ok our stroke is 3.68 inches(93.5)



which using the piston speed equation (stroke x rpm / 6) at 7200 would put the piston speed at 4416 ft/m



ive always recall that the max we can safely rev the beta to was 7200 stock, being that i now have shot peened rods, arp bolts and forged pistons looking to see if id be able to rev it higher than that



digging around some on the interweb i ran across this



Regarding piston speed, A.G. Bell provides these guidelines for piston speed in his book, Performance Tuning in Theory and Practice:



Stock Motor (cast crank, stock rods and cast pistons): 3,500 ft/min

Heavy Duty Motor (forged crank, shot-peened rods w/good bolts, forged pistons): 4,000 ft/min

Drag Racing Motor (forged crank, aluminum rods, lightweight pistons, etc.) = 5000 ft/min



which, if thats true, the stock motor revs higher than safely and i doubt hyundai would allow that to happen



BLAH so confusing



(for some wierd info, wiki says we have forged steel rods, i always thought they were cast, is it true?)



weird what you research when your bored and cant sleep

 

If you do that equation for the original 1.8L crank (85mm) it's 4020, just slightly above the "heavy duty" mark. Plus people do boost on stock pistons, rods and crank quite regularly so there's no doubt Hyundai did build hell out of this motor. I was also reading that 2.0L beta1 and all beta2 heads use a solid lifter which allows for greater rpm and valve response. Any idea if the 1.6s and 1.8s did too? It's quite possible this motor was intended for "heavy duty" applications.

 

Those numbers are for a specific engine with a specific combination of parts. The parts you use are different, therefore you will have higher or lower safe operating speeds. As the OEM specified a higher speed, I'm going to go way, way out on a limb here and say you will be OK with higher speeds than in that chart for Heavy Duty, but won't speculate about the Drag Racing speed.



My vote: see what others have been able to run reliably with your combination, if possible. If not, you get to be a guinea pig.

 

A.G. Bell's book was also written 20-30 years ago. Manufacturing processes and metallurgy has become MUCH better since those days, which raises the limit considerably. A.G. Bell's book was also written for reliability. Drag Race motors can get away with 5000 because they spend such short time @ those high figures and they get rebuilt very frequently. You can build a beta motor that will see 5000, but you've got to be willing to take the hit when it breaks and/or do regular rebuilds/checks to make sure it's ok.



Consider the Yammaha R6 motorcycle. Stroke of 42.5mm with a red line of 17500 RPM. Do the math on that one and you end up with 4842!!



before you go crazy trying to get 9000 RPM beta motor, keep in mind the stock head doesn't flow that well. You'll need cams, better valves and port/polish work to see any improvements over 6000-6500 rpm in N/A form.

 

Well I'm far from na now lol



I honestly think id be fine with 7500 rpm (4600 ft/m) with my setup



How about you post up the destroke plans tony I'm sure someone is willing to try it

 

7250 here no issues eva!

 

You want to rev? Retainers/springs. Make sure you're bottom end is balanced very well. Dyno, see where your torque line drops, then set rev limit before that or upgrade to bigger valves.



No sense in revving to 8000rpm if your power band drops at 7300rpm unless your rich so you can upgrade the bottle necks.

 

mario!! just the guy i was lookin to post in this



i just think reving slightly higher would help a tad concidering the size of the turbo im not askin to rev 8000 rpms, just slightly higher

 

If it's a stock head it makes no sense. Just watch your dyno sheet and I'll tell ya if you have more juice in a higher rpm range.

 

this interests me greatly. i love me a good NA motor, but it seems like you'd be pushing sh*t uphill trying to get a 2L beta to produce decent HP considering it only revs to 6500 rpm. i mean, that stroke is just ridiculous - it out strokes the 351 cleveland! i'm very interested in putting 1.8 pistons/rods/crank into my beta II for a more respectable set of dimensions.



as it is, i'd speak to your part manufacturers and see what the maximum safe speeds they have set, then just pick the lowest speed provided and work backwards. maybe look at engines with comparable dimensions? some of the B series LS motors have similar dimensions to the 1.8 beta, and i know that people do enjoy a good CR/VTEC build.