Extreme MPG from 91' LS400 ??

[spf_lexus]

not to mention the motor would not last long due to the imbalance caused by the dropped cylinders...

Not saying that I dont believe you but can you elaborate on this some? I initially ruled this out as I assumed that the weights of the rotating assembly wont not be changed. Would it matter if I left the plugs installed so that pumping losses stay preserved? Also, a single coil being removed would be 2 cylinders from each bank so the overall drop in usable cylinders would be even from bank to bank.

 

[BlackUZZ31]

no need to trust me, give it a try, you will feel the imbalance at low revs and not hurt the motor but its at higher revs where you may or may not feel it as violently but it will be breaking the oil wedge in the main bearings and higher frequency vibrations will rattle main caps lose and other fasteners on the block, there is a reason why manufactures spend lots of money to spread the deactivation across all cylinders and specific programs in ecu's.

while the mass of the rotating components does not change the engines have a specific firing order for a reason... dynamic balance.

if your never going to rev it over 2500 it would probably be fine but what fun is that?

more reading here:

http://en.wikipedia.org/wiki/Engine_balance#Primary_and_secondary_balance

http://en.wikipedia.org/wiki/Firing_order

 

[spf_lexus]

That makes sense BlackUZZ31, thanks for the clarification. Im not really looking forward to the loss in tq/hp but instead want this for days when im planning 2+ hours of driving on the freeway where I dont use the v8's abilities anyway. If im not in a rush, I usually keep it at 60mph or so anyway. At that speed using cruise control, im sitting at 2,000rpm flat.

 

[BlackUZZ31]

That makes sense BlackUZZ31, thanks for the clarification. Im not really looking forward to the loss in tq/hp but instead want this for days when im planning 2+ hours of driving on the freeway where I dont use the v8's abilities anyway. If im not in a rush, I usually keep it at 60mph or so anyway. At that speed using cruise control, im sitting at 2,000rpm flat.

just put a aftermarket ecu in it or fudge the voltage from the o2 sensors so the ecu thinks it running a little richer and will lean it out at cruse a bit more...

 

[XR8tt]

just put a aftermarket ecu in it or fudge the voltage from the o2 sensors so the ecu thinks it running a little richer and will lean it out at cruse a bit more...

Aftermarket can just shorten inj pulse and be done properly..
Imo variable inlet length. Longer at low rpm high torque and shorter at higher rpm are better than dropping cylinders IMO..
Variable cam timing is another option ? But difficult ..

 

[ernie]

Cheap and cheerful way to better MPG just fit larger diameter tires.
For example change from a 60 profile to 65 or 70 with the same width and rim diameter.
Acceleration will suffer a bit and your speedometer will read low or need to be re-calibrated but all it will cost to try out is two tires, even second hands on rims just to swap on for a few days.
Just bear in mind that your trip info will still be the same as the car will not know that it has different size tires.

 

[adxx]

taking off even one cylinder spark plug brings up poor engine revving at low rpm. so, you're gonna kill your major powerband.
one of the solutions would be 6-speed man V160 from Toyota Supra JZA80

 

[spf_lexus]

taking off even one cylinder spark plug brings up poor engine revving at low rpm. so, you're gonna kill your major powerband.

If you read the pervious posts I do not care about power. I plan to unplug only for long commutes where I only see 55mph anyway. Easiest/cheapest way to save mpg is to drive slower... and the easiest way to do that is to leave earlier so you can drive casually.

 

[adxx]

If you read the pervious posts I do not care about power. I plan to unplug only for long commutes where I only see 55mph anyway. Easiest/cheapest way to save mpg is to drive slower... and the easiest way to do that is to leave earlier so you can drive casually.

Thinking about unplugging injectors is also a good idea, otherwise you'll get gasoline instead of oil in oil sump.

You should try how it works - I had faulty ignition wires on couple of cylinders when I replaced engine. it is somewhat drivable, but I prefer to have engine running smoothly.

 

[spf_lexus]

inking about unplugging injectors is also a good idea, otherwise you'll get gasoline instead of oil :biggrin: in oil sump.

Been covered in previous posts... injectors are already unplugged with the plugs. Already tried this and it works.

 

[Zuffen]

I'd be a little concerned about uneven cylinder temps which would then become head temps that could then become BHG's.

If I was trying to eek more miles out of a gallon of gas I'd look carefully at the cost/benefit equation.

If you spend $100.00 doing this you need to save a lot of gas to pay for it.

If you gained 10% fuel economy you would need to save around 25 gallons (at $4.00 a gallon) to cover the cost. 25 gallons will take you around 600 miles.

If you remove the spark plugs you would need some sort of filter to stop crap falling or being sucked into the cylinders.

One option I would try was to learn to drive with a very light foot. Most people (and cruise controls) use too much pedal to drive a car.

Simplest/cheapest option is higher profile tires.

 

[spf_lexus]

One option I would try was to learn to drive with a very light foot. Most people (and cruise controls) use too much pedal to drive a car.

Simplest/cheapest option is higher profile tires.

I think im on the the same page Zuffen.

I have been waiting for importation paperwork for a couple weeks now and the idle time is how I came to giving this a try. I will most likely just leave the car alone until my career starts and I can afford a replacement. I have a set of 19" rims with 245/35's all around that are about a half inch taller than OEM which should help out a bit but its a catch 22. The rims are 29lb each so the added mass will most likely kill the gains, resulting in an even trade. I suppose 24/25mpg isnt too bad for this car and I can achieve that when I use cruise control at 55mph which sits the engine at 1900rpm. With the plugs removed, and the spark plug cover installed, the holes are not an issue but after weighing all the pros and cons i think i'll just leave it alone.

If I get hired at Lexus or Tesla motors (which are the 2 at the top of my list), I will need a 100% reliable daily driver so I will have to leave this LS alone.

 

[stevechumo]

If I get hired at Lexus or Tesla motors (which are the 2 at the top of my list), I will need a 100% reliable daily driver so I will have to leave this LS alone.

After you get hired, then don't worry about tweaking on the MPG and have headache. LOL.

 

[spf_lexus]

After you get hired, then don't worry about tweaking on the MPG and have headache. LOL.

Yep . By then I can start shopping newer lexus's or whatever. I hate to go to the dark side but all day today I have been really eyeing a 2001 audi S8. They go for about $9,000 used these days. I will most likely keep it toyota but my eyes have been wandering

 

[stevechumo]

Yep . By then I can start shopping newer lexus's or whatever. I hate to go to the dark side but all day today I have been really eyeing a 2001 audi S8. They go for about $9,000 used these days. I will most likely keep it toyota but my eyes have been wandering

If your budget is around $10K, then a Lex GS300 with a low boost turbo kit will fit the bill.

 

[spf_lexus]

Power wise that would really fit the bill. What really made my eyes fixate was the quattro AWD and the 0.89g of grip from the factory. That AWD would be VERY useful to me as I drive to the ski resorts evewry season and traction is a selling point for me. Also that engine is bliss... Naturally aspirated 4.2L with 5 valve/head (40 total)... revvs to 7,000rpm... 360bhp and 317tq with (90% tq available at low rpm).

Here's a review on it I cam across today: http://www.caranddriver.com/reviews/car/01q2/audi_s8-road_test


Comparing the dark side to lexus, i would have to hand it to the GS400, as it beats down the S8 year for year. Adding a set of Lex's stage II cams and an exhaust would be plenty for me but now im getting waaaaaaay ahead of myself. havent even sent my resume out yet!


Im going in for nasal surgery on thursday and once im recovered and SEMA has come and gone, i'll be on the hunt.