# T3 Or T3/t04e, Which Pushes More Cfm's @ 20 Psi

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#### mwasnp

##### Senior Member
I am arguing with a friend. I know the t3 has more lag, so I assume its a larger turbo in that it would push more cfm's at any given psi, and has a higher range, ie you can safely run more psi with it than a t3/t04e. Well, given the motor is built properly and tuned well. What is the deal, does anyone have the specs for each of these turbos? I know the trim matters, I'd love to compare 2 with equal trim if possible. Thanks guys

if i remember correctly....the t3 is the smaller of the 2...and i think the t3t4 would give me cfm...thats just me though but i think thats right...someone correct me if im wrong

Assuming the t3 and the t3/t04e are of the same specs, only difference is one being a t04e compressor- the t3 turbine will make power faster, and the t3/t04 will lag more cause of the larger compressor.

A while ago, i said that if everything is constant- then at a set psi level on any turbo then the cfm's will be the same- and here is what calesta told me:

given all factors constant- engine @ constant RPM, intake manifold pressure the same... yes the flow rate (CFM) will be the same.

The main deal with relating flowrate vs pressure is in how MUCH flow the turbo can maintain at certain pressures. Your small turbo will start to "run out of steam" at higher revs, while the larger turbo will still be able to maintain pressure.

Let's say that you have two turbos... one is capable of 600cfm @ 15psi, and one is capable of 300cfm @ 15psi. Now let's take a theoretical engine that chugs 50cfm of air (naturally aspirated) per 1000rpm.

At 2000rpm, the engine only uses 100cfm at atmospheric pressure. The small turbo can maintain 300cfm at 15psi, and the larger turbo can maintain 600cfm at 15psi... both only need to supply 200cfm total (engine wants 100cfm at atmospheric, then add another 100cfm to boost 1 bar/atm) to maintain a +1 bar positive manifold pressure (or 14.7psi), so both will produce the same amount of power at that engine speed and boost level.

At 3000rpm, the engine wants 150cfm at atmospheric, so you need 300cfm to maintain 15psi of boost. No problem for either turbo here either- they can both maintain 300cfm at 15psi.

Once you step the engine up to 4000rpm, it wants 200cfm. To maintain 15psi of boost, you'll have to flow 400cfm into the intake manifold- and here is where the small turbo starts to choke. It's now operating outside its efficiency range, and it can't supply 400cfm of air to the engine. It can try- but it'll be spinning so fast that it does more work heating the air charge than compressing it. You start running into supersonic blade tip speeds, cavitation, etc- then a turbo that starts caramelizing its oil supply and starts to die. The larger turbo has no problem- it's still well within its efficiency range. It can flow 400cfm with no problems.

Since it can go to 600cfm at 15psi, it can maintain boost on that engine all the way to 6000rpm. It's supplying the 300cfm to satisfy the engine's atmospheric pressure needs, then another 300cfm to increase intake manifold pressure to 15psi (well 14.7 really).

Understand how it works? I could draw you some diagrams, but I don't really feel like it right now... the downside to using the bigger turbo is that it takes longer to 'spool up' and start producing positive intake manifold pressure against your engine. Your power curve will start later, but you'll be able to flow more air at those higher revs, and ultimately make more power. Go with a smaller turbo and you'll have your power sooner, but you could be choking your engine off towards redline.

This is my somewhat shorter version of that

CFM's is what makes HP not PSI. All the PSI does is move the air. You need the move the air efficiently though. You want to run the turbo at about 70%-80% of its potential. The intake system will only handle so much flow. Say the flow is maxed out at 12 psi and you are running 15-16 psi. That will create a lot of heat. The boost pressure may indicate 15 or 16 psi but there are no more air molecules in the intake charge than a cooler 12 psi intake charge. After a certain point, increased boost gives decreased intake charge density plus more heat and detonation plus increased ignition retard. Increasing the boost begins to give rapidly diminishing returns until a point of negative return is reached.

So if you increase the flow of your intake and you were already running the turbo at 70%-80% of it's potential at 15 psi before, you may be running it at 90% at 15 psi now. That's going to create heat and inefficient flow. You need a bigger turbo to get back down to that 70%-80% range.

Basically, these are the reasons to use a larger turbo.

1. More lag (benefitial sometimes)

2. Cooler intake charge, not overspinning the turbo at high rpm, larger turbos generally can support more psi than the smaller ones.

the larger turbo will make more power due to the lower intake temps, and it wont fall out of the compressor effeciency range when the revs increase.

Originally posted by mwvnos@Jan 11 2003, 05:10 PM
if i remember correctly....the t3 is the smaller of the 2...and i think the t3t4 would give me cfm...thats just me though but i think thats right...someone correct me if im wrong

There are 2 main parts to a turbocharger- the compressor( side that pumps air into the intake) and the turbine (side that connects to the turbo manifold and spools up the turbine.

