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Unread 01-01-2015, 09:48 AM   #1
ianthart89
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Budget Friendly Exhaust System Modification Questions.

I am on a tight budget and I am considering an upgrade to my 1998 Jeep Cherokee Limited 4.0L I6's exhaust system. Would the aFe Mach Force XP 409SS 2.5" Catback Exhaust be a good choice for me. The one I am looking at includes the aFe 1.5" Stainless Steel Headers. Any thoughts on the system, or recommendations on other budget friendly systems?


Last edited by ianthart89; 01-01-2015 at 10:29 AM..
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Unread 01-01-2015, 10:10 AM   #2
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Discussing the removal of cat convertors is against forum rules, so you may want to edit your post. Personally, I'd leave it on anyway since it won't hurt performance. I don't know much about the AFE exhaust. Is the rest of it stainless or just the header? The Dynomax cat-back is pretty cheap and sounds decent. I'd also go with the Dorman exhaust manifold. Its cheap and has the flex joints built in to eliminate the original problem that cracks the manifold. I don't know anyone running the AFE manifold, but I do know of a few running other expensive headers which ended up cracking since they didn't have the flex joints.
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Unread 01-01-2015, 10:34 AM   #3
ianthart89
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Originally Posted by jeepkid03 View Post
Discussing the removal of cat convertors is against forum rules, so you may want to edit your post. Personally, I'd leave it on anyway since it won't hurt performance. I don't know much about the AFE exhaust. Is the rest of it stainless or just the header? The Dynomax cat-back is pretty cheap and sounds decent. I'd also go with the Dorman exhaust manifold. Its cheap and has the flex joints built in to eliminate the original problem that cracks the manifold. I don't know anyone running the AFE manifold, but I do know of a few running other expensive headers which ended up cracking since they didn't have the flex joints.
Any suggestions for a budget friendly catalytic converter then? The one on my Jeep is trashed and has a rattle. And thanks for the suggestion for exhaust system. I will take it into consideration for my budget.
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Unread 01-01-2015, 10:36 AM   #4
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Wait for Dynomax to have one of their $75 rebates (pretty common). That will make a Dynomax cat-back the single best bang-for-buck you can find. Unless you have a relatively powerful stroker, 2.25" exhaust remains ideal for you.

APN headers are popular for those on a budget.
Dorman's OEM replacement header is better than the factory header (for durability purposes only) and very affordable.

Most headers crack on the XJ. Replacing motor/trans mounts, making sure all exhaust hangers are solid/secure, and installing a flex joint after the header or downpipe will all help tremendously.

Performance-curve.com is a great source for quality, affordable cats, and after you sell your old cat for scrap (they're worth a solid amount in scrap $), a new cat really isn't expensive at all.
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Unread 01-01-2015, 01:09 PM   #5
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X2 on Performance Curve. Cheap cats, and much smaller than the factory rock catcher cat.
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Unread 01-01-2015, 01:19 PM   #6
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Originally Posted by mschi772 View Post
Wait for Dynomax to have one of their $75 rebates (pretty common). That will make a Dynomax cat-back the single best bang-for-buck you can find. Unless you have a relatively powerful stroker, 2.25" exhaust remains ideal for you.

APN headers are popular for those on a budget.
Dorman's OEM replacement header is better than the factory header (for durability purposes only) and very affordable.

Most headers crack on the XJ. Replacing motor/trans mounts, making sure all exhaust hangers are solid/secure, and installing a flex joint after the header or downpipe will all help tremendously.

Performance-curve.com is a great source for quality, affordable cats, and after you sell your old cat for scrap (they're worth a solid amount in scrap $), a new cat really isn't expensive at all.
Dorman headers or Dorman exhaust manifold? I am looking for boost in fuel economy and my understanding is that headers win over a manifold.
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Unread 01-01-2015, 02:00 PM   #7
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Any suggestions for a quality and budget friendly head pipe? I am looking to replace the whole exhaust system.
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Unread 01-01-2015, 04:11 PM   #8
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Quote:
Originally Posted by ianthart89 View Post
Dorman headers or Dorman exhaust manifold? I am looking for boost in fuel economy and my understanding is that headers win over a manifold.
They're the same thing in this case. Technically the XJ never used a manifold; "header" is the appropriate name even for the factory part. Headers are a tricky situation with XJ's since nobody makes a "perfect" header for us. Even the best choices aren't going to give you any kind of impressive gains, so decide what you really want. If you're trying to be "budget friendly" pinching pennies and MPG is your main area of concern, worry about something other than the header since it won't be able to help you much anyway--grab a Dorman and save your money.

Quote:
Originally Posted by ianthart89 View Post
Any suggestions for a quality and budget friendly head pipe? I am looking to replace the whole exhaust system.
The downpipe? Many exhaust shops could fab one pretty easily. I know Rockauto also sells one for $45.


