What's The Perfect Drivetrain For Your 3IS
 

Toyota's V6 is a fine motor which has proven itself to be immensely reliable but the design is clearly getting long in the tooth now being carried over from the 2IS. If it managed to easily get 30+MPG on the highway I would find it to be acceptable enough, but given the mpg ratings of this car it got me thinking - what would be the perfect drivetrain for this car?

The 200t is a pretty good engine, good design but the performance and efficiency is nothing particularly special. The IS250 gets dismal fuel economy for the amount of power it provides. So the perfect base engine replacement would be a 2.5L inline 4. A large displacement 4 cylinder would work much better than a small displacement V6 due to the extra torque. I have a 2.5L inline 4 in my Mazda 6 and it is the only 4 cylinder engine I have ever been pleased to live with on a day to day basis... Throttle response is sharp, strong torque from down low, very easy to service and easily gets 40MPG on the highway. A 2.5L V6 is much more peaky and will obviously make a superior sound but a bit more difficult to service and the MPG is terrible in comparison.

That leaves me with the 3.5L V6. I think for this upgraded "350" model, a 3.5 or 3.7L Inline 6 would be a wonderful alternative. If you can tune the engine correctly the MPG will be fantastic, but, more importantly, overall engine refinement and the amount of torque it is capable of producing just off idle would be monstrous. I always felt very impressed with my 2011 BMW 528i which is a 3L inline 6 with merely 240hp, but imagined an increased displacement version of this same 6 cylinder motor inside a lighter more reliable Lexus would be something truly fantastic. Plus, Toyota wouldn't have to worry much about extra manufacturing costs because the inline 4 and inline 6 cylinder versions can easily be built off the platform.

So what is the solution for the next generation Lexus IS? Toyota has already partnered up with Mazda and plans to use their fantastic Skyactiv-X compression ignition technology. It would be wonderful if Lexus incorporated this technology into a inline 6 cylinder version for their next sports sedan.

As for the transmission, are you guys happy with the 8 speed or would you prefer the 6 speed? If the transmission mapping is very precise, gear hunting and jerky shifting should be an issue of the past. 8 gears is a lot, but still offers benefits due to the close ratio spread especially in city driving.

I think a return to the straight-6 engine would be great. I had a first gen IS300 a few cars before my current IS200t. As far as transmission, if lexus spruces up the tuning of the 8 speed, that would be great. From what I've read, it's almost the same unit as the ones in the F cars, just tuned less aggresively. It is a bit annoying how it hunts for gears sometimes, but it's 90% there in my opinion. Either that, or maybe adopting the ZF8 that BMW is using. Those seem to be holding the power quite reliably while providing a great driving experience. I agree, 8 gears does offer its benefits with its close ratio.

I agree, but the 2JZ engine is not that good without a turbo. I want something more optimized around natural aspiration.

Actually, I was going to comment in regards to the ZF 8HP. That is a truly fantastic transmission. It's literally telepathic with the way it chooses gears. ZERO gear hunting of any kind. I would prefer for it to be programmed not to be so aggressive with the way it goes straight to the top gear and is always very reluctant to downshift unless you give the throttle a real good stab. Also, Inline 6 engines allow the manufacturer to be even more precise with their transmission mapping, especially with the way it all works pottering about at super low RPM's,

An 8 speed transmission is fantastic when done right and paired to an inline 6. Try driving a bmw 340i and you will see what I mean. These transmissions are all bulletproof as long as you regularly service the pan filter.

I think the naturally aspirated engine is going to start to disappear. The way electrics & hybrids are gaining popularity and the way turbos are becoming the norm because of fuel economy and power output I don’t see big naturally aspirated V6’s existing, or most naturally aspirated engines for that matter.

You’ve got Ford and Mercedes with Turbo 4-cylinder engines putting out 350 HP. What I don’t get from a business perspective is why didn’t Toyota just keep and use the 2jZ in almost everything?
Stick it in lower end cars naturally aspirated, single turbo in mid tier vehicles and twin turbo’d in higher tiers. They would have a bulletproof, legendary, highly tunable motor in their whole line up. Wouldn’t it have saved them millions in research and development and not having to make so many engines? Imagine if instead of all the different V6’s they made they just used 2jZ’s.

