry Forums

Ccmano · 07-11-2009

After doing all the usual upgrades on my engine, Ported top end, chip, SW headers, modified corsa, new injectors, HO coils etc. I had the car dyno'd a couple weeks ago and was somewhat disappointed the get HP/Torque readings of 369/370. While the torque reading is good, the HP output is about 20 lower than expected. While there are alot of variables I suspected I knew what the problem was.

After all the mods were done I felt the Corsa system was too loud for my taste. I had a local exhaust shop swap out the corsa resonator for an X-pipe and a magnaflow resonator. I loved the sound and was happy till the dyno run. I finally jacked the car up and crawled under to take a look at their work today. What I didn't realize is that for some reason the shop used 2" pipe between the x-pipe and the resonator and between the resonator and the connection to the 2.5" Muffler pipes. This meant I had a system with a 3" header collector into 3" HF Cats into a 2.5" x-pipe into 2" pipe into a 2.5" resonator into 2" pipe into 2.5" mufflers. Not condusive to good flow.

It just goes to show you if you want things done right you have to do them yourself and inspect the work others do for you before you accept it.

The resonator and 2" pipes will have to come out. Since the corsa system is a 2.5" system I will leave the 2.5" x-pipe. I'm thinking of using a Borla resonator. The Corsa resonator is nothing more than straight pipe with an expansion chamber. It looks like the Magnaflow resonator that was used has pipe spacing that is too far apart. I need a resonator with a bit more muffling ability than the Corsa and that aligns correctly with the pipes. Given that I want it quieter I will have to give up some HP. But 20 is more than I am willing to give.

Other than the Borla resonator any thoughts on what to use in there?

H

07-11-2009	#1
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Found my HP problem After doing all the usual upgrades on my engine, Ported top end, chip, SW headers, modified corsa, new injectors, HO coils etc. I had the car dyno'd a couple weeks ago and was somewhat disappointed the get HP/Torque readings of 369/370. While the torque reading is good, the HP output is about 20 lower than expected. While there are alot of variables I suspected I knew what the problem was. After all the mods were done I felt the Corsa system was too loud for my taste. I had a local exhaust shop swap out the corsa resonator for an X-pipe and a magnaflow resonator. I loved the sound and was happy till the dyno run. I finally jacked the car up and crawled under to take a look at their work today. What I didn't realize is that for some reason the shop used 2" pipe between the x-pipe and the resonator and between the resonator and the connection to the 2.5" Muffler pipes. This meant I had a system with a 3" header collector into 3" HF Cats into a 2.5" x-pipe into 2" pipe into a 2.5" resonator into 2" pipe into 2.5" mufflers. Not condusive to good flow. It just goes to show you if you want things done right you have to do them yourself and inspect the work others do for you before you accept it. The resonator and 2" pipes will have to come out. Since the corsa system is a 2.5" system I will leave the 2.5" x-pipe. I'm thinking of using a Borla resonator. The Corsa resonator is nothing more than straight pipe with an expansion chamber. It looks like the Magnaflow resonator that was used has pipe spacing that is too far apart. I need a resonator with a bit more muffling ability than the Corsa and that aligns correctly with the pipes. Given that I want it quieter I will have to give up some HP. But 20 is more than I am willing to give. Other than the Borla resonator any thoughts on what to use in there? H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold. Last edited by Ccmano; 07-11-2009 at 06:34 PM.