Broken Balance Shaft Belt
Feb 18, 2018, 09:52 AM
#91
Can anyone chime in as to why a broken balance shaft belt would result in a loss of power though?? I see here arguments of whether it will damage the engine over time, but I don’t see why I would be at a loss of power. I didn’t want to beat on the car so I can’t say with 100% certainty it lost “power” but the car was not reacting properly to the amount of throttle input I was giving... It still moved quite well though at max boost, with very generous throttle, maybe 75%. Spool up was definitely affected. Would the ecu sense an issue with the balancing system and throw a code and reduce power? I’m still at a loss and wont have the car back until tomorrow most likely.
Feb 18, 2018, 11:24 AM
#92
I can't think of how it will cause a loss of power. It will be off balance because the front balance shaft will cause left and right vibration (front and back if you're sitting in car). But you have 1 less rotating mass to spin, so you should gain half of the claimed 15 whp...like a lightened flywheel! 
Can anyone chime in as to why a broken balance shaft belt would result in a loss of power though?? I see here arguments of whether it will damage the engine over time, but I don’t see why I would be at a loss of power. I didn’t want to beat on the car so I can’t say with 100% certainty it lost “power” but the car was not reacting properly to the amount of throttle input I was giving... It still moved quite well though at max boost, with very generous throttle, maybe 75%. Spool up was definitely affected. Would the ecu sense an issue with the balancing system and throw a code and reduce power? I’m still at a loss and wont have the car back until tomorrow most likely.
Feb 18, 2018, 11:50 AM
#94
It's possible that your knock sensor started picking up knock from the belt flapping around and retarded your timing. Or knock sensor picking up noises from mounts or downpipe caused by front BS.
Last edited by 2006EvoIXer; Feb 18, 2018 at 11:55 AM.
Feb 18, 2018, 12:12 PM
#96
I just reread your original post. It doesn't seem possible to jump a tooth from BS belt breaking. Unless a piece got in between the timing belt and tensioner pulley and when it rolled through the tensioner pulley, the crank sprocket jumped a tooth before timing belt tensioner adjusted. But how could that happen without pulling the timing belt completely off?
Last edited by 2006EvoIXer; Feb 18, 2018 at 12:39 PM.
Feb 18, 2018, 01:09 PM
#97
I have no clue. Timing was checked and everything was fine, the BS belt was just in pieces when we got off the covers. Only other damage was the oil pressure pulley had nicks on it, which I’m assuming happened when the belt snapped. I’m just at a loss here. I’m trying to self diagnose but the pieces aren’t adding up. Is there any other system in that vicinity that would throw a VVT system code, but not be the timing belt and not affect idle whatsoever?
Feb 18, 2018, 04:55 PM
#102
I just can't think of any way you can injure your oil pump. It's protected by the oil pump sprocket. Maybe check oil sprocket gear for groves? But cover broke, so cover took most of the punishment.
Last edited by 2006EvoIXer; Feb 18, 2018 at 05:20 PM.
Feb 19, 2018, 10:07 AM
#105
EvoM Guru
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I have a good amount of experience developing balance shaft systems for OEMs. I've literally reviewed hundreds of hours of run data on engines, talked about this same stuff with other engineers who design these systems for a living, seen results first hand. Removing balance shafts will cause no damage to an engine. They are only for NVH purposes.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
Or an odd fire V6. I used to hate riding in the old class 7 off road trucks that ran the old odd fire V6 nascar Busch series motors. ****ing blenders man...lol
Can anyone chime in as to why a broken balance shaft belt would result in a loss of power though?? I see here arguments of whether it will damage the engine over time, but I don’t see why I would be at a loss of power. I didn’t want to beat on the car so I can’t say with 100% certainty it lost “power” but the car was not reacting properly to the amount of throttle input I was giving... It still moved quite well though at max boost, with very generous throttle, maybe 75%. Spool up was definitely affected. Would the ecu sense an issue with the balancing system and throw a code and reduce power? I’m still at a loss and wont have the car back until tomorrow most likely.
Timing could have jumped. Knock sensor could have been picking up the noises of the belt flapping around as knock. The odd harmonics of having only one shaft spinning may been freaking out the knock sensor, and the ECU can pull a lot of timing, which will hurt power.
It's not oil pressure. The timing belt is either on the oil pump gear and spinning it, or it's not.
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2006EvoIXer (Feb 19, 2018)