whats the massive surge of speed/acceleration after 4.5k revs

[ollie_kerslake]

I was pulling out of a junction the other day trying not to get hit in the rear so I floored it, Once i was in 3rd I felt this massive surge of speed/acceleration after I went over 4.5k revs.

I have heard people talk about cam boosts but whats really going on? mechinaly?

I have a standard 182 no frills and spills

 

[cliobritt]

just goes at 4000 plus eh!
where in plymouth you from?

 

[RichMcc]

its normal, its between 5k and the top of the rev ranage.

 

[ollie_kerslake]

But why does it really go!, it revs to just over 7.5. no it really kicks of after 4k, more than normal! Beacon park in plymouth. u?

 

[cliobritt]

plymstock.
fancy this? £30!!
http://www.cliosport.net/forum/showthread.php?t=174630

 

[Lee]

But why does it really go!, it revs to just over 7.5. no it really kicks of after 4k, more than normal! Beacon park in plymouth. u?

From memory I think it's got something to do with the cams being at their most effective/efficient point at 5k.

BenR will be along with the correct answer if I'm wrong. lol

 

[ollie_kerslake]

no thanks mate, taking my car there soon though for a few upgrades, money permitting. What colours your car?

Lee is know nothing about cars, whats the cams for?

 

[nosluom]

its the vvt kicking in mate and the profile of the cam changing! so i believe anyway. the good old cliosport 5k kick

 

[ollie_kerslake]

vvt (valve timing)? Oh right yeah its great fun!

 

[cliobritt]

http://www.howstuffworks.com/engine.htm
silver mate keep an eye out!

 

[Lee]

its the vvt kicking in mate and the profile of the cam changing! so i believe anyway. the good old cliosport 5k kick

That's what it isn't, but most people think it is. VVT on the Clio only activates at low revs to assist with the idle from what I can remember.

Ben/Fred? Hurry up and give us the full answer. lol

Cams: http://auto.howstuffworks.com/camshaft.htm

 

[ollie_kerslake]

will do buddy, cheers. Sorry for being an idiot I only do electronics and computers! Not a greas monkey yet!

 

[Justin182]

But why does it really go!, it revs to just over 7.5. no it really kicks of after 4k, more than normal! Beacon park in plymouth. u?

As far as i know, its just the cams working at their most efficient point and should kick in at around 5k..... i dont get it as much as standard anymore due to mods but remember it always being insane in 2 gear.

 

[Justin182]

It is not VVT.

Edit: so many posts just came in.

 

[ollie_kerslake]

lee howstuffworks never lets me down. cheers

 

[cliobritt]

lol np see you around.

 

[gooner182]

i dont care what it is,
man when it kicks in its awsome.

 

[C.slicker]

When someone who really knows what they are talking about comes into the thread can they also answer...

Does this happen on 1.2s as well? I can't feel it but theoretical should it happen?

 

[GR172]

The cam phase change is at 1800rpm IIRC and that's it, nothing else like vvt.

The cams get to their most efficient at around 5000rpm, but if you look at rolling road graphs, there's usually actually a dip in power just before it. This makes it feel like a bigger change than it actually is.

Lots of people seem to lose the "5K kick" after mods, probably because that little dip in power is improved.

 

[experi-mental 182]

its the vvt kicking in mate and the profile of the cam changing! so i believe anyway. the good old cliosport 5k kick

That's what it isn't, but most people think it is. VVT on the Clio only activates at low revs to assist with the idle from what I can remember.

Ben/Fred? Hurry up and give us the full answer. lol

Cams: http://auto.howstuffworks.com/camshaft.htm

So is it the VVT de-activating that causes this burst of power that causes small animals to be sucked into my pipercross induction filter at 5200rpm?

 

[Chris n nic]

IIRC the VVT is just at low rev/idle. Without this I think the idle would be quite lump due to the cams used.

I thought the kick at 5k was the vtec yo!

Chris

 

[Cookie]

It's magical engine pixies I tell thee

 

[Martin]

This should be a FAQ for ffs

 

[Rob Clark]

erm there is.......
Cant find it atm but im 99% sure its one of edde's posts which are stickied in this section or a link off it.

From mem VVT is active from ~1800RPM -7000 ish
the 4-5k kick is the cam profile changing to a more agressive one hence you feeling like knightrider pressing 'boost'

 

[Steve]

Thats when your binding brakes free off

 

[dick]

have any engines started having electronic actuators for valves yet?
because thats the next thing,
will allow engines to have just one cylinder firing on tickover as it uses not much power.

also, will give engines the best timing throughout the rev range.
i dont know if they use it on any top end cars yet, but will be happenning soon.

 

[LegoHead]

have any engines started having electronic actuators for valves yet?
because thats the next thing,
will allow engines to have just one cylinder firing on tickover as it uses not much power.

also, will give engines the best timing throughout the rev range.
i dont know if they use it on any top end cars yet, but will be happenning soon.

as far as in know alot of performance cars such as the m5/m6 do this.

 

[LegoHead]

what tyre pressures should i use......:dead:

what oil.....

what fuel.......

 

[dick]

yer thout it would be, when i learned about it, it was just a plan at the time.