Redneck DoD

[L31MaxExpress]

There is another way to reduce throttling losses at part load. It requires a blower with a variable speed drive between it and the crankshaft. Set up with a high (numerically low ratio) as it would be in a normal forced induction set-up it boosts. Change the ratio and there is a ratio that permits full volumetric air delivery but without boosting. At that ratio the blower is invisible to the engine. Lower the ratio further and the effect is as if it were throttled - but instead of the turbulent irrecoverable throttling losses at the throttle plate there is vacuum applied beneath the blower and positive atmospheric pressure above which results in the blower delivering work to the crankshaft in part load running.

The variable speed drive in essence becomes the throttle (reacting to pedal inputs) but it would have to have a further control mechanism to compensate for the lack of intrinsic 'torque back-up' eg, constant pedal opening but vehicle slowing on a gradient.
I doubt that it will ever be implemented on a production vehicle but the theory is sound and the patent already issued.

95% of the throttling on many newer Nissan engines is the intake valves themselves. They have throttle plates, but only use them for more precise control for idle. The VVEL system controls both the intake cams duration and lift. Years ago there was a company IIRC called HotRocker in Denton, TX making a variable rocker ratio shaft mounted rocker system for a SBC that varied the rocker ratio from 1:1 to 1.9:1 during the engine operation and is strickingly similar to the Nissan VVEL system to the point it almost makes me wonder if Nissan bought the rights and Patent to the system. I saw the HotRocker setup in action in the early 2000s and it made a big race cam idle like a stocker and flattened the whole torque curve considerably.

I am thinking the best thing one could do for fuel economy on a stock L29 454 with high mileage is to replace the timing chain with one that can afvance the cam 4*. The 454 Vortec has a very late intake close point and thus it cost low-speed torque and efficiency.

 

[Pinger]

95% of the throttling on many newer Nissan engines is the intake valves themselves. They have throttle plates, but only use them for more precise control for idle. The VVEL system controls both the intake cams duration and lift. Years ago there was a company IIRC called HotRocker in Denton, TX making a variable rocker ratio shaft mounted rocker system for a SBC that varied the rocker ratio from 1:1 to 1.9:1 during the engine operation and is strickingly similar to the Nissan VVEL system to the point it almost makes me wonder if Nissan bought the rights and Patent to the system. I saw the HotRocker setup in action in the early 2000s and it made a big race cam idle like a stocker and flattened the whole torque curve considerably.

I found an EE video explaining the Nissan system (here >> https://www.motorauthority.com/news/1108141_how-nissans-vvel-engines-work) and it does seem complicated and presumably the HotRocker (only a description found, here >> https://ck5.com/forums/threads/hotrocker.1560/) is too if the two are similar.

I was looking at this type of thing a little while back and devised a simpler mechanism that could reduce the lift and duration down to zero. I didn't calculate the force required to operate it (could be unacceptably high) as I bailed as not convinced it wouldn't also suffer turbulence that ridding the throttle plate of its metering was supposed to achieve.

The reason is that the reduction of duration is from both sides of the maximum lift position and that is when the piston is at (roughly) mid-stroke, and with vacuum already in the cylinder the opening of the valve would initiate an inrush of air which would be turbulent. Had this opening occurred early in the stroke before vacuum formed, inward air flow would be orderly and when the valve closed (before mid-stroke, say) the ensuing vacuum returnable during the compression stroke. It isn't clear to me if the Nissan, HotRocker, or any other system achieve this or, they accept mid-stroke induction and the reduced duration (vs continual, full-stroke turbulence at the throttle plate) delivers benefit.
If they do, then I guess that is where the complexity is justified - but it's far from obvious they do.

 

[Boomer50]

95% of the throttling on many newer Nissan engines is the intake valves themselves. They have throttle plates, but only use them for more precise control for idle. The VVEL system controls both the intake cams duration and lift. Years ago there was a company IIRC called HotRocker in Denton, TX making a variable rocker ratio shaft mounted rocker system for a SBC that varied the rocker ratio from 1:1 to 1.9:1 during the engine operation and is strickingly similar to the Nissan VVEL system to the point it almost makes me wonder if Nissan bought the rights and Patent to the system. I saw the HotRocker setup in action in the early 2000s and it made a big race cam idle like a stocker and flattened the whole torque curve considerably.

