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Old 04-08-2002, 03:38 PM   #51
4sfed 4
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Quote:
Originally posted by 8Complex


I like torque, it is what makes you go, horsepower is nothing but the rating of which how easily the particular motor is making that torque.
Power is what makes you fast!

Torque can be changed with gearing, power cant.

In short, without getting into a discussion that has been beaten up on the internet too much already------

If torque was all that mattered, why doesnt everyone run a turbo diesel? Youd have 200 hp and 500 ft lb at your disposal. Run that against the same car with 500 hp and 200 ft lb. Who do you think will win?
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Old 04-08-2002, 03:55 PM   #52
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torque, is what pushes you in your seat. The work the car get's out of the torque produced is what makes you fast. Work = Horsepower. High torque, low HP engines just do a poor job of converting the torque into work at high RPMs. You can't feel HP.
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Old 04-08-2002, 05:06 PM   #53
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Quote:
Originally posted by Jewbaru
torque, is what pushes you in your seat.
Yes!

Quote:
Work = Horsepower.
Work / Time = Power (i.e., 1 hp = 550 ft lbf / sec)

Quote:

High torque, low HP engines just do a poor job of converting the torque into work at high RPMs.
They arent making torque at high rpm! Its not a matter of "converting" it. Torque gets "converted" in hp the same way everytime based on the often quoted formula.


Quote:
You can't feel HP.
Thats true.
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Old 04-08-2002, 06:20 PM   #54
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Quote:
Originally posted by 4sfed 4
They arent making torque at high rpm! Its not a matter of "converting" it. Torque gets "converted" in hp the same way everytime based on the often quoted formula.
Don't forget, they aren't doing much in the way of revving high either. What you said about not producing torque at high RPMs is what I ment by saying they were doing a poor job of converting their torque to HP.
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Old 04-19-2002, 01:40 AM   #55
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Default Volume vs. Mass

There are advantages to running boost other than effective compression ratio. Although there is the same volume filling the cylinders at 14.7 psi of boost you are effectively pushing twice the mass of air (and fuel) into the combustion chamber, which should yeild greater power if properly applied. High compression is more efficient, but sometimes yields the side effects such as heat and detonation. This volume would also be somewhat reduced if the charge air is hotter, and thus less overall mass at BDC, so that a 2 liter engine with 14.7 psi boost will not necessarily produce the same power as a 4 liter engine.

I think the issue of what effective compression ratio your engine can handle is a good one.

Can you cool rapidly?

Do you have strong rods for the initial expansion shock?

Is the chamber and piston head properly shaped?

Forged aluminum pistions?

These are all factors effecting the effective compression ratio.

I am building up an SVX engine. Rebello racing builds the 3.3 Liter and 2.2 L engines for racing and airplanes. At high boost these engines must be modified to dissapate more heat or they melt down or detonate. That is why I have been looking to hear what success people have had running 10:1 compression on their 2.5 L RS, as it would be somewhat comparible to my SVX engine.

Porche runs 9.4:1 compression in their engines with about 12 psi boost. They have piston sleaves that are made to reduce friction. The cylinders and heads are made to reduce heat. Engine management and control are also a must. fuel is also important as a higher octane fuel will burn cooler.

Bottom line is what are people running succesfully on the subaru engine at 91 or 93 octane? What is the acceptable effective compression ratio for our engine? How can it be improved (cooling or slicker internals)? What is your ultimate power goal?

Using your ultimate power goal coupled with the effective compression ration, then it just becomes a function of how much to boost is needed to achieve the goal without loosing too much bottom end power.

Race fuel can be used at the track then all bets are off.
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Old 04-19-2002, 01:44 PM   #56
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I plan to hit the track this weekend, weather permitting, on 93 octane pump gas and 12-13 psi.

My TB fuel injectors seem to cool down the intake air temps at the MAP sensor, similar to water injection, but without the antidetonation properties of water injection. I am still seeing in the neighborhood of 80% intercooler efficiency with my air/air IC which does help.

Is it cheating if I put ice in my intercooler watersprayer bottle?

