VVT question?

[Nick3814]

I know the RS engine is a variable valve timing unit so if I'm right it gets to a certain rpm and surges for want of a better description, is this right and if so at what rpm does it do this?

Whilst running mine in I'm not going over 4000rpm till 600mls and then I'll gradually build it up until 1000mls when it'll get the full beans.

Really happy with its performance whilst taking it easy, just wondering what to expect once I've ran her in?

Cheers guys

 

[oscar]

nick, perhaps best to ask neil about this directly as he really does know the ins and outs of the engine, plus with all the recent cam work he has undertaken he will definately give you the beans on all there is to know! i've a feeling what you should look at is some dyno graphs to see where it begins to get properly steep though?

 

[mrbushrat]

Really starts to get going above the 4k mark. Mine has just over 50k on the clock now and runs sweet and feels like it's one of those engines that will keep loosening up. My 170k puma will still happily rev to 7k and do 125 the engines feel pretty similar.

 

[DrDrew]

The vvt kicks in around 3750-4000. You'll feel a bit of a flat spot in that area when accelerating, but it picks up quickly after.

 

[user 980]

 

[Nick3814]

:-D :-D :-D

Great thanks guys

 

[singlespeed]

The vvt kicks in around 3750-4000. You'll feel a bit of a flat spot in that area when accelerating, but it picks up quickly after.

^^^ this. Although it can be reprogrammed as part of a remap to come in whenever.

Its not going to be a big change in performance like the honda vtec which is effectively like having standard cams for low down and fast road cams for higher revs. All its doing is moving the inlet cam timing, so ithe inlet valves open earlier in the cycle, so the cylinder filling gets going earlier and more efficiently due to the exhaust gasses exiting causing a lower pressure. This wwouldn't work so well at lower engine speeds as there would be too much overlap and the idle would be like my stage 2 profiles were originally... lumpy as hell and not liking to idle but goes well top end.

So, you have a relatively high lift set of cams as standard, with enough overlap for idle/emissions etc. Extra overlap for better top end performance/efficiency.

 

[Adeyspec]

thread revival. can anyone actually confirm the type of vvt on the twingo? is it on/off like a 182 or fully variable like the 197? also id be surprised if it switched at 3700-4k the f4r runs it on from about 1600rpm, the kick is usually when the engine just gets into its stride for inlet length and cam timing.