Resonators?

[bpracer]

I really just want to get rid of the restriction at the stock X-pipe and weld it back up at the resonator. As shown in the pictures above, the tubing restriction is down less than 2.5" in places. All that mess, and the x-pipe shape doesn't look like it helps at all.

I'm staring at the FP 2015 GT x-pipe replacement. It says it 2.75" pipe, and it must neck down to 2.5 in at the front.

I'm think it might be possible to cut off the 3" long necked down portion, essentially move the x-pipe up a little and then re-weld the joint at the resonator. If I wanted to return it to stock, I could probably do it without much noticeable difference except the welding might look neater.

The spacing of the pipe might be off, but my welder can probably deal with it.

That, or I'm going to be the strange person that buys the Borla ATAK and then adds resonators...

 

[VoodooBoss]

@bpracer you're probably on the right path to extract a few more HP. Unless you have sound restrictions at your local tracks I'd dump the resonators as well. It's louder but more important to me is the snap crackle pop you get which I like. They rob a few HP as well.

 

[bpracer]

It looks like the one vendor that described the normal GT X-pipe from FP quoted 2.75" diameter, but I think its a mistake and only 2.5". Borla had an X-pipe for a Vette that showed up as 2.75" but that ended up being the expanded ends to slip over 2.5" pipe. So nothing that I can find relatively cheap can be re-purposed.

So, the only off the shelf replacement is the GT350 specific 3" Corsa double helix X-pipe and at $500+ it is a bit spendy.

 

[VoodooBoss]

Good luck on your search, keep us posted on what you find.

 

[bpracer]

cj350 really helped this idea along with the pictures. Many thanks for looking into this.

Finally got home from traveling on business and measured some stuff myself. The nominal diameter of the system is 2.5" OD until behind the resonators. At that point the 2.5" pipe feeds into a section of 2.75" pipe that the ID is scrunched down to the OD of the 2.5". Then it is 2.75" from there on.

I'm going to buy the '15 FP X-Pipe and hopefully adapt it. The Roush and the FP pieces look ok, most others have one drawback or another. I can get a deal on the FP piece so that's what I'm going to try.

At what I'll call the collector portion of the FP GT part, the first few inches in length of x-pipe is scrunched down, but the rest is 2.5". I'll cut off the reduced section and with any luck that will fit the GT350 collector spacing. (other x-pipe designs may not have enough section length to do this) The spacing between the two pipes is of course the unknown compared to the GT350. Then I plan to weld the rear section to where the 2.75" pipe necks down as it comes forward. The exact point depends on the actual length of the part. 32" seems to be the answer but I don't know exactly how much of the front section will be cut-off. I can basically save the front half of the OE exhaust if I want to return it to stock appearance.

If the car is too loud for my tastes or track limits, I can add some aftermarket resonators. Or, add the ability to bolt in/out the resonator section.

The main goal is to get rid of the funky restrictions noted in the previous photos and maybe have a better flowing X cross-section.

This may take a couple week after I get the piece as I'm not home more than half the time... ugh.

 

[VoodooBoss]

Are you planning to dyno your car before and after your x pipe mod?

 

[bpracer]

Are you planning to dyno your car before and after your x pipe mod?

Kind of doubt it. It may depend on my work schedule and who might do the work.

If I can test fit this a bit before it's permanent and it looks like it will work, I might try.

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[bpracer]

I got the normal 15+ x-pipe today. and it will take modification for it to work. The rear section spacing looks the same and is long enough to reach beyond the resonators. I don't think that will be any problem.

The front section is 3/4" too narrow. I think it could be modified fairly easily. The Vorshlag guys are close and just sent them some details of what I want. I have somebody else that can do it but they are recuperating from some eye surgery, so welding is a little iffy right now. It will probably be a couple weeks until I can get this done. Track day this Saturday, then work travel for the next two weeks.

 

[bpracer]

Two other GT350s at the track day I instructed at and they sure seemed quiet on they outside vs inside.

I cut the front section off the replacement x-pipe. There are some dimples where the tube bender formed the X in the area that would be sealed by the front band clamp. I did work some of that out but since the section may need to be modified for spacing, I'm thinking I'll just buy a 45 degree bend to cut in two to serve that purpose.

Still two weeks out before this/ can happen. Talked to the fabricator that made the stainless exhaust for my former racecar and he didn't think it was a very big deal.

I sure wish I could TIG weld...

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[bpracer]

Two other GT350s at the track day I instructed at and they sure seemed quiet on they outside vs inside.

I cut the front section off the replacement x-pipe. There are some dimples where the tube bender formed the X in the area that would be sealed by the front band clamp. I did work some of that out but since the section may need to be modified for spacing, I'm thinking I'll just buy a 45 degree bend to cut in two to serve that purpose.

