T4 footprint and A/R questions...

[definitiveno]

So I always thought that with the t4 turbo's the same number A/R, .70 A/R for instance, would be bigger than say a T3 .70 A/R......is that true? I have looked around at T4's now and then and I have been looking at .58 and .63 T4 A/R's thinking that they would flow just as much as a T3 .82 A/R. Some one said some thing to that affect some were on some board one time and it's just recently occurred to me that was a horrible source for information


Thought I would look into this a little more. Can any one help me understand the difference here?

 

[damnslowtsi]

It should be safe to say that the same A/R T4 housings will be bigger than T3's. I don't think there are any hard numbers (spreadsheets etc.) out there to compare say .58 T4 to .82 T3 other than comparing performance on various set ups. If you are interested in those two then I *think* .82 T3 will outflow .58 T4. It also matters if the housing is divided or not. Divided ones are smaller for the same A/R. I 'll step aside now and see what others have to say since I 'm curious myself.

 

[nanokpsi]

According the PTE, the .68 t4 will flow more and spool slightly better than a .82 t3. I would go as far as to say the relationship of the .58 t4 to thge .63t3 would be the same. Its hard to say going much further than that as there are so many turbine housings on the market from a number of sellers.

 

[94Jettameowpsst]

The reason people will switch to a t4 turbo is because the turbine housing takes a lot more volume to fill it.
(if im wrong please correct me, i've had a few to drink
So a smaller ar on a full t4 turbo will produce the same if not better numbers on larger ar t3 housing because the exaust gasses arent as hot and not as compressed.

Think of blowing up a small balloon then blowing up a larger balloon the same amount.
It takes more force to blow up the smaller one than the larger one but yet there's the same amount of air in both.

This makes sense to me now ( i THINK im correct) but i have a feeling im going to look at this tomorrow and be like wtf >.<

 

[definitiveno]

The reason people will switch to a t4 turbo is because the turbine housing takes a lot more volume to fill it.
(if im wrong please correct me, i've had a few to drink
So a smaller ar on a full t4 turbo will produce the same if not better numbers on larger ar t3 housing because the exaust gasses arent as hot and not as compressed.

Think of blowing up a small balloon then blowing up a larger balloon the same amount.
It takes more force to blow up the smaller one than the larger one but yet there's the same amount of air in both.

This makes sense to me now ( i THINK im correct) but i have a feeling im going to look at this tomorrow and be like wtf >.<

Well, go ahead and check it out tomorrow and tell me what you think. I am not an expert so I usually have a wtf going on on a regular basis anyway. I feel like wtf right now.

 

[94Jettameowpsst]

Oof, well now that i look at this (please chime in if need be) but thats a pretty good description of why a smaller ar t4 will spool better than a larger ar t3.

 

[GVR4592]

Read the first thread in this forum, "Turbo Education Thread".

 

[definitiveno]

Read the first thread in this forum, "Turbo Education Thread".

hmmm, I have read all that before, several times. From what I can deduce there is no change in A/R going from t4 to t3, what-so-ever. Although you have a larger opening to meet your manifold the actual radius of your turbine housing hasn't changed since it needs to fit the same turbine wheel. However later on the next page I think I found where some one said that a .58 t4 flows more than a .68 t3. So there are contradictions and hence my questions.


I am not entirely confident on my understanding of radius and what dictates it's size either. Right now I think it is the size of the turbine wheel or some thing close and wouldn't change between T3 and T4 housings, but not sure though.

 

[GVR4592]

http://www.dsmtuners.com/forums/showpost.php?p=1670844&postcount=15

 

[definitiveno]

Thats the one I was reading from, , did you post that because I sound confused and should read it again?

 

[GVR4592]

I posted it because, in the picture it shows how they determine the radius. I wasn't sure if you had read that post or not. Are you trying to figure this out so you can choose between a T4 housing and a T3 housing?

 

[definitiveno]

I posted it because, in the picture it shows how they determine the radius. I wasn't sure if you had read that post or not. Are you trying to figure this out so you can choose between a T4 housing and a T3 housing?

Yes, possibly. My manifold maker stiffed me for another 2 weeks, for the third time......starting to look at other options now. I was looking at divided t3 but divided t4 is more prominent, so I am just trying to get a better understanding for the differences between the two. So what that says to me is that the exit hole on the turbine sets the ratio between area and radius and that radius should not change between t3 and t4. I am not sure about that last part about radius changing or not, I just assume for the dynamics of a turbine wheel the radius wouldn't change because the turbine housing needs to remain tolerantly close to the exducer in order for the fins to capitalize off of the gas energy.

 

[Low Impedance]

The reason people will switch to a t4 turbo is because the turbine housing takes a lot more volume to fill it.
(if im wrong please correct me, i've had a few to drink
So a smaller ar on a full t4 turbo will produce the same if not better numbers on larger ar t3 housing because the exaust gasses arent as hot and not as compressed.

Think of blowing up a small balloon then blowing up a larger balloon the same amount.
It takes more force to blow up the smaller one than the larger one but yet there's the same amount of air in both.

This makes sense to me now ( i THINK im correct) but i have a feeling im going to look at this tomorrow and be like wtf >.<

i dont feel as though this is entirely correct. Or at least the way to say is misleading. If you look really closely at the T2, T3, T4 or hell a T6, they are increasing in size. why is this? they are meant to handle more exhaust energy from the motor while maintaing a useable compressor side. so lets compare a T3 in a .63 and a T4 in a .63. I dont care if they dont produce in that number or not.

The T3 has a smaller exiting volume than the T4. Which is actually good for building power in the lower rpm range. I can explain why, but it will take more explaining than i care to. Just use google if you really want to know. The .63, meanwhile, tells us roughly how the turbo will respond in terms of boost threshold. The smaller the a/r ratio, usually creates a more rapidly spooling turbo which can get to the point where is almost too soon, or in cases too late. But the a/r ratio effects the peak power as well. The larger a/r is well, larger. The exhaust is less restricted and can flow better, meaning more power, but usually at the expense of a longer boost threashold. So lets look at the T4. Basically, is a larger version of the T3 with the same rules applying. Odds are you are looking alot of hig end power OR your engine is producing alot of exhaust gases and needs the larger housing to be controlled properly.

Ideally, you do not want the exhaust gases to become cooler. Actually, you should aim to get the opposite of this. The heat energy is what drives the turbine and helps maintain a good exhaust velocity. Same reason why too large of an exhaust and create a loss in power. (bigger is not always better)