1nzfe valve and valve springs

[tsu]

Originally Posted by alias06

Stock rev-limit is around 6500 rpms...so how are you up at 7k? For your question I don't think anyone has swapped out 1zz springs for 1nz's. If you had one of each spring, you could do a bench test and get your answer that way.

Thanks for your reply, I have installed a Unichip in my car which has a feature to "open" the rev-limiter.

Originally Posted by xnamerxx

Stock valve springs are good for at least 7800 rpms, 2az spring will bind I haven't tried 1zz springs but I imagine its probably the same. BC valve springs are too stiff for VVT. Stock cam is way out of steam before 7k rpm, I've got plenty of dyno sheets to prove it.

IIRC stock springs are 25lbs installed height and 50 lbs at .4" Brian Crower springs are 1.280 : 48-50 LBS .400” lift 105 lbs

Really up to 7800 rpms??. Actually, the cylinder head has been ported-and-polished and milled. During the dyno test, my mechanic assumes that my stock spring valves are floating at high revs because the horsepower falls steeply after 6000 rpms and the peak horsepower occurs at around 5600 rpms. He added that beyond 7000 rpms, the acceleration feels rough and sluggish (the symptom is similar to incorrect air-fuel ratio; too rich mixture. But it is not because of AFR). To be honest, I'm not sure whether it is caused by valve springs or not. However, me and my mechanic have check all the other parts and variables, and they're on the right track.

Since my cylinder head has been ported-and-polished and milled, will it limit the work of stock valve springs (valve springs float sooner)?. Or maybe, is it because my stock camshaft that cannot provide a longer "breathe" beyond 7000 rpms?. It is quite hard anyway to find aftermarket parts for Yaris in Indonesia these days, especially engine internal parts .