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Discussion Starter · #1 ·
Hi

Maybe it is a silly question but a never had a car whit turbo and now i just got my new SE mokka 1.7 CDTI 2WD.
. How you suppose to know when turbo is kick in ? Does the turbo activates after certain revs ? Because I can`t see any big difference, even if I pressing acceleration to the bottom , on lower or higher gear is the same. May that suggest it is a fault in the turbo system, or just that how the mokka is a bit lazy. Any replies will help. (before to go to the dealer and lock stupid)

Thanks
Dorel
 

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You do not say how many miles your engine has done..I had turbo lag until the engine had done a few miles about a 1000.
When the turbo kicks in on mine it puts me back in the seat and we are off.
I would say engine revs at about 1200 to 1500 rpm the turbo starts to boost the engine.
I am not expert,a few on this forum are so they will answer you.
 

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The 1.7cdti goes like stink so I'm surprised you say "is a bit lazy".

I suggest you ought to take it back to the dealer and get it checked out.
 

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Hi dorel. The turbo is active all of the time but the boost it producesis more noticeable as the revs get higher. However, on a 1.7 diesel engine tuned for economy and low down powerI would suggest you are not going to notice much of the "turbo kicking in" - which generally describes the point at which the turbo starts to make a noticeable difference after the "turbo lag" - the pause between putting your foot down and the exhaust gasses spinning the turbo up to produce moreboost. On a highly tuned petrol turbo engine producing far more "top end"power the turbo willnoticeably kickin with a big push in the back. The wifes 1.7D Tech Line does not have any noticeable point at which the turbo suddenly propels you forward at a much greater rate so I wouldn`t worry that there is any problem with yours. Wayne.
 

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The power band on the 1.7 diesel is quite narrow. Mine starts to wake up at 1500rpm and maximum acceleration occurs between 2000 - 3000rpm. I certainly notice the surge when hard acceleration is requested between these thresholds. I always ensure that I am sitting on at least 2000rpm when overtaking as I know that I will have maximum power available should I need it.
 

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Stick it in 5th at 1000rpm on a flat clear road and put your foot to the floor; you'll notice it has barely any performance at all and this is when you are below the turbo's threshold (not to be confused with lag); at this point there is insufficient exhaust gas to effectively spin the turbo; eventually you will notice an increasing 'swell' of torque start to accelerate you at which point the turbo is now effectively working. It's not like the old days when there was nothing...nothing...turbo...bent drive shafts - I'm sure the CTDi has a variable geometry turbo which changes the vanes on the turbo so that it is shallower at lower revs (allowing less air to make he turbo operate) and sharper at higher revs (allowing more punch). Lag is the difference between putting your foot down at an engine speed the turbo can operate at and it starting to operate; most modern cars lack this as a) turbos are smaller or b) have variable geometry which means they need less pressure again before spooling-up.

With a variable geometry turbo it's essential to give it a regular Italian Tune Up otherwise the vanes rarely change profile and either fail solid (not the end of the world, needs a turbo replacement or overhaul) or snap (bit of metal flies into engine intake - there's only one outcome from that...)
 

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theforestdweller said:
The power band on the 1.7 diesel is quite narrow. Mine starts to wake up at 1500rpm and maximum acceleration occurs between 2000 - 3000rpm. I certainly notice the surge when hard acceleration is requested between these thresholds. I always ensure that I am sitting on at least 2000rpm when overtaking as I know that I will have maximum power available should I need it.

You are quiteright as the Spec for my 1.7 diesel, albeit the 4x4 version withthe same engine, shows the peak power being produced at between 2000rpm and 2500rpm. So it will build torque as it heads towards it's peak but a 0-60 of over 10 seconds will never set your hair on fire.1686cc 16v four-cylinder turbo diesel 128bhp @ 4000rpm 221lb ft @ 2000-2500rpmSix-speed manual, four-wheel drivePerformance: 0-60mph
10.4 sec The ideal torque curve for a performance carhas a quick rise to it's peak and then a long plateau at maximum torque before making a steady drop. The longer the plateau the longer you can hold it in each gear making for better 0-60 times bynot having to constantlywork the gearbox to keep it in the sweet spot. My old Subaru onlyhad a 0-60 of around 4.5 sec and a sub 13 sec1/4 mile but it was running a relatively low 290bhp. It had a nice flat top torque curve though after a remap and maximum power was reached well belowthe red line at 7000rpm.
 

