14b vs. evoIII at same boost level

[racetracker]

quick question i was curious as to why people that change there 14b to a evoIII or bigger say that there car pulls so much harder at the same psi im just confused maybe this is dumb but why would one turbo make more power at the same boost level if they are both running say 14 psi why would one be more efficent

srry for spelling thanks guys help me understand

 

[oldman]

14 psi in the intake tract is 14psi, the only factor which accounts for differences in air flow between two different turbos at the same psi is the intake temperature which is determined by the efficiency of the turbos with everything else being equal. The difference between a 14b and EVO3 at 14psi is probably minimal, except for spool up and upper RPMs, because 14psi is well within the efficiency range of both turbos. now 20+psi is a different story.

 

[tranman91]

Airflow of Evo III 16g@ 14psi > Airflow of 14b@ 14psi

Think of it this way...You have two fans, one x-small, and one x-large. Each fan has the ability to rotate one time. Even though each fan rotates equally, one time...Which fan do you think will create more air in that one rotation?


Efficiency of turbos is like this...

Again two fans, one small, one large. Both fans are able to cool down a really hot girl after a workout. The small fan can do the job...but one girl is all it can handle. The big fan can do the job...but while cooling down that one girl...it also encourages another three girls to join in.

As you can imagine, the small fan is only efficient at cooling one girl. And that's fine if that's all you want, but it's not going to do a very good job trying to cool down two girls because it wasn't designed to.

Now for the large fan. It can cool down one girl, but you're not using it to it's potential. And therefore it would be more efficient cooling down four girls as it was designed to do.


I'm not a huge technical person so I can't put it into those words, so I hope my analogy helps as this is how I understand it.

 

[BaddAssGst]

Airflow of Evo III 16g@ 14psi > Airflow of 14b@ 14psi

Think of it this way...You have two fans, one x-small, and one x-large. Each fan has the ability to rotate one time. Even though each fan rotates equally, one time...Which fan do you think will create more air in that one rotation?


Efficiency of turbos is like this...

Again two fans, one small, one large. Both fans are able to cool down a really hot girl after a workout. The small fan can do the job...but one girl is all it can handle. The big fan can do the job...but while cooling down that one girl...it also encourages another three girls to join in.

As you can imagine, the small fan is only efficient at cooling one girl. And that's fine if that's all you want, but it's not going to do a very good job trying to cool down two girls because it wasn't designed to.

Now for the large fan. It can cool down one girl, but you're not using it to it's potential. And therefore it would be more efficient cooling down four girls as it was designed to do.


I'm not a huge technical person so I can't put it into those words, so I hope my analogy helps as this is how I understand it.

Best post ever. I've never seen such an excellent way to describe something. In a very effective and appropriate way, points are given.

 

[racetracker]

Airflow of Evo III 16g@ 14psi > Airflow of 14b@ 14psi

Think of it this way...You have two fans, one x-small, and one x-large. Each fan has the ability to rotate one time. Even though each fan rotates equally, one time...Which fan do you think will create more air in that one rotation?


Efficiency of turbos is like this...

Again two fans, one small, one large. Both fans are able to cool down a really hot girl after a workout. The small fan can do the job...but one girl is all it can handle. The big fan can do the job...but while cooling down that one girl...it also encourages another three girls to join in.

As you can imagine, the small fan is only efficient at cooling one girl. And that's fine if that's all you want, but it's not going to do a very good job trying to cool down two girls because it wasn't designed to.

Now for the large fan. It can cool down one girl, but you're not using it to it's potential. And therefore it would be more efficient cooling down four girls as it was designed to do.


I'm not a huge technical person so I can't put it into those words, so I hope my analogy helps as this is how I understand it.

thats got to be the best explaination ive ever gotten really appreciate you helping out and putting it in words i can understand

 

[tranman91]

No prob

 

[firebirdvert305]

the awesome's post i have ever read....i nominate this for post of the year

 

[wret]

Interesting analogy, and you certainly got everyone's attention, but you didn't answer the question.

