Garrett GT Turbos, here is why they are better.

[Hollywood]

Here is some info for people to check out. Most people understand that the Garrett GT turbos are superior to the older lines but here are the reasons why and some comparisons;

T04B, old school technology, 20+ years old!
T04E, older technology but still used due to part availability and it is considerably cheaper because of this. Many companies rebuild this turbo as well competition reduces cost and maintenance.
T04S Newer Race/GT housing 4" inlet standard.
T04R 1 word "hardcore!" For full out drag race cars.
Then there are a series of GT housings.

Here is why GT turbos are better;

1. Improved Aerodynamics - The modern GT wheel is the result of decades of development and testing using the latest technology and tools.
-Many "T" applications are based upon older/outdated wheels from the previous decades.

2. Better wheel match/ratio: Each turbo consists of a careful matched turbine and compressor wheel that is known to work extremely well together which also, allows the combination to reach the highest level of operating efficiency.
-Many "T" applications are randomly selected combinations based solely upon a compressor flow requirement or a turbine flow requirment in relationship to an engine size. As a result, a lot of "untested" combinations are used.

3. The GT's larger A/R housing allows the turbo to reach peak turbine efficiency. Not only is backpressure reduced, but the increased turbine efficiency allows the turbo/engine to make better power across the entire RPM band. A large A/R "GT" Turbo with a good wheel combination will outperform a small A/R "T" in both spool-up and power.
- In many "T" applications, the selection process for the A/R size is influenced by the desire to have boost at a certain RPM range. Here, the tendency is to use a small A/R as an attempt to shift the boost curve to the lower RPM. As a result, the selected turbine wheel is not allowed to reach it's peak efficiency because of the small A/R. The overall result is a lazy turbo that is not efficient, a combination that only looks good on paper.

4. The GT Ball Bearing makes a good turbo even better. The low friction design offers less drag on rotation and endures thrust much better than journal bearing turbos. Better transient boost response makes the turbo much more responsive during both cruising and wide open throttle driving conditions. By reaching full boost sooner, the GT Ball Bearing turbo makes more power available sooner, negating the need to "rev out" the engine constantly.
- Many "T" turbos can make the high peak HP numbers, but only the GT Ball Bearing turbos make the high HP and offer a power curve with a wider torque band that spreads the power across a more usable range. A high torque number is no good if it is reached 200 RPM before redline.

5. The last reason to switch to GT is: Its now easy to do with a drop in turbo design. No major reconfiguring of the turbo kit is necessary. In most cases, all major hardware such as manifold, downpipe, pressure pipes, etc. is retained.



Enjoy yourself!

[Loose]

you left out price!

[milesmcewing]

LOL

[Hollywood]

Originally posted by Loose
you left out price!

What does price have to do with why they are in technical terms better?

[Redlyne_mr2]

I'm saving up for a gt28rs, should be a nice turbo for my car

[Inthered]

^^ I would love to get that turbo for one of my cars!! I read some crazy reports about it.

[Kor]

I really like your post. Basically, its all true. The GT series turbos are the best.

However, there are some points I would like to make, just so that both sides of the coin are being presented.

One, just because a turbo's design is old does not mean its bad. The older T series turbos are "proven".

Two, really its not about the turbo but how you use it. You can build a turbo system with an older T3 or T04 series turbo that will perform just as well as a GT series turbo. By just as well, I mean it will spool similarly and yeild similar hp/torque. You might find this hard to believe - but what it comes down to is properly sizing the turbo to the engine and application. Although you point out that "many T applications are randomly selected" the truth is that the selection process is not random. Well, for some people it IS random, and they end up dissatisfied. But for others, the process is scientific, and you get a very well tailored turbo.

Three, price. You can honestly buy 3 to 4 older T series turbos for the price of 1 GT series turbo. Or, you can put the money you save into supporting modifications (such as an intercooler, exhaust or intake improvements). For any given amount of money, I think you can probably build a better system with the T series just because you will be able to buy more other stuff.

Finally, fourth. I disagree that its easy to drop in a GT series turbo. The flanges and bolt patterns are largely different. As far as I know, the majority of hardware (manifolds, downpipes) that exists for T3 or T4 applications absolutely will not bold directly to a GT turbo?


I would just like to say though, that I am a big fan of the GT series turbos. They do have a wider power band, and its easier to have a "one size fits all" attitude with the GT turbo because to a large extent its true. They do have slightly higher efficiencies (although this is often exaggerated). They are newer in design and probably more durable.