So when you say t3/t4, you use the t3 turbine and the typically larger t4 compressor

There are many different sizes and trims to a turbo, so you cant just say a t04e is bigger than a t3. It all depends on the specific sizes of it. But generally, a straight t3 turbo is damn small, t4 is good sized, then there are the hybrids like t4/60-1, a monster of a turbo...

the t3/t04e will make more cfm's than a straight t3

Thanks guys, my confusion was in seeing a t3/60-1, and not really knowing what that meant, and I didnt explain that. I know that the t3/60-1 is huge, b explained it all to me. Thanks though alot of good info in this thread...

So which turbo do you (solreaver and Brian) recommend? I'm just wondering because I think I remember B calling the t3-t04e a fad, faulty memory though so somebody clear this up.

Originally posted by preluderjs@Jan 13 2003, 09:11 PM
So which turbo do you (solreaver and B ) recommend? I'm just wondering because I think I remember be calling the t3-t04e a fad, faulty memory though so somebody clear this up.

a good sized t3/t04e will support plent of power, and may even lag less than a similarly sized t3/60-1. The t3/60-1 will have more top end- and the t3/04 should have quicker response. Im gonna try to get ahold of a t3/60-1 for my setup, if i cant find that then a 60/.63 t3/t04e will do just fine for me

Im pretty sure that B will recommend the t3/60-1

Thanks for the info, seems like the t3-t04e is the perfect set-up for a street car due to the response, just w/ a bigger trim. I think the response is pretty important, especially in a heavy car like a prelude. This is probably isn't the right place to ask, but how hard do would it be to pass emmisions w/ this set-up (97-01 H22 w/ t3-t04e, skunk 2 turbo camshafts and full valvetrain, hondata, aem cam gears (or anything better that I dont know of, and the regular bolt-ons)? I'm just naming what I think would affect emissions.

Originally posted by preluderjs@Jan 13 2003, 09:44 PM
Thanks for the info, seems like the t3-t04e is the perfect set-up for a street car due to the response, just w/ a bigger trim. I think the response is pretty important, especially in a heavy car like a prelude. This is probably isn't the right place to ask, but how hard do would it be to pass emmisions w/ this set-up (97-01 H22 w/ t3-t04e, skunk 2 turbo camshafts and full valvetrain, hondata, aem cam gears (or anything better that I dont know of, and the regular bolt-ons)? I'm just naming what I think would affect emissions.

well, if youre running an external wastegate that dumps it back into the exhaust before the cat, you will have a better chance of passing...but i really have no idea if you will pass or not.

Where are you located? I live in iowa and dont really care if stuff is emissions legal cause we never get tested here

My bad, I thought about it but still forgot to mention I'm in hell hole cali. <_<

im gonna start a club for people in cali (like me) who gotta deal with this shit. emissions and passing..lol. u got hondata.. what stage?? cuz (if you can) run your car lean and dont let vtec engage. that will help. And if you go to the smog shop with the turbo on make sure everything has a CARB EO (California Air Resource Board Executive Order) number on it. AND the only ones ive seen are Greddy. BUT i havent really shopped around for turbos, so i could be wrong. The other option is to take the turbo off before you go smog it.. if you got any other questions.. just ask away

If you are looking for a good deal on a t3/60-1 www.sr20performance.com has them for \$648 which I think is dam cheap. Thats with free shipping too!!! And you can pick in 3 trims for the exhaust side, .48, .63 and .82, compressor side is only available in .70.

there's an easy soloution to cali laws.

MOVE

OK the reason why Greddy kits are 50 state legal is because they use internal wastegated turbo's. Any external waste gate that uses its own downpipe to return the exhaust before the cat will be legal in some other states. NOT CALI THOUGH! And external wastegates that just dump exhaust under the hood(not passing through the cat) might be legit in like maybe 6 states if your lucky. Also as more and more states are hopping on the "SMOG WAGON". They won't end up legal for long. Just my Knowledge and .02

How do the Greddy kits compare to the turbos mentioned before? I know it seems kind of stupid but anyone think a car could pass if it had a greddy CARB EO with it but actually a different turbo under the hood?

the numbers won't match... so it depends again on how strict the station you go to is.

the actual turbo itself really shouldn't matter. but the ls kit comes with an 18g. the 20g is the biggest turbo you are going to fit on the greddy manifold anyway.
its a small kit, but good for 250 horse

Good for 250 EXTRA HP

Originally posted by knowledge@Jan 14 2003, 05:57 AM
Good for 250 EXTRA HP

So your saying 250 hp extra on an H22 which would make a little over 400 with a street legal greddy kit? Sounds too good to be true but I hope it is. Around what p.s.i. are we talking about here to reach these numbers? Its not really important but I'm just wondering.

Ok on Greddy's SOHC kit with the 15g turbo. The 15g on a D16Z6 produces about 10hp per 1psi. It's a known fact. I would never push a 15g past 15psi. They tend to grenade after that. So you figure at 15psi on the SOHC it's an added 150hp. 125+150=275! Thats with just the kit. Now mind you the stock motor won't handle that. The 18g that comes in the H-series kit flows alot more CFM's. So you can see from my example that a well built setup with a Greddy kit installed can be a big player on the street. Plus Greddy kits are 50 state legal.