Turbo stuff

[magnus_heydoc]

This has been already discussed , however, maybe not in this level of depth..............
I know lots of guys have stuck on supra turbos and the like onto a 3B but I'd like to go with a new turbo unit. I've been lookin at a GT25R ballbearing unit.
The specs are 60 trim , .64 A/R exhaust housing, compressor 54.4 mm and exhaust 53mm.
I'm not too familiar with exactly what these figures mean or how they will be appropriate for my 3B. I thought I'd see what this forum has to offer as far as advice.
ADJ

 

[Tapage]

My contribution ..

I know that the Garrett GT28 is usualy used for 4.2 Land Cruiser Aplications ..

compresor wheel 60mm turbine wheel 53mm flow capacity 290HP but you have some diference in diferent models of GT28.

 

[magnus_heydoc]

so is the GT25 smaller? If so would that be appropriate for a 3.4 L?

 

[Tapage]

so is the GT25 smaller? If so would that be appropriate for a 3.4 L?

Mmm yes is smaller .. but I do not have the knoweldge to say if is right or not. I'm not sure if this fou you aplication can manage the air flow necesary.

 

[magnus_heydoc]

common you guys!

I need more information before I buy a turbo and start forcing the air down my 3B's throat!
Somebody that knows something chime in with some stuff I can chew on and help me make the right decision.
I want to produce 200 hp and 200ftlbs of TQ.

 

[Island Moose]

I need more information before I buy a turbo and start forcing the air down my 3B's throat!
Somebody that knows something chime in with some stuff I can chew on and help me make the right decision.
I want to produce 200 hp and 200ftlbs of TQ.

Do a search on this forum for "turbo", when you've read all of those posts, you may be in a situation to ask more specific questions.

 

[Vegard]

I need more information before I buy a turbo and start forcing the air down my 3B's throat!
Somebody that knows something chime in with some stuff I can chew on and help me make the right decision.
I want to produce 200 hp and 200ftlbs of TQ.

That's quite a lot! Guess you need something larger than the T25 then. I ordered a used Garrett T25 from a Saab 9000 today. I will probably mount it to my 3B the coming autumn. But am not planning 200 hp, more hoping for 125 or something like that.

Have you seen this one? Claiming 220 hp, 300 ft torque! http://www.overlandexperts.com/bj75biodieseloffroadtruck.htm

 

[Behemoth60]

This has been already discussed , however, maybe not in this level of depth..............
I know lots of guys have stuck on supra turbos and the like onto a 3B but I'd like to go with a new turbo unit. I've been lookin at a GT25R ballbearing unit.
The specs are 60 trim , .64 A/R exhaust housing, compressor 54.4 mm and exhaust 53mm.
I'm not too familiar with exactly what these figures mean or how they will be appropriate for my 3B. I thought I'd see what this forum has to offer as far as advice.
ADJ

First of all, if you're wanting to do some custom matching of turbo's to engines, it's probably well worth taking a day at the library and educating yourself on the subject. A few books I would recommend are 'Maximum Boost' by Corky Bell, and 'Turbochargers' by Hugh McInnes. All the information is very gasser specific, but if you can clear your mind of that clutter, these books cover all the basics, including how to choose a turbo charger. Alternatively, you can learn all you need to know about reading compressor maps, and even find a lot of maps, on the Internet. Then, I would suggest getting onto a mail list or forum, much like this one, and continue your education. The Junkyard Turbo group on Yahoogroups is very good. Then, you'll want to spend some time with some turbo calculators. Ray Hall's website has a number of awesome turbo calculators.... www.turbofast.com.au. I also like this site... http://www.prestage.com and go to 'Car Math'... I just tried it and it's not working... hopefully they fix it as it has a great set of engine calcs.

The specs you've quoted are meaningless for matching that turbo to your engine. You need the compressor map. With the specs you've quoted, you should be able to find said map.

Once you have the map, you need to plot on it the amount of air your engine will consume at various RPM's (every 500 rpm would be lots), at the absolute boost level you want to run. If the line you plot stays roughly around and through the maximum efficiency bubble on the compressor map, and doesn't cross the surge limit, then that turbo will work best for you.

Fact is, most small turbo's will 'work' on most small engines. The issue becomes whether you're maximizing the possible efficiency from your turbo or not. The difference in max power is probably in the range of 10-20%, but when youre' talking about power increases of 40-60% right out of the box, it's a minor concern unless you're building a race engine or something of the sort.

Peter Straub

 

[crushers]

too big a turbo and you get "turbo surge" so i have been informed...
cheers

 

[magnus_heydoc]

Awesome info Peter! I'll start working on it!

thanks Peter.

 

[wesintl]

THat's the turbo that comes up on the rall hall site. It's really the off the shelf Garrett model that fit's the 3B. I had been recommended that model from a turbo shop but I don't know how much they were going to massage the fan to the 3b spec. Anyway that's my weak .02

 

[brownbear]

ya the old, too small it chokes the engine. But spools quickly and gives lots of low end.

too big, you won't even notice it a the bottom. by the time it gets spooled up you are at highway speed. And if you got stock gears and big tires the engine rpm is too low to get all the boost.

so just right is what you need.