Larry
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Old 04-23-2002, 10:21 AM   #57
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Default 12-13 psi

Hey larry. How'd it go this weekend?
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Old 04-23-2002, 01:25 PM   #58
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$30 and 6 hours later, waiting for only two runs since they were so busy...

Bogged the 1st launch because the clutch keeps slipping if I slip it, so I have to dump it instead. And, my new 1st is 15% taller than stock, and 10% traller than 1st in a WRX, so it likes the clutch to be slipped a little to launch and I can't do that. And, since the track is so sticky when I dumped the clutch only the front wheels spun and when they hooked up revs dropped from 5,000 to 2,800 and bogged = 13.9 @ 97

Second and last run of the day I hit 2nd gear going into 4th and after hitting 8,500 rpm I coasted through the lights all freaked out = 15.1 @ 65 mph

Bah!

Larry
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Old 04-23-2002, 01:26 PM   #59
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Plus, I was only building 10 psi in 1st gear, and 11-12 psi in 2nd - 4th since it warmed up. That's like 8-9 psi at sea-level.

Time to gut the second cat or get a 3" downpipe made up...

Larry
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Old 04-23-2002, 07:31 PM   #60
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Default times

The 13.9 isn't too bad. Still faster than a Rex.
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Old 09-07-2004, 08:22 PM   #61
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so 2 years and 4 months later... can anyone sum up everything that was said?
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Old 10-03-2004, 12:15 PM   #62
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So, if I am correct... which I may not be...

isn't the point of a turbo, forcing air into the cylinder, to make the cylinder push down harder with more explosive force? ie: getting more static CR?

Let's take this example...

If you take a 10:1 compression EJ25, it breathes in ~614cc per cylinder.
If you take an 7:1 compression EJ25, it breathes in ~614cc per cylinder.

Lets just use these numbers.

if 79mm stroke and 100mm bore gives you a 2481cc engine (2.5L)...
then 10:1 CR is about 248cc of area where everything is squished.
and in the 7:1 CR is about 345cc of volume of area above the piston.

Now, doing the math... isn't 854cc of mixture packed into 345cc of volume of space the same power output as 614cc packed into 248cc volume of space? (854cc of mixture is the amount needed in the 7:1 engine for it to have the same static CR of 10:1)

Doesn't 12/16 = 3/4? The whole time I'm reading this, someone out there saying that a lower compression boosted engine with more boost is going to have more mixture in the cylinder (true) than the less boosted higher cr engine, and so therefor going to make *more* power? How can it make more of anything if the static compression (345cc/854cc = 248cc/614cc) is the same?

if there were two engines, one at 13:1 CR, and one at 8:1 CR, and the turbo motor pushing 24.25psi. if the turbo motor were able to have the turbo spooling at exactly the right amount of psi to make the static CR be the same as the 13:1 motor, and be able to do it through the whole RPM band (idle on) then wouldn't the power output regardless of rpm be exactly the same?

And furthermore, if you had two IDENTICAL (cams, everything) engines, except that one was the 13:1 CR, and the other 8:1 with 24.25psi, then at the point where the boosted engine reached 24.25 psi, wouldn't that RPM in the other motor bring out the same EXACT hp/torque numbers? (assuming the engines are identical and both at the same timing)

I think I'm right. Static CR = static CR regardless of if there is more "mixture" in the cylinder... 854cc of gas/air mixture in a 354cc area doesn't make more power than 614cc of mixture in 248cc of space. It makes the same. (but turbo engines have to spool... so... you don't have as much torque as the engine that has the same peak static CR but has it all across the bandwidth.)
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Old 09-12-2012, 07:11 AM   #63
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Quote:
Originally Posted by bsquare View Post
One of the flaws stated directly in that article is that it is specific to superchargers and superchargers aren't as effective in making a lot of boost from a small package as turbochargers. You can easily bolt on a turbo to push 30psi, but a supercharger to do it will be sticking out of your hood.