Still two weeks out before this/ can happen. Talked to the fabricator that made the stainless exhaust for my former racecar and he didn't think it was a very big deal.

I sure wish I could TIG weld...

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So there is the plan, two sections of 403 18 degree mandrel bends (they're one gauge thicker) from Columbia Mandrel Bending, that will be used to widen the front of the x-pipe.

The bends should really be 22.5, but close enough. I could have added a section in middle of the front X, but I think this will seal better. The thicker wall tubing won't hurt in that regard either.

I decided I want to be able to remove the back part of the exhaust, hence the v-band clamps. It will all be removable and seal well. If it needs to be quieter, I can make another x-pipe with resonators or modify this one.

I'm hoping I can have this welded up this coming week.

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[VoodooBoss]

Two other GT350s at the track day I instructed at and they sure seemed quiet on they outside vs inside.

Did they have the resonators removed?

 

[bpracer]

Did they have the resonators removed?

No, they were stock, non-Rs. The cars just didn't seem that loud in comparison to what it sounds like in the car.

My previous racecar required ear plugs with a helmet as it had 3" x-pipe, side exit exhaust just barely muffled. Old school 289 cid@+7500 rpm yessir! I had to shove some baffles in the side exit outlets so I could warm the engine without rattling my neighbors dishes.

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[bpracer]

No, they were stock, non-Rs. The cars just didn't seem that loud in comparison to what it sounds like in the car.

My previous racecar required ear plugs with a helmet as it had 3" x-pipe, side exit exhaust just barely muffled. Old school 289 cid@+7500 rpm yessir! I had to shove some baffles in the side exit outlets so I could warm the engine without rattling my neighbors dishes.

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So Gas Monkey Garage was booked so had to take the car to Fired Up!

Wandered down to Sue's place next door to talk about putting green suede on my seats but she was all "why you always bring me junk?"

So...the shop that really did my exhaust is about 200 yards from all that stuff...

After all the purchasing of extra pipe to make the front X legs wider, it wasn't needed:

The front just slipped in, the header down pipes actually looked more parallel to the frame rails with the narrower X. (This was after I already cut off the 2.25" section for the stock GT 5.0 exhaust, see previous post)

Not widening the front like I planned moves the X a little further forward so you probably want to check the spacing of the legs at the back as the flare apart slightly.

Welding the v band clamp on the X was easy but they had trouble TIG welding the rings on the original exhaust side due to lack of clearance to work under the car.

If you just wanted to weld it all in place, cutting at the rear weld of the resonators allows you to remove the 2.5" pipe segment that was slipped in the the rear 2.75" section. You could probably slip the new X in place.

Be careful you line up the rear tail pipes in the outlets before you weld it up. The weight of the mufflers wants to rotate them. With the v band clamps you can just loosen, rotate, and retighten.

It's louder of course. Seems less "blatty", maybe a little smoother sound, but haven't gone for a real ride yet. Traffic was too much on the way home.

Leaving now for a real test.

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[bpracer]

Put the heat shield on in the exact same place so the x pipe really didn't change position as I thought. The shield gets bent a little bit around the diameter of the v band clamp. I'd like to rotate the clamp a bit more but don't want any sharp end pointed towards the gas tank.

 

[VoodooBoss]

Looks good. Did you get the sound you were hoping for?

 

[bpracer]

Looks good. Did you get the sound you were hoping for?

I live in suburbia and still couldn't really try it out. Not much more snap, crackle and pop as I was thinking there would be, but the jury is still out. I'm wondering if the actual x-pipe design contributes to that characteristic. The stock one is more like two exhaust streams crossing each other, while this one and the FP/Borla exhaust is more like sharing most of the area of the two pipes.

I can't help to think that this change is a large percentage of any benefit the FP full exhaust.

Discounting the extra mandrel bends I purchased and didn't use, I'm in to this for about $400.

 

[bpracer]

I live in suburbia and still couldn't really try it out. Not much more snap, crackle and pop as I was thinking there would be, but the jury is still out. I'm wondering if the actual x-pipe design contributes to that characteristic. The stock one is more like two exhaust streams crossing each other, while this one and the FP/Borla exhaust is more like sharing most of the area of the two pipes.

I can't help to think that this change is a large percentage of any benefit the FP full exhaust.

Discounting the extra mandrel bends I purchased and didn't use, I'm in to this for about $400.

It is loud, maybe louder than the cars with the stock x pipe. I do like the sound though. Can't wait to really test at full song on the track. None around here have sound limits so no real worry there.

I can't say I see much benefit in a new, full exhaust unless you were doing headers. Then, this would be too loud.

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[Etchhead]

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