T22SED Engine redline RPM

[MMamdouh]

thats way too complicated man... thats why i love (N/A) engines.

MMamdouh

[Big P]

Just remember that horsepower is just Torque X RPM

Actually, horsepower is Torque X RPM/5252

5252 is the constant in that equation. That's why both torque and horsepower are always equal at that specific RPM. I understand what you are saying about the turbo and increased boost pressures. That is why I've been looking for a turbo that will have very high efficiency in the 5000-6000 RPM range because the more torque that I can make at 5252 RPM, the more horsepower I have also. As soon as you crest over the 5300 RPM mark *usually* the torque numbers start to drop whereas horsepower increases as long as there is sufficient airflow as stated before.

Lets say you manage to make 200hp at 5000 RPM then in theory you would make 400hp at 10,000 RPM

I can see where this theory might seem plausible but I don't think that it is. Doubling the horsepower an engine makes is not exponentially related to doubling the engine RPM. It all has to do with airflow. If you can double the airflow that was required at 5000 RPM to make the initial 200HP, then you can sustain the 400HP at 10,000 RPM as long as the air/fuel ratio remains the same. Look at the turbo cars. A T22SED has what, 135HP N/A?? Now, I can almost guarantee that with the proper A/F ratios and at exactly 14.7 PSI of boost(which as we all know is twice atmospheric pressure) the engine should make twice its output which would be 270HP or *acting* like a N/A engine that has 4.4L of displacement.

If you wanted to get technical, your 200HP@5000 RPM engine would end up having roughly 210.08 FT. LBS. at 5000 RPM and the 400HP@10,000 RPM would have the same torque value of 210.08 which you had already stated earlier. I don't know of any engine in the world that would keep the same torque output rating over a 5000 RPM spread but I do see the point that you are trying to make.

[PrecisionBoost]

Sorry.... I didn't have the exact equation with me ( I'm at my in-laws place at the time)

Here is some useless technical babble about horsepower vs torque...

James Watt (steam engine inventor) came up with a figure to gauge his engines back in around 1775

A strong horse could lift 150 lbs of weight 220 feet in one minute

So if you multiply the two you get a figure of 33,000 lb-ft per minute

To convert between horsepower and torque you would calculate the force at one foot.

So imagine a flywheel that has a 1 foot radius ( which is a 2 foot diameter )

The circumference of this flywheel is calculated as (3.14 X 2ft ) = 6.28 feet

So we divide 33,000 lb-ft per minute by 6.28 and we get our conversion factor of 5252

I know this is dry but there are probably one or two of you out there that might find this interesting.

[PrecisionBoost]

To get back to my point.... torque and horsepower are directly related.

It's the efficency of the engine that changes as you increase RPM..... the air fuel doesn't have anything to do with it.

Basicly..... at higher RPM there is more restriction.... so the engine can't pull in enough air.

So at 5000 RPM a 2.0L engine might only pull in 1.75 liters of air and at 10000 RPM that figure might drop to something closer to 1.5L

As such there is less air.... therefore less fuel (if A/F ratio stays the same).... therefore less power.

So in this case where you drop from filling 1.75L to 1.5L you would see a decrease in power of around 14%.

So on an engine making 200hp at 5000 RPM it might only make 343hp at 10,000RPM due to the drop in efficency.

It's like sucking air through a straw.... at some point the restriction will limit how much air can pass through the straw.

Anyways..... I gotta go.... I'm taking my daughter swimming (she's 3yrs old ) so she keeps hitting me with her doll and telling me to "come on... were going swimming"

Later...... Chris

[PrecisionBoost]

hmmmm...... that might not be right...

200hp / 0.8725 = 229.22hp at 100% eff

double that to 458.45hp and multipy my 0.75 = 344hp

Oh... I guess my "guess" was bang on.

Basicly I'm calculating with an 87.25% eff at 5000RPM and 75% at 10,000RPM

[mister_g]

You can tune your engine to make lots of horsepower at high RPM but it will allways cost you power and driveability at lower RPM levels.

To make a huge power gain through increasing the redline you need to do some serious head work to make it breath better.

So enlarging the intake and exhaust ports, intalling larger valves with undercut shafts, multiangle valve & seat job, longer cam duration / lift and polishing will let you make more power at higher RPM.

The down side is that the engine might not run at all under 1000 RPM... and at 1500 it would be "lumpy" with very little power.

This is due to the fact that you will have decreased port velocity at low RPM in order to make the engine be able to breath better at high RPM.

Thats why Honda's make VTEC with adittional valve openning only above higher RPM. Thats why all Honda's like TypeR like to rew, and have grate power output without turbos...

Honda S2000, 2.0, N/A, 240HP! And redline is around 9000rpm...
Thats why I love Hondas!