fastegg

Does anyone know if anyone makes/supplies underdrive pulleys for '99 LS400 ?

GH5T

Why would you want to put underdrive pulleys on the LS400?

YODAONE

The crankshaft serpentine belt pulley serves as the harmonic balancer, so goiing smaller is not really an option.

You could locate a larger alternator pulley but besides requiring a larger serpentine belt, will undermine the alternators' ability at lower RPM....in some instances the stock configuration does not keep up.(read my post on going to 130A alternator). You will be replacing your battery more often and perhaps the ignition coils are less efficient at idle....perhaps the AC compressor clutch does not respond well to lower power at idle...

On older American V6 and V8's an underdrive pully would turn the water pump slower...in certain circumstances this scheme worked.

With 1UZ-FE engine the water pump is driven by the timing belt, not serpentine belt..so no opportunity for power gains with an underdrivepulley here.

The power steering pump is also tuned to engine RPM and vehicle speed....you do not want to underdrive this either.

As an aside, a larger idler pulley would have helped bearing longevity and reduced noise...that would be my project

Hope I covered everything...

GH5T

Yodaone that was kind of my point. Under drive pulleys made sense on my 86' Mustang but I couldn't think of any advantages in adding them to the LS.

fastegg

Yodaone just answered all my question. I'm looking at fuel economy. As Ive said on another post. I took the clutch fan off my Cressida and got a 10% improvement straight away, from 500km per tank to 550 per tank... and all I did was take the fan off. Ive just taken the fan off my LS about a week ago. I think I'm getting better liters per 100km but unsure yet. I'm on holidays and wont be on the highway till next week so we'll see then. I havent fitted a thermo fan yet and so far no temperature issues... so long as the car is moving, even slowly its ok. No heavy stop start traffic where I live.

YODAONE

Ok...here's how the engine is going to adapt to temperature rise without a radiator fan

1.) The ECU is going to richen the fuel "charge" to help cool the engine....less fuel economy.

2.) The ECU is going to also retard timing to prevent detonation...see 1.) less fuel economy.

3.) The transmission cooler is in radiator so it will run hotter and reduce transmission life...

At least go with an electric fan.

fastegg

Yes yes I understand all your points Yodaone.... One thing that surprised me was when the car was idling in the driveway (with no engine fan) when it hit 90C the air con fan came on.. It couldn't pull the temp down but it didn't go up any further either. Since both the fuel and temp gauges read very incorrectly I put another temp gauge on, I put it in the drivers side door pocket as there wasn't really anywhere else to put it, its also reads the ATF temp also. I have been driving around now for 2 weeks with no engine fan and so far it hasn't gone over 90C and the air con fan hasn't come on either as I'd hear it. I will never the less put a 14" or 16" thermo fan on in due course.
.... And yes, just driving around town it's getting better economy... With engine fan on I get around 14-14.5 liters per 100km and with it off 13-13.5. Thats about 7-8% ? and it's much quieter.
... I'm out on the highway next week and I'm betting it will be using 10% less fuel.

fastegg

Sorry kitabel, the engine fan I was referring to is the stock clutch fan. I have been taking it on & off to discover if I get better fuel economy with it off. I'm 99% certain using the l/100km digital readout.

fastegg

Had the fan off for nearly 3 weeks now... I'd say 5-8% better fuel economy... So if I keep this car for another 20 years it's gunna be alot of money... Petrol here is $1.50 per litre... $120 per tank full... I use at least 1 tank per week.... So thats about a $10 a week saving.. $500 per year.. $5,000 in 10 years... $10,000 in 20 years and that doesn't take into account any increases in the price of fuel.