We are trying to solve an arguement so we need some good information that has scientific data or facts to back it up..yes i know it has been "covered" but no good conclusions come out of these topics as i hope will with this.

Basically Does a big turbo make more hp than a small turbo on the same engine at the same psi? If so HOW?

 

Yes, it does. Its my understanding that a large turbo can push more CFMs at the same PSI as a smaller turbo.

 

No, efficency plays a big part in this. The more your turbo sits in the compressor's most efficent area, the best power output will come.

Proof of this can easily be shown on Boosted Hybrid's latest GT28rs vs GT3071 thread where the GT28 blew the GT3071 out of the water at the exact same pressure. Compressor efficency means everything in picking a turbo. Cant always directly rely on the compressor map, but its a good place to start atleast.

 

so would the results have been different at a boost level more efficient for the gt30

 

thats why people upgrade to bigger turbos! more power...

 

the arguement is that 8psi is 8psi no matter how big the turbo is...

Is it possible to contain different amounts of air in 8psi?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">so would the results have been different at a boost level more efficient for the gt30</TD></TR></TABLE>

The two turbos have different characteristics for two different applications. Theoretically, boosting higher you will take the GT28rs out of its given efficency range and the GT3071 will then get in its efficency range. Two different turbos, two different characteristics.

Its hard to ever make a super generalization with turbos. The most important part of picking a turbo is one that will be efficent as much time as possible. That will offer the best powerband. Powerband is what people should be looking for instead of bullshit peak numbers. Powerband is what wins races.

 

Is it possible to contain different amounts of air in 8psi?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">Is it possible to contain different amounts of air in 8psi?
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You are getting too mucked up in this whole amount of air. It also comes down to quality of air. You want cool, dense air which will increase the volume which is the most important part.

At a given pressure ratio you need to figure what kind of air the turbo will pump out. Like i said, you cannot make a generalization about size of turbo. Size of turbo directly relates to the quality of air being pushed out.

Example: I have a T25 on some engine and a T3/t04e 60 trim on the exact same engine. I decide to boost 5psi which in this case allows the T25 to land in the compressors most efficent area of the map from 3000rpm to 6000rpm from 6000-7000(redline in this case) it drops in efficency. Meanwhile, the 60 trim turbo is far less efficent from 3000rpm to 5000rpm barely finding the compressor map and from 5000-7000rpm it finds the compressor map and is in the most efficent place possible at the end of the rpm scale.

You can guess that from 3000-5000, the t25 will kill the 60 trim in power. From 5000-7000 the T25 will begin to waver off and most likely cause your powerband to table top from 6000-7000 while the 60 trim will just start waking up and pull ahead at that point and offer significant gains. Now which is better? The answer would be solved by figuring out the area under the torque and horse power curves of both and seeing which area is largest.

Now you may say you want the 60 trim because when you shift you will fall back to around 5000rpm and you will be efficent. which is an accurate way to think about it, which brings me back to the whole powerband concept. Powerband is what wins races. the T25 turbo would most likely own that 60 trim turbo in your street racing application but in a straight line drag race would come up short because of the fact its not in optimal efficency when shifting.

To answer your question in the easiest way i can. If at 8spi some smaller turbo falls in the same efficency as some larger turbo at the same pressure, the larger turbo will produce more power.

 

here take a look at this thread https://honda-tech.com/zerothread?id=1045887

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">We are trying to solve an arguement so we need some good information that has scientific data or facts to back it up..yes i know it has been "covered" but no good conclusions come out of these topics as i hope will with this.

Basically Does a big turbo make more hp than a small turbo on the same engine at the same psi? If so HOW? </TD></TR></TABLE>

Yes, a larger turbo makes more power than a smaller turbo given the larger turbo isnt too ridiculously oversized. Theres is plenty of tech on this site about this. 8psi is NOT 8psi in terms of air flow. 8psi is only 8psi in terms of pressure, but pressure is only part of the equation. Also, dont get peak power confused with driveability. A car with a disgustingly over sized turbo isnt going to have any kid of respectable power band and very well could be making less power than a car with a properly sized turbo.


Modified by Mag00n at 12:33 AM 11/15/2004

 

yes it matters, think of it this way what would u get the most air out of, 8psi going through a straw or 8 psi goin through a 3 inch pipe. its still 8 psi but the amount of flow is different.

 

i agree but he says regardless it is still going through the same small hole in the end

 

Your friend is a moron.

 

ill try to get him to explain his point a little better

 

slap your friend

 

This has been covered a million times. The turbo gods said the power difference increase from a bigger turbo has to do largely from the larger turbine exhaust (less back pressure) and the compressed air isn't heated up as much as a small turbo (efficiency).

 

18 psi on a t25 &lt; 8 psi on a t88.