Oldman got it right. 14psi produced by one turbo is the same as 14psi from another.

tranman91, change your analogy to air conditioning and you may hit closer to the mark.

 

[tranman91]

I agree that 14psi is the same as 14psi...but this is a pressure rating that doesn't scale the volume of air(CFM) that a turbo produces. So in turn, we cannot say that two different sized turbos, at the same pressure rating...will give the same result. Different turbos rate a variance of CFM at the same PSI. So we can't use 'PSI' to place different sized turbos on common ground.

I found this... http://ztechz.net/id6.html which compares various turbos at 15psi.

An example from the link:

A 16g flows 475cfm @ 2PR(14.7psi) @ 68% efficiency

A 20g flows 640cfm @ 2PR(14.7psi) @ 68% efficiency

So, that's more air volume at the same pressure rating...small fan, big fan...right?

This is how the analogy came about to answer the original posters question. Do I have it all wrong?

 

[wret]

One turbo cannot flow more than the other if the motor is not consuming more. If either turbo pushes more than the motor is allowing in, it results in a pressure increase and the boost controller reacts, keeping the boost at 14psi. The motor would be consuming the same volume of air in either case so there would be no performance differences unless, as oldman stated, there are intake air temperature differences.

The question is similar to this one: A Geo Metro and a Ferrari Enzo are both traveling 80 mph. Which one will travel 100 mile the fastest?

 

[idt512]

One turbo cannot flow more than the other if the motor is not consuming more. If either turbo pushes more than the motor is allowing in, it results in a pressure increase and the boost controller reacts, keeping the boost at 14psi. The motor would be consuming the same volume of air in either case so there would be no performance differences unless, as oldman stated, there are intake air temperature differences.

Thats what its all about though, the bigger turbo will generate the same 14psi much cooler and more dense than a smaller turbo and therefore more HP can be produced. What is being compared here is why one turbo produces more hp than another at the same pressure... its all in the temperature that its arriving at.

 

[titogs95]

One turbo cannot flow more than the other if the motor is not consuming more. If either turbo pushes more than the motor is allowing in, it results in a pressure increase and the boost controller reacts, keeping the boost at 14psi. The motor would be consuming the same volume of air in either case so there would be no performance differences unless, as oldman stated, there are intake air temperature differences.

The question is similar to this one: A Geo Metro and a Ferrari Enzo are both traveling 80 mph. Which one will travel 100 mile the fastest?

So it is more like: the bigger turbo can flow farther (more psi) than the other one, and still be in his 70% of potential?

In other word: A motor that revs more and keep its hp/torque band increasing across the rpm constantly?

Correct me if I am wrong....

 

[racetracker]

so the only diffrence that would make more power is the evo would have a cooler charge?

other than that there would be no diffrence in power until you get to into the higher boost levels which would be out of the 14bs efficency range right?

i was just confused because i have read other peoples post saying that their car pulled harder at the same psi

 

[Talesin]

Yes, and a cooler charge = more oxygen into the cylinder at the same psi. So it WILL pull harder. It's at the same pressurization level, but there's literally more air to combust, when it's colder.

Like the difference between crappy milk chocolate, and extra dark bittersweet. They both occupy the same volume, but the milk chocolate is less substantial.. it has less mass.

 

[idt512]

other than that there would be no diffrence in power until you get to into the higher boost levels which would be out of the 14bs efficency range right?

i was just confused because i have read other peoples post saying that their car pulled harder at the same psi

the evo WILL pull harder at any SAME psi as the 14b because it will always deliver the air at a cooler charge than the 14b.... as long as you are comparing equal psi. Density is the key factor here, there is more air per given volume in cooler air, just because they are both at 14psi, the cooler air has more air than when warm.

Think of an elevator, 10 skinny people will fit, but only 5 fat people can fit, now think of the skinny people as the cooler air, and the fatter people as the hotter air, warmer air expands taking up more room, therefore less people (hot air) can fit

 

[tranman91]

tranman91, change your analogy to air conditioning and you may hit closer to the mark.

