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DIY 280Z mandrel bent side exit exhaust with 3" dump

Exhaust cutout H-pipe dual exhaust custom tip

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#1 Smyrna388Z

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Posted 09 January 2016 - 07:23 PM

In order to reduce weight, add simplicity, and improve exhaust performance, I decided to tackle an exhaust system myself. I've always paid to have a crush tube system installed and have never been particularly happy with the ones I've had. They have been functional, but I suspect restrictive.
To build what I have so far, I purchased two 2 1/2" mandrel 180 degree J-bends and a stick of 3" tubing from Summit Racing. Tubing cuts have been made with a miter saw with cutoff wheel, sawzall, and hole saw.
I will add a 3" dump where you see the hole in the H pipe.
Prior to the Magnaflow mufflers, including the H pipe will all be 3" pipe.
Time consuming but fairly simple to this point. I recommend anyone giving it a shot. Satisfaction of building your own exhaust will be worth it.
I am running the 3" dump to the rear. I added to pictures to show the custom oval tip as I align it for welding.
Picture after final welds is attached. System is ready for install. Once I get the headers installed, I can fabricate the header collector to H-pipe tubes.

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Edited by Smyrna388Z, 23 January 2016 - 08:58 AM.


#2 Smyrna388Z

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Posted 10 January 2016 - 08:58 AM

General location of the 3" exhaust cutout
This could easily run to the back of the car and exit in the original location. I will install it as if it is going to exit in the rear (future addition).

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#3 RebekahsZ

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Posted 11 January 2016 - 04:04 PM

Very cool!  Must be nice to have all that room inside a 280z tunnel.

 

Couple questions?

1) Stainless or aluminized?

2) Are you going under the rocker panel or are you cutting a hole thru it to put the pipes thru?

3) Have you heard a date for ZAttack2016?  That will be my deadline to have my car back on 4 wheels.  I dunno if it will be aligned and drag-ready....

 

Keith


Edited by RebekahsZ, 11 January 2016 - 04:04 PM.

1972 240z, purchased in 1991 for $900. Bone stock LS2/T56/DBW from 2006 GTO, swap completed in 2011. 400rwhp/435 rwtq. 2400# minus driver. JCI swap, Mantic ER2 clutch kit, JTR headers, single exhaust, Borla muffler, MGW shifter, M2 Differentials shortened Z31 CV axles, Z31 CLSD R200, Chequered Flag Racing billet stubs and companion flanges. MSD 2-step, Hurst roll control, both operated from switches on clutch pedal. 9" Hoosier drag slicks on Weld Draglites, 245/45/16 Hoosier A6/R6 on 16X8+10 Rota RBR. 225/250 sectioned coilovers, Koni 8610-1437RACE shocks, DP and EMI camber plates, MM shortened rear control arms, TTT front control arms, poly and aluminum bushings. Top speeds: Ohio Mile 174mph, C/GMS class record holder, best 1/8 mile 6.96 at 100mph, best 1/4-mile 11.0 at 126mph, best 60' 1.43, best 1/2-mile 148mph at GA 1/2-mile. Home Track-Jake's Dragway, Moulton, AL. SCCA autocross club - TVR, Huntsville, AL. Lets race!


#4 Smyrna388Z

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Posted 11 January 2016 - 06:23 PM

Aluminized
Under the rocker panel. Ground clearance will not be an issue with 2 1/2" pipes. I welded the pipes with them touching the rocker panel bottom flange, then trimmed the flange for clearance.
I will email tomorrow and try to get a ZAttack date.
I have to get this exhaust done, the new AFR heads on, and the headers installed before the weather warms up and the race tracks open.
More pictures of progress.
I have decided to run the 3" exhaust dump out the back.
Custom tip and mandrel bent 3" tubing.

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Edited by Smyrna388Z, 16 January 2016 - 07:33 PM.


#5 Smyrna388Z

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Posted 18 January 2016 - 07:11 AM

Update: exhaust tubing is in place. Next step is to drop the exhaust and weld it up.

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Edited by Smyrna388Z, 18 January 2016 - 07:13 AM.


#6 Smyrna388Z

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Posted 24 January 2016 - 05:58 AM

Weight went out the door for a reason for the new exhaust, but it is still lighter than the 2 1/2 duals all the way out the back. The dual out the back system had two Magnaflow mufflers (pictured) + two Cherry Bombs at the tips - great sound but a bit too restrictive for the new power levels. The side exhaust is complete and now waiting on the headers to make the last two tubes.

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Edited by Smyrna388Z, 24 January 2016 - 05:59 AM.


#7 LanceVance

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Posted 24 January 2016 - 07:44 AM

So exhaust can exit via the side pipes whether the cutout is open or closed? Why bother with a cutout in this case?

