Turbo specifications clarifications

11-23-2003, 03:47 AM
Try saying that title 5 times fast. Sweet...

I recently got some PMs about turbo specs, like AR, trim, etc and how they affect performance. So I'm going to write up one of my technical novels here so every can benefit from the info and ask questions, or add to my explanation. ;)

Once you have decided what basic type of turbo you are gong to run, you need to firgure out the specifics. What I mean by that is, are you going to run a Mitsu turbo, a Garret turbo, or a combination of the two? The center section of the turbo you choose will determine what oil and water lines you need to make it work. A Mitsu turbo center section will bolt right on to a 1g, or a 2g using the feed line from all of the installation kits to add mitsu turbos to 2Gs. A garret center section will require oil/water line kit that goes with your turbo and car.

Once you know what center section the turbo will have, there is still compressor wheel, compressor housing, turbine wheel, and turbine houisng. What you choose here will DRASTICALLY affect the power potential of the turbo, as well as the lag, and what supporting mods you need to get for this turbo, which is VERY important. ;)

First we'll look at compressor wheels. The trim people often quote for the wheel is NOT the size of the wheel. It is simply the ratio of the quare of the size inducer (smaller diameter, that you see in the inlet) to the size of the exducer (the larger diameter, you can only see this when the wheel is not in a housing), times 100. So its inducer squared, divided by exducer squared, times 100. So a wheel that measure 50mm on the inducer and 65 mm on the exducer is a "59 trim." The trim of the wheel determines the flow and boost characteristics of the wheel. One tirm may be happy running high boost, but doesnt want to move a ton of air, while another trim may like to move a ton of air at low boost. Keep in mind that you can take one compressor wheel, double the size of the inducer and exducer, and the trim doesnt change, but one wheel is obviously much larger than the other. ;) Typical Mitsu wheels are the 9b, 13g, 14b, 15g, 16g, big16g, EVOIII 16g, 17c, 18g, 19c, 20g. The simplest way to explain the system is the number is the basic size, and the letter is the "trim." For example, the 15b, 15c, and 15g are the same basic size wheel, but the trim is different between them. For the TO4E wheels used in the T3/T4 turbos, you have the 40, 46, 50, 54, 47, 60, and 60-1 trims, in asending order.

The compressor housing will have a rating in "A/R." This is the ratio of the area of the nozzle to the radius of the volute, or some part of the housing. I'm not sure. Someone can look this up. The only thing you need to remember about AR is a lower number will have less lag but less flow capability, and a larger number means more lag, but more flow (and therefore more power) capacity. Typical housings are the Mitsu tdo5h found on the 14b through 19c size turbos, the tdo6 found on the 20g, and the "cyclone" cover found on the red, green, M50/60, etc. I'm not sure anyone knows the actual ARs of those housings, but they are in order from smallest to largest. For garret, you have the housng found on the t3/t4 steups. The compressor side is the T4 side. So you have the TO4B, TO4E, and TO4S (also called TS04), again from smallest to largest. I dont know the ARs of those housings, but the TSO4 is .70, which is considered very large.

The turbine housings are also rated in AR. Mitsu uses the 5cm (13g turbo found on 1g auto tranny cars), 6cm (found on 14b turbos from 5spd 1g), 7cm (found on 16g and up, used on reds that run into the nines), and 8cm housings found on large turbos. There are other sizes, but htey are rarely used. The 6cm equates to a .41 AR, the 7cm is a .49 AR, and the 8cm is a .57. Note how small these are compared to the garret housings. Typical T3 housings (the exhaust side of the turbo is the T3 in the T3/T4 combo) are the .48 and .63 housings. .63 is known to spool very well on our cars with large turbos, while the .82 is going to lag a bit more. There are other sizes as well. Its been said that the only way the mitsu turbos get away with such small housings is because thier turbine wheels are so good. Who knows.

Typical Mitsu turbine wheels are the TDO4 (13g), TDO5h (14b to 19x, custom 20Gs), TDO6 (20g), and TDO6H (20g). There is also the TDO7 25g stuff but we never use it. For the garret T3 wheels found in the T3/T4 turbos, there is the Stage 1 (also called "standard"), Stage 2, Stage 3, and Stage 5. Stage 3 is the most popular wheel used with DSMs, with stage 5 being too laggy or most to use. You will very rarely see a T4 turbine side on a DSM, but there is a whole slew of other wheels and housings in the T4 turbine family.