Make your own decisions based on what you research using Google (this stuff has been covered tons of times), but if I were you, I'd replace my motor mounts and exhaust hangers as necessary first then buy a Dorman, a downpipe locally or from Rockauto, a flex pipe, a cat from Performance Curve, and a Dynomax cat-back preferably during a rebate time (but still well-priced without rebate).
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Unread 01-01-2015, 04:23 PM   #9
ianthart89
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Originally Posted by mschi772 View Post
They're the same thing in this case. Technically the XJ never used a manifold; "header" is the appropriate name even for the factory part. Headers are a tricky situation with XJ's since nobody makes a "perfect" header for us. Even the best choices aren't going to give you any kind of impressive gains, so decide what you really want. If you're pinching pennies and MPG is your main area of concern, worry about something other than the header since it won't be able to help you much anyway--grab a Dorman and save your money.
I will go with a Dorman headers, a Magnaflow 2.25/2.5 Catalytic Converter and a Gibson 2.5 Catback System. Any suggestions for a better head pipe.

I am also upgrading to BOSCH 4 Port Fuel Injectors.
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Unread 01-01-2015, 04:56 PM   #10
mschi772
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Quote:
Originally Posted by ianthart89 View Post
I will go with a Dorman headers, a Magnaflow 2.25/2.5 Catalytic Converter and a Gibson 2.5 Catback System. Any suggestions for a better head pipe.

I am also upgrading to BOSCH 4 Port Fuel Injectors.
Better how? The only thing one really could ask for that any ol' replacement might not have is mandrel bends, and that would be strange to demand when the rest of the system isn't built in such a way for them to really matter. No, no suggestions for a better downpipe as it is my opinion that there is no such thing in this situation.

I strongly discourage the Gibson cat-back. It's more than twice as expensive as a Dynomax cat-back and offers you nothing for that extra money. The mandrel bends are meaningless given your setup, and the 2.5" pipe will rob you of power where it matters. Magnaflow is a fine cat, but is almost certainly more expensive than a number of options provided by Performance Curve with nothing really warranting the extra cost besides their name.
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Unread 01-01-2015, 05:02 PM   #11
ianthart89
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Quote:
Originally Posted by mschi772 View Post
Better how? The only thing one really could ask for that any ol' replacement might not have is mandrel bends, and that would be strange to demand when the rest of the system isn't built in such a way for them to really matter. No, no suggestions for a better downpipe as it is my opinion that there is no such thing in this situation.

I strongly discourage the Gibson cat-back. It's more than twice as expensive as a Dynomax cat-back and offers you nothing for that extra money. The mandrel bends are meaningless given your setup, and the 2.5" pipe will rob you of power where it matters.
So stick with the 2.25 System, and just replace the down pipe? I have limited car knowledge, but I thought that reducing the back pressure with a larger pipe increases power and performance.
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Unread 01-01-2015, 05:12 PM   #12
mschi772
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Quote:
Originally Posted by ianthart89 View Post
So stick with the 2.25 System, and just replace the down pipe? I have limited car knowledge, but I thought that reducing the back pressure with a larger pipe increases power and performance.
Lots of people throw the "backpressure" word around not really knowing what they're talking about, but use of that term is often very convincing to those with even less experience.

This has more to do with exhaust gas velocity, but the bottom line is that unless you've got a suped-up stroker, the consequences of a 2.5" exhaust are reduced power in the lower RPM's where your engine operates most of the time and a slight increase in power in relatively high RPM's rarely seen by a Jeep 4.0. The difference isn't huge, and 2.5" won't be the end of the world by any means, but 2.25" is ideal and isn't any harder or more expensive to do.

P.S. I'm talking about tailpipe size. Factory configuration is 2.5" from the header to the cat and 2.25" after the cat, and this works-out very well because exhaust starts-out hotter and less dense. As it travels and cools, it gets denser which is why the exhaust shrinks from 2.5 to 2.25 in order to maintain good velocity.
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Unread 01-01-2015, 05:20 PM   #13
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If you want a really slick system that will compliment a non-boosted, non-stroked 4.0 that isn't exactly budget friendly coming in probably in the $600-800 ballpark if not more...
  • Borla (if you're really willing to risk head cracking; Brown Dog motor mounts might provide extra piece of mind) or Thorley header
  • Mandrel bent downpipe (Borla includes this)
  • Flex pipe section somewhere between header and cat
  • Spun cat from Performance Curve
  • Cat-back with mandrel bends (Flowmaster, Dynomax, Magnaflow, AP, Borla....all performance mufflers are pretty equal behind the 4.0; no need to split hairs here)
  • Stainless steel parts preferred when possible for longevity

All that doesn't really shine unless you invest money into the other areas of your engine, however, which is why it's not actually my recommendation for someone who's working on a budget.



Quote:
Originally Posted by mschi772 View Post
then buy a Dorman, a downpipe locally or from Rockauto, a flex pipe, a cat from Performance Curve, and a Dynomax cat-back preferably during a rebate time (but still well-priced without rebate).
This entire setup could be purchased for roughly $300-400 and will provide most of the benefits of a system costing 2x as much. That Gibson cat-back you mentioned earlier costs nearly this much all by itself which is why I jumped to steer you away from it.
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