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Seeking info on upping displacement on my 3.0L

29 February 2000
St. Petersburg
Hey all...
For some time now, I've been considering the various options an NSX owner has to gain precious HP. My '94 makes 268rwhp with headers, exhaust, intake, chip and no cats. I'd really like to bump that up to 350rwhp and have toyed with the ideas of adding a supercharger (Comptech) or NOS. I'd really like to hear from someone who has either increased their displacement or someone who knows what parameters are possible with the 3.0L NSX engine specifically. I'm getting about 105hp/Litre at the crank. If I could bump that displacement up to say, 3.6L...hmmmm...that would be fun. I don't know if that's possible...cylinder wall thickness, etc...Any constructive input is greatly appreciated. Thanks!
My GUESS (big guess) is that increasing displacement on a 3.0L is pretty difficult. Honda had to move over to using the FRM (Fiber re-inforced Metal) process in order to shave the cylinder wall thickness down to something like 3mm or something. Again, my guess is that without the block cast with the FRM Cylinder Sleeve's you cannot Bore the cylinder out, so the only option would be to stroke it. which might work, with I would venture to guess that you would lose the fast revving capaibilites that make the NSX so wonderfully fun to drive. Not to mention new Connecting Rods for a stroked engine have got to cost an arm and a leg..and possibly your soul.
Again, these are all guesses.. I've also considered doing the same myself. So if anyone has better info please let us know..
Are you willing to risk experimenting on an engine that lists for $23,000 without any reason to think that you can get the gains you're looking for?

Leave the product development to the pros, places like Comptech where they can spread the product development costs over dozens (or hundreds) of cars. (If there were an easier way to get more horsepower than supercharging, I'm sure they would have introduced it themselves.)
Originally posted by TampaBayNSX-R:
I'd really like to hear from someone who has either increased their displacement or someone who knows what parameters are possible with the 3.0L NSX engine specifically.

The race cars such as the Dome/Mugen NSXs fielded in the JGTC series are 3.5 but I'm not sure what they are doing to achieve it. That might be a place to start your research. However, they are starting with the 3.2L engine, not the 3.0. Also keep in mind that these are race cars and whatever they have done may not transfer well to a street car.
If you are really serious about getting big forced-induction HP numbers, you need to do two things.

First, rebuild the short block. You MUST do this if you are planning more than 450hp at the crank. The NSX has an open deck design and you will fatigue the block quickly (10K-15K miles) if you don't. Several things are important at this stage. Deck the block, press in ductile cylinder liners, switch to forged pistons (stock suck) and drop the compression a bit. 9.5 to 1 seeems to be a good compromise. Most of the stock rods are fine, as is the crank. If you would like, this is also a good point to do things like coating pistons, Extrude Honing everything, etc. Decking an aluminum block is very difficult and I would not let anyone but Comptech do it. I sent my motor to JG and have had problems with their work. Comptech has done it before and builds Indy car motors, so you know they will get it right. The whole process should cost $5K to $7K and you are essentially getting a new motor.

Second, install a quality programable engine management system with larger injectors. I recommend Motec or Haltech. If you are not getting super fancy, Haltech is the way to go as it is cheaper and simple in comparison. There are also a lot more Haltech dealers.

For some idea of what you will get, 10-12 psi with pump gas will produce 440-460 hp at the wheels. Mech Tec has done several cars with a bit less hp using a modified Bell kit, stock motor and Haltech management.