So the key points to take away from this:

1) Big AR flows more but lags mores, small AR is vice versa
2) Trim is not the size of the wheel, but how it will behave
3) T3 is the exhaust side of the turbo, to reduce lag. T4 is the compressor side for big flow
4) These parts can all be mixed and matched as you want to. This is why some turbos work, and other dont. Its all about a matched system.
5) A small turbine side will spool well, but will choke a large compressor side. A large turbine side will flow more, but will lag more, espeically on large compressors. It has to be matched.
6) The type of turbo combination you choose must not only be well matched in itself, but to your needs as well.
7) You MUST support the turbo you choose. What injectors, pump, IC, etc you use are ALL determined by what turbo you are running.
8) Look for a compressor wheels flow rate in Lbs/min. Multiply this number by 10 to get the horsepower capacity of that wheel. A 50 trim wheel moves up to 50 lbs/min, and well tuned will make about 500 hp. Etc.
9) Getting a turbo too large for your goals will lag more, but allow room to grow. A turbo too small will perform well but you may be wanting more before long. Its a tough balance.
10) as with anything else in life and physics, there is no free lunch, its all a comrpomise. Choose your weapon wisely. :)

This is a very basic overview. Feel free to ask more questions to get into some more of the specifics. :)

11-23-2003, 02:25 PM
u rock man.. thankz alot
this really helps and it will really help the others who are intrested in these thing. thankz again

11-23-2003, 09:20 PM
Let's just call 95 gsxracer the turbo god!:biggrin:

11-23-2003, 09:37 PM
Well, lets not get crazy now :D There are two interesting things to onte here. One is thats only a small part of what I have managed to leanr about turbos. The even scarier part is I still have a LOT more to learn. Just so you know what youre up against :lol: But it all starts somewhere. I always encourage poeple to read up as much as possible on this stuff, just be careful who you listen to. ;) Theres a lot of crap and missinformation out there.

11-23-2003, 10:50 PM
95 gsxracer i have a ? for you, im looking to get this turbo from dsmparts it's a gt-14. they say it a killer 1/4 turbo, BUT it says for those brave enough to run it, Do u think i should?


11-23-2003, 11:06 PM
I thought that description sounded a lot like SBR's, so I went to the site and sure enough they are reselling SBR turbos. :) Looks like they mark them up a bit. 100 bucks on that turbo ;) Jsut a heads up. Also, I dont like how they say the EVOIII 16g is the rarest turbo on the planet, when SBR had 20 of them sitting on the showroom floor when I drove down there last week. Sounds like hype. But at any rate, on to the turbo...

So that is a big wheel. Like the description says it is the largest wheel in the GT30 family, and is pratcially a GT40 wheel. In fact, you can get that same GT14 wheel with the GT40 turbine wheel, labeled the GT35R. It will lag. I have that compressor wheel in a Mitsu TDO6H setup right now, 7cm housing, "cyclone" compressor cover. I get full boost (25 psi on pump) at 4400 rpm. So its laggy. But its not bad. And it has a lot of potential when one is ready to take advantage. To take full advantage you need every part in the book. Professionally worked head, full 272s, sheetmetal intake, etc. It gets complicated, hence thier "for those who are brave enough" comment :)

When I get some time I can continue my write up above with the GT line of turbos, since they are a whole new animal...

11-23-2003, 11:10 PM
what kind of mods have you done to your engine...most likly with that turbo you will experiance so much lag, you will probably regret buying it... now if your engine is completly built it might be a different story... you will still get some lag but it has a better chance to reach full boost with a modded engine!!! shit thats a lot of money for a turbo too, plus they AirFlow/min your engine would never handle it! anyways i would suggest 16g or a 20g, much more realistic. peace

11-23-2003, 11:13 PM
thnks man.... ok so i street race alot and not so much as on the drag strip. so what turbo do you think i should get for street im thinking a 20g, so i dont have to much lag when i take off about 3000 rpm's in 2nd gear.

11-24-2003, 12:39 AM
thanks for all the info, but i have i question and i might have over looked the answer in your post thats is a lot to try to comprehend all at once. but any way why cant you pair a small exhast turbine with a big compressor wheel? thanks. :thumbsup:

11-24-2003, 03:45 AM
Having a built engine or stock engine, doesnt affect lag at all. If you increase compression in the process it helps slightly though, but you will knock more easily. My engine is fully "built" and I still dont get 25 psi until 4400 rpm as I said above, and people with stock motors are getting the same exact thing. ;) Only pussies cry about lag. If its not building boost fast enough, you are int he wrong gear anyway. You should never be below 5-6000 rpm if you are trying to go fast. ;) Dowshifting, the antilag. Not to mention that if you run DSmlink, anitlag is included. Big turbos dont have such a dissadvantage anymore, but correct sizing is still important.

For a badass street turbo I would recomend the SBR TDO6H 20g. Not the TDO5H, not the TDO6, the TDO6H. It still spools well (before 4000) but has tons of top end. About 999 setup for external gate IIRC. I borrowed one from SBR for a month or so and thats what I ran my 11s on. The guy that now has that turbo trapped 124 mph on a well setup car, which is good for low 11s. Lag wasnt nearly as noticeable as my current turbo.

Pairing a smal turbine side with a large compressor side is what the t3/t4 is. ;) Its also the key to 10 second 20g, the bushur tdo5h/20g. Thats a tdo5 turbione side with a tdo6 compressor side. Same idea as t3/t4. Same thing with the GT14 turbo, GT40 comp wheel with a smaller GT30 turbine wheel.

