so i saw on a topic awhile back that said that the 240sx/stanza TB conversion made not a bit of damned difference....is this true or was the person not smart enough to gring away the manifold and port it enough to match it to the throttle body diameter?
Read down a few posts called "240sx TB." Basiclly what it comes down to is that the stock intake manifold and head are more constricting than the TB is so there is no point in putting a larger tb as it will still clog at these points. The only way to actually make the intake manifold better is to get the Engloid plenum which is extrude honed. Just port matching the manifold does nothing becuase it doesn't reach into the insides of the manifold. That is why Engloid started making them as he cuts them open, hones them out, welds them back up. That way the entire manifold, even all the way in the middle, is ported and polished. Still that only solves one of the three problems. You then need to worry about the lower intake manifold which from my understanding is good enough to just port match it. Then lastly you need to do work on the heads. Only at that point will the larger flowing 60mm tb actually help. However by the time you got done doing all this port and polish work you could have bought your self a 300zx turbo or equivalent car for less money and still have money left over to mod it or put towards something else you have been modding. This is why most people don't get far into modding the n/a 300zx. After doing the basic bolt on's, which don't yeild much gain, all that is left is basicly tearing the engine apart and doing port and polish work which can be very expensive.
Whats the point of more flow if it bottle necks? For instance take a coffee straw, you know those small straws, and blow into it. Then take it and cut it in half. Replace the same lenght missing with a regular straw and tape it into place. Now blow from the large end. You'll notice that flow hasn't increased. Better yet look at an exhuast system. Would you expect to gain more hp if you say replaced the entire exhuast with a 2.5 inch pipe but then had it come out a 2 inch tip? No. Flow is only as good as it's smallest point in the system. For the breathing of the VG it happens that the TB is not the smallest part. Also you are comparing na/ to turbo. Mods on a turbo are much more benefical and noticable than on a non turbo. Even still when the guy from Z31.com dyno and track test the larger tb on the turbo version it didn't help. I talked with Engloid when he first started making the plenums about what gains would be on the non turbo. He couldn't say exactly but estimated by the flow that it would probably be 5 or less. Sure on a non turbo 5hp is decent but look at the cost of the plenum plus the larger tb plus install. Thats a lot of money for 5 or less hp. But we are talking about doing just the tb. The tb alone will not allow any more air in. Yes perhaps mated with the larger plenum air would increase a little going into the engine but I would say that if you are going to go with the 60mm tb that it would only be slightly worth it as long as you got the Engloid plenum along with it. If all this flow stuff doesn't make sense get yourself a basic physics book and read the 1-2 chapters that covers flow, pressure, etc.