m20 headers

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m20 headers

Postby 87e30 » Wed Mar 12, 2014 11:02 pm

So my entire exhaust is literally falling apart. Pieces of it fall off every few weeks, the muffler is only being held in place by a hanger, and my O2 sensor is probably the original one from 1987 and is permanently stuck in place. Obviously I need to replace everything, and I only want to do the job once. I pretty much have everything planned with the help of ideas from Yoshi's current thread.

Now I know a lot of people say until you do serious mods to an m20 you don't need to worry about the exhaust, especially headers. Well as I said I only want to do the job once, so I want some headers with bigger than stock pipes on the back. Most of the headers I see advertised say that they will slip right over (or into) your stock pipes. That's not what I want, because I want to run bigger pipe all the way so that when I DO have the engine mods (be it turbo or a strong N/A build, whatever) my exhaust will be able to keep up with all the extra air flowing through without having to spend more money replacing practically new parts.

Which brings me to this... http://www.iemotorsport.com/bmw/E30-exhaust/M20STG2.html

Now I didn't really dig deep into this yet, but from what I have seen so far these are the first set that has bigger pipe. Not sure the exact dimensions, but I'm sure I could drop them a line to find out. Has anybody had any experience with these headers? Are they worth the price tag? Is it worth the extra to have them ceramic coated, or should I just hit them with some high-temp paint? Is there something better out there for hopefully much less money? I want something that's gonna last. I bought eBay headers for my suburban (which were actually Pacesetter headers shipped straight from Summit), and they flexed so much they kept breaking the grade 8 bolts on the flanges. Obviously I don't want the same problem.


EDIT It just dawned on me 3 seconds after I hit Submit that if I were to go turbo I'm pretty sure I wouldn't be able to run these headers anyway, lol. I'm probably not going to end up putting a turbo in anyway, I'm actually gonna try to tear down my original engine and do the best N/A build I can afford and see how it turns out. 333is maybe?
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Re: m20 headers

Postby Yoshi » Wed Mar 12, 2014 11:40 pm

You want power? Headers won't really give you much for your money. A full free flowing system all said and done might net you 10whp if you're lucky and have basically no mods. IMO Just redo the exhaust with more free flowing parts minus the headers and you'll gain a good 5 whp-ish.

It's not worth $500 from a whp perspective to get those headers. But for the cost of headers, they are pretty decent.

If you want power out of the M20, boost. That's the only way.
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Re: m20 headers

Postby Nsquared97 » Thu Mar 13, 2014 7:29 am

I would love those headers just from a shiney perspective, but agreed its hard to justify them for the price. But I get what you're saying, do it once and do it right.
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Re: m20 headers

Postby blasphemy101 » Thu Mar 13, 2014 6:34 pm

I agree with those two. Without doing a full build, it doesn't seem like much additional power can be had from the M20. For what it is (single cam, designed in the late 70s, 2.5L), it's great. Unless you really want to tear into the motor or build another, I'd just refresh/maintain it, add a chip and maybe a cam, and make it sound good :)

You should probably ignore me, though, considering my only koalafications come from my budget turbo build... I kind of want to build a bitchin' N/A motor now. Paging Tony...
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Re: m20 headers

Postby 87e30 » Thu Mar 13, 2014 7:02 pm

I have the original engine that I pulled out of my car just sitting around doing nothing. My plan is to tear it down completely and upgrade everything that I can in it and put it back in. I'm looking at the 3.1l stroker kit on IE's site. It's a bit pricey, but as long as I don't screw anything up I think I will be happy with it. As I said before my entire exhaust needs to be replaced NOW, so I just want to have everything done right the first time for whenever I get around to rebuilding the other engine. So yes, I will be doing a full build. Anyone know any less expensive headers with larger than stock outputs on them? Somewhere in the 2"-2.5" inner diameter range.
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Re: m20 headers

Postby Yoshi » Thu Mar 13, 2014 7:53 pm

The issue with the M20 isn't how many liters it has (though that does hurt), it's that it doesn't breathe. The amount of work you put into that, you could have a nice S50/S52 STOCK. I have my red car sitting around with no real mods to it and it's got 250chp. You can't really get that with a 3 liter M20. Even then, you gotta tune and all that. Even turboing a factory M20 can easily net you 300whp reliably.

Why put so much work into a motor that probably still won't break 200whp?

PS: buy my S52 E30, call it a day :)
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Re: m20 headers

Postby 87e30 » Thu Mar 13, 2014 8:36 pm

Why does anyone do anything? I dunno, it seems like a fun project to work on if I ever get any spare time. Ever since I first got the car my goal was to rebuild the engine and get it running right. I have so many things that I want to do eventually. When I win the Mega Millions I will build a 50 car garage with several lifts so I can work on all of my e30's whenever I want. Until then I just wanna toy with this one. I have read of m20's getting upwards of 1000hp. No idea what kind of work it would take to get that kind of power, and I'm not expecting to be able to do it.

