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PostPosted: Mon Dec 01, 2014 11:04 pm 
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hey, I kind of like the black air box. it suits the rest of the standard looking car. notice any increase in torque or smoother low down power with it on?


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PostPosted: Tue Dec 02, 2014 6:19 am 
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That's a good job you've done on the exhaust, no need to buy headers or extractors since that will be every bit as good.
The old rule of thumb for oil pressure was 10psi per 1000rpm give or take a bit. You don't want to go too high or you start to blow off oil filters (seen it before) and do bad things to bearings (so I've heard). The pressure can be adjusted a bit with the pressure relief valve on the oil pump housing, or just get a new pump which means less ignition timing problems and smoother running.


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PostPosted: Tue Dec 02, 2014 6:42 am 
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really?
the next thing i was going to do was to make a set of headers out of mandrel bends, i know the generic style headers are crap, i have 5 sets of extractors and this system looks way better. i was just going to use one of the sets of extractors for its flange.
and up the pipe size for the rest of the system to 2.25 in, its currently at 2 inch.

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PostPosted: Tue Dec 02, 2014 6:53 am 
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oh and with airbox, i noticed a significant reducion in evrything.
as i said i seriously just hacked the sh*t out of it for the rego check
[ img ]
[ img ]

if i was going to use something like this i would need to make it out of a L6 twin su airbox as they are longer.
and i would need to make it deep enough so i could run the ram tubes.

[ img ]
as you can see the 48 dco carb is actually a 55mm carb all the way to the aux venturi, the slip in ram tube makes it a 48
[ img ]
[ img ]

so the ram tube has to be used other wise the carbs are just to big.

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PostPosted: Wed Dec 03, 2014 6:41 am 
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The stock cast iron exhaust manifold is a lot better than most people give it credit for. If you do launch into making your own extractors there's some clues that worked on my car that seem to go against "conventional wisdom"

1. Small diameter primary pipes, not "big bore", to keep up the high speed of the exhaust gas.
2. Secondary pipes 3ft long, there'd be a way to calculate this....
3. Collector 10 inches of 3 inch then the rest of the system, 2.25 inch or whatever you plan

That suited a NA 200hp L20b


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PostPosted: Wed Dec 03, 2014 8:48 pm 
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I'm definately keen on building a full system.

Do you know what pipe diameter you used for primary and secondary pipes.

I'll be looking for a lot of info about what works and any formulas for calculating diameters and lengths.

Did you just use 10 inches 3" strait tube after the collector then reduce into the 2.25" or was it like a megaphone ?

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PostPosted: Wed Dec 03, 2014 9:12 pm 
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Also done a couple of runs to check the afr. With the new wideband.
Just done a couple of 2nd 3rd gear pulls.
I have 65f8 idles, 150mains, 155 airs, f7 emulsion tubes.

Idles at around 14.5 afr
Cruises about the same step on the pedal and as revs rise
The Mid range is about 9-10 afr the leans out at High rpm to around 12.5 which apparently is what I'm chasing.

Then with the same jets with f2 emulsion tubes.
Same deal with the idle and cruise but step on the accelerator and it pulls a lot more cleanly than with the f7s and it seems to maintain a steady 10.5 through the whole main circuit.

Then I tried with the f9 emulsion tubes. And I just can get these to work, they just won't transition. Way way lean off the scale when in transition. You basically have to feather the throttle about up untill 4000rpm.

At any rpm I can dump the throttle with the f7s and f2s and they will build revs after a split second 22 afr rush of air. The f7s are richer low and leaner high and the f2s are rich but steady through out, so I'm thinking of going down to a 145 with the f2s to lean the main circuit out

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PostPosted: Wed Dec 03, 2014 9:48 pm 
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for the extractors take a look at this

http://ozdat.com/forum/viewtopic.php?f=27&t=17386

lots of info that may help.

I would have thought there would be great aftermarket available for the L? try some Japanese places? yahoo JP?