I am thinking the best thing one could do for fuel economy on a stock L29 454 with high mileage is to replace the timing chain with one that can afvance the cam 4*. The 454 Vortec has a very late intake close point and thus it cost low-speed torque and efficiency.

 

[Schurkey]

I am thinking the best thing one could do for fuel economy on a stock L29 454 with high mileage is to replace the timing chain with one that can afvance the cam 4*. The 454 Vortec has a very late intake close point and thus it cost low-speed torque and efficiency.

In the Honda Goldwing world, the hot tip is to install an ignition reluctor from a Valkyre. The engines are very similar, the Valkyre has more carburetors and 4 degrees more ignition advance built-into the reluctor via a repositioned keyway.

I'm thinking that exactly the same thing could be done with the Vortec Crank sensor reluctor...clamp it on a milling machine table, turn the thing 176 degrees around, and machine a new keyway four degrees advanced.

Or do it right, and make a multi-keyway reluctor that would have the stock position, plus three more: 2, 4, and 6 degrees advanced.

Of course diddling with the software accomplishes the same thing, without the milling machine or the metal chips. Someday I'm gonna have to open the box my Jet tuning set-up came in.

There's no amount of software tuning that can advance the cam, though.

 

[L31MaxExpress]

In the Honda Goldwing world, the hot tip is to install an ignition reluctor from a Valkyre. The engines are very similar, the Valkyre has more carburetors and 4 degrees more ignition advance built-into the reluctor via a repositioned keyway.

I'm thinking that exactly the same thing could be done with the Vortec Crank sensor reluctor...clamp it on a milling machine table, turn the thing 176 degrees around, and machine a new keyway four degrees advanced.

Or do it right, and make a multi-keyway reluctor that would have the stock position, plus three more: 2, 4, and 6 degrees advanced.

Of course diddling with the software accomplishes the same thing, without the milling machine or the metal chips. Someday I'm gonna have to open the box my Jet tuning set-up came in.

There's no amount of software tuning that can advance the cam, though.

How about an offset crank keyway? IIRC though a 8* cam advance would be 4* ignition timing. The 4* unit would advance the ignition timing 2*. I always get thrown off though with cam vs crank advance and the way various manufactures list the degree changes.

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[454cid]

95% of the throttling on many newer Nissan engines is the intake valves themselves.

Interesting. I didn't know anyone besides BMW did that. https://en.wikipedia.org/wiki/Valvetronic

 

[mpyusko]

Hello mpyusko,

Great question. When it comes to pushing the MPG envelope with a specific vehicle, a thought
experiment like this can yield additional insight to the engineering tradeoffs built into our vehicles.
Well worth pondering in these times, even if it doesn't immediately yield a demonstrable MPG improvement.**

**** A Brief History of V8 > V4 engine conversions

Back in the '70s during the height of the Arab Oil Embargo, there were a small handful of people who were
experimenting with V8 to V4 conversions. From individual mechanics experimenting all the way to a complete
kit offered by Crower. From the outside looking in, back then a V4 conversion operating 100% of the time
just smelled like 100% of the weight penalty with 50% of the displacement, combined with the coarse feel
of a power stroke every 180° of crank rotation.

Sure, there might be an improvement in MPG, but in terms of the daily driving experience the operator was going to
pay dearly for every drop of fuel saved in the process. :-( (I know the above sounds a bit extreme, but back then
a lot of us were reeling by the tripling of gas prices in a year.)

Q: To put this into perspective, how would a rapid shift to $10-$12/gallon gas today affect your household budget?
So instead of pursuing a V4 conversion, I instead bought a newly released book on Rochester Carburetors and
started experimenting with lean-cruise implemented using brass logic in my '70s-era mechanical computer metering the
precious juice. (Book Full O' Carb Theory)

****

But I digress. Given the above, your idea about a 'part-time V4' under driver control for a GMT400 equipped with a
big block caught my attention. And thanks to the sheer amount of talent in here, the peer review process to date
has been a positive one, especially in the area of implementation details. Here's a prime example:



This gentleman's statement is spot on as shown by the '96 FSM wiring diagram for the 454 SFI setup:

You must be registered for see images attach

Studying this wiring diagram, looks like Schurkey's comment is the best way to implement your idea:



As engineered by GM, all 8 injectors 'float' at whatever voltage is at fuse ECM 1. Once
the CKP sensor starts sending pulses to the VCM (and we're above ~400 rpm) these
injectors are grounded in the firing order by the VCM, creating the necessary current flow
to open the injector and deliver the fuel shot to the cylinder.

