4-1 or 4-2-1 exhaust headers?

[Medusa]

I'm looking to improve the low end torque in my MR2, and I've always heard that 4-2-1 headers are better for low end power, as opposed to 4-1 headers which I've heard shift the powerband somewhat higher.

The only 4-2-1 headers I've found so far are the Weapon R headers, but I don't know if they're a rip off or actually worth the money...one thing I noticed is that the headers designed for the Scion tC look like they *might* fit, does anybody else agree?

Link: Weapon*R Racing Development

Pic:

I know the page says "optimized for high RPM" yada yada yada, but I don't really listen to the advertisments too much, I try to find people with actual experience.

Also, I'm not too concerned with modding farther down the exhaust, as long as the headers fit down to underneath the engine I can cut and weld in custom tubing from there. Basically, if it fits till the final 2-1 reduction, it will work fine for me.

So basically I'm trying to make sure the price isn't a rip off and it will fit to my specifications (above).

[mr2stealth]

i would love to put a header on my car, and run a completly new exhaust. but its quite expensive, especially while going to college

[M.Bailey]

well from what expierience i have had the 4 to 2 to 1 (also called a tri "y" header) do improve low end torque you are moving in the right direction. but as far as the 4 into 1 shifting the power band i would say you were wrong, shifting the power band has to do with the primary tube size (if you dont knwo that is, its the tube ID on the header) so if you are looking for low end torque a tri "Y" would be great, and i dont know but Doug Thorly headers might have a tri "Y" for your MR2 and that it a good header they have good welds and thick flanges so it will seal. i wish you luck in your quest.

[Medusa]

So smaller primaries will improve low-end torque, right?

What size should I shoot for that will be small enough to give good torque at lower RPM but wide enough to not cause uneccessary exhaust backpressure?

I could have sworn I saw something about primaries somewhere...but I couldn't find the thread. Anybody know what I'm talking about?

[TomsMR2]

theres no 4-2-1 headers available anyway, so it really doesnt matter much..

4-2-1 headers are better though.. but again, irrelevant.

those headers are for a tc.. a mr2 isnt a tc.. they dont even use similar engines.

[MR2 Drifter]

I also read something about this, the wrong size will end up making you lose power instead of gaining, I plan on getting some headers also and this could help me out too.



^There are 4-2-1 headers for MR2s, there's a ebay brand (cheap) and then I forgot what company makes em but there like $300

[M.Bailey]

yes a smaller primary would would improve torque but I'm not sure how small or how big you can go. if it was me (assuming you can cut and weld) i would find out what the primary size is on the best MR2 header go get some mild steel tubing and build your own tri "y". you dont even need a tube bender just buy a few 90 degreee angles in the same tubing and just cut out what angle you need. were there is a will there is a way. good luck to you once again

[Medusa]

Actually, the engine in the tC is the AZ series, which replaced the S series. I don't know if the port dimensions are the same or not, but I could machine a new flange for it. I've got good fab skills, and the access to all the machines I would need, including all welding.

I just want something more lightweight than mild steel, I dunno what kind of thin wall tubing I could find that is easily weldable and bendable, and still lightweight.

[albertgunit101]

eBay Motors: OBX Exhaust Header 91-95 Toyota MR2 Non-Turbo Header (item 140267453809 end time Sep-22-08 10:56:26 PDT)

this is still a 4-1 design but its long tube style though and can improve hp. i think

[M.Bailey]

in any header the key to making power is long primarys that are the same length. since you dont waqnt to se mild steel yo could go with a lower grade of stainless and use a super thin tube like 411 stainess. i dont know if you could or would want to use chrome moly tubing its light but expensive and it must be madrel bent in order to not wrinkle it.if it was me i wouldnt care about the extra 2 ppounds thin wall mild steel was going weigh. but either way you go i would recomend tig welding. easier to control heat and keep from your weld making a ridge on the inside of the tube.

[Medusa]

^^ Thanks, I'm not really familiar with all the different alloys.

I had thought about chromoly, but yeah it's crazy expensive for just headers application, I don't need that much strength, just as long as the engine vibrations don't rip it apart it should be good.

Yeah, tig welding is what I thought too. Tig or mig, either one will work it just depends on what machine I have access to easiest.

[mr2stealth]

oh medusa can you fabricate a new exhaust system for my mr2?!! haha

[Medusa]

Well, given materials and equipment I could help out! I actually don't have much experience working with any pipe, and the majority of my welding has been stick welding. I tried mig once or twice, and never used tig. But I would get somebody who's done custom exhaust before if you want something that looks professional.

[mr2stealth]

haha understandable! Ill probably just go get a new exhaust tomorrow after i pick up my car! yay!

[Medusa]

Cool!

I have good fab skills, I just haven't specifically worked with any tubing very much. But I'm really good at that kind of stuff, I'm looking forward to making my own headers.

[TomsMR2]

i have a very nice, 90% perfect 4-2-1 custom header based off a 3sge unit. it makes tons of midrange.

ill sell it if you want it. it has no lower flange at all, so you'd have to weld a b-pipe to it.. but still, the hard part is done already.

[Medusa]

^ PM'd

[Servin]

Tom you didnt happen to buy that off a celica forum did you?

[TomsMR2]

no, i bought it off tred and made it myself.

[thornz12]

never heard of anyone ever using a weapon r, im gonna be running a SSAUTOCHROME header with my NATKO exhaust