Difference VTEC Sohc & Dohc

[Thug]

Its unavoidable to get knocking after skimming?

I'm experiencing ping. Now after using ron 98 and retarted my ignition timing, it decreases...

 

If it continues, one of these day the engine going to piang....how to totally solve the problem?

[Mcff_1980]

No my parents taught me that those who dunno anything but want to hao lian should be taught.

 

and to forgive those who scold other pple parents cos most likely they got fingered by their dad when their young thus making their arse a big one.

 

now who is one who started the haolian sh1t by calling others idiots.

 

nvm forget it, dont come here and talk mother talk father with me. my english is not as powderful as u but i am not impress at all

 

u wan to be YAYA, good

 

1.59min PG, good!

 

PUT TIME AND DATE - PASIR GUDANG

 

USE YOUR OWN CAR

 

if u lose, post it here, very simple

[Mirrorimage]

So typical of a non educated ah beng asking pple out for a confrontation.

 

The beauty of a forum is that I can just be a armchair racer and make your blood boil while u cant do anything abt it and just go home crying to your mommy.

 

Anyway I started replying to someone else, you were being a busybody and sticked your nose in.

[Mcff_1980]

well what can i say?

 

just another COMPUTER HERO

 

1.59 not fast enough to be COMPUTER HERO, why not claim 1.30min ??

 

practice somemore maybe u can really achieve 1.30min on your PLAYSTATION! then u can come and update your signature.

 

thats what COMPUTER HEROS are good at isnt it?

 

shall not be bothered with u anymore.

 

bye!

[Mirrorimage]

Bye! Hope your B20 dont piang on the track.

 

Have a nice day!

[Mirrorimage]

An example of Vtec Killer cams. These cams are meant for high revs, single lobe. No Vtec point.

 

See how the idling goes.

 

But at 10000 RPM...things are a little different

 

http://www.youtube.com/watch?v=dHVCyj4GqPo&NR=1

[Thug]

Wad the hell is that sound?

Like something going to piang..........

[Thug]

actually i had my engine....redone...

everything inside is stock...jus the skimming part...

with hotbits 4-2-1 & supersprint...everything else i would say pretty much stock...

 

i wouldn't say my blasting off time is good, but its decent enough...i'm quite happy with my high end though...

but I just can't get it through 180km/h....it seems to stuck...there.....

 

then a close buddy of mine told me the other day he shocked wad he see on the speedometer of his Lancer GLX...200km/h....

I tot to myself....is it possible???

 

I'm not looking down on GLX...but as compared to Vtec...its inferior...but if the speed he mentioned is real.......then why...why...why????

haha...can't get over it...

[Mirrorimage]

err...ok. hope u can digest this long post.

 

I am gonna explain abit about NA performance at high RPMs.

 

Typically for a NA car, Cam durations are used to extract more power. How so?

 

For a normal intake and exhaust procedure. The exhuast valve is closed, The intake valve opens to take in air. the intake valve closes. Combustion happens and then Exhaust valve opens to release the Exhaust.

 

So for NA cars, at high RPMs, there is a slight over lapping of the opening and closing of both Valves...imagine 8000 RPM. There equates to abt 134 RP(Sec).

 

This overlapping at high RPMs is a good thing as the action of drawing out the Exhaust gases creates a stronger vaccum and draws in the air from the Intake valves at a stronger rate than as compared to low RPMS.

 

So engineers try to find an optimum cam duration at high RPM for good power. However, there was a draw back, at low RPMs, the engine idling is very unstable cos the air coming in is like drawn out immediately. Hence this is what u see in the Vid....the engine is like dying already. losing RPM cos it cannot really combust properly with such aggressive Cam durations. Also typically such Killer Cams only start making decent power 6000 RPM thereabouts and above. Making it a real pain in the ass to drive everyday.

 

What Honda did was made a compromise and created two cam lobes. One for low end and one for high end, which we find in their Vtec engines.

 

Hope you understand!

[Thug]

I see...trying to digest..haa

Actually I know how it goes...saw a video about it.

However, right now I'm more interested in knowing the source of my problem wif my ride...

 

Since the last engine to this new one, I have this common problem...sometimes with air-con on, my idling goes to 600 plus making the car vibrate very very jia lat....then slowly it will climb back to 750-850....then after awhile...it go down 600 plus again...repeating...

 

Sometimes....when travelling...then coming to red light...i clutch in and the rpm drop relatively fast and straight to 600 plus...sometime...with the clutch still in, it die engine....*faint...pple will think i'm new-bie...haha

 

Anyway, since the last engine the same problem. Hence I think not about the engine...the only thing i din change is trottle body...

Could it be the problem?

[Mirrorimage]

Which workshop u normally go to?

 

That could range from a variety of reasons. Idling valve, or the TB really too big or got leak....do u have a piggyback to tune?

[Thug]

VAFC2...I always go Ubi...blk 53

[Dynaway]

Its unavoidable to get knocking after skimming?

I'm experiencing ping. Now after using ron 98 and retarted my ignition timing, it decreases...

 

If it continues, one of these day the engine going to piang....how to totally solve the problem?

 

i guess ur CR may have been raised too high.... u can try a piggyback ecu wif ignition control to alter the timing.... may help solve the problem.

[Thug]

Arrr...spend again....

I think I'll just skip that..

going to scrap the ride next year...

so..i thin i'll jus feeding it wif good petrol and act blur about the pinging...

[Mcff_1980]

bro did u ever go and bore your trottle body?

[Dynaway]

i have to disagree with some of ur points...

 

theoretically the exhaust valve is open only after the intake valve closes.... but in practical, tat does not happens.... u still need overlapping of valves to create drafting of the intake air.

 

valve overlapping occurs all the time even in low rpm range, duration of the overlapping depedant on the cam lobe/profile design.

 

if the overlaps are extended, logically there will be a better scavenging of exhaust air, more air/fuel are drafted into the combustion chamber n some will actually leak out together with the exhaust gases.... however there is a cut-off limit as to how much it can be extended..... u may face "compress leak" n instead looses power at the end.

 

this is one reason why most race cam will require the adjustable cam gear/sprocket for fine tuning.

 

if u want to play with overlaps, u will also need to special tune the exhaust header... this will be good if u can do an echo pulse tuning

[Thug]

Yes...in fact things start to have problem after the trottle boring....

[Turbonetics]

actually i had my engine....redone...

everything inside is stock...jus the skimming part...

with hotbits 4-2-1 & supersprint...everything else i would say pretty much stock...

 

i wouldn't say my blasting off time is good, but its decent enough...i'm quite happy with my high end though...

but I just can't get it through 180km/h....it seems to stuck...there.....

 

then a close buddy of mine told me the other day he shocked wad he see on the speedometer of his Lancer GLX...200km/h....

I tot to myself....is it possible???

 

I'm not looking down on GLX...but as compared to Vtec...its inferior...but if the speed he mentioned is real.......then why...why...why????

haha...can't get over it...

 

if iam not wrong,Lancer does not have speed cut.

you can remove the speed limit.