4G13/4G15 modifications guide Jan 30, '08 11:27 PM
due to many repeating new topics asking about modifying 4g13.4g15, i would like to give some guidelines on modifying these engines.
1. intake and exhaust
intake: keep the original air filter. those apexi, K&N, HKS power filters won't increase HP dramatically on small, NA engines. but CAI (cold air intake-DIY) usually help.
won't increase fuel consumption(standard)
exhaust: follow original route, 1.7/1.8 inch is the best. use big mufflers. for max acceleration, don't use mid silencer(bullet). for balance between pickup and top speed, use 1 bullet. for better top speed, use 2 (or more for hardcore) bullet. use powerzone extractor, it is the best for 4g13/15
slightly increase fuel consumption
2. spark plug & cable
best spark plug cable is the standard one. for spark plug, i think bosch super 4 is recommended. don't use platinum, iridium, or others...
3. port and polish
this one is the best mod. clean out carbon from engine head. (like top overhaul). can feel better power across all rpm range.
get powerzone camshaft. for more hardcore users, use semi/full race cams. remember to make sure fuel supply is enough.
not necessary to install bigger valves, unless u got valve fetish
just get wira 1.6 front brake system. more than enough braking power.
standard items are good enough. make sure that they are in good condition.
8. tuning-the most important part
make sure that ur engine is properly and regularly tuned. and make sure that u have enough lubrication(i destroyed 2 engines because of neglection of lubrication)
9. rim size
most ideal is 14inch, not too heavy, not too small.
10. fuel regulator
this is a good mod. recommended as first mod.
11. performance carbs
hehehe this one, no need to say la. weber is the best. twin 40dcoe for those who doesn't mind its fuel consumption. 40dcnf for moderate power increase. additional/better fuel pump supplies more fuel to the carb.
12. gearbox mods
manual-use wira 1.6 clutchplate. lighten flywheel(lose top speed)
auto-no hope. just dont over rev ur engine. 1.8 supertouring auto box fits saga 1.5 engine perfectly.
13. engine block mods-lighten crankshaft, crank pulley, ...
piston- try to keep them standard.
14. for those using 4g13/15 with siemens ECU, sorry to say: NO HOPE!
15. finally, full engine balancing. usually after u don't have anything to add anymore.
tips for saga megavalve owners: use wira 1.5 block. it has lighter internals. and use wira 1.5 injection standard camshaft. u will feel power increase after installing the mentioned items
tuning tips for beginners: try to keep as many things standard as possible, because they are cheaper to replace when they break down.
tune engine regularly. make sure fuel supply is enough.
p/s change to bigger displacement engine-better! no hassle...
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