Honda D Series Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
2,022 Posts
Discussion Starter #1
hey guys i pulled the turbo apart to measure the wheels to see exactly what i have and im no genius at math so the conversions for finding out the trim are eluding me. ive found how to do it and everything but its confusing me.


if you guys know how or are better than i am at it would you mind to help me out?


here are the number i got from it in inches an mm

cold side

big end 2.753 inches or 69.93 mm
small end 2.15 inches or 54.45 mm


hot side

big end 2.565 inches or 65.12 mm
small end 2.093 inches or 54.69 mm


hope that helps and that someone can figure it out for me cuase its telling me its a 77 trim on one side and above an 80 on the other.


thanks guys.
 

·
Registered
Joined
·
13,322 Posts
Turbo Systems 102 (Advanced)

Please thoroughly review and have a good understanding of Turbo Systems 101- Basic prior to reading this section. The following areas will be covered in the Turbo System 102 - Advanced section:

1. Wheel trim topic coverage

2. Understanding turbine housing A/R and housing sizing

3. Different types of manifolds (advantages/disadvantages log style vs. equal length)

4. Compression ratio with boost

5. Air/Fuel Ratio tuning: Rich v. Lean, why lean makes more power but is more dangerous

1. Wheel trim topic coverage

Trim is a common term used when talking about or describing turbochargers. For example, you may hear someone say "I have a GT2871R ' 56 Trim ' turbocharger. What is 'Trim?' Trim is a term to express the relationship between the inducer* and exducer* of both turbine and compressor wheels. More accurately, it is an area ratio.

* The inducer diameter is defined as the diameter where the air enters the wheel, whereas the exducer diameter is defined as the diameter where the air exits the wheel.

Based on aerodynamics and air entry paths, the inducer for a compressor wheel is the smaller diameter. For turbine wheels, the inducer it is the larger diameter (see Figure 1.)
inducer and exducer diameter of compressor and turbine wheels
Figure 1. Illustration of the inducer and exducer diameter of compressor and turbine wheels



Back To Top

Example #1: GT2871R turbocharger (Garrett part number 743347-2) has a compressor wheel with the below dimensions. What is the trim of the compressor wheel?

Inducer diameter = 53.1mm
Exducer diameter = 71.0mm



Example #2: GT2871R turbocharger (part # 743347-1) has a compressor wheel with an exducer diameter of 71.0mm and a trim of 48. What is the inducer diameter of the compressor wheel?

Exducer diameter = 71.0mm
Trim = 48



The trim of a wheel, whether compressor or turbine, affects performance by shifting the airflow capacity. All other factors held constant, a higher trim wheel will flow more than a smaller trim wheel.

However, it is important to note that very often all other factors are not held constant. So just because a wheel is a larger trim does not necessarily mean that it will flow more.
Back To Top

2. Understanding housing sizing: A/R

A/R (Area/Radius) describes a geometric characteristic of all compressor and turbine housings. Technically, it is defined as:

the inlet (or, for compressor housings, the discharge) cross-sectional area divided by the radius from the turbo centerline to the centroid of that area (see Figure 2.).
compressor housing showing A/R characteristic
Figure 2. Illustration of compressor housing showing A/R characteristic



The A/R parameter has different effects on the compressor and turbine performance, as outlined below.

Compressor A/R - Compressor performance is comparatively insensitive to changes in A/R. Larger A/R housings are sometimes used to optimize performance of low boost applications, and smaller A/R are used for high boost applications. However, as this influence of A/R on compressor performance is minor, there are not A/R options available for compressor housings.

Turbine A/R - Turbine performance is greatly affected by changing the A/R of the housing, as it is used to adjust the flow capacity of the turbine. Using a smaller A/R will increase the exhaust gas velocity into the turbine wheel. This provides increased turbine power at lower engine speeds, resulting in a quicker boost rise. However, a small A/R also causes the flow to enter the wheel more tangentially, which reduces the ultimate flow capacity of the turbine wheel. This will tend to increase exhaust backpressure and hence reduce the engine's ability to "breathe" effectively at high RPM, adversely affecting peak engine power.

Conversely, using a larger A/R will lower exhaust gas velocity, and delay boost rise. The flow in a larger A/R housing enters the wheel in a more radial fashion, increasing the wheel's effective flow capacity, resulting in lower backpressure and better power at higher engine speeds.

When deciding between A/R options, be realistic with the intended vehicle use and use the A/R to bias the performance toward the desired powerband characteristic.

Here's a simplistic look at comparing turbine housing geometry with different applications. By comparing different turbine housing A/R, it is often possible to determine the intended use of the system.

Imagine two 3.5L engines both using GT30R turbochargers. The only difference between the two engines is a different turbine housing A/R; otherwise the two engines are identical:
1. Engine #1 has turbine housing with an A/R of 0.63
2. Engine #2 has a turbine housing with an A/R of 1.06.

What can we infer about the intended use and the turbocharger matching for each engine?

Engine#1: This engine is using a smaller A/R turbine housing (0.63) thus biased more towards low-end torque and optimal boost response. Many would describe this as being more "fun" to drive on the street, as normal daily driving habits tend to favor transient response. However, at higher engine speeds, this smaller A/R housing will result in high backpressure, which can result in a loss of top end power. This type of engine performance is desirable for street applications where the low speed boost response and transient conditions are more important than top end power.

Engine #2: This engine is using a larger A/R turbine housing (1.06) and is biased towards peak horsepower, while sacrificing transient response and torque at very low engine speeds. The larger A/R turbine housing will continue to minimize backpressure at high rpm, to the benefit of engine peak power. On the other hand, this will also raise the engine speed at which the turbo can provide boost, increasing time to boost. The performance of Engine #2 is more desirable for racing applications than Engine #1 since Engine #2 will be operating at high engine speeds most of the time.
 

·
Registered
Joined
·
2,022 Posts
Discussion Starter #3 (Edited)
yea i saw all that and was trying to plug the numbers but its giving me crazy return numbers this lil turbo is not a 77 trim on the cold side but thats what it keeps telling me.

the turbo in question is a garrett t3/t4 with a p trim cold side wheel and a stage 3 hot side wheel and the compressor cover is a 4 inch one the hot side says .58 ar and the cold says .60 i was told when i purchased it that its a 60 trim.


btw its the turbo in my pic
 

·
Registered
Joined
·
764 Posts
It looks like you have T04B V trim compressor with a Stage 2 T3 turbine. No body's measurements are 100% correct so it is hard to say 100%.

The V trim is pretty decent compressor. Should easily support 400hp.
 

·
Registered
Joined
·
2,022 Posts
Discussion Starter #6
you were right mhamrick it is a damn v trim guy who sold it to me bent me right over cause i didnt know the difference. lesson learned i guess.
 

·
Registered
Joined
·
764 Posts
It depends on several things. You may actually be able to push it that far. I quoted around 44 lb min at 14.7 psi so it also depends on psi you run. You will be working it harder then 2 dollar corner hooker on tax return day but you may be able to make it 8k.
 

·
Registered
Joined
·
2,022 Posts
Discussion Starter #8
see i was selling it to a guy from here and i was telling him the specs i was given when i bought it so i was told it was a 60 trim and blah blah blah and obviously it isnt and it pisses me right off wish i had known sooner. i would have got a refund. but alas now im boned i cant use it and noone seems to want it. worst part is it a brand new turbo.
 
1 - 8 of 8 Posts
Top