Help Make My 420a Even Slower!

[RallyEclipse98]

A 420a without FI is slow, we all know that. So rather than denying the slowness, I want to embrace it!

I spoke with this guy about a year ago who was selling his Eclipse. I asked about what mpg he saw with the car (to tell if he beat the heck out of it). He said about 50 mpg and here's how:

He told me he programmed the ECU to kill a cylinder at a given speed. He set the Eclipse to cut a cylinder at 55 mph. This being similar to what a lot of modern vehicles do from the factory. He said he could do it for my Eclipse or almost any car for that matter.

Is this safe and can it be done without expensive tuning software? I would call him myself but I find it foolish to take advice from a sales person.

Thank you for helping me make my car even slower!

 

[2gSpyder4g64]

in my eyes its pointless to have death weight on the crankshaft, if you want to save gas at 55 mph use the cruise control if you have the "heavy" foot disease, if you want to make your car 3 cilinder for free, just pull one of the spark plug wires

 

[tkelly27]

You could use an arduino or other microcontroller to drop different cylinders every couple of cycles. You would just need to cut the route to ground for the injectors from the ECU with the arduino.

Cruise control is not a good way to get MPG. Check out eccomodder forums for more info on MPG. Tuners is really for performance. Bang for the buck, changing the way you drive, weight loss, good tune, and aero mods are a good place to start. Pick the low hanging fruit.

Pulling a spark plug would use MORE gas, not less. You'd need more throttle to get the same output, but be using the same amount of gas, just 25% of it would be pumped out the tail pipe.

 

[jayson427]

If you want 50gpm go buy a prius! and this does not sound good at all I think it would make the rotating assembly off balance. You have two pistons on a compression stroke and the other two going downward ( 1 and 3 and 2 and 4 work together). So taking one piston out of the equation doesn't sound right at all.

 

[RallyEclipse98]

how to change your V8 to a 4-cylinder - Gas Savers - Fuel Efficiency Forum

DIY displacement on demand system project - Gas Savers - Fuel Efficiency Forum

These are very interesting threads about the idea of active cylinder management.

 

[jayson427]

how to change your V8 to a 4-cylinder - Gas Savers - Fuel Efficiency Forum

DIY displacement on demand system project - Gas Savers - Fuel Efficiency Forum

These are very interesting threads about the idea of active cylinder management.

Yeah they do it on v8's because they actually balance it out and run 4 cylinders. They don't do 5 cylinders or 3 it's on an even scale. Maybe you could run two cylinders but there's no point I still think it would kill the longevity of the motor and mpg. Get a prius!

 

[RallyEclipse98]

Yeah they do it on v8's because they actually balance it out and run 4 cylinders. They don't do 5 cylinders or 3 it's on an even scale. Maybe you could run two cylinders but there's no point I still think it would kill the longevity of the motor and mpg. Get a prius!

It definitely makes an interesting discussion even though the more I read about it, the less feasible it seems. A prius... no thanks. When driven right, my DSM gets near what a Prius does all without the slab-sided "styling" of a Prius. Maybe in the distant future a Tesla Model S though.

 

[jayson427]

Yeah if you have over half a million dollars to spend on a telsa.

 

[VelocitàPaola]

Real variable displacement systems have a way of deactivating the valves. Cutting fuel to a cylinder won't improve efficiency; there will be significant losses just pumping air through the engine. As tkelly27 noted, pulling a spark plug alone won't work either.

He said he could do it for my Eclipse or almost any car for that matter.

Is this safe and can it be done without expensive tuning software?

Implementing variable displacement would require extensive mechanical changes to the cylinder head and the addition of an aftermarket engine management system that supports this feature. It's definitely not as simple as "[re]programming" the stock PCM.

 

[bullettdsm]

Bang for the buck, changing the way you drive, weight loss, good tune, and aero mods are a good place to start. Pick the low hanging fruit.

Start here ^^ and then think about rolling resistances (tire contact patch, alignments, wheel bearings etc.). Do the simple stuff before you start thinking about water injection systems and super atomization systems etc.

You can certainly use MS to gain some mileage as well. You can definitely run leaner than stock (more so if you have forged pistons that can take a little more abuse). You can also make timing changes that match your driving habits and octane rating of the gas you use.

