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Old 04-15-2012, 03:26 PM
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Exhaust size??

Now that I have gotten totally confused (and cross eyed) researching exhaust sizes and mufflers. I have a 1985 Jag. XJS with a 350 chev. quadrajet on a performer intake, and rams horn exhaust manifolds, dumped into 1 5/8" exhausts. I would like to open them up to 2" or 2 1/4 (if they will fit) but I don't want to loose any low end torque as I 'd like to autocross some. I also would like to open up the mufflers I but don't want to hear anything except a mild deep purr unless I step on it. Any suggestions on pipe size and mufflers (they are behind the axle). I would greatly appreciate any help you can give me.

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Old 04-15-2012, 03:34 PM
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I wouldn't hesitate to run 2" exhaust off a standard ram horn and 2.5" exhaust off a corvette-style ram horn manifold. Cross the pipes off the manifolds together with an "H" or "X" connection and then run dual Turbo-style mufflers of the largest case size you can fit under the jag. If anything you'll likely gain power and torque and it wont be obnoxious at idle.
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Old 04-15-2012, 03:55 PM
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Step up to 2.25" or 2.5", don't worry about the x or h pipe unless sound is a concern, it does help sound but that's about it.

Id also look into possibly upgrading your manifolds even cheap 1.5" long tubes would help.
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Old 04-15-2012, 05:07 PM
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Also if you have the room a nice 3 inch single exhaust will match the flow of dual 2 1/2 twice pipes, and a good flowing turbo style muffler like a dynomax ultraflow or Magnaflow and give good torque , but if you do go duals, make sure you use a x over between the banks.
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Old 04-15-2012, 06:32 PM
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Quote:
Originally Posted by Jim Rockford
Also if you have the room a nice 3 inch single exhaust will match the flow of dual 2 1/2 twice pipes, and a good flowing turbo style muffler like a dynomax ultraflow or Magnaflow and give good torque , but if you do go duals, make sure you use a x over between the banks.
A single 3" would be adequate for this engine, provided you don't need the "dual exhaust" hype.

Those manifolds are killing you though.
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Old 04-15-2012, 07:43 PM
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Sorry, but I like the hype (and it's for show), what is the difference between corvette and regular ram horn ? Besides I've had the manifolds ceramic coated and the headers (that I know of) won't clear the rack. Will the H (no room for the X) really help the torque or just the sound. Clearance (and the installer) dictates 2, maybe 2 1/4 max. best muffler? Thanks Rick
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Old 04-15-2012, 08:08 PM
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Quote:
Originally Posted by Kenrick Binegar
Sorry, but I like the hype (and it's for show), what is the difference between corvette and regular ram horn ? Besides I've had the manifolds ceramic coated and the headers (that I know of) won't clear the rack. Will the H (no room for the X) really help the torque or just the sound. Clearance (and the installer) dictates 2, maybe 2 1/4 max. best muffler? Thanks Rick

It won't affect tq at all, just sound. Magnaflow makes good mufflers. Corvetter ramhorns are larger diameter.
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Old 04-16-2012, 10:57 AM
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Quote:
Originally Posted by Kenrick Binegar
Now that I have gotten totally confused (and cross eyed) researching exhaust sizes and mufflers. I have a 1985 Jag. XJS with a 350 chev. quadrajet on a performer intake, and rams horn exhaust manifolds, dumped into 1 5/8" exhausts. I would like to open them up to 2" or 2 1/4 (if they will fit) but I don't want to loose any low end torque as I 'd like to autocross some. I also would like to open up the mufflers I but don't want to hear anything except a mild deep purr unless I step on it. Any suggestions on pipe size and mufflers (they are behind the axle). I would greatly appreciate any help you can give me.
You need to run 2-1/2 inch pipes minimum from the rams horns to the mufflers. The amount of restriction to flow between 2.25 and 2.5 inch is a very surprising 33% give a take a couple percent. This is especially important at the muffler. Walker Dyno Max 2-1/2 inch in and out will provide about the best flow 375 CFM against the least sound. The pipes and mufflers being too large, with-in reason, is less harmful to the bottom end than too small is to top end power.

The purpose of X and H pipes is to allow sharing of muffler and or catalytic converter capacity where dual exhausts are used, while at least the H pipe seems to have some effect upon lowering the dBs of the exhaust the real purpose is that most exhaust systems don't come close to the volumes per unit of time that the intake system is capable of. So to reideratee the connection between the pipes allows some share of the gas volume by both sides. The X crossover is better at this capacity sharing than the H but tends to make more noise doing it.

Since you're running rams horns there is no need to configure things for tuning the pipes as done with long tube headers. Your only need with this set up is to minimize back pressure which the engine has to use power to overcome.

Bogie
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Old 04-16-2012, 11:47 AM
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plus unless your installer is using mandrel bent pipe the bends are gonna crush the 2 inch pipe down to as low as 1 7/8th cross area , so go the biggest you can fit and as said before best muffler s are magnaflows or Dynomax Ultrafows , Avoid any flowcrappers as they don't flow nearly as well due to the barn doors place in the middle of the airflow.
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Old 04-16-2012, 02:47 PM
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Quote:
Originally Posted by Kenrick Binegar
Now that I have gotten totally confused (and cross eyed) researching exhaust sizes and mufflers. I have a 1985 Jag. XJS with a 350 chev. quadrajet on a performer intake, and rams horn exhaust manifolds, dumped into 1 5/8" exhausts. I would like to open them up to 2" or 2 1/4 (if they will fit) but I don't want to loose any low end torque as I 'd like to autocross some. I also would like to open up the mufflers I but don't want to hear anything except a mild deep purr unless I step on it. Any suggestions on pipe size and mufflers (they are behind the axle). I would greatly appreciate any help you can give me.
[/QUOTE]
plus unless your installer is using mandrel bent pipe the bends are gonna crush the 2 inch pipe down to as low as 1 7/8th cross area , so go the biggest you can fit and as said before best muffler s are magnaflows or Dynomax Ultrafows , Avoid any flowcrappers as they don't flow nearly as well due to the barn doors place in the middle of the airflow..[/QUOTE]


Yeah a big X2 on Mr Rockford's. You want full diameter mandrel bends, none of this crushed bend or corrugated bend stuff and no flex tube. All this stuff eats up a lot of CFM capacity.

