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Old 03-01-2001, 04:09 PM   #1
RS-LOVER
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Question Difference between Turbos?

I'm sure this has been answered before, but what is the difference between a t28,T3,T4,T3/T4. I know that there by different companies, but what is the differnce in size, spool up time,compatabilty,max hp,max psi.
I'm lloking to get one soon, but there are so many to choose from.
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Old 03-01-2001, 06:21 PM   #2
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Heres a general guideline:

T28 Garrett- correct size for the 2.5RS
T3+ Garrett- Too big, late spool up, capable of supplying more power than your stock internals will hold up to.

Kevin
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Old 03-01-2001, 06:34 PM   #3
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there are too many different variations of each one (t28, t3,t4,etc.) You can hybrid each one to what you need within their capabilities.
With a ~10:1 compression car you do not want a small turbo. A t28 might give you 300hp, but you will have to run a lot of boost. Ok, it will spool up quicker but, higher boost means higher heat, which can hurt you engine.
Lets just presume a T28 will make 300 hp at 20psi, for argument sake! This is just so you can get an idea. A T3/T4 would make that same power at lower boost levels, say 8-10, where the turbo is still very efficient. It might not spool up as quickly as a T28, but on pump gas, its the better way to go.
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Old 03-01-2001, 08:20 PM   #4
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I think Shiv would have to argue w/ you about a T3 being to much for the engine internals(transmission, probably, but not the engine)... Trey would probably disagree too. I've talked to him and he seems fairly confident in the stock engine... I have to agree that the most important part is the engine management. Check out www.vishnuperformance.com There's lots of great info there, and I plan on calling shiv soon and getting fairly technical... I'll probably be posting on there what I find out...
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Old 03-01-2001, 09:23 PM   #5
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Why would you want a turbo that falls out of it effcient range well before redline? The T-28 runs out of steam 5300ish from the posts I have read from current users. Won't you just be generating more heat at higher RPM's without as much power as the T3?

Aaron
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Old 03-01-2001, 09:37 PM   #6
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ive never seen a t28 run out of steam.i have a little IHIrb5 turbo on my rs and it pulls like a madman to redline.its all in how you set it up,engine managment.after several hard runs (hours)my IC is still cold.and EGTs are very low.but yes my turbo is a little small for a 2.5 but i made the best of it and i like it.
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Old 03-01-2001, 09:39 PM   #7
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and a t3 is NOT to big.
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Old 03-01-2001, 10:14 PM   #8
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FWIW several of the turbo calculators come back with the t3 as the proper size for our displacement and redline. t28 is undersized really, It might be okay for low boost but if you want serious power a larger turbo is a better choice. If you're really worried about spool up, buy a ball bearing turbo.
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Old 03-01-2001, 11:10 PM   #9
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Like ASR was saying, there are many "hybrids" out there that have a custom intake and exhaust turbine specs.

So you really can't generalize and say the t28 is better than a t3 until you compare the a/r rating.
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Old 03-02-2001, 03:29 AM   #10
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The specialists that i know at Bill Bryan subaru said that the engine internals are excellent.The couple week parts are:
The Clutch and flywheel, and the piston rod bearings. The most HP that is recommended for daily reliability is 230-240. 290-300 things start breaking.On a stock 2.5 engine that is.
I want about 250-275 with my turbo...Eventually.
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Old 03-02-2001, 07:47 AM   #11
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T3/T4 is not too big for this motor. I'm making full boost by about 3500, too, with my 'too big' turbo. Yeah the turbo can make more power than a stock EJ25 can reliably hold, but if you aren't making the boost it ain't a problem.
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Old 03-03-2001, 01:20 AM   #12
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If the turbo can make way more boost than your car can handle, why not use a slightly smaller one so that you're taking advantage of the turbo in its effecient range?
The small IHI may be a good choice for people who want to auto-x, and the T3/T4 is probably a better choice for the drag strip.
That said, I'm getting the larger IHI ball bearing ~T3 in size. 3500 seems too late for a turbo to come on in our cars considering we have such a low rev limit. My eclipse GSX would come on about 3K, and you could ride it to 7K.
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Old 03-03-2001, 01:33 AM   #13
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Here's a crazy idea-- why not discuss the current GT series Garretts instead of the old rebuilt ones?
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Old 03-03-2001, 01:51 AM   #14
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Is suppose you could talk about those if you dont mind paying [ Dr. Evil Voice ] ONE MILLION DOLLARS [/ Dr. Evil Voice ] for it.

