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Saturday, May 7, 2011

Handy Conversion Tables when dealing with turbos

When dealing with turbochargers you always come accross alot of different units of measurement.

That's why I made this conversion table here for you. I started out with only a few. But over the weeks I kept adding equations that are usefull. Put in the value you want converted, like 20 PSI.

Type in 20 the PSI box and click with the mouse on the BAR box and you will get the value in BAR.

I have made conversion tools for pressure ratio, that will come in handy if you are reading compressor maps. Along with conversions for airflow. And also some custom made equations that calculate Airflow to HP and turbo inducer mm to HP and much more. So these formulas will be of great help when reading turbocharger compressor maps. Keep in mind that some of these formulas are to give you estimates of what is theoretically possible to obtain.




lb/min to CFM



These two formulas will give you an estimate of the theoretical engine HP you can expect from the given airflow.
lb/min to HP






The following formulas will calculate you're theoretical horsepower on the wheels (WHP) on ordinary 93 pump gas for any given airflow.
lb/min to theoretical WHP on (US 93 Pump Gas)



CFM to theoretical WHP on (US 93 Pump Gas)



The following formulas will calculate you're theoretical horsepower on the wheels (WHP) on European 98 pump gas for any given airflow.
lb/min to theoretical WHP on (Europe 98 Pump Gas)



CFM to theoretical WHP on (Europe 98 Pump Gas)



The following formulas will calculate you're theoretical horsepower on the wheels (WHP) on E85 fuel for any given airflow.
lb/min to theoretical WHP on (E85 Fuel)



CFM to theoretical WHP on (E85 Fuel)



Pressure Ratio (ATM+Boost) to Boost Pressure (BAR)



Pressure Ratio (ATM+Boost) to Boost Pressure (PSI)



Map sensors (Mainfold Absolute Pressure) usually use kPa so this formula show you how much it is in BAR
Kilopascal (kPa) to BAR



This formula will calculate and give you the theoretical horsepower from the given turbo inducer size. Now this will only give you an idea about the possible power you can get. Because there are many factors that come into play. Also note that this formula only works one way.
Turbocharger Inducer (mm) To HP

Inducer MM





HP to KW



NM to lbs/ft









KG to lbs






I also have more technical pages for you that will come in handy. They will be of great help when looking at compressor maps Use the conversion tools And you will be able to calculate airflow, pressure and HP figures for the turbocharger you are interested in.


Anonymous said...

Please tell me what A/R compressor housing and inducer/exducer i should be looking for if i want to put the turbo on a 1.3 and i want the turbo to start spooling at about 2800rpm. I'm really really confused.

Anonymous said...

and also for a 1.5 and 1.6. Thank you.

Leo Valek said...

Dear Sirs, I plan buy the turbocharger Garett GT1548 for my motor bike Yamaha FZ1 (1000 ccm, 150 PSI @ 11000 RPM). I'm selecting a gear pump for oil for this GT1548 now. Can you send me a information, what pressure and flow of the oil I need for the turbocharger, please ? And can you approve me the best oil type for the turbocharger ? Thank you very much for your quick response. Leo Valek ( leo.valek@flowservice.cz)

JD said...

Leo getting oil to the turbocharger on a motorcycle is the easy part and the oilflow and 4-5 bar pressure from the stock oilpump is enough. The hard part is getting the turbocharger mounted high enough. Normally because of clearence issues (front wheel, fairings, radiator, intercooler, oil cooler and turbocharger along with pipes and hoses all need to fit in a very tight space) the oil outlet will often have to be mounted lower than the engine sump / oil pan and this will cause problems for the oil to return to the engine.

The easiest way to solve this is to get an 12 volt electric oil pump. If you can't find an aftermarket 12v oil pump you can get yourself an 12 volt electric water / Diesel pump to drain the oil. You will find that these are more common use in boats and marine environments.

These electric pumps can normally pump 8-12 liter/min water / Diesel and have been tested to work very well with oil for turbocharged bikes. They are small and compact and are built good enough to last a long time on a turbo bike. The best oil for any turbocharged bike or car is a fully synthetic oil 5w50 or similar, remember a turbocharger get very hot and needs a good oil to last.

Anonymous said...

Why no info or even mention of the Garrett GT25 VNT - stands for Variable Nozzle Tehcnology? Instead of a single injector, it has 12 vanes that go from 0-100% open. Not only was turbolag basically eliminated, a wastegate is no longer necessary. Was introduced for 1989 Shellby and seemed awesome, but then less than 3000 were made.

I have access to a rebuilt one and desperately want to know what the deal with 'em is.

They seemed to work great from what I can gather is the problem durability???

Kits to rebuild it exist on ebay cheap enough, except for the VNT part and maybe getting the actuator to work wth it, I'm not sure. I wonder if the VNT or vanes part of it just doesn't last or needs constant work etc.

I'm trying to size the right turbro for a conversion (never been turbo'd) for a straight 6, 12 cyl SOHC, with 3.5L. Finding answers is so much harder than I thought it would be. FYI, happens to be BMW e24 aka M30 engine or model 635csi.

Any help or advice ..... anyone, anyone?

JD said...


Well I would put up some info on the VNT Garrett turbochargers if I could find any. But because so few where made it's hard to find much about that specific VNT turbocharger. But it's true that the early VNT turbochargers had some problems with durability, especially on gasoline engines.

Today you will mostly find VNT or similar variable turbochargers that have vanes or adjust the exhaust gases in the turbo exhaust housings in a similar manner on Diesel engines. And they work well in Diesel engines because the exhaust gases are much cooler than your avarage gasoline engine. Not saying that the VNT turbocharger can't work on a gasoline engine, it's just the added heat produced by a gasoline engine that can cause problems for the VNT turbocharger to work without problems.

