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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 04-08-2008, 10:19 PM   #41
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Keep in mind that you can get several different sized turbine wheels in the 48 housing. Most of the OE t3 housing are stage 1 48AR and can be cut "up" to a stage 2, or 3. I'm running an OE Mercedes 48AR with a stage 3 wheel now. The bigger wheel helps relieve some of the top end flow issues associated with the smaller housing.
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Old 04-08-2008, 10:47 PM   #42
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Yes we can. I'd like to know why E85? I'm pretty sure I read that there's less specific energy in E85 than regular gasoline... something like 20%... which means you're gonna need a lot more liquid. I don't think 550's are going to get you 300whp if you need 20%more fuel than gasoline. And 350whp seems like more.
You might be looking into some big RC's which are gonna cost $$$.

Do a search for "mild build". There are several good threads out there that tell you how to build a motor to handle 300whp. Rods, pistons, rings, and some headwork are almost mandatory. OEM pistons are pretty strong if you keep the knock under control. Most guys see stock rods bend before the pistons melt during a knock event. Forged rods, tri-coated stock pistons, upgraded rings, and a 3angle valve job will see you safely able to push 300whp for a long time. For a goal of 350whp, you're definitely in the realm of forged low-compression Wiseco pistons. The going rate for a mild build, without forged pistons is $2500-$2800 with somebody else doing the work. If you're gonna go with forged pistons and get a little fancier with the port/polish and maybe an upgraded valvetrain, ARP studs, you're looking at $4k... but that gets you 400whp and some longevity.

Try not to gauge your build around your Honda experience too much or you'll be disappointed in how much $$ it takes to make RELIABLE hp in these cars. The BP head is early 80's engineering and is the weak point in making power... it simply runs out of flow. Nothing about the Honda head will translate. You can make up a lot of ground in the head with somebody who is a magician with a Dremel... but even a $2k BP head won't flow what a stock Honda B series will.

The clutch to hold 300+whp is gonna be $400+. The 5spd tranny is at it's limits at 300whp unless you drive like Grandma. The 6spd are known to handle 400whp. For that power, a 3.6 dif will get you back the use of 1st and 2nd, but a 4.30 or even 4.10 just means 1st=$$$straight to Tire Rack.

Wheels and tires to put 300whp down safely are gonna run you $1k.
A little suspension work might be in order... shocks and sways at a minimum... $500-$2000 depending on new/used/choice.
I'd go with some brakelines and pads for safety.
Rollbar?
Tranny/Dif fluid=$75
3" Enthuza=$400
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Old 04-08-2008, 11:12 PM   #43
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Quote:
Originally Posted by Braineack View Post
There's something wrong on your setup then, even with my extremely restrictive exhaust i never saw boost or torque drop.
I'll find out soon enough. I suspect it could be either my 2.25" crush bent cat back and 2.25" cat, or a problem with the turbo XS bleeder type MBC. We'll see, when the enthuza and BEGi gear arrives.
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Old 04-08-2008, 11:14 PM   #44
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Originally Posted by samnavy View Post
I'd like to know why E85?
Probably because E85 has an octane rating of ~103. Sure it will take more E85 to make the same power as 93 octane gasoline but it will probably be safer.

The problem with E85 is that it has a high sensitivity rating, that is it's resistance to detonation decreases with load.
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Old 04-09-2008, 12:17 AM   #45
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Originally Posted by Arkmage View Post
I'll find out soon enough. I suspect it could be either my 2.25" crush bent cat back and 2.25" cat, or a problem with the turbo XS bleeder type MBC. We'll see, when the enthuza and BEGi gear arrives.
Found your problem.
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Old 04-09-2008, 10:31 AM   #46
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the equation is to measure to amount of airflow volume that your displacement assuming 100% VE can displace.

the formula is: Volume of Air (CFM) = RPM X Cubic Inches / (1728 x 2)

The displacement of our 1.6L is 97.7 cu.in. We have a four stroke engine; the intake valve on a cylinder opens once every 2 revolutions of the engine. So, for every 2 revs the engine takes in 97.7 cu.in. of air.


