SimonsTeg

I was just wondering how different turbos perform at a set boost level. I've heard that the t-25s fall off but spool up quickly cus they're smaller, the 14b's hold boost better... so basically the bigger the turbo, the better it holds boost but also takes longer to spool.

Bigger turbos can put out higher boost levels but how do they compare at a set level. I mean, shouldn't you get the same gains from each turbo. Given a car has the same setup, boost is at 10 and should make about 250whp... it shouldn't matter what turbo is used cus boost is boost right?? 10lbs on a t-25 and on a t3/t4 should get *almost* the same results right?... other than the t-25 spooling faster then starting to drop off towards the end of the powerband. Only thing that makes the difference is being able to hold boost. A t-25 may hit 250whp max at 10lbs. before it starts to drop off while the t3/t4 may get up to 260-270whp because it holds the boost longer and the power that the cams create, add more power.

Someone let me know if this sounds right, and/or correct me on what i'm wrong about.

ninesecrx

First off boost is not boost and second picture this. You have a 3 inch pipe and a 3mm pipe. They both have a gauge on it and say 10 pounds. Do you want to try to plug the little 3mm line or the 3 inch. line? They both have 10 pounds right? But ones going to carry more mass inside because of the area it gets to fill up. Yes, the bigger one will take longer to fill up...which is why a bigger turbo will have more lag then a smaller turbo.....Mr Michael E. Laskey

SimonsTeg

I understand what you're talking about but my question is still unanswered. I already knew why it took longer for bigger turbos to spool. What I'd like to know is if you put the smallest turbo, that may max out at 15lbs of boost, on a car, set the boost to 10 and get it dynoed. Then you take a turbo that's about twice the size of the first, it has a max boost level of 30, swap the turbos so that there is aboslutely no differences except for the turbo itself, set the boost to 10lbs and get it dynoed, shouldn't the results be about the same??? Yea the smaller one will spool quicker, and yea the bigger turbo may end up making about 10whp more than the smaller cus it'll hold boost better, but that should be the only difference... the ability for the turbo to hold boost. It's not like setting the boost to 10 is pushing the turbos to their limit. The small one can get up to 15lbs and the big one can get up to 30lbs, but each turbo is only set to 10.

Look at it like this... what if every turbo held boost the same? The only difference between them is how fast they spool and how much boost they can put out. If you were looking to add boost to your car and keep the boost at 10lbs or a little less, which turbo would you choose??... the smallest one that spools the quickest, but can only put out no more than 15lbs of boost, or would you get the biggest monster turbo that takes an extra 2k RPM to spool, but can put out up to 40lbs of boost??? Keep in mind that once each turbo reaches full boost, they can hold it all the way through the powerband and not fall off, and that eventhough each turbo has different boost capacities, all you want is 10 so it doesn't matter if the turbo can put out up to 15lbs or up to 40lbs. Which turbo would you choose???

Now, can someone please answer my question? At a set boost level, do all turbos perform the same???... aside from how fast they spool and how they hold boost.

liam821

The spool times between the two arent THAT different. The 14b is a larger turbo.

The 14b flows around 405cfm and the t25 is around 305cfm. You can normally get about 60-70hp more outa the 14b then the t25.

And spool time isnt that different. Its going to be a little different on a honda depending on the motor, but on my eclipse i could spike 18psi of boost by 2500 rpms on a t25, a 14b would do the same thing but around 2900-3000rpms. So there is about a 500rpm difference.

liam

Etylorcen

You still dont get it. 10psi on a t4 turbo flow more air than 10psi on a 14b. Boost is not boost as you are stating.

rjardy

Two words

VOLUMETRIC EFFICIENCY

howthingswork.com may help you understand this more, 10psi on a t3 IS NOT comparable to 10psi on a t4.......

Rob

SimonsTeg

thanx guys, that's all i wanted. sorry if i made things seem kinda drawn out but i just didn't want anyone misunderstandingwhat i was asking. thanx again.

one more thing, is about 250whp at about 10lbs of boost using a t25, 14b, or t3 turbo, 450 injectors, in-tank pump, and dsm smic possible on a stock '91 b18a, with shotpeened rods and ARP rod bolts???

Ri5e

250 whp @ 10 psi with a with a b18a t25, t3 or 14b? You won't even be close, probably like 170-190 whp max.

01geeser

you gotta remember that ur compressing air. when you compress air you make it hot. so a t-25's 10psi would be considerably warmer than a t3/4's 10psi. because the t3/4 is more efficient at that boost level it will create less heat.