It also comes down to budget. I was looking seriously at new units. But my extra money got used in other projects. So I am going to try a junkyard unit I got. its off a Merkur. But I have to make an adapter. Where the turbo I was going to get built would fit the ct26 opening on my 13b-t manifold.

I'll let you know how it goes.... Trial and error baby!

 

[Behemoth60]

too big a turbo and you get "turbo surge" so i have been informed...
cheers

I am fairly certain that it's the other way around... Too small a turbo on too large an engine causes surge.

"Most compressors have a stability limit that is defined by a minimum flow rate on a pressure-rise-versus-flow-rate characteristic curve."

I've been told that surge is when the outer fins on the compressor exceed the speed of sound... the little itty bitty sonic booms from each blade cause all hell to break loos in the compressor. So I'm told. As you can tell, I'm not entirely convinced of this definition of Turbo Surge. All I can find in either of my books is the following...

"The surge area on the left side of each [compressor] map is a region of pressure and flow where the compressor is unstable. Depending on the compressor, this instability will vary from a sharp loud banging sound, to a sluch-pump-like action, to no surge at all"

Does anyone really know what surge really is?

Peter Straub

 

[crushers]

phone Alamo, this is where i got my (mis)information... but since he does this for a living i think i would listen to him...
no offense intended
cheers

 

[silvercrusher]

Now bear in mind I like diesels more than GT's but am trained in both and correct me if I am wrong Brownbear; but a surge on a GasTurbine compressor is defined as A complete breakdown of airflow in one or more stages of the compressor. Now being that a turbo runs on much the same turbine principles i'm sure it is the same.
You can actually have a complete reversal of airflow across the turbine from a surge. The blade noise you here is called Blade Flutter. And i believe is the blades singing at their resonant freq. . This can lead to the blades stretching and actually cutting a new groove in the casing and destroying the leading edge of the blade.
I think this would occur more on a smaller turbine that had huge pressure building behind it and could not get past the turbine fast enough. With to large a turbine you would never build said pressure fast enough and your spool up time would be very slow to say the least. Its all in the angle of attack and vector diagrams from the engineers.

Cheers

Challis

 

[brownbear]

ya silver you got it right.

heres from the book and my memory.

The compressor blades are actually tiny airfoils and are subject to the same aerodynamic principles which apply to the wings of aircraft. Like a wing, the blade has an angle of attack.
Which is defined as the acute angle between the chord of the balde and the relative wind. The angle of attack of a compressor blade is the result of inlet air velocity and the compressor's rotational velocity(RPM). The two forces combine to form a vector, which is the actual angle of attack of air approaching the airfoil..

As with a wing if the angle of attack becomes too great, airflow across the airfoil section will be disturbed, and a stall will occur. A compressor stall, a condition all gas turbines from time to time, can be described as an imbalance between the two vector quantities, inlet velocity and compressor roatational speed. Compressor stalls cause the air flowing in the compressor to slow down, to stagnate(stop), or to reverse direction, depending upon the intensity of the stall. Stall conditions can usually be heard and range in audibilty from an air pulsating, or fluttering sound in their mildest form, to louder pulsating type sound, or to a violent explosion. Quite often the cockpit gauges do not show a mild stall condition, called a transient stall. These stalls are usually not harmful to the engine and often correct themselves after one or two pulsations. Severe stalls, called "hung stalls" can significantly impair engine performance, cuase loss of power, and can even damage the engine.
The pilot can identify compressor stall conditions by its audible sound, by fluctuations of RPM , by an increase in Exhaust gas temperature, or by a combination of these clues.

stalls maybe caused by;
-turbulant or disturbed airflow to the inlet ie flight manouvers.
-excessive fuel flow caused by an abrupt engine acceleration
-contaminated or damaged compressor blades
-excessively high or low rpm for a given airflow( so could be a maxed out rotational speed on a little turbo, or too large a turbo spinning well below its design speed and loosing the boundary layer on the airfloil.)

The statement above is partial my words and mostly out of my text books.

There is also" bootstrapping" which may be confused as surging. Bootstrapping is a condition under part throttle operation. where a continual drift of manifold pressure occurs. An undesirable cycle of turbocharging events causes the manifold pressure to drift in an attemp to reach a state of equilbrium.
Maybe caused by rapid throttle movement, the wastegate hunting for the proper setting.

I feel compressor stall may happen most in a situation where too small of turbo is selected for the application. It is then maxed out and starts to break down the airfoil. which would cause it to slow down and speed up again. Giving the surge feeling.

or as noted above, waaay to large a turbo, it would be loosing the boundary layer over the airfoils and becoming separated.

ok I am studied out for now............

That help anyone?

 

[Tapage]

wou .. I'm impressed. Thanks for this free lessons.