Found my HP problem

[tpepmeie]

Originally Posted by XfireZ51

As for dynos, I week before Bowling Green, I went to Street Stuff and dyno'd the head porting and headers I did. 385rwhp. In BG both Don and I put ours on and I dyno'd 370rwhp.

Hmmm. that's interesting. Have you had it on any other dynojet? I was wondering if Street Stuff was a little optimistic, but don't have any data to support that at all.

Todd

[Kb7tif]

Originally Posted by Ccmano

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

Did you dyno the car before any mods, what were the numbers

[LGAFF]

Both Don and Hans had about 330-335hp....with porting they went to 360 for Don and about 370 for Hans.

[Ccmano]

Met with Paul today and picked up the Mflow. Nice piece and brand new! Thanks again Paul. The 2" stuff is coming out asap. I have to take a look at it and may do it myself or at the very least will have Al do it. I'm not sure I want go back to Twisted Pipes after seeing this. If I can get all the pieces together I may take Wednesday off and to this.

So... the new system will be 3" coming out of the cats into a 3" X-pipe, into the 3" Mflow resonator, into the 2.5" Corsa Mufflers. Should be interesting.

H

[XfireZ51]

Originally Posted by tpepmeie

Hmmm. that's interesting. Have you had it on any other dynojet? I was wondering if Street Stuff was a little optimistic, but don't have any data to support that at all.

Todd

Todd,

Before their closing, Street Stuff was the dyno regularly used by Marc Haibeck, and Pete.
Also my intent was to demonstrate discrepancies in dynos even tho both the BG and SS dynos
are Dynojets. In the end, the purpose of the dyno is to give you a view of relative changes after having established a benchmark.
Finally, if we use the results I got at BG and compared that to Han's results they're nearly identical. My results at SS and BG were with the B&B system.

[bobbyhi]

What does Marc use for dyno now??

[Pete]

I always go to 2 differant shops with DynoJets.
Street Stuff and Speed Inc. dyno's were within 5rwhp,same week.

I also go to 2-3 different tracks to back up the Dyno #'s.

Also have videos for those from Missouri

Pete

[lbszr]

Originally Posted by tpepmeie

Hmmm. that's interesting. Have you had it on any other dynojet? I was wondering if Street Stuff was a little optimistic, but don't have any data to support that at all.

Todd

I was thinking BG's was pretty close one and two years ago with both times seeing several newer vettes and zo6's with no mods putting out in the ballpark with what they are advertised of doing. At the time with cams set to 93-95 specs and header, B@B, MH chip, it did 360 and one year ago it did 395 with upper port, secondaries removed and B@B resonator traded for magnaflow bullets with H pipe. Didn't make it this year though I've never heard how often the dyno's get calibrated

[XfireZ51]

Originally Posted by lbszr

I was thinking BG's was pretty close one and two years ago with both times seeing several newer vettes and zo6's with no mods putting out in the ballpark with what they are advertised of doing. At the time with cams set to 93-95 specs and header, B@B, MH chip, it did 360 and one year ago it did 395 with upper port, secondaries removed and B@B resonator traded for magnaflow bullets with H pipe. Didn't make it this year though I've never heard how often the dyno's get calibrated

lb,

There were 4 of us there that night. 90, 91(karterdon's), 92 (mine), and a 93. The dyno operator told us they had nicknamed it "heartbreaker" because it was not as "optimistic" as some others. Each of us, with the exception of karterdon and his 91, had previously dyno'd our cars and in each case we observed that the resulting numbers that evening were between 15-20rwhp down from our previous runs. This was all SAE corrected.

[tf95ZR1]

Originally Posted by LGAFF

I would say the 2" stuff needs to go before going to any dyno, think tf95ZR1 could chime in, I can't recall what he picked up when he dumped the Borla resonator but if I recall over 15hp...and it necks to about 2.25"

As scientific as I could make it: In the AM I had my car dynoed with "A" resonator. Took the car to a muffler guy I know who replaced the resonator
with an "X" pipe. Took it back to the same dyno same day and got the results Lee stated.

I kept the same mufflers because I like the sound.
More resonance ~1800 RPM but tolerable and worth it to me. JMO