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Romans 2005 Toyota Echo - Back to 1300cc setup


Roman

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1 hour ago, Yowzer said:

Reminds me of a story from my old boss, building up a 2L Fiat twin cam race motor. He did all the math on cams intake and exhaust runners to get maximum power. His mate built the same engine with slap together parts and guess work.

Guess which was the better performer of the two?

This and people think their random assortment of high dollar aftermarket parts will all magically work in unison to produce the optimal result.

Testing testing testing is how you get results 

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Haha I expect you're right, although without a working engine (or a working car for it to go in) all I have at the moment is mucking about with spreadsheets! Interesting to see if they can point me in some sort of direction for when the other bits start falling together. Would be interesting to see if it bears any semblance to reality or not.

Very familiar with @kpr's videos. Awesome stuff. Was just as surprised at how well the peach slices did :D same with how poorly the super long intakes did, although that was before I knew about the water hammer theory being junk.

To answer some questions about the scribblings, yes it does account for the offset of the crank (and the piston pin, which moves things back in the other direction). No, it doesn't do anything with working out how far the atmospheric pressure migrates down the runner, nor determines when in the intake cycle is a good idea for the charge to be targeted. All far too complicated things to determine with my level of maths! Best leave that to the empirical testing. What it does do is give you an intake length range where the pressure wave will enter the cylinder between 3/4 and 7/8ths of the inlet cycle. Anything more precise is way too complicated man :D

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Calculators have there place getting you ballpark.  or if have no idea on starting point. can cut down on testing time, if that's the case.     Or at least a good learning exercise.  As a lot of people still seem to go with a blanket "shorter is better for high rpm, long is better for low rpm"    Yes if make the runner shorter it will push the tuning higher in rpm range.  The part they miss is, if make the runner longer and drag one of those previously unreachable peaks  down to where the engine naturally wants to make peak power. you have just had a big win. as said peak  you have pulled down, is stronger than if you shortened the runner,  to push a peak  up the rev range. Plus you get the benefit or pushing all those other peaks down the rpm range and gaining midrange power as well.   
you can see this in my videos pretty clearly. if the runner is too short and the peak falls off the end of the rpm range.  it chops the top off the power curve.  So yeah im actually using the longer runner to make more peak power which melts most peoples brains

There are of course other things to overcome than just length. but yeh, gets you most of the way there.

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2 hours ago, Yowzer said:

 

That is my theory, then it doesn't matter if the engine is a cast iron turd from the 60s, force feed it and all is good. 

I have wondered how much more power is lurking within, if I had roman/kpr levels of tuning smarts though  

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On 28/05/2022 at 14:26, BiTurbo228 said:

Haha I expect you're right, although without a working engine (or a working car for it to go in) all I have at the moment is mucking about with spreadsheets! Interesting to see if they can point me in some sort of direction for when the other bits start falling together. Would be interesting to see if it bears any semblance to reality or not.

Very familiar with @kpr's videos. Awesome stuff. Was just as surprised at how well the peach slices did :D same with how poorly the super long intakes did, although that was before I knew about the water hammer theory being junk.

To answer some questions about the scribblings, yes it does account for the offset of the crank (and the piston pin, which moves things back in the other direction). No, it doesn't do anything with working out how far the atmospheric pressure migrates down the runner, nor determines when in the intake cycle is a good idea for the charge to be targeted. All far too complicated things to determine with my level of maths! Best leave that to the empirical testing. What it does do is give you an intake length range where the pressure wave will enter the cylinder between 3/4 and 7/8ths of the inlet cycle. Anything more precise is way too complicated man :D

I've been thinking about this some more, apologies if I was initially dismissive etc of your work putting this together. 
Just venting my dissapointment with reality not often aligning to my own expectations on these topics. 
However in terms of your calculator, Is there something that you would you like me to do that's helpful for you? 
I've got a dyno plot of the motor running a known length intake (with bends at the end though) 
It's got very pronounced dips and peaks in the curve. 
If you like I can get a fairly accurate overall runner length dimension. 
But where do you measure to at the head end? Back of closed valve? 
I dont really have the right tools to find the point relative to TDC of when valves are opening and closing though.

