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Discussion Starter #1
Help me understand this concept of "tuning" or monitoring vacuum on a nitrous set up? I have heard guys on here talking about it, referring to losing vacuum because of detonation(?) Where is it being measured at? Intake manifold? Crankcase?
If i understand a motor at WOT should have little to no vacuum in the intake?
:confused:
 

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vacuum in the crankcase keeps oil out of the cylinders which is bad , vacuum in the intake is there for carb signal, min1.5-2 inchs for the proper signal to carb for it to operate right
 

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First round fodder...
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if you run a racepack the crankcase vacuum signal can tell you when or if a cylinder is rich, pinched or hole'ed
 

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Discussion Starter #6
if you run a racepack the crankcase vacuum signal can tell you when or if a cylinder is rich, pinched or hole'ed
Don't run a Racepak but my 7531 will also if i remember correctly. Do i run a MAP sensor off the crankcase then and hook that to my box that way? So what would it show say if it was way rich or on the edge of possible failure?
 

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I understand that. Right now if i put a gauge on the crankcase, with my vacuum pump, i am at about 14. So if it starts detonating will that pressure drop?
if it is bad enuff to make the rings flutter, and loose there seal .
 

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I understand that. Right now if i put a gauge on the crankcase, with my vacuum pump, i am at about 14. So if it starts detonating will that pressure drop?
At what point ?? Is this a dry sump set up too ?? One of the things you have to watch if you have a wet sump is to not have to much vac. It can hurt the motor if it pulls to much.. SJ
 

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So basically if it loses ring seal enough, either detonates or overly rich, the vacuum will start to dance up and down and I better get off the throttle!

On a normal pass it should maintain what ever the current vac. reading is.....sound right?
Fixed it for ya, now it sounds right!
 

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it will look like a quick signwave decending to a lower than normal vacuum reading, yes you should be able it pick up a map sensor and monitor this but the lowest made is -15 to my knowledge.......
 

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I'm interested in knowing this as well, because my NOS Launcher instruction sheet says that in race car setups with a vacuum pump, you can connect the integral MAP sensor to a crancase vacuum source and log the vacuum signal during a run and that vacuum signal spikes will indicate detonation. Is this true? Would that be so with mild detonation, or would it have to be very serious detonation?
 

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Hope i dont sound stupid here. If i run a vac pump on my motor, and it has a pressure relief valve set at say @ 14in,If a single cylinder was to detinate would i see that on a log? Does the relief valve somehow let the motor maintain 14in. If it does how bad would the detonation have to be to upset the valve.

Thanks
 

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Hope i dont sound stupid here. If i run a vac pump on my motor, and it has a pressure relief valve set at say @ 14in,If a single cylinder was to detinate would i see that on a log? Does the relief valve somehow let the motor maintain 14in. If it does how bad would the detonation have to be to upset the valve.

Thanks
That's what I'm wondering as well, as every vacuum pump setup I've seen uses a vacuum relief valve to regulate the vacuum in the crancase. However, I suppose it takes a few micro seconds for the valve to respond and regulate pressure if there is a spike (up or down) in vacuum and the MAP sensor can see this. What I'm wondering is, does this occur with even mild detonation, or does it have to be pretty serious detonation to rattle the rings enough to change crankcase vacuum? Obviously, if it happens with mild detonation then it would be useful to use a MAP sensor to log for it, but if it takes serious detonation, then it may already be too late when you see spikes in a log.:confused:
 

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Discussion Starter #16
I'm interested in knowing this as well, because my NOS Launcher instruction sheet says that in race car setups with a vacuum pump, you can connect the integral MAP sensor to a crancase vacuum source and log the vacuum signal during a run and that vacuum signal spikes will indicate detonation. Is this true? Would that be so with mild detonation, or would it have to be very serious detonation?
Exactly what i am looking for help with! Does any one have a log they could post up via racepak, 7531, nos controller??? Just to see.

Steve, the 14 inches of vacuum was at WOT, measured when we dynoed.
 

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You will see even the slighest hint of ring flutter, in a vacumn trace, especially with a RacePak, because the sample rate is very high. As someone else said, the motor should maintain, or make vacumn during a pass. If it is dropping, or has dips, the motor is NOT happy.

With all 3 kits spraying on our 632, it has 10" when he drops the button and 13" at the stripe.

Think about it, on a nitrous motor, with a gas ported piston, the more cylinder pressure you make, ie, more nitrous, the better the motor should seal. If this is not happeneing, there is a reason. As I mentioned in another thread, about what a plug "should" look like, you will see an unhappy motor MUCH quicker in the vacumn trace, as opposed to watching plugs. Rich, or overtimed, will unseat the rings and even the slighest flutter, will show up in the trace.

Monte
 

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Discussion Starter #18
You will see even the slighest hint of ring flutter, in a vacumn trace, especially with a RacePak, because the sample rate is very high. As someone else said, the motor should maintain, or make vacumn during a pass. If it is dropping, or has dips, the motor is NOT happy.

With all 3 kits spraying on our 632, it has 10" when he drops the button and 13" at the stripe.

Think about it, on a nitrous motor, with a gas ported piston, the more cylinder pressure you make, ie, more nitrous, the better the motor should seal. If this is not happeneing, there is a reason. As I mentioned in another thread, about what a plug "should" look like, you will see an unhappy motor MUCH quicker in the vacumn trace, as opposed to watching plugs. Rich, or overtimed, will unseat the rings and even the slighest flutter, will show up in the trace.

Monte
Awesome!!! Just what i was looking for. Thought i read something you posted before but wasn't sure. What about a overly lean condition?
 
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