11-24-2003, 10:34 AM
Pairing a smal turbine side with a large compressor side is what the t3/t4 is. ;) Its also the key to 10 second 20g, the bushur tdo5h/20g. Thats a tdo5 turbione side with a tdo6 compressor side. Same idea as t3/t4. Same thing with the GT14 turbo, GT40 comp wheel with a smaller GT30 turbine wheel.

Once again 95GSXracer educates the ignorant. :worshippy . thanks again.

11-24-2003, 06:34 PM
looks like im going back to 20g the sbr 20g.. hehe unless i can figure out a better inducer/exducer,a\r and a nice trim that i can build for the gsx motor the sbr... hehe
thankz alot..
i did some equations form a old sport compact car mag that had the equations to find the right trim for you turbo and this is what i got can up please make some sence of it for me..
for 4g63 2.0l
pressure ratio-2.326
mass flow rate-37.86
the corrected mass flow rate is 40.18
so with all these numbers what does it equal to? how will this help to find the good sze turbo for the 4g63?
thanks alot

11-24-2003, 10:26 PM
That works out to a bout 20 psi, 400 crank HP. Smaller than a 20g. Those calcs are usuallyjunk when it comes to 4g63s. We run much bigger setups than we should for the size of our motors. ;) If you want alternatives to the TDO6H 20g, you can do something simialr to the M50 wihich is the same thing with a TO4E 50 trim compressor, and is the FP "Green." Or a full garret 50 trim t3/t4, with a TO4E comp cover, and a 63 AR turbine side with a stage 3 wheel. All good for ~450 whp either way...

11-25-2003, 05:36 PM
thanks alot man

02-07-2004, 01:34 PM
I've been researching a lot and buying parts when I find a good deal in hopes of turbocharging my VR6 this summer. I've made a small webpage that also explains some turbo stuff. check it out:

02-07-2004, 06:52 PM
and this is another thread that sould be stickied, or if kevin wants to cut and past into a bigger thread to be stickied, that would be great... ;)

02-07-2004, 11:09 PM
I was thinking about making one, when there is an active mod I will go ahead and link all of the best posts if it will be stickied.

02-08-2004, 12:14 AM
yeah that 20G sounds so nice with that explanation since my gs-t is a daily driver and occasional at the track but can my Gs-t handle the 20 seeing the torque steer and crappy tracktion at take off cuz of its front wheel drive set up?

02-08-2004, 12:22 AM
if you spend the money to get the proper suspension, take the time to make your chassis more rigid, and get some things that help eliminate wheel hop like solid motor mounts, i dont see why not. i also am not sure what all you would have to do to eliminate the problems presented by FWD. but if you get motor mounts and a suspension under your car i bet it would eliminate 80% of the problem. search the forum for some info on suspenison there is some really good threads on the topic.

EDIT>>>>> i forgot to mention that the way you launch your car has a lot to do with the way it reacts off the line.;)

02-08-2004, 12:33 AM
You can compensate for FWD with a some skill, and there are 600fwhp GS-T's.

02-08-2004, 04:00 AM
well i hear this talk about the 20G getting into the 11s range but can the gst do that?

02-08-2004, 06:13 AM
with proper suspension/tire setup, and good luanching, yes it can. Has it been done? Not sure ;)

02-08-2004, 07:14 PM
ok i got the tein flex coil overs for the suspension planning on some 18x8.5 tires LSD 20G turbo upgrade and a nice shot of nitrous oxide?

02-08-2004, 08:10 PM
You might want to re-think the nitrous set-up, it seems to be difficult to pull off with turbo, but if you're set on it, i'm sure it can be done. 18's are a little big for going fast, but it will look nice as you do it :)

Let's try to keep this thread on-topic as eventually I hope to have a sticky thread pointing to this thread as one of the more informative turbo posts.

02-08-2004, 08:52 PM
you guys want me to tell a mod to stick this thread? or is it not ready? and why dont we have a mod in our eclipse forum? we should have one...sorry off topic...

02-08-2004, 09:24 PM
Don't make this thread sticky, there would be 2 pages of stickied threads, we need a post that addresses topics and directs them to relevent threads. I'd make one, but I would hate to see it go down not stickied.

02-09-2004, 01:27 PM
somebody needs to copy and paste all the bare and bone info into one new thread... or a thread with links to the relavent threads, so that new links could be added as they come about, like book of contents, or a 'nOOb's look here first' thread...

05-02-2005, 04:37 AM
old school bump of the week :)

05-02-2005, 05:54 AM
Ah yes, the good old days when I wasn't a mod...

05-03-2005, 03:55 AM
Well i have learned alout from reading this post, but this also leaves me with questions. My goal is to run 400 WHP without breaking stuff every other day. i was thinking of putting the 18g comppressor side and the small 16g turbine side together. i have upgraded fuel system(255lph, fuel rail, 660cc's, FPR) Do you think this turbo will work?

05-03-2005, 04:01 AM
18Gs are typically TDO5H, which IS the 16g turbine side. 14b also. IMO, the 18g isnt worth it. For 400 whp I would start with at least a TDO6H 20g. You can do 400 comfortably. A EVO3 16g will do it on the ragged edge though to be fair.

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