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No worries man :) I guess I've got a lot of the whole 'reality not meeting expectations of theory' stuff coming up :D

A lumpy dyno graph and a measurement of your intake length for it would be dead useful yeah! Back of closed valve to the open end of the bellmouth would be perfect.

Could probably have a stab at guessing your cam timing and then if you do end up measuring it for any reason (not sure why you would TBH), could see if it's anywhere near close. Although lord knows what VVT does to tuned length intakes. Probably makes them somewhat redundant I expect as you can move your cam opening and closing time around wherever you like it (although your engine seems to have responded better to some lengths of inlet compared to others.

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39 minutes ago, BiTurbo228 said:

Although lord knows what VVT does to tuned length intakes. Probably makes them somewhat redundant I expect as you can move your cam opening and closing time around wherever you like it

This is an interesting point. Does VVT mean we can tune engines to suit a set runner length at different points throughout the rev rage? I guess it does. 

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Using his calculator a little earlier, it looked like 40 degrees of cam movement basically did the equivalent of having adjustable runner length by 200mm or so. 
Which makes sense, runner length is about catching the pulse in the right spot when the inlet valves are closing. 
VVTI means you move the catch point rather than the send point. 

But you still need to have your runner length set to a meaningful range to work across

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3 hours ago, BiTurbo228 said:

A lumpy dyno graph and a measurement of your intake length for it would be dead useful yeah! Back of closed valve to the open end of the bellmouth would be perfect.


So total intake length from back of valves to the tip of the inlet looks to be around 350mm 
The trumpets used in this case were curved, but have a fairly linear cross sectional area until right at the end 
image.png.f4042bc9b5c516f326feadf4fe718378.png


Then here's the dyno plot from this setup.

Peaks and troughs are very distinct! 

This is how many degrees of cam advance it was using through the cycle 

image.png.bbbdd939c6161bf022f403756074ca99.png

271649693_229588476009700_145501324279449023_n.jpg.1539b4e32b10162fbba9250d6fee2029.jpg

271716267_344794294316694_6517361878539680290_n.jpg.a845db679ec59579e448c9f0de03fe0a.jpg

And a video. It was really interesting to be in the room with bonnet open while car was running, you could feel the pulses from the intake hit your chest. 
Way more than I would have imagined 

 

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I've also been thinking about what you said about the pressure wave being generated in the cylinder, when there is peak accelleration of the piston. 
But would this be when it happens, would it be peak accel of the piston, or peak change in volume inside the cylinder
Like the first 10 degrees of travel and you might have expansion ratio of 200% (or whatever) 
But by the time you're half way down the expansion ratio of another 10 degrees crank movement might only be 20% (or whatever) 

This has all made me think that I've got an 8 channel oscilliscope and it's very easy to hook up a map sensor with a probe dipping into the port. 
I can setup an output on my ECU to trigger at each TDC event so there's a reference point for the scope.
Probably pretty easy to figure out when things are happening and why.

If you look at some of the peaks and then see if there's a dip at 50% rpm, it almost lines up as you'd expect...
The "not quite" could be because cam timing is different at each point, and just other contributing variables I guess

peaks.jpg.b9f320210f04f35eb27707e7c70ae5ad.jpg

Also a while back I had the thought that you can figure out which reflected waves you are looking at on a dyno plot, by the rpm spacing of them.
If you had a first reflected wave, and then a 2nd wave. The 2nd wave would happen at a 2:1 RPM ratio 
But then 3rd wave and 4th wave, you get a 2:3 ratio between rpm spacing 
And so on. 
The point of this is that you can theoretically see the rpm at which the other reflected waves would happen, outside of what's measurable.
So maybe if there was a big peak you just werent quite reaching, you could make your intake a little longer to try get to it. or whatever.
Another important implication is that if you know which reflected waves you are looking at, then if you assume that it's travelling at the speed of sound, then you know how long the tuned length is.
Which will help solve the mystery of whether the wave bounces back for the next engine cycle, or just to the end of the same induction event. 

