why can't the devs get the powerband right?

[Silvia95]

I sure hope that it's in. I always wondered why GT3 was like that.

 

[SchuberT]

I have a theory that turbo lag exists in GT3 as well. It just isn't so obvious. Today I bought an Alto Works and figured it'd be fun to drift. I bought everything for it including the stage 2 or 3 turbo (forgot which one is the highest). I noticed that from a stopped position, it took about 5 seconds for ANYTHING to happen, and 3 more for it to rev up to 2k RPMs... When I went to the lower level turbos the effect decreased only slightly until I took the turbos off completely.

Before I realized it was the turbo I had tried dealing with everything pertaining to the gearbox, to no avail.

 

[Gabkicks]

yeah i just did the "top gear TV show" test for turbo lag, and there is some, So GT3's turbo lag doesnt seem too bad by those standards with the cars i tested.

 

[Div is back]

From the sounds I heard, turbo sounds are back in force just like in GT2.

 

[Silvia95]

From the sounds I heard, turbo sounds are back in force just like in GT2.

I really hope we can hear it outside the car too. Thats something I really hated with GT3. The only time you can hear it is inside and if you don't buy the after market transmission, you can hear it better.

 

[KSaiyu]

I have GT4 now...
I'm happy to see that modifications are realistic again
I put a stage 1 turbo only on my Fiat Panda and torque at lower revs slightly decreased. Even the reference manual mentions about this happening with modifications. Very good!

So wait, do turbos actually decrease stock low end torque figures, or do they just narrow the cars powerband? Kinda OT, but how is it possible for a turbo to make an engine lose torque - does it restrict airflow at lower speeds or something?

 

[Eric.]

So wait, do turbos actually decrease stock low end torque figures, or do they just narrow the cars powerband? Kinda OT, but how is it possible for a turbo to make an engine lose torque - does it restrict airflow at lower speeds or something?

Well, the stock one is designed to produce boost at lower RPM's, while higher stage turbos are made for high-end power, so higher RPM for the boost.

Someone else may be able to explain better...I'm hardly an expert.

 

[LFRANCOF483]

I dunno. My old 90 Civic DX sedan could spin 'em up quite nicely from ~2000 RPM. Considering the monstrous () low-end torque of a stock D15B2...

you have to consider the factors, my rear tires are 245's, the front tires on your civic are probably at the most 185's....also keep in mind the weight shift, as you accelerate, weight shifts back, causing you to lose traction in thefront making your tires spin, a RWD car actually gains traction due to this weight shift....also other things like differentials, gears, weight, etc....has a lot to do with this scenario

 

[Buck-O]

So wait, do turbos actually decrease stock low end torque figures, or do they just narrow the cars powerband? Kinda OT, but how is it possible for a turbo to make an engine lose torque - does it restrict airflow at lower speeds or something?

THere are so many cariables in this type of question its insane.

For one it depends greatly on the compresion ratio of the enginein question. That can change a hudge number of paramters in that single number alone.

On the turbo side, there is tons of varibles. From efficiency, to volume, to scroll type, to size, and even to the manifold its bolted to.


So, to answer your question in a simple answer....YES.
A Turbo can actually decrease the lower RPM performance of an engine.


FOr example, lets say you have an EVO.

If you have a small, quick spooling turbo, with a high boost, low CFM output. You will get high low RPM torque, punchy midrange, and you will fall off alot at higher RPM's.

If you have a large, high CFM, high boost, high volume, difficult to spool turbo, your low end torque, will greatly suffer becuase the engines low compression ratio will not have enough air, or compensated "seen" compresion ratio to be efficient enough to produce power. And the engine will lag, until enough RPM is reached, with enough load to produce adiquate exaust manifold pressue to create boost.

In this setup, the smaller turbo would be much faster at acceleration, and likely produce a much higher torque number then the larger turbo, which would produce a much higher HP number at higher RPM's.


Now, in the world of rallying, they combat all of these problems by compromising in the middle as much as possible. Useing turbos with twin scroll turbines, and trimmed impellers to produce high boost at low RPM, and high CFM with sustainable boost levels at high RPM, and useing water injection to squeeze out that little bit more power.


THats probibly more info then you wanted.

But the answer is yes. Becuase EVERYTHING in an engine is a compromise.

