one of our local guys up here went nuts on his EL XR6 and got 350kw at wheels and its still not fully tuned up ... add another 30% on that figure and u got ur figure of power at the fly ... the I6s LOVE boost
He also spent a stupid amount of money and waited 8 months for the result, when I know of at least one car that'll be keeping up that have spent less and been on the road more (no, not mine). But that's a whole other argument.
How far could you go Naturally Aspirated though? Well how much are you willing to spend? Rebuild it high compression, massive cam and headwork, good extractors and exhaust, change the ECU, maybe stroke it if that's possible and you might push 250kw at the fly. Maybe. That's a bit of a guess...
performance costs money - how fast do you want to spend?
there is a place down here that can port an AU head to flow a little over 400hp, and i think for a complete head they want about $2k (dont know if thats exchange) and i think you get a cam as well.
IMHO a MAP sensor based system would not be a good thing to use in this application, so an aftermarket MAF based computer would need to be bought and tuned, with a 6000 or more rpm redline.
i would start with an AU engine, rebuild it with an ACL 'race' series rebuild kit and a little more compression, get the head ported by the blokes down here, get a custom intake manifold made up with either one very large throttle body or two slightly smaller ones (you would have to work out what is the best length for the intake runners, and see what kind of setup that requires) and then see how you go.
extractors would be a very important decision too - custom ones may be needed, failing that possibly the new JMM style might work well, or the pacemaker 'competition' series - the primaries may be too small for this kind if output though, and also they have to match the cam for optimum cylinder filling.
gm destroya has more info on the people that port the head - maybe PM him for details - he is building a MASSIVE hp turbo I6 at the moment and the shop used his head as a testbed for their porting.
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There is no doubt that a 200rwkw turbo car will be a shitload more drivable then a 200rwkw N/A car.
But, im considering going with a turbo setup at a later stage, but because I have done quite a bit of N/A tuning, it gives me a good starting point for a turbo set up.
Hold your breath, count to 10, fall apart, start again
I have a mate with an el xr6 who claimed 2 have something like 198rwkw from an n/a el xr6. Now, i never believed him, and reading the last few posts, i can rest assured, i was right!!
Just out of interest, he has following mods: Exaust, extractors, cai with k&n, cam, port/polish (i think), 5ltr injectors, bigger fuel pump, with wolf 3d computer controlling fueling and ignition. Is auto (which robs power too).
Im thinking he got mixed up and meant 198rwhp, but he seamed pretty sure bout the dyno fig..... Anyway, whatta u guys think.
A Dyno can be made to read anything the operator likes, really. I was getting 137rwkw with a similar setup to what you're describing there, 4ltrpwr. Add a couple kw at the sacrifice of drivability and reliability, maybe...
Just decide before you start anything if you'll ever take it to the stage of forced induction. Because a big HP NA engine is not going to like forced induction as much as an engine specifically set up for it.
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