Garrett turbo Q

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crushers said:
hey, dumb arrogant fawk, i leave the mapping to the pros since ****s like you shoot off their uneducated mouths misleading the masses with your posts...
if i want info then people like you are the last i would go to...actually, people like you are the ones i stay away from...
you open up a book or a site, find out the AR ratio and post it up like you actually know something... big deal.

most of the Kiwis i have met on line are knowledgable, friendly and helpful but i guess there are asses in every country.
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If there is a problem with the information I provide, then feel free to correct me. I am not only educated, but also qualified in this subject.
But I do not believe you have enough knowledge or experience on the topic to do so.

It's difficult to be friendly and helpful when advice given through experience, education and application gets shouted down by people who have no understanding of the matter and pay others to solve their problems.
 
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Dougal said:
Turbos are driven by exhaust flow. That requires both engine speed and load. At full load there is a rpm where any given turbo will start to produce boost. That is what we have been talking about.
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Yes, but the rpm at which boost comes on will vary depending on how large the exhaust A/R is. The bigger the A/R the slower the boost comes on (later in the rpm curve) but you also get less backpressure as you approach the engines red line.

With a smaller A/R the boost comes on sooner but it suffers from more back pressure at the higher rpm's.
 
cruiser_guy said:
Yes, but the rpm at which boost comes on will vary depending on how large the exhaust A/R is. The bigger the A/R the slower the boost comes on (later in the rpm curve) but you also get less backpressure as you approach the engines red line.

With a smaller A/R the boost comes on sooner but it suffers from more back pressure at the higher rpm's.
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You'll notice that I specified both the turbo and the exhaust A/R before discussing RPM's.
 
Yikes, this is just a nasty thread to read through. If you don't agree with a post, pick on the information... not the author. Ohh yeah, the T25 with the .48 turbine would be a great fit. I hooked up a t25 with a .63 hot side off of a talon and got full boost (8lbs) at around 2000rpm. And for the mentally challenged out there... YES THAT WAS AT FULL LOAD... duhh.
 
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okay, Dougal, after spending a night reading you many varied posts (correct me if i am wrong) you have done a bit of studying on the matter of turbos but you still have not achieved your goal of getting the trubo built to what you want. yet you are critical of me going to a shop and getting one designed right the first time by people that actually do this for a living and know what they are talking about...also interesting is anyone that hides behind a fake name and is reluctant to reveal who they are in real life.
interesting.

Gerg, after reading your few confusing posts it is obvious you have little experience at all. curious oh wise one, how did you achieve FULL LOAD? never mind anwering, i couldn't care less.

turbos are designed to behave a certain way, people go to school to learn this stuff and are paid well to do their job afterward.

here is what i have to add to this thread, if you want it done right, go to the pros. if you want to invest countless hours grabbing used turbos and mixing parts to try and achieve the goal then go for it. in the end it is cheaper, faster and much more accurate to do it right the first time. mapped turbos work... simple as that.

BTW, the turbos i use are Garrett turbos (which is the only reason i opened this thread)

i will leave the rest of you to stumble along in the dark with Gerg and Dougal...
 
crushers said:
okay, Dougal, after spending a night reading you many varied posts (correct me if i am wrong) you have done a bit of studying on the matter of turbos but you still have not achieved your goal of getting the trubo built to what you want.
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Yes you are wrong, I have no idea what you are referring to?
The Garrett T25 is the best possible single turbo match for my engine.


crushers said:
yet you are critical of me going to a shop and getting one designed right the first time by people that actually do this for a living and know what they are talking about
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You pay to get it done because you lack the knowledge and skills to match a turbo yourself. This same lack of knowledge and skill is what you're portraying here while at the same time claiming to know more than others who have succeeded where you couldn't.

crushers said:
..also interesting is anyone that hides behind a fake name and is reluctant to reveal who they are in real life.
interesting.
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Who is this person hiding behind a fake name?
Dougal is my real name, I bet "crushers" isn't yours.
 
