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Sunday, February 24, 2013

Garrett GT2860RS - 62 TRIM - 360 HP Disco Potato

The GT2860RS "Disco Potato" model 739548-1 and 739548-5 turbocharger is basically a GT28R turbo with a 62 trim compressor 0.60 A/R and a 76 trim turbine 0.86 A/R. The Disco Potato was voted top 20 New Products at SEMA 2003.

This turbocharger is an upgrade turbocharger for the GT2554R model number 471171-3 and GT2560R model 466541-1 turbine housing flanges are outline interchangeable.

This turbo has a flow capacity of about 250 - 360HP and works well for engines between 1.8L - 3.0L. Gives good spool and would be comparable to the HKS GT2530. But have the fastest spool of the turbochargers in it's category.

The Dual Ball Bearing GT2860RS turbo assembly have a T25 style turbine inlet (NOTE: without studs). It also has an internally wastegated style T25 turbine housing with actuator bracket and actuator fitted from the factory.

Now before I go any further you need to know that there are actually 3 different versions of the GT2860R turbocharger (ONLY R at the ending). This turbo is the RS version named GT2860RS, and somewhat a hybrid with a bigger compressor and of these there are 2 different RS versions 739548-1 and 739548-5. Both these are called “The Disco Potato” and the only difference between these RS versions are basically the turbine housing. So I will cover both "Disco Potato" turbos here.

It's a bit confusing yes, however don't forget to read the story behind the Disco Potato turbo and how it came to be further down after I give you the specifications.

Model: 739548-1 and 739548-5
CHRA: 446179-66

Bearing: Dual Ball bearing
Cooling: Oil & Water cooled bearings

Compressor
Inducer: 47.20 mm
Exducer: 60.1 mm
Trim: 62
A/R 0.60

Turbine Model 739548-1
Wheel: 53.90 mm
Trim: 76
A/R: 0.64
Turbine Housing PN 430609-230

Turbine Model 739548-5
Wheel: 53.90 mm
Trim: 76
A/R: 0.86
Turbine Housing PN 430609-231

Wastegated
Turbine Flange: T25 without studs
Turbine outlet: T25 flange 5-bolt pattern



Looking at the compressor map for the GT2860RS turbochargers will show you that it have a very broad range. Even if you have a low boost of 1bar it will flow 350+ hp if your engine is capable.



Here we see the two different turbine housings at work. And the bigger 0.86 A/R will give you more flow and in effect even more top end power. However it should be recomended to use the bigger one also if you have a big 3 liter engine. The ball bearings will give you exellent spool even if you don't use the smller 0.64 A/R turbine housing.

 The measurements and turbo flange drawings can be viewed in fullscreen.

The GT2860RS use the Standard T25 oil drain flange.

Oil inlet 0.4375IN - 24 Thread for 6.35 Tube Inverted flare connection PER SEA J512 Oil inlet
Oil outlet 2 x M8x1.25 13.5 oil outlet
Water connections thread M14x1.50

The Turbine wheel is cast from "Inconel" material suited for extreme applications. The Turbine housing have the traditional T25 5-bolt flange. 

This is the story behind the Disco Potato Turbocharger

The story starts with Dan Passe who, at the time, was a Nissan PR genius with a penchant for bending rules. He conveniently "lost" the paperwork for a 1.8-liter Sentra which Nissan Design International had modified for the L.A. Auto Show. The car quietly landed in the hands of Nissan engineers Steve Mitchell and Mike Kojima.

Meanwhile, a few miles away at Garrett, turbo engineer Jay Kavanagh wanted to boost his Miata. Having full access to the newest Garrett technology, he concocted a physically small turbo with a ball-bearing center section and internal aerodynamics 20 years more modern than the T3/T4 standard the aftermarket is used to.

A few cubicles from Kavanagh, Rob Cadle, a good friend of Mitchell and Kojima, realized Kavanagh's Miata turbo would be perfect for the SR20DET the Nissan boys were planning for the Sentra. He brewed up a turbo, stuffed it under his shirt, and went out the back door.

The Sentra was painted a unique combination of psychedelic, color-shifting brownish paint and was thus dubbed the Disco Potato.

Jim Wolf Technology built a very mild SR20 for the Sentra, making it functionally equivalent to a stock Japanese-spec SR20DET. The turbo was installed, and amazing things started happening. The car's power was impressive, 280 hp at the wheels, but not earth-shattering. The driving experience however, was. Throttle response was excellent, turbo lag virtually non-existent, and the tire-shredding power was easily modulated. The turbo spooled up early, making so much torque, that the best quarter-mile time (13.7 at 104.5 mph) was achieved launching in second gear.

Mitchell brought the Disco Potato to the Ultimate Street Car Challenge in 2001, and placed an impressive fourth overall. The rest of the time, the car was stashed away in Nissan USA's service garage and used strategically as an attitude adjustment tool. Whenever Nissan or Garret executives needed an injection of gasoline in their veins, they were offered the keys. They would inevitably come back grinning from ear to ear and breathing heavily, eager to bring horsepower to the masses.

During one such outing, which included a 1,000-mile road trip as well as a track day at Thunderhill Raceway, the fwd Disco Potato outran every car at the track and then blasted down the freeway at 140 mph. Several Garrett executives also experienced the Potato. They were so impressed, they decided to produce the turbo, double the engineering staff in the aftermarket department, and start applying this modern Garrett technology to a whole range of aftermarket turbos.  End of story.

Did you like the story? I sure did. A lot of people find the Disco Potato turbocharger as a very fun turbo to drive. And here is a little video of a Honda Civic B16 fitted with a GT2860RS turbocharger. I might add that this 1.6 liter engine drives and spools the GT28RS Disco Potato quite well.

Video text:

This car now has a third setup. First setup was a b16a2 N/A, second - b16a2 turbo, but burst slevees and now I will gave him a new life with the next engine, he has forged pistons and connecting rods. I'm using a turbocharger Garrett GT28RS (Disco Potato), what generating power 328,3HP and 323,3Nm with the 1bar of boost (14,5PSI).


You might want to fit this turbocharger to you're own car perhaps. Well sometimes there are a few problems, especially when using the existing turbo manifold.

Because most standard cars don't come with a turbo this big from the factory, you start to run into clearance problems.

However these problems can be solved quite easily with an simple turbocharger flang fitted as a spacer between you're standard turbo manifold and the turbo itself. Like on this Saab turbo. There was no need for grinding or further modification to make the GT28RS turbocharger fit. We can see the extra turbo flange with seals in the picture. 


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.

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Posted by JD at 11:40 PM 76 comments
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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.