why do honda engines make so much more power with less boost
there are many variables to this equation
the vtec system is one
head design which is very efficient
and you are also comparing awd to fwd
so driveline loss
I still love the honda design and plan to build another monster which
most likley will outrun my Evo on the track meaning road course
I just happened to have sold my original Honda to get an evo
Honda also has killer F1 type technology behind their designs
everything just works when you have that kind of budget behind you
we had a 550hp Civic back in the early 90s (the Viet Lam, Gary Shih days)but got no respect and coverage because we were east coast.
they just do make alot of power
check youtube for the K20 NA Hatch beating up on an Evo
It also helps the chassis are very light
some can be almost 7-800 pounds lighter
now im getting way off topic
the vtec system is one
head design which is very efficient
and you are also comparing awd to fwd
so driveline loss
I still love the honda design and plan to build another monster which
most likley will outrun my Evo on the track meaning road course
I just happened to have sold my original Honda to get an evo
Honda also has killer F1 type technology behind their designs
everything just works when you have that kind of budget behind you
we had a 550hp Civic back in the early 90s (the Viet Lam, Gary Shih days)but got no respect and coverage because we were east coast.
they just do make alot of power
check youtube for the K20 NA Hatch beating up on an Evo
It also helps the chassis are very light
some can be almost 7-800 pounds lighter
now im getting way off topic
there are many variables to this equation
the vtec system is one
head design which is very efficient
and you are also comparing awd to fwd
so driveline loss
I still love the honda design and plan to build another monster which
most likley will outrun my Evo on the track meaning road course
I just happened to have sold my original Honda to get an evo
Honda also has killer F1 type technology behind their designs
everything just works when you have that kind of budget behind you
we had a 550hp Civic back in the early 90s (the Viet Lam, Gary Shih days)but got no respect and coverage because we were east coast.
they just do make alot of power
check youtube for the K20 NA Hatch beating up on an Evo
It also helps the chassis are very light
some can be almost 7-800 pounds lighter
now im getting way off topic
the vtec system is one
head design which is very efficient
and you are also comparing awd to fwd
so driveline loss
I still love the honda design and plan to build another monster which
most likley will outrun my Evo on the track meaning road course
I just happened to have sold my original Honda to get an evo
Honda also has killer F1 type technology behind their designs
everything just works when you have that kind of budget behind you
we had a 550hp Civic back in the early 90s (the Viet Lam, Gary Shih days)but got no respect and coverage because we were east coast.
they just do make alot of power
check youtube for the K20 NA Hatch beating up on an Evo
It also helps the chassis are very light
some can be almost 7-800 pounds lighter
now im getting way off topic
back on topic. if we're just talking about max hp, then i don't think Vtec has much to do with it. if you don't have Vtec, just run a cam with the same profile as the Vtec high lob and you will get the same top end. Vtec just give you more under the cure power with the lower cam lob. most pro drag car use Vtec Killer/Eliminator to reduce valve train weight, they just run the high lob since the engine will never be below 6k rpm during a race.
if i remember correctly, Honda engineered Vtec to be used in F1 but it got banned so they put it on a production car and was first seen on the 89 NSX. Honda did not invent variable value lift (earlier system have been used else where) but they were the first to put it on a production car.
Last edited by honda-guy; Feb 10, 2007 at 08:50 AM.
Newbie
Joined: Jan 2005
Posts: 88
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From: Columbus, Ohio
The GT28RS will be at about 72% and the GT3076 will be at 77%. This WILL translate to more power but not much 5-10HP-ish. Not the amount of power that would justify the expense. An increase of 5% efficiency does NOT translate to 5% denser charge let alone 5% more power. Again, we are talking compressor side.
The T3 based GT30R will flow more on the turbine side than the T2 based potato hence improving VE and making more power... the point is the extra power did not "come" from the larger compressor... The engine is able to take advantage of the extra blow the GT30R provides since the overall VE was improved.
I know you understand this... my initial point was to clarify the point that by themselves larger compressors, or perhaps more specifically, compressors with more potential DO NOT create more power at a lower boost levels, psig.
Newbie
Joined: Feb 2007
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From: ghetto
Internet Myth...
