Some of you know I have been focusing most of my free time on the 565 RGB Parallel Video Board Project. In fact I have parts coming in for 3 more boards, boards of a new design which I am very anxious to put into action with the currently running 2 PVB's...

The purpose of all this work was to head in the direction of an advanced personal computer, designed for data storage and rapid display. Also audio, but I've not gotten to the audio or even a controller board that controls all 6 PVB's yet...

But something has happened this past week which will require my attention for the next couple weeks.
A car has been put in my lap for real cheap. The same type car that had shifted me from digital electronics to auto mechanics more than 20 years ago. So I am back to the crossroads, although now am much more knowledgeable in present digital electronics.

The car is a 1986 Chevy Camaro. Formerly I replaced the engine and some other modifications that increased horsepower significantly, but it was a carbureted engine. This one is a fuel injected IROC Z-28 with Tuned Port Injection. The one I originally looked for but could not find.

It needs a new engine and has an 4-speed automatic transmission. This is the year when Chevy initially came out with multi-port fuel injection for the Camaro. Anyway, I will be busy bringing this car up to speed next couple weeks.

My desire is to eventually replace the original 4-speed transmission with a more up to date 6-speed manual...

After this is done, I will attempt to do something... Which is why I post here: I would like to attempt to make a very simple FPGA (maybe CPLD, but It will grown into a total engine controller) design which incorporates a cylinder fuel injector shut-off scheme after the engine reaches a certain RPM in last gear for a certain amount of time.

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

Nice car!

I find that sometimes changing gears is a great thing to do. I get sick and tired of a project and it stops being fun - then it's time to do something else for a bit. I then return to the original project with new ideas and determination.

After all, why are we doing this if not for fun?

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In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

My other distraction from 6502/electronics stuff is also cars but a little different from yours (Austin 7). It's definitely good to have multiple projects you can divide your time on. I am currently hand making the aluminium skin for my car which involves A LOT of hammering. Very sore on the arms and shoulders. After a weekend of doing that tonight I'll need a break so will go back to working out the keyboard input on my little 6502 project.

No scope for combining 6502 with vintage cars I am afraid. The only electronics in the entire car is the condensor in the distributor!

Simon

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My 6502 related blog: http://www.asciimation.co.nz/bb/category/6502-computer

The goal is to save fuel when little torque is required, right? I like the idea, and have daydreamed about such a project myself. (A lot of the daydreaming happens when I'm behind the wheel, with little else to occupy my thoughts. )

I never had any ambition to replace the original engine controller. Instead I figured the fuel injector shut-off is something that could be added downstream -- for example: a microcontroller which would selectively squelch some of the injector pulses. There could be an imaginative pattern of dropouts related to the firing order.

All that sophistication might be overkill. I could start simple, with no logic, just a manually operated toggle switch wired directly in series with some of the injector solenoids. But where's the fun in that?

-- Jeff

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Yes, to save fuel and recoupe some of the money that will being going into the beast.
It has cruise control so maybe I could use that as an enable signal in addition to a user switch to activate the injector shut-off controller. At low speeds and on level ground, a most basic circuit might work very well. At higher speeds, air resistance will become a factor so the circuit would have to measure the incoming pulse widths, maybe switch on an additional cylinder. And it will be interesting to see the least number of cylinders that can work reasonably, because the engine will in effect be mis-firing and we don't want it to be shaking the whole car. So picking the right combination of cylinders and order would be key. I'll have to do research but info should be out there as they already use this technology on some present day 8 cylinders.
But yes, a simple module at first in addition to the original vehicle controller (PCM) that will go in between the injectors and PCM...

Tomorrow I tow it, and me and a friend will remove the bad engine and replace the block (305). Luckily he has one sitting around. Also I have to replace the electric fuel pump. Maybe it will be running next week.

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

It'd be nice if the circuit were smart enough to be trusted with the decision of when to enable cylinder dropping. But it'll surely ruin your driving pleasure if the thing sometimes makes bad decisions. (Automatic transmissions can be very frustrating in this regard! ) Initially, at least, I think it'd be better to settle for a manual enable, and let the driver make the decision. But it's the driver's decision whether to engage the Cruise Control, so taking a cue from that is a cool solution.

Sounds like an "either-or" proposition to me: either the 6-speed tranny or the cylinder-skipping -- but not both. If you had the 6-speed...

• the fuel economy problem would be largely solved, leaving little potential for additional gain (in the engine, I mean. Tires, aerodynamics & other factors exist).
• the engine would end up running lower revs and delivering higher torque -- which is what you want. But I suspect it would make cylinder-skipping intolerable (due to vibration), as well as unnecessary. (It'll depend on the ratio chosen for 6th gear.)

Speaking of vibration, I'd always imagined that as the limiting factor, ruling out cylinder-skipping except in the most forgiving conditions -- ie, low torque output, and moderate revs, not too low. IOW, strictly for highway cruising. But the factory-designed systems have more scope than that, am I right? So here's the question: do the factory-designed systems include special measures to prevent vibration, stuff you'd be unable to include in your retro-fit?

