What's The Deal With The Lexus 2.5 V6?

[culubalo]

I'm not trying to troll I'm sure there's a good reason for this and I'd like to know what it is.

Lexus puts a 2.5 V6 into the IS250 and IS250C as well as the new GS250 (which looks to be the exact same engine but with 1kw more power).

What I don't understand about the engine is it doesn't make much power or torque and needs to be rev'd like mad to actually get to what little power it makes and the engine uses quite a bit of fuel for the power and displacement, it's rated at 9.7l/100km.

Meanwhile Toyotas 3.5 V6 which they put in the Aurion (let's not get into the IS350) produces substantially more power and Torque (200kw and 336nm in 3.5 vs. the 153kw and 252nm in 2.5) while using *only* 9.9l/100km.

It's a larger displacement engine yet it barely uses more fuel and it produces a very high amount of power and it does all this without requiring the premium fuel the IS250 does.

At first I thought the engine was just ageing (really like the IS250 which has been around for yonks) but since they put the exact same engine in a new car (the GS250 albeit very slightly revised) then Lexus MUST have a reason for it despite the lacking power and poor fuel economy, otherwise they would surely have wanted to put in a better engine or at least a 2.5 litre engine with better fuel economy.

Is there any defense which can be made for the 2.5 v6 or is it just a weak point in an otherwise great car?

[Sapphire Cam]

Just my five cents worth here - purely my thoughts, after driving one around for the past 5 years!), I actually think there are a few reasons. Firstly, the IS250 is a very heavy car - in fact I think the larger GS is slightly lighter that the IS. Secondly the automatic transmission in the IS250 is not ideally 'mated' to the 2.5L engine. The maxmium torque is achieved quite late - I agree, almost the antithesis of a diesel engine! However, what I have done is Ive had the ECU reset so the car is now re-learning my driving behaviour - which is actually using paddles to hold gears as well. After 2,000kms since the 'reset' the automatic is starting to hold gear about 300-500RPM more in 1st and the changes from 3rd to 4th and 4th to 5th are much smoother. I prefer to do the gears myself and hold about 500-750RPM more than what the automatic would do normally. It's a completely different car as a result, and enough toe for me. If only the automatic would be programmed this way!

I do feel a bit 'flat footed' though off the mark regardless, unless I'm holding 1st to about 4000-4500RPM, but once the car is going whereas many cars in the IS250's class start to lose grunt in that 60-90km/h range and plateau off, the IS250 keeps going.

I actually think the auto has been programmed 'tall' so as to achieve better fuel economy results on paper (especially for the European market and also the Californian market, which is a critical (and successful) one for Lexus - Lexus's are everywhere in California) - but having said that, I've actually have found a slight improvement in economy if I do the gears myself. Less gear changes, smarter gear changes and actually not making the car 'labour' by strolling in a too lower gear before having to kick down and rev its guts out, perhaps gives me the better economy overall. Average about 9.8 around town doing the gears myself as opposed to 10.2 on full auto (which I no longer do).

On the fuel side of things, you'll actually find, despite the labelling on the fuel lid, the IS250 engine can safely run on RON91 and E10. Performance suffers of course and Lexus service reps will advise against it, and I'll always chuck in RON98, but it can live off '91'.

[ilv1004s]

2.5L V6 is a entry model engine

australia had the entry model is250 only for years before the is350 came

GS250 Also a entry model

it's to compete with BMW and Audi

if you look on the specs

BMW320

Audi 1.8T

MercC200

instead of making higher spec models like bmw 323 325 328 330 335 etc

lexus chose the option of adding more standard options

People generally who buy is250's *new* are gentle and dont give a two cents about speed so for the main IS buyers market the 2.5L engine is perfect

lazy at speed but enough power to not a fool out of itself

bmw has probably sold more 320i's over 335 or 330's

like

reason for this higher fuel needing is due the compression ratio which is in the high side of 12.X.X ratio

whilist the IS350 or the Aurion with the 3.5V6 is at a lower 11.X.X ratio

Infact the 2.5L is not underpowered

biggest problem of the car is the weight

For instance Honda accord Euro is a 2.4L motor makes 147kw

the 350z with a 3.7L makes 230kw or so reason for this it's purpose is a sports coupe

unlike the IS250 it's a entry model luxury small saloon

I know u dont want to hear this but

to fix this problem lexus did bring out the IS350 back in 2006 to cater for the sports luxury market its just australia didnt receive the is350 till 2011

[onnzo]

Not everyone needs or wants power. I was fine driving it for over 4 years until I got into a is350. I still enjoy driving my 250, I just cruise when I'm in it.

[culubalo]

My problem isn't with the power it's how much fuel it uses for what power it produces, Toyota has engines in much cheaper cars with higher displacement, considerably higher power output and which only use marginally more fuel.