 

[sgtstix]

ok ponder this my friend in florida had a 1988 ford thunderbird turbo coupe
4 cyl 2.3 ltr e.f.i. engine bought the car for 500 bucks and that car screemed down the street plus it was rear wheel drive so donuts in a parking lot where easy also we decided to go visit his mother in jacksonville florida while we lived in fort myers florida and if u look it up its about 6 hrs away doing 70 mph but we did 90 mph most of the way so we did the trip in about 4 hrs. this car had a 5 speed manual tranny.

we researched this car on line cause we where impressed with this car so much we looked up the stats it had 190 hp stock

ok so we put in high octane fuel in this car before the trip to jacksonville and set of

my friend hit 90 mph and set the cruise control and the revs where about 2900-3000
rpm and the turbo gage was at 0 and it went to 15 psi so no torque at low rpms dont apply to this car plus each cylynder had 150 psi or about 150 or maby 170 i cant remember.

put it this way he could burn the tires on this thing without even trying plus on road trips it was fine and cruising dont use the turbo. plus we tested this many times from a stand still at a light we would take of as fast as we could when we got into 3rd gear when the rpms where below 3000 the turbo was at 11 psi and at about 3200 rpm it would shoot up to 15 psi 18psi was in the red it didnt go there. we where very impressed with the cars performance.

i think turbo lag is to do with the cars engine.

if u put a huge turbo on a small compact car there will be turbo lag cause a compact car doesnt have high compression cylynders cause it fuel efficient so it takes longer to spool up the turbo so if u put a turbo on a vette for instence and u floor it ull get no turbo lag or very little.


sorry i went on there a little

 

[KSaiyu]

THere are so many cariables in this type of question its insane.

For one it depends greatly on the compresion ratio of the enginein question. That can change a hudge number of paramters in that single number alone.

On the turbo side, there is tons of varibles. From efficiency, to volume, to scroll type, to size, and even to the manifold its bolted to.


So, to answer your question in a simple answer....YES.
A Turbo can actually decrease the lower RPM performance of an engine.


FOr example, lets say you have an EVO.

If you have a small, quick spooling turbo, with a high boost, low CFM output. You will get high low RPM torque, punchy midrange, and you will fall off alot at higher RPM's.

If you have a large, high CFM, high boost, high volume, difficult to spool turbo, your low end torque, will greatly suffer becuase the engines low compression ratio will not have enough air, or compensated "seen" compresion ratio to be efficient enough to produce power. And the engine will lag, until enough RPM is reached, with enough load to produce adiquate exaust manifold pressue to create boost.

In this setup, the smaller turbo would be much faster at acceleration, and likely produce a much higher torque number then the larger turbo, which would produce a much higher HP number at higher RPM's.


Now, in the world of rallying, they combat all of these problems by compromising in the middle as much as possible. Useing turbos with twin scroll turbines, and trimmed impellers to produce high boost at low RPM, and high CFM with sustainable boost levels at high RPM, and useing water injection to squeeze out that little bit more power.


THats probibly more info then you wanted.

But the answer is yes. Becuase EVERYTHING in an engine is a compromise.

This is what I don't get though - wouldn't the CFM at low revs at least remain the same after you fitted a large turbo? How can it negatively change the torque an engine produces?

 

[zefff]

"wouldn't the CFM at low revs at least remain the same after you fitted a large turbo? How can it negatively change the torque an engine produces?"

go and ask at a proper car forum.

I dont know much but I do know that engines with turbos run with lower compression. Why Im not exactly sure but Turbos are not indestructable and neither are engines and gaskets. With turbos comes great exhaust flow pressures and heat which needs to be taken into account.

"if u put a huge turbo on a small compact car there will be turbo lag cause a compact car doesnt have high compression cylynders cause it fuel efficient so it takes longer to spool up the turbo so if u put a turbo on a vette for instence and u floor it ull get no turbo lag or very little."

Thats not true, You still have lag you just dont notice it.

"Now, in the world of rallying, they combat all of these problems by compromising in the middle as much as possible. Useing turbos with twin scroll turbines, and trimmed impellers to produce high boost at low RPM, and high CFM with sustainable boost levels at high RPM, and useing water injection to squeeze out that little bit more power."

The most decisive factor is the use of anti-lag systems where the exhaust gases are rerouted back through the turbo to keep it spooling whenever the driver comes of the accelerator. So boost is always being made...this isnt good for turbo's but who cares if you only have to drive a stage or two before fitting a new part.