Great post! Any comments on what I wrote above?

[lude_conduct]

That's just it though. The T series would spool similarly to a GT, but won't be making the same power. Or it will have noticable lag, and make the same power. That's pretty much the whole point to upgrading to a GT series, you get the best of both worlds.

[Kor]

I think it can spool *similarly* to a GT and make the same power.

Impossible you say, the efficiency dictates the power at a given airflow. Yeah, true.

But, is the difference big enough to notice?

More importantly, can a person compensate for the difference by spending money elsewhere?

If you compare compressor maps, you can match a T series pretty closely as a GT series.

IMO the turbine side is where the problem lies. The GT series can have a larger A/R but still spool quickly. On a T you need a smaller A/R. You can also go from a stage 1 to slightly larger stage 2/3 wheel for more flow at the same A/R but again you are sacrificing spool time. Its a balancing act I guess.

Some people are now supplying a T3/T04e turbo with a GT wheel. So, you get the better aerodynamics of the GT wheel as well!

There is such a thing as spooling too early (this is driver preference I guess). On a VW 1.8T for instance, I think it delivers boost too soon. I would like the stock boost to come on 500 rpm's later.

Anyhow, I was most interested in the comment that you could bolt up a GT series turbo as a straightforward upgrade...

[Hollywood]

Originally posted by Kor
One, just because a turbo's design is old does not mean its bad. The older T series turbos are "proven".

Well it kinda does actually. T04B compressors are less effecient, T04E's are good still, many configurations you would not use the T04S and above compressors anyways. But in the GT3x adn gt4x line there are housings specifically designed for the GT wheels that specific configuration will yeild more performace out of those turbos.

Originally posted by Kor
Two, really its not about the turbo but how you use it. You can build a turbo system with an older T3 or T04 series turbo that will perform just as well as a GT series turbo. By just as well, I mean it will spool similarly and yeild similar hp/torque. You might find this hard to believe - but what it comes down to is properly sizing the turbo to the engine and application. Although you point out that "many T applications are randomly selected" the truth is that the selection process is not random. Well, for some people it IS random, and they end up dissatisfied. But for others, the process is scientific, and you get a very well tailored turbo.

Three, price. You can honestly buy 3 to 4 older T series turbos for the price of 1 GT series turbo. Or, you can put the money you save into supporting modifications (such as an intercooler, exhaust or intake improvements). For any given amount of money, I think you can probably build a better system with the T series just because you will be able to buy more other stuff.

Older T3's perform just as well? No I dont think so, older T3/T4's ya with the proper trims and housings a good turbo still can be selected from that line, but it wil have less peak hp and will spool later, and have a good chance of more back pressure as well which is a negative.

In this post money is not an issue as I am compairing performance not costs.

Originally posted by Kor


Finally, fourth. I disagree that its easy to drop in a GT series turbo. The flanges and bolt patterns are largely different. As far as I know, the majority of hardware (manifolds, downpipes) that exists for T3 or T4 applications absolutely will not bold directly to a GT turbo?

Nope the exhaust side of GT3x is still the same as a regular T3. The flange is the same, but they offer the 4 bold exhaust side standard over the 5 bolt which is better anyways. The center section is the same as well as far as the oil and coolant feed ins. The only difference is you need to run a restrector on the oil side for the GT.

Another example is if you have a GT25R, and take my car for example, it bolts right up as it still has a t25 exhaust flange, and still is a T2 center section, and the turbo fully fits on my car, just the question is on some cases do they have room for the T04s compressor with other cars?

[Kor]

I kind of qualified my own statement in the next sentence, "By just as well, I mean it will spool similarly and yeild similar hp/torque." My main point was, its not about the turbo but how you use it. Because in theory, yeah the GT will perform better, no question. But in practice, I am not sure this is true. What you are saying, is the GT series are better. What I am saying is, a car with a well chosen T series could perform as well as a car with a GT series turbo. So, although the turbo is not as "efficient" the car itself is going to be better. What is a better car? Well, maybe faster drag time, or auto-x time. It depends on what you pick the turbo for.

