Okay.............help!

[wwest]

Please, only traditional naysayers need respond.

I am on the verge, cusp, of commiting to buying an RX400h.

My idea is to have custom ground intake cams made and installed to convert the engine to the atkinson cycle. I don't need V8 performance and as I see it the loss of about 20% would put me back into an RX330 equivalent insofar as HP/torque is concerned but also with an equivalent 20% GAIN in fuel economy.

For the rest of you, sorry, but my wife says I don't need encouragement in this possible venture. Also, I am finding that all the dealers I have visited, WA & OR, seem to have surplus RX400h inventory.

[goofygrin]

I don't think it would be worth it monetarily or for cool reasons to do this...

You'd kill your warranty (and your resale value) and I seriously doubt you'd get a 20% gain in fuel economy...

I think you'd get more bang for the $$ by coming up with a custom flash for the ECU that will make the gas engine come into play later.

[SW03ES]

I totally agree, its way too expensive a vehicle to commit to completely voiding the warranty on.

[wwest]

Voiding the warranty.....

Never had a warranty claim on a Lexus yet!

Not so sure I'd let them touch it even if I had one, claim that is.

[SW03ES]

But you'd be voiding the Hybrid system warranty and you also have no idea what kind of effects your modifications would have on the longevity of the motors or the batteries. A set of batteries for the Prius costs $7000 I shudder to think what it costs for the RX400h. I know of Priuses that have had them replaced too.

I really wouldnt.

[wwest]

Why would modifying the intake cycle of the ICE adversely affect the electric motors or the battery?

Remember that you "modify" the intake cycle each and every time you move the gas pedal.

Not concerned about the warranty, losing that is a virtual given.

[SW03ES]

I have no idea, but thats the very reason that I wouldn't do it.

I just wouldn't make engine modifications to a $50,000 vehicle that would void the warranty on its 5 digit price tag drive system that is new and untested in the first place that are better made to something like a Chevy Bel Air.

If you've got $50,000 to spend on a vehicle just to "tinker" with and you're not conserned about potentially making it undrivable or running up tens of thousands of dollars in repair bills just to get maybe 20% better fuel economy I gotta get to know you better.

[wwest]

Well, the $50,000 wouldn't be just to tinker, I get to drive a really nice luxury SUV at the same time, a hybrid SUV yet. But at this point it looks as if the real problem might be how to keep the catalytic converter "lit-off" with the low exhaust heat/energy of an atkinson cycle.

Maybe the reason Toyota didn't use the atkinson cycle on the Rx400h and maybe also the reason the ICE on the RX400h runs more often than "we" expect.

[RX400h]

You wouldn't believe what new Corvette owners do or have done to their cars - superchargers, heads/cam/nitrous, etc, etc, shortly after driving it home. I've been a bit more conservative - intake system, exhaust, and shifter, but none of these affects my warranty.

However, to do internal mods you must have two things: Confidence in your decisions and extra money in case something goes wrong!

That being said, I must also mention that the hybrid Honda Accord with cylinder deactivation averages 25-27 MPG, which is the same as our RX400h's mileage. Consider the difference in vehicle weight and you'll appreciate what Toyota/Lexus has done.

[RX in NC]

wwest.

I respect your engineering knowledge as it pertains to our mutual transmission problems in our respective RX300s, but in this particular case (and given my background in investing and financial management) there's an old southern expression that fits you like a glove, namely:

"That ol' boy's got a lot more money than sense...."

[LEXUSMASTER]

What no one has really looked into is that the engine is already detuned off of the normal RX 330 engine. Secondly the engines main purpose is to charge the batteries. Engine power is only used on hard accleration.

[wwest]

What no one has really looked into is that the engine is already detuned off of the normal RX 330 engine. Secondly the engines main purpose is to charge the batteries. Engine power is only used on hard accleration.

←

No, the engine's MAIN purpose is to provide motive force for forward motion of the vehicle. Ideally the engine would NEVER be used to recharge the batteries so it is only used for that purpose as a last resort. If you drive, continously, for any reasonable distance at a constant speed you will find that the engine's use as a recharge source will be delayed until the batteries are quite low.

Think about it, if the engine is used to continuously recharge the batteries then where would the hybrid "put" the free energy to be recovered from regenerative braking on that next downhill slope or the next time you apply the brakes?

Conversely, on the highway during cruise the batteries are only used in a SC, supercharger manner, to make up for the lack of HP from the detuned engine when you need to accelerate to a higher speed, or quickly speed up, say to pass someone on a two lane road.

[wwest]

"That ol' boy's got a lot more money than sense...."

I often wonder if that was said to Edison during his many tries to make a functional light bulb.......or the Wright brothers when......

Back in 85 when I first proposed developing our company's current product set that is exactly what several of my key employees were saying, mostly behind my back.

Absolutely none of our customers, even to this day, will believe our product really works absent an actual face to face show and tell, dog and pony show.

