Found my HP problem

[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
:cheers:

[LGAFF]

You should through the exhaust from my 92 on it while its off the car and head to the dyno:mrgreen:

I would call Mike at twisted....he used 3' stainless on my car and I am sure he would change it....is the 2" what the kit came with?

[LGAFF]

http://i134.photobucket.com/albums/q115/lgaff/DSC02353.jpg

Only bad thing about the Borla is its 2.25 neck down as it enters the resonator

[rhipsher]

I'm doing all of the same mods you did right now. I don't want to set myself up for dissapointment by having expectations of big dyno #'s. I've got a Borla exhaust system right now and like the sound of it. It may not be the best exhuast performance wise but after top end porting and Jeal headers and tuning we will see. I have no idea what to expect from it all. I just hope it puts a smile on my face.

[Paul Workman]

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

H
:cheers:

Wow! Talk about restriction and all manner of reflections! Sheesh! But, I'm glad to hear ya found it.

As for noise, I have a Borla resonator, if you want to try it.

I just finished hanging my 3" system under my Z today. It still needs some regulating to get it all aligned right. Soon as I can arrange it, I'm also going to add the "Power Stick" 18" mufflers in place of a resonator (behind the SW crossover), and then going thru the Maganaflow twin tube mufflers. It will be a true 3" all the way to the muffler inlet that does shrink down to 2.5. But, I don't think a restriction that far back is going to result in much loss. Certainly it is better than the obstruction in the B&B mufflers.

I don't mind a little noise, but don't want to have to shout to carry on a conversation while in cruise mode.

I'll let y'all know how it works out.

P.

[-=Jeff=-]

Only bad thing about the Borla is its 2.25 neck down as it enters the resonator

Actually... it necks down worse then that

I would say buy the X pipe resonator form Paul.. it is the magnaflow set up.. that would be better

[xlr8nflorida]

You should be at 450 or 400 RWHP with your setup.

The exhaust is hurting some but not that bad. I have borla on my car and I'm probably leaving 10HP on the table over a B&B system. Mine sounds alittle throaty but more like a sleeper - I prefer that over a bunch of resonance.

[tomtom72]

Hans, is the top end P & P including head porting and re-degreeing of the cams?

I'm asking as your dyno numbers are exactly like a 90 that I inquired about. He had a P&P to the plenum and I/H's and a chip and headers w/o cats. The P&P and chip was mail order from Mr. Haibeck's shop and the owner did his own assembly work. His heads & cams were not touched, and his dyno sheets which he posted in his add were right at a 365 hp avg for three runs. I don't remember the brand of headers and the exhaust....:redface:...it was a long time ago.

:cheers:
Tom

[Paul Workman]

Hans, is the top end P & P including head porting and re-degreeing of the cams?

I'm asking as your dyno numbers are exactly like a 90 that I inquired about. He had a P&P to the plenum and I/H's and a chip and headers w/o cats. The P&P and chip was mail order from Mr. Haibeck's shop and the owner did his own assembly work. His heads & cams were not touched, and his dyno sheets which he posted in his add were right at a 365 hp avg for three runs. I don't remember the brand of headers and the exhaust....:redface:...it was a long time ago.

:cheers:
Tom

365 at the wheels???:jawdrop: Somethin' ain't right!! Mine dyno'ed last fall at 339 stock (except for a Borla cat-back). I don't know what it is at now - soon to find out - but w/ top end porting and Marc H's chip, and not changing the stock exhaust, turned my 90 into a whole new animal! I would think it should be between 390 and 400...NOT 365, if the dyno graphs posted on Marc's wall are any indication.

[tomtom72]

Yea, Paul. The other thing that I don't recall for sure was the brand of dyno....I think it was Dyno-Jet?

But it's what this 90's numbers were. This was when I was looking for a Z to buy, I was a noob so I knew very little about any of the finer points on our cars. This guy was generous in that he took the time to give me some heads up on what I should be buying in a used Z.

:cheers:
Tom

[Ccmano]

Thanks for the input guys. As we know not all dynos are equal or accurate for that mater. I suspect this one was not real accurate. In this case, same day same dyno, karterdon put down 358/349 on his 91'. He has similar mods but no headers and is using a full Corsa cat back. So this gives me a point of reference. I have headers and the modded Corsa, but only 10 more HP?

As for my mods, I do not have any head work other than port matching the IH's and the cams have not been timed. Based on several other cars I've seen numbers on, with the same mods, I should be in the 385 to 395HP area.

Paul can you give me the dimensions of that magnaflow resonator you have? Length, width, height and most importantly what is the center to center distance of the piping going in and out. Thanks

H
:cheers:

[LGAFF]

Check this site for options:

http://www.magnaflow.com/02product/universalsatins.asp?shape=oval

[LGAFF]

Wonder if this glasspack resonator might work: http://www.classicchambered.com/classic/products.html

[Ccmano]

Paul,

Is that Magnflow resonator out of a Kit or is it just a standard Magnaflow part?

H
:cheers:

[-=Jeff=-]

Paul,

Is that Magnflow resonator out of a Kit or is it just a standard Magnaflow part?

