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Old 5th March 2008, 23:14   #1
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Default TURBO Confusion

Hi Guys!
I am a little confused about the factory fitted Turbo which comes in diesel engines (Swift 1.3 Multijet, Indica Turbo V2, Scorpio etc).
*Are these turbos "Soft Turbos"? i.e they are electronically limited to a particular boost range(eg. 5-7psi or lesser) which is a compromise between economy and power.
*If the above is answered "YES" then can the stock ECU be remapped for a higher boost range(eg.7-9psi or more) or a stand alone one would be required.
*Can the factory fitted Turbo be replaced by an after market turbo.(brands like Garett etc.)
*Are turbos used for petrol engines the same as the ones in diesel, i understand that their operation is based on the same principles of induction.
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Old 6th March 2008, 00:21   #2
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interesting,would like to know myself aswel,all the techies out there,shed some light please..cheers..happy revvin..!
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Old 6th March 2008, 02:39   #3
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Originally Posted by abhik View Post
Hi Guys!
I am a little confused about the factory fitted Turbo which comes in diesel engines (Swift 1.3 Multijet, Indica Turbo V2, Scorpio etc).
*Are these turbos "Soft Turbos"? i.e they are electronically limited to a particular boost range(eg. 5-7psi or lesser) which is a compromise between economy and power.
*If the above is answered "YES" then can the stock ECU be remapped for a higher boost range(eg.7-9psi or more) or a stand alone one would be required.
*Can the factory fitted Turbo be replaced by an after market turbo.(brands like Garett etc.)
*Are turbos used for petrol engines the same as the ones in diesel, i understand that their operation is based on the same principles of induction.
I'm not sure what "Soft Turbo" means, but I'll give a little explanation of how boost is regulated in general. The turbos boost is regulated by the wastegate. That wastegate is controlled generally by a solenoid or some sort of boost control device(via a vacuum source). These can be a manual process or electronic controlled by either the user or the ECU etc.

So in theory, yes, you should be able to up the boost and remap your tune to make more power. However just about every car/manufacturer controls boost in a different way, so you have to figure out the system being used on your particular car and then we can find the best solution to upping the boost and retuning to compensate. In general, you would be disconnection the way the manufacturer controls boost and would be controlling it yourself. Unless you are able to make that change in the stock ECU and have it accept the change.

And yes, any/all turbos can be replaced with another. However, availability of turbos that will fit your stock manifold depends on the flange style being used on your car. In general, most people will have a new manifold made, in which case you can use whatever turbo/flange you would like. In this case, all new intake piping, intercooler piping, and downpipe piping would have to be fabricated as well.

And yes, diesel and gas/petrol turbos function the same way and are technically interchangeable. However, they can have some differences in build strategy. Some of the diesel turbos are build more sturdy for higher pressure situations and can handle higher boost thresholds(like 60 - 80 lbs of boost in very extreme setups). For lower power applications, turbos designed for diesels may not be the ideal setup for a gas/petrol car not looking for high hp/boost levels(which need a stronger turbo which can take the abuse, I'm talking over 40psi etc), as the shaft and components are generally heavier and could/would affect spool up(slower).

I hope this makes sense, if not, just ask me to clarify whatever is not clear.
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Old 6th March 2008, 10:04   #4
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the term "soft turbo" is related to the use of turbo with very low boost , it is mainly when a turbo charger is used without an intercooler [ like in the tevera, seina ,old trax].
The turbos on most of the Indian cars have mechanical wastgates [spring loaded for boost control] so that there is no over boost. they can be changed to any brand with proper engineering nohow, they should match the engine properly. one can use electronic boost controller for the turbos but ,these are mainly used where the engine can handle overboost with out destroying itself, so the scorpio and other cars mention by abhik should be that well engineered and also the clutch,gearbox and diff have be be able to handle the increase in power....
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Old 6th March 2008, 10:18   #5
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But there is a vacuum line attached to the wastegate actuator correct? From the sounds of it, it is a normal wastegate. There are internal wastegates and external wastegates. Most stock turbo applications have internal wastegates and have an actuator and a vacuum line attached to it. Upstream the vacuum line is attached to the boost control device(whichever style is used). And from there the boost control device is sourcing vacuum/boost probably from somewhere on the intake manifold.

