exhaust A/R question
exhaust A/R question I was looking at some graphs at forced inductions web site. People are saying that a t-3 will not handle the flow of a v-8, and a t-4 is needed. Just for example lets use a t-3 .70 ar, a t-4 .68 and a t-3 .84. All with p-trim wheel. All three show that the initial radius is 64.5mm. The t-3 .70 a/r has an opening of 4.23 sq inches. The t-4 .68 has an opening of 3.76 sq inches
and the t-3 .84 has an opening of 4.40 sq inches So i guess my question is if My math tells me to use a turbo with around a .81 a/r does it really matter if i use a t3 .84 or an t4 .81? Or am I missing something? A/R is Area / Radius correct? So that if all three turbos start with the same radius then area is the only variable. With the examples above is the t-4 the fastest spooling but the quikest to max out? sorry about the wordy ness but i've been
my head about this and now I want to
So to any one who knows the answer 
and the t-3 .84 has an opening of 4.40 sq inches So i guess my question is if My math tells me to use a turbo with around a .81 a/r does it really matter if i use a t3 .84 or an t4 .81? Or am I missing something? A/R is Area / Radius correct? So that if all three turbos start with the same radius then area is the only variable. With the examples above is the t-4 the fastest spooling but the quikest to max out? sorry about the wordy ness but i've been
my head about this and now I want to
So to any one who knows the answer How did you calculate the intial radius of all three housings?? The T3's and T4 are physically way different in size not to mention the big T6's. Also how are you calculating the internal area of the housing''s volute??
http://www.forcedinductions.com/images/810009.gif is the t-3 .70 ar
http://www.forcedinductions.com/images/810015.gif is the t-4 .68 ar
the 64.5 is showing a radius from the center of the turbine to the center of the inlet. on both. for area I only used the 43.00mm tall opening by 63.5 for the t-3 of the inlet flange and the 43mm tall by 56.5 mm of the t-4. I then drew out both flanges overlapping and the inlet on the t-3 is just slighty larger than the t-4, but the t-4 flange is way bigger. AMybe the numbers i'm working with are wrong?
http://www.forcedinductions.com/images/810015.gif is the t-4 .68 ar
the 64.5 is showing a radius from the center of the turbine to the center of the inlet. on both. for area I only used the 43.00mm tall opening by 63.5 for the t-3 of the inlet flange and the 43mm tall by 56.5 mm of the t-4. I then drew out both flanges overlapping and the inlet on the t-3 is just slighty larger than the t-4, but the t-4 flange is way bigger. AMybe the numbers i'm working with are wrong?
But as the radius gets smaller doesn't the area get smaller in relashionship. Hence the A/R I wish I had a t-3 .84 and a t-4 .81 in my hands but the best I could do is find some pictures online. I used a scaled ruler and I find that everything outside of the flange size appears the same?
Also you said the area is the volume? Isn't area 2 dimentions and volume three? so as the radius decreases around the turbine the area should decrease in proportion as the A/R ?
Sorry volume is 3D, you are correct, but that is how Garrett describes it, so that is my fault. Also their is no way by using a ruler you can find internal volume of the housing. Have you looked inside a T3 and T4 housing?? You will see the flange size has nothing to do with internal area. Also the MP units you refer to 1 is divided flange other is undivided. How are you calculating the divide into the total area??
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I can see your point on the divied vs undevided flange. I was thinking that there was a small amount of overlap between sizes like the t-3 start real small, like .45 ar and Ive seen as large as an .96 t-3 which was larger than I thought existed. Before I thought .84 was the largest. Then the t-4 comes in with a .68 .81 .96 1.05 and so on. Then there would be an overlap between t-4 and t-6's. I don't know anymore cause I've been running a custom sts type turbo with a t3 .84 and It seems to work just fine, I do need to take some exhaust pressure measurments to see what my pressure ratio is. Like many others with the sts which run t-4's I'm at full boost around 3k and it starts boost around 2.4k Again thanks for all your info I do appreciate it, I'm trying to learn as much as I can.
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