I will agree with you that for sure you can't make boost sooner AND make more peak HP with the older line. But you could make boost sooner OR make more peak HP. So depending on the application of the car, you might have chosen a better turbo for that application. Example: auto-x, you would want more torque down low, while drag, you want more peak HP. A given GT turbo is not going to be better for both drag and auto-x than if you choose a T series turbo specifically for one or the other. So, the GT is more versatile in my mind, but not "better".

I might be wrong, but I just want to be clear on what I mean.

On a side note, I think leaving money out of the post is ridiculous. Thats like saying "look, a VW Golf is faster than a Civic". Then someone might say, well, they are different prices. And they might add, given some mod money for both cars, I can make the civic faster. That is a worthwhile contribution. It might sway someone into thinking the civic was "better performance". Not a great analogy, but I am tired.

Basically, a T3 or T3/T4 would be what I would want as an alternative to say a GT28RS, the exhaust side of those two is definitely not the same though right? So if I already have a T3 and want a GT28 I am out of luck, unless I want a GT3x... but I definitely don't, a GT3x is too big So the upgradability kind of depends on the car.

Anyhow, I like this conversation, I am not tryin' to be a dick or anything, just want to argue for argument's sake

[gpomp]

Here's a GT28RS with a T3 housing...

http://www.atpturbo.com/Merchant2/me...egory_Code=GRT

[Hollywood]

Originally posted by Kor
What I am saying is, a car with a well chosen T series could perform as well as a car with a GT series turbo. So, although the turbo is not as "efficient" the car itself is going to be better. What is a better car? Well, maybe faster drag time, or auto-x time. It depends on what you pick the turbo for.

A regular T will perform close in some cases, but never as good. The guy doing drag will be faster with the GT, the guy doing autocross will be faster. With the GT.Hands down no questions asked.

Originally posted by Kor
I will agree with you that for sure you can't make boost sooner AND make more peak HP with the older line. But you could make boost sooner OR make more peak HP. So depending on the application of the car, you might have chosen a better turbo for that application. Example: auto-x, you would want more torque down low, while drag, you want more peak HP. A given GT turbo is not going to be better for both drag and auto-x than if you choose a T series turbo specifically for one or the other. So, the GT is more versatile in my mind, but not "better".

I might be wrong, but I just want to be clear on what I mean.

Unfortunately you are wrong. There is not only “one” GT turbo to pick from. While you pick a specific T3/T4, you would pick a specific GT for your racing desires. You cant compare a GT30R say to a T3/T4 50 trim, then compare it to a T76 at the same time, but then you could compare a T3/T4 50 trim to a GT25R or GT30, and a T67 to a GT42R. You have to compare apples to apples son.

Originally posted by Kor
On a side note, I think leaving money out of the post is ridiculous. Thats like saying "look, a VW Golf is faster than a Civic". Then someone might say, well, they are different prices. And they might add, given some mod money for both cars, I can make the civic faster. That is a worthwhile contribution. It might sway someone into thinking the civic was "better performance". Not a great analogy, but I am tired.

It’s not ridiculous, this is where you fail to comprehend.

“Do you understand the words coming out of my mouth?”
This was an informative post not ment to compare money or value but to compare the 2 styles of turbo’s and their technical differences. Not sure how many times I have to repeat this.

Originally posted by Kor
Basically, a T3 or T3/T4 would be what I would want as an alternative to say a GT28RS, the exhaust side of those two is definitely not the same though right? So if I already have a T3 and want a GT28 I am out of luck, unless I want a GT3x... but I definitely don't, a GT3x is too big So the upgradability kind of depends on the car.

Anyhow, I like this conversation, I am not tryin' to be a dick or anything, just want to argue for argument's sake

Again where you lack in knowledge as explained above there is a T3 version of the GT28RS.

If you want to argue, make your have the technical knowledge to back up what you say, because so far it’s been a waste of my time to point out your technical ineptness, it’s obvious you do not understand fully, due to repeating your same arguments and contradicting yourself all over your posts in this thread.

I try to display some good technical info for people to read up on and then have to spend time trying to undo pollution from people who think they know what they’re talking about. It’s rather annoying. And if one insists on arguing for only the sake of arguing then they have issues.

[M_Power]

Kor, this post was never intended to make a statement that you should or should not buy a GT series turbo over a T4 or any other. It was just posted to inform beyond of the obvious advantages that the new technology of these turbos has. No need to have an argument over it.

[Hollywood]

Originally posted by M_Power
Kor, this post was never intended to make a statement that you should or should not buy a GT series turbo over a T4 or any other. It was just posted to inform beyond of the obvious advantages that the new technology of these turbos has. No need to have an argument over it.

