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PostPosted: Fri Dec 27, 2019 6:51 pm 
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Would this make any difference?

Does any computer system support this approach?

--Walt Jackson


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PostPosted: Fri Dec 27, 2019 7:48 pm 
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Supercharged

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With MPFI and properly sized and calibrated injectors the fuel delivery would be consistent enough to not require a feedback from every cylinder.
There are modern engines that have more than one air fuel sensor. I believe that the MS3 systems support two sensors. That maybe more common on V engines with sensors allocated to each bank.

If there was a system that allowed for an airfuel sensor for each cylinder, to be useful it would also need the ability to trim and adjust each injector’s duty cycle independently. A simpler approach would be to have a matched set of injections and the combustion chamber characteristics all set to the same dimensions.


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PostPosted: Sat Dec 28, 2019 12:00 am 
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Supercharged
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I know the late 80s-early 2000s Ford MAF based MPFI system used two oxygen sensors- one for each bank of four cylinders. That said, Ford sold a MAF SEFI retrofit kit for the batch fired MAP based vehicles that only used one sensor but spliced both O2 sensor signal feeds to the computer to the one feed from the O2 sensor. I did it that way on my old Ford van. Computer thought there were two O2 sensors but really it was just one sensor sending the same signal to both inputs. Worked fine for almost ten years.


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PostPosted: Sat Dec 28, 2019 3:22 am 
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I thought really smart units could use one sensor (up to 4 cylinders or so) and figure out what each cylinder is doing knowing which cylinder that most recent puff of exhaust was for...……………

:mrgreen:

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PostPosted: Sat Dec 28, 2019 9:44 am 
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Supercharged
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Yes, there are EFI systems with individual injector trim (FAST XFI 2.0 is one) and, less commonly, ignition advance capabilities. How you get the data to make individual-cylinder fueling changes varies. Individual cylinder exhaust gas temperature (EGT) used to be the only way. Conventional lambda oxygen sensors are only accurate near stoichiometric and wide-band sensors are expensive.

Even if every cylinder receives the same fuel from a set of blueprinted injectors they don't usually have identical manifold runners and therefore don't aspirate the same amount of air which changes the air/fuel ratio. The differences are small, but present. More than once I've thought that if you wanted really precise air/fuel ratios you could get it by mixing a dry fuel like propane with the correct amount of air. It wouldn't matter if there were a little more or less air as the fuel is already in correct proportion.

Individual ignition trim is useful when some combustion chambers run hotter than others. Individual cylinder ignition retard is helpful when operating near detonation limits.

Years ago I was building a spreadsheet with different engine management systems to compare features, but it's hopelessly out of date.

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PostPosted: Sat Dec 28, 2019 12:20 pm 
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Joshie225 wrote:
More than once I've thought that if you wanted really precise air/fuel ratios you could get it by mixing a dry fuel like propane with the correct amount of air. It wouldn't matter if there were a little more or less air as the fuel is already in correct proportion.



I had that same thought 30 years ago. I have most of the parts on the shelf to do a slant turbocharged on propane. Just never got that "round tuit".

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PostPosted: Sat Dec 28, 2019 2:47 pm 
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Supercharged
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Charrlie_S wrote:
Joshie225 wrote:
More than once I've thought that if you wanted really precise air/fuel ratios you could get it by mixing a dry fuel like propane with the correct amount of air. It wouldn't matter if there were a little more or less air as the fuel is already in correct proportion.


I had that same thought 30 years ago. I have most of the parts on the shelf to do a slant turbocharged on propane. Just never got that "round tuit".


Do it! :D Propane is a great motor fuel. I encourage people to learn more about it.

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PostPosted: Sat Dec 28, 2019 3:05 pm 
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Supercharged

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Code:
there are EFI systems with individual injector trim (FAST XFI 2.0 is one)


Section 22 of the FAST operating manual provides instructions on what they call 'Individual Cylinder Control'

for the fuel side there is a table that allows operator input to add or subtract a percentage of fuel per cylinder for up to eight cylinders.
The values entered are in effect whenever the TPS reads a value above idle. The values are not live in that they are set and are not variable
and dependent upon an operating cylinder AFR or EGT.