 

[barmyclown]

at the end of the day it doesn`t really matter, because gran Tourismo is a race game, so if you driving round with the revs low enough that you have bogged down in lag hell maybe you should think about superchargers rather than turbo chargers. The power band on most of these cars is wide enough in standard tune that you can still change gear well short of maximum power and still not suffer lag because the rpm drop between gears is quite small in comparison between 500 and 1500 rpm depending on the gear. And there is is nothing worst than sitting at the line of the traffic light gran prix with 4wd turbo charged rocketship bogged down cos you bought the clutch up to early and you can see a 1ltr fiat panda getting away from you. Then you look a tit as it takes off when it all comes on boost 2 seconds later.

 

[zefff]

Barmyclown what the hell are you talking about? That is a load of rubbish but u r right, GT is only a game.

 

[Buck-O]

This is what I don't get though - wouldn't the CFM at low revs at least remain the same after you fitted a large turbo? How can it negatively change the torque an engine produces?

CFM = Cubic Feet per Minute
Which is the volume of air that it is able to move.

Boost = the amount of manifold pressure that is able to be generated.

One does not dictate the other. But both are needed.

Most all turbo charged engines have their internal compression ratios lowered from a standared Naturally Asperated engine. This allows for more cylinder air volume to help with the fuel mixture, and allows for the handling of boost pressure.


Lets say that an engine runs at 8.5:1 compression ratio in the cylinder. When you add a turbo, and put boost to it, the effective "seen" compresion ration on the engine is up around 12:1.

Untill that engine sees boost, the engine slugs. Then once the turbo gets enough RPM to generate positive boost, the engine comes alive.

Now, you can have to much CFM, and to much Boost.
If you have to much CFM your not able to generate enough boost.
And if you ahve to much boost, you can actually choke out the air, and cause a really bad run rich situation. But it can be countered with water injection to help increase the density of the air in the cylinder. But thats way out there for what you need to know.


Now if you have a standard engine, and you add a turbo to it.
It can definatly kill the performance. Becuase the turbo will choke the engine on both ends.

It will restrict the free flow of exaust gasses on the exaust side. And on the intake side it acts as a restroctor.

Its not untill the turbo actually spools up to the point that it begins to build positive pressure that the engine gets more power. And the turbo still has to reach 0 efficieny to be able to produce the same amount of power as before its instalation. And even then, if the turbo isnt producing enough CFM, you will overboost the engine, and kill it quick. Usually the case on ricerboys with big turbos on civics.

There are dozens of variables in turbo setup.


But like i siad before. THe genreal answer to your question is...yes. A turbo can cause lower performance on an engine not designed for a turbo, when the turbo is not forcing positive pressure.

 

[Buck-O]

at the end of the day it doesn`t really matter, because gran Tourismo is a race game, so if you driving round with the revs low enough that you have bogged down in lag hell maybe you should think about superchargers rather than turbo chargers. The power band on most of these cars is wide enough in standard tune that you can still change gear well short of maximum power and still not suffer lag because the rpm drop between gears is quite small in comparison between 500 and 1500 rpm depending on the gear. And there is is nothing worst than sitting at the line of the traffic light gran prix with 4wd turbo charged rocketship bogged down cos you bought the clutch up to early and you can see a 1ltr fiat panda getting away from you. Then you look a tit as it takes off when it all comes on boost 2 seconds later.

If you know what kind of car your buying, and know how to drive it, and quit watching Top Gear all the time and believing everything out of Jeremy Clarksons mouth....none of this would be a problem.

 

[barmyclown]

I do know what car i`ve got and i`m speaking from experiance i`m not super human I can`t launch perfectly every time. The main reason for this is I expect my clutch to last more than 10,000 miles so in being sympathetic to the car you need to take the chance that you could get bogged down when you try and launch from a set of lights. and the 5000rpm and sidestep the clutch method is a good way of destroying the gearbox as the weakest link in the transmission is 1st gear, as in it will destroy first before it spins the wheels. an extract from martin brundell about driving turbo charged sports cars, " you take chances you wouldn`t take in an NA car, because to back off means you lose boost." So if you are in the position that your are suffering lag in gran tourismo you obviusly ain`t trying hard enough. Or don`t know how to drive a highly tuned turbo charged racecar.