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How much boost on stock rods

A

apexjunki

New member
Looking for some info on how much boost I can run on stock rods and pistons with head shim on a 07 apex at 7,000 to 10,000 ft elev.
 
Depends on how much octane your willing to run. If you willing to run c16 I would run up to 20 psi on stock rods and pistons on occasion. 110 octane I wouldn't run more then 17-18. Detonation is what throws rods through blocks, not the lack of strength of the rods or pistons. It's actually the rod bolts letting loose most the time.
 
I have run over 20 #'s with 75/25 c12 without any issues, many factors to determine the answer to that. Like others say 18. Detonation is the killer, factors are: fuel settings, compression, octane/fuel quality, engine air temp, turbo/intercooler sizing/efficiency, timing, etc, etc.
 
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Everyone has stated very good points....Has there actually been any stock rod failures when using the correct octane for the boost threshold you are pushing??? The propane sleds that are out now have been running up to 25lbs of boost on stock rods and pistons.....Dissasembled, inspected and have shown nothing out of the ordinary with the internals of the engine.....So who can truely say what the limit of the stock parts are when you run the correct Octane!!!!

BC.
 
How many have actually seen an Apex throw a stock conrod while running proper fuel, HEAD SHIM, proper set up, etc, no NOS, no water meth ?
I've only heard of guys running stock compression and one RX using nitrous.

I'm going to keep pushing my motor, sure the RB3 timing control and super cold intake charge helps too. Maybe I'll be sorry. :eek: :beer;:beer;

AA
 
If you want some good advice call a good motor builder (that's seen and rebuilt grenaded motors) like Dustin @ Outlaw Motorsports. He wouldn't claim the stock rods were safe for anything over 15 lbs. Suprised me but he knows a heck of alot more about these motors than I do.
 
If you want some good advice call a good motor builder (that's seen and rebuilt grenaded motors) like Dustin @ Outlaw Motorsports. He wouldn't claim the stock rods were safe for anything over 15 lbs. Suprised me but he knows a heck of alot more about these motors than I do.

I'm not saying Dustin @ Outlaw Motorsports not know engines, but if anyone says that Yamaha stock rods not safe over 15 lbs he have to talk about an engine thats have no headchim and running regular fuel, or he must have sick kickback on selling aftermarket rods!
Let the evidence from people running much higher boost with stock Yamaha internals speak for itself!
The key is: Run on appropriate octane regarding boost and compression level, i follow the numbers that the boost calculator gives me, and had not a problem, 6000km / 3800miles so far!
 
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as has been said its all in the right fuel, thats why the propane sleds can run 25lbs. I ran my nytro last year 18-22 lbs with a 30 hp. shot of nos, on stock internals no problem. its not the rods that fail its the bolts after the bearings have been beaten out of the rods from Detonation.
 
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How many have actually seen an Apex throw a stock conrod while running proper fuel, HEAD SHIM, proper set up, etc, no NOS, no water meth ?
I've only heard of guys running stock compression and one RX using nitrous.

I'm going to keep pushing my motor, sure the RB3 timing control and super cold intake charge helps too. Maybe I'll be sorry. :eek: :beer;:beer;

AA
What is your intake charge temp compared to the competion?;) Do you have a guage?
 
Depends on how much octane your willing to run. If you willing to run c16 I would run up to 20 psi on stock rods and pistons on occasion. 110 octane I wouldn't run more then 17-18. Detonation is what throws rods through blocks, not the lack of strength of the rods or pistons. It's actually the rod bolts letting loose most the time.
It's not the rod bolts that get loose, it's the rod bearing that gets smashed, then the rod starts slapping, then it stretches the rod bolt, which loosens the nut, then failure... catastrophic failure.

I've caught the motor just as the motor started to tick, pulled it down to find this.
 
It'll happen when doing a pull and the tick or knock will sound off in the pull, very unmistakable, the Apex and Rx motors don't give as warning as the Vector motor, but the split second you hear it, get off the throttle, and you'll save the motor, try to finish your hill and it'll cost...lots.
 
What is your intake charge temp compared to the competion?;) Do you have a guage?


My airbox builds frost on it, say its cool ;)
Shoot an air/air with a Raytek after a big pull, bet its 200*F

Drive safe with all those shiny CR parts !!
 
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on first build on band new apex motor 30 km in. 17 lbs boost, strait vp c-111 fuel, stock rods & pistons with head shim- #3 rod let go from bottom end at 10500 rpm and fired itself right into the CR tunnel & cooler! Put band new motor in with carrilo rods & 10:1 GE pistons ran same fuel; didnt know any better; ran 20 lbs boost on pulls. 400km later heard a ticking sound while cruising at about 30kph, stopped shut it off. Pulled engine and the same #3 rod bearing had failed. Looked like it was getting no oil but I guess that is detination. Rebuilt again and run strait c-16 fuel 20 lbs boost with no problems. I'll never cheap out on fuel again!!
 
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