Engines with usable power at lower RPM...?

[darkstrike]

Hi all!

Big fan of a game, but I've found something I seem to struggle with...I like trying to design useful, compact, efficient, yet, decently peppy engines in Automation, usually older Japanese kei-class (550cc), current Japanese kei-class (660cc) and on up to 1.6L or so.

It could just be that I'm incompetent, but I seem to have a heck of a time getting higher hp figures without having the max torque usable only at a relatively high RPM...

For example, in my mainstay, current 660cc I-4 that I am developing, my K4I4NA engine, the max engine speed is 6800rpms...not too high, but high enough to be a decent small engine with high reliability. Ok, that's fine. The power output for such a small engine is about 57.1hp at 6800rpms. Ok, THAT'S fine. Torque is 47.8ft-lbs at 4800rpms. BUT...I'd rather the torque come in a little lower to give the engine better driveability for the small amount of horsepower without having to rev the nuts off of it....say 3800-4200rpms instead....

No matter what I try, I can't seem to lower the max torque to a lower RPM without sacrificing some horsepower. Is there an easy way to do this?

Thanks for any help!

[nialloftara]

You will sacrifice some hp but you can usually tune it to be pretty close, the exhaust would be my first step. Restrict the exhaust a bit, go down a tick or two in size, and try a baffled muffler, that along with a cam under 50 should give you plenty of low end grunt.

[darkstrike]

You will sacrifice some hp but you can usually tune it to be pretty close, the exhaust would be my first step. Restrict the exhaust a bit, go down a tick or two in size, and try a baffled muffler, that along with a cam under 50 should give you plenty of low end grunt.

Thanks for the tips! I had already figured out that playing with the cams had an impact, so I shall give that more of a try and play with the exhaust...what about with VVL?

[nialloftara]

I does for cost though, if you were trying to build for a kei car, they had pretty inexpensive engines, so I was thinking of cheaper tuning methods. one other way is spark advance it seems like a higher raises the peak power rpm so maybe dialing in more compression for a bit less spark.

[Daffyflyer]

VVL will help a lot, as you can have both a good lower RPM cam and a good higher RPM cam

[nialloftara]

Here's a quick engine I made up, it's got about 3 less hp at 6900 rpms, but 2 more torques at 3800rpms for 30 hours and less than $300, I didn't know your stance on sliders so they are all 0. Have a poke around and see if anything is helpful for you.

[darkstrike]

All my sliders are 0 - always are! Thanks, I'll give it a dload and compare it!