Exactly!

[Maxt]

I guess I will just add that it probably depends on the car and exactly what turbo you are comparing the GT series to..
Alot of people jumped on the GT band wagon in the rotary world, but failed to realize any magical gains over other older model turbos... The Gt3540 was supposed to be the 500 rwhp turbo, but I don't think anyone got near that on the 3540..
On a rotary, there is so much exhaust energy, the BB option really doesn't seem to really diminish spool time over standard bushing style bearings...
Check this out
http://www.catenet.net/graph.php?car...1&SUBMIT=GRAPH

The GT are not the fastest spooling, and are "within" the pack when it comes to HP... Some of the older models seem to work better than the GT, on the 13b, which seems to hit a back pressure wall on the GT series.. There are some refinements, but they are far from any kind of quantum leap in turbo technology..maxt

[Hollywood]

Originally posted by Maxt
I guess I will just add that it probably depends on the car and exactly what turbo you are comparing the GT series to..
Alot of people jumped on the GT band wagon in the rotary world, but failed to realize any magical gains over other older model turbos... The Gt3540 was supposed to be the 500 rwhp turbo, but I don't think anyone got near that on the 3540..
On a rotary, there is so much exhaust energy, the BB option really doesn't seem to really diminish spool time over standard bushing style bearings...
Check this out
http://www.catenet.net/graph.php?car...p;SUBMIT=GRAPH

The GT are not the fastest spooling, and are "within" the pack when it comes to HP... Some of the older models seem to work better than the GT, on the 13b, which seems to hit a back pressure wall on the GT series.. There are some refinements, but they are far from any kind of quantum leap in turbo technology..maxt

Roteries are a little differerent obviously and only make up a small percentage of whats on the road.

On that graph, you know the difference in porting in roteries make a huge difference yet only some ports are listed, just question marks on others, 1 port can mean totally different power compaired to another.

But the T88 aside as it power rage is considerably diferent than all the others, the next two on top are the T04S, and the GT 35/40, both which i mentioned above as being newer better technology then the 3rd id the apexi RX6, which again specializes in ball berring and better spooling wheels.

I'm not comparing GT's to other brands just compairing Garrett to Garrett. As if one is looking for ultamate turbos HKS's are very popular and they make their own housings.

[Maxt]

Most likely most of the motors are stock port or mild street porting, if someone has a bridgeport, they are probably not gonna be running those size turbos, they are pretty much all to small for a bridge to make it worthwhile..
Rotaries are only different from smaller 4 bangers in that they like a more exhaust flow than other similar sized engines....And thats part of the problem with the GT series, it seems Garrett has if anything tried to just improve spool characteristics, and they have matched their compressors to overall, smaller turbines , at the expense of top end flow...The gt 3540 is a decent comp, but on a T3 footprint and housing configuration, it chokes up early, this would also show up on a v-8 as well as a rotary, and thats where being able to use old T4 frames generally allows a user to tune to higher peaks than the GT so far.. If I was to run a T04e, I could cheaply and easily swap to about 8 different turbines to optimize the hots side.. Not so with the GT....Yet....Maxt

[Hollywood]

Originally posted by Maxt
Most likely most of the motors are stock port or mild street porting, if someone has a bridgeport, they are probably not gonna be running those size turbos, they are pretty much all to small for a bridge to make it worthwhile..
Rotaries are only different from smaller 4 bangers in that they like a more exhaust flow than other similar sized engines....And thats part of the problem with the GT series, it seems Garrett has if anything tried to just improve spool characteristics, and they have matched their compressors to overall, smaller turbines , at the expense of top end flow...The gt 3540 is a decent comp, but on a T3 footprint and housing configuration, it chokes up early, this would also show up on a v-8 as well as a rotary, and thats where being able to use old T4 frames generally allows a user to tune to higher peaks than the GT so far.. If I was to run a T04e, I could cheaply and easily swap to about 8 different turbines to optimize the hots side.. Not so with the GT....Yet....Maxt

Keep in mind many V-8's use twin turbos, this is where the GT's will shine. Not to mention the hybrid GT's, gt parts on other garretts.

Not everyone is tunning to the extreme (ie:full out T76 etc) but to prove to you, you tell me what turbo do you need for for 550whp on your car?

[milesmcewing]

I feel compelled to comment!