You're right. If the analogy was changed to air conditioning, it would be more accurate.

I think a point I was trying to make is that you can't determine the characteristics of air volume by the pressure rating. Because you can have 15psi of hot air or otherwise 15psi of cold air.

 

[DSM90AWD]

I was interested about this myself so did a little digging and put my findings together HERE

Note that there is a significant efficiency difference BTW the 14B and 16G even at 15psi (17psi @ compressor). That 3% efficiency difference creats ~12F more heat at the same boost level (246F 14B vs 234F "small" 16G)

 

[kevingst]

It think I'm still a little thrown off because I was under the impression that the cfm's did account for something. For instance: with my 14b @ 20 psi I was flowing 32-33lb/min and with the Bullseye t04b I'm flowing 39lbs/min @ 20psi. I thought it was actually compressing more air at the same pressure, therefore making it "pull harder". However, I do understand the "colder=denser" side of the discussion.

 

[polonez]

i was gonna buy an evoIII but now im confused. Im only planning to run 15lbs. soo??? there wont be any diff if I run a 14b? with lets say a supra sidemount?

 

[DSM90AWD]

I admit my example was in simplistic terms. But to add, if you compress air into a closed system (your intake tract) at a static pressure, you will fit more air volume the cooler/denser it is.

Another thing to note is that Intercooler efficiency is just as important as compressor efficiency. Taking my example above and pitting the 16G with the factory SMIC (assume 70% efficient) against a 14B with an 80% efficient FMIC. The 14B would actually produce a 17F cooler charge air temp (104F vs 121F)

 

[tranman91]

I was interested about this myself so did a little digging and put my findings together HERE

Note that there is a significant efficiency difference BTW the 14B and 16G even at 15psi (17psi @ compressor). That 3% efficiency difference creats ~12F more heat at the same boost level (246F 14B vs 234F "small" 16G)

With these statitics in particular, is it feasible to conclude that a 16g will pull harder than a 14b at the same pressure level?

At the same pressure level, there are differences in temperature. Therefore, the turbo that flows cooler with more oxygenated air, will allow for more combustion.

Right? So, regardless of how much air is actually flowing...

Air temperature of 16g @ 15psi < Air temperature of 14b @ 15psi

Making the 16g pull harder at the same given PSI.

 

[daren_p]

i was gonna buy an evoIII but now im confused. Im only planning to run 15lbs. soo??? there wont be any diff if I run a 14b? with lets say a supra sidemount?

Even if your only going to run 15 psi go with the evoIII. It should be able to do this more efficently then the 14b, giving you more hp. I believe with the newer design (thinner comp wheel) of the evoIII, even though overall its larger then the 14b it will spool faster. Another benefit is the evoIII won't drop off in the upper rpms.

 

[idt512]

I was under the impression that the cfm's did account for something. For instance: with my 14b @ 20 psi I was flowing 32-33lb/min and with the Bullseye t04b I'm flowing 39lbs/min @ 20psi. I thought it was actually compressing more air at the same pressure

Correct! it is compressing more air, the higher CFMs is the result of the cooler air coming from your t04b at the same psi... perfect example right there with flow ratings to back it up

 

[DSM90AWD]

Another benefit is the evoIII won't drop off in the upper rpms.

Correct. The higher the RPMs you take your car the harder your turbo has to work to keep the same boost pressure. A 14B turbo set to say 16psi would have no problem supplying airflow from 3K-6K RPMs, but take it up to 8K add cams (increases engine VE), and you'd be wayyy on the right side of the graph where efficiency drops off like Bush's approval rating

 

[oldman]

Correct. The higher the RPMs you take your car the harder your turbo has to work to keep the same boost pressure. A 14B turbo set to say 16psi would have no problem supplying airflow from 3K-6K RPMs, but take it up to 8K add cams (increases engine VE), and you'd be wayyy on the right side of the graph where efficiency drops off

Isn't that pretty much what I said in post #2?

like Bush's approval rating

I should ban your ass for trying to start shit.