Turbochargers are a pivotal performance component to the srt4. In order to accurately compare which turbo is best is a very complicated and bias concept. I have been asked countless times what turbo is the best for our car, which turbo is bigger, etc. I have decided to give a fair layout, on which turbo is which, in a fair and unbiased means of measurement.
Before jumping to a “what’s the biggest snail I can run” question, lets get a few pieces of information out of the way. It is important to understand the fundamentals of turbochargers and how they work. Now I'm not going to explain the in’s and out’s of how turbochargers work, but will instead just give you the basics on what’s important here. A compressor wheel is a finned wheel that compresses the air going into the motor. There are 2 major measurements on this wheel. You have the inducer and the exducer. The inducer is the smaller diameter measurement, measured from the top of the wheel. This is where the air comes into the compressor housing. The exducer measurement is the larger one, or at the base of the vanes. See below for clarification.
The next question I get asked is, “What is turbo trim?” the simple answer is that it’s just a mathematical equation based on the comparison of inducer and exducer sizes. The exact measurement is (inducer/exducer)^2x100
The larger inducer size, the more air can get into and therefore out of the turbo. This is awesome because a larger inducer means more power. It allows more air to be ingested. It’s like drinking through a straw (your intake being the straw). A large McDonalds straw brings in air a lot faster than a skinny coffee straw. So why don’t you just cram the largest inducer wheel possible into the housing? Good question. There is a down side of cramming more air into, and therefore out of, the turbo. Surge becomes an issue with too much air. Surge is when the turbo flows more air than your motor can take at any specific rpm. This is a very bad thing because it causes air to back up into the housing and can actually damage the turbo.
So what is the benefit of running a larger exducer dimension? Exducer sizing has more to do with actual spool up time over power ability. The larger the exducer, the quicker the spool. This works because the circumference becomes longer when the radius increases. This “longer travel” increases velocity of the surface edge of the wheel. This increased velocity helps to fling the air out of the turbo at a greater rate of speed.
Turbine housing is important as well, but not in the same way. All the air that goes into the motor has to come out. All that air is pushed through the exhaust and through the turbine housing. A smaller wheel is going to allow quicker spool, but will sacrifice top end because of the limited amount of flow. A larger wheel won’t spool as quickly but will allow more power because there is less restriction. A larger wheel will also help keep egt’s down because there will be less exhaust backpressure in the manifold. The trick is to find the smallest wheel that will flow the power you need it to flow.
Now onto the stuff you all want to know. Turbo sizing. There are 2 main styles of measurement. First up, is the Mitsubishi way. A typical Mitsubishi turbo nomenclature is TD05HR-16G-9.8cm^2 (early EVO VIII turbo). Lets break this down so its not gibberish. TD05 is the turbine housing; it’s a TD05 (see below for sizing). The “H” is for the type of blade (5 equal blades, 5 staggered blades, 6 standard blade, 6 staggered blade, etc.). The “R” stands for reverse rotation (clockwise for standard, counter-clockwise for reverse). The next set of numbers, “16g” in this case, is the compressor wheel housing (see below for actual measurements). The last set of numbers (9.8cm^2} is the measurement of the A/R of the housing.
Some quick measurements
TD04 ~ 1.81”
TD05 ~ 2.22”
The next set of numbers is the Garrett GT names. Take, for example, a GT2860RS. “GT” refers to the family. “28” is the turbine exducer measurement, or similar to the above Mitsubishi measurement, just a means of informing you of the turbine size. The next set of numbers is the compressor exducer measurement. 60 is the actual measurement, measured in mm (And remember mm to in conversion is mm/25.4=in
). The “R” means its ball bearing, and the “S” is a means of differentiating a higher flowing turbo assembly (note larger inducer measurement). A couple side notes. If the compressor hosing is larger than 100mm the 1 is omitted and simply labeled as the last 2 digits.
Some quick facts
GT28 ~ 2.10”
GT28 ~ 2.20”
GT30 ~ 2.36”
GT35 ~ 2.68”
GT40 ~ 3.03”
GT42 ~ 3.23”
Just for the record, Turbonetics likes to confuse the matters a bit. they alter their numbering a hair. they do resemble the Mitsubishi naming, but slightly larger wheels.
T3 ~ 2.32"
T4 ~ 2.92"
ITS TURBO TIME!!!!!!
MOPAR
Stock TD04-16G – 300hp seems to be the hp goal for this baby
Inducer: 1.71”
Exducer: 2.21”
Mopar Stage3 TD05-15G – 350 is easy, 400hp is the goal for this one. Crappy manifold design seems to be the limiting factor here
Inducer: 1.94
Exducer: 2.56
MITSUBISHI
Mitsubishi 16G6 (EVO. VIII wheel) – same as the stage3, 400hp seems to be the goal
Inducer: 1.89”
Exducer: 2.68”
Mitsubishi 20G-R – 400hp on pump is doable
Inducer: 2.04”
Exducer: 2.67”
AGP
AGP 50 trim – 450 is reasonable and mid 11’s are commonplace
Inducer: 2.12”
Exducer: 2.95”
AGP 57 trim – see above, not recommended because of surging issues
Inducer: 2.23”
Exducer: 2.95”
AGP 60 trim – 475 is achieveable, really shines in mid to high range
Inducer: 2.29”
Exducer: 2.95"
GT3147 – 400 hp is a healthy number on this snail
Inducer: 2.03”
Exducer: 2.67”
GT3071 – 425hp and a decent spool up time
Inducer: 1.77”
Exducer: 2.80”
GT3076 – 425hp on pump, nearly 100hp more on 110 octane
Inducer: 2.23”
Exducer: 2.99”
GT3082 – 600hp is doable
Inducer: 2.42”
Exducer: 3.23”
GT3582 “GT35R” – 40psi??? need we say more?
Inducer: 2.42”
Exducer: 3.23
T3/T67 - the only saving grace on this turbo is the baby turbine wheel
Inducer: 3.02"
Exducer: 4.03"
HAHN
Hahn Super16g – 350hp and near stock spool time!!!
Inducer: 1.83”
Exducer: 2.36”
Hahn Super 20g – look forward to near 400hp with this beauty
Inducer: 2.07”
Exducer: 2.67”
