Mate - That was (or still is actually) a bloody joke. Crissakes, you can't take that seriously....Uhm - You say "max power has nothing to do with rev's" and then say in the next sentence "power is torque x rpm...."...? Huh? Obviously usuable power is greater at at certain engine revolutions. I understand all the scientific formula you are applying, no need to repeat it...

I am not saying "I must build a 7500 rpm inline six" at all. That was a figure that some people run their sixes at, quite happily. By working backwards from there I was hoping to find out what other peoples ideas were on the ways and means of achieving good results from a high revving six.

So far there has been a lot of positive input from a number of people, yourself included.

I don't subscribe to the theory that any one person "owns" a thread and there is happy discussion between people about bore sizes, stroke considerations, head flows etc etc.

And hey --- What is wrong with talking in theory and then trying to apply it to something real? Crissakes- that's how invention, of any sort, works.

I've learnt a bit from peoples input into this thread already, and if anyone feels like commenting on what they're thinking, or what they are actually building (as a few have via PM and email) then the thread is serving its intended purpose.

No - You're right. 33.33 is not where you'll get the most power out of any engine known to man.

Continue reading further and you would have found it was 66.66 (as I forgot to times it by two - Up stroke and down stroke...)

NOTE THE BIG LAUGHING OUT LOUD ICON

NOTE THE "ROLLS EYES" AT SELF IN SELF DEPRECIATING HUMOUR ICON TOO.

I've called it "mean piston speed" in my spreadsheet thingy and as it happens, that's what the WIKIPEDIA entry quoted above called it too. Very interested to see your spreadsheet - I made up the little spreadsheet posted above after reading your message with relation to making one with the more complicated speeds in mind.

I reckon it'd be interesting alright - not sure many people would give a s**t, but I would! I'm not good enough at maths to work out much more than what I've botched up already.

Cheers...!

ok knock yourself out....

so far i havent seen any suggestions on how to actually get more power out of an I6....

Where did you get that poorly written article fiend?

Have a look at this gem:



So the mean piston speed is limited by increasing the intake port velcity? WTF? I'd have my SAE membership torn up if I ever wrote a paper with comments like that in it.

hahahahahah. I see what you mean mate, but I think you may have mis-read the article...

It was part of the http://en.wikipedia.org/wiki/Formula_One_engines article, as quoted in original message.

I think the writer means that the PORT VELOCITIES are increasing as RPM rises and the intake can no longer keep with the demands of the displacement at high RPM.

If only he'd (or she'd) put in a comma or re-arranged the sentence or something or other.

Does that make sense now, or is it still a pile of poo?!

Better not tear up your membership just yet --- But maybe click on the link http://en.wikipedia.org/wiki/Formula_One_engines , sign in to Wiki, and offer an updated edit on the offending paragraph!

I thought they were talking about Volumetric efficiency as that was the topic of the previous paragraph.

Here's my little spreadsheet. It was originally for a single cylinder Yamaha MF150 laboratory motor but I've expanded the range so you can work out instantaneous piston speeds at all rpm and at any crank angle for almost any stroke and rode-stroke ratio you can possibly think of.

Edit: Its a bit rough but I'll debug it over the weekend and put up a revised version. its been over a year since i looked at it so I've forgotten most of it.

 

 

Attachments:

Lab_3.xls [33.5 KiB] Downloaded 217 times

was just playing around with a little calculator i found free somewhere on the net (had it a while but cant fathom it.)

Buy inputting where the stock 6 makes its peak power (4900) and then playing with torque input, Ive found that it takes about 225 nm at 4900 rpm to make the claimed 157kw (210 hp).

Its interesting that by increasing the peak point to 5500 rpm results in an increase of 19kw. not bad for a meager 600 rpm increase.

theoretically if you could modify the engine to produce the same torque at peak power as the stock engine, but only at 7,500 rpm, you would pick up 82 kw O_O (225nm @ 7,500)

its interesting to note that when peak torque occurs in the stock engine, its only a few horsepower from the peak power. 357nm @ 3000 according to this calculator is 152 kw, only 5 shy of peak. So it takes 1900 rpm to gain 5kw. But also indicates why the 5 speeds go so damn hard stock, as the closer ratio's keep it in a 2000 rpm power band so nicely

just for fun I input the peak torque of the stock engine and entered 7,500 rpm and it would theoretically produce 510 HP! 300 more than stock lol.