No car can handle "over boost", otherwise known as boost spikes. All cars need to be tuned for the boost levels they are running, thus the need for boost control/wastegates etc. Same goes for the clutch/gearbox etc, that applies to all cars.
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Old 6th March 2008, 10:34   #6
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Most turbos can support more than 5psi of boost. Excess boost could cause over heating and will need to be controlled using the intercooler and the wastegate ensures that the pressure doesnt exceed a particular limit. Typically the wastegates can be mechanical or programmed for a certain psi.
It may be true that the amt boost may be regulated for optimum point on most cars but there defenitely is chance to increase the boost with carefull engineering so that there are no side effects to the increase in the boost. I guess the amount of boost is proportional to the compressor and cylinder capacity aswell
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Old 6th March 2008, 11:07   #7
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Originally Posted by Rotorhead View Post
Most turbos can support more than 5psi of boost. Excess boost could cause over heating and will need to be controlled using the intercooler and the wastegate ensures that the pressure doesnt exceed a particular limit. Typically the wastegates can be mechanical or programmed for a certain psi.
It may be true that the amt boost may be regulated for optimum point on most cars but there defenitely is chance to increase the boost with carefull engineering so that there are no side effects to the increase in the boost. I guess the amount of boost is proportional to the compressor and cylinder capacity aswell
I would be comfortable saying all turbos support more then 5psi, and all need to be controlled via a wastegate.

What type of overheating are you referring to? Of the engine, or the air going into the motor? Neither is good, but are caused by different things. Running turbos without intercoolers is not a good practice pretty much ever. Some manufacturers do this for cost cutting, but it's not a great practice.

Wastegates are always mechanical, but the method of boost control(wastegate control) varies between mechanical or electronic.

You can raise the boost on all cars, and the set boost from the factory is done so for many different reasons. Either longevity, power, economy, whatever the reason, it's not because it's "optimal". To raise the boost, you need proper fuel and ignition(timing) control, along with all the supporting cast: fuel system capable of keeping up, intercooler capable of keeping up, some sort of tuning capability, etc etc. It is not advisable to just turn up the boost without taking the proper precautions.

The boost can technically be raised as high as you want on just about any turbo, but the size of the turbo will determine how efficiently it is working in the range of power and boost you want to run. The size of the turbo or cylinder has nothing to do with how much boost the turbo or motor can run. The state of the motor, and the strength of the motor, the fuel, etc, is what determines what boost can and should be run.
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Old 6th March 2008, 11:12   #8
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Quote:
Originally Posted by HPP View Post
Some of the diesel turbos are build more sturdy for higher pressure situations and can handle higher boost thresholds(like 60 - 80 lbs of boost in very extreme setups).
Here's where I disagree. My source in Holset tells me that shaft sizing in diesel applications is much less critical (and hence smaller) because there is less chances of compressor surge than a throttled gasoline engine. Also, OEM turbochargers for gasoline engines usually have a turbine impeller and turbine housing material capable of withstanding much higher EGT.
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Old 6th March 2008, 11:18   #9
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Originally Posted by ananthkamath View Post
Here's where I disagree. My source in Holset tells me that shaft sizing in diesel applications is much less critical (and hence smaller) because there is less chances of compressor surge than a throttled gasoline engine. Also, OEM turbochargers for gasoline engines usually have a turbine impeller and turbine housing material capable of withstanding much higher EGT.
You could be correct, but then I am used to talking about diesel turbos that also cross over to my world of HP. For example my example is correct for Borg Warner turbos which are now becoming very popular in the performance world. I'll take a look at some other examples as well, and see what I come up with.
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Old 6th March 2008, 18:40   #10
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Quote:
Originally Posted by HPP View Post
I would be comfortable saying all turbos support more then 5psi, and all need to be controlled via a wastegate.

What type of overheating are you referring to? Of the engine, or the air going into the motor? Neither is good, but are caused by different things. Running turbos without intercoolers is not a good practice pretty much ever. Some manufacturers do this for cost cutting, but it's not a great practice.

Wastegates are always mechanical, but the method of boost control(wastegate control) varies between mechanical or electronic.

You can raise the boost on all cars, and the set boost from the factory is done so for many different reasons. Either longevity, power, economy, whatever the reason, it's not because it's "optimal". .
Firstly, the amount of boost corresponds to the amount of gas + air burnt in the cylinders and hence the corresponding increase in the temperature and hence the need for intercoolers. Secondly , i was speaking about wastegate control only and not the wastegate as such which obviously is a mechanical pressure release system. Thirdly, what i mean as optimal is optimal for the producer of the car which is all the things that you have mentioned , the word "optimal " is probably not the right one.
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Old 6th March 2008, 22:17   #11
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Soft turboes may be another term for light pressure turbos. They don't create enough pressure to do big dia plumbing, big intercoolers, ecu upgrades etc.
Replacing stock turboes with bigger turboes and upgrading the ECU alone won't work, if you are looking for more power from diesel engines. Everything associated need to be changed or alteast made sure won't fail.
Theoretically performance turboes on petrol engines and light pressure turboes are same. But that's theory. The components, electronics and what not are different.