Quote:
Originally Posted by opek View Post
Why do you keep saying pounds = mass and not volume, clearly I understand that. My first post addresses the relevancy of using a simple cfm -> lb/min conversion to a turbocharged motor.
I converted the CFM of the exhaust flow to lb/min simply because turbine maps from Garrett are displayed in lb/min and not CFM.

example:





Quote:
Originally Posted by opek View Post
Ok, let me try again. I don't think I am explaining myself very well. The conversion you used factors in pressure and temperature, but the pressure you use in your calculations is 0lb. I don't care if the turbine can flow 0lb of boost, I care if it can flow 24lb of boost. An equation to determine ideal turbine size must take into account desired airflow.
I did not factor in pressure or temperature. I didn't need to. Like I keep saying, the amount of boost you are running has little effect on the exhaust flow. While you may have more mass in the flow, it's still the same volume. The amount of change it may give to the final numbers, in my mind is trival. I'm looking at two A/Rs .48 and .63. One is good for 17 lb/min, the other 21 lb/min. which will i be closer to without going over?

If you wanted to take those factors into account to get a closer idea of the exact volume, then you'd apply the Ideal Gas Law to the CFM you first calulated.

The Ideal Gas Law is: PV = nRT


Where P is the absolute pressure, V is the volume, n is related to the number of air molecules, which is an indication of the mass (or pounds) of air, R is a constant number, and T is the absolute temperature (460 + intake temps) .

To get pounds of air: n (lbs/min) = P (psia) x V (CFM) x 29 / (10.73 x T)
To get the volume of air: V (CFM) = n(lbs/min) x 10.73 x T / 29 x P (psia))


To take is a step further, since the actual amount of air that flows into the cylinder is somewhat less than ideal. We factor in volumetric efficiency. 15psi in your intake manifold doesn't mean 15psi filled into the chamber before ignition.

So we determined that we can flow 198 CFM through the engine....but alas maybe the engine also sees 90% VE. so therefore, the flow through the engine may only be (198 x .9) 178 CFM.

Quote:
Originally Posted by opek View Post
I guess I just don't understand how this equation tells us anything about the turbine to suit my goals vs. someone who is looking for 200whp. Right, volume and weight are different. The more air you move, the more power you make; MAP is a function of the turbine as much as it is of the exhaust, head, cams, and manifold itself.
The more mass doesn't mean more flow. You can stuff a skinny kid into a locker. you could also pack my fat *** into the same. The volume is still the same, the mass is now.

How does it relate to your turbine? because your ******* exhaust spins the damned turbine, which determines the speed of your compressor wheel.

If you look at the turbine map, you see two axises. PR and Flow. You will always flow 198 CFM at 7000RPM, and plot it against the PR.

So, it's import to know you have a turbine that working within it's efficiency so it spins faster and spools quicker without being too large or too small. Pick one too small and you'll choke it up and you'll suffer from boost drop and increased temps. Too large and it may not spool how you want it, but it will make more power once it does spool.
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Old 04-09-2008, 12:33 PM   #47
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Negatory. Why do you think you need a t4 turbine wheel and a large t4 housing to make 800whp on a 1.8liter honda motor?

let me edit a hint in for you: It's not because the 110CID honda motor is flowing 15lb/min at 7000rpm.
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Old 04-09-2008, 01:41 PM   #48
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this is why; larger a/rs make more power & you need a larger turbine wheel exducer diameter to drive a compressor at various air flow rates.

again, approximately the same volume of air is drawn in as the piston moves down regardless of engine speed, load, or intake manifold pressure. The volume is the cylinder displacement. However, the density of the air that is drawn in varies quite a bit.
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Old 04-09-2008, 01:47 PM   #49
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Right, and your dumb *** said that regardless of how much air the compressor is flowing into the engine, the exhaust pipe sees 15 lb/min. That is ******* so incorrect, I don't konw how you haven't apologized for saying it. You go to a t4 turbine wheel and housing not because a t3/t4 can't spool, but because no t3 wheel/housing combo is going to efficiently flow the 80lb/min the compressor is sending into the motor.