-- Jeff

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

I just searched for 'cylinder deactivation' and apparently there is already a product available for a reasonable price between $295 and $395. I'm reading the owner's manual now.

Also, the wiki on variable displacement, i.e. cylinder deactivation.

I will still tackle my own 6502 controlled unit when the time comes.

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

Selective fuel injector de-activation is not sufficient to successfully implement a variable displacement system, since you are not decreasing pumping losses (because the valves are still opening), and you are creating a stream of oxygen through the system (because the valves are still opening) to confuse the mixture feedback and EGR systems, rendering both basically useless. The 305 is not suited for this purpose without extensive valve-train modifications.

I would just go with the six-speed, and design an on-board computer for other tasks, like climate control, security and convenience, entertainment, etc.

Mike

Some very good points Mike! Although I don't care about the EGR, for sure the Mass Air Flow would be going nuts from the irregular vacuum...
According to the wiki, they mention the company on my earlier post. It won't pass EPA standards. Also there was a problem with the power brakes, since that system uses engine vacuum and de-activating 4 out of 8 cylinders seriously affects vacuum negatively. Still, they are selling their system.

I'm not so confident in this approach to save fuel now. I don't want invest alot of time and resources in something that's destined to fail. Thanks for all the input.

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

Yes, Mike brings up some good points... as just clipping the injector drivers would still leave the remaining cylinders to be dragged along and performing all four cycles which includes compression (of just air in this case). Chances are it might end up being a moot point between having a fraction of the power vs wasting some of what's left to drag the non-functioning cylinders. IIRC, Cadillac did something like this years ago but also was able to disengage the valve train for disabled cylinders. Needless to say it really didn't work that well as it's been long forgotten.

In any case, getting better economy from an engine that was clearly not designed for it somewhat unrealistic. The best you can likely do would be to optimize airflow and balance with the usual techniques of porting, polishing, cc-ing the combustion chambers, tweaking the valve train and balance the airflow through the engine. All of this is not a cheap effort and likely not in line with what you're trying to do. The tuned port system was developed by Lotus Engineering for GM... pretty good system in it's day, but still tacked onto an ancient design.

My brother has had several Iroc-Z cars over the years... and still has one to this day. It's been completely rebuilt bumper to bumper and with a much higher output engine and a more robust gearbox (automatic). For the past several years it has sat on his lift... zero miles. While it is pretty quick in a straight line, handling is, well... it's a Camaro... enough said. What seems to bother him (brother) the most is the braking system. Seems the rear calipers are a source of trouble (non-handed units as well) and even when functioning, the braking system instills little to no confidence, in his view. I drove it once many years ago... and had to agree, braking was pretty marginal.

Still, it can be a pretty cool project car and you can certainly have some fun with... there's just limits, based on what you're starting with. Not trying to rain on your parade, just trying to level set expectations a bit... as I've been working on cars for 4 decades, doing performance mods (not just engine) and it can get pretty expensive pretty quick with a low return, especially with older design vehicles, best of luck!

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Regards, KM
https://github.com/floobydust

Thanks. I'm already starting above, performance wise, the 1986 Camaro I first owned. I realize the limits of these vehicles. I prefer acceleration vs. top speed to keep everything safe, i.e. there are no laws for acceleration, unless one burns rubber.

Some questions...
BTW, Nice to see some experienced fellow auto technicians here. I only have 20 years under my belt, so I am humbled.

1) I would like to eventually swap the original 305 to a 383, but I am hesitant as the oil burning I've read about is excessive after a few thousand miles on a brand new build. The angle the pistons come in, on a compression stroke, is scrubbing the cylinder sidewalls is excessive and creating more friction and wear on the lower portion of the cylinder walls supposedly and after a 'short' time wearing occurs on the block.

2) With a larger Chevy CID engine, 383 vs 305, can the original PCM keep up? Would it be as simple as upgrading injectors that have higher flow per pulse width?, i.e. 19lbs/hr to 24lbs/hr?

3) The cam would be a roller style when switched to the 350 block (383CID), not too aggressive. I had great success using a roller cam from a '91 ?Trans Am in my first Camaro. The idle speed was admirably low even with the Rochester Carb.
What spec's would you recommend for a roller cam just above stock with 3" exhaust, headers, TPI, and original IROC differential with rear drum brakes?

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

The key to achieving a proper balance between reasonable performance, driveability, and economy is to reach stoichiometry as quickly as possible and hold on to it as often as possible. The TPI firmware makes the most efficient use of the available hardware, IMO, so I personally would spend my efforts on keeping the hardware in tip-top shape.

If you are looking to modify the hardware (camshaft, displacement, intake, exhaust, etc.), the stock TPI look-up tables for ignition advance and injector pulse-width are based on the volumetric efficiency of the stock configuration, so any modifications could possibly throw the system out-of-whack. Performance, driveabilty, and/or economy could suffer from the imbalance.