This is all rudimentary and generic. To explain all takes a book (and they write books on these things, ). If you hop on the internutz you can find quite a few different ideas. Use these ideas to help you think about ways to save gas. You shouldn't necessarilly try to "glove" each idea (What I mean is don't try to simply do the exact same thing as John Doe did to get 150 mpg. See what he did and then think about implementation onto your vehicle).

Also, know how much performance you are willing to give up to get better gas mileage. I was able to get 40 mpg (425 miles highway and 75 city) with the daily, while she could run either low 14's or high 13's at the track (I don't remember which. Been too long ago ). That was using an AFX ECU and a SAFC.

 

[RallyEclipse98]

I am already pretty skilled at hypermiling. I took a road trip (about 500 miles) with my old Oldsmobile (RIP) with the 3800 Series II V6 and averaged 49.4 mpg. The EPA rate for highway travel is 27 highway. The trip was about 95% interstate. Had to pass through a few cities such as KC that kept me from reaching 50 mpg.

Back to the 420a... I don't drive the car too much since cycling is my preferred method of city travel. That means it would take something like a decade or more to pay off the electronics/mechanics necessary to make this adventure work. Not exactly worth it especially considering it may take a hit at my reliability. My 420a currently has 167k and I plan to take it to the moon and back.

 

[91-GS]

Real variable displacement systems have a way of deactivating the valves. Cutting fuel to a cylinder won't improve efficiency; there will be significant losses just pumping air through the engine. As tkelly27 noted, pulling a spark plug alone won't work either.


Implementing variable displacement would require extensive mechanical changes to the cylinder head and the addition of an aftermarket engine management system that supports this feature. It's definitely not as simple as "[re]programming" the stock PCM.

(Theoretically) Will it be possible with a modified MIVEC head? From what i understand MIVEC allows valves to open at different times and for longer. Is it possible to have valves stay pen all the time? This plus fuel cut to those cylinders should reduce fuel consumption because now it's a two-cylinder engine with some dead weight on the crank.

 

[dsmcurse]

(Theoretically) Will it be possible with a modified MIVEC head? From what i understand MIVEC allows valves to open at different times and for longer. Is it possible to have valves stay pen all the time? This plus fuel cut to those cylinders should reduce fuel consumption because now it's a two-cylinder engine with some dead weight on the crank.

You understand that wrong. How is the camshaft gonna hold a valve open the whole time?

 

[jayson427]

(Theoretically) Will it be possible with a modified MIVEC head? From what i understand MIVEC allows valves to open at different times and for longer. Is it possible to have valves stay pen all the time? This plus fuel cut to those cylinders should reduce fuel consumption because now it's a two-cylinder engine with some dead weight on the crank.

Do you know how mivec even works? Holding valves open longer and completely open or closed is waaay different. Plus you would never be able to bolt it up on a n/t car.

 

[VelocitàPaola]

(Theoretically) Will it be possible with a modified MIVEC head? From what i understand MIVEC allows valves to open at different times and for longer. Is it possible to have valves stay pen all the time? This plus fuel cut to those cylinders should reduce fuel consumption because now it's a two-cylinder engine with some dead weight on the crank.

That's a good thought, but unfortunately there are a couple of problems with it. Like dsmcurse and jayson427 alluded, MIVEC is a variable valve timing system. Basically, MIVEC systems adjust the valve timing (and valve lift in newer systems) on the fly, but not independently. When the system is activated, all the valves are affected, but none of them are ever completely closed or open during the combustion cycle--which is necessary for variable displacement.

Furthermore, MIVEC was developed by Mitsubishi for Mitsubishi engines. That means MIVEC heads definitely aren't compatible with the Chrylser 420A blocks that are in my car and the OP's car. I don't know enough about swapping heads in the 4Gxx family, but I have a feeling MIVEC heads aren't directly compatible with 4G63/4G37 blocks (I assume you have a 4G63 engine since the car in your profile is a 1991 N/T).

Interestingly, Mitsubishi did have a variable displacement system called "MIVEC-MD." It was introduced in 1982, then made a few sporadic appearances before being dropped altogether in 1996.