13B Power @ 1 bar absolute pressure, to see what you might have if you MAN UP!

[RICE RACING]

You can see when you sort through the BULLSHIT that a well done street port makes pound for pound the same as a partial PP or full BP engine with non of the head fucks associated with poor fuel mileage, high idle, very high exhaust noise, exhaust back pressure sensitivity etc etc.

And you can equalize out the boost people run and see what the motor will do on its own, and project further on what it will do if you fit up the right turbo and charge cooler etc.

[Mitchocalypse]

Hmm. I've often thought about this exact concept and would have applied it exactly the same as you have but the more and more I thought about it, the more i found things that might throw off the approximation so I pretty much just dismissed the idea.

Have you tested how accurate this is? Maybe it's just the way i'm looking at it but it almost seems over simplistic. I'm sure it gives a reasonable approximation - but how accurate is my question?

The two biggest things for me are intake air temp and volumetric efficiency. Obviously i don't need to explain the fundamental gas law, but I was also under the impression that at higher rpms, internal combustion engines (n/a) could reach greater than 100% volumetric efficiency so the absolute pressure in the manifold (or combustion chamber) could be greater than 1 bar absolute.

The way I'm looking at it (and I know I'm missing some things) is that doubling the absolute pressure wouldn't actually double the power.

Sure it's a good approximation, but how good?

[RICE RACING]

Originally Posted by Mitchocalypse

Hmm. I've often thought about this exact concept and would have applied it exactly the same as you have but the more and more I thought about it, the more i found things that might throw off the approximation so I pretty much just dismissed the idea.

Have you tested how accurate this is? Maybe it's just the way i'm looking at it but it almost seems over simplistic. I'm sure it gives a reasonable approximation - but how accurate is my question?

The two biggest things for me are intake air temp and volumetric efficiency. Obviously i don't need to explain the fundamental gas law, but I was also under the impression that at higher rpms, internal combustion engines (n/a) could reach greater than 100% volumetric efficiency so the absolute pressure in the manifold (or combustion chamber) could be greater than 1 bar absolute.

The way I'm looking at it (and I know I'm missing some things) is that doubling the absolute pressure wouldn't actually double the power.

Sure it's a good approximation, but how good?

It's 100%

So long as you have the compressor map width and turbine to match i.e. BIGGER TURBO *to match your pressure ratio target, thus power target* (efficiency) and charge cooler big enough for the extra heat rejection. I have proven it in my own testing and that with rotary turbo drag cars I consult on. And its been proven over and over in many piston turbo examples most notable F1 1000bhp era.

Volumetric efficiency of stock ports is around 85%
My Street Ports around 105%
Bridge and Peripheral (many variations!) but say 110% (as used in turbo applications).
NOTE: Power differences are not just a function of this but where the power is made

The match between turbine to compressor (again I test this and have posted up many graphs not Howard Coleman like conjecture and personal theory) is so long as relationships are maintained PORTS are not the restriction never ever have been to ultimate power, all they define is where it is made due to charging efficiency at higher engine speeds.

(Turbo's are simple as stated. And ancillaries as well, if you are reading this thread and comprehend it so far you will be all over these basics too.)

The formula and how it works is proven

[RICE RACING]

So the base engine (aside from mechanical strength!) was and is never the issue, its the bolt ons and adaption of water injection or aftercooling spraying to keep charge temperature under control and so long as you have the appropriate turbo its a prefect linear relationship.

It is and can be swayed by these variables:

* If you are greatly reducing ign timing as boost increase
* If you are making vast changes to AFR as boost increase

Then you can have non linear discrepancies of over 25%!!!
But if you run water injected especially these boundary restrictions do not apply

To give you a practical proven example a BMW F1 turbo mapped on an engine dyno here (I have the dyno sheet!) is Australia did 802bhp @ 3.3bar with lambda of 0.79 @ 10,000rpm and at 5.6bar uses the same lambda and water spraying the IC it see's over 1350bhp That was the going rate at the time for the qualifying power output at that boost pressure

[Mitchocalypse]

Well I'll be darned

I gotta say, the thing I like the most about your posts is that you explain the theoretical side of things and then follow it up with an example that agrees with what the textbook says.

[RICE RACING]

Originally Posted by Mitchocalypse

Well I'll be darned

I gotta say, the thing I like the most about your posts is that you explain the theoretical side of things and then follow it up with an example that agrees with what the textbook says.

Thanks

That is how I teach (It's my profession) it adds credibility and separates the wannabe's from the ones who actually have done it

I like many others get sick and tired in forum world of reading crack pot theories or regurgitated information by overnight wonders who have never done anything of the sort. My idea is to understand the theory and then apply it myself, THEN talk about it. And back it up ........... odd concept I know to some lol.

You asked an excellent and insightful question before and I hope I explained it, back when I was doing tests on the standard ports and collecting data on everything I personally saw near a linear rise to the point where there was divergence between TIP and MIP (turbine inlet pressure and manifold inlet pressure) *read turbo becoming too small* so then I experimented with 1.00 to 1.15 and to finally 1.32 A/R turbine housings then to the point of the turbo itself being too small. So that is a critical point and lots of good engineering writing on the subject explains balance of gas flows between turbine to compressor. Second "mapping" considerations which lots dont talk about is excess fuel ratio's and spark timing, and tertiary considerations are the charge temperature and knock limitation of the fuel you use relative to the CR you choose to implement (inter related issues to a point).

But if all things are appropriate for the target goal then sky is the limit, so long as you do not exceed thermal capacity of critical engine components or mechanical strength, and it is advantageous to keep rpm low and vastly increase pressure as this is far far less stressful.

Wanted to keep it simple though, but hopefully this explains the "theory" is sound and proven in reality too

[RICE RACING]

Forgot to add, the real world examples I give are using stock std Mazda inlet manifolding.

edit *too much info!* you dont need to know and all of your real performance increases come from raising the absolute pressure to the level you need to make the power you want