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Originally Posted by crrrazy
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Yea but the thing is, a big motor can always be modded to rev higher and handle a lot of boost too :-)
Look at the 428 LS7 V8 GM is building for the new corvette and God knows what else they are putting that beast in. 7k rpms the motor can make power to, its sold to only rev to 6,400 and the power is turned down stock for emissions, it has high compression(not sure the exact numbres but i believe it to be 11:1), TITANIUM lightweight strong pistons that could probably handle loads of boost if the the thing didnt have such high compression, but i imagine the high compression in conjunction with even low boost would make insane power. My neighbor works at the tech center in the town next to mine that builds the LS7. He said the motor can make over 550 hp@7k rpms if you let it do what GM intentended it to do. Now remmeber this is a push rod motor, however it has titanium valves, connecting rods, pistons, push rods, rocker arms, just about anything that moves in a recipocating motion in that motor is titanium. This allows it to make more torque at higher rpms which in turn equates to more hp.
Now you could do the same to any large displacement motor if you have enough money, then you could rev them high. Its hard to make a small motor bigger, and in the long run size does matter.
My ideal motor would be a 5.0 litre I6 with SOHC and 4 valves per cylander with variable valve timing much like hondas 4 valve SOHC set up with VTEC. Then you'd have the motor run at relativley low compression (since this thing would be a torque monster already down low) you could use low compression then have 2 turbos on it plumbed after a cross flow exhaust manifold. Have short runners for the small turbo, have long exhaust runners for the big turbo. This will allow for high boost levels at all rpms in conjunction with the low compression motor. Then have titanium rods, pistons, and a lighter crank, make the motor built to rev to 8k rpms. Use a dual runner intake manifold with IMRC valves to allow cross flow and to block off the long runners at high rpms and block the short runners at low rpms. Then you'd have the compressors hooked up to two seperate pipes that flow through an x pipe to two seperate TBs, the small low rpm turbo hooked up to the long runner TB, and have this long runner part of the intake manifold be somewhat rougher surface than the short runners to help atomize fuel better. Also inject the fuel closer to the TB in the long runners so that you could get more torque and better fuel atomization. Then the big turbo pipe would hook up to the other tb that hooks to the short runners.
At the exhaust end have variable geometry nozles on the turbo and have the two turbos have seperate exhaust pipes that run parrelel and through an x pipe then out two tips at the back, have a wider exhaust pipe for the high rpm turbo, and a narrower exhaust pipe for the low rpm turbo to regulate back pressure. The x pipe will help regulate the back pressure.
This is my dream motor, also the engine block would have to be built with the best strength possible, have 4 bolt main caps, a forged steel stud girdle, and have 7 main caps.