[SKavuri]

Thanks Dhanush for the interesting thread!

I trust the purpose of this thread is to help us understand how the load control on the Turbocharger works than really as a recommendation to go ahead and change the settings!

I will take the liberty of extending the discussion, and here are my views:

My opinion is that the turbocharger is a piece of precision engineered component with a calibrated pneumatic actuator and one needs to be sure of the implications before changing the calibration. I am not sure if the ECU gets any feedback signal from the turbocharger to raise the fuel flow to match the changed air flow. If the ECU fuel flow algorithm is only based on vehicle load/RPM, then the result of this recalibration of the bypass (waste gate) actuator is a bit complex.

As indicated by A350WXB and jdr, the pneumatic line to actuator is to act as a discharge pressure limiter for the compressor. So if the compressor is overloaded, then the stress fluctuations in the rotor leads to higher fatigue and premature failure. It could be a bit dangerous as the actuator is not fail-safe (it does not open the waste-gate at failure, and in-fact the waste-gate is fully shut when the shaft fails, as there is no pneumatic pressure to actuate the waste-hate). The turbine wheel will foul with the casing and make quite a big clank of noise. But the worst will be if the splinter particles find their way into the cylinder. Scary thought.

Plus there are other roto-dynamic parameters to consider: if the bypass (waste gate) is forced open always, then the the turbocharger rpm could exceed the design values - and could lead to resonance if it gets into critical speed band or the impeller tip speeds may simply exceed the design values (material stresses exceeding the allowable limits). But normally there will be significant design margins to avoid such events.

What is your finding after your adjusting it to minimal boost? Is it as per your expectation?

Anybody has info on how the "variable" geometry TC varies the "geometry"? is there a variable inlet guide vane or some such thing? Would be interesting to discuss on that.

[Sandman689]

Very risky and tempting proposition. I am trying my best not to fiddle with the turbo as I have no frame of reference and won't be able to revert back to factory settings should things go wayward.
I would love to squeeze more performance out of my engine, but I would prefer to leave these to the experts who have tried and tested them.

[dhanushs]

Originally Posted by Sandman689

... and won't be able to revert back to factory settings should things go wayward..

Reverting to factory settings is the easiest. You can always count/note down the number of turns you have increased or decreased, and revert back.

Remember the 'ol carburetor tuning testing.

[Sandman689]

Originally Posted by dhanushs

Reverting to factory settings is the easiest. You can always count/note down the number of turns you have increased or decreased, and revert back.

Remember the 'ol carburetor tuning testing.

Many people have advised me to keep everything stock. And I have accepted their advice up till now. What you are indulging me in Mr Dhanush, is a forbidden obsession.

[vikram_d]

Originally Posted by SKavuri

Anybody has info on how the "variable" geometry TC varies the "geometry"? is there a variable inlet guide vane or some such thing? Would be interesting to discuss on that.

Actuation can be done in various ways. It can be done using vacuum actuators, hydraulic actuators, electric servo actuators etc. My bet is that most modern systems use electric servo actuators thanks to their small size and also because being electric it will be easier to control them from the ECU.

On vehicles equipped with air brake systems you could also use an air/pneumatic actuator.

For those who want to know exactly how VGTs work, the below link is a nice resource.

http://paultan.org/2006/08/16/how-do...geometry-work/

[eapen]

Before doing the above mentioned mod for an FGT, to increase boost pressures one should have a Boost pressure gauge & a digital Coolant gauge to monitor, or if the ECU supports an OBD digital gauge - monitoring corresponding increase in coolant temperatures for the increased boost.

Normal analogue coolant gauges are slow to respond to temperature changes.

A better option to adjust boost is to buy a mechanical adjustable Boost Controller (with ceramic ball) & insert it into the actuator pressure line.

If this mod of adjusting the actuator length is performed for a VGT - vaccum controlled with actuator, you run the risk of damaging the turbo. The length of actuator arm is synchronized with the nozzle ring mechanism & variable vanes.

I have opened the vaccum controlled VGT turbo of Hyundai Verna & re-fixed it.

[eapen]

This are the pictures VGT turbo of the my 2008 Hyundai Verna taken while removing & re-fixing.
It is vaccum controlled by an air solenoid through the ECU. It also has the actuator mechanism similar to an FGT externally, but completely different internally.

Below is the internal mechanism with the nozzle ring assembly & variable vanes.

[atlantis0965]

Originally Posted by eapen

Below is the internal mechanism with the nozzle ring assembly & variable vanes.

hi
can you please post more pictures if you have any?

also could you elaborate a bit on how the vanes are actually connected to the linkage from the actuator ?

i guess this type does not by pass the exhaust gases from acting on the turbine wheel of the turbocharger; rather it just controls the angle in which the gases act on the turbine wheel there by varying the rpm ? right?