Installing 2 NC (Normally Closed) switches in the dash, one opening the 1-4-6-7 injector path,
with the other opening the 8-3-5-2 injector path looks like a feasible implementation that
wouldn't outright injure any electronics involved? And if the driver uses the 'V4 via fuel cut'
function only during cruise conditions, will this give us both big block cake when working, and
also improved MPG during cruise conditions?

Possible Pros:

* Potential improvement in pumping losses during highway cruise? (ie: lower intake manifold
vacuum when 3.7L displacement V4 is maintaining same necessary cruise HP as 7.4L V8?)

Possible Cons:

#1) Guaranteed disruption of O2 sensor feedback from shut down cylinders distorting Closed Loop
operation as noted by several. Work-around: Force Open-Loop operation in V4 operation.
(Note that Open Loop operation routinely occurs both during warmup and also during WOT operation.)

Also, in discussions elsewhere it's been stated that when the stored tables in the VCM are closely
matched to the engine, the resulting Open Loop operation can be very close to optimal operation.
(Just no realtime tuning around parameters that are drifting from the default values.)
Work-around possible? Yes.

#2) Bringing excess RFI into cab from engine bay using normal unshielded wiring. Big potential
issue for drivers still using their AM radio. Not so much for FM listeners. Not an issue for
drivers using their smart phones as their tunes source. Potential impact on other in-cab circuits
unknown. With shielded wire, proper bypassing where the wire enters the cab, etc., if this RFI
issue surfaced it could be mitigated. Work-around possible? Yes.

#3) Weak/unmetered Air/Fuel mixture in intake manifold (from reversion pulses created by the events
surrounding the closing of intake valves) gets drawn into 'dead' cylinders. Too weak to ignite, these
unburned HCs exit the cylinder and heat up the cats?

We have all seen the training videos showing the feature of SFI, where the intake valve opens, and
a shot of fuel is neatly injected into the air being sucked past the open valve & into the cylinder.

But what a lot of people don't realize is that this is the behavior only when the properly sized injectors are
running at low HP/low duty cycle conditions. When the HP demand goes up, the injectors can and do
end up running at 80-90% duty cycle. In English, the injectors are on 80-90+% of the time...whether
the intake valve is open -or- closed. (!) So I don't think of the intake manifold in the 7.4 SFI setup
as being a perfectly 'dry' intake. Especially with the tuned-length runners and all the slinky-style
pressure pulses going on. (Not to mention any crankcase blowby introduced into all this by the
PCV valve.)

Work-around possible? Maybe. The right combo of short duration intake valve timing (decreased
reversion pulses) + increased size injectors (to lower amount of time open) + small turbo might
get the intake system to operate much 'drier' than stock?

Or, for the old 2-stroke guys in here, if we were able to somehow figure out how to implement
reed valves in the intake manifold runners upstream of the intake valves, then this reversion issue would
be cured.

Thinking on this, I remembered back to the old 100% V4 motors, and one solution with this intake
mixture control problem was neatly solved by using the stock '180° degree' dual plane intake manifold,
and only using the one side of the carburetor associated with the chosen firing order. For example,
if you had a Quadrajet, you would end up breathing only through 1 small primary + 1 secondary,
while the other side wouldn't meter at all, due to zero airflow past the venturis. (EDIT: Assuming old
school kit where valvetrain deactivation was implemented. An alternative approach would be to
leave the valvetrain intact and physically modify the carburetor to be unable to feed any fuel to the
intake manifold on the deactivated side.)

Check this out, here's a bird's-eye view of a V8 in our beloved firing order running as a V4:

You must be registered for see images attach

(Incredibly, this old Mother Earth News link is still working? Kansas mechanic home-brew V4 during oil crisis)

Note: I really like the OP's idea of balancing the wear by alternating which 4 cylinders are made to
carry the load. The 'only these cylinders always do the extra work' just felt wrong to yours truly.

So given the nearly intractable intake mixture control issues with the '96+ SFI setup, for the purposes
of this thought experiment what if we were to switch to a TBI 454 engine bay? Now we have the ability to run
only 1 injector feeding the side of the intake manifold matching the 4 enabled cylinders, and now the disabled
cylinders (via the dash-switch disabled TBI injector) really do only get dry air fed to them?

