- 249
I have a fully modded 2CV Turbo and it doesn"t have any lag at all.
So I found a car with worse turbo lag than the Chaparral when it has a stage 4 turbo
- Thread starter Boz Mon
- 47 comments
- 5,159 views
- 40,874
That could be anything from low power to a poor powerband. Not necessarily lag.
- 1,478
Did you try starting from a complete stop? Maybe mine is just a glitch then?
- 2,571
I am absolutely staggered by the number of people who do not know the difference between 'turbo lag' and 'boost threshold'. Arguing about something you do not understand against someone who clearly does understand it is not the most intelligent thing you can do with your time.
DE
DE
- 3,770
- Boss-Barracuda
I actually like the lag on the Escudo Dirt Trial car. It's great on the Test Track with Super-Soft tires, full power and minumum weight, in Arcade mode. It's excellent, you go quite slowly and then WHAM! Rocket boosters.
ya but its gets annoying when you accidentally hybrid a car with an escudo's turbo and have to put up with it around the complex string. going through the square corners is a pain, no power then wtf i'm off the track.
- 2,571
I refer to my post above - the poor powerband Toronado mentioned would be an overly high boost threshold, possible with a too-low boost cut-off as well - neither of these are 'turbo lag'.lmracer
Perhaps on the car you are talking about, it is turbo lag, but Toronado said that it 'That could be...a poor powerband'. If it is a poor powerband, then it is not lag - so your above post is incorrect.
DE
- 1,708
- Wisconsin
turbo lag = rpm range before turbo spools and makes power. if the engine makes 300 peak hp, but only %20 of that power is available until 3/4 of the total rpm range, that car suffers turbo lag. no matter what. how can you argue that?
- 2,571
Because it is wrong.
Turbo lag is the delay between depressing the throttle pedal more, and the turbo's output increasing accordingly.
The rev range before the turbo 'spools up' and increases engine power is referred to as the rev range below the boost threshold. This is not turbo lag.
DE
- 1,708
- Wisconsin
we are saying the exact same thing. you are just trying to complicate a simple answer with added jargon.
the following was taken from turbonation.com
this is consistant with any definition i can find on the net. in the nature of this thread no one cares about boost threshold. thats just the glorified volumetric capacity of the compressor.
the following was taken from turbonation.com
this is consistant with any definition i can find on the net. in the nature of this thread no one cares about boost threshold. thats just the glorified volumetric capacity of the compressor.
- 572
I have to back up DE on this one. Turbo lag refers to the phenomenon that occurs due to the time it takes the turbine to come up to speed.
With turbo lag what happens is this: you are cruising down the road at 4000RPM and floor the throttle - instantly you've opened the butterfly and told the fuel system to deliver a lot more - however, because you were travelling with a barely opened throttle there was very little exhaust speed/pressure so the turbo was turning maybe 40,000 RPM (these numbers are for illustration, I don't actually know how fast the turbo spins when lightly loaded) at which point it does almost nothing (and the engine is essentially naturally aspirated), but needs to be somewhere in the 100,000 to 150,000RPM range to pressurize the intake. And no matter how small or light the turbo is it will take some time to accelerate the impeller from 40k to 100k/150k - that is turbo lag. So you floor it at 4,000RPM and you have have let's say 150HP available, a half second passes, the turbo spools and now at 4,100RPM you have 300HP.
To put it another way - if you had been WOT from 1000RPM, at 400RPM the engine would already be producing its 300HP because the turbo would be spooled up.
To put it yet another way, a turbo'ed engine does not always produce the same power at a given RPM - it depends on how fast the impeller is spinning.
The effect that most people call turbo lag is simply the power curve of the engine where ther is relatively little power at low RPM and a massive increase as revs climb - but actually no different than a highly tuned 9,00RPM Honda engine that is anemic down low and very powerful near redline.