I know throwing a turbo on it would be much easier HP, but I live for challenges.
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Re: m20 headers

Postby M20_fever » Fri Mar 14, 2014 3:08 am

1000hp m20 is completely useless unless the car lives on a dyno. Peak power comes in around 5500rpm...Building a mean NA m20 is going to be big $$$, no way around it. You can easily spend 7-9K on a terminator m20 that will put out around 300chp. It will sound and feel mean as fuck, but will still lose to a decent turbo or SC build that cost less than half.

Those IE headers are decent, but the collector isn't designed very well, which is where headers actually make HP. There is a guy on e30tech (maybe here too I think) who's putting down 288whp on an NA m20, and a good bit comes from his custom tuned headers. If you really want some nice headers, make your own. I have a CAD file of the exhaust flange I can send you to have laser cut, then build your own. Equal length isn't the most critical design feature, how the collector comes together is more important. Do some reading on header design, you'll see the big points to pay attention to.

Honestly, your better off spending the money on head work than the header.
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Re: m20 headers

Postby Yoshi » Fri Mar 14, 2014 11:20 am

I guess it comes down to what your goals are and what your means are. If you can't cad/custom tune headers, it looks like these ones will do better than stock.

If you want to see what you can do with an M20, sure, I get it. I agree with you on this one.

To me, it's not a challenge to mess with an M20 (NA), it's a waste of money. The more I taste power, the more I realize it's a waste of time to spend it on 5hp gains here and there. My first M20 dynoed at 154whp. I did a chip/exhaust/intake and lightened the car. I made about 170whp on my best day. Still slow as balls. I put a shit turbo system in my car for $3k, made 275whp, huge smile on my face.
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Re: m20 headers

Postby 87e30 » Fri Mar 14, 2014 6:12 pm

Yeah, making my own headers definitely isn't in the cards right now. Feel free to send that CAD file though, as I may end up needing it in the future.

I don't have my mind set on those headers or anything. Was just the first set I found that ended bigger than stock pipe. I would much rather spend my money on the engine itself than headers or anything. Is there a good set around maybe the $200 price range that's bigger than stock? I think it would be a waste to use nice fat pipes for my exhaust if they won't be of any use at all. That's like a riceboy putting a coffee can on the end of the 1 inch pipe his Civic came with.
Schwarz 5-speed 87 325is (newest project)
Arktisblau 5-speed 86 325e (current DD)
Schwarz 5-speed 87 325e (parts car/LS1 swap?)
Gazellenbeige automatic 85 318i (70,000 miles)
Alpine white 5-speed 87 325is (my first e30, possibly for sale)
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Re: m20 headers

Postby 87e30 » Thu Mar 27, 2014 6:48 pm

Regardless if I get headers or not I need to replace the whole rest of the exhaust. I read the 325i has dual 1.75" pipes. Technically that will be able to flow more than a single 2.25" pipe (unless my math is wrong), but which would be better? I want to do stainless so it'll last forever, and I'm thinking a single pipe would be cheaper than 2 smaller pipes. The muffler I bought only has a single 2.25" input, which is why I was planning to use a single 2.25" pipe all the way back. Should I go with 2.5" and have it stepped down right at the muffler? Again, if my math is correct, it looks like 2.5" would flow just slightly more than dual 1.75. Ideas? Suggestions? Freebies? :-)
Schwarz 5-speed 87 325is (newest project)
Arktisblau 5-speed 86 325e (current DD)
Schwarz 5-speed 87 325e (parts car/LS1 swap?)
Gazellenbeige automatic 85 318i (70,000 miles)
Alpine white 5-speed 87 325is (my first e30, possibly for sale)
99 Suburban
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Re: m20 headers

Postby blasphemy101 » Thu Mar 27, 2014 7:23 pm

If you're looking for power, stepping down piping size may increase exhaust gas velocity, but it's a big no-no with respect to flow and maintaining exhaust pulses. It's one of the reason some straight-through mufflers are able to flow so much more than others. Even though one might be straight-through, without chambers or baffles, its internal diameter might decrease more than others. Similar issues show up when you abruptly step UP in diameter as well, but by the exhaust gas gets to the muffler, it might not matter much.

You may find a straight-through 2.25" exhaust flows better than a 2.5" that chokes down to 2.25" at the muffler, but unless you're make some serious NA power, it probably won't matter much. Stockish M20s don't seem to need much more piping diameter than they have.
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Re: m20 headers

Postby M20_fever » Thu Mar 27, 2014 10:27 pm

Unless your making big time power just go with stock design, its well designed for a stock M20.
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Re: m20 headers

Postby Nsquared97 » Thu Apr 17, 2014 7:44 am

I know this is almost 2 months later, but just stumbled across these, seems pretty damn cheap for long tube SS headers.
http://www.stegaperformance.com/store/p ... aders.html
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Re: m20 headers

Postby Yoshi » Thu Apr 17, 2014 11:03 am

link just times out for me.
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