engine question

[Mopsdrops]

Hi,

I've got some questions:

If you are tuning a car into high bhp's by installing a turbo setup, can you still do a N/A tune up afterwards like changing the pistons, valves, valve springs, retainers, camshafts, etc... ? Cause like in GT4 you would have to chose: N/A or Turbo, so I don't know if you could mix the two in real life

2nd, what is it all about those compression rates like 11,1:1 ? Can someone explain a bit more about this, like why they calculate this etc...

Thank You

[nthfinity]

well, i may not be the best to explain; but i'll try

high compression (like 11:1) means that it packs more mass of air in a smaller location; heats it because of compressing it; then when mixed with the fuel, and sparked; it has more resistance to staying compressed... essentially adding some torque.

with high compression; you also get more problems with knock (pre-detonation) which is basically diesling the engine... definately not good; this is why running a higher octane is nessiary for high compression motors... higher octanes burn slower; and require more energy to detonate.

turbo/supercharged motors generally run a lower compression ratio; which is evident by low rpm bog, and general lack of throttle responce... however, once boost pressure is there; true compression ratios could be 11:1 - 16:1 and perhaps higher since that volume of air is forced in there by the impellars.... this is also why its good to run high octane in low compression turbo/supercharged engines... to reduce knock.

after turboing an engine, of course you can change pistons; valvetrain, everything. afterall, its still an engine

[Mopsdrops]

Originally Posted by nthfinity well, i may not be the best to explain; but i'll try high compression (like 11:1) means that it packs more mass of air in a smaller location; heats it because of compressing it; then when mixed with the fuel, and sparked; it has more resistance to staying compressed... essentially adding some torque. with high compression; you also get more problems with knock (pre-detonation) which is basically diesling the engine... definately not good; this is why running a higher octane is nessiary for high compression motors... higher octanes burn slower; and require more energy to detonate. turbo/supercharged motors generally run a lower compression ratio; which is evident by low rpm bog, and general lack of throttle responce... however, once boost pressure is there; true compression ratios could be 11:1 - 16:1 and perhaps higher since that volume of air is forced in there by the impellars.... this is also why its good to run high octane in low compression turbo/supercharged engines... to reduce knock. after turboing an engine, of course you can change pistons; valvetrain, everything. afterall, its still an engine

Thank you very well Nthfinity for the information, and very quick thanks

[ZfrkS62]

Originally Posted by Mopsdrops Hi, I've got some questions: If you are tuning a car into high bhp's by installing a turbo setup, can you still do a N/A tune up afterwards like changing the pistons, valves, valve springs, retainers, camshafts, etc... ? Cause like in GT4 you would have to chose: N/A or Turbo, so I don't know if you could mix the two in real life 2nd, what is it all about those compression rates like 11,1:1 ? Can someone explain a bit more about this, like why they calculate this etc... Thank You

This is the reason i am setting up those new info sections. Good questions like this always lead to informative answers.

Nth's post is pretty much it in a nutshell.

http://www.motorworld.net/forum/showthread.php?t=20209

this is an article one of our members, who has become a lurker, wrote awhile back on turbocharging. It's pretty long and contains alot of really good information that i think will answer your question.

Most engines can go from NA to FI with no work being done to the internal
components providing you don't run any more than 6-7psi. However you can't take the turbo/supercharger off an engine that was setup for it right out of the factory.

Same as setting up an engine to handle high boost pressures. You can't revert back to NA without changing the internal components back to a natural aspiration set up. IF you were to do this, it would be cheaper just to have a NA engine laying around in anticipation.

[T-Bird]

Well like has been said before you can get all new internals and cams that are specific to boost applications along with larger injectors and colder plugs also porting and polishing your head/heads and the intakeand exhaust manifolds never hurt with either an NA or FI engine aswell as oversized valves. Dished pistons for example are great for boost aplications to lower the compression ratio down to roughly 8:1 - 9:1 idealy but (like in my case) 10:1 is very doable but no more than 10 pounds is really recommended. in an NA motor you might go with raised pistons with valve reliefs to get a higher CR. I am assuming you would be interested in doing this on a Honda engine (possibly a prelude or ITR) I would say you can keep your engine mainly stock but get bigger injectors and colder plugs then get the computer fully remapped not just chipped. for a little better response I would even change the cams, then you will be in a good place for a Honda.