Thanks for sorting that out Grimbro.

I know damn well from driving hard and fast that there is more power when holding the car at certain rev's. Goes without saying.

I go back to what I theorised originally - With a free flowing head, suitable cam (not super high lift) and all the other changes we've been looking into, you possibly could get that torque figure to move up the rev range and provide a whole heap of power at 7500. Possibly. That's what this stockcar driver was telling me anyway. He sits at 7500 from the get-go and does pretty well in this countries stock championships...

Not sure you'd ever get an extra 300kw mind...! In theory perhaps, but honestly?!!!!!!

That is bloody interesting reading though Grimketel. Found a link so we can all have a play? Or maybe you could upload it somewhere and point us to it?


XCABBI --- That spreadsheet looks like the bees knees alright... Mind telling me why you put so many hours into producing it and has it ever resulted in anything practical being produced?

300 HP fiend HP. which is 223 kw.

still massive though, and not feasable in the slightest to be making that torque at that rpm with that bore and stroke combination. At least not without forced induction.

It doesnt have the cubic capacity to be moving that much air.

I dont have a lnk, as stated Ive had it for ages but cant quite figure it all out.

Its called : Virtual Engine Calculator 2005, Challenger Engine Software, LLC.

maybe searching that will come up with something.

Personally its all theory at that rpm, the money require and metals required to spin the i6 that fast reliably you might as well build a monster v8 (you would want to be using metals like chrome -moly and titanium all over the place to make it reliable). 6500 is more doable on a day to day drive basis. still would require a better bottom end to stop it from grenading.

For a uni assignment last year. For that experiment we had to disassemble a motor, measure the piston and conrod weights, bore stroke, rod length. Calculate the moment of inertia of the conrod. Then we were given a PV diagram of the engine at 4000rpm. From all of that we performed 4 bar kinematic analysis of the engine and worked out the velocity and acceleration of each of the links. (piston, crank big end and conrod). Factoring the PV diagram we also did a force analysis and worked out the instantaneous power the engine was making at a set crank angle and rpm.\

Another one I've done is to determine the max operating rpm before you get valve bounce. That one was time consuming as you have to use a dial indicator to work out the valve lift for the entire profile at 5 degree intervals.

That spreadsheet so far can only work for side valve motors or direct acting valve motors (such as motorcycle engines). Pretty much any engine that doesn't have rockers. I can modify it to factor in the inertia of the rocker but i would then need to model the rocker in 3d and get the drafting software to calculate the moment of inertia for me. But we all know the contact patch between the cam/pushrod and rocker and also the valve stem/rocker changes with each position. This is what makes it a royal b**ch to work out. Over the summer I'll have another go at it and see where i end up.

XCABBI ---
My goodness me. That is one serious thought process you have going on there. Are you at all interested in phenolic spacers and where to put holes in bonnets? Would be interesting to see what you come up with on those subjects!

GRIMFELLA ---

Click on logo for the big picture

these figures aren't right, make sure you use metric units, as the calculator seems to use imperial.
the engine makes 225lbft @4900 which is 305nm. At maximum torque it makes 111kw.

The forumlas are Power(kw@rpm)=(torque(nm@rpm)x rpm)/9549 or Power(hp@rpm)=(torque(lbft@rpm)x rpm)/5252
and at 7500rpm with 357nm it would make 280kw

SHYUN = at 7500rpm with 357nm it would make 280kw

And that, is pretty much the end of the argument regarding power at revolutions. Now, if anyone has any further ideas on how to produce it....

What do you want to know? Temp distribution through the spacer or the air speed with the supposed increased runner length? I could knock up some excel spreadsheets but i need to collect some data first. Can't just pull numbers out of thin air.



It is safe to say that the only way to make that sort of power without building a one run hand grenade is to use forced induction.