boosted94cx

kind of a brain fart/stupid question...but, i'm asking

say you have a stock sleeved ls/vtec...rod/pistons..blah blah

say you ran a 60-1 s-cover .63a/r, and took that to the safe limits of pump gas....
then, say you ran an SC61 s-cover .63a/r...and took that to the safe limit of pump
could you make more power with the SC61 than the 60-1? i'm not saying the ragged edge of pump gas...not like 500whp area...but, would the SC61, being a bigger turbo, allow for more power to be made safer/just as safe?

Jay_Sensing

While I am no genious on this subject, I will throw in my .02.

Say you have a greddy 15g kit, at 10lbs you can make we will say 275 hp on a dynopack with a 3 inch DP and an OBD1 conversion and crome tune.

Now take the same LSVTEC and run a T04Z at 10lbs, same tuner, same dyno and same car and watch it make 365 within a week of the same time.

To me, the reason behind this is one the flow rate and efficiency of the turbo and the fact it isn't even working to make that 10 lbs of boost so the air charge is nice and cool which equals a denser charge and the ability to burn more fuel thus more power.

That being said, I would think you could raise your pump gas limits with a larger turbo because of it's ability to have a cooler charge therefore warding off detonation longer.

Again, I am not an expert so this could be a jacked up thought.

wade

iTrader: (1)

i am no guru,but i think yes with a GOOD IC to keep the intake air temps down. hotter AITs can make the chances of detonation and knocking/pinging easier to occur.

bigger turbo will be further from its limit thus not over spinning its self creating hotter air as a result from being closer to its threshold

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jay_Sensing &raquo;</TD></TR><TR><TD CLASS="quote">To me, the reason behind this is one the flow rate and efficiency of the turbo and the fact it isn't even working to make that 10 lbs of boost so the air charge is nice and cool which equals a denser charge and the ability to burn more fuel thus more power.

That being said, I would think you could raise your pump gas limits with a larger turbo because of it's ability to have a cooler charge therefore warding off detonation longer.
</TD></TR></TABLE>

Air temperature is simply air temperature. A T25 pushing at 10 PSI @ 80 deg F has the same cold dense air as a larger T04Z also pushing 10 PSI @ 80 deg F. Larger turbos are efficient through both the turbine/compressor and their ability to free up the exhaust side of the engine. The larger the turbine, the more exhaust gases can escape, therefore, allow more fresh air into the engine. Now the same 10 psi against the intake valves between the smaller and larger turbo is no longer the same because of different amount of CFM inside the cylinders. That's how a larger turbo can make more power @ the same PSI, and most of the time, making the engine slightly safer because there is less backpressure against the engine.

Jay_Sensing

It may be 80 degrees OAT but what about IAT? That is what I am getting at, a T25 is going to raise IAT's because it is having to work harder to get that 10lbs of boost/restriction in the intake tract that the To4Z will right?


Not arguing, asking because I like to know these things. I am a Helicopter mechanic by trade and at the moment, an instructor covering turboshaft engines and rotors so I know more than my share about mechanical engineering and the like, just not sure about this portion so I like explanations lol.
Thanks.

wade

iTrader: (1)

jay we are on the same page here, so its cool.

must be a ebp thing

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jay_Sensing &raquo;</TD></TR><TR><TD CLASS="quote">It may be 80 degrees OAT but what about IAT? That is what I am getting at, a T25 is going to raise IAT's because it is having to work harder to get that 10lbs of boost/restriction in the intake tract that the To4Z will right?

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

Well, I am talking air entering the engine, so it's going to be IAT regardless. If the intercooler is doing a proper job, it is going to be able to cool off IAT's close to ambient. Especially when we are talking about 10 PSI on a T25 which is still well within the efficiency range of the turbo, but the facts tell us that the larger T04Z still makes way more power than the T25 at 10 PSI.

T25 @ 10 PSI with 80 deg IAT will have the same air density as T04Z @ 10 PSI with 80 deg IAT. The air pressurizing at the intake manifold/intake valves is the same density air, but it is only the fact that the engine is only engulfing XXX amount of CFM of air which dictates power output. That's the main difference between small and large turbos. The large turbine on a large turbo can dramatically free up the exhaust side and achieve a much higher VE, so the same 10 PSI against the intake manifold can now allow a lot more CFM into the engine. That's how it makes more power

Jay_Sensing

It does make sense to me the way you are explaining it man, completely. But at the same time, I have to disagree with the fact that the intercooler can cool a charge to ambient temp. It can infact cool it significantly but I don't think it has the ability to cool it that well.