Because MAP depends on the turbine and the compressor, you can't just talk about one side of it.
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Old 04-09-2008, 01:49 PM   #50
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Quote:
Originally Posted by Braineack View Post
then apply the damned Ideal Gas Law and change the multiplier....is still doesn't change the fact that you can only displace so much air, regardless of how much boost. so while i may see 14 lb/min through my exhaust, you may see 12, who the **** cares, what are you arguing again?


so to sum up:

**** ton of boost in the intake = 15 lb/min through the exhaust
no boost in the intake = 15 lb/min through the exhaust
It's not just people on this site who are laughing at this post.
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Old 04-09-2008, 01:54 PM   #51
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one here's one less.



turbos don't increase your displacement. they may increase your VE, not your displacement.
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Old 04-09-2008, 02:04 PM   #52
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aww come on Scott. I like this guy.
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Old 04-09-2008, 02:08 PM   #53
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15psi in the IM means we completely fill the cylinder up with 15psi of boost and shoots straight into the exhaust during overlap....Hell, boost shoots out of the exhaust, duh. We drive the car on boost, the boost pushes the pistons down (creating torque) and spins the turbo at the same time.
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Old 04-09-2008, 02:25 PM   #54
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The guy had a point scott, I hope you didn't ban him for that. I still think he's right to, and your comments about flow earlier were wrong. You could admit you were wrong instead of draging on about "displacement", volume, and all that. I'm still hung up on how you think the same poundage goes through the exhaust irrelevant of what goes in the intake. I'm pretty sure that poundage that goes in tries to expand back when it comes out, but builds up pressure because of the restriction (turbine) in its way.
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Old 04-09-2008, 02:37 PM   #55
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Why was this guy banned again...?

Booo
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Old 04-09-2008, 02:41 PM   #56
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im not wrong. opek had no points other than i was wrong. explain to me why im wrong.


DISPLACEMENT = VOLUME

MAP = PRESSURE

PRESSURE VOLUME


I only converted engine CFM to lb/min since the garrett turbine flow maps are in lb/min. still flow. the temp and pressure of the air must be know to correctly convert this. however it's the density ratio, not the pressure ratio you use for the conversion....so again, boost pressure does not factor in.
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Old 04-09-2008, 02:57 PM   #57
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Originally Posted by Braineack View Post
im not wrong. opek had no points other than i was wrong. explain to me why im wrong.


DISPLACEMENT = VOLUME

MAP = PRESSURE

PRESSURE VOLUME
You keep saying this, but it just shows how much of what I write you don't understand or choose not to read. Volume corrected for density (ie: pressure) describes the mass, and corrected CFM = mass/time. lb/min = mass over time.

Mass != volume, right. That is why your point in this thread is moot, because you are not considering dynamic pressure in the intake manifold.

My point is that you need to consider desired airflow (or power) to decide on a turbine. The turbine is more concerned with being able to flow the air the compressor pumps, rather than the air a naturally aspirated 1.8l is flowing.

Of course I'm right, braineack said 1 bar absolute pressure in the intake manifold produces the same amount of exhaust flow (mass/time) as 2 bar aboslute pressure in the intake manifold.

rofl.


And he also called me a complete moron, after he used a bunch of math he doesn't quite understand.
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Old 04-09-2008, 03:01 PM   #58
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this is the part where it all gets messy,

every one stay tuned,

brain and opek round 2
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Old 04-09-2008, 03:08 PM   #59
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next time ill ask Garrett to post their turbine air flow rates in cfm versus lb/min.

I don't need to factor in the pressure ratio in the intake manifold. only the density ratio of the air outside the car.

the compressor compresses air to fill a certain volume in the intake. the pistons further compress this air with fuel, and displace a certain amount of volume, this exhaust spins the turbine.
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Old 04-09-2008, 03:10 PM   #60
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But you didn't account for that! holy **** man, just say "I'm sorry I was wrong."

You still haven't responded to my point, and keep saying I have none. You need to consider power or flow goals to choose a turbine, not the flow of a naturally aspirated motor at sea level.

And just to be an *******, think about the dynamics of the system. What determines airflow? How we measure airflow may be a better question, speed/density or mass air flow. What determines density? Is it related to MAP? Directly related?

Density is a function of the turbine and the compressor, and the head and exhaust and intake manifold and cams and etc. Your math assumes the density of the air in the motor is equal to 1 bar at 120*F. That's absurd, we are concerned with a dynamic system that will be flowing 30+lb/min into the motor and the density is going to be dependent on the turbine. For that reason we must focus on turbine flow with relation to desired power output.

The Pressure Ratio that you are referring to is a way to describe the efficiency of the compressor, but you used sea level and 120* F as a measure of the air IN THE INTAKE MANIFOLD.

No one is concerned with the pressure ratio in the intake manifold. Ratio with respect to what? Ambient air? Exhaust manifold? Cylinder at x crank angle and y cam angle? Come on, man.
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