****

When I first started this reply, I was thinking that maybe planning on driving on well-tuned Open Loop tables during
V4 mode might actually allow the V4 operation that the OP was asking about. But due to the inability to control what the
disabled cylinders are ingesting, the '96+ SFI isn't an ideal candidate for this DoD experiment on a GMT400 machine.

But if you were to combine a TBI 454 with a savvy tuner using a EBL Flash-II setup, I think a good test case
could be put together. V8 454 running Closed Loop vs V4 227 running Open Loop on optimized tables?
This test case would also minimize all the other variables having to do with MPG measurements. (Wt, Cd, gearing,
state of tune, different driver habits, etc)

Sure, we're back to the 100% weight with 50% displacement drawback, but at the same time the driver can
choose to use the V4 mode only when the benefits outweigh the drawbacks. (Steady cruise) I'll bet that if you are running
a steady-state cruise down Kansas Rt. 36 I think you might be able to observe a noticeable difference.

And be able to do so without incurring a large 'Opportunity Cost' to find this out. Probably a negative ROI for 98%
of the people reading this...but for someone with the curiosity shown by the OP maybe the experiment pays for
itself while at the same time becoming a valuable source of new knowledge?

Thanks for the opportunity to think about the old V4 stuff I used to read about back in the day with great interest.
I remember thinking that the new DoD offerings based on the 'lost motion' lifter technology was interesting, but at
the same too many owners seem to have noisy/spendy failures in this area, so I never felt the urge to scratch that itch.

But this dead simple V4 cruise mode based on a tunable (TBI) EBL Flash-II setup may actually allow an old GMT400 to learn
new Redneck DoD tricks. :0)

Food for thought...

****

**Disclaimer: I lived through the early '70s Arab Oil Embargo. The year before this old midwestern boy started driving,
gas was ~33¢/gal...and when I got my license gas was a cool 99.9¢/gal. Including lots of discussion about how to modify
old gas pumps to display triple-digit gas prices? From my perspective, this meant that for every hour I pushed a Lawnboy at
the apt. complex after school I could now buy *2* whole gallons of gas...before taxes, of course. :0)

This may help to explain why I've always been interested in any possible method to maximize MPG, especially on unloaded
milk-run/ferrying portions of 'go retrieve a rust-free vehicle from down south' road trip.

Apologies... agreed, I would not want to ground out, but open the injector circuits instead. This was initially a thought exercise and I hadn't reviewed the wiring schematics.

Also, 7,000 miles is about 14 thanks of gas. I'm expecting there will be times where I'll be cruising on pretty much flat land (or downhills) for hours on end. Done right, that could save multiple tanks and extend my range.

I live in Western NY. It's not flat my any means, but there are a few places around here I can hit 17 MPG on flat (not downhill) highways. (No, I haven't fixed my #3 misfiring yet. Been crappy weather every chance I have had to work on it)

That being said...
So what you're basically saying, is it's possible, if I also disable the O2 sensors, possibly using the same switches. Doing so, would likely increase my exhaust emissions as the computer would have no way to check the mixture.

It also sounds like I would need to reprogram my computer. unless I missed something.

RFI.... who cares? People still use radios? LoL. (I have a cassette to Bluetooth adapter for my smartphone)

I get what others suggested the "usual stuff", but for someone technically savy, if I can modify it to make it work reliably, then why not?

I have android, so I use Torque app and a Bluetooth OBD-II adapter to constantly monitor and log all my sensors. Fun stuff.

No, my AC it not working. It's on my list to fix but finding lines for the rear is not easy.

 

[454cid]

That being said...
So what you're basically saying, is it's possible...

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if I also disable the O2 sensors, possibly using the same switches. Doing so, would likely increase my exhaust emissions as the computer would have no way to check the mixture

Which means it'll likely be running rich, which is going to use more fuel with the added benefit of possibly fouling plugs and the cats.

 

[mpyusko]

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Which means it'll likely be running rich, which is going to use more fuel with the added benefit of possibly fouling plugs and the cats.

Yeah... That's essentially what I said.
Valid point to consider.

 

[Supercharged111]

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Which means it'll likely be running rich, which is going to use more fuel with the added benefit of possibly fouling plugs and the cats.

Probably not. It should apply long term fuel trims that were already learned. You can unplug a single O2 sensor to disable the O2s. But I still say this is a dumb idea/complete waste of time.