As far as efficiency range, the efficiency range is more than just pressure, it's pressure in relation it volumetric efficiency on a given displacement at a given RPM which will equal the total amount of air the specific engine is able to ingest at a certain RPM. As we both know, boost is simply a measure of restriction in an intake tract.

That being said, I agree tottaly on the exhaust side of the matter but I have to agree to disagree slightly on the intake temps becuase on a high revving very efficient motor, I can see a decent gain being made just from the ability of the larger turbo to keep the air cooler therefore more dense and allowing more fuel to be burned.

Thanks for a civil discussion though, that **** don't happen here often lol.

SOHC_MShue

Certain compressors are efficient at different airflow levels. The t25 might be just as efficient as a t3/t4 at say 10psi on a d16, but at 18psi the t25 will become a hairdryer where the t3/t4 will have much cooler iat's.

wade

iTrader: (1)

exactly, thank you, i just suck at putting words from my brain into the computer!

fled

And now in lay terms...

What I got: Larger exhaust/turbine housing passes out air easier to the DP, and by the same measure, air enters into the compressor easier than a smaller turbine equipped turbo?

BUT...Why does a GT35R w/ .63 AR turbine make more than a GT3076R w/ the same .63 AR turbine at the same PSI?

SOHC_MShue

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fled &raquo;</TD></TR><TR><TD CLASS="quote">And now in lay terms...

What I got: Larger exhaust/turbine housing passes out air easier to the DP, and by the same measure, air enters into the compressor easier than a smaller turbine equipped turbo?

BUT...Why does a GT35R w/ .63 AR turbine make more than a GT3076R w/ the same .63 AR turbine at the same PSI?</TD></TR></TABLE>
different compressor

Muckman

iTrader: (2)

Tony that is by far the best explination Ive ever read on this matter. Tony the smart ****

mrbigg9032

This is by far one of the most informative posts I've read on here in a while. Thanks guys for the lesson.. Keep it comeing, I like to learn!!!!

tony1

NO NO NO NO NO!!! lol, Forget about CFM. If there is 10psi in the manifold on said engine, then it's 10psi, period. The only way you can change the amount of air that will enter the engine is to change the density. The only way to do that is to change the temperature. If the charge temperature is 80 deg., then it's doesn't matter how big the turbo is, the same amount of air is going in the motor. The engine is the restriction, and the restriction is what makes "boost". A smaller turbo will eventually not be able to keep up with the airflow requirements, and boost will drop. The amount of air the turbo can flow is irrelevant if boost is constant. If it's is flowing enough to maintain the same boost as a big turbo, then temperature is the only variable that can change the MASS of air entering the engine. Volume is fixed. So, on the compressor side you have temperature, which is efficiency (which is why we have compressor maps), and on the exhaust side you have exhaust backpressure. 95% of the time, the larger turbo is going to have a larger exhaust wheel/housing and that's where most of the power comes from. And to answer the original question, yes, a bigger turbo greatly raises the knock limit on a motor, because of both lower intake temps and less exhaust backpressure. The whole CFM/volume thing is a VERY common misunderstanding.

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fled &raquo;</TD></TR><TR><TD CLASS="quote">And now in lay terms...

What I got: Larger exhaust/turbine housing passes out air easier to the DP, and by the same measure, air enters into the compressor easier than a smaller turbine equipped turbo?

BUT...Why does a GT35R w/ .63 AR turbine make more than a GT3076R w/ the same .63 AR turbine at the same PSI?</TD></TR></TABLE>

There is a lot more to the turbine than just the housing A/R... In fact, the turbine wheel is just as critical as the turbine housing A/R. The turbine housing is the diameter and size of the exhaust path, but the turbine wheel is the "exit way" which allows a certain volume of exhaust to pass through vs turbine RPM.

To answer your question, the GT35R has a larger and more aggressive turbine wheel than the GT3076R. Compressor size has minimal affect on power unless the turbo is running out of CFM at a relatively low PSI. Most of the time our Honda engines with nice tubular manifolds are able to completely dry out a small turbo, ie: a T25 even at a low 10 psi because the engine is already engulfing more than 28 lbs/min of airflow in which the turbo is rated for. When the CFM falls behind the engine's demand, pressure drops and that's the usual "blowing hot air". This info can be easily obtained by looking at the compressor maps.

