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Discussion Starter #1
22B ...
Again a more positive reply I did the maths while CEM was busy closing the 937 bhp thread:mad: shame he did this as we are all beginning to move forward positively:D

I am interested in the equations but feel you must have missed something.

Assume Mario revs to 8500 (I know thats on the low side), 3000cc 1 bar of boost =>
((3000/16.39)*8500*0.85/1728) * (1 + 1) * (1.5) = 2295

Let us know when you have located the book.:smokin:
 

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was about to correct a mistake as I indicated, but didnt get chance to edit.

It is divided by 1.5 at the end.

I also believe there is a 0.5 to mulitply which I believe accounts for the engine needing two complete rotations for all the cylinders to suck in their charge capacity.

inshort divide your answer by 2 x 1.5 x 1.5 and that will be the true value.

But I think you will find mario revs very high and runs much more boost than 1 bar.
 

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Discussion Starter #4
22B.
Yes I thought about the engine revolutions thing a lot as I created this thread.
My thought was that 1 rpm is the time between a cylinder firing once and then firing again i.e the combustion cycle.
Yes I know this means the crank rotating through 720 but it probably depends on what the definition or the rpm is?

Revolutions of the crankshaft or combustions cycle.

To be honest I do not know the answer but maybe someone who does can help me out here?

PS I know Mario will rev to 10000+rpm and will probably boost to 2+bar. I was using conservative figures.
 

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Thanks to spending far too much time on the Net I read Mario used 11,500rpm as his sustained maximum but has hit 12,500rpm in short bursts. As far as turbo boost goes I don't know what his maximum is (does the word 'maximum' have any meaning to him?) but he has posted a figure of 3.3 bar.

If you run this through the formule, what sort of power do you get (bearing in mind his engine is 2700cc, not 3000)? Probably more power than God...

MDG.
 

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It is a serious amount of power!


rpm is revolutions of the crankshaft, not complete four stroke cycles, othjerwise we would ahve a nomenclature problem when discussing 4 stroke, 2 sroke, wankel, and "other" engines.

I am assuming this also because the otical crank position sensor on my modified timing wheel (required to run a pectel ecu on an impreza) records one rpm for every passing of the 360 degree marker.
 

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Discussion Starter #7 (Edited)
Ok ran 2700cc at 11500 rpm at 3.3 bar through amended formula where we divide by 2 to allow for rpm

((((2700/16.39)*11500*0.85/1728)/2) * (3.3 + 1) )/ (1.5) = 1335

Which isn't that far away!

Perhaps slightly on the low side though, since when I run mine or Henry's figures through this I get
((((2800/16.39)*8000*0.85/1728)/2) * (1.5 + 1) )/ (1.5) = 560.
We both have dyno sheets showing 600+ from TJ using less rpm than this.

And please do not deviate onto the dyno arguement anyone!
 

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no it isnt at all

That was the whole point of what I said in the thread.

Marios is about the only massive power car I know of which fits in with the formula.

I must stress this isnt my formula, nor is it perfect. It is meant to be used as a rule of thumb to calculate what is possible.

The reason I mention it is that a lot of the cars, which are famous for their high horsepower simply do not compute with this formula, as they do not rev high enough to extract the power they claim.

Imperfections in the formula should be able to yield quite a difference, eg. the assumption that each cubic foot of air is required for 2/3 bhp. This will vary to some degree, and as boost, rpm, and capacity rise, being proportional, the accuracy of this figure will be moe significant.

It's not just foreign cars which dont seem to quite fit, but some uk cars too. I dont know personally of the claims of peopleon this board, but try it out with some example you are aware of.

It is for this reason that I tend to ignore rolling road figures and only rely on engine dynos for power figures. As I also said on the other thread, I think timing statistics such as quarter miles are more indicative of a cars state of tune, plus these also translate to fun factor on the road.

A car with 1 million horsepower driving one wheel with no grip is not going to be too impressive to drive.
 

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The reason I mention it is that a lot of the cars, which are famous for their high horsepower simply do not compute with this formula, as they do not rev high enough to extract the power they claim
Math & theory aside, surely the 0-400m, 0-300km/h, 0-1000m & top speed runs prove something???!!! I mean just look at what GTR demo cars in Japan are achieving! Sure they run AV gas, but a result is a result! You can chat all day about theory but what counts is results...and those are only achieved in the real world with infinite variables.

