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Hmmm...I'm guessing that relates to a vacuum signal issue, right?
I Finally Did It.....EFI
- Thread starter threewood
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Thanks. I'll look for the SD card slot.
rmchrgr
Well-Known Member
It's on the left of the handheld housing. If you slide the outside frame down you will see it.
andyf
Well-Known Member
The problem with a PCV valve (or any vacuum leak with EFI) is that the Sniper self adjusts the air fuel ratio automatically. The Sniper senses the extra airflow and it adds fuel to keep the AFR where it is programmed to be. So if the PCV valve sticks open at idle the idle speed takes off and the car will take off.
One customer has a 700 hp race engine in his mud truck and when he was in the pits the PCV stuck open and the truck took off on him. He almost hit some people before he was able to flip the kill switch and shut it off.
If you have a big vacuum leak with a carb the carb doesn't add more fuel. You just end up with a super lean mixture and the engine runs poorly or shuts off. With EFI the computer adds fuel to maintain the correct AFR. It isn't smart enough to understand that the extra air is a mistake. It just adds fuel to the air to keep the AFR in the programmed range. So a big vacuum leak that shows up suddenly can cause a loss of control of the car with EFI. Just something you have to be careful with.
So like a gutted pcv valve with a small hole on the big end?
rmchrgr
Well-Known Member
That mud truck sounds like an extreme situation and probably not the right application for a PCV valve anyway.
In any event, I do agree on the Sniper adding fuel, I'm sure it's happening on some level in my car right now due to a small exhaust leak. If you have a situation like that in a late model OBD-2 car, it will go into a fault and if severe enough will put the car into limp mode. Obviously the Sniper can't do that with older cars so yeah, you need to pay attention.
I documented some PCV stuff in my own thread to which Andy replied. I'm considering getting the M/E Wagner adjustable PCV and running it it fixed-orifice mode. Expensive little part but have read some glowing reviews about it. In the interim, the old plastic one I was using was replaced with a brand new valve I had left over from my dealership days. One place I worked at we replaced them as a matter of maintenance but we didn't always do it if it was a pain and you'd just toss it in your bolt box. The new valve does seem to be working better than the plastic one as the oil leaks I was struggling with appear to have subsided for now.
In any event, I do agree on the Sniper adding fuel, I'm sure it's happening on some level in my car right now due to a small exhaust leak. If you have a situation like that in a late model OBD-2 car, it will go into a fault and if severe enough will put the car into limp mode. Obviously the Sniper can't do that with older cars so yeah, you need to pay attention.
I documented some PCV stuff in my own thread to which Andy replied. I'm considering getting the M/E Wagner adjustable PCV and running it it fixed-orifice mode. Expensive little part but have read some glowing reviews about it. In the interim, the old plastic one I was using was replaced with a brand new valve I had left over from my dealership days. One place I worked at we replaced them as a matter of maintenance but we didn't always do it if it was a pain and you'd just toss it in your bolt box. The new valve does seem to be working better than the plastic one as the oil leaks I was struggling with appear to have subsided for now.
I installed the Holley application and got a long data log. Not really sure specifically what I'm looking for but it is a play by play of my drive. Neato!!
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I might as well be looking inside a human brain for all the sense that makes to me!
MTBRider
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Please do post on how this goes. I’m super curious and am considering it for my 67
That_Tall_Dude
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That_Tall_Dude
Well-Known Member
There are 4 lines on the graph.
Red = RPM
Maroon = fuel delivery
Purple = afr
Green = Throttle Position
There are more options but I chose these to see if my afr was good at wot.
I can move the white line right or left and the chart shows data from these points.
Red = RPM
Maroon = fuel delivery
Purple = afr
Green = Throttle Position
There are more options but I chose these to see if my afr was good at wot.
I can move the white line right or left and the chart shows data from these points.
That_Tall_Dude
Well-Known Member
Cool man
So you floored it, rpm climbed (no shift), don’t know what do say about A/F (few jumps there are interesting), and fuel flow was off the chart!
Thanks for sharing; never saw one of these before...
So you floored it, rpm climbed (no shift), don’t know what do say about A/F (few jumps there are interesting), and fuel flow was off the chart!
Thanks for sharing; never saw one of these before...
Yep. Those green plateaus are wot (93% tps). Those afr spikes are weird. Only real issue on the drive was throttle pressure cable was too tight not allowing a shift unless I pulled off.
rmchrgr
Well-Known Member
If you want to get into the software, you might want to join the Holley EFI forums, lots of good info there.
As far as the visual representation of the data, you can isolate each parameter or however many you want to see. I have not messed with it too much yet but I believe you can change the "resolution" to make the data chunks bigger or smaller.
The data is basically about typical operating ranges so you're mostly looking for peaks and low points like your AFR spikes. Right now you're establishing a baseline tune (based on the initial Wizard set up) as it learns your driving habits. At some point down the road if you decide to make a change it's helpful to see a graphic representation of what the change actually did.
Or maybe something is going on that you can't see visually. It might be obvious but if you're trying to diagnose an issue then you'd want to run a log for however long it takes to reproduce the problem then go look at the data and compare it to your established baseline. It's almost exactly the same thing we used to do at the dealership trying to diagnose a car with a code that was intermittent. You'd take the scanner in the car and have someone with you trying to watch for voltage spikes or drops while trying to re-produce the symptom. "Customer states"...
As far as the visual representation of the data, you can isolate each parameter or however many you want to see. I have not messed with it too much yet but I believe you can change the "resolution" to make the data chunks bigger or smaller.
The data is basically about typical operating ranges so you're mostly looking for peaks and low points like your AFR spikes. Right now you're establishing a baseline tune (based on the initial Wizard set up) as it learns your driving habits. At some point down the road if you decide to make a change it's helpful to see a graphic representation of what the change actually did.
Or maybe something is going on that you can't see visually. It might be obvious but if you're trying to diagnose an issue then you'd want to run a log for however long it takes to reproduce the problem then go look at the data and compare it to your established baseline. It's almost exactly the same thing we used to do at the dealership trying to diagnose a car with a code that was intermittent. You'd take the scanner in the car and have someone with you trying to watch for voltage spikes or drops while trying to re-produce the symptom. "Customer states"...
On the second one, yes. Target afr is 12.5. The spikes are interesting.
The spikes are interesting as I would think the voltage of the O2 would be somewhat slow. It could be noise induced. The ADC should be oversampling to get the lowest noise and highest resolution.
On the other hand the ADC may be performing a successive approximation for a fast value and the spikes are just an artifact of this conversion.
I'd love to spend some time with a oscilloscope and see how the PWM shifts with AFR.
On the other hand the ADC may be performing a successive approximation for a fast value and the spikes are just an artifact of this conversion.
I'd love to spend some time with a oscilloscope and see how the PWM shifts with AFR.
andyf
Well-Known Member
Yes, a gutted PCV filled with epoxy and then drill a small hole. Something around 0.100 diameter should work. I've started making fixed orifice PCV valves but I haven't put them on my website yet. You can see it mounted on the passenger valve cover on this engine.
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