Apex/RX1 Stroker Cranks and Rods

[TWIN TURBO]

Had a great day today. It was really nice to get a step by step tour thru the process of making a ultra high quality connecting rod in a state of the art facility. Just love this stuff.
One nice thing about ordering custom rods is you get to choose from a variety of options you don't get when buying off the shelf products and I love options, want them all and we got them. I chose a Semi-Parabolic I Beam Design that will reduce the chance of stress risers in the beam which can lead to cracks and ultimate failure. The broken Yamaha rods I've seen did just that, broke in the beam just above the big end housing bore.
The rods start with Mil Spec Aircraft Quality Double Re-Melt E4340AQ Chromoly Steel similar to 300M Specifications. It's a Full Machined Billet, not Forged, Triple Tempered, Surface Peened and through hardened, Cryogenically Treated, Magnaflux inspected and Rockwell Tested. We have selected lifetime "Custom Age 625" ARP bolts. These are very expensive but this is most likely where a problem would appear in high RPM applications. These bolts will eliminate the chance of failure. The rod also uses a AMPCO 45 Pin end Bushing, which is a very dense long wearing bronze bushing.
We have designed the rod for 600+HP at Boost levels of 40+lbs and 13500 RPM. All the load calculations were made, this rod can handle it. The best part of all is it's American Material, American Labor and American Pride and I can drive to the the facility in 45 minutes.
You really must see these, they are beautiful
I'm taking orders for stroker cranks and custom rods, now is the time for the coming season. There is a 3 week lead time so let's get started, Power is waiting.

 

[Wildman]

How large of stroke can we get from an RX-1 crank? 6mm, 8mm, Larger?
What is the general cost and I take it you modify our crank that we provide?
If you want to p.m. me the info or post it up so everyone can get an idea.

Thanks

 

[TWIN TURBO]

That is some what of a loaded question, "that is how far can we go" I've only heard of 10mm strokes, never seen one and don't think that's a good idea. I'm doing 4 and 6 mm but it really depends on how high you want to spin the engine. For RPM to 13000, 4mm is what I recommend. As I've said before RPM is your freind if your trying to make 500+HP and this is a whole new topic I won't discuss here. If you get the stroke too long the inertia loads go ballistic at high RPM and the rod angle, thus cylinder wall loading, gets more and more extreem. Because we are using a stock turbo piston, or a stock Yamaha piston for that matter, the rod length must shortened 1/2 the stroke increase to keep the piston in the hole. The rod angle will go from 1.91 stock to 1.74 with a 4mm stroke increase. The general range in almost all types of engines is from 2.0 to 1.5. Most 2 strokes are in and around 2.0 and a 454 Chevy is 1.53. Don't get me wrong I think the 1.74 ratio is good for a turbo engine as it increases dwell time at BDC which allows more time to fill the cylinder with incoming charge. A 6mm stroke will take the rod angle to 1.67 The compression ratio goes up with stroke also. A 4mm increase will raise compression ratio from 10:1 to 10.5:1 unless a thicker head gasket is used to offset the gain, which can be done but personally, I don't like that approach. While we are into this the rod to main overlap on the crankshaft, is reduced as stroke increases. that is not good for crankshaft strength.
All in all I believe and have tested this to extreems, the 4mm stroke is good and everything is happy there. We can do 6mm strokes but I am only stocking rods for the 4mm stroke. 6 weeks lead time on the shorter 6mm Rod. The cost on the package is $1995.00 crank modification and a set of my rods using your crank if it is in good condition and Magnafluxes good. I can repair some damaged cranks but the cost will increase depending on what's wrong.
Hope this answers your question, tend to get off in details sometimes.

 

[Wildman]

Thank you Greg, it gives me much to ponder in the coming weeks. I'm not much on spinning my motor at 13k but it has its applications. I appreciate the in depth explanation.

Thanks

 

[mulot30th]

Can also be good for NA power

 

[87gtNOS]

I would think that a stroker would not help so much in our applications as we run 'peak' RPM all the time, whereas in a motorcycle application (for example) you would run through an rpm 'range' and not just hold a given 'peak' rpm......stroker = torque.


Funny though, with that said, I would be HUGELY interested in a stock bore stroker to use N/A (well with the Yamcharger!!)!!!

Prices please. (edit:I see the price!)

 

[TWIN TURBO]

Very generally speaking, increase in stroke raises torque thru out the RPM range. It makes more power especially if you can hold the torque to a higher RPM. 4mm Stroke should give you 10% across the power band. reguardless where your clutched at.

 

[mulot30th]

Big bore AND stroker NA would be something