Hi
I am developing a hot GA16 engine, and the header and exhaust must be custom fabricated as most parts here
What is the proper tubing diameter for a header and exhaust for a GA16 engine with enlarged p/p ports, custom valve springs, 45 dual carbs, around 300° duration cam and top hp around 8500 rpm?
This is a 80% race and 20% commuting to local events machine
We plan to mount this engine in a fastback B11
Thanks in advance
Sounds like an interesting project. General rule of thumb is 2" exhaust is best for a non-turbo GA16, of course with cams with that kind of duration you might have a case for bigger. I don't know of anyone that's made custom cams, and the JWT cams give 263* duration. The JWT offer .345" lift, what about these ones that you're putting in? Do you really plan on revving to 8500+ rpm?
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Is this forum still full of n00bs learning that you can't boost your daily driver on a part time retail income?
Hey everybody, I’m the proud owner of one of 3 GA16´s that together with Freddy’s and José’s are getting ready to rumble.
In my case, my GA16 has the OEM cams (but I’m planning to install custom cams soon), custom made sprockets, two 40/40 mikuni carbs (with velocity stacks), intake and exhaust ports enlarged and polished, increased compression ratio (10.5 - 11 : 1), lightweight crankshaft and flywheel, aluminum crankshaft pulley, MSD ignition system, etc etc etc. and it actually revs to 8500
I have a 4-2-1 custom made header and I’m not really happy with it, I know I can buy a hotshot header but... us$400?? + usa/peru freight + Peru taxes... NO WAY, so please help us and fill in the blanks
How'd you increase the compression ratio? Shave the head or somethin like that? Why'd you install the MSD ignition system? I thought stock was fine to light off even nitrous and turbo. I would think that 2" would still be appropriate, unless you get a really aggressive cam that can get a lot more fuel/air mixture into the combustion chamber. Maybe 2.25" but I don't really know. Hopefully Wes or James or Mike Young (any of the GA16 gods) will chime in soon. I'd be interested to see what they make of this stuff.
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Is this forum still full of n00bs learning that you can't boost your daily driver on a part time retail income?
I have a 4-2-1 custom made header and I’m not really happy with it, I know I can buy a hotshot header but... us$400?? + usa/peru freight + Peru taxes... NO WAY, so please help us and fill in the blanks
Usually, headers are optimized on a dynamometer after making the initial design decisions. The lengths and diameters of the pipes are changed to maximize the desired engine power/torque. It seems that your application will be an engine with a narrow power band at the upper rpm range unless your transmission cannot take advantage of this power band. Then you will need to sacrifice some power for a broader range.
Bikerfry you are right, we shaved the head so we can get more compression at the combustion chamber, some people don’t recommend this procedure but it worked really good for us.
Maybe I expressed myself wrong, I’m using an MSD 6A ignition module + a Blaster 2 Coil + 8.8 mm accel race wires, not a complete MSD ignition system to try to burn all the fuel poured into the combustion chamber by the dual 40/40 carbs and this worked good too.
Ishadoff, thx for your comments and what do you recommend to get a wider power band at a higher rpm range, speaking in common language I would like to lower some secs on my ¼ mile time.
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Bikerfry you are right, we shaved the head so we can get more compression at the combustion chamber, some people don’t recommend this procedure but it worked really good for us.
Maybe I expressed myself wrong, I’m using an MSD 6A ignition module + a Blaster 2 Coil + 8.8 mm accel race wires, not a complete MSD ignition system to try to burn all the fuel poured into the combustion chamber by the dual 40/40 carbs and this worked good too.
Ishadoff, thx for your comments and what do you recommend to get a wider power band at a higher rpm range, speaking in common language I would like to lower some secs on my ¼ mile time.
Generally speaking 4-2-1 or Tri-Y configurations give wide power band, and a 4-1 yields a narrow power band and higher maximum power. The idea is to use a primary diameter small enough to keep exhaust velocity up but not too small to restrict flow at max power. Also, the longer the primaries, the lower the resonant frequency, and the lower the power band rpm.
I've never designed a header, and have about reached the limit of my ability to help.
Thanks for the data Lew
Seems that its time for some header building on our own, trying maybe a size bigger each time
The hottest engine will be installed in a B11 for regular drag events
The other two are Enrique's (B13) and mine (B12) dailydrivers
It would be great to rev at 9 grand but sadly it wont last too long, besides that kind of config is somewhat funny for everyday commuting...
Mine at least will have big ports (enlarged exhaust ports 80% the intake ports area), lightened flywheel and underdrive aluminum pulley
Stock tranny, we have to deal with our stock gear ratios, mine being a 87 US version coupe has looonger ratios
We'll post results as the developement goes on
Thanks for all the answers
A question:
Is there a reliable calculator for exhaust tubing diam/length f.e.?
I am aware it is just a starting point and exact data is dyno based
Thanks in advance
I've never designed a header, and have about reached the limit of my ability to help.
congrats guys, this doesn't happen often with lew
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A question:
Is there a reliable calculator for exhaust tubing diam/length f.e.?
I am aware it is just a starting point and exact data is dyno based
Thanks in advance
Check this out. I registered and used their header design calculator. It should give you a really good start.
Exhaust yes
Header, is made of primary tubes, equal length to a collector... blah blah blah
As much as I know it is smaller than the collector/exhaust tubing
Would love to examine a stepped exhaust closely...
Linear Mode