Most people talk about the old series because they are buying remanufactured/rebuilt turbos.

Why are we still talking about RHB series turbos instead of RHE's and RHF's?


[This message has been edited by blaster88 (edited March 02, 2001).]
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Old 03-03-2001, 12:19 PM   #15
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Check any turbo builder that can map a compressor and they will tell you the correct size turbo for the 2.5l IS THE T-28!
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Old 03-03-2001, 12:33 PM   #16
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The T3/4 turbos are not too big whatsoever. All of the honda turbo kits use these, and their motors dont even start to pull hard all-motor until 4,000 rpms where ours 2.5's really shine. We have the low end already from the 2.5 engine, so use a small turbo to kick in maybe 400 rpms early(NO point).

Another thing. Wouldn't you want to let the restrictive 2.5RS breathe more at high rpms.

A little sidenote: If all you are doing is running like a stage 1 turbo kit, then save the extra 300 buck or so and get the bigger of the turbo options. Since you can only run 3-5 psi of boost, this will act like 7-9psi on a smaller turbo, so go figure. Also get a ball bearing as these will spool up noticeably faster, maybe 500 rpms quicker at least.

PEACE

Bigger turbos are Better, so shut up
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Old 03-03-2001, 02:03 PM   #17
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Let's not forget about cfm. A T3/T4 turbo, most popular in aftermarket EJ25 turbo kits flows about 100 cfm more than T3, and probably even more than T28.

What does this mean? It means it will make more power with less boost. If the turbo is ball bearing quipped, the difference in turbo lag will be negligible, especially on a comparibly big engine like the EJ25.

Whatever a T28 does, the T3/T4 will simply do better, pound for pound, rpm for rpm, with very little sacrifice of bottom end power.

The secret to getting a T3/T4 to perform its best is your basic airflow mods to the engine.

Quote:
T3+ Garrett- Too big, late spool up, capable of supplying more power than your stock internals will hold up to.
Big? Yes, too big? No. It being able to supply more power than your engine can take means 2 things:

1. You will be able to make similar power with less boost pressure, which will reduce strain on the turbo as well as improved adiabatic efficiency.

2. It will most likely be the last turbo you ever buy; you can modify your car to the limits of streetabilty and your turbo will still be able to handle it.

Quote:
If the turbo can make way more boost than your car can handle, why not use a slightly smaller one so that you're taking advantage of the turbo in its effecient range?
The small IHI may be a good choice for people who want to auto-x, and the T3/T4 is probably a better choice for the drag strip.
That really depends on how much power you plan on running. The auto x 4 cylinder cars I have seen never encounter any lag problems with their T3/T4s.

Quote:
Duh! we are not talking about freakin' Hondas here! The boxer engine is a high torque, low revving engine that requires a quick spool up to get the best gains out of.
Well that is what the T3/T4 is best at. It delivers a quick spool up due to its small turbine section and big cfm for the top end. Just because the EJ25 is a low revving engine in stock form doesn't mean it has to stay that way.