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Ok guys let's settle down a bit. I don't think there should be such an argument between the "DIY" or the "customer" philosophies, both have their pros and cons obviously ? I think what Dougal is trying to say (correct me if I'm wrong), is that numbers do not say everything when you're trying to build your own setup. Better yet the magic A/R ratio is just that, a ratio, and is only meaningful when comparing turbos in the very same family and size. Because turbos are designed for full-load, and the A/F does not vary much from an engine to another in full load operation, turbocompressor designs and sizing are most often well balanced between the hot and cold side.
Now to Dougal's point : you have to decide what is more important for a DIY turbo setup between :
1. a good low-end response without choking the engine in the revs :"sizing by the turbine"
or
2. obtain the best efficiency compressing the air (within a couple %) : "sizing by the compressor"
 
Dude, get back on your lithium before you completely loose it. Yes it is true I have little experience or wisdom, but I have mated a t25 to my 3B, increasing the fuel to achieve 1150F max egt, climbing the snow shed in the middle of summer and observing 10lbs boost at 2000rpm.
 
denis said:
Now to Dougal's point : you have to decide what is more important for a DIY turbo setup between :
1. a good low-end response without choking the engine in the revs :"sizing by the turbine"
or
2. obtain the best efficiency compressing the air (within a couple %) : "sizing by the compressor"
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Well actually both are necessary. But for a diesel of the 3B size the T25 with 0.48 A/R turbine and 45 trim compressor is ideal. The 45 trim is the compressor sizing, the compressor A/R ratio means little.
Luckily this turbo is commonly fitted to 1.8 and 2L petrol engines so they're freely available secondhand.

My point with the compressor A/R is that manufacturers don't give you any choice because it makes no difference. They fix the trim (which sets the airflow) and manufacture the compressor housing with the appropriate A/R to suit.
In the case of the bog standard T25, the 45 trim compressor comes with a .49" A/R compressor housing.

If you want a bigger T25, you can get one with a 74 trim, it has a 0.8 A/R compressor housing but is not suitable at all for a diesel as it cannot provide boost at low airflow (runs into surge).
 
Moe R said:
Do any of guys water cool your turbos?Or is that overkill on a 3B?
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It is not necessary on a diesel, factory diesel turbos seldom have water cooling lines, when they do it's because the turbo is commonly fitted to a petrol engine.

The water cooling lines are only to help cool the bearing housing after a hot shut-down, hot shut downs are best avoided anyway.
But do make sure you don't plug the coolant ports completely, the air in there needs to expand and contract.
 
Moe R said:
When it comes to exaust size is 2 1/4" good would 2 1/5" be better with a GT25 ?
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I guess you meant to write 2 1/2"?;)

2 1/4" works fine, that's what is on my truck with a slightly bigger engine than the 3B. But I have yet to measure backpressure downstream of the turbo. I've measured exhaust backpressure upstream of the turbo, it didn't increase with engine speed which indicates everything is rosy.

The choice of muffler will have the biggest effect on exhaust backpressure. If you are putting in a new exhaust and 2.5" will fit then I'd do that.
 
Thanks, I did mean 2 1/2 :)
I'm thinking no muffler, straight pipe with a few bends all the way to the rear. Since I won't have the DIY thing going I'm going to seek a turbo kit. Looks like turboglide or AXT are the major companies. Can you or anyone else offer any opinions? Thanks again.
 
Moe R said:
Thanks, I did mean 2 1/2 :)
I'm thinking no muffler, straight pipe with a few bends all the way to the rear. Since I won't have the DIY thing going I'm going to seek a turbo kit. Looks like turboglide or AXT are the major companies. Can you or anyone else offer any opinions? Thanks again.
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The major components in a kit are the turbo and the manifold. If you can find a manifold then the rest is really easy and you'll save thousands.
Any exhaust shop can do the fabrication of exhaust and intake pipes.
The same places can usually plumb in oil supply and return for the turbo.
 
Pretty interesting thread .. :D

I'm too late .. but after plenty of reading about this theme on books and net .. I believe, to have a perfect turbo for your engine you must need to know some issues about your aplication and engine ..

Like a

Flow rate at peak torque rpm .. efective power band and air flo on this power band in your engine .. with this information also need the flow rate that your engine need thought this range to archive 100% VE or closer ..

And with this info you finally can decide which turbo you gonna use ..

At time you can archive a .58 or bigger turbine AR with a special trimm and swap a shorter compresor AR to allow your turbo setup produce boost as soon as you want with little low back pressure cheating you in the exhaust section ..
 
Tapage said:
At time you can archive a .58 or bigger turbine AR with a special trimm and swap a shorter compresor AR to allow your turbo setup produce boost as soon as you want with little low back pressure cheating you in the exhaust section ..
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A small A/R compressor housing will not produce boost sooner.
 
All your talking is really interesting. But i am seriously lacking time right now to dig and search.....if someone could simply hand me the right turbo with the invoice i'd be happy to pay...lol.

Ho well, i will start looking local add here.
 
This guy has two garett GT25r, he is asking 1500$ brand new, sound high. But maybe the right turbo. for me
 
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