Qurious as to what the stock RPM limitation is of the engine mechanically speaking (not ECU/rev limiter), also what would be necessary mods to bottom end & head to provide strength to 8k?

I always wonder how they determine this using Math & Physics calcs as opposed to expensive trial and error..

 

well if you were to build the motor, it should be safe to around 7500 RPM. that with a new P&P head, pistons, connecting rods.

Check out www.ZPIracing.net

They have some great stuff for tC's looking for more power.

 

Thanks, but I'm looking for a little more specifics.. to say "build the motor up" is kinda vague..

i've built motors for my 3tc in the past, and understand that bore/stoke, internal materials used, weight of internals, etc.. all play a part.

Let me as in a more specific way.. Suppose I was to "build the motor up", what method/research would I use to know what the new "safe" RPM limit is (dyno power aside)

I also want to use those same methods to try and figure out the max rpm of the stock engine.

Thanks

 

It's going to require a lot more than just simple math and physics. You'll need to know the shear strength of your alloys, the density and purity of the metal parts, and a general idea of force vectors on all parts, as well as temperature.

You're looking at a series of complex differential equations, computer modeling, and existing data that I doubt even some of the manufacturers have or will give to you. People don't engineeer their vehicles when modifying them this way because generally there's just too much of a lack of information, and the safe bet is to build something stronger than what you're throwing at it. That's why most everyone is going to tell you to buy strong parts and raise the rev limit. Those parts may be able to hit 9500rpm, but it's all a big test at that point to see what's too far.

 

Gotcha... Anyone tested the limit on a stock motor?

 

Look up the threads where people misshift and rev to 7-8k and have problems.

I would say the safe limit on the stock block is the 6250 redline that comes from the factory.

 

I would think you stock transmission would hold u up when reving so high as 8,000 RPM, with time it will not hold up at par with the engine. I think thats a problem we have to also address.

 

Wise advice, but keep in mind during a bad downshift the engine is accelerated almost instantaneously to this high revs, which means the crank could theoretically out-accelerate the head, and cause some pistons to slam into valves. I'm sure this is part of it, in addition to the huge stress load of moving that fast.

Usually a motor is engineered to handle, at a minimum, 15-20% more stress than indicated maximum before failure. Using a standalone, I'm sure the motor will run just fine at 6800-7000 rpm... but at that point, your power curve is most likely dropping off anyway because you're outflowing the FE head.

Rev's aren't everything... Hell, my uncle's race engine only revs to 7000... For a motor like the 2AZ, you're better off trying to maximize torque for daily fun. If you want to race it, stick to boost. You don't need huge revs if you dish out 400 ft-lbs at 5000 rpm.

 

Some good advice..

I myself have miss-shifted 4th-2nd once (from redline in 3rd) and suffered no damage. [note.. tires squealed and I immediately sank clutch so maybe I reacted fast enough to prevent damage, but RPM went WAY up]

It was after that that I kinda realized that we have a pretty well built motor and wondered how high an rpm the bottom end supported. AGAIN... head flow, power gains etc.. aside.

Anyone with real tested info?

 

The only way your crank can "out accelerate" the head is in the case that your valve springs cannot react quick enough. Not only will you not do that on the tC at 8k, the tC is a non interference engine (all but a couple of toyotas motors ever that I know of are non-interference), so this is not an issue. The cams can be in any position without the pistons hitting a valve.

To figure the safe limit. I would go no higher than about 10 - 15% of the stock RPM without building. If you are building, then you can do some math to calculate rotational load given the weight of the components, stroke and rpm. If you add lighter or shorter components (depending on how you build) then you can back - calculate given the new numbers to produce the same max forces. This, however, does not take into account the strength of the new materials. So it is hard to tell when you are buying off the shelf parts and building a motor.

 

Good to know.. I couldn't remember if it was an interference motor or not... I've never popped the head on a 2AZ... yet..

 

i have... but it had metal shavings all over it ...... oops......