Ben
You are so wrong with your assume I run a raptor centrifugal in my 2.5i @ 10 psi at redline don't go over 5k till forged internals... CR is 10.1 but really it's 9.7:1. Any ways compression is fine but yes 9.0:1 or even 9.2:1 will work. Reason for lower is for u boost happy turning uppers lol Either way love my Supercharger 220whp 340 tq getting ready too twin carge it with either screw vane for low torque and centrifugal for high end. Air to Air works awesome and 10 psi and an intercooler on a SC lol lets jus say charge is also cool
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Old 09-12-2012, 11:40 AM   #64
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Quote:
Originally Posted by VIsubi View Post
You are so wrong with your assume I run a raptor centrifugal in my 2.5i @ 10 psi at redline don't go over 5k till forged internals... CR is 10.1 but really it's 9.7:1. Any ways compression is fine but yes 9.0:1 or even 9.2:1 will work. Reason for lower is for u boost happy turning uppers lol Either way love my Supercharger 220whp 340 tq getting ready too twin carge it with either screw vane for low torque and centrifugal for high end. Air to Air works awesome and 10 psi and an intercooler on a SC lol lets jus say charge is also cool
he is right in saying the physics of getting a blower to push high psi is not an easy thing to do, he said nothing about the limits etc of a stock engine
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Old 09-12-2012, 02:05 PM   #65
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8 year bump, woo hoo!!
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Old 09-12-2012, 03:39 PM   #66
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Damn zombie-necro-thread..... Good info in here for those that cared to read it all.


~Josh~
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Old 09-19-2012, 02:33 PM   #67
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Quote:
Originally Posted by JonofScio View Post
So, if I am correct... which I may not be...

Now, doing the math... isn't 854cc of mixture packed into 345cc of volume of space the same power output as 614cc packed into 248cc volume of space? (854cc of mixture is the amount needed in the 7:1 engine for it to have the same static CR of 10:1)

I think I'm right. Static CR = static CR regardless of if there is more "mixture" in the cylinder... 854cc of gas/air mixture in a 354cc area doesn't make more power than 614cc of mixture in 248cc of space. It makes the same.
Adding more to this necro-bump

If you have 850cc's of burning mixture you are going to produce more heat and more energy than 615cc's will. The pressure will stay higher longer inside the cylinder as the piston moves down, imparting more turning force to the crankshaft.
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Old 05-20-2018, 12:35 AM   #68
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And 16+ years later LOL!!!

This is a good read - I love looking at different schools of thought when it comes to building power. Since this thread was started new technologies have been developed, and old technologies have been honed and improved upon.

Something I'm itching to do is exploit the daylights out of ceramics - I'd love to coat the pistons, combustion chambers, exhaust ports, cylinder walls... anything that sees a flame, coat it in ceramic. It reflects heat back into the combustion process, providing for a more complete burn. Plus, that coating has much less friction than oil on steel, freeing up even more power. Add to that the advent of gapless piston rings, and suddenly the engine isn't losing ANY intake charge to blow-by. Ever. So now this engine is burning ALL of its fuel with no leakage, doing so more completely due to the ceramic coating on everything, with less friction thanks to that same coating... and now with these gapless rings it can do so more reliably and with less maintenance. No blow-by means no soot or raw gas getting in the oil, meaning more miles between oil changes.

Now, enter ceramic bearings.

They already make turbos with ceramic ball bearings and titanium impeller shafts. The ultimate in quick/fast spooling, in essence a smaller turbo making bigger boost quicker. They even make ceramic differential, wheel, and axle bearings now. They're much lighter, much tougher, and MUCH less friction than steel bearings. They aren't cheap by any stretch, but when you consider the potential they have in differentials and transmissions both manual and automatic, we have the ability to greatly improve the efficiency of how the engine puts power to the ground. There are even coatings to reduce friction between gears, now. A win-win really, because less power loss means better fuel economy. Theoretically, a more efficient, less powerful WRX can outperform a more powerful, conventional WRX - all other things being equal.

I'm stoked to see - maybe even find myself able to use - all this stuff in a build of my own one day.

Last edited by Stites; 05-20-2018 at 12:39 AM. Reason: forgot something
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Old 06-01-2018, 12:00 PM   #69
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Originally Posted by Stites View Post
And 16+ years later LOL!!!

