Whats a worst-case scenario that can occur with slipped timing?
#1
04-13-2010, 09:55 PM
Whats a worst-case scenario that can occur with slipped timing?
Just curious. What can happen? Truck impossible to start? Truck starts but runs rough? Truck will NOT go past 1800rpms? Sucks down fuel? Etc?
My throttle response is AWESOME but people are telling me my timing may have slipped. Trying to figure a worst case scenario that can occur with slipped timing.
Matt
My throttle response is AWESOME but people are telling me my timing may have slipped. Trying to figure a worst case scenario that can occur with slipped timing.
Matt
#3
04-14-2010, 09:01 AM
#5
04-14-2010, 01:00 PM
The only thing I can think of is high EGTs.(Yet another reason you need gauges)
I'm not very knowledgeable about the effects of timing on diesels and why, but just from an internal combustion engine standpoint, the later the timing event, the closer to the exhaust stroke peak cylinder temps occur. This pushes EGTs up and makes exhaust valves more prone to heat damage. Over a certain point the excessive EGTs won't melt the pistons because the chamber temps arent that high because the timing is so retarded. The temps in the exhaust will be through the roof, turbos will glow, etc., but the peak combustion temp point has moved from in the chamber through the valves to the exhaust ports in extreme cases. Good for turbo spool, bad for power.
As far as why the lower timing helps lower rpm power in a diesel, I'm still kinda in the dark. I'm guessing it's just because the timing is fixed, that all you can do is move the peak power point around and stock is too much timing down low, but perfect in midrange and too low up top. Lowering it makes peak power down low, but still nothing up top because its too low up there. I guess its why guys bump there timing to move the peak up there where their turbos spool, can really fuel it and make big HP numbers, but cyl pressures skyrocket because then the timing is really too far advanced on the low end. Just guessing.
---AutoMerged DoublePost---
Another thing too low(or high) timing could do is hammer the rod and main bearings. The combustion even is still trying to push the piston down when the crank is already at its lowest point and getting ready to come back up on the exhaust stroke(late). Too early and the piston is still coming up when combustion is trying to push it back down or at least the crank has not started back down and is straight up without any leverage to rotate.
I'm not very knowledgeable about the effects of timing on diesels and why, but just from an internal combustion engine standpoint, the later the timing event, the closer to the exhaust stroke peak cylinder temps occur. This pushes EGTs up and makes exhaust valves more prone to heat damage. Over a certain point the excessive EGTs won't melt the pistons because the chamber temps arent that high because the timing is so retarded. The temps in the exhaust will be through the roof, turbos will glow, etc., but the peak combustion temp point has moved from in the chamber through the valves to the exhaust ports in extreme cases. Good for turbo spool, bad for power.
As far as why the lower timing helps lower rpm power in a diesel, I'm still kinda in the dark. I'm guessing it's just because the timing is fixed, that all you can do is move the peak power point around and stock is too much timing down low, but perfect in midrange and too low up top. Lowering it makes peak power down low, but still nothing up top because its too low up there. I guess its why guys bump there timing to move the peak up there where their turbos spool, can really fuel it and make big HP numbers, but cyl pressures skyrocket because then the timing is really too far advanced on the low end. Just guessing.
---AutoMerged DoublePost---
Another thing too low(or high) timing could do is hammer the rod and main bearings. The combustion even is still trying to push the piston down when the crank is already at its lowest point and getting ready to come back up on the exhaust stroke(late). Too early and the piston is still coming up when combustion is trying to push it back down or at least the crank has not started back down and is straight up without any leverage to rotate.
Last edited by guhfluh; 04-14-2010 at 01:01 PM. Reason: Automerged Doublepost
#6
04-14-2010, 01:22 PM
The only thing I can think of is high EGTs.(Yet another reason you need gauges)
I'm not very knowledgeable about the effects of timing on diesels and why, but just from an internal combustion engine standpoint, the later the timing event, the closer to the exhaust stroke peak cylinder temps occur. This pushes EGTs up and makes exhaust valves more prone to heat damage. Over a certain point the excessive EGTs won't melt the pistons because the chamber temps arent that high because the timing is so retarded. The temps in the exhaust will be through the roof, turbos will glow, etc., but the peak combustion temp point has moved from in the chamber through the valves to the exhaust ports in extreme cases. Good for turbo spool, bad for power.
As far as why the lower timing helps lower rpm power in a diesel, I'm still kinda in the dark. I'm guessing it's just because the timing is fixed, that all you can do is move the peak power point around and stock is too much timing down low, but perfect in midrange and too low up top. Lowering it makes peak power down low, but still nothing up top because its too low up there. I guess its why guys bump there timing to move the peak up there where their turbos spool, can really fuel it and make big HP numbers, but cyl pressures skyrocket because then the timing is really too far advanced on the low end. Just guessing.
---AutoMerged DoublePost---
Another thing too low(or high) timing could do is hammer the rod and main bearings. The combustion even is still trying to push the piston down when the crank is already at its lowest point and getting ready to come back up on the exhaust stroke(late). Too early and the piston is still coming up when combustion is trying to push it back down or at least the crank has not started back down and is straight up without any leverage to rotate.
I'm not very knowledgeable about the effects of timing on diesels and why, but just from an internal combustion engine standpoint, the later the timing event, the closer to the exhaust stroke peak cylinder temps occur. This pushes EGTs up and makes exhaust valves more prone to heat damage. Over a certain point the excessive EGTs won't melt the pistons because the chamber temps arent that high because the timing is so retarded. The temps in the exhaust will be through the roof, turbos will glow, etc., but the peak combustion temp point has moved from in the chamber through the valves to the exhaust ports in extreme cases. Good for turbo spool, bad for power.
As far as why the lower timing helps lower rpm power in a diesel, I'm still kinda in the dark. I'm guessing it's just because the timing is fixed, that all you can do is move the peak power point around and stock is too much timing down low, but perfect in midrange and too low up top. Lowering it makes peak power down low, but still nothing up top because its too low up there. I guess its why guys bump there timing to move the peak up there where their turbos spool, can really fuel it and make big HP numbers, but cyl pressures skyrocket because then the timing is really too far advanced on the low end. Just guessing.
---AutoMerged DoublePost---
Another thing too low(or high) timing could do is hammer the rod and main bearings. The combustion even is still trying to push the piston down when the crank is already at its lowest point and getting ready to come back up on the exhaust stroke(late). Too early and the piston is still coming up when combustion is trying to push it back down or at least the crank has not started back down and is straight up without any leverage to rotate.
#7
04-14-2010, 02:14 PM
#8
04-14-2010, 02:24 PM
#9
04-14-2010, 02:32 PM
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