[TurboGuru]

Originally Posted by dhanushs

Hi,

I have not mentioned whether its the inlet or outlet. What I have mentioned is: that side (aluminum side) is the compressor (compressed air to the inlet) side and the other side is the turbine side.

I'm not sure how my post came out..

However, what I need to confirm is that, this illustration is to adjust your wastegate for different purposes NOT ONLY increase in power. Infact, the main reason why I ventured into this is that I'm turbocharging a NA diesel engine, and needed very minimal boost. So, i have set the wastegate accordingly.

Just thought of sharing the idea, and its different purposes. Also, I guess the disclaimer at the bottom covers for me?

No offence, great thread
BTW what is the project vehicle & which turbocharger you are opting for ?

[ringoism]

Originally Posted by vikram_d

Just one question, adjusting boost is easy. But what about proper fueling to go with change in boost?

I think most electronically-controlled (ECU) engines/IP's would adjust fuel delivery upward automatically (up to some maximum level), via feedback from the O2 / mass airflow sensors.

Years ago, I upped the boost via the described method on a Nissan/Datsun 280ZX Turbo (petrol), after adding an intercooler. The 2.8L inline-six went from 180bhp stock to probably near 250bhp (7-8psi boost stock, upped to around double that); and from being a low 15-second quarter-miler to a mid/high 13-second runner. Astounding transformation! Seriously pushed you back in the seat, could power-drift with ease, and just seemed to pull harder and harder the faster you went - Almost Scary!!! Put some tens of thousands of km on it after that with no reliability issues (but then, the stock block / head / bottom end of the 280Turbo were reputed to be good to 600+hp, and the BorgWarner T5 gearbox / rear diff were good enough for the increase, too) Whatever, with no other mods, this car was instantly transformed into absolutely the most fun and fastest machine I've ever owned, even compared with some big-block V8-powered vintage American muscle cars!

If I ever do a Turbo conversion on the Marshal, I'll definitely be playing with boost levels and related tuning a bit.

Yet, you do have to be VERY careful here... On an ECU-controlled petrol car, it's simple enough to arrive at a "safe" level of boost increase: Assuming the engine components are good for the expected power increase, simply add boost (via adjusting pre-load) in very small, cautious increments till the first signs of detonation (pre-ignition "pinging", "pinking") can be heard, then back it off just slightly so it's not at all observed (with your preferred quality / octane rating of fuel).

For tuning non-electronic Diesel engines / pumps (like the Bosch/Mico VE unit used on the Mahindra DI-Turbos, etc), i.e., to adjust fueling for the added boost, check out these links (at your own risk, of course... but this seems to be someone "who knows what they're doing"):

http://www.landroverweb.com/Pdf-file...ines_Rev_2.pdf

http://306oc.co.uk/forum/thread-131.html"]306oc.co.uk/forum/thread-131.html"]http://306oc.co.uk/forum/thread-131.html

http://306oc.co.uk/forum/thread-145.html"]http://306oc.co.uk/forum/thread-145.html"]http://306oc.co.uk/forum/thread-145.html

Though the long-term reliability / lifespan / maintenance costs of non-turbos (incl. the MDI) is often better, I love turbo'd cars (besides the 280, had a Mitsubishi Starion TSI) for their ability to greatly enhance performance while maintaining acceptable levels of fuel consumption.

Regards,
Eric

[ringoism]

Moderator: Please delete the duplicate post above (not my first one, also above). By the time I finished editing to clarify a couple points, the system wouldn't let me update. Thanks.

Originally Posted by ::CMS::

Most probably you will endup with a blown turbo when it goes beyond its tolerance levels and needs good lubricating and a bigger intercooler to cater the EGR tempreature under control

Not sure I'm grasping what you're trying to suggest there, but for anyone not clear on the theory:

An Intercooler is NOT designed / implemented in order to cool down / protect your turbo (or EGR or whatever). Turbos are typically oil and/or water cooled for that purpose.

What an intercooler IS designed to do is to cool down the air intake charge (and thus also combustion chamber), since according to the basic thermodynamic formula (PC=nRT), with all else being equal in a closed system, temperature increases proportionate to pressure. In a non-intercooler-equipped turbo, you do gain power (vs. NA engines) due to more intake charge being forced under pressure into the combustion chambers... BUT you lose some of what you would otherwise fully gain, simply because by pressurizing the intake air, you've automatically heated up your charge, and with hot air being less dense than cold air, you're actually not getting as much air/oxygen filling the cylinders as you could, thus your flow effectively decreases.

