chengteik

After researching all the past threads on this forum (especially our exhaust guru pzull's threads), I've decided to copy the custom design that pzull came up with.

Parts needed to build Pzull’s custom exhaust system (pzull I hope you don't mind me posting this):

Parts needed:
1x 32” equal length headers from the racers group mild steel version with ceramic heat coating inside and outside or T304. Headers 1.75" OD (not sure if correct? pzull?) and primaries 32" long.

2x Magnaflow Muffler #14236 2.5” inlet/outlet

Question: Are 2.5” or 2.75” mandrell bends better for this design?

2x mandrell magnaflow U-bends #10706
4x mandrell magnaflow 90-bends #10716 (2 for connecting to header and 2 for tips)

Fabrication:

1) Fabricate the X-pipe using two mandrell U-bends. Important to ensure left and right U-bends are cut at centerline when joined otherwise internals will have a ridge which will cause turbulence. One end of X-pipe to mufflers and the other end of u-bends are joined to the 90 degree mandrell bends to attach to the headers.

2) Use the 90 degree mandrell bend or use the other pipe end of the primary muffler as the bend and weld it to the muffler so that the exit fits the bumper exhaust cutout and weld on the exhaust tip - there's not alot of space so the tip has to be quite short

3) the muffler can be held in place with the stock bracket.

Hope I got this right. The 32" length primaries on the headers are supposed to be optimized for 6000rpms so will be quite at crusing speeds but wicked at high rmps.

AsianBond

Email me and I'll send you pic and video of my custom exhaust made in HK, cau@matrixcap.net

JW in Texas

I did a modified version of PZULL's exhaust on the race car & it worked great! Definitely helped the midrange over previous B&B muffler. I kept the B&B long tube headers, came off those into (2) shorty glasspacks going towards the center of the car, into a mandrel bent crossover & back out to the exhaust outlets with tips. I'm very happy & the crossover tuning point does make a difference.

chengteik

Jay, did you use 2.5" or 2.75" mandrell bends?

JW in Texas

It's been a while but I believe we used 2.5".

chengteik

OK, after further research and using the custom header design software found at www.headerdesign.com, I have come up with the following specs for the headers:

Primary Pipe Inside Diameter 1.50in.
Primary Pipe Length 33.1in.
Collector Inside Diameter 2.36in.
Collector Length 13.1in.

I'm gonna get intouch with the racers group to see if this is doable.

pzull

chengteik, don't use 2.75' they are too big and you will lose low end torque. on headerdesign.com you will find other pages to help you calculate size of tailpipes, etc.

for pipe sizes make sure you specify OD or ID (ie. outside or inside diameter) the program gives you inside diameter but pipe dealer specify OD not ID so you must work backwards based on the thickness/guage of your steel pipe.

The racers group header will not make collector length of 13" possible as the flange (merge) is too far forward. the old B&B long headers extends more to the rear and would give you nearer spec collector length but they are not equal length (racers group's headers are near equal length - 4 equal, 2 not so exactly equal)

JW, did the cross over raise the pitch of your exhaust note? You would get better results if the crossover was done before going into the glasspacks. You want the crossover tuning point to have strong sound waves for stronger tuning - going through the glasspack 1st might weaken the sound wave hence weaker tuning. Effective difference - dunno, could be miniscule difference, but just a thought

JW in Texas

I believe it did. It really Sounds great now on the high end. Thanks for the idea!

chengteik

Thanks guys. Will go with the 2.5". I've sent an email to The Racers Group with a difficult request. 32" primaries equal length with the flange set further towards the back so that collector length is closer to 13".

BTW The Racers Group say they outsource the manufacture of their custom headers cause they don't have the jigs to do them. I'll see what they come back with.

pzull

cheng, that's a true custom one which will cost quite a bit. My custom was a semi custom. I asked them to use one of their stock base model headers, cut the primaries just before the merge and add 5 inches of striaght to the primaries and reweld the merge cone. I ended up with just over 30" cos they added 6-7 inches instead which was just fine. I think they charged me the same price as stock ie. no extra charge.

Beware the mild steel with ceramic coating. Mine was starting to show signs of corrosion coming through. Stainless would be better but twice the cost without coating

JW in Texas

That is exactly why I went with the B&Bs. I hate their mufflers but the headers aren't bad. They may not be exactly equal length but I picked up the set for the RSA on ebay for $ 700.00 & they are stainless. I've got less than a grand in the whole exhaust inc. fabrication costs & the chrome tips. Hey, I'm cheap, what can I say

chengteik

OK, if I go with SS headers. Ceramic coatings - worth doing? Outside only or inside as well. I heard that coating the inside causes some turbulence? True or not?

chengteik

Hey Pzull, any idea if the custom exhaust shops in Singapore (eg Man Exhaust) can fabricate custom headers? Would be much cheaper here if possible. But do they have the tooling and skills?

pzull

cheng, if you have SS, you can skip ceramic coating if you want.
Man can do custom headers but he won't as it is too tim econsuming without the payback. Besides he doesn't have the facility to do mandrell bends. Headers are not easy to get right without first building a jig, which is only worthwhile if one was going to fabricate in large quantities