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I was thinking today about how people can produce engines that
go past 10K before redline, and now its killing me to know how they can set a RPM as a Redline.

Is it something you see on a dyno, where power just stops?
or
Do they measure detonation or thermal breakdown or internal parts as they spinn faster?

And lastly, a built H22 w/ type S pistons and stronger rods and
stiffer valve train with say stage 2 cams has a higher redline correct, how could on tell what that would be?

Thanks:D
 

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I thought redline was the spot on the dyno when your power started to dip off.

I remember someone (marcucci or jacques) saying that they'res some equation depending on the size of the rods and pistons and blah blah. I'm sure they will chime in and tell you. But it more or less comes down to math.

and your redline shouldnt change until you start stroking/destroking the motor. I may be wrong but thats how i heard it.
 

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In a nutshell it comes down to piston speed. The lower the rod/stroke ratio the faster the piston is moving during the stroke. Even with reinforced components there is just a point when everything moves too fast for their mass and the engine will just self destruct. Don't expect to get a stock geometry H22 over 8500-9000 RPM as an absolute maximum unless you're only expecting it to live a 1/4 mile at a time.

Even with the reinforced rods and upgraded valve train w/o any change in the geometry like moving the wrist pin around and using some custom rods you still have the problem with very high piston speed per RPM. I wouldn't rev a street driven motor over 8k and if the S2 cams need more than that to get the power, bad design.....

Though why do you care where you rev to just so long as you can create power though the band that you have? Remember what RPM stands for... Ruins People's Motors ~TOO
 

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Why does increasing your stroke...increase piston speed. If you increase your stroke it will take longer for the piston to reach tdc, correct? So if it takes longer for it to reach tdc then a motor w/less stroke wouldn't the piston speed be less? Or is it simply a matter of increasing your stroke requires bigger rods and bigger rods have more mass, and will give into inertia quicker than lighter rods?
Thanks,
-Greg P
 

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I used to ask this question...

You can determine piston speed but things like side loading become that much more tricky. On an H22 you need to worry more about rod stretch and vertical loads than side-loads... on an H23, B20A, B21A, or other long-stroke motors you need to worry about side-loading more than anything.

For most engines, the first thing to usually go is the valves with valve float. Aftermarket valvesprings will fix this. Then you have to worry about the timing belt and tensioner and if they can take the additional load. If you have that all set, then you generally have to worry about the rods. A set of stronger rods can fix that.

When it comes down to it, there is no way to look at a motor and what's been done and decide what the redline should be to be safe. I'm not sure how many of you remember, but the ITR originally had issues with the high redline, like the Celica. People spun them too fast and bent valves. The S2000 has a similar issue. They all run towards the hairy edge of what the valvetrain will support.

For "proper" development of products like a mfr or race engine builder would use, you can get a machine called a Spintron to spin rotating components to identify (experimentally) where they let go. This obviously is not a cheap or easy thing to do and is obviously destructive testing- so you better have a pile of parts to test.

I say "proper" because it is BLATANTLY obvious to me that some companies, like Skunk2, don't test products before they are released. I have a set of mushroomed valves from them if you would like to see what poor product development looks like.

When it comes down to it, it's all about good judgement. There's no magic formula or any way to look at a motor and ID the proper redline. We know that stock H22's valve float somewhere above 9,000 RPM, so all you can do is try to better that. The bigger issue on the H22A is having the breathing to accommodate anything above 8500 RPM or so. Beyond that they just fall flat without some serious mods.
 

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precisionelite said:
Why does increasing your stroke...increase piston speed. If you increase your stroke it will take longer for the piston to reach tdc, correct? So if it takes longer for it to reach tdc then a motor w/less stroke wouldn't the piston speed be less?
Only if you lower your redline. At X number of rpms, a piston moving up and down over a 50mm stroke isn't going to have to move nearly as fast as a 100mm stroke will at the same number of rpms.

Or is it simply a matter of increasing your stroke requires bigger rods and bigger rods have more mass, and will give into inertia quicker than lighter rods?
This is also a factor. F=MA, so any increase in mass or acceleration will increase the amount of force seen on the components.
 

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precisionelite said:
Why does increasing your stroke...increase piston speed. If you increase your stroke it will take longer for the piston to reach tdc, correct? So if it takes longer for it to reach tdc then a motor w/less stroke wouldn't the piston speed be less? Or is it simply a matter of increasing your stroke requires bigger rods and bigger rods have more mass, and will give into inertia quicker than lighter rods?
Thanks,
-Greg P

The piston has to travel a greater distance in the same amount of time. Thus the speed is increased.
 

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When determining the "redline" or, rev limit of a motor there is only one factor you need to pay attention to... Where the motor makes power, period...

Usually +600 rpm past peak is about where you want to set your rev limiter...

Anything other than that, rod angles, r/s ratios, piston speeds, Intake manifold runner lengths/plenum volume, cam specs, header primary/secondary lengths, collector specs, valve train capabilities are all part of building the motor, not determining where a motor can rev to... You build the motor in accordance to what your goals are... Select cams that will work with your set up, not a set up that will work with your cams...

I mean, think about it... If r/s ratios, piston speeds, rod angles, etc, etc determined where the motor makes power do you think there would be motors out there with 102mm strokes, r/s ratios of 1.2x -1.3x making power up over 10,000 rpm?

All the above that was covered in previous posts is to prolong the life of a motor and help figure out what you are going to need to make the package a well working combination... Higher r/s ratios will increase the dwell time at TDC and decrease the affects of high piston speeds (does not decrease piston speeds what so ever) which is good, that will help the motor breathe up top but doesnt dictate where it makes power... Piston speeds, that will tell you what your goiing to need in terms of a cylinder head/port/chamber/cam/intake manifold/header combination but it wont dictate where you make power or where your rev limit should be set at...

Theres no way of determining where its going to make power with out throwing on the dyno... You can guess, but thats never very accurate...
 

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precisionelite said:
Why does increasing your stroke...increase piston speed. If you increase your stroke it will take longer for the piston to reach tdc, correct? So if it takes longer for it to reach tdc then a motor w/less stroke wouldn't the piston speed be less? Or is it simply a matter of increasing your stroke requires bigger rods and bigger rods have more mass, and will give into inertia quicker than lighter rods?
Thanks,
-Greg P
As many on the site have pointed out, it's simple physics. Speed = Distance/Time. If two engines are running at 8000 rpm's and one has 100 mm and the other 50 mm stroke. Then it's easy to see that the piston speed has to be greater on the 100 mm stroke to be turning at the same rpm. The higher the piston speed then the higher the wear, but this does not become a hugh issue until you approach the critical piston speed. I fogot what speed that is.
 
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