H
:cheers:

his is the one out of the LT4 kit.. Same center section Dominic has on his car

:thumbsup:

[Paul Workman]

Sorry it took so long to get back, but "duty called", and I had to go in to start one of the crews this morning. (Y'all sleep in WAAAAAY to late anyway!!:mrgreen:)

But, Jeff is right: It is part of an LT4 kit. I kept the mufflers (installed yesterday), but I was looking to "go for performance" first, and then back off (if necessary) for ride comfort. (Right now it has the SWs w/ 3" outlets to a SW X (more like a "merge") pipe to Magnaflow links and mufflers. I need the assistance of someone that can cut and weld stainless tubing so as to install my "Power Stick" "resonators"...Al? Whatcha doin' buddy???.)

P.

[XfireZ51]

Hans,

If you do decide to try the MFlow system, I'd suggest going to Twisted Pipes. It will take a little work to match the header collector to the
X-pipe, particularly on the passenger side, as there was a slight offset with the Watsons I have.
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. SO to your point re: dynos.
My first suggestion would be to dyno the car as is at a known shop and scan it to eliminate other factors being the culprit for your power loss.
We could even look at tuning it to see if output could be optimized.
Then I'd look at addressing the exhaust if it still isn't performing to expectations. My $.02 :hello:

[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"

[XfireZ51]

I would say the 2" stuff needs to go before going to any dyno, think 95ZR1 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"


I would disagree because I believe you would want to establish a benchmark you can measure against as needed. The one in Antioch
wouldn't be something I would depend on replicating. I'm not disagreeing that the exhaust could represent a restriction, but is it the only thing? Is it responsible for 15-20rwhp? I don't think any of us knows that at this point.

[rhipsher]

Personally from my own experiance going from the Borla resonater to straight 2.5 dia pipes in place of it I didn't notice any difference at all in power. At least nothing I could physically feel. Of course I still had the Borla mufflers on it. There was no resonence running with straight pipes. But the exhuast tone sounded like crap and I couldn't wait to put the Borla res back on. Maybe and X pipe would have made a difference. I don't know.

[tpepmeie]

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]

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
:cheers:

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
:cheers:

[XfireZ51]

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??:dontknow:

[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]

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:dontknow:

[XfireZ51]

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:dontknow:

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]

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

[lbszr]

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.

That sounds good to me to think it has 415 instead of 395:thumbsup:

[XfireZ51]

That sounds good to me to think it has 415 instead of 395:thumbsup:

That's really my point. You need to pick a benchmark and stick with it to measure any changes. You can make the number almost anything you want depending on actual v sae v standard correction.
A wise old tuner told me to use the trap speed. That's the real measure but again on a relative basis.

[Ccmano]

OK.... :icon_scra Who's the snitch????

Got a call today from Mike at Twisted Pipes. Said, "someone" emailed him a cut-&-paste of my comments on this forum...

I have to say he was very nice and was concerned that I thought there was a problem with his work. I told him that after 9 months I did not expect him to do anything. He insisted that I bring it back and he would make it right. You don't see that very much these days! When I told him that I was going with the Mflow set up he said to bring it along and he would take care of it.

I should have the rest of the pieces I ordered from Jegs in the next few days. SS Pipe, new header reducers and clamps.

I may just take it back to him and see what happens.

Now...will this be clipped and sent as well?
H
:cheers:

[LGAFF]

Hans,

That would be me, I felt responsible as I sent people to Mike after using him several times ...I did edit the comment to only the info about the set up and any personal references were cut out......

I did not want him to call you, just told him that I felt responsible.

Sorry if I caused an issue.

[-=Jeff=-]

hans,

you mean it is not done yet??

LOL

[LGAFF]

Hans, this is what I sent Mike.....

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.

No reference to a post, told him you sent me a note.

[XfireZ51]

Hans,

Mike put my MFlow system on. I can only say that in my case he took over 3 hrs to put it together properly. Mine doesn't gave any of the issues you showed in your pics. I also don't have the cats.

[Ccmano]

No worries... guys.

Thought that might have been you Lee.;)

I actually thought it was good of him to call in the way that he did. I just have to decide if I want him to install the Mflow stuff. This time I think I'll stay and watch him as he does it.

H
:cheers:

[Kb7tif]

Hans, this is what I sent Mike.....

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.

No reference to a post, told him you sent me a note.

That sounds like a ^%$#house install to me. Good name for the place. Find another shop.

[lbszr]

That's really my point. You need to pick a benchmark and stick with it to measure any changes. You can make the number almost anything you want depending on actual v sae v standard correction.
A wise old tuner told me to use the trap speed. That's the real measure but again on a relative basis.

I agree totally, that's why BG is the only one I've had mine on for comparison after porting.

[Ccmano]

Went back to Twisted Pipes today. Mike was very pleasant and willing to accomodate me. They immedeately put my car on the lift and we took a look. Long story short they installed the Mflow resonator/xpipe, had to fabricate the head pipes to connect to headers and fabricate a connection to the corsa mufflers. I supplied the reducers, connectors and clamps. So now it's 3" all the way from the header collectors to the Corsa's. Stood there and watched the whole thing. It came out very nice. They only charged me 2 hours labor, it took 3.5 hrs with 2 guys working and me supervising.