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jay_Sensing &raquo;</TD></TR><TR><TD CLASS="quote">It does make sense to me the way you are explaining it man, completely. But at the same time, I have to disagree with the fact that the intercooler can cool a charge to ambient temp. It can infact cool it significantly but I don't think it has the ability to cool it that well.

As far as efficiency range, the efficiency range is more than just pressure, it's pressure in relation it volumetric efficiency on a given displacement at a given RPM which will equal the total amount of air the specific engine is able to ingest at a certain RPM. As we both know, boost is simply a measure of restriction in an intake tract.

That being said, I agree tottaly on the exhaust side of the matter but I have to agree to disagree slightly on the intake temps becuase on a high revving very efficient motor, I can see a decent gain being made just from the ability of the larger turbo to keep the air cooler therefore more dense and allowing more fuel to be burned.

Thanks for a civil discussion though, that **** don't happen here often lol.</TD></TR></TABLE>

I've stated that a good intercooler could lower IAT's close to ambient temps. This is pretty normal, as I've seen numerous datalogs showing IAT's being only 10-15 deg F warmer than ambient temps. Sometimes it can get closer to ambient if the airflow across the intercooler is good and the engine bay hasn't been heatsoaked. But it's easy to get some numbers out... It wouldn't be realistic to think that a larger compressor could create IAT's enough to compensate up to 20% gain of power that we usually see, right? It's not like a T04Z would be blowing 80 deg F of air while a T25 is blowing 250 deg F. Differences are minimal, especially when both turbochargers are running within their efficiency range

sharkcohen

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">NO NO NO NO NO!!! lol, Forget about CFM. If there is 10psi in the manifold on said engine, then it's 10psi, period. The only way you can change the amount of air that will enter the engine is to change the density. The only way to do that is to change the temperature. If the charge temperature is 80 deg., then it's doesn't matter how big the turbo is, the same amount of air is going in the motor. The engine is the restriction, and the restriction is what makes "boost". A smaller turbo will eventually not be able to keep up with the airflow requirements, and boost will drop. The amount of air the turbo can flow is irrelevant if boost is constant. If it's is flowing enough to maintain the same boost as a big turbo, then temperature is the only variable that can change the MASS of air entering the engine. Volume is fixed. So, on the compressor side you have temperature, which is efficiency (which is why we have compressor maps), and on the exhaust side you have exhaust backpressure. 95% of the time, the larger turbo is going to have a larger exhaust wheel/housing and that's where most of the power comes from. And to answer the original question, yes, a bigger turbo greatly raises the knock limit on a motor, because of both lower intake temps and less exhaust backpressure. The whole CFM/volume thing is a VERY common misunderstanding.</TD></TR></TABLE>
Thank goodness, some sanity in this thread.

CoreyR

let me try to understand this better, because im a bit confused. areyou saying basically boost pressure is boost pressure no matter the size of the turbo and the reason a larger turbo makes more power is becuase it doesnt have to work as hard as the smaller turbo to pressurize the air to say 15 psi thus doesnt heat the air up as much resulting in denser air? i can see how that makes sense but at the same time is it really possible that if you have a t25 and a 35R at the same boost pressure and the same IAT entering the engine that the 35R wont make more power?

i was always under the impression that alarger turbo makes more power becuase it flows more air at the same pressure.

thomas@LPS

Quote, originally posted by tony1 »
NO NO NO NO NO!!! lol, Forget about CFM. If there is 10psi in the manifold on said engine, then it's 10psi, period. The only way you can change the amount of air that will enter the engine is to change the density. The only way to do that is to change the temperature. If the charge temperature is 80 deg., then it's doesn't matter how big the turbo is, the same amount of air is going in the motor. The engine is the restriction, and the restriction is what makes "boost". A smaller turbo will eventually not be able to keep up with the airflow requirements, and boost will drop. The amount of air the turbo can flow is irrelevant if boost is constant. If it's is flowing enough to maintain the same boost as a big turbo, then temperature is the only variable that can change the MASS of air entering the engine. Volume is fixed. So, on the compressor side you have temperature, which is efficiency (which is why we have compressor maps), and on the exhaust side you have exhaust backpressure. 95% of the time, the larger turbo is going to have a larger exhaust wheel/housing and that's where most of the power comes from. And to answer the original question, yes, a bigger turbo greatly raises the knock limit on a motor, because of both lower intake temps and less exhaust backpressure. The whole CFM/volume thing is a VERY common misunderstanding.