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PostPosted: Sat Dec 28, 2019 3:24 pm 
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Quote:
Propane is a great motor fuel



One of the last large projects that I was involved with prior to retirement was assisting with the integration, product validation and production launch of a propane powered
school bus. The company that provided the propane engine is PSI. They have a proprietary propane injector that uses liquid propane to and through the injector.
Operates similar to a gasoline common rail FI system. Was nice to be working with an engine company that did design and manufacturing and assembly in the USA.
The propane motor that we developed and launched is a 8.8L (537 CI) V8,, the block and head assembly is shown briefly in the video linked. PSI also has I4 and V6 engines.

https://www.youtube.com/watch?v=G-gSot0-a8c


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PostPosted: Sat Dec 28, 2019 3:42 pm 
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Supercharged
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DadTruck wrote:
Code:
there are EFI systems with individual injector trim (FAST XFI 2.0 is one)


Section 22 of the FAST operating manual provides instructions on what they call 'Individual Cylinder Control'

for the fuel side there is a table that allows operator input to add or subtract a percentage of fuel per cylinder for up to eight cylinders.
The values entered are in effect whenever the TPS reads a value above idle. The values are not live in that they are set and are not variable
and dependent upon an operating cylinder AFR or EGT.


Right, no feedback/closed loop for individual cylinder fuel trim. The user has to collect and analyze the cylinder-by-cylinder data before tuning and re-tuning.

My understanding is that the old 2.2/2.5 Chrysler turbo engines had injectors offsets in the ECM programming as the intake manifold they made wasn't all that good. So if one pays attention to manifold design and uses a good set of injectors then the usefulness of this feature goes way down.

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PostPosted: Sat Dec 28, 2019 3:54 pm 
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DadTruck wrote:
Quote:
Propane is a great motor fuel



One of the last large projects that I was involved with prior to retirement was assisting with the integration, product validation and production launch of a propane powered
school bus. The company that provided the propane engine is PSI. They have a proprietary propane injector that uses liquid propane to and through the injector.
Operates similar to a gasoline common rail FI system. Was nice to be working with an engine company that did design and manufacturing and assembly in the USA.
The propane motor that we developed and launched is a 8.8L (537 CI) V8,, the block and head assembly is shown briefly in the video linked. PSI also has I4 and V6 engines.

https://www.youtube.com/watch?v=G-gSot0-a8c


Nice! The V8 looks a lot like a 8100 Chevy.

Growing up in Portland, Oregon propane fueled buses were everywhere. They made the fuel change after the OPEC shenanigans.

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PostPosted: Sat Dec 28, 2019 4:29 pm 
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Supercharged

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Quote:
a 8100 Chevy.


Good eye!,, Until GM discontinued it, PSI used GM 8.1 L blocks / heads with their own proprietary components.
PSI's new 8.8 was based on the 8.1 as they had experience with it and knew what worked and what needed improvement
with regards to using propane as the fuel.

Since diesel fuel now sells at a price above gasoline, there is once again a market for large gas engines to power medium duty commercial trucks.
PSI now has a gasoline version of the 8.8L, that development was done after I left the company.


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PostPosted: Mon Dec 30, 2019 10:23 am 
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TBI Slant 6

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DadTruck wrote:
With MPFI and properly sized and calibrated injectors the fuel delivery would be consistent enough to not require a feedback from every cylinder.
There are modern engines that have more than one air fuel sensor. I believe that the MS3 systems support two sensors. That maybe more common on V engines with sensors allocated to each bank.


On a slant six, even with MPFI, it wouldn't surprise me if the inner cylinders needed a little more fuel at high RPM and the outers needed a little more fuel at low RPM.

MS3 does allow up to eight oxygen sensors and allows closed loop feedback per-cylinder, so each cylinder can automatically correct and have the fuel tuned per-cylinder. I've worked with a couple customers using this feature, usually on all out race cars. A couple other ECUs can do per-cylinder O2s as well - I believe Haltech supports this, for example. There's a couple things to keep in mind if using this feature, regardless of ECU.

1. It's not going to work well with a stock log-style manifold; the runners are short enough that you'll get gases from adjacent cylinders washing back into them. So it needs a set of headers with reasonably long tubes.

2. For good results, you'll need to use wide band O2 sensors. I'm not aware of any ECU that put the control circuits for six of these onboard, so you'd need the control units as well as sensors. This could easily run a thousand or more for sensors and control units on top of the rest of the EFI system.

3. Turbo cars typically have too much pressure and temperature upstream of the turbo; this would be best for a naturally aspirated or supercharged engine.

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PostPosted: Mon Dec 30, 2019 11:50 am 
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Thanks for the thoughts, Matt, Josh, and all.

Lou

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PostPosted: Mon Dec 30, 2019 4:10 pm 
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Wow! What an informative discussion. Thank you.

"So it needs a set of headers with reasonably long tubes."

In your view would two Dutra Duals be sufficient?

--Walt Jackson


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