Please note I have put my comments in quotations after your original points, sorry that I don't know how to stick them as quotes. Please note that I am not trying to start a war, I am just adding my views, based on my experience.


Here is why GT turbos are better;

1. Improved Aerodynamics - The modern GT wheel is the result of decades of development and testing using the latest technology and tools.
-Many "T" applications are based upon older/outdated wheels from the previous decades.

"GT wheels are based on the same theories of airflow that the "T" series are based on, and the turbos dating to the 1930's, yes it is true they are using newer technology and tooling to build them, that doesn't make it better. Physics are still physics"

2. Better wheel match/ratio: Each turbo consists of a careful matched turbine and compressor wheel that is known to work extremely well together which also, allows the combination to reach the highest level of operating efficiency.
-Many "T" applications are randomly selected combinations based solely upon a compressor flow requirement or a turbine flow requirment in relationship to an engine size. As a result, a lot of "untested" combinations are used.

"Not necessarily better matches, Gt turbos are subject to the same people using your "randomly selected combinations" (only there are not as many combinations). We test many turbos for the manufacturers, our testing helps qualify these combinations for both series. Better matching to the requirements and application are key no matter whose turbo you use.:

3. The GT's larger A/R housing allows the turbo to reach peak turbine efficiency. Not only is backpressure reduced, but the increased turbine efficiency allows the turbo/engine to make better power across the entire RPM band. A large A/R "GT" Turbo with a good wheel combination will outperform a small A/R "T" in both spool-up and power.
- In many "T" applications, the selection process for the A/R size is influenced by the desire to have boost at a certain RPM range. Here, the tendency is to use a small A/R as an attempt to shift the boost curve to the lower RPM. As a result, the selected turbine wheel is not allowed to reach it's peak efficiency because of the small A/R. The overall result is a lazy turbo that is not efficient, a combination that only looks good on paper.

"A/R ratio is a mathematical calculation. (read Corky Bell or Hugh Macinnis for a detailed explanation) A larger A/R ratio is larger no matter what series you use. Using different A\R ratios to shift the boost curve is someones knowledge trying to match the turbo to your application, lazy and inefficient means you have the wrong guy matching your application. Buying the wrong GT series isn't going to work any better than buying the wrong "T" series."

4. The GT Ball Bearing makes a good turbo even better. The low friction design offers less drag on rotation and endures thrust much better than journal bearing turbos. Better transient boost response makes the turbo much more responsive during both cruising and wide open throttle driving conditions. By reaching full boost sooner, the GT Ball Bearing turbo makes more power available sooner, negating the need to "rev out" the engine constantly.

"GT ball-bearing turbos are suffering from many bearing failures, yes they can spool faster, but the tolerances required for operation at 120,000 RPM are very small, the bearings are much less tolerant of cheap oil, hot shutdowns, infrequent oil changes, and manufacturing defects. Think about this ' if ball-bearing design is so much better, how come crankshafts, connecting rods, and camshafts ride on bearing shells?' Even Formula one engines still use bushing technology. If you need to Rev out the engine constantly, yet again someone has mismatched the turbo for your application."

- Many "T" turbos can make the high peak HP numbers, but only the GT Ball Bearing turbos make the high HP and offer a power curve with a wider torque band that spreads the power across a more usable range. A high torque number is no good if it is reached 200 RPM before redline.

"The torque band is a function of the combined A\R, intake wheel, trim side, hot housing etc. etc. Yet again this statement supports the mismatch issue"

5. The last reason to switch to GT is: Its now easy to do with a drop in turbo design. No major reconfiguring of the turbo kit is necessary. In most cases, all major hardware such as manifold, downpipe, pressure pipes, etc. is retained.

"Not true, the bearing housing is considerably larger, most applications using "T" series turbos will need some fabrication to "drop in"



"Most of the statement you have provided point to a marketing sense, the GT series certainly is a refinement of the T series, however the bugs are not worked out yet. If you blow up a T series, usually you can rebuild the turbo, with the GT series, the cartridge is non-rebuildable. "

"Lastly, the most important factor in turbocharging is still getting someone who can identify your application and size the turbo to match your requirements, deal with a reputable shop and make sure when they ask you what you want you tell them truthfully, a lot of people call wanting a drag turbo with a million horsepower, try living with that unit everyday and you will be sorry (unless of course it is for a drag-only car)"

Cheers to all!