Anybody out there want to buy a modern day implementation of a legacy minicomputer, say a PDP-11, a DG Nova or Eclipse? Or how about an HP-1000?

(above stated as a joke, not an actual offer.)

Such is life, the burden some of us choose to carry.

[RX in NC]

The light bulb and the airplane introduced electric light and heavier-than-air flight to mankind. You're just talking about !Removed! around with a production vehicle looking for a moderate increase in fuel economy.

That ain't gonna revolutionize the automotive world, my friend.

If that $50,000 is really burning a hole in your pocket, what you should do is take that money and put it towards the development of the first generation of hydrogen-powered automobiles. Hydrogen is the auto's future and this nation's exit strategy from the dependence on foreign oil. Find a way to get it to market within the next three years instead of what will more likely be ten to fifteen years.

Do that, and then I'll put you right up there with Edison and the Wright brothers and maybe even Les Paul....

[SW03ES]

I'm with him.

[patt]

I don't think it would be worth it monetarily or for cool reasons to do this...

You'd kill your warranty (and your resale value) and I seriously doubt you'd get a 20% gain in fuel economy...

I think you'd get more bang for the $$ by coming up with a custom flash for the ECU that will make the gas engine come into play later.

←

I haven't seen any convincing evidence that that would make the car operate more efficiently. When one can have the engine operating in its efficient range, the most efficient way to get power from the gas to the wheels is the direct path. The battery is there to provide power in place of the engine when the engine would have to run below its efficient range (moving at low speed) or to provide a boost in addition to the engine for fast accelleration (presumably also helping to keep the engine in a more efficient part of its range in addition to providing V8 performance when called upon to do so).

The most inefficient performance I see on my RX 400 is the first 5 minutes of operation when the engine is warming up. One reason the engine cycles on is to keep it in its warmed up region for efficiency.

Using the engine less frequently might hurt mileage.

[patt]

Please, only traditional naysayers need respond.

I am on the verge, cusp, of commiting to buying an RX400h.

My idea is to have custom ground intake cams made and installed to convert the engine to the atkinson cycle. I don't need V8 performance and as I see it the loss of about 20% would put me back into an RX330 equivalent insofar as HP/torque is concerned but also with an equivalent 20% GAIN in fuel economy.

For the rest of you, sorry, but my wife says I don't need encouragement in this possible venture. Also, I am finding that all the dealers I have visited, WA & OR, seem to have surplus RX400h inventory.

←

My engineering background is more electrical than mechanical.

Would you be able to back out the changes to return to the original engine cycle? If so, it would be interesting to get the car and drive it for 10 k miles or so with the original configuration and then try the altered cams to compare the mileage and performance.

Mileage varies enough between individual driving styles and types of driving (short trips vs. long trips, percentage highway vs city and the type of city driving, etc.) that it would be difficult to know if your mod made an improvement without a control experiment.

It seems likely that Toyota may have had other reasons than getting V8 power that drove the choice of engine cycle so it is possible that you won't make the savings you expect or you may find other problems. I think it would be pretty risky to try if you couldn't revert to the original operation.

[wwest]

Toyota...., "other reasons...."

My suspicion is that the 2.4L I4 could not be used, certainly not in the Prius' detuned form (atkinson cycle, etc), and still provide a satisfactory level of performance given the size, weight and Cd of the RX series. And I think it's pretty clear that the battery/electric system could not be used to make up the difference "full time", say during highway cruise.

So a bigger engine than the I4 had to be used.

And on that note I just can't get it out of my mind that the need to keep the catalyst fired up resulted in not using the atkinson cycle.

I drove an RX400h today, just briefly, city streets and freeway, and I cannot say that I felt the acceleration performance be all that great over my AWD 2001 RX300. It was definitely quieter at speed.

I was told that with a $5000 deposit I could have one of my choice, my specs, in as little as six weeks but not greater than 10 weeks.

[RX400h]

I drove an RX400h today, just briefly, city streets and freeway, and I cannot say that I felt the acceleration performance be all that great over my AWD 2001 RX300. It was definitely quieter at speed.

←

I believe the 0-60 MPH difference is 1.5 seconds, so if you don't accelerate aggressively, you may not be able to tell. Although I have never driven an RX before buying our 400h, I am very impressed with its power. Typically, pressing the gas pedal only an inch or so produces plenty of power. However, one of these days I'd like to line up with an X5 and do a 4-wheel burnout - just to show the guy what 650 lbs-ft of torque can do!

[wwest]

The only times I went WOT was out on the freeway already at a substantial speed, 55MPH or more. But certainly impressive.

[goofygrin]

I was told that with a $5000 deposit I could have one of my choice, my specs, in as little as six weeks but not greater than 10 weeks.

←

Come to Dallas... you can get most configurations here, no waiting... Be a nice trip home too, stop in Vegas :D

[wwest]

I'll be in memphis, and tyronza AR over the 4th. Driving my Porsche C4 home, finally.

I could stop in Vegas safely, but I dare not with my wife along.