Interestingly I noted that the Mflow resonator actually has an x-pipe inside it, in addition to the x-pipe fitted on the inlet side. Strange that they would set it up this way.

In driving the car afterwards, Surprisingly I noticed that it's now somewhat quieter. No resonance what so ever. I have to say I really like the combination of Mflow x-pipe/resonator and Corsa mufflers. Problem of course is you only get these Mflow and Corsa parts as part of full systems. Really can't say I felt any more power at this point.

Next comes the Dyno. We'll see if this change made any difference at all. Third times a charm, as they say.
H
:cheers:

[XfireZ51]

Hans,

Are you sure that the MFlow mufflers are not available separately When I spoke with Mike last year, he told me the full system I bought was made up of components he could buy individually. In fact, I had contemplated using the MFlow Xpipe and resonator but with the B&B mufflers. As for the rsonator, I could swear that when we looked at mine before installing that
it was straight thru. But sometimes the mind plays tricks. :confused:

[Paul Workman]

Went back to Twisted Pipes today. Mike was very pleasant and willing to accomodate me. They immedeately put my car on the lift and we took a look. Long story short they installed the Mflow resonator/xpipe, had to fabricate the head pipes to connect to headers and fabricate a connection to the corsa mufflers. I supplied the reducers, connectors and clamps. So now it's 3" all the way from the header collectors to the Corsa's. Stood there and watched the whole thing. It came out very nice. They only charged me 2 hours labor, it took 3.5 hrs with 2 guys working and me supervising.

Interestingly I noted that the Mflow resonator actually has an x-pipe inside it, in addition to the x-pipe fitted on the inlet side. Strange that they would set it up this way.

In driving the car afterwards, Surprisingly I noticed that it's now somewhat quieter. No resonance what so ever. I have to say I really like the combination of Mflow x-pipe/resonator and Corsa mufflers. Problem of course is you only get these Mflow and Corsa parts as part of full systems. Really can't say I felt any more power at this point.

Next comes the Dyno. We'll see if this change made any difference at all. Third times a charm, as they say.
H
:cheers:

:thumbsup:

Let's hope the dyno likes it too! Getting rid of the 2" choke points certainly didn't hurt performance, I'm sure.

Looking forward to the next FBI track day!

P.

P.

[Ccmano]

Dom,

I can not say for sure you can't get the resonator separately however, I've been all through the Mflow catalog and there are no mufflers with as long and narrow a case as this and with the pipe centerline spacing as close with 3" inlet/outlets.

As for the internal x-pipe I saw that for myself. One of the installers commented on it as well. I suspect the double x-pipe combination is engineered that way for a reason, probably to control the resonance.

H
:cheers:

[XfireZ51]

Hans,

As for the performance of this system and the restrictions notwithstanding,
Lgaff and I have very nearly the same setup. Both 92s with ported top end and 63mm throttle bodies. We also both have the same Watson 1 7/8" headers. Lee has an Xpipe with no resonator and Borla mufflers. I have the full MFlow system with resonator.
Lee has 4.10s to my 3.45s and a Fidanza. When he and ran heads up the last time, our trap speeds were virtually identical, 116.47 v 116.48. Just gives you an anecdotal benchmark as best as I can describe.

[Pete]

Guys here is what i remember.

Me and Al used to run 116-117 MPH with only exhust & chip.
No port work
With plenum/IH porting we were running 119-120.

So my opinion, you guys are looking for cake and eat it too.

The LT5 likes to breathe.

Heck even GM knows you can't have your cake and eat it,have you guys heard the LS7 at WOT crappy/loud from outside the car.

Also if GM went with full 3" exhaust with flappers for 500 HP why would you guys go with 2.5" and down to 2 1/4" (Corsa Tailpipe) :dontknow:

Think of this for a minute if your exhaust is restricted porting the heads won't be worth it you'll go from 116 to maybe 118. or from 370 rwhp to 390-400rwhp that tells me your exhaust is robbing you of 25-40rwhp.

Anyway food for thought.
Pete

[XfireZ51]

Pete

Nobody doubts either the experience you or Al have had with the LT-5 and what makes it work. Marc H. has said several times that he has seen virtually little to no difference between a 3" exhaust and a 2.5" Corsa regarding hp.
I would also think engine displacement would have something to do with the necessary size of the exhaust. By any chance, had you timed the cams when you ran 116-117 with just chip and exhaust?
At least from the dyno runs Lee and myself have done, we are in the 385-390hp range with top end porting and that's before recognizing that the Street Stuff WB may have been reading lean.
Here's a very interesting thread with excellent information:
http://www.digitalcorvettes.com/forums/showthread.php?t=94275&highlight=exhaust

[Pete]

Pete
By any chance, had you timed the cams when you ran 116-117 with just chip and exhaust?


Plenum had not even come off at that time.

Al, found 19rwhp from B&B rasonator to SW X-pipe.

Pete