I agree with u that 10 psi is 10psi. but the volume or amount of air does change. u will definately get more volume air with 3 inch charge piping vs 2 inch. there is more volume inside the 3 inch thus more air is getting to the engine. hope this clears things up a little.

tony1

Sorry, that's wrong. Do some more research...

sharkcohen

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by civic_ex_95 &raquo;</TD></TR><TR><TD CLASS="quote">I agree with u that 10 psi is 10psi. but the volume or amount of air does change. u will definately get more volume air with 3 inch charge piping vs 2 inch. there is more volume inside the 3 inch thus more air is getting to the engine. hope this clears things up a little.</TD></TR></TABLE>
Wrong.

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">NO NO NO NO NO!!! lol, Forget about CFM. If there is 10psi in the manifold on said engine, then it's 10psi, period. The only way you can change the amount of air that will enter the engine is to change the density. The only way to do that is to change the temperature. If the charge temperature is 80 deg., then it's doesn't matter how big the turbo is, the same amount of air is going in the motor. The engine is the restriction, and the restriction is what makes "boost". A smaller turbo will eventually not be able to keep up with the airflow requirements, and boost will drop. The amount of air the turbo can flow is irrelevant if boost is constant. If it's is flowing enough to maintain the same boost as a big turbo, then temperature is the only variable that can change the MASS of air entering the engine. Volume is fixed. So, on the compressor side you have temperature, which is efficiency (which is why we have compressor maps), and on the exhaust side you have exhaust backpressure. </TD></TR></TABLE>

Tony1, are you kidding? I am not sure if you are joking or not, but anyway, I have to disagree

Ever wonder why a large V8 engine could run a turbo at a very low pressure ratio yet be drawing in a lot of CFM? This would in turn, put that engine at a high HP/TQ @ specific PSI. The larger V8 engine is engulfing a lot more CFM @ XXXX RPM than a smaller 4 cyl engine also at the same XXXX RPM.

Now how does this all relate? If 10 PSI is constant and air volume does not change for a set engine other than air temp, then does that mean the change of cams, valve sizing, cam timing, larger exhaust, also has no effect? This can't be... Those changes would increase VE and efficiency of an engine because now the engine is engulfing more CFM at XXXX RPM. These changes also put the turbo at a higher CFM (higher X-axis) BUT at the same pressure ratio (Y-axis).

10 PSI is the restriction between the turbocharger and the engine (intake manifold or intake valves). With this as a known fact, the restriction point is now lesser restriction with improvements mentioned above, which means more air can get into the engine at the same 10 PSI and at the same RPM. Again, same PSI or pressure ratio, but higher CFM or lbs/min on the compressor maps. This in turn would mean more HP/TQ at the same PSI.

It's simply efficiency, just as what you also obtain from nice tubular manifolds, larger turbine and wheel, changes in cam timing, etc..

The only reason why a smaller turbo blows hot air is either: (1.) PSI has exceeded the recommend pressure ratio or (2.) Turbo is failing to supply CFM demand.

If you run a T25 turbo @ 10 PSI, but airflow rating is within the compressor map (ie: 190 WHP on say a D-series), the turbo will have no problems keeping a stable 10 PSI. It is only when the engine demand is higher than what the turbo could supply in which boost drops.

However, a T04Z for example, also at 10 PSI can produce a lot more power; not just because the air is colder or denser, but rather the exhaust side of the engine is a lot more efficient. This means the same 10 PSI restriction is a much lesser restriction at the intake valves, and more CFM can be allowed into the engine given the fact that the turbo has no problem supplying it

Jay_Sensing

Tony the Tiger, reading all of your arguments seems to me like we are arguing the same point, just wording it slightly different.

Si Shane

Based on what I understand the 10psi is only 10psi as it is a function of what cannot get out. IE the turbine restriction will change the manifold pressure if all things else remain equal. This is also relative to the intake restriction, but would the turbine or intake valves offer a greater restriction? From empiricy it seems as though the turbine, and boy do I understand what you said about the wheel vs. the housing!

All turbos push z cfm, and when your motor only flow y: there is a relationship between z & y, or f(yz)=psi.

Is that correct?


And to Jay-unless your wording is spot on then there is more to learn!