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MaidofKent said:
What is a regular Italian tune up? Foot down and a bit of wellie?
Exactly that!

It's a big debate but a torque plateau like table mountain isn't necessarily the 'best' type of torque curve unless your driving style is 'what's that stick inbetween the seats, no need to use it when overtaking'; power is an output calculation of torque multiplied by engine speed so a 'crescendo' is best if you like to use the engine, ideally with something at low-medium engine speeds rather than always having to get to 5000rpm before anything happens. A turbo naturally boosts torque lower down the engine speed range but typically (on petrol cars) at the lack of top-end response (I exclude diesels from that comment as they never had it, even without a turbo...). Turbo's are also useful at hiding how fat our cars have become... Edited by: Frank Bullitt
 

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Discussion Starter · #12 ·
I have managed to fill when the turbo kicks on in 2/3/4 gears around 1600 revs with gas pedal fully down after couple of seconds. Still now luck in 5 and 6. I have reached 85 miles only maybe it happens after 85
, but in this case I will need to leave my wife on the hard shoulder
(or at home).

Dorel
 

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Frank Bullitt said:
It's a big debate but a torque plateau like table mountain isn't necessarily the 'best' type of torque curve unless your driving style is 'what's that stick inbetween the seats, no need to use it when overtaking'; power is an output calculation of torque multiplied by engine speed so a 'crescendo' is best if you like to use the engine, ideally with something at low-medium engine speeds rather than always having to get to 5000rpm before anything happens. A turbo naturally boosts torque lower down the engine speed range but typically (on petrol cars) at the lack of top-end response (I exclude diesels from that comment as they never had it, even without a turbo...). Turbo's are also useful at hiding how fat our cars have become...

On track I found a wide rev range of maximum torque is far easier to manage than a quick blip where you can fall in and out of the sweet spot too easily and then bog down when you change gear before the torque builds again. It gives far more flexibility when approaching a corner not having to change gear because the crescendo has peaked prematurely and the torque has dropped off a cliff.A plateau like torque curvedoesn't mean it doesn't rise to a crescendo it just means once it has it can hold it longerbefore dropping off.Givingyou a chance tosnick the next gear and still have a good gob of torque tolaunch youtowards the next apex.

If you look at my dyno read out you can see it takes just 1000rpm forthe torque torise from 160 lb·ft to 290 lb·ft and then holds peak torque from 4000 revsto 5500 revs before dropping off whilst the power is still climbing to peak at 6000rpm. In the car that equates to a head snapping acceleration, the crescendo you talk about,from 0-60 using only 1st and 2nd gear and rather than revving the nuts off it youjust change up at 5500rpm and are still in the power band as the revs drop. My shift light was set at 5000rpm and on a good dayI would change gearby 5500rpm.

I saw some huge torque and power figures on Skylines but as for driveability they were sadly lacking due to the peaky nature of their torque delivery.However much you like to use the engine if you change gear and drop out ofthe power band because it is so narrow you are dead in the water till it builds again.

Your mention of nothaving to get to 5000rpm before anything happens makes me think of the Honda VTEC engines.They were non turbo andthe engine wouldn'tcome aliveuntil 5500rpm and thenscream on to 8000rpm. You could not help but rag it everywhere to get anything out of it. Played havoc with the mpg figures but sounded nice.
 

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Hi

Maybe it is a silly question but a never had a car whit turbo and now i just got my new SE mokka 1.7 CDTI 2WD.
. How you suppose to know when turbo is kick in ? Does the turbo activates after certain revs ? Because I can`t see any big difference, even if I pressing acceleration to the bottom , on lower or higher gear is the same. May that suggest it is a fault in the turbo system, or just that how the mokka is a bit lazy. Any replies will help. (before to go to the dealer and lock stupid)

Thanks
Dorel
Not a silly question I have similar. Having just bought aMokka X I find the turbo cuts in very sharply but unless you keep the revs up it drops off just as quick. Makes smooth overtaking a bit difficult. I've had other turbo cars and expected the Mokka turbo to integrate better.
 
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