Quote:
Put a t-28 with the same set-up as a t3 and Ill smoke your car all the way down the 1/4 mile. I recall someone racing a t3(2.5l) against a 1.8l 2wd Subie w/ an IHI and still beat him by .5 seconds!! HAHAHAHA!!
Can we say "driver skill"? There is also the issue of how much boost and modifications each engine had.
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Old 03-03-2001, 02:11 PM   #18
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Mike, call up any "turbo manufacturer" and ask them what turbo-charger you should use for a 2.5l 4cyl. They will tell you "t28". Im not talking about anyone who sells turbos, but a shop that does mapping, rebuilds, etc.
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Old 03-03-2001, 02:18 PM   #19
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Quote:
Mike, call up any "turbo manufacturer" and ask them what turbo-charger you should use for a 2.5l 4cyl. They will tell you "t28". Im not talking about anyone who sells turbos, but a shop that does mapping, rebuilds, etc.
I would be apalled at any company that would tell me that without even asking me my application, volumetric efficiency, modifcations, and many other questions that go into proper turbo selection.

Would be pretty stupid to sell a T28 to a drag racer aiming for the 10s.

The T3/T4 is simply a superior turbo. It sacrifices a little bit of spoolup time, but all performance turbos do.

A T28 will do good, but the T3/T4 will do better.
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Old 03-03-2001, 02:33 PM   #20
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Quote:
I recall someone racing a t3(2.5l) against a 1.8l 2wd Subie w/ an IHI and still beat him by .5 seconds!! HAHAHAHA!!
hehe...even I understand the power to weight ratio. Also, think about it, a 2.5L engine has to breathe in ALOT more air than a 1.8L engine so the IHI feeds the 1.8 very well. OK, how about you compare and that same IHI on a 2.5 against a T3 on a 2.5. Check the flow characteristics of both. See which is pushing more CFM's at the same boost level. Check intake temperature while you're at it too. Working around Joe and John I'm surprised you haven't heard that "it's not the amount of boost, but the CFM's being produced." I know I've heard it from them.

when it comes to choosing the right turbo you need to consider where you want your power and where you want the boost. if you want it lower in the power band get a smaller one; if you want it up high get a larger one.

*feeding the flame*
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Old 03-03-2001, 04:45 PM   #21
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So, Kevin, did you process my refund? You seem to have plenty of time to answer questions here.
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Old 03-03-2001, 05:13 PM   #22
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YES, it should be to you no later than Tuesday(banks take a couple of days to transfer electronically)

Kevin
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Old 03-03-2001, 05:17 PM   #23
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Thank you.
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Old 03-03-2001, 09:22 PM   #24
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Pimpsube, I think you need a Turbo101 class. I guarantee my left nut that a t3/04 with walk all over the t28. The t28 is only good for first gear where you use the whole rpm band. After that it is 4000rpms and up. That little turbo aint gonna do beans after that. That t3/04 will walk all over it any day. If you get a ball bearing t3/04 it will even walk all over the t28 even more, rediculiously more. Don't post **** that you dont know **** about. Drag racing=high rpm, so how can your t28 walk all over a t3/04 in 2nd, 3rd, and 4th gear. I don't think so. Peace. I am fighting in all good intention, so chill. Hit me with what ya got.

PS-and what's with you guys saying one turbo is designed for a certain car? One certain turbo does not win races. Peace out
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Old 03-04-2001, 12:00 AM   #25
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impRSa01,
Not that I disagree with what you are saying (T3/4 is well suited for our cars) but you don't want to turn this somewhat technical thread into name calling or insulting other member's intelligence. It would be nice if you toned down your last post. Kevin does work for JC Sports, and I would hear his facts on why the T-28 is too small for the RS, besides "turbo manufacturers" told him so.

I am a moderator, just not in this forum, so I am speaking as a member on this one. I will let one of the other moderators edit it if they want to keep this from turning ugly.

That T3/4 is way to big, that is why it could only muster a 13.2 a Kevin Thomas 2.2 liter OBS I bet with the T28 he would be in the 12's

Aaron http://www.azscooby.com


BTW: MikleYox It is nice to see you posting here again, I was getting my fill of you laying into people's claims on clubsi


[This message has been edited by AaronB (edited March 03, 2001).]
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