stock port max flow rate? cough cough max hp
I've been doing some searching around the thread but can't seem to find any information on how well stock ports on a s4 TII will flow. I'm trying to calculate how well my turbo set up will mesh with my stock ports but it is difficult if I don't know the approximate maximum flow rate of stock ports. If there's anybody who can tell me how much power they made on stock ports that would be more than helpful too!
Thanks guys :icon_tup: ~Ant |
If you can find the square port area and the runner length (runner length doesn't include the plenum behind the throttle body) then you can get a close figure as far as flow rate is concerned at any given rpm.
|
I'm under the impression that not only the area of the ports but the bends and turns within the irons the ports take will effect the maximum flow as well, which is something I don't have the ability to measure. In my case it would be more time and cost effective to see if someone has reached the maximum potential of the stock ports and hence the maximum flow rate I would assume.
From an engineering perspective I feel knowing a rough estimate of that number would help greatly in planning ahead /deciding on what turbo to run, how much boost, expected power output, fuel requirements, etc. etc....once again, saves time and money....and stress :icon_tup: |
The intake manifold plays a big role in flow as well.
I don't think there's an easy way to calculate this on paper, you'll probably need to build a flowbench. |
Intake manifold is important only if it is in restrictive conditions. You could have a fire truck hooked to a garden hose and it will still only flow what the smallest restriction/cross section will flow. Oddly enough, this given is applicable to N/A and pressurized.
gd |
Wouldn't you think the ports would max out in flow before the manifold since they have the smallest cross sectional area?
|
max flow at what pressure ratio? increase the boost and you will flow more air
|
This website is siding more around 30 lb/min http://fc3spro.com/TECH/TURBO/compmap.html although that seems a little low even for stock ports..
|
Originally Posted by rx7 SE
(Post 9801469)
This website is siding more around 30 lb/min http://fc3spro.com/TECH/TURBO/compmap.html although that seems a little low even for stock ports..
Tell you what, just post the following info and I will give you a ballpark flow rate figure so you don't need to hurt yourself with higher-level physics... - What is your intended max boost level? - Are you using a stock intercooler or aftermarket front-mount intercooler? |
Let's see....I have a BNR stage III hybrid which flows about 40-47 lb/min max and I plan on running 15 psi once I settle on injector size and which EMS upgrade. I'm also running the stock top mount intercooler in conjunction with a coolingmist progressive water/meth kit to keep AIT's down under boost with such a small intercooler.
Thanks, ~Ant |
1 Attachment(s)
Originally Posted by Evil Aviator
(Post 9801535)
The engine's max flow rate without boost is about 16lbs/min, so I am not sure why you think 30lb/min is low.
Based on those Rx-8 numbers, I would be surprised if an s4 T2 really flowed as little as 16 lb/min without a turbo. That's only about 120 grams/sec. What's really interesting is that the Rx-8's 225 grams/sec is almost exactly the same amount of air my buddy's '05 Subaru Legacy 2.5GT flows with full exhaust and higher boost (16ps) on stock turbo. Rotaries flow a lot of air, even if the engine geometry is not the best for torque production or fuel economy. |
The stock top mount will be your restriction IIRC...
|
Originally Posted by arghx
(Post 9801657)
I don't know about on an s4 T2 with no turbo, but a stock Rx-8 can flow almost 30 lb/min without a turbo.
The RENESIS numbers in your readout are higher because: - The intake air temperature is below the SAE standard. - The RENESIS flows more efficiently than the 13BT, which is one reason why it makes more horsepower without a turbo than the 13BT does with one. Technically the RENESIS is slightly supercharged. - The RENESIS has a higher operating rpm. Math: (80cid * 8310rpm * 102% EV)/1728 = 393cfm * 0.07567lbs/cf = 29.79lb/min. I am guessing at some numbers here, and I am ignoring small factors like air moisture, but the numbers should be good enough for a compressor map SWAG.
Originally Posted by arghx
(Post 9801657)
Rotaries flow a lot of air, even if the engine geometry is not the best for torque production or fuel economy.
Originally Posted by sc0rp7
(Post 9801659)
The stock top mount will be your restriction IIRC...
|
Great information guys, I'm glad the things I'm learning in class are actually used out in the field.
Anyway, so to say a s4 TII motor flows 16lb/min with no turbo I would assume that is because the motor itself doesn't have the displacement ie, torque to flow that much air under its own will? So that is why we slap turbochargers on these engines, but, is 30 lb/min the limiting factor for stock ports? Would that be a safe assumption, if that were the case then my turbo/exhaust setup will significantly outflow this motor :(. That can't be the case because 30 lb/min is along the lines of 226 rwhp is it not, which is not that hard to get with just a stock turbo. I must be missing something then :scratch: |
have you read this? https://www.rx7club.com/spec-tuning-154/how-size-matters-478915/
|
heres a few..
first cars build thread: keep in mind this is a REW, but it is an unopened engine.. https://www.rx7club.com/single-turbo-rx-7s-23/another-bw-475-project-816447/ results: https://www.rx7club.com/rotary-drag-racing-167/stock-motor-enzo-racing-fd-goes-9-85%40142-9-mph-865403/ no stock intake here though.. theres also this car: this is also a stock port, but a RE.. https://www.rx7club.com/showthread.p...hlight=tearbo2 results: https://www.rx7club.com/single-turbo-rx-7s-23/my-goal-met-769rwhp-747542/ both around 700rwhp, one a bit above, and one a bit under. now if somebody could post some data on the performance benifits between REW or RE plates and TII ones, we'd be getting somewhere! |
Originally Posted by rx7 SE
(Post 9802216)
Great information guys, I'm glad the things I'm learning in class are actually used out in the field.
