Headers vs downpipes

[Owwdee8s]

I am looking to either install the bad boy jhm headers or high flow catless down pipes. What are tge pros and cons of each and how much more power do you get with the headers compared to down pipes

[JimmyBones]

Headers require an engine pull or lowering the engine really far. So you will spend major bucks and there is a long lead time to make the headers. With headers you will really notice a lot more torque. Look through JHM's videos because they ran a 12.70 second quarter mile with headers and a lot of other goodies.

Catless down pipes can be found real easy, even slightly used for cheap. You can install the down pipes with the engine in the car but you don't get the same amount of gain power wise.

[Dudeman258]

Just so you know, a rise in torque is required for any gain in horsepower under the same rpm range. Torque is proportional to HP. I have seen allot of torque comments on this forum that worry me.

The headers should (hopefully they got close) properly tune the exhaust diameter and primary lengths to provide peak torque at a usable RPM. This in turn will allow for absolute maximum peak horsepower with the current intake and cylinder head. Most manufacturers will not release specific design information behind their parts either because they don't understand and copied/guessed or they want to keep what is a highly guarded secret..intake/exhaust tuning. Therefore I cannot give you my true opinion other then I have seen promising dyno plots, and 1/4mile times. I have questioned JHM on the design and they were professional in their response, it appears their engineer(s) are not clueless compared to many companies (good thing ;)).

The downpipes will reduce the back-pressure caused by the cat converters (flow restriction), which in turn allows the engine to "breath" better, however my educated guess is the OEM header design is lacking in every way (diameter and primary length) meaning you will get very poor scavenging effects and your mass airflow will be limited through the engine overall. Disclaimer: I do not know the oem ID and length so my comments are purely speculatory as I have done no calculations.

Conclusion:
There is no reason not to get headers but for money.

Let me know if you have any questions.

Walker

Edit: Someone is selling JHM headers in the classified section btw.

[BCsniper]

Edit: Someone is selling JHM headers in the classified section btw.

This! Get em while its hot boys

[tylerS]

the jhm treatment, headers included, completely change this car. i ran catless FI downpipes prior to the headers and there is a VERY noticeable difference.

[noznab]

Just so you know, a rise in torque is required for any gain in horsepower under the same rpm range. Torque is proportional to HP. I have seen allot of torque comments on this forum that worry me.

The headers should (hopefully they got close) properly tune the exhaust diameter and primary lengths to provide peak torque at a usable RPM. This in turn will allow for absolute maximum peak horsepower with the current intake and cylinder head. Most manufacturers will not release specific design information behind their parts either because they don't understand and copied/guessed or they want to keep what is a highly guarded secret..intake/exhaust tuning. Therefore I cannot give you my true opinion other then I have seen promising dyno plots, and 1/4mile times. I have questioned JHM on the design and they were professional in their response, it appears their engineer(s) are not clueless compared to many companies (good thing ;)).

The downpipes will reduce the back-pressure caused by the cat converters (flow restriction), which in turn allows the engine to "breath" better, however my educated guess is the OEM header design is lacking in every way (diameter and primary length) meaning you will get very poor scavenging effects and your mass airflow will be limited through the engine overall. Disclaimer: I do not know the oem ID and length so my comments are purely speculatory as I have done no calculations.

Conclusion:
There is no reason not to get headers but for money.

Let me know if you have any questions.

Walker

Edit: Someone is selling JHM headers in the classified section btw.

It's refreshing to hear that there are actually ppl on this forum who understand the engineering that goes into making a set of headers. It seems as though the majority believe all that matters is having equal runner length. The JHM headers take into account shot gun firing order, exhaust diameter, etc. I think the biggest thing that scares ppl away from headers is the motor pull but TBH its something that can be done in a weekend with a couple buddies. Lately I've been seeing threads about shops quoting "lol" worthy prices just to install downpipes or a catback. I think I'd have a brain aneurysm if I dared price out a header install.