My point is there is going to be more air flowing at the same boost level with a larger turbo

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mag00n &raquo;</TD></TR><TR><TD CLASS="quote">

Yes, a larger turbo makes more power than a smaller turbo given the larger turbo isnt too ridiculously oversized. Theres is plenty of tech on this site about this. 8psi is NOT 8psi in terms of air flow. 8psi is only 8psi in terms of pressure, but pressure is only part of the equation. Also, dont get peak power confused with driveability. A car with a disgustingly over sized turbo isnt going to have any kid of respectable power band and very well could be making less power than a car with a properly sized turbo.


Modified by Mag00n at 12:33 AM 11/15/2004</TD></TR></TABLE>


OK I’m the one being slapped! My view on this subject is that a turbo is a compressor forcing air into the intake manifold, where boost is measured, the pressure that is in the manifold is released into the cylinder through the valves so no mater how much air is forced into the manifold that as long is it is 8 psi in the manifold the only amount of air that can be forced into the piston is what can be pushed through the valve opening from 8 psi of pressure. So how can there be a difference in HP if there is always 8 psi in the manifold. Any more increase in pressure from a greater CFM would generate a larger psi in the manifold. Please do not flame on me. Just explain in clear terms where I am wrong.

 

Here's what I gathered from my experience on this topic. I'm not saying I'm right but follow me.

Leaving out CFM and airflow and all that non-sense here's why bigger turbos make more power than smaller turbos.

I used the think that 8 psi in the intake manifold was 8 psi no matter what.
Well that would be true if your engine didn't have any sort of valve overlap. Valve overlap, in an all motor sense is a good thing. That is why you gain the most power on a K-series motor with a supercharger by advancing the intake cam 50 degrees. (I attended the Hondata seminar in Maryland) The reason this is so effective if because you are looking at this from the perspective that your engine is an air pump.

When you have no back pressure, you can run lots of overlap, and push lots of air through the engine. Since a Supercharger creates no backpressure, this is useful.

But what happens when there is back pressure? You can't run as much overlap. Which means that less air flows through the motor on each cycle. This in turn causes the air to get backed up in your intake manifold and cause high boost readings. Now say you get a bigger turbo with a bigger exhaust housing that flows more air. Less back pressure. You can run more overlap. More air flows through the motor instead of getting backed up into the intake manifold. In turn you make the same amount if not more power, only now your boost gauge is reading less boost.

 

so is 8psi...8psi no matter what? or not

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by deeweewoo &raquo;</TD></TR><TR><TD CLASS="quote">


OK I’m the one being slapped! My view on this subject is that a turbo is a compressor forcing air into the intake manifold, where boost is measured, the pressure that is in the manifold is released into the cylinder through the valves so no mater how much air is forced into the manifold that as long is it is 8 psi in the manifold the only amount of air that can be forced into the piston is what can be pushed through the valve opening from 8 psi of pressure. So how can there be a difference in HP if there is always 8 psi in the manifold. Any more increase in pressure from a greater CFM would generate a larger psi in the manifold. Please do not flame on me. Just explain in clear terms where I am wrong.

</TD></TR></TABLE>

Where does the compressor's given efficency come into play? A turbo will not produce as much air as it is rated for if its not spinning at the most favorable rate.

At X psi a smaller turbo can produce more air than a bigger turbo at the same X pressure. If you dont believe this, there is a link on this very thread that will prove my point very easily.

Efficency


Type GSR, uh....there is a dyno on this very thread that has a smaller turbo killing a bigger turbo in every single place at certain points adding 50whp, how can you maintain this opinion and ignore the nature of the turbo's actual quality of air? Why do turbo manufacturers even bother printing compressor maps if its your valves? We all know cams and valve train can aid in gains, but given what you have and keeping all variables as close to the same as possible, it absoltuely comes down to efficency.

 

OK now relate that to the amount of air in the piston because this whole argument was about breaking stock internals. Will there be more air in the piston at 8 psi from a large turbo than there is at 8 psi from a small turbo?

 

campthen

that is sorta misleading the way you said it but i get it....but considering both turbos were efficient in that area..would x psi = x psi in HP

 

Well obviously there's a cutoff limit to how big you can make your turbo before it makes less power than a smaller one. If you pull a watermelon sized turbo off a Peterbilt and put in on a stock DX motor vs. a T3/T04E then yes, the smaller turbo will win, because of the efficiency. But let's say T3/T04E vs. SC61 on a 2.0 L GS-R motor. I'm pretty sure you'd be able to make more power with the SC61.

I haven't seen the graph you speak of, but did they change cam position? were both tuned to capacity? It seems to me like the bigger turbo may have just been too big. There I said it, there is such thing as a turbo that is too big.

No 8 psi isn't 8 psi no matter what.