I have a 99 neon. What would be the best route to go? How much more horsepower would a 2.4 w/turbo have and how much faster?

the larger the displacement, the more power you can gain from a turbo. especially the 2.4 as opposed to the 2.0. turbos like a long stroke! you will be able to make more power over a broader power band!

the larger the displacement, the more power you can gain from a turbo. especially the 2.4 as opposed to the 2.0. turbos like a long stroke! you will be able to make more power over a broader power band!
how much more power would the 2.4 have though?

there are too many variables to say that off the cuff. i need compression ratios, boost levels, etc! expect it to make a significant amount more. hows that...

you have more displacement, meaning more volume of air moving in and out. you can spool a larger turbo faster, meaning more air in and out again meaning more power! a long stroke is going to produce more torque lower in teh power band. if your limiting yoruself to pump gas, the 2.4 will be the way to the most power!

Is your 2.0 a SOHC or DOHC?

Is your 2.0 a SOHC or DOHC?
dohc

You could start by transplanting a 2.4 into your Neon, tuning it up some and then decide if you need more speed. 2.4s seem to respond better to turbo than the 2.0. You would get more HP per $ if you turbo the 2.4.

The SRT-4 Dyno's in at roughly 200HP @ the groun, on a DOHC 2.4L. So at similar boost on a stock 2.0L i dunno 170-180?. However TEXSRT4 is right it is hard to just pull numebers out of the air. With your older 2.0 you need to lok out for the strength of your internals probably aren't 20psi ready.

the srts dyno in at 230hp and 250ft/lbs of torque stock. so thats more than normal boost levels on a stock 2.0. but can take 500 (if tuned right) on stock internals! so you wont have to build anything. just add more boost. otherwise you will have to build your 2.0

those numbers are at the tires