In this example if I say one of the peaks is at 6550, and then look at what ratio I need to get next peak at 5400ish
6550 divided by 5400 is 0.836. 
Which is within ballpark of the 5/6 ratio. 
Then the next one is close too.


image.png.c855955d01401a5931cf87c14d0984c8.png


image.png.a8e04f5c5b25cb935c721b156d770c11.png

So then you can see that the 3/4 ratio wave is apparently happening at around 8700rpm. Which you cant see on the dyno graph as we didnt rev it that high on the day. 

One thing that will throw a spanner in the works if the wave is first generated at 50% towards BDC or whatever.
The first wave will start from that length of the bore, to the tuned end length of the runner. 
But when that wave reflects back to the head, any subsequent bounces will be bouncing off the back of closed valves which is a shorter tuned length. 
Then the final tuned length part will be something along lines of your 7/8ths or 3/4 wave distances on your calculator.
So there will be an offset for the first wave and last wave but all the middle ones should be the same.
However it should be close enough to validate whether the tuned length is the entire cycle or just start/end of induction.

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Think I will do a little bit of a revisit on intake runner lengths, now my engine has vvti.    I think the length I was using with fixed timing will be at least still very close to where it needs to be.  Tuning the intake to where engine where it wants to make peak power.  Then using the vvti extend the peak power both ways

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On 01/06/2022 at 14:17, Roman said:

The point of this is that you can theoretically see the rpm at which the other reflected waves would happen, outside of what's measurable.
So maybe if there was a big peak you just werent quite reaching, you could make your intake a little longer to try get to it. or whatever.
Another important implication is that if you know which reflected waves you are looking at, then if you assume that it's travelling at the speed of sound, then you know how long the tuned length is.

 

I wonder how much effect the air velocity has in the inlet. high rpm/air velocity would slow the waves outward path in the inlet?

Could be a reason for unexpected performance of odd inlet shapes, with different air velocities due to the diameter change, having an effect on the timing of the peaks?

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True, good point! 
Also something KPR mentioned previously, when he put the injectors in the outer position to test. 
The inlet then performed like it was slightly longer than it actually was, presumably because of density difference that the waves were travelling through.

Just those damn peach cans on the intake dyno test really rattled me aye. haha.

I've always had the idea in mind that the primary function of an inlet runner is to maximize mass flow (as in, if steady state mass flow goes up on a flowbench, you're winning) 
Then from there, you tune for pulses or whatever as a secondary thing.
But what I've come to realize is that it seems like you really can just brute force the mass flow issue by going bigger on pipe diameter, and it's very forgiving you dont lose much if anything.
The only time it seems to matter that you have a super duper mega efficient bellmouth shape for mass flow, is if your intake is so utterly tiny, that the easiest mass flow improvement would be to simply increase the pipe size.
Like race cars that run an intake restrictor, a good bellmouth design can make or break the whole car.

However peach cans is a really good example of that they flow "good enough" from a mass flow perspective, just through brute force. Despite seeming absolutely absurd.
Yet they still have the right tuned length to bounce some waves back in when the valve is closing.
If you've got a pressure wave banging an extra 10kpa at the valves when they shut, it probably doesnt matter if you're losing 2kpa on average from a crappier design.

I guess some of these generalizations change again once you start doing 20k rpm and reaching supersonic port speeds or whatever. 
All interesting stuff.

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Its pretty silly how far can oversize the inlet runners  with  only small negative effects  at low/mid rpm.    Which makes sense for the majority  of the 80's/90's  "performance" heads with massive port entries and runners.  easy just to overkill it and take a small hit low down.     going too small on the runner you can actually see engine hit a brick wall and flat line.  with only a small benefit down low.    unfortunately there doesn't seem to be any sweet spot that will get you a significant  gain down low without restricting top end.  If make the runner small enough to gain anything significant  low down,  it will loose top end.

Not saying there isn't something in getting the diameter right. but far less sensitive that you would think if err on the big side.

also, there are plenty of people out there that will show you big gains down low/mid  from a small diameter runner.   which is usually a band-aid  fix for sucky exhaust side. as your increasing intake pressure to overcome a reversion issue. they will have lost top end power doing so. 

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