When it comes to BMW and dealing with the M30 3.5L engine, you really don't need to worry about turbo lag or anything like VNT turbochargers because a big SOHC 3.5L engine will have no problem spooling even a big GT35R turbocharger by about 4000 rpm. So it's really more about what sort of power you wan't to make and where in the powerband you want it.

I'm sure you can find some inspiration if you have a look in the Project section at the PPF Turbo forum http://server.pure-pf.com/phpBB/viewforum.php?f=2

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Folks don't forget about racing safety gear when buying auto racing parts

I have been tuning engines for a long time and with that experience I tend to look a bit more at how other people tune their cars and bikes than anyone else. Now this is not true for everyone, but most of you will recognize yourself at some level.

About 25 years ago the level of tuning an ordinary street car would ever see was at most 30% increase in power. (Not true for every car out there, but I'm talking ordinary street cars here)

So if you had an Ford, Volvo or BMW the amount of power you could get would have been in the 150hp range and in some extreme cases 250hp. At this point this was the "limit" of ordinary naturally aspirated engines at that time. Yes there was a lot of racing going on at that time, and some of these race engines did get put into street cars and power levels would have been 300+ hp. But the amount of maintenance these race engines required and the cost to keep them running were too much for most people.

Back then you could not just go into a racing store and buy yourself a set of forged pistons and connecting rods. Let alone camshafts and valves to build your race engine.

With the introduction of turbochargers however the power suddenly increased to levels that are still uncommon in today’s cars. At the beginning people where not really sure how to tune turbo engines and intercoolers where something that most people had never heard of. Silicone hoses where did you get that?

You would have to know someone in the maintenence department that did service on trucks or busses that had turbocharged Diesel engines at the time to buy the simple things like, clamps, hoses, gaskets, oil lines etc. Even something like an external Wastegate that are availiable almost everywhere now today you could not get your hands on. And something like real drag tires where not that common either.

But as time passed by, engine tuners got their hands on more parts, most that had the machines and tools started to make their own intercoolers, wastegates and all the parts that were hard to get and the knowledge and the tuning business took of.

Now it still took some time before engine management systems and electric fuel injection where you could really start to extract power out of engines became common and figure out how to tune the software to make that work. To start if you found someone who could tune these you would have to fork out serious doe to get everything working. Well you still might have to do that today, and serious race teams do spend alot of money to get the electrical side working right. Today there are so many more things you can do with a powerful ECU, like traction control, different boost pressures for low and high gears, launch control, shiftcut etc.. This list is very long.

But before all that came chip tuning and fuel injected turbo engines. What was unheard of just 20 years ago would now become a reality for anyone with a few minutes of tuning. Some of you might know the story of the Ford RS Cosworth, Nissan Skyline, Audi S1 Quattro, Lancia S4 to name a few and other icons of the late 1980 and early 1990. The turbo engines back then would give you 200hp and that is still today 25 years on about the same power level you would get from a new car. However today this is a common power figure for a station wagon. And back in the 80s only a few racing breed turbo engines would give you that.

But with a few changes to the ECU with chip tuning and some larger fuel injectors all that was needed then was to turn up the boost pressure and 350hp where unleashed. The only real limit here was only how much air the standard turbocharger could supply.

Sure there where different levels of basic tuning you could do but the effect was the same, more power.

With more and more tuner friendly cars coming out over the years the power figures are still holding almost the same. Just until recently where the powerfigures have really started to go up and beyond what was thought possible only a few years ago..

But what have really changed today is the huge amount of DIY tuners out there. What engine tuners did 25 years ago have now entered the garage and racing parts have now become widely available to anyone. From the cheap Chinese made turbo exhaust manifolds to wastegates and almost every tuning part you can think of to the pure racing parts like forged pistons and engine management systems on sale that anyone can buy.

So what has happened is anyone with a little background in mechanics can now build their own race engine. Power levels have just gone up and up and up.. It’s not uncommon to see street cars today with 500hp and then there are the ones who have gone even higher, breaking the 1000hp barrier.

The one thing that all these engines have in common to achieve such power levels are of course the turbocharger. Without the turbo it would not have been possible. Well a supercharger or N02 injection could do the job too but that’s another story.

However time and time again people forget the most important parts when tuning cars. I’m talking about safety and racing safety gear. I do see that people buy racing seats and that’s good. But most of the time they don’t buy racing seats because of the added safety. It’s because they think racing seats look good. And what about things like auto racing helmets that keeps your head intact. Most of the time people come to the track without real racing helmets and if it’s street racing that’s taking place, no one seems to bother wearing any kind of racing helmets at all.

I do understand that people feel protected inside their cars and they don’t think they need roll cages and in some cases opt for roll bars instead but you really need to think about this.

Some of the racing safety gear you should look at are the following:
racing suit
racing shoes
racing helmets
racing gloves

This would be the minimum for my liking if your going on a trackday or similar race day event with your tuned car.

In case you don’t have a fuel cell in your car and there is a chance of fire or fuel leak then you should consider racing fire suits also because these will save your life.

Fire is not to be taken lightly. If you have a good fuel system in place to feed your engine and anyone who are looking for power is going to have that. Then you need to understand that at any given time those racing fuel pumps are pumping 2 gallons of fuel every minute. And if you get a leak and have an accident you are in real trouble if the power to the pumps are not cut right away.

So having the right racing safety gear to protect you is always a good choice. Today’s car are much safer than the ones years ago, but you need to understand that when we double and triple the amount of power and turn our 100mph car into a 200mph fire spitting monster of a car you really, really should spend some time and pick out some racing safety gear also.