Be careful of joints, you always want the fit where slip joints are used to be the pipe ending toward the rear (of the vehicle) to be the male side of the connection and the pipe facing forward to be the female. Reversing this eats into the flow numbers really big time.

Bogie
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Old 04-16-2012, 05:29 PM
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Well my muffler man is not going to like to hear what I'm going to tell him (for that matter neither is my wallet I'll bet) Now that I've spent all day listening to muffler sound comparisons I think that I've decided to go with Magnaflow even though Flowmaster is made in the U.S. and I would rather buy it. It just does not have the rich deep sound I need. (I don't like that tinny/high pitched sound). It just dosen't sound correct that .25" is 33% (plus or minus?) more efficient. Well thanks you guys you have just helped make an old man's day. Until the next time don't forget to keep the dirty side down. Rick
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Old 04-16-2012, 07:13 PM
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Quote:
Originally Posted by Kenrick Binegar
Well my muffler man is not going to like to hear what I'm going to tell him (for that matter neither is my wallet I'll bet) Now that I've spent all day listening to muffler sound comparisons I think that I've decided to go with Magnaflow even though Flowmaster is made in the U.S. and I would rather buy it. It just does not have the rich deep sound I need. (I don't like that tinny/high pitched sound). It just dosen't sound correct that .25" is 33% (plus or minus?) more efficient. Well thanks you guys you have just helped make an old man's day. Until the next time don't forget to keep the dirty side down. Rick
(.25" is 33%) Yes we've tested it 6 ways from Sunday and Dave Vizard did it on Sunday. We're not talking about just the pipes, but that alone is a 19% difference in area, but what also comes to play is the bend radius which is a function of pipe diameter larger diameter pipe requiring a larger radius bend and mufflers sized to the flow of the inlet and outlet pipes make a big difference, here alone is a 42% difference for an identical high flowing muffler between 2.25 and 2.50 inlets and outlets. Put it together as a system and you're see numbers running 27 to 34 percent.

It was suggested that you run a single 3 inch pipe which isn't a bad solution either, but has two problems one is simply space for that size especially if you're trying to snake past the rear axle to some under the bumper exit location, the other is getting a muffler with flow capability to match the pipe size and will fit under the car. If you were running headers with collectors 3 inch pipe might be a problem you'd have to deal with, but your not.

I ran a single 3 inch on my parts truck for a number of years it ended just ahead of the left rear tire, even with a big Walker muffler on it the noise in cab was deafening. I converted it to 2-1/2 duals with Thrush glass packs about 6 years ago that dump out under the tailgate valance, a lot quieter in the cab. The dumping under the rear most end of the vehicle also pretty much assures you that it's emptying into a low pressure area; as there is always a vacuum following a moving vehicle that gets both physically larger and depresses the pressure inside the vacuum bubble deeper the faster you go. So this makes up for some of the losses in the twists and turns of the plumbing to get there. Where-as, if you dump anywhere else you need a wind tunnel test just to see that you're not trying to exit in a place of higher than atmospheric pressure.

I have less concern about 2.25 inch pipes if they occur after the mufflers and are neither very long nor twisty. A reasoning though, untested by me experimentally, is that mufflers in the act of removing noise energy also reduce gas temperature. That means for a given size pipe there is less gas density thus less volume which leads to a velocity loss and a pressure gain. So pulling the pipe size down after a cooling event will increase the velocity and lower the pressure as a result. Strictly for a street engine, don't try this on your race car. But you have to remember that if you need to make a turn, the smaller tube will most likely be bent around a smaller radius and when that happens the gas flow becomes restricted very fast. Vizard has even argued for a larger diameter pipe, smoothly transitioned, when having to pass objects like rear axles and suspension. Like my ending under the rear valance, I'm suspicious of my own logic let alone his. In my playing with gas flow on the bench; one thing I constantly find is that the flow has to be managed (shape and confinement) when it's allowed to go freely into more space than is needed it often doesn't find the most efficient path on its own.

Certainly if you're exhaust guy has enough flexibility in his tube shaping machine, he can diddle the bend radius such that a 2.25 inch pipe has a more open turn. But your still up against the flow issues of smaller inlet/outlet mufflers, if you do that for the entire system. Transitions in tube diameters are best done with cones over a few inches. Abrupt changes really disturb (lesson) flow.

Bogie
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Old 04-17-2012, 02:32 PM
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Bogie, I didn't mean to question your findings. You sound more than a little knowledgeable about flow dynamics. I am glad to hear that Dave checked it on Sunday. LOL However you did bring up some interesting facts which I didn't know and will consider. Thanks for the info. Rick
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Old 04-18-2012, 06:45 AM
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Don't forget they make oval exhaust tubing also. Might help with the 3 inch single option.
http://www.spintechmufflers.com/tubi...ng/cat_41.html
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