10,000 RPM SR20VET head on HLAs?

[jspaeth]

I was at a shop with my buddy this weekend getting his RB26 Skyline tuned and met a bunch of guys that have a couple of built SRs among them.


The one guy is running a RWD S13 SR bottom end with a VET head, using OEM VET cams.

He said he plans on revving it to 10,000 RPM.....with HLAs and OEM VET cams.


Normally, I would discount this as someone who is clueless, but these guys were completely legit and seemed to REALLY know their shit, having built/raced/tuned many engines.


Can someone explain to me if this is reasonable or not, and if so, why?

Why is it that you can put in aftermarket springs/retainers/cams on a regular RWD SR20 and can't really safely rev past 8,000/8500 RPM, yet these guys are saying they can rev a non-solid OEM head to 10,000 RPM?

Is there something different about the VET head that enables it (in stock form) to be able to rev to 10K?


thanks

[MadScientist]

Contact Mazworx... they use the VET Heads.

[Killa_D]

lol wow you really just needed to search but to make it plain and simple VET heads do not have floating rocker arms like the DET heads so with that said as long as you have the proper valve springs set up and cams reving to 10,000 rpms shouldn't be a problem.

[PoorMans180SX]

What Killa_D said. Way better rocker design in the VE head. That's really the only thing that limits the DE(T) head.

[sirfallsalot243]

So why isnt it more common to see guys running the VE head? What makes it not worth doing?

[jspaeth]

So why isnt it more common to see guys running the VE head? What makes it not worth doing?

Can get expensive, need to buy quite a few new parts, and some non-trivial modifications/fabrication.


Okay, I see now why (rocker arms are on a rod, so they can't fly off).


But it seems amazing to me that companies probably base their rev-limit off of R&D, and someone can just say "eh fuck it lets rev it out another 2000 RPM higher than that".


At the end of the day, you are still using the OEM pistons, crank, rods, etc.

How does anyone know if those parts can withstand the drastically higher rotational and linear velocities and accelerations?


This is one of my major unanswered questions honestly.....


I have asked posted on here quite a few times, and no one can ever give me a scientific answer (maybe there isn't a good one?)


How do you determine the safe REV limit of a motor?

At some point, the parts cannot stand the stresses or the speeds get too high and the metals get too hot....


I would assume that high-performance engine builders actually test this stuff, but it intrigues me that people just slap on springs and retainers and rev the motor another 1500 RPM over the OEM limit.

[Killa_D]

also the stock valve springs on the VE heads are dual from the factory its just something nissan thought will help a little lol..

[PoorMans180SX]

Rev limit is based on piston speed.

The general rule is if piston speed is exceeding an average of 5000fpm, then that's getting into sketchy territory.

This can be safely increased if you use forged rods/pistons, well-balanced crank etc.

I would not rev a stock bottom end SR out to 10,000rpm. You're begging for pistons to shatter at that speed. At 10,000rpm the pistons are moving at 5643fpm, which is extremely fast, and definitely only doable on a built engine. Reducing rpm to 9000 means the pistons are moving at 5078fpm, which is much more acceptable, but I would still only do it on a built engine.

The formula for piston speed is : Stroke (in inches) * 2 * RPM / 12.

Obviously valve float can become an issue, but that is solvable with higher-strength and lighter valve springs, retainers, and valves.

Then you run into powerband issues. Obviously stock SR20 or SR16VE cams are not going to make optimum power out to 10,000rpm.

[racepar1]

Toyota 4ag formula atlantic engines rev to 10,000 RPM...

If it wasn't for the shitty valvetrain on the SR20det's they could rev up there too.

[jspaeth]

Rev limit is based on piston speed.

The general rule is if piston speed is exceeding an average of 5000fpm, then that's getting into sketchy territory.

This can be safely increased if you use forged rods/pistons, well-balanced crank etc.

I would not rev a stock bottom end SR out to 10,000rpm. You're begging for pistons to shatter at that speed. At 10,000rpm the pistons are moving at 5643fpm, which is extremely fast, and definitely only doable on a built engine. Reducing rpm to 9000 means the pistons are moving at 5078fpm, which is much more acceptable, but I would still only do it on a built engine.

The formula for piston speed is : Stroke (in inches) * 2 * RPM / 12.

Obviously valve float can become an issue, but that is solvable with higher-strength and lighter valve springs, retainers, and valves.

Then you run into powerband issues. Obviously stock SR20 or SR26VE cams are not going to make optimum power out to 10,000rpm.

Thank you, this is along the lines of the type of discussion I was looking for.


Also, when I talk about "rev limit", I am referring to mechanical rev limit.....how much the motor can physically handle.

I DON'T intend to discuss or talk about whether or not the motor is efficient or producing good power yada yada yada, because clearly that depends upon VE, port design, cams, turbo, valve job, the list goes on.

[PoorMans180SX]

Sure thing.

To put that in perspective, an F1 engine has a stroke of about 39.7mm, and at 16,000rpm the pistons are only churning 4167fpm.

[jspaeth]

So would you say that valve float and piston speed are the two BIGGEST factors?

As an example, for the VET head, there is a rod that holds the rockers, so they are constantly rotating back and forth on this rod.

Does this component not place any real upper limit on the RPMs?

(IE piston speed will cause the motor to fail before heat/friction between rocker arm and rod on which it is rotating?)

Is there any scientific resource you can point me towards so that I can learn more about these types of issues?


I would assume also that at these types of RPMs, you need to have an insanely well balanced crank....

[PoorMans180SX]

So would you say that valve float and piston speed are the two BIGGEST factors?

As an example, for the VET head, there is a rod that holds the rockers, so they are constantly rotating back and forth on this rod.

Does this component not place any real upper limit on the RPMs?

(IE piston speed will cause the motor to fail before heat/friction between rocker arm and rod on which it is rotating?)

Is there any scientific resource you can point me towards so that I can learn more about these types of issues?


I would assume also that at these types of RPMs, you need to have an insanely well balanced crank....

Negative. There shouldn't be much friction between the cam and the rocker arms or the arms and their mounts because of engine oil preventing metal to metal contact. Valve springs are what generate the most heat in the head.

Piston speed is definitely the biggest limiting factor, followed by valve float.

Yes, make sure your crank is balanced extremely well and I personally would get an ATI crank damper.

[jspaeth]

Well at this point in my life, I won't be doing anything like this, but i would like to learn about it, so that in the future, I could do it if I wanted to.

[s13silvia123]

subscribing this thread i need to learn more about this cause in the near future i willing be swapping my head over to this cause if i cant push near or even close to my goals this will be my factor to get further in my goals

[PoorMans180SX]

Mazworx offers a full VE conversion kit:

Mazworx VVL/RWD Conversion Kit (http://www.mazworx.com/index.php?l=product_detail&p=3136)

But I would request no intake manifold and just get this:

Xcessive Manufacturing (http://www.xcessivemanufacturing.com/merchant.ihtml?pid=173&step=4)

DET exhaust manifold bolts up, but the VE ports are bigger so you might want to port it out a bit.

Apex'i metal headgasket works with minor modification.

Then you have to machine 5mm off the back of your crank pulley because of clearance with the VE front cover.

Get something to tune it...done.

[Walperstyle]

also the stock valve springs on the VE heads are dual from the factory its just something nissan thought will help a little lol..

crazy, I didnt know that!