Quote:
Originally Posted by some_other_dave
Hmm?? Are you sure?
From what I have read about naturally-aspirated engines, making the exhaust primaries narrower and longer will help with the low-end torque. Narrower and longer pipes are better at promoting flow velocity, but worse for sheer volume of flow. And long primaries (how long? dunno!) can set up the resonance to better evacuate the chamber at lower RPMs than sort primaries.
There is also the effect of any secondary pipes after the collector for the primaries (if you're doing a 4-2-1 header), and of course that of the pipe after the final collector, but they get less and less important the further out you get from the exhaust valve.
Then again, this is all book-learning. And especially when it comes to fluid dynamics, reality can hold an awful lot of surprises that aren't in books...
-soD
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right, I figured he ment soften the torque low down. thats what I was refering to. My car has slightly less down low torque now, at least I think, it drives smoother and pulls lower though, used to not have any ability to drive under 40mph in 5th (2,000rpm) but now I can climb hills at 30 in 5th (around 1,400-1500) so maybe its more?
but, I do have a full race header, very long primaries which are steped up along the way at specifice points, then longish secondaries (4-2-1). every tube is much bigger than stock though, which really uncorks the engine in the upper RPMS, the 421 and long primaries help with the midrange and lower, but they still arent as good as stock.
as far as dyno runs, no, I dont, I havent messed with the computer so I havent. however, there are many many people who have on my car with the same or similar mods done, and almost as a rule, raceheader/full exhaust/intake/no tuning will net you 150-165hp (depending on which parts you use and where you are driving[temps and such]) and with tuning it will jump to fairly constant upper 160's and mid 170's, though one guy got up to 180 with just intake and full exhaust with tuning. bone stock dynos usually end up 130-140hp (160 crank advertised). this is for the k230a3, the k20a2(orz1.z3) will go from 160hp stock to over 200hp (wheels) with those same bolt ons and tuning.