Although it is tempting to experiment with different hardware/firmware configurations, the simple truth of the matter is that it can get very expensive and time-consuming very quickly. There are a lot of dynamically-changing variables, and using pure theory to solve these equations is too complex for a mere mortal ... you're going to have to get your hands dirty experimenting and matching these components in the real world, with trial-and-error.

There are literally dozens of different performance-proven packages out there on the inter-web, and these hardware/firmware combinations are pretty much guaranteed to work together (someone else has already done the dirty-work). Many of them have been tested and compared with one another by an impartial reviewer. So, the question becomes, "are you in it for the labor-intensive and expensive engineering work, or simply for the end result that suits you best?" Both paths can be rewarding, but it's a choice that only you can make.

Mike

Once again Mike has been quick to respond. I'm actually over in Hethel as I type this reply, attending a driving academy at the Lotus factory on Sunday with my daughter

I can't recall all of the changes my brother made with his setup, but I know he changed a lot of stuff and went to 400 CID and large exhaust plumbing. Once I get back I'll give him a call and get some details on what he ended up doing.

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Regards, KM
https://github.com/floobydust

Then, I would think, it would be advantageous to plug in a performance PROM and start from there on the currently stock system. Not going to do every modification at once here. I will stay with the current 305 engine to get a feel for it. Then tri-Y headers and 3" cat-back. Then larger flow injectors.
Looking at the schematics of this 2nd Gen Chevy fuel injection setup, they fire 2 banks of 4 injectors, i.e. injectors on each side of the engine are wired in parallel which is interesting. Has to be emitting alot of HC at low RPMs with the gas just boiling away on top of the valves.

BTW, this car had a torn diaphragm in the fuel regulator, so it was dumping almost a gallon of fuel into the cylinders during troubling shooting. Also cracked the starter. After replacing these parts I took a test drive and I liked it!

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

The topic of cylinder-skipping by inhibiting fuel injectors has been in the back of my mind, and despite the delay I'd now like to add a comment or two. I hope nobody minds if I roll the discussion back a bit :
Okay, I'd like to venture some observations. I agree that when the vehicle is under way there will be a sharp drop in intake manifold vacuum shortly after cylinder skipping is engaged. That's because the driver will naturally want the same amount of power as before, and will compensate for the lost cylinders by pressing harder on the accelerator. A new equilibrium is then reached, with RPM and torque the same as before but with the throttle open much wider -- hence the lower vacuum.

Problems? Maybe! But the one benefit -- the key to the improved fuel economy we seek -- is lower pumping losses. My understanding is that the pumping losses drop simply because the throttle is open wider. In that regard, at wide-open throttle a gas engine becomes more like a diesel... which has no throttle, virtually no vacuum, and therefore minimal pumping losses -- isn't that right? To be more explicit, during each intake stroke the pistons will have less vacuum dragging back against their downward motion. And less drag means better efficiency (economy). As for the question of vacuum-assisted power brakes losing effectiveness, that would be an issue only if the throttle remained open while the brakes were applied! With or without cylinder skipping, this just doesn't seem like a problem to me.

That said, I share Mike and EE's concern about the engine computer -- even though I can almost believe it would be successfully fooled. What we want is for the computer to "think" the driver opened the throttle simply in order to climb a hill or counteract a headwind. The throttle position and the MAF support this interpretation. But there's one major anomaly, namely that torque didn't increase commensurately with the wider throttle opening. Does the computer even monitor overall torque of the engine? (Misfire detection indirectly measures the torque of each individual cylinder.) I guess another anomaly is that the air exhausted from the inactive cylinders will be comparatively cold and rich in oxygen, causing the exhaust O2 sensor (and is there also an exhaust temperature sensor?) to deviate.

Venturing back into my own field of expertise (!), I want to congratulate the folks at Fuel Smart Global for some delightful electronic cleverness. I'm referring to one aspect of their retrofit-able cylinder-skip controller. I decided to download the installation manual, and while reading it I expected emphatic instructions demanding that you must be sure to connect wire pair #1 to injector #1, wire pair #2 to injector #2, and so on. But such instructions are absent! Apparently upon startup their device "listens" to the signals, figures out which injector each wire pair has gotten attached to, maps the apparent firing order, and configures itself to operate accordingly. This is a tidy and thoughtful design feature which makes installation easier -- not to mention avoiding some skull-splitting headaches due to errors. I like it!

Via the contact form on their web site, I have invited the Fuel Smart people to comment on our thread here on 6502.org. I hope they accept!

-- Jeff

ps :
Part of me is tempted to conclude that, in a retrofit context, cylinder-skipping by inhibiting fuel injectors can be successful in saving fuel, although probably at the expense of violating EPA standards (as EE mentioned). That's because the pre-existing computer doesn't accommodate the retrofitted system. OK, in the context of new vehicle design, manufacturers can alter the computer at will. Yet, out of all the manufacturers that've introduced cylinder skipping, AFAIK none of them chose the cheap & simple approach of merely inhibiting the injectors. You'd have to suspect there are some good reasons why they resorted to more elaborate and expensive approaches (such as valve-inhibit mechanisms). If so, what are those reasons ?

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html