First off the 2jz is way too outdated so it makes sense that we didnt see it again second off they made a v6 so they can easily fit it into both FWD and RWD applications across the lineup.

If mazda and toyota plan to work together we will see supercharged compression ignition which is even better.

Please add dual clutch tranny.

I do not think an n/a engine is coming and I do not think it belongs. Other MFRs are already on their 3rd, 4th generation of turbo engines and Lexus is just barely starting. Anyone who test drives anything else turbo powered is going to go F that as soon as they test drive an N/A engine. They're already doing that and IS sales are poor.

Also no you can't really get great MPG out of an n/a engine. The turbo 4 out of the new BMW is already banging 43+ mpg highway. that's in sport package trim with summer rubber too. that's approaching Prius territory...

No way . Way too complex and completely unreliable for regular driving. Plus if you're stuck in stop and go traffic, you're screwed. You're not supposed to let a dual clutch roll out. It's either you're stopped or in gear accelerating.

ZF's 8 speed is the best all around unit.

Like I said the future is supercharged compression ignition. Generally speaking you can make an NA engine efficient if you want to.

The truth of the matter is I'd rather take NA over turbo any day of the week even if I'm sacrificing power. Most turbo engines I've tried arent linear at all, soft throttle response, turbo lag and they run so rich at high rpm. Unless you have a 68mm precision turbo the power tapers off at high revs because the average engine is not designed for this sort of driving.

turbo engines are only designed to be specific under a very specific driving loop. Think EPA testing. The way the average person drives (always on boost, like an idiot) most turbo engines experience absolutely horrid mpg.

Luckily Mazda has figured out a way to get good driveability with a huge increase and efficiency and smartly enough, Toyota wants to incorporate it.

But actually I have to admit, when I test drove the NX300 before buying it I was amazed at how linear the power delivery was for a turbo engine. It feels quite good.

Mazda for example with their skyactic engine use a 4-2-1 exhaust header which cools exhaust temperatures and allows them to use a very high compression ratio amongst other brilliant pieces of engineering. They have achieved excellent real world fuel economy from a NA engine. Compression ignition takes this a step further by using a supercharger to force even more air into the combustion chamber. Not for huge levels of power, but an extremely high air to fuel ratio. The end result is an engine which has a much broader torque curve across the rev range allowing engineers to apply a very short final drive ratio without sacrificing fuel economy. The end result is the performance and feel of an excellent gasoline engine but 50mpg like a diesel and dramatically reduced emissions.

now add this technology to an inline 6, and the end result is monstrous torque while still maintaining excellent efficiency.

It felt very much turbocharged if you ask me. That's not a bad thing, but it also has some turbo lag. Nice broad torque curve - a little too broad to be NA. The only NA car I've driven that felt like that was a Camaro SS, but 6.2 liters will do that. (And of course, that Chevy has a lot more torque than pretty much any other car I've driven outside of a Model X P100D.)

I honestly think the perfect drivetrain for the IS would be a much better torque-converter auto, like a ZF as you said earlier, combined with a lineup of small-ish turbo engines. Perhaps the 3.4-liter engine from the LS could make an appearance as the top engine, if it would fit in the engine bay, However, I can't deny how cool it would be to have an IS with the current F drivetrain - maybe even the 10 speed auto from the LC... lots of possibilities. :) With the 6-speed in my AWD car, even the 8-speed seems like a pretty nice upgrade. :D

I am a huge fan of NA engine setups from a point of reliability and ease of maintenance, but I understand the limitations of it from a fuel economy standpoint. Take a look at every NA V6 used by other mfgs and you'll see pretty similar MPG ratings in the mid to low 20s and some lower (Mustang/Camaro).

I would love to see either the new Z4/Supra B52 in the IS with the same ZF tranny, but I would also like to see the current V8. If I were to never touch a single drivetrain component and just drive the car stock, I'd go with the V8, but it's hard to overlook the potential from the B52.

For now, I look forward to enjoying the trouble free daily driving that the current 3.5 V6 provides, and I'll deal with the fuel costs.