This is a good read - I love looking at different schools of thought when it comes to building power. Since this thread was started new technologies have been developed, and old technologies have been honed and improved upon.

Something I'm itching to do is exploit the daylights out of ceramics - I'd love to coat the pistons, combustion chambers, exhaust ports, cylinder walls... anything that sees a flame, coat it in ceramic. It reflects heat back into the combustion process, providing for a more complete burn. Plus, that coating has much less friction than oil on steel, freeing up even more power. Add to that the advent of gapless piston rings, and suddenly the engine isn't losing ANY intake charge to blow-by. Ever. So now this engine is burning ALL of its fuel with no leakage, doing so more completely due to the ceramic coating on everything, with less friction thanks to that same coating... and now with these gapless rings it can do so more reliably and with less maintenance. No blow-by means no soot or raw gas getting in the oil, meaning more miles between oil changes.

Now, enter ceramic bearings.

They already make turbos with ceramic ball bearings and titanium impeller shafts. The ultimate in quick/fast spooling, in essence a smaller turbo making bigger boost quicker. They even make ceramic differential, wheel, and axle bearings now. They're much lighter, much tougher, and MUCH less friction than steel bearings. They aren't cheap by any stretch, but when you consider the potential they have in differentials and transmissions both manual and automatic, we have the ability to greatly improve the efficiency of how the engine puts power to the ground. There are even coatings to reduce friction between gears, now. A win-win really, because less power loss means better fuel economy. Theoretically, a more efficient, less powerful WRX can outperform a more powerful, conventional WRX - all other things being equal.

I'm stoked to see - maybe even find myself able to use - all this stuff in a build of my own one day.
Personally I would steer clear of ceramic coatings for anything inside the combustion chamber on our cars. Think about what is downstream in the exhaust flow - the turbocharger. If those coatings fail - and that can happen - then you can have damage to the turbine wheel. Look into surface treatments that microfinish the substrate material like WPC for a safer method of reducing friction.

I have seen people sing the praises of ceramic coatings for the entire combustion chamber in vintage cast iron muscle car engines, but there's no turbo downstream in those cases.
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Old 07-25-2018, 04:37 AM   #70
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Quote:
Originally Posted by Stites View Post
And 16+ years later LOL!!!

This is a good read - I love looking at different schools of thought when it comes to building power. Since this thread was started new technologies have been developed, and old technologies have been honed and improved upon.

Something I'm itching to do is exploit the daylights out of ceramics - I'd love to coat the pistons, combustion chambers, exhaust ports, cylinder walls... anything that sees a flame, coat it in ceramic. It reflects heat back into the combustion process, providing for a more complete burn. Plus, that coating has much less friction than oil on steel, freeing up even more power. Add to that the advent of gapless piston rings, and suddenly the engine isn't losing ANY intake charge to blow-by. Ever. So now this engine is burning ALL of its fuel with no leakage, doing so more completely due to the ceramic coating on everything, with less friction thanks to that same coating... and now with these gapless rings it can do so more reliably and with less maintenance. No blow-by means no soot or raw gas getting in the oil, meaning more miles between oil changes.

Now, enter ceramic bearings.

They already make turbos with ceramic ball bearings and titanium impeller shafts. The ultimate in quick/fast spooling, in essence a smaller turbo making bigger boost quicker. They even make ceramic differential, wheel, and axle bearings now. They're much lighter, much tougher, and MUCH less friction than steel bearings. They aren't cheap by any stretch, but when you consider the potential they have in differentials and transmissions both manual and automatic, we have the ability to greatly improve the efficiency of how the engine puts power to the ground. There are even coatings to reduce friction between gears, now. A win-win really, because less power loss means better fuel economy. Theoretically, a more efficient, less powerful WRX can outperform a more powerful, conventional WRX - all other things being equal.

I'm stoked to see - maybe even find myself able to use - all this stuff in a build of my own one day.

not to burst your bubble, but the ceramic bearings in turbos dont allow you to make more power just like ball bearings dont allow you to make more power. turbos are still octane limited and you look at these guys with their smaller turbos having to push 30+ psi to get the power out of a smaller turbo.
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