Just my 2yen's worth:)
 

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22B said:

It is for this reason that I tend to ignore rolling road figures and only rely on engine dynos for power figures. As I also said on the other thread, I think timing statistics such as quarter miles are more indicative of a cars state of tune, plus these also translate to fun factor on the road.

yep, completely agree.

The theory holds a lot of water (not perfect will admit), as a result it forces me to question a lot of the power figures I always see (mostly subarus, not just skylines). It is because of this that the only thing I cannot argue with is the performance times. BHP is almost worthless.

When I was young, I didnt even think about bhp, all I cared about whilst playing top trumps was 0-62 or top speed. ironically that was probably the right move.

on another note, I would like to echo the sentiments of others, with regard to what was said ont he other thread. Avgas is all well and good, but not really convenient for everyday use.

The first person who intended to map my car on the dyno (french incidentally) insisted on using race gas, his spec of injectors, turbo, ecu, compression etc. I quickly declined his offer, as race gas is simpy not a viable option for an everday car. regardless of availability, cost is prohibiting.

These cars surely become dedicated straight line cars with so much horsepower. I can only presume they come from massive turbos with odd torque curves, which I cant imagine would make great drivable cars. Obviously I havent driven a mega horsepower skyline, so please those who have feel free to correct me.

I would just have thought that if your goal is to achieve incredible quarter mile times, it is a waste of a car such as the skyline to one for this purpose. One of the best handling track cars there is, to be confined to going in straightlines all the time.

Especially when better times can be achieved using cheaper running gear in a space frame type chassis which weighs nothing.

Not saying I wouldnt like one of these skylines, but it isnt the perfect tool for the job, unless you want a car that can be driven to and from the drag.

Thats why I was so impressed with ronnie at elvington. The other cars that considered themselves such a threat to the skyline big boys all turned up on trailers, with teams of mechanics, and ran race gas.

Ronnie turned up, competed reliably all day, then left.

Must admit I was more than impressed to see him come second on the handling circuit. testimony to the handling/driver as well as the outright performance of the car.
 

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209mph tells me a lot more than a dyno run of xxx.x amount of hp, or even less the formula of what that engine is suppose to produce.

I have always been a firm believer that a dyno will only tell you if something is wrong with the car, or help trying to tune the car. Other than that, its not that darn helpful in comparing it to each other. Heck from one day to the next at the same dyno, you would be hard pressed to put out the same readings.

You can say hp is smaller or larger till your blue in the face. I am pretty sure time is a constant no matter where you are in world. The best judge is time, either on the 0-60, 1/4 mile, 1.5 mile, or track.

Does that formula take into account of port velocity, size of the valves, fuel type, spark, timing, lobe profile, LSA, duration, lift, air temp, intake temp, dew point, barometric pressure? These all do play apart of the factoring of hp, don't they?


I am not tring to flame anyone, just trying to learn.
 

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Power

"I am pretty sure time is a constant no matter where you are in world."

Thats my quote of the week- you can't argue with that..............

Guy
 

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actually that isnt true.

As you appraoch the speed of light time slows down, slow strictly speaking, the fast you go, the less time it takes you to get there!


but the speeds we are talking about, are not relevant here. You do experience it though. Everytime you go on a plane you experience less time than the people on the ground you left behind.

we are talking femtoseconds difference.

The formula is based on fundamental requirement for oxygen in order to extract the energy from the fuel.

I think the factors you are talking about are incorporated into the 1.5cfm/bhp part, but you would have to check with corky bell or someone more familiar with the formula, such as pat, although I am sure someone with a strong grounding in theory such as mycroft will have an opinion.

I must admit, when this was first explained to me, I did ask what about turbo sizing and compression ratios etc. but I was never given a clear answer,
 

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If we wait long enough the GTR might achieve light speed

some aussie scientists reckon 'c' is slowing - totally irrelevant but this is the theoretical section?

I'll get me coat


Iain
 

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If we incorprate 1.5cmf/bhp into all those variables and I put out 300bhp according to the formula, then I change my duration, lift, lobe ramp, LSA, air temp, timing, fuel pulse, and fuel octain I will still get 300bhp, since the formula says 1.5cmf/bhp is the standard?

I am sure by changing those variables, I can make an engine put out 90-400hp.
 
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