I've been fixing some extractors instead of building from scratch and building an exhaust too and it takes a loooong time!


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PostPosted: Thu Dec 04, 2014 6:31 am 
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Nad015 wrote:
I'm definately keen on building a full system.

Do you know what pipe diameter you used for primary and secondary pipes.

I'll be looking for a lot of info about what works and any formulas for calculating diameters and lengths.

Did you just use 10 inches 3" strait tube after the collector then reduce into the 2.25" or was it like a megaphone ?
I can't recall what size the primary pipes were but it started life as a brand new set of HM headers for stock 1600, smallest pipes I could find when everyone else was going big bore, special order. Flange and gasket were mated to the head and exhaust ports like you did.
Secondary pipes were cut off and the junctions on the inside of the primary pipes were welded to fill any gaps and then hit with the die grinder to clean them up - fixed the "out of sight out of mind issues" since the manufacturer only welds on the outside of the pipes.
New secondaries were each 3ft of 2 inch, needs to be bent up once the primaries are fitted to the engine in the car to get around the steering gear and firewall.
"Collector" was just a 10 inch piece of 3 inch to bring the 2 secondaries together. The was no special fittings or anything, the exhaust guy just made it all fit. I was told after that I could do anything I liked with the rest of the system, within reason.
To suit rallying I had 2.5 inch for the rest and had a slip joint about a foot or two back from the collector and a straight through "turbo" muffler after the diff. Pipe went over the half-shaft and muffler mounted diagonally under the boot floor and the exit on the right (instead of left like standard). No spare wheel well.
2.25 inch pipe would have done for anything but rallying, the 2.5 inch allowed for some crush and damage.

Formulas unknown, I was told exactly what to do by a experienced educated engine builder and long time rally freak that had spent a lot of time on the engine dyno and then chassis dyno with the L20b with twin 45 Webbers over a few years.


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PostPosted: Thu Dec 04, 2014 1:15 pm 
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I plugged a few different values into a calculator linked in one of the other threads and got primary lengths of 28 inches and 1.2inch dia pipe up to 29 inches and 1.25 inch dia pipe - used from standard L20b exhaust and bore/stroke values up to a bit oversize with bigger valves. You'll need to plug in your own values to confirm.
So there's not a lot of variation in primary pipes over a range of L20b performance.
I noticed many people have short secondary pipes, that come together and join to one (what i called the collector) just under the firewall - mine came together further back more under the pasengers feet, being 3ft long.

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PostPosted: Thu Dec 04, 2014 2:03 pm 
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Yeah I had a go of that aswell, but how do I work out my volumetric efficiency and also the exhaust valve centre line??

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PostPosted: Sat Dec 06, 2014 7:41 am 
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if your after a good bolt on set of extractors im told the pacemaker ones are good for sizing and design and ok for up to around 170hp.

I bought this set for $20 but they need work. I was told they are too big for my application and would work well on a plus 200hp engine. they have a unique design which I really like on ports 2 & 3. also see attach doc for some interesting theories if you making your own.


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11203d1321416009-4-1-extractor-design-exhuast.doc [191 KiB]
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H2.jpg [ 226.16 KiB | Viewed 4022 times ]
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PostPosted: Sat Dec 06, 2014 9:46 am 
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I have two sets of pacemakers headers.
But my set up of the cast manifold and y pipe looks a lot better. I'm pretty sure the pacemakers would be a step back.

Are those ones hm headers ??

I'll check out that link, as I want to make my own

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PostPosted: Thu Dec 11, 2014 1:08 pm 
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[ img ]

Stole this pic out of the ozdat classifieds, I was also wondering if anyone knows the science behind this collector. See how it reduces just after the collector then flares out to match the rest of the system.
It's something I have seen a few times and wondered the reasoning.

Something else id like to incorporate

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PostPosted: Fri Dec 12, 2014 12:14 am 
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from what I've read the 'megaphone' setup flattens, a torque curve for more linear power delivery. especially with 4-1 collectors.


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