Hope this clears things up
With turbo lag what happens is this: you are cruising down the road at 4000RPM and floor the throttle - instantly you've opened the butterfly and told the fuel system to deliver a lot more - however, because you were travelling with a barely opened throttle there was very little exhaust speed/pressure so the turbo was turning maybe 40,000 RPM (these numbers are for illustration, I don't actually know how fast the turbo spins when lightly loaded) at which point it does almost nothing (and the engine is essentially naturally aspirated), but needs to be somewhere in the 100,000 to 150,000RPM range to pressurize the intake. And no matter how small or light the turbo is it will take some time to accelerate the impeller from 40k to 100k/150k - that is turbo lag. So you floor it at 4,000RPM and you have have let's say 150HP available, a half second passes, the turbo spools and now at 4,100RPM you have 300HP.
To put it another way - if you had been WOT from 1000RPM, at 400RPM the engine would already be producing its 300HP because the turbo would be spooled up.
To put it yet another way, a turbo'ed engine does not always produce the same power at a given RPM - it depends on how fast the impeller is spinning.
The effect that most people call turbo lag is simply the power curve of the engine where ther is relatively little power at low RPM and a massive increase as revs climb - but actually no different than a highly tuned 9,00RPM Honda engine that is anemic down low and very powerful near redline.
Hope this clears things up
- 1,708
- Wisconsin
there is no need for this detailed explanation. 2078TM, that is very insightful and true, you are properly stating the basic principal of all boosted engines. the engine tries harder to spool the turbo which essentially is exhaust resistance that the engine has to cope with. the lag that you are both describing, without going into technicalities, is turbo lag in its essence. i dont care about the engine's natural power curve. waiting for boost is turbo lag.
and because GT4 doesnt model boost pressure accurately, your argument is nullified.
and because GT4 doesnt model boost pressure accurately, your argument is nullified.
A garrett T88 turbo on a Nissan RB26DET(T) comes 'on boost' at around 5,500rpm, if I remember correctly. That means that it's boost threshold, the point at which it begins to make proper levels of boost, is at around that 5,500rpm mark. Anything below that is below the boost threshold of the turbo.
Now, if you put that T88 on a 7L V12, with much higher exhaust flow, the boost threshold of that turbo would probably drop down to somewhere in the 4,000rpm range. So the boost threshold is the point at which the engine makes enough exhaust flow to drive the turbo at full strength. Anything below that is not going to provide as much (if any) boost. Because highly boosted engines have low compression ratios and cam/injection/ignition setups for high boost, they have a noticeable lack of power/torque outside of the boost range. That is why turbo selection and engine tuning are critical. A smaller turbo will not produce as much boost - and hence top end power - but it will spool up earlier and provide better low/midrange power and torque.
This is the reasoning behind the sequential twin turbos of the RX-7. A small turbo gave boost at low/mid rpm, and then the system switched exhaust flow to the second, larger turbo at higher rpm.
Lag is the time it takes from opening the throttle to the turbo coming onto boost. Take that massive, blow-drier T88 Garrett again. Because it has a larger, heavier turbine/impellor, it takes more time to spool up from idle to boost speed than say a tiny Mitsubishi TD04. Turbo lag is about inertia and momentum of the turbo itself, while boost threshold is solely about exhaust flow to drive the turbo.
So after all that dead-horse-flogging, I would say that Dark Elite and 2078TM are 100% correct, and yes, it is important if you get into automotive stuff.
Whilst GT4 is just about stage 1 to 4 (and hybrid 5) turbos, it makes a difference. Where available I take the hybrid stage 5, because it gives better boost threshold and spool up (i.e. less lag), which I think is worth the slight loss of top end HP.
I don't know if calling the engine itself 'laggy' is correct or not... what's the correct terminology for a heavily boosted engine with no low/mid range power?
Now, if you put that T88 on a 7L V12, with much higher exhaust flow, the boost threshold of that turbo would probably drop down to somewhere in the 4,000rpm range. So the boost threshold is the point at which the engine makes enough exhaust flow to drive the turbo at full strength. Anything below that is not going to provide as much (if any) boost. Because highly boosted engines have low compression ratios and cam/injection/ignition setups for high boost, they have a noticeable lack of power/torque outside of the boost range. That is why turbo selection and engine tuning are critical. A smaller turbo will not produce as much boost - and hence top end power - but it will spool up earlier and provide better low/midrange power and torque.
This is the reasoning behind the sequential twin turbos of the RX-7. A small turbo gave boost at low/mid rpm, and then the system switched exhaust flow to the second, larger turbo at higher rpm.