[BigDenis]

Cububalo, the IS250 is a very heavy car for its size.

[ldc]

OP is asking why isn't the 4GR-FSE producing more power, weight is one thing power output is another. Not related (unless you are talking about weight of the engine only which i doubt you are). If you bolt the 4GR-FSE into a Camry (not that it will fit) the engine still produces the same power give or take exhaust system.

The 250 isn't underpowered if you look at these sixers:

323ci, 2494, 125kW @ 5500rpm, 245Nm @ 3500-3500rpm

325ci, 2494, 141kW @ 6000rpm, 245Nm @ 3500-3500rpm

325i, 2497, 160kW @ 6500rpm, 250Nm @ 2750-4000rpm

Is250, 2500, 153kW @ 6400rpm, 252Nm @ 4800rpm

Eunos 800, 2254, 149kW @ 5500rpm, 282Nm @ 4000-4000rpm

As you can see there isn't much in it between the 325i and 250 interms of torque (we have 2Nm more) but the BMW has more power (we have 7kw less). If you look at the 800, how does 2.2L producing 149kW @ 5500rpm, 282Nm @ 4000-4000rpm fit in (Edit: it doesn't cos it's Supercharged lol) ?

Weight aside the Is250 puts out good power for 2.5L (better than the E46s). The only question is how does the E92 325i put out 160 and we only manage 153, and why is the max torque occuring at RPMS differs between the two?

Could it be the exhaust system?

Could it be the internals?

Could it be the technology?

Answer these questions and you'll have the answer (somewhat).

[onnzo]

Everything is built to a price. Lexus are optioned up from even the base models. If they were to throw in a more powerful engine the cost would come up too. That plus the cost / design work to set up production etc

[BigDenis]

My problem isn't with the power it's how much fuel it uses for what power it produces, Toyota has engines in much cheaper cars with higher displacement, considerably higher power output and which only use marginally more fuel.

OP is asking why isn't the 4GR-FSE producing more power, weight is one thing power output is another.

OP also made reference to the fuel usage of the IS250, for which the weight of the car becomes a contributing factor.

[ldc]

I'm sure weight is a factor but i wouldn't put it as a primary reason. Engine tuning (compression ratio etc) might have more to say, according to the these figures anyway.

Autos:

2007 Camry Sportivo, 2362, 9.6:1, 1535kg, 9.9L/100km <====> My other car.

2010 Camry Sportivo, 2362, 9.6:1, 1535kg, 8.8L/100km <====> Pretty much the same as 2007 in weight yet with refined engine gives less fuel consumption.

1997 Honda Prelude, 2156, 10.0:1, 1335kg, 8.9L/100km

2007 IS250, 2500, 12.0:1, 1560kg, 9.1L/100km

I threw in the Prelude cos the figures are funny lol. When i had it a few years back i'm sure i got more than 8.9L/100km AND it felt heavier than the Camry.

[BigDenis]

Might have something to do with your tires/wheels combo as well. I went from factory fitted 17" tyres/wheels to 255/40/18 & 225/40/18 (39 psi all 'round). Fuel went from 8.5L/100km to 9.4L/100km. Go figure.

[Atlantis]

My fuel use jumped up a ridiculous amount when I put 20" wheels on mine... I was getting very consistent 9.0L/100km... as soon as I put 20" wheels on, up to 10.2L/100km.

Pulled the wheels off about 6 months later and I'm back down at 9.0L/100km. 11% increase just because of heavier wheels. It doesn't take much extra weight to make a difference.

[Sapphire Cam]

Wouldn't be also attributed to the larger wheel circumfrence and what they will do to your speed readings, and in turn odometer and therefore fuel consumption calculation? With bigger wheels, your wheels are turning just that little bit slower, therefore the odometer and trip computer think you're travelling less kms than you really are.

[BigDenis]

Wouldn't be also attributed to the larger wheel circumfrence and what they will do to your speed readings, and in turn odometer and therefore fuel consumption calculation? With bigger wheels, your wheels are turning just that little bit slower, therefore the odometer and trip computer think you're travelling less kms than you really are.

Using the Miata.net website, comparing the 245/25-17 that I used to have to the 255/40-18 that I now have:

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference

245/45-17 4.3in 12.8in 25.7in 80.7in 785 0.0%

255/40-18 4.0in 13.0in 26.0in 81.8in 775 1.4%

Speedometer reading with non-stock tire is 1.4% too slow.

When your speedo reads 60 mph, you are actually travelling 60.8 mph.

This doesn't explain the big jump in fuel usage. A more plausable explanation would be the the new tires are wider with greater 'grip' and rolling resistance i.e. more friction, hence the increased fuel consumption. It would further explain Atlantis' fuel consumption figures.

