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[SKY 34]

I was trying out my 0-100km/hr speed.. I have Apexi RSM

so I rev the engine steping on the clutch till the blow off valve went off...to abt 6000rpm...did that three times..let the rev went down to abt 4000rpm before relasing my clutch and slam the accelerator...

that's when my problem came in...sometimes it immediately went in gear and start accelerating..however most of the time from 4000rpm as I step on the accelerator the car moves at a very slow speed, also the rpm drops a bit (although steping the accelerator full)...for 1-2 sec before the rpm starts to climb up and the car start accelerating properly

also at other times when I release the clutch, the rpm just shoots up to red line although the car barely moves.......I got like 8-10s time when this happens

does it mean I need to get a new clutch? or some other problem?

I also have really shit fuel consumption with that....like 350km just as the orange light went on..I ask the mechanics abt it and they cannot figure out the reason...

thanks

[Mulkers]

what car is this for?

[dezz]

if your sitting there revving to 6k then launching at 4500, chances are ur clutch is slipping lol, and 350km isnt bad economy if thats how u drive

[SKY 34]

it's r34 GTT.....no, did this very rarely....very very very...I didn't have mods on engine yet...

friend's gtt can do up to 450..I'm 100km short..

the second one..reve went up but car moving slowly..I think that's definitely clutch slip...but the 1st one I thought is a bit weird....

[dezz]

are u saying ur mates R34 GTT does 430km/h?

[SKY 34]

nop....his full tank can go for 450km ...mine only 350....

shitty fuel consumprion..what kind of a car go 430km/hr lol.....I'll be clearer next time..

fuel is quite okay...the clutch thingy ..I'm not even sure if it's clutch problem...

Edited January 1, 2006 by SKY 34

[Dingo]

I could be very wrong here but a blow off valve releases the built up pressure on the inlet manifold to help reduce any damage right. So whilst you rev it high and it releases all that pressure, on the way back down through the revs your not gonna be spooling up so when you do "launch" youll be on no boost so no big launch.........

[Ivan in Oz]

youll be on no boost so no big launch.........

Isn't this

Turbo LAG

That's why some go for less Boost

and more engine compression?

[Dingo]

That's why some go for less Boost

and more engine compression?

<{POST_SNAPBACK}>

The idea behind twin turbos was to eliminate lag (sequential that is)

well yeah, turbo lag.....Example you have to wait for the turbo to spool up to get your good speed. Where as a Supercharger is run off the engine and not the exhaust so you get no lag.

What i was getting at though is if the skyline creates boost at what was it 1800rpm?? And youve revv'd it up and the BOV has gone off, then you wont be spooling up if your just letting the revs drop. But if you have the revs sitting there then launch youll be launching whilst on boost, instead of comming down in no boost then launching.

If im wrong please correct me, because thats the only way Ill learn more.

Edited January 2, 2006 by Dingo

[SKY 34]

I thought the intension of reving is an attempt to remove turbo lag? so rev ---> generate exhaust---> the turbine spins faster---> more air suked in----> off I go...

I think unless all the air sucked in is completely vented from the BOV then chances are by reving will cause turbo to spool....so reducing lag slightly?

my boost gauge went over 0 at abt 2500rpm....

I'm not really sure what I'm atalking abt either...lol

[Dingo]

yeah okay ill try to put it more simpler from my point of view.

Just for this convo lets say that the turbo spools up at 2500rpm.

So you rev it to 2500rpm and hold it there as there is boost is being created. Therefore when you take off youll be taking off whilst boost is being generated resulting in a much better launch.

If you were to take off from idle it would not be creating boost so just imagine taking off from a normal 2.5litre engine car, but once you get to 2500rpm the turbine starts to spool creating boost forcing air into the engine making it go faster.

Now a BOV wasnt invented to "sound cool". When you rev your car up and you get boost it puts pressure on the inlet manifold which can be bad if its re-tained there for X amount of time. The BOV then vents the pressurised air so that there is minimal damage done. In rally cars you wont often hear a BOV because if they were to vent the pressuried air they would be back to square one and would have to generate it all back again making their cars slower etc etc.

now what I was saying was that If you rev'd it to 6500rpm and the BOV went off, then your boost has been released right? So when it comes back down to 2500rpm there is no boost, and it has to make more (Turbo Lag- Waiting for the turbo to spool up and kick in).........which takes time which kills your 0-100kmh times.

Turbo Lag Side Note For Dummies - Were you to race lets say a V8, they have large displacement and dont need to wait for a turbo to spool up to get going. Say you were racing a V8 they might get off the mark before you (if you wern't launching on boost) its the time that you wait for the turbo to spool up and kick in that is known as Turbo lag as the exhaust from your engine will only have enough force at 2500rpm to spin the turbine to create boost.

(Im sincerely not trying to sound like a know it all so if I come off that way........sorry)

Edited January 2, 2006 by Dingo