I've got a cutout on the STi, and can tell you from experience that running full open is not ideal for the anything but the track or hooning around backroads. Avoiding dirty looks at stoplights, every Honda thinking you want to race, and the unwanted attention of the law is the whole point of being able to redirect into a quiet stock style system right?

All I'm seeing is that you expect the exhaust to make two rapid 90° turns when the cutout is open, instead of the less restrictive, shorter and straightforward path via the sidepipes.

Not trying to knock your efforts, the exhaust looks great from a craftsmanship point of view, but I don't think you'll be getting the full benefit of the cutout in your current configuration. Realistically, to get the full range of control, you'll need a dual cutout setup with two Y pipes feeding the central (full to the back) dump.
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1973 Datsun 240z - Running tripples, getting the L28ET!
1975 Datsun 620 Pickup - Future SR20/Ratrod project

#8 Smyrna388Z

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Posted 24 January 2016 - 08:04 AM

LanceVance, the side exhaust pipes are 2 1/2" pipes and I know they will not have quite enough CFM to support my HP goals. Just need a bit more for 500hp.
Beyond the header 3" collectors and the 3" H-pipe the goal is simply to have enough CFM. The flow direction (90 degree turns in the H-pipe) will not be a concern. Similar to a chambered muffler. The thought is to open the cutout valve at the race track to supplement the side exhaust CFM and keep it closed on the street for a tamer tone.
Alternate reasons are to fill the exhaust body cut in the rear with a tip, more noise when I want, uniqueness in sound and layout.
I'll be able to make passes down the drag strip with the 3" pipe open or closed. It may or may not benefit. I'll post the results on this thread.
I appreciate the feedback. Not sure how it will work myself, but I think it will be cool. Thanks.

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Edited by Smyrna388Z, 24 January 2016 - 12:53 PM.


#9 Smyrna388Z

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Posted 31 January 2016 - 04:30 PM

You can see in this picture where the exhaust will exit on the sides.

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Edited by Smyrna388Z, 31 January 2016 - 04:31 PM.


#10 Smyrna388Z

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Posted 25 March 2016 - 07:45 PM

Update: Sanderson C33-AP, 1-3/4" primary, long tube headers fit great on a 280Z.
I installed the headers today. Be prepared for variances in the manufacturing process. I had to clearance my oil pan a bit on the driver's side with a hammer. I bent the passenger side tubes in to the engine about 1/8" to gain clearance at the frame rail in the engine bay and the fuel lines that run alongside the frame rail under the body. This may not be necessary if your set is manufactured with slightly more bend in the tubes.
Very happy with the fit. It is as if the headers were made for a 1976 Datsun 280Z with a Chevrolet LT1 350 and 700r4 transmission.

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Edited by Smyrna388Z, 25 March 2016 - 07:49 PM.


#11 Smyrna388Z

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Posted 26 March 2016 - 07:45 PM

Today I got all of the exhaust pipes in place and tacked. I have more ground clearance now than I had with the old crush tube 2-1/2" system I removed.
Long tube headers and 3" exhaust is possible on a 280Z.

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Edited by Smyrna388Z, 26 March 2016 - 07:46 PM.


#12 Smyrna388Z

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Posted 18 April 2016 - 06:41 PM

The Sanderson long tube 1-3/4" headers are installed along with a single 3" non-muffled pipe to the rear. This pipe can be sealed by means of an exhaust cutout valve. The exhaust would then flow through 3" collectors, pipe, and H-pipe to two side pipes muffled by two 2-1/2" Magnaflow mufflers.
I painted the pipe black and therefore it is hard to see. But notice how well 3" pipe can fit under a 280Z.Attached File  image.jpeg   56.22KB   0 downloadsAttached File  image.jpeg   90.02KB   0 downloadsAttached File  image.jpeg   68.92KB   0 downloadsAttached File  image.jpeg   78.46KB   0 downloadsAttached File  image.jpeg   72.8KB   0 downloadsAttached File  image.jpeg   64.68KB   0 downloadsAttached File  image.jpeg   89.91KB   0 downloadsAttached File  image.jpeg   86.69KB   0 downloads
I am very happy with the figment of the Sanderson headers in this engine swap. I did pull the passenger side header toward the passenger side while heating the pipes to gain more clearance along the frame rail. I suspect this was due to jig figment at the manufacturer because they left more room than what was needed between the header and oil pan on that side.

#13 Smyrna388Z

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Posted 12 May 2016 - 05:08 PM

Exhaust complete
The attached video clip is with rear exit cutout closed and with rear exit cutout open.
The long tube headers were a challenge, but so far happy with the results. I did raise the front end 1/2" to increase ground clearance.

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Edited by Smyrna388Z, 12 May 2016 - 05:26 PM.


#14 Smyrna388Z

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Posted 06 September 2016 - 03:01 AM

Update:
Rear exit open; improves 1/8 mile ET by about .04 seconds and sounds very cool. Exhaust is working well. Recommend doing your next exhaust yourself!





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