[Atlantis]

Here's something interesting about rolling diameters... when I have the genuine Lexus 17" wheels on, the speedo reads too fast by 5%. When my 20" wheels are on the car, it's dead accurate.

(Confirmed by multiple GPS units).

[ilv1004s]

lets stay on topic guys

this thead is about the 2.5 V6 engine

not about wheels sizes and speedos

[BigDenis]

lets stay on topic guys

this thead is about the 2.5 V6 engine

not about wheels sizes and speedos

Ah, you see, if you'd followed the entire thread, you'd have seen why wheel size and speedo became part of the discussion.

The OP asked about the relative low power of the IS250 and its supposed high fuel usage.

You (ilv1004s) mentioned that the weight of the car was the biggest factor of the fuel usage.

Idc said that weight is a factor but he wouldn't put it as a primary reason (for the supposed high fuel usage).

I said that I notice my fuel consumption increased substantially when I changed my tyre/wheel combo to larger ones.

Sapphire Cam believes that the larger wheel/tyre circumference causes the odometer and trip computer think that you're travelling less kms than you really are (hence the discrepency).

And so on....

It was a progression of the discussion; moreso related to the fuel consumption of a supposed 'weak' engine.

[ilv1004s]

Denis please just stay on the topic

i dont want to put the hammer down

nor i want to have a internet war about who is right or wrong

as a mod i have to moderate the topic dont make my role job harder

But you are right in a way

but the main question was Wats wrong with the 2.5V6

Weight and wheel factor is correct relative to the answer

but going up to the point where the speedo is off etc i had to stop it there

to stop the topic going sideways

[coconut2001]

What I don't understand about the engine is it doesn't make much power or torque and needs to be rev'd like mad to actually get to what little power it makes and the engine uses quite a bit of fuel for the power and displacement, it's rated at 9.7l/100km.

Meanwhile Toyotas 3.5 V6 which they put in the Aurion (let's not get into the IS350) produces substantially more power and Torque (200kw and 336nm in 3.5 vs. the 153kw and 252nm in 2.5) while using *only* 9.9l/100km.

Is there any defense which can be made for the 2.5 v6 or is it just a weak point in an otherwise great car?

Rated fuel economy is not real world figures, some manufacturers tend to overstate (more likely) or understate these figures. I have not driven the aurion myself but I've read several reviews and tested fuel economy seems to be low to mid 10l ( eg here ) . My is250 averages 8.9-9.2 around town and that includes some *spirited driving*, whereas some members average more. Anyway, imo I don't think the is250 has poor fuel economy. I've seen worse and better.

[ldc]

My is250 averages 8.9-9.2 around town and that includes some *spirited driving*, whereas some members average more. Anyway, imo I don't think the is250 has poor fuel economy. I've seen worse and better.

What liquid gold do you use to get those figures. I used 98 only at Caltex and my readings are 10-10.5 constantly (hardly drive on freeway.

That said has anyone mentioned fuel type being the other factor to fuel consumption? Fuel economy is per engine tuning so i guess it comes up engine technology.

With the increase in wheel size that changes fuel consumption i found this to be true also BUT the ecu soon adjusts and everything goes back to normal.

My take is this.

The engine produces power and consumes fuel according to how it was designed to. As a prestige luxury car it is neither a sports car nor a "Camry" so they have to make it as what it is. Engine design (incl. technology) and management (ecu) is outputted to suit the car.

[Atlantis]

Could be that Caltex fuel isn't very good? I never use it due to poor experience with it a long time ago (same with Shell).

I use BP and Mobil now and get around 9.0-9.2 average per tank. Nearly all city driving, with a spirited cruise on weekends.

An ECU can't compensate for extra weight Idc... my averages were 10L/100km the entire time I had 20" wheels on my car, and dropped to 9.0 when I went back to 17" within the first full tank of fuel.

[ldc]

I'll give BP a try. I've experienced changes to readings when going to larger wheels (19s), however a couple of fills later it normalises back to the same figures as when i had the smaller wheels (18s). I could only think of engine management adjusting.

When you have bigger wheels it takes abit more to get the car moving (higher/faster reving - engine works harder - increases speed -- more fuel consumption). That said i can't remember what the figures for my car was when it was in 16s a long while back, but now it's 10.4L on 18/19s.

[samsung001]

wow..... i wonder how come you guys can get such a gd fuel consumption figure. 10 or even <10L/100km?

mine is always 12L +, i drive it normally too.

[Newbie]

Yes I am also wonder how ppl get such a good fuel consumption figure as I have a 2008 Sport Lux and running only 98RON both from Caltex and Mobil(7-Eleven) and never able to achieve bellow 11, always between 11 and 12 ... even with new tyres and brakes

[Atlantis]

Weird... I don't do anything particularly special while driving. The SL does weigh a little bit more than a Prestige... wondering if it could be that?