When air is worked upon, ie, pressurised, it gets heated up, so needs to be cooled.
When you extract work from pressurised air, air gets cooled.

Disclamier:- all these are theories and may be wrong:-)
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Old 7th March 2008, 02:06   #12
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guys thanks so much for the knowledge and your inputs.
i wanted to asks that the mechanically controlled wastegates that most of ypu are talking about; would a blow off valve do the same and can a blow off valve be controlled(electronically or mechanically) to control boost pressure.
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Old 7th March 2008, 02:21   #13
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Quote:
Originally Posted by HPP View Post
I'm talking over 40psi etc), as the shaft and components are generally heavier and could/would affect spool up(slower).

I hope this makes sense, if not, just ask me to clarify whatever is not clear.
*40psi is a lot of boost from a turbo-i guess such application might only be used for track racing pupose right? please enlighten me on this.
*And does boost pressure vary for a diesel and a gasoline engine?(lets say for eg. if we have the same turbo charger for both engines)
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Old 7th March 2008, 06:04   #14
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Quote:
Originally Posted by Rotorhead View Post
Firstly, the amount of boost corresponds to the amount of gas + air burnt in the cylinders and hence the corresponding increase in the temperature and hence the need for intercoolers. Secondly , i was speaking about wastegate control only and not the wastegate as such which obviously is a mechanical pressure release system. Thirdly, what i mean as optimal is optimal for the producer of the car which is all the things that you have mentioned , the word "optimal " is probably not the right one.
About your first point, I'm not following what you mean. The need for an intercooler comes from the need to cool down the compressed/heated air that is coming out of the turbocharger. What is happening in the exhaust side doesn't really have to do with the need for an intercooler.

Quote:
Originally Posted by kutlee View Post
Soft turboes may be another term for light pressure turbos. They don't create enough pressure to do big dia plumbing, big intercoolers, ecu upgrades etc.
Replacing stock turboes with bigger turboes and upgrading the ECU alone won't work, if you are looking for more power from diesel engines. Everything associated need to be changed or alteast made sure won't fail.
Theoretically performance turboes on petrol engines and light pressure turboes are same. But that's theory. The components, electronics and what not are different.

When air is worked upon, ie, pressurised, it gets heated up, so needs to be cooled.
When you extract work from pressurised air, air gets cooled.

Disclamier:- all these are theories and may be wrong:-)
Like I mentioned before, there really isn't "light pressure turbos". The tiny turbos that come on the 1.8t motors in VW/Audi/Skoda's are extremely small but can produce a lot of boost if asked to do so. The CFM is low(tiny turbo), but the pressure is high still, and all turbo's are capable of this. It all comes down to what is asked of it(controlled by the wastegate..).

Quote:
Originally Posted by abhik View Post
guys thanks so much for the knowledge and your inputs.
i wanted to asks that the mechanically controlled wastegates that most of ypu are talking about; would a blow off valve do the same and can a blow off valve be controlled(electronically or mechanically) to control boost pressure.
Not really. The wastegate is the proper way to control boost. If you tried to let the turbo run high and control/bleed off pressure with the blow off valve, your turbo would have a very short life and likely end up in pieces, which could end up in your motor.. So the answer is no.

Quote:
Originally Posted by abhik View Post
*40psi is a lot of boost from a turbo-i guess such application might only be used for track racing pupose right? please enlighten me on this.
*And does boost pressure vary for a diesel and a gasoline engine?(lets say for eg. if we have the same turbo charger for both engines)
No. These are street cars driven on the street. The craze for horsepower here is insane. We have tuned cars to over 45psi in street trim.

A good friend of ours races his car at something like 65psi and about 1400hp.
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Old 7th March 2008, 07:13   #15
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Quote:
Originally Posted by abhik View Post
*40psi is a lot of boost from a turbo-i guess such application might only be used for track racing pupose right? please enlighten me on this.
*And does boost pressure vary for a diesel and a gasoline engine?(lets say for eg. if we have the same turbo charger for both engines)
Sorry, I missed your second point. Well all motors are set up for different levels of boost, it doesn't really matter whether it's a diesel or a gas power engine. One diesel engine and one gas powered engine could have the same turbo and run two different levels of boost depending on what it's tuned for and what it is capable of handling.
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