jaundice

I previously spun an f22 to 9000 with the blower and broke a connecting rod. Don't want to trash this motor so want a good place to start for the tuner.

Jin_SK

When I was on my F24 I only rev'd it to 7500, after that torque was falling off so there wasn't much point. If this is a racecar then a lower limit is essential.

Gernby

@Jaundice - It's the inertia of the rod itself that causes them to break at high RPMs, not the boost or power being produced. You would have broken that rod even if you didn't have an SC.

@Jin_SK - I don't know of any normally aspirated street car that doesn't have torque "falling off" above 7K, but that's no reason to limit the revs! I know it's not intuitive, but it's HP that matters for shift points. If you are still making good HP, then you will definitely make more torque to the ground than you would in the next higher gear. That's a mathematical certainty.

Gernby

I've had to edit the post above several times to make it "technically correct", and still haven't nailed it. It really is hard to explain, but I once spent many hours trying to prove mathematically that torque was more important than HP for shift points, and wound up proving myself wrong. What I found was that if you had a perfect "continuously variable transmission", it would perform better if the controller for that transmission allowed the engine to stay at peak HP instead of peak TQ.

EDIT AGAIN!: However, I also found that non-CVT setups would perform best with shift points at or above the rev limit (except in the high gears).

jaundice

That makes complete sense. If peak HP is at 7500, then revving to 8500 keeps you closer to 7500 when you up shift. The goal is to keep the motor close to peak HP at each shift point.

s2000Junky

That surprises me, but anything can happen. I put 80k of hard miles on a f22 revving it to 9k regularly. I ran my old comptech kit at full boost with that motor till I ran it lean and had to retire it. The stock rods are tough. Typically what happens at over rev over a long period of time (yet to be determined) is the side loading on the piston to wall and ovalizing the cylinders over time. Short rods at severe angles puts more load on them at speed. In our case its the parts surrounding the rods then get worn, rather then the rod breaking itself, but obviously you have a different experience.

wadzii

If you have upgraded rod bolts you can turn it to whatever you want. Most of the k24's we build make power to 9000, a few make power to 9800 rpms. we have only had one failure and that was due to the cheap Chinese rods we had in our race car, they lasted 2 years of serious abuse at 9800, only made it one pass at 10200.

Honda pistons and rods are so light that side loading is not an issue.

Ultra_Nexus

Quite interesting this, but you seem to be missing the point of torque. Engine torque simply shows the efficiency of the per cycle combustion process.

What you are aiming for is to change gear at such a point when the torque at the hubs in, lets say 3rd, drops to a lower number than the product of the engine power and 4th gear.

Well, I say lower, I mean exactly that same in an ideal world!

It's often the case that you need to rev the engine to max in every gear, but less so as you go up the box since the ratios are closer.

rednikos

I have 8600 rpm redline.



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redboost10

10k shifts