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Exhaust requirements for higher output engine?

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Hi,

 

If going with 9.5:1 CR pistons and a 292 cam, is it essential that the exhaust manifold be upgraded to a tii unit (or header) or will the non-tii manifold from a '73 or '74 be adequate?

 

Thanks.

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Define: essential. It really depends upon your goals. 

 

You might leave a few HP on the table at higher revs but probably not enough to notice in normal everyday driving through the seat of your pants.  I would spend my money elsewhere until you find a natural reason to replace your exhaust. 

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I would not say it's essential. The stock manifolds and exhaust systems have proven to be very good.  Many (many) years ago we tested a stock system against 4 aftermarket systems (Abarth, Ansa, Supersprint, Monza)  on a stock Tii with the stock exhaust manifold and down pipe. there was a difference of less than 3 HP at the wheels across all of them with the stock system being #2 and the quietest of them.  The Monza made the most power and was loudest. 

 

A 9.5:1 CR and 292 cam is not a huge jump in performance (you didn't say what intake you are using) but unless this is a car that is going to spend a lot of time at the track above 5000 rpm the stock manifold and exhaust should work very well. If you want more noise then that is a different discussion.  If you don't have a Tii manifold you can remove the air injector nozzles and do a bit of porting of the stock smog manifold and virtually match the Tii manifold. 

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Agreed 100%- with the caveat that if your exhaust after the 2-1 collector's not stock,

it might be SMALLER than stock, and that's not good.  Stock's about the minimum.  No surprise, eh?

 

t

 

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(edited)

I ran a stock Genuine tii exhaust system on my last hotrod (S14 crank, 2.2l, dumb 304 camshaft and dumb 45 DCOE Webers....yadda yadda....you know the drill) and NEVER felt like the exhaust was holding the car back. The stock stuff fits, lasts virtually forever, and is very well designed. After playing with many MANY systems over the years, I finally got fed up with screwing with them, and have been very happy with the stock (Genuine BMW) stuff. I like letting the INTAKE make all the noise. :D

 

Edited by wegweiser

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I'll be the guy who steadfastly says you are leaving power on the table with this setup.  A basic header and exhaust upgrade are definitely noticeable in your situation.

 

As an example (and one I've posted in the past) here's an actual dyno showing the power difference using a stock 2002Tii as a test (done by a curious customer at the time).  The baseline is using the stock Tii system in good working order and the second line shows the IE step header with exhaust.  I'd love to see other actual dyno results.

 

 

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I remember that article, funny they mention the Alpina header being a ' rare bird ' in 1985 (what the heck is one now in 2019 almost 25 years later?).  +1 with every other post here - especially with the fitment and longevity the stock tii Eberspacher system provides.  I too would probably try out one of the repop Alpina down tubes (original Alpina version on bottom) - fyi this is what they look like.  I might as well port out/match a tii manifold with the head.

80.jpg

81.jpg

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No matter what type of exhaust you select, I highly recommend having it coated (both externally and internally) by a company like Jet Hot (or Swain Tech).  The "Sterling" coating applied to my 73 tii exhaust manifold and down pipe in 2008 has held up very well (NO RUST) and reduces the under hood temperature.

 

I just shipped my stock tii exhaust manifold and (new in 2016) downpipe from the 69 to Jet Hot for coating using their satin black coating (oddly enough, the color code for the satin black is "2002"). 

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31 minutes ago, markmac said:

I remember that article, funny they mention the Alpina header being a ' rare bird ' in 1985 (what the heck is one now in 2019 almost 25 years later?).  +1 with every other post here - especially with the fitment and longevity the stock tii Eberspacher system provides.  I too would probably try out one of the repop Alpina down tubes (original Alpina version on bottom) - fyi this is what they look like.  I might as well port out/match a tii manifold with the head.

80.jpg

81.jpg

The one on the bottom (first pic) and right (second pic) sure looks like a stock 2002 down pipe to me.

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45 minutes ago, AceAndrew said:

I'll be the guy who steadfastly says you are leaving power on the table with this setup.  A basic header and exhaust upgrade are definitely noticeable in your situation.

 

As an example (and one I've posted in the past) here's an actual dyno showing the power difference using a stock 2002Tii as a test (done by a curious customer at the time).  The baseline is using the stock Tii system in good working order and the second line shows the IE step header with exhaust.  I'd love to see other actual dyno results.

 

 

Andrew - thanks for re-posting that.  Hard to believe it was over 5 years ago.

Jim

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28 minutes ago, jgerock said:

The one on the bottom (first pic) and right (second pic) sure looks like a stock 2002 down pipe to me.

 It does, but it isn't - tubes are larger.  I could be wrong on this one and I am sure one of my older German friends will know, but I want to recall that headers weren't approved by the TUV back then on street cars (?)....they did make headers both the try-y and the 4-1 but for racing applications.  Looking at this old pic (early 70's) you can see one of the downpipes (along with a header) and a bunch of the other 'goods'.  I have looked at this photo many times and the first time I noticed the knife edged crankshaft, I guess racers have probably been doing this for a long time (clearly they have) interesting though that not even my Alpina engine sans Schnitzer cylinder head had one of these.

116.jpg

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Thanks for the feedback.  It's interesting that all of you used the tii exhaust as the baseline, while I was inquiring about the non-tii bits :).  I take it then that the non-tii approach is definitely a restriction?  I prefer my exhaust to be quiet and hence have not really looked into headers.

 

The car will use an e30 intake and MS3 fuel injection.  The throttle body is larger than the 318i TB so I don't expect that to be a problem.  Airbox is from the M20 so again, it should have decent flow.  Usage is street driving, no racing.

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1 hour ago, markmac said:

I have looked at this photo many times and the first time I noticed the knife edged crankshaft, I guess racers have probably been doing this for a long time (clearly they have) interesting though that not even my Alpina engine sans Schnitzer cylinder head had one of these

Tricked up parts like seem to be appealing to a certain crowd, but it;s a rare day that any parametric study is published showing the results from the one and only the one modification.  So without a study and unless something makes sense engineering wise, i consider it fluff and waste of money.

The only study I have seen that adds substance to the b.s. is the header study by Stahl.

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