172 varible cam timing info

[hamloin]

hi iv just got a 172 engine for me 5. now i dont know what to do about the timing, i have mega squirt so can probably work out how to control it.

What i need to know is, is it just a on/off 12v power supply which swithes it ?
At what revs does it change?
has anyone got rid of it or just set it at full advance?

 

[keirravn]

someone more knowledgebale (who can spell) will no doubt give you an accurate answer, all i can give ya is it seems to be around 4500 revs that it kicks in, good luck with the 5 project mate!

 

[sideways danny]

it's just a switch. Normally activated at around 1600-1800rpm, and de-activated above roughly 6500rpm

 

[sideways danny]

someone more knowledgebale (who can spell) will no doubt give you an accurate answer, all i can give ya is it seems to be around 4500 revs that it kicks in, good luck with the 5 project mate!

nothing to do with VVT

 

[hamloin]

So if i hit it with a ignition live will it just be advanced all the time? smooth running aint a priority its a rally car. thanks for your help

 

[keirravn]

nothing to do with VVT

care to explain before i embaress myself in another thread at some point lol?

 

[hamloin]

it aint variable valve timing. i.e. v tec. the 4500 boost u feal is the just the engine coming into its own, my willy engine takes off at 4000, it changes tone and starts pullimg like a beast. however the f4r is a better engine and pulls harder

 

[The Boosh!]

The VVT system is only active after certain conditions are met, like coolant temperature / battery voltage etc.
Once these conditions are met , the ECU looks up engine load and rpm in a 3D table and activates/deactivates the cam shifter accordingly.

For the 182 that means VVT is active from 1450 to 6850 rpm and from light/moderate load to full load.
The 172 shifts back 150 rpm earlier. All settings can be changed as required.

As most of you know the VVT is a 2-step ON/OFF system. However the ECU is capable of sending a PWM signal which turns the solenoid on/off in 6 steps. From 25 - 100 % duty. Renault does for some reason, NOT implement this feature on the 2000-2005 models.

....

Tried finding BenR's post on this subject also to no avail.

 

[Tom@JMS]

The fabled 5k kick is due to a number of factors, the primary one being the efficiency of the manifold at that specific rpm. (Resonance of gas pressure waves etc.)

 

[Jonny1*2]

I thought the "5k kick" was due to the dephaser changing the cam angle, causing a more aggressive profile?

 

[Ian_s]

I thought the "5k kick" was due to the dephaser changing the cam angle, causing a more aggressive profile?

Did you not read any of the thread? :S

Its the RPM at which runner length, manifold design, cam timing etc all add up to produce the best volumetric efficiency. Some engines have a variable runner length so this can be achieved over a wider engine speed range.

 

[sideways danny]

It's emissions restriction!!!!!!!!!!!!!!!!!!!!!!!!!!!! acceleration fueling is heavily restriced by euro4 emissions regulations. That's why the "kick" can be mapped out by giving it the fueling it really wants

 

[Russ_16v]

I always thought it was a the Vtec Y0

 

[Jonny1*2]

I always thought it was a the Vtec Y0

Don't start

 

[keirravn]

I always thought it was a the Vtec Y0

me too

cheers for the education gents

 

[sideways danny]

it aint variable valve timing. i.e. v tec.

think this post has confused it even more lol

v-tec ISN'T variable valve timing, it's variable valve lift

What the F4R has IS variable valve timing (VVT) which operates to give a better idle. Above a given rpm (1400-1800, not massively important exactly when) the VVT is activated to bring the cam into phase. Now depending on the cam profile being used, it can be beneficial to change at the top end of the revs that the vvt is de-activated again.

Later engines (197/200) use fully variable cam timing so it can be optimised throughout the rev range, but the 172/182 just uses an on/off switch.

 

[hamloin]

so is positive advanced or retarded????? thanks