"Akio Ohtori - RIP Oppo" (akioohtori)
05/16/2018 at 09:59 • Filed to: Project Dumpster Fire
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"Akio Ohtori - RIP Oppo" (akioohtori)
05/16/2018 at 09:59 • Filed to: Project Dumpster Fire | 4
| 15 |
One of the more persistent problems on Project Dumpster Fire is my inability to measure the air-fuel ratio. Tailpipe sniffers are thin on the ground and even used units are fetching over $200 on eBay. I could build one, but the rabbit hole is deep there. I could also buy an in-car air-fuel meter with wideband O2 sensor, but that would require a lot of faffing around.
Luckily, I had a solution sitting on my dining room table! A while back I got an Amazon price alert (thanks CamelCamelCamel) which, sidenote, fill me with even more dread than Steam “An item from your wishlist is on sale” emails, for an oscilloscope that I’ve had my eye on for a while.
I am an electrical engineer and have a lot of professional toys but not a ‘scope. No longer!
Anyway, back to the Saab, I do not own a Bosch KDJL 7453 Pulse ratio thingy. In fact I haven’t even looked for one because I figured I wouldn’t find one. That said, I do (now) own an oscilloscope.
SCIENCE!
I ran the Saab up to temperature, hooked up the scope to the measurement port, and with a little fiddling with the triggering method had a mostly usable waveform.
I don’t remember what causes that weird spike when the waveform falls, or how to get rid of it, but ultimately it didn’t change the reading.
Looks like despite having leaned up the mix considerably, I was still reading at about a 10% pulse ratio, where the spec is 50%. As I dialed it leaner, the idle started hunting a little, but eventually I got the ratio to where the hunting was centered at 45%.
Good enough.
What is the net effect?
No idea. It is still covered in tools, trapped in the garage, and in need of a hot start relay.
But progress!
(NOTE: No actual science as used in this process. Just tools that would ordinarily be present in a lab.)
Bed hog doggo for your time.
RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:08 |
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Glad things are coming along! I do love me an old Saab! :)
Spoon II
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:15 |
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Science! Nice job! That reminds me, I still need to get a scope myself. Just got a nice little power supply off of Amazon, so this is next!
sony1492
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:20 |
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I think your waveforms upside down, and you can also look at injector health if you zoom in on one of those forms.(with a current probe)
The square dip is the pcm turning the injector on competing the circuit which is creating a magnetic field that pulls the pintle up. The jump to 60v is the magnetic field collapsing, which creates a bunch of voltage. This amount is capped and the energy stored in a diode to let the pintle down gradually, which explains the arc.
(Could be wrong since I learned this and barely used it over a year ago, used this site to brush up)
https://www.automotivetestsolutions.com/understanding-fuel-injector-waveforms.html
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Akio Ohtori - RIP Oppo
> Spoon II
05/16/2018 at 10:20 |
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It is a hard thing to pull the trigger on. Many choices, many different prices.
Low end new Tek?
Used Tek?
Used low end Tek?!
Chinese no-name-knockoff?
Respected off-brand?
Used respected off-brand?
2-channel or 4-channel?
Oh look a 6-channel!
Do I really need a color display?
Do I really need a USB port?
How high of a sampling rate do I really need ?
Ultimately I decided on the Rigol because it was well priced ($300), had decent sampling rate, and all of the other features I liked (USB and FFT). I would have preferred 4-channel, but at some point I had to just pull the trigger and buy one.
This was the first time I’ve used it and I’m happy so far. It does everything I am used to work’s Tek scopes to do, though it does feel a little lower rent.
TheTurbochargedSquirrel
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:22 |
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Nice choice of scope! My FSAE team has been using the same model Rigol for a few years now. I’m probably going to pick one up for myself at some point.
Sovande
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:29 |
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Why not just get and AFR gauge? Takes about 20 minutes to install (of you have a welder) and they are pretty idiot proof. Power, ground and the plug for the sensor. All for the very reasonable price of about $100.
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Akio Ohtori - RIP Oppo
> Sovande
05/16/2018 at 10:31 |
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I looked into it. I do own a welder, but I’ve never used it. Also the gauge that matches my existing ones is about $250, as are most of the others I’ve found.
This should be a “set it and forget it” measurement.
BvdV - The Dutch Engineer
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:33 |
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Nice use of scientific tools! Just like how I used Matlab to calculate the effect of a gearbox swap once.
I think a scope might be a very useful tool for diagnosing early electronically controlled cars, as all the systems are pretty basic, yet require a specialistic device. When I buy a Rover SD-1 (which I’ve been looking for for a while now), I’ll probably need a scope too, because Lucas electronics, haha
Schaef_Camaero Z/28
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:33 |
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What brand is your wrench roll & how’s the fit / finish?
I’ve been eyeballing some on Amazon lately but haven’t pulled the trigger on anything yet. I’m tired of having to dig through the pile of wrenches in my box to find the right size.
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Akio Ohtori - RIP Oppo
> sony1492
05/16/2018 at 10:36 |
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Oh awesome! Thanks! This is why Oppo rocks!
If only EssExTee could be so grossly incandescent
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:40 |
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Hook that up to my Jeep and it’ll probably have a meltdown
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Sovande
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:40 |
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Gotcha. I just checked and I spent $130ish on mine - for some reason I thought it was cheaper.
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Akio Ohtori - RIP Oppo
> Schaef_Camaero Z/28
05/16/2018 at 10:46 |
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It is a Tekton set, but apparently it is NLA. Well... Amazon is listing it for $140 and I paid $25... so I’ll call that NLA. It is pretty OK. My biggest complaint is they skimped on the large metric sizes (16mm and 22mm in particular) and the wrenches are kinda short. Also the downside of a roll is you have to have room to completely roll it out, which is pretty inconvenient as any flat surface in my garage is usually covered in other tools.
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Sovande
> Akio Ohtori - RIP Oppo
05/16/2018 at 10:47 |
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You should learn to weld! It’s fun!
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Schaef_Camaero Z/28
> Akio Ohtori - RIP Oppo
05/16/2018 at 11:13 |
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Good point on having the space to roll it out.. I was looking for a shorter one that would only hold SAE and another to hold only metric, but then I’m stuck buying two. My best bet would probably be making one myself so each pocket would exactly fit the wrenches I already have.... however, I’ve never sewn anything, which may pose a problem.