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Does lowering your vtec X- over change your spool time??

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Does lowering your vtec X- over change your spool time??

Old 02-17-2005, 01:10 PM
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Default Does lowering your vtec X- over change your spool time??

You would think that more air make more power right. I would say you can lower your x over point too low and cause the cam to become inefficient. But ive seen in dyno graphs where hp numbers jump big time when vtec kicks in.

For example: In 98CTR's post, it looks like if he lowered it 500 rpm it would smooth out the transition. From 5k to 5.5k he gains about 90 hp !! If you lowered it 500 rpm ,It might bring his torque curve a little down the rpm scale. I dont know what kind of cams your running but im guessing they arnt desighned to flow 190 hp on the low cam =) Let me know what you guys think. And 98ctr if you do change your x over point let me know what happens. $0.02 , dave
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Old 02-18-2005, 02:13 PM
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Default Re:Does lowering your vtec X- over change your spool time??

nobody knows huh ...what ever
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Old 02-18-2005, 04:58 PM
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Default Re:Does lowering your vtec X- over change your spool time??

you know i've thought the same thing. i know its not always beneficial to lower your vtec but if you lower it a little wont it flow more air to spool the turbo a bit quicker correct me if i'm wrong... i dont even have a vtec but some friends do and i've always wondered about this
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Old 03-05-2005, 08:04 PM
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Default Re: Does lowering your vtec X- over change your spool time??

Ive been on boost for about a week now and to be honest i feel a big difference depending on where i set my spoon vtec controller.Car runs best with vtec settings about stock.I lowered it to about 4800rpms and it felt a lot weaker.Then to 5500 felt a lot stronger....Unless you can whip something up on a dyno Id say stock settings are the bomb untuned.
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Old 03-07-2005, 08:02 AM
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Default Re: Does lowering your vtec X- over change your spool time??

You want to set your Vtec RPM to when the High can and low cam make the same torque. The low cam will be dropping off and the high cam will be coming on. Where the torque is equal is where both cams make the same power.

Dyno and set it if you can. Or set Vtec at like 6000 and tune AF. Save that fuel table. Set Vtec at like 4000 and tune AF. Compare fuel tables. Your Vtec point will be the high cam and low cam table that maximizes fuel injected. The more fuel at the same AF means more air = more power.

Or play with the controller so that you dont feel a power difference when it kicks in. If you feel a big surge, lower the RPM point. If it falls flat raise it.
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Old 03-07-2005, 01:39 PM
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Default Re: Does lowering your vtec X- over change your spool time??

I set my vtec cross over where it worked the best and made the best power.

I did try to lower it and it did not like ti.

I did try to put it higher and it was too big of a power loss in the mid range

So I set it where it worked the best for my set up.
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Old 03-10-2005, 10:07 AM
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Default Re: Does lowering your vtec X- over change your spool time??

I hope when people are lowering their vtec point they are fuel tuning also. If you just lower the crossover and don't tune... you'll see very little if any benefits at all.

Get access to a dyno. Tune the car with vtec of 12k :P (so it doesn't activate). Then tune the car with Vtec at like 1k(so its always on). Then set vtec where their torque graphs cross (as mentioned above). Assuming you tune both maps well, this should give you the most power and a smoot transition.
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