Exhaust manifold choice(s) for 1.6L NA

[ktzdsl]

I am working on a 1982 pickup with a 5 speed manual transmission.
I am finally putting together a 1.6L NA engine using a 1.5L dual manifold connecting to a 2" TT dual downpipe and exhaust system.
Will this improve the breathing capability or should
I be looking for a "gasser cross-flow" exhaust manifold?
If so, can any one tell me what the part number would be?
Thanks.
ken

[burn_your_money]

The combo you have planned is definitely better then stock. I'm not sure how the x-flow one compares

[ktzdsl]

Thanks for your response, Tyler. I just wanted verification that
I would be ok. I will also induce cooler air via the rain tray.
I just have to note that you are one busy dude.
ken

[burn_your_money]

Can you explain your cold air induction idea a bit more please?

[ktzdsl]

Here is Roger's approach:

http://www.4crawler.com/Diesel/CheapTricks/index.shtml#ColdAirIntake

I can lookup my saved pics of the other approaches if you like. Let me know.

[Baselyne]

I just had a broken N/A downpipe and I swaped it for the Gasser Race header manifold! I got crazy gains off that one maybe partly due to the broken one before but it sure felt like a huge difference in breathing!

Id recomend this.....its way more flowing than my stock N/A manifold!
Just putting in my two cents.....

[Pat Dolan]

Don't sell the gasser two hole manifold short.  It flows quite well, and if you make a decent secondary (length is important, 99% of aftermarket secondaries are far too short for bifurcated "Y" systems) and a nice big system behind it, that can outperform all but the very best of 4:1 race headers, and far, far better than "shorty" headers with ugly collectors.

Oh, you were about to ask about length?  For gassers that would wind up fairly high, I found about 32" to be good, but a diesel's lower revs would want to be longer.  However, the shift box pretty much dictates where you have to stop.  I used to make little ball joints to allow the flex to happen on a plate bolted to the manifold flange.  You need to let the system flex somewhere, and the closer to the manifold, the better.  However, this takes some serious machine work and fabrication, so the other option is to just use some stainless 1.5" (ID) flex pipe on the horizontal runs, and replace it when it fails (and keeping the vibration brace on the bottom).  The accordian flex stuff (which includes the pretty looking braided stainless stuff - that is just another accordian pipe inside) does not flow worth a hoot.

Consider a very straight through muffler if you are going "all the way", with perforations, not flutes that protrude into the airstream.  Some of the ricer fart cans are actually pretty good.

[Vanagoner]

I have a 1.5 petro dual exhaust manifold too (not installed).  Is there an advantage to keeping both pipes apart thru the whole system, including a 2 in 2 out muffler (like a BMW) ?  Should the pipes be made to come out the same length, or doesn't it matter?   At this point I'm thinking of just supercharging it, so I have different exhaust options than most builders here.

[Pat Dolan]

I have a 1.5 petro dual exhaust manifold too (not installed).  Is there an advantage to keeping both pipes apart thru the whole system, including a 2 in 2 out muffler (like a BMW) ?  Should the pipes be made to come out the same length, or doesn't it matter?   At this point I'm thinking of just supercharging it, so I have different exhaust options than most builders here.

The concept of "interference tuning" for four cylinder inline engines is to put 1+4 and 2+3 together as quickly as possible, and then run the secondary pipe out to a length where it is the longest possible length to resonate at a frequency the co-incides with your target RPM for best scavenging.  That is fairly long for lower RPM (over 40" for most little diesels), but the flow really wants to dump into a single pipe to provide a reflective surface for the secondaries to resonate against.  I think you will find that the BMW you are looking at will be a six cylinder, in which case long primaries and seconday system with two collectors (i.e. conventional "headers") works quite well.

[Vanagoner]

Ah.  Great knowledge and information- thanks.  If you still have patience on this subject, I'd appreciate your help (and others) optimizing the design for my vanagon.  The '73 Audi manifold has the two pipes going back together into a Y.  On the vanagon, they will be pointing forward.  Should I unbolt them from the cast part of the manifold and turn them around, or keep them pointing forward, making 2 u bends to achieve the correct length before bringing them back together ahead of the muffler?  I would have much more  length to play with in the second option, but the addition of u bends is not the greatest.  I have room for about a 14 inch dia. bend.  
Also, I'd like to optimize the length for whatever the rpm's are at 60 mph with an air cooled 091 vanagon transaxle.  I don't know what that will be, but I'll dig a little.  Thanks.

[Pat Dolan]

Is your Vanagon going Audi 4 cyl or 5 cyl?  I ask because one of our projects this winter is to put 2.5tdi into T3 Syncro Westy, and want to hear from others who have used the Audi engines.

To answer your question:  Yes, put the pipework forward and then use some mandrel bends to turn it back.  The rear installation is particularly difficult because, as you can see, there isn't enough room to put a proper exhaust in, and you have to make trombone pipes to fit stuff in.  For us, no biggie, the turbo does most of the work and the tailpipe is not critical in length.

[Vanagoner]

Pat, my last camper was a Syncro, had it about 10 years.  Some bad luck, and I couldn't afford to keep up with syncro maintenance.  So I sold it, paid some bills, and got the diesel.  I'm keeping the 1.6 4cyl.  The manifold is from a fox with the 827 series 1500 engine.  I plan on installing a Mercedes c32 IHI lysholm supercharger, and no turbo.  so lengths probably will make a lot of difference in my installation.  I'm planning it this way because, being a truck, the super will give me the "grunt" that I need for normal traffic and an upgeared transaxle, And I can disengage it at cruising speed and get the same economy as an n/a.  Plus, I don't know of anyone else who has tried this on a Westy-  It might be a good performer.
Your 5 cyl D T3 sounds great- best of luck.
BTW- where do you hail from?

[Pat Dolan]

Sage:

You STILL need an exhaust system with all of the important tuning and flow features for a supercharged engine - much moreso than a turbo installation (except when going for broke in turbodome).

I live in Martensville SK (just North of Saskatoon) but my office is actually in Sheridan WY.

Pat

[Vanagoner]

Hi Pat, we're practically neighbors, sometimes.  
I figure on keeping the diameter of the double pipes small like stock, to keep the velocity up for better extraction at the head.  I'm guessing about 42 inches before the Y to optimize @ 3200 rpm.  Does this sound about right to you?
 I'll make the exhaust when it warms up outside, and put it on the n/a first before I play with the kompressor.
Thanks again.

[Pat Dolan]

Sage:

Seasons Greetings, neighbor.

Yes, the length sound right, and I have been using 1.5 inch 16 gauge for the secondaries.  However, the merge point is usually defined by where the shift "lump" is in the tunner, making the secondaries a lot shorter than ideal.

Pat