Lag is the time it takes from opening the throttle to the turbo coming onto boost. Take that massive, blow-drier T88 Garrett again. Because it has a larger, heavier turbine/impellor, it takes more time to spool up from idle to boost speed than say a tiny Mitsubishi TD04. Turbo lag is about inertia and momentum of the turbo itself, while boost threshold is solely about exhaust flow to drive the turbo.
So after all that dead-horse-flogging, I would say that Dark Elite and 2078TM are 100% correct, and yes, it is important if you get into automotive stuff.
Whilst GT4 is just about stage 1 to 4 (and hybrid 5) turbos, it makes a difference. Where available I take the hybrid stage 5, because it gives better boost threshold and spool up (i.e. less lag), which I think is worth the slight loss of top end HP.
I don't know if calling the engine itself 'laggy' is correct or not... what's the correct terminology for a heavily boosted engine with no low/mid range power?
- 1,708
- Wisconsin
ok. i apologize to both DE and 2078TM. you guys are both very precise with your information. however this thread has become only us arguing. im suprised we have not been warned. this thread, if anyone has forgotten, is about finding a car in GT4 that is very laggy when it comes to turbocharging. all your logic does not apply to this case because GT4 is not modeled that accurately. look at the boost gauge for heavens sake. it hits full boost at any rpm, any engine. that is why im saying what i am. it seems the only way to describe that phenominon is turbo lag because none of those other factors are tangable
- 2,571
Thank you.
However, I must say that the poor modelling in GT4 does not mean you should rename real-life characteristics of turbocharged engines - after all, the terms were coined for real-life reference.
Leaving that behind...
The boost gauge in turbocharged cars in GT4 does not reach maximum boost immediately, if I recall correctly. Without doing any reference:
I haven't tested the latter theory, but it would be interesting to do so and see if GT4 does, in fact, model turbo lag.
Anyone testing it would have to bear in mind the different powerbands of different turbochargers, however, to ensure a fair test.
DE
However, I must say that the poor modelling in GT4 does not mean you should rename real-life characteristics of turbocharged engines - after all, the terms were coined for real-life reference.
Leaving that behind...
The boost gauge in turbocharged cars in GT4 does not reach maximum boost immediately, if I recall correctly. Without doing any reference:
- If the engine is below boost threshold, when the throttle is opened fully the boost gauge begins to rise slowly as the engine speed, and subsequently turbo speed, rise. This is GT4 modelling 'below boost threshold' behaviour.
- If the engine is well in the boost powerband with little or no throttle, when the throttle is opened the boost gauge moves quickly to maximum - not immediately. This, I assume, is GT4 modelling 'turbo lag' - the larger the turbo fitted, the slower the gauge should reach full boost in this situation.
I haven't tested the latter theory, but it would be interesting to do so and see if GT4 does, in fact, model turbo lag.
Anyone testing it would have to bear in mind the different powerbands of different turbochargers, however, to ensure a fair test.
DE
IIRC, boost will also fall off as you run up to redline - I noticed it mostly in the 787B, I think. You can see the boost gauge needle slowly drop away.
I find the lag/lack of low end grunt is most obvious in the smaller engines. The big guns don't tend to lose that much, but then they are powerful to begin with. PD have really reduced the turbo lag since the first and second games - I remember in GT1 having an STi type R with stage 4 turbo, and it took about six seconds to rev up to redline in neutral. Good whilst on the move, in the power band, bad if you spun out and lost rpm...
I find the lag/lack of low end grunt is most obvious in the smaller engines. The big guns don't tend to lose that much, but then they are powerful to begin with. PD have really reduced the turbo lag since the first and second games - I remember in GT1 having an STi type R with stage 4 turbo, and it took about six seconds to rev up to redline in neutral. Good whilst on the move, in the power band, bad if you spun out and lost rpm...
- 2,571
The inclusion of an accelerative G-counter would be the best way to see where the power really is.
I'd forgotten about the drop-off at higher revs, although now I think about it a few cars I've driven experience it at extreme revs - couldn't tell you which ones, though.
DE
I'd forgotten about the drop-off at higher revs, although now I think about it a few cars I've driven experience it at extreme revs - couldn't tell you which ones, though.
DE
