pork
Posted a lot
Posts: 1,655
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I Wanna have a go at building a decentish n/a engine as I've never tried it
Engine will a cg13de from a k11 micra
(I've allready turbo'd/supercharged these engines before)
just fancy a new challenge.
So, what can I do? What's best things to do?
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more compression, more cam (aka more air) add more fuel.
make sure air goes out fast enough.
I've heard one on bike bodies, sounded brilliant.
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pork
Posted a lot
Posts: 1,655
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Well it's gonna be on the cheap as I'm buying a house
(Selling s/charger and turbo btw)
Can you go to big with the throttle body?
What size runners on exhaust, is there a formula that can be applied
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Dec 11, 2014 20:25:34 GMT
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A rule of thumb I've heard about a couple of times is to get the volume of the exhaust runner the same as the volume of the cylinder it's connected to. I'm not sure about the technicalities behind it, but somehow it sounds like it would make sense?
Other than that, the engine is basically an air pump, so anything you can do to increase air flow will increase power, decrease drag/resistance in intake and exhaust, increase max RPM, increase cam lift and duration, dial in some overlap, there is tons of stuff to do, but it's going to be expensive..
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N/A builds aren't really cost effective compared to charged build engines. So on even a more tight budget you cannot expect much.
Ideally, you need 4 throttlebodies, longest intake runner you can physical fit in combination with the largest volume airbox that fits in the same space.
Then the cylinder head needs modifying so it still flows at higher valve lifts. So you also need wilder cams. Finish it off with a 4-2-1 exhaust and some kind of low restriction silencer and you are good to go.
Software like desktop dyno are great to play around.
Aren't Cg13de used in autocross? Maybe pick an engine which had all the work already done. Would be cheaper than from scratch.
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goldnrust
West Midlands
Minimalist
Posts: 1,872
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As Ettorebugatti says, n/a builds are mostly about spending money on new parts, for small gains. That said, for me, a nicey set-up n/a engine is more fun to drive than a turbo engine. It's that razor sharp throttle response and crisp feeling. Yes you can have throttle bodies too large, if they are too large you start loosing midrange and drivability. While it is more expensive to do a proper n/a build, I think if you get a set of appropriate throttle bodies, build a half decent exhaust and fit a light flywheel, you'll have an engine which whilst not significantly faster than stock feels exciting to drive and sounds great. I recommend getting this book to reference: Four Stroke Perfromance Tuning. I've got this book, and the turbo and 2 stroke books by the same author and they are really useful for this kinda of thing. The've got all the formulas and theory that you need to plan a project like this  |
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