The transmission is what really holds back the AWD cars, combined with losses with the AWD drivetrain. The 8-speed 350 models get decently better fuel economy, and other products that use the 2GR and an 8-speed also do even better - for instance the new ES 350/Camry V6 - though, those also have less drivetrain loss due to having a more efficient transverse engine mounting.

There are a lot of things working against the current V6 in terms of efficiency, but then again, a new transmission would seem to go a long way. Here's hoping it'll be the 10-speed...

A large displacement inline 6 has more potential than a V8 and is more likely to have better reliable. Especially the B58 BMW straight six compared to a similar V8 counterpart.

I'll easily choose supercharger, compression ignition or a big straight 6 NA over anything else. It's the best all around.

The truth of the matter is, the only reason why you guys see NA motors the way you do is because your only experience with this sort of engine pertains to a V6 engine which has been on the market since 2006. 26MPG from a 3.5L engine was a great figure 15 years ago. Reliability-wise there is nothing wrong with Toyota continuing to produce such an engine to this date. They have built way too strong of a reputation over the years off loyal customers to bother making and revolutionary changes which would cost not only tons of money but take longer for them to bring newer technology to market..

There are a number of benefits with an inline-6 engine over a V6 hence which is why many manufacturers are switching to thus layout after several decades of absence from the lineup. First off, Inline 6 engines have inherit perfect balance which reduces the need for balancing shafts while still ensuring an even firing order with near perfect smoothness and refinement... The result is an engine that sounds and feels like no other. You need to experience a modern one such as in a BMW to understand the true beauty of such an engine and it's unique characteristics over a V6 engine. With a V6 engine, it is much more difficult, probably next to impossible to be able to fit a lengthy 4-2-1 exhaust header on both cylinder banks which greatly limits potential when it comes to squeezing the most amount of efficiency and torque out of the motor. V6's by design are quite limited in this regard.

If the Japanese focused more on inline 6's especially back in the day, that would be wonderful. V6's, even with balancing shafts are not as smooth or refined and tend to nearly rattle themselves apart as the mileage accumulates. A well-built inline 6 engine will stay true and run perfect smoothly for hundreds of thousands of miles on end. It is inherently the most durable and reliable engine design you can possibly think of.

The truth of the matter is, while today's consumer market seems to love turbo engines for whatever reason, there is absolutely no future for them and never was. It is simply a fad or a niche to satisfy EPA efficiency ratings by being efficient only under a very specific driving style - think EPA'S efficiency testing loop. In the real world, they use tons of fuel and in my opinion could never live up to the characteristics and feel of an NA engine even if they do make more torque and HP.

Without Mazda's Skyactiv technology I can't think of any other better way for the internal combustion motor to exist merely for the sake of advancement. My educated opinion is that Lexus would continue to smartly stick to Natural aspiration for the exact same reasons Mazda did and develop Inline 6 engines for their newer models to maximize power and efficiency and maybe utilize some sort of mild hybrid system. Jaguar/Range Rover and Mercedes have already reverted back to the straight-6 Maybe also design some sort of diesel motor.

I urge you guys to try test driving a 2006 BMW 330i or 2007-2011 328i with the Naturally aspirated inline 6 while you still have the chance to really see what I mean. The rare factor of this engine makes it such an honourable experience to operate in a vast world of mediocre, soulless V6 engines.

I disagree, Lexus has a large market of people who were tormented by BMWs/Audis/Benzes and made the jump, so reliability is important to them and I totally applaud that. I went from an F30 340i w/ M-Sport and M-Performance to my IS350 F-Sport, and I couldn't be happier despite being down on power. Until modern turbocharged motors can be reliable over 150k+ miles, I'm not willing to buy another.

Before my 340i I had a 335i, and both were horrendous pieces of **** that I wouldn't let anyone that I care about buy. The 335i I kept until it had 70k miles, and it had inconvenient issues since new, but started to become more problematic at around 60k, including a breakdown on the highway in Vermont and another across town within a 6 month span. The 340i was a POS from day 1, and over 20k miles it had its engine, front diff, 2x water pumps, and a turbo replaced. It's really unfortunate what happened to BMW, because my E46 went over 260k miles before I sold it, and the guy who bought it still drives it today. Either way, point is the 2GR is fine for now IMO, the car is fast enough and I know that it's going to be reliable over the long haul.