A given engine can ingest only so much air period. Installing a turbo with more potential flow will not generate more power at the same boost pressure unless... UNLESS... by installing the larger turbo you also reduce back pressure (better flowing turbine side) hence improving its ability to ingest more air, i.e. VE. A larger turbo may also be more efficient at a given PR and provide more power since the charge is cooler but not by much unless you are comparing a GT3076R to a T3-60 or something. A real mismatch. A better comparo would be a GT3071R to a GT35R or similar.
All things equal a larger turbo does NOT make more power at a lower boost level.
Here is why...
Pressure is just resitance to flow. 10 psi out of a 50 gallon tank with 50psi is the same as 10psi out of a 100 gallon tank with 100psi. The larger tank with higher pressure has more potential but if the engine cannot process that potential what is the difference? None.
The ONLY way to get more power at a lower boost pressure is to improve on the engines ability to breathe, or it's Volumetric Efficiency by reducing the resitance to flow. This can be accomplished by improving the flow before the head (intake), at the head (porting, cams, valves) or after the head (manifold, turbine, exhaust).
Honda heads flow more than the Mitsubishi heads is the simple answer to this question. For all those VTEC haters out there... remember MIVEC is Mitsu's version of VTEC. Too bad more Hondas aren't RWD or AWD. All that power and no way to get it to the ground... The Nissan SR20DET head flows well too, not as good as the Honda though and the Suby heads cannot compete with any of them.
A given engine can ingest only so much air period. Installing a turbo with more potential flow will not generate more power at the same boost pressure unless... UNLESS... by installing the larger turbo you also reduce back pressure (better flowing turbine side) hence improving its ability to ingest more air, i.e. VE. A larger turbo may also be more efficient at a given PR and provide more power since the charge is cooler but not by much unless you are comparing a GT3076R to a T3-60 or something. A real mismatch. A better comparo would be a GT3071R to a GT35R or similar.
All things equal a larger turbo does NOT make more power at a lower boost level.
Here is why...
Pressure is just resitance to flow. 10 psi out of a 50 gallon tank with 50psi is the same as 10psi out of a 100 gallon tank with 100psi. The larger tank with higher pressure has more potential but if the engine cannot process that potential what is the difference? None.
The ONLY way to get more power at a lower boost pressure is to improve on the engines ability to breathe, or it's Volumetric Efficiency by reducing the resitance to flow. This can be accomplished by improving the flow before the head (intake), at the head (porting, cams, valves) or after the head (manifold, turbine, exhaust).
Honda heads flow more than the Mitsubishi heads is the simple answer to this question. For all those VTEC haters out there... remember MIVEC is Mitsu's version of VTEC. Too bad more Hondas aren't RWD or AWD. All that power and no way to get it to the ground... The Nissan SR20DET head flows well too, not as good as the Honda though and the Suby heads cannot compete with any of them.
A given engine can ingest only so much air period. Installing a turbo with more potential flow will not generate more power at the same boost pressure unless... UNLESS... by installing the larger turbo you also reduce back pressure (better flowing turbine side) hence improving its ability to ingest more air . . .
A simple boost gauge only reveals the conditions of the intake manifold, not the exhaust manifold, yet that is very influential in determining mass airflow potential.
Some 3rd gear VATTACK!
this sounds like its becoming a very closed minded conversation...kinda like the subaru boards
I on the other hand show love for any car that is impressive
hence you learn from one and apply to another
it helps when you worked at a great speed shop
not an import shop but one that caters to everyone
V8 to 4 cylinders.
Keep an open mind people
you can learn somethings from the old fogeys who run 8 cylinders that will easily beat anyones car on any given night
no motor is better
they each have their own given aspects
and it would be nice to be able to engineer that one motor that does it all
I on the other hand show love for any car that is impressive
hence you learn from one and apply to another
it helps when you worked at a great speed shop
not an import shop but one that caters to everyone
V8 to 4 cylinders.
Keep an open mind people
you can learn somethings from the old fogeys who run 8 cylinders that will easily beat anyones car on any given night
no motor is better
they each have their own given aspects
and it would be nice to be able to engineer that one motor that does it all
Newbie
Joined: Jan 2005
Posts: 88
Likes: 0
From: Columbus, Ohio
Larger turbos DO have larger hotsides, and therefore, since manifold pressure is a function of resistance, a larger turbo flows greater air mass at the same point of pressure (resistance) than a smaller turbo, all else being equal. This is why a larger turbo delivers greater power at the same indicated pressure as the smaller turbo. The indicated pressure is the same, but if one examines the MAF signal, there is a substantial difference.