Originally Posted by rx7 SE
(Post 9802216)
Anyway, so to say a s4 TII motor flows 16lb/min with no turbo I would assume that is because the motor itself doesn't have the displacement ie, torque to flow that much air under its own will?
Math: (80cid * 7500rpm * 85% EV)/1728 = 295cfm * 0.069146lbs/cf = 20.4lb/min. Given 13B engine = 80 cubic inch displacement The rotary engine cycles all of its displacement each revolution of the output shaft, as do 2-stroke piston engines. A typical 4-stroke piston engine only cycles half of its displacement per output shaft revolution, so we would need to divide the displacement by half in this case, but fortunately we can ignore this step with rotary engines. Therefore, we can solve for cubic inches per minute by multiplying the displacement times the number of output shaft revolutions. I will choose the 7500rpm stock engine redline for this calculation, although you can solve for any rpm as desired. 80cid * 7500rpm = 600,000 cubic inches / minute. Now we come to something called "Volumetric Efficiency" (usually written as EV, Ev, or VE). That is a fancy term to describe how efficiently an engine cycles air. Some factors like intake restrictions, poor suction, and burnt gasses lingering inside the engine will reduce this efficiency, while other factors like supercharging and tuned exhaust will help increase it. The 13B engine has a volumetric efficiency of about 85% at 7500rpm, which means it only cycles about 85% of the amount that we previously calculated. Therefore, we adjust the equation to: 80cid * 7500rpm * 85% EV = 510,000 ci/min. A conversion factor is then introduced in order to convert ci/min to cubic feet/minute: (80cid * 7500rpm * 85% EV)/1728 = 295cfm Since modern compressor maps are in lbs/min, we then convert cfm to lbs/min by multiplying by the mass of air at a given temperature, pressure, and moisture content. Since moisture content is such a pain to calculate, and it makes very little difference in mass, most field work ignores this factor. Since the Garrett compressor maps are based on 85degF and 28.40inHg pressure, I will use the standard mass of air under this condition in the conversion: 295cf/min * 0.069146lbs/cf = 20.4lbs/min.
Originally Posted by rx7 SE
(Post 9802216)
is 30 lb/min the limiting factor for stock ports?
Originally Posted by rx7 SE
(Post 9802216)
Would that be a safe assumption, if that were the case then my turbo/exhaust setup will significantly outflow this motor
Ambient pressure: (80cid * 7500rpm * 85% EV)/1728 = 295cfm * 0.069146lbs/cf = 20.4lb/min. 2.0 pressure ratio (about 14psi boost): (80cid * 7500rpm * 85% EV)/1728 = 295cfm * 0.069146lbs/cf = 20.4lb/min * 2.0 = 40.8lb/min. 3.0 pressure ratio (about 28psi boost): (80cid * 7500rpm * 85% EV)/1728 = 295cfm * 0.069146lbs/cf = 20.4lb/min * 3.0 = 61.2lb/min. As you see, nothing changed but the turbo boost and the lb/min flow rate. I ignored some factors like pressure drop, but that should give you the main idea. Also, keep in mind that a turbo compressor map is a compressor map, which means that it deals with the statistics at the compressor inlet and outlet as opposed to the air filter or intake manifold.
Originally Posted by rx7 SE
(Post 9802216)
That can't be the case because 30 lb/min is along the lines of 226 rwhp is it not, which is not that hard to get with just a stock turbo.
Originally Posted by arghx
(Post 9802520)
have you read this? https://www.rx7club.com/showthread.php?t=478915
|
In depth response man! I appreciate you taking the time and explaining these things to me. I'm currently an undergrad in mechanical engineering with some motorsports on the side, so I've covered the basics including thermodynamics, fluid mechanics, materials, etc. etc. So in effort to retain everything that I'm learning at such a fast pace I apply it to our cars to see if everything works and how I can optimize these engines. You seem to have a lot of experience, I'm sure I have much more to learn :icon_tup:
~Ant |
Originally Posted by rx7 SE
(Post 9804925)
I'm currently an undergrad in mechanical engineering
Have you seen this website? There are some minor math errors, but otherwise the information is pretty good. http://www.gnttype.org/techarea/turbo/turboflow.html
Originally Posted by rx7 SE
(Post 9804925)
You seem to have a lot of experience, I'm sure I have much more to learn
We ALL have much more to learn. I have met some industrial legends who were shockingly lacking in some technical areas, which I have come to realize is part of being human. |
Porting improves performance, but doesnt mean you cant make good hp without...
just put on a bigger turbo and run more boost. yes you will increase lag and intake temps, but you can make plenty of power. J-rat had over 500hp on stock ports... |
Originally Posted by Furb
(Post 9805352)
Porting improves performance, but doesnt mean you cant make good hp without...
just put on a bigger turbo and run more boost. yes you will increase lag and intake temps, but you can make plenty of power. J-rat had over 500hp on stock ports... |
J-rat WAS running stock ports untill a vacuum hose to his wastegate melted and he blew his engine...
Now he has a ported motor. |
All times are GMT -5. The time now is 02:28 PM. |
© 2024 MH Sub I, LLC dba Internet Brands