Building a 10,000 rpm NA engine.

[oab_au]

Originally Posted by Dessertrunner

Correct me but higher revs shorter intake length?
That was how I understood it.
Tony

Yes that is the way it goes, but this set-up that I posted is the best length to keep a strong wide torque curve. I have tried to stay with the standard manifold length of 300mm, but although it develops another 27kw at 8000, it develops a resonance at 4000 that knocks a big hole in the torque curve, making it not as usable. Going to the 400mm length moves that resonance away from the usable range.

This is the best I can do to show what it looks like,

Harvey.

[Dessertrunner]

One point from the past that I want to mention was I asked the question,
"On a turbo engine what is the final compression ratio based on a given boast"

Now many years later I think there is a answer,
If the turbo engine is at 15lb boast approx then from before we know that the engine has approx double the quanity of air.
It would assume that if the normal NA engine has 10:1 compression ratio and you turbo to 15lb or double its volume the compression in terms of head load is the same as 20:1 NA engine.

Does anyone agree.
Tony

[icingdeath88]

Originally Posted by Dessertrunner

One point from the past that I want to mention was I asked the question,
"On a turbo engine what is the final compression ratio based on a given boast"

Now many years later I think there is a answer,
If the turbo engine is at 15lb boast approx then from before we know that the engine has approx double the quanity of air.
It would assume that if the normal NA engine has 10:1 compression ratio and you turbo to 15lb or double its volume the compression in terms of head load is the same as 20:1 NA engine.

Does anyone agree.
Tony

Yep, that's the basic idea. Not quite that simple though. An NA engine has a constant compression ratio throughout the rev range. A boosted, especially turbo setup, the compression ratio will vary depending on the boost level. The boost level is not directly proportional to the RPMs, because the turbo may be lagging or already spooled up depending on what's happening at the time. This is why tuning a turbo engine is such an important thing.

[svxfiles]

Originally Posted by Dessertrunner

One point from the past that I want to mention was I asked the question,
"On a turbo engine what is the final compression ratio based on a given boast"

Now many years later I think there is a answer,
If the turbo engine is at 15lb boast approx then from before we know that the engine has approx double the quanity of air.
It would assume that if the normal NA engine has 10:1 compression ratio and you turbo to 15lb or double its volume the compression in terms of head load is the same as 20:1 NA engine.

Does anyone agree.
Tony

Yes, I agree,

and as icing says the boost depends on RPM more than a supercharged engine would.

[oab_au]

I almost agree, if you talk 'compression pressure' changing, and not the 'compression ratio' that, does not change.

Harvey.

[Dessertrunner]

Originally Posted by oab_au

I almost agree, if you talk 'compression pressure' changing, and not the 'compression ratio' that, does not change.

Harvey.

Now Harvey here you go getting all techeonial on me, just joking. Okay so the only bit I care about is the compression pressure.

So Harvey I want to go to 14:1 compression by shaving the heads. How much should we take off? Also does you simulator show much difference in power from 10:1 to 14:1 at say 8,000rpm.

Tony

[oab_au]

Originally Posted by Dessertrunner

No Harvey here you go getting all techeonial all a on me, just joking. Okay so the only bit I car about is the compression pressure.

So Harvey I want to go to 14:1 compression by shaving the heads. How much should we take off? Also does you simulator show much difference in power from 10:1 to 14:1 at say 8,000rpm.

Tony

Well we got to use the right terms, or people will think we don't know what we are talking about.

I'll raise the ratio on the present one to 14:1 to see, tonight.

Harvey.

[oab_au]

Also I would not worry about the compression ratio yet, till we get the cam timing and lift finalizes, as we have to fit the valve heads on overlap into the chamber on TDC.

Harvey.

[Dessertrunner]

Originally Posted by oab_au

Well we got to use the right terms, or people will think we don't know what we are talking about.

I'll raise the ratio on the present one to 14:1 to see, tonight.

Harvey.

I am going to bet Harvey that the actual gaining power from increasing compression ratio on a Subaru engine is far greater then everyone say due to the flat nature of our engines. Plus I have experience at raising the compression on a Subaru engine and it stood up and bucked.

Tony

[oab_au]

Game enough to put a percentage on it?
Tom and Ice want to have a go at what % increase from 10:1 to 14:1?

Harvey.

[Dessertrunner]

Okay so the % is based on Simulator or actual?

[oab_au]

Originally Posted by Dessertrunner

Okay so the % is based on Simulator or actual?

It will be the same simulation that I posted, with just the com ratio changed from 10:1 to 14:1

Harvey.

[Dessertrunner]

So base case was 10:1,
My guess is 14%

[svxfiles]

My best guess is less than 10%.
For example;
Bowling's Compression Ratio -> HP CalculatorComputation Results:
Engine Horsepower (peak) is 230
Old Compression Ratio is 10.0
New Compression Ratio is 14.0
Computation Results:
Computed New Engine HP is 249, a 8 percent change

[svxfiles]

From Wallace Racing;
Your old Compression Ratio of 10 and HP of 230 is now calculated
as a Compression Ratio of 14 and 249.16 Horsepower.