By adding an intercooler, that inevitably superheated, pressurized air coming out of your turbo is simply cooled down again before it enters your intake manifold / cylinder, so that it's more dense and oxygen-rich again! When an intercooler is added or the existing one is upsized, you can (and should !) increase your boost pressure to more fully realize an engine's potential. The main limiting factor (besides strength of engine components) re: boost pressures is the onset of detonation, due mainly to excessive heat in the combustion chamber. An intercooler, via a cooled intake charge, keeps combustion chambers cooler and less prone to pre-ignition, allowing you to crank up the boost beyond what would normally be possible.

The sensation of my 280ZX pulling harder and harder (post intercooler addition) as vehicle speed increased (kind of the opposite of most NA cars) demonstrates the effect: The air flowing past the air-to-air intercooler (in front of the radiator) was cooling the intake charge more and more as the vehicle speed increased, and thus, with denser and denser air flowing out of the intercooler, cylinders could be more and more fully filled and power actually increased with vehicle speed to a greater degree than increases in aerodynamic drag and mechanical friction would've otherwise decreased my rate of acceleration (at least, I THINK that's what was happening !).

Re: turbo longevity in the cases of increased boost pressures, I wouldn't expect that to be so much of an issue. Where modified turbo cars usually break down is in the basic engine components themselves, since everything's MUCH more highly stressed than in a N/A unit. My 280ZX's turbocharger was actually a modified T3/T4 unit with supposedly an upgraded center bearing, but anyway I was running fully double the stock boost, driving it hard/fast daily (a little racing in there), and put over 70,000km on it after the mods, with no issues whatsoever. It still ran strong when I sold it (humorously, a friend who owned an expensively modified turbo Mitsubishi came into the office some months after that, a little dejected, telling me how he'd just been soundly beaten in a street race against my old, rusty Datsun!). Keep boost increases moderate and drive sanely more of the time than I did, and I don't expect you'll have problems with the turbo itself.

As usual, just my 2 paise, of course...

Regards,
-Eric

[Sandman689]

Thanks for sharing. They were inspiring.

Originally Posted by ringoism

Yet, you do have to be VERY careful here... On an ECU-controlled petrol car, it's simple enough to arrive at a "safe" level of boost increase: Assuming the engine components are good for the expected power increase, simply add boost (via adjusting pre-load) in very small, cautious increments till the first signs of detonation (pre-ignition "pinging", "pinking") can be heard, then back it off just slightly so it's not at all observed (with your preferred quality / octane rating of fuel).

What if it's an ECU controlled Direct Injection Diesel Engine? Is the procedure same?

[ringoism]

Originally Posted by Sandman689

What if it's an ECU controlled Direct Injection Diesel Engine? Is the procedure same?

That's where I'm less experienced... with diesel combustion timing being controlled completely by the actual injection of fuel into the cylinder, presumably pre-ignition doesn't ever occur, since obviously there's nothing to ignite till the fuel's in there (vs. on spark-ignited/timed (i.e., petrol) engines, where the fuel comes in prior to the spark's igniting it, allowing the possibility of unintended early ignition via contact with high heat, under some conditions).

My guess is that the limiting factor(s) for diesels will be simply the strength of basic engine components and/or EGT's (Exhaust Gas Temperatures, which one of the links I posted does address a bit, if I remember right). There'd be a lot of good, specific info available out there online, since a large number of do-it-yourselfers abroad (U.S. in particular) are modifying / tuning (Dodge) Cummins/ (Ford) Powerstroke/ (VW) TDI diesels out there (Google it), all of which are ECU-controlled units.

At the very least, a temperature probe for a simple (electro) multimeter is not too expensive or hard to come by, and probably pretty important for proper, safe turbo-diesel tuning - as would be a simple psi-scale (0-25psi would suffice) pressure gauge. Without these, you're going to have some trouble ascertaining what all is going on as you make adjustments.

As far as ascertaining the strength limits of basic components (pistons, rods, crank, head-gaskets basically), well, you either have to make a conservative, educated estimate on the basis of similar engine designs or the histories of other modified units... or you just have to try it blind and be prepared to take some potentially costly risks (well, somebody's gotta do it ).

-Eric

[Frankenstein]

Dhanush i keep adjusting the boost and fueling depending on my mood, if you adjust for max boost and drive your car on the highway at high speeds then your turbo will blow.

[Harish.Krovvidi]

Why are indian diesels like innova or fortuner running internally wastegated system with intercoolers rather than using externally wastegated system with a blow off valve. Typically this system works better (in my opinion) as you connect the waste gate to the bov to boost it all way up to 8-10 psi in synch ... While internally wategated ones only develop like 3-6psi range.

Wont it make thoem diesel rockets rather than barges with mid power ranges (50-120)..