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Bobcat Skidsteer Forums
General Bobcat Skidsteer Forum
The Mitsubishi 4G32 and you. A comprehensive guide to surviving poor financial decisions and overhauling a terrible engine.
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<blockquote data-quote="Scott Cee" data-source="post: 134064" data-attributes="member: 23817"><p>I thought about it a lot, but didn't really hash out my thoughts here. Their detuning of the vacuum advance likely is contributing to engine failure. They dropped the compression enough by using the turbo pistons that they reasonably could have run a lot more timing without any risk of detonation, and the lack of timing along with low compression was definitely leading to incomplete combustion. Incomplete combustion isn't great for valves, rings, the cylinder bores, etc. Changing the vacuum advance how I did will just lead to better combustion and running at part throttle and idle, effectively meaning that it makes more power with less throttle, but will limit full throttle power to about the same as before (it's a bit of a wash, throwing more base timing at it will definitely increase power a bit for sure though, and I did that). The correct factory solution to decrease power would have been a restrictor plate (Nascar does this) or a throttle stop, along with the complete lack of the secondary circuit in the carb.</p><p></p><p>I planned to just lock the secondary out on the carb if I used it. This would be the easiest approximation of what the factory did. I'd have to look at how the carb I bought is working exactly to tell what is best.</p><p></p><p>I suspect the pump would not outright fail from having a bit more power, but likely it would decrease its life. I did not check to see what else they used this pump in, it may be in higher power applications as it is. Their concern may not have been the pump, but rather something in the drive system, or this model was simply detuned a ton as it was intended to be their entry level/cheapskate model.</p></blockquote><p></p>
[QUOTE="Scott Cee, post: 134064, member: 23817"] I thought about it a lot, but didn't really hash out my thoughts here. Their detuning of the vacuum advance likely is contributing to engine failure. They dropped the compression enough by using the turbo pistons that they reasonably could have run a lot more timing without any risk of detonation, and the lack of timing along with low compression was definitely leading to incomplete combustion. Incomplete combustion isn't great for valves, rings, the cylinder bores, etc. Changing the vacuum advance how I did will just lead to better combustion and running at part throttle and idle, effectively meaning that it makes more power with less throttle, but will limit full throttle power to about the same as before (it's a bit of a wash, throwing more base timing at it will definitely increase power a bit for sure though, and I did that). The correct factory solution to decrease power would have been a restrictor plate (Nascar does this) or a throttle stop, along with the complete lack of the secondary circuit in the carb. I planned to just lock the secondary out on the carb if I used it. This would be the easiest approximation of what the factory did. I'd have to look at how the carb I bought is working exactly to tell what is best. I suspect the pump would not outright fail from having a bit more power, but likely it would decrease its life. I did not check to see what else they used this pump in, it may be in higher power applications as it is. Their concern may not have been the pump, but rather something in the drive system, or this model was simply detuned a ton as it was intended to be their entry level/cheapskate model. [/QUOTE]
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Bobcat Skidsteer Forums
General Bobcat Skidsteer Forum
The Mitsubishi 4G32 and you. A comprehensive guide to surviving poor financial decisions and overhauling a terrible engine.
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