A simple boost gauge only reveals the conditions of the intake manifold, not the exhaust manifold, yet that is very influential in determining mass airflow potential.
A simple boost gauge only reveals the conditions of the intake manifold, not the exhaust manifold, yet that is very influential in determining mass airflow potential.
My point was not to include the turbine... I am just talking about the compressor side... as you know.
Newbie
Joined: Jan 2005
Posts: 88
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From: Columbus, Ohio
Ah, but the turbine side has to be considered, simply because any given turbo always consists of a compressor AND turbine, and both influence mass air flow vs. indicated manifold pressure. If we want to speak of compressors only, that would be restricted to blower applications.
As far as that 15 psi, a 35R is flowing more air mass to reach 15 psi vs. 15 psi indicated with a smaller turbo. Again, all a boost gauge does is indicate manifold pressure, nothing more. If you really want to know what's happening, install a pressure gauge on the exhaust manifold and compare. At 15 psi, that 35R will indicate less exhaust manifold pressure, and that is where the additional mass airflow results. After all, there is a big difference between a small turbo making 15 psi on the intake with 10 psi in the exhaust, vs. a 35R making 15 psi with 3 psi in the exhaust (hypothetical numbers).
To give a real world comparison of two different compressor wheels with the same hotside, on a 2g DSM, I ran two turbo identical except for the compressor wheel and the machining required to fit it in the compressor housing. The wheels were a regular old 20g (~49lb/min wheel) and a gt35r compressor wheel (~65 lbs/min). Running them both on the same setup, at the same 25 psi, airflow was identical at about 46-47 lbs/min. At this point the larger turbo made for a slower car due to the much increased lag (700 rpm increase in boost threshold at 25 psi). But of course the advantage to the larger turbo is that it was possible to increase the boost significantly on race gas, while the 20g only had another 2-3 psi left in it.
If both compressors are within their limits, you won't get a significant gain in airflow on the larger one at the same boost. Compressor efficiency will play a role in power production, but in reality, FMIC efficiency is FAR more important. It's not until you gain some flow through the turbine side, as Ted states, that you start to see meaningful increases in power output.
If both compressors are within their limits, you won't get a significant gain in airflow on the larger one at the same boost. Compressor efficiency will play a role in power production, but in reality, FMIC efficiency is FAR more important. It's not until you gain some flow through the turbine side, as Ted states, that you start to see meaningful increases in power output.
Newbie
Joined: Jan 2005
Posts: 88
Likes: 0
From: Columbus, Ohio
To give a real world comparison of two different compressor wheels with the same hotside, on a 2g DSM, I ran two turbo identical except for the compressor wheel and the machining required to fit it in the compressor housing. The wheels were a regular old 20g (~49lb/min wheel) and a gt35r compressor wheel (~65 lbs/min). Running them both on the same setup, at the same 25 psi, airflow was identical at about 46-47 lbs/min. At this point the larger turbo made for a slower car due to the much increased lag (700 rpm increase in boost threshold at 25 psi). But of course the advantage to the larger turbo is that it was possible to increase the boost significantly on race gas, while the 20g only had another 2-3 psi left in it.
If both compressors are within their limits, you won't get a significant gain in airflow on the larger one at the same boost. Compressor efficiency will play a role in power production, but in reality, FMIC efficiency is FAR more important. It's not until you gain some flow through the turbine side, as Ted states, that you start to see meaningful increases in power output.
If both compressors are within their limits, you won't get a significant gain in airflow on the larger one at the same boost. Compressor efficiency will play a role in power production, but in reality, FMIC efficiency is FAR more important. It's not until you gain some flow through the turbine side, as Ted states, that you start to see meaningful increases in power output.
This is the point I was trying to make originally... I must not have been very clear... thanks for doing so.
I think you were pretty clear, I just like to add real world examples whenever possible. Especially in this case since it is quite rare that you get a chance to change the compressor wheel and not the turbine wheel, which I believe was Ted's point. And it's a good one. Any real gains from a turbo swap at the same boost pressure will be attributed to the turbine side upgrade.