Gain Some Real Mpg (If You Want)

[davidbee]

i've found recently that when using an obd2 reader via my laptop the car does not get to normal operating temp and does not run into 'NORMAL' fuel mode until it's really hot, it does take a considerable amount of time to do this, if your only making a 20-30 minute trips twice a day and it takes 15-20 minutes to fully warm up, if you can make the ecu think the car is actually warmer than what it really is the fuel delivery goes to 'NORMAL' sooner and then uses less fuel as when it's cold it runs rich. if you was to make it 'think' that it should be running 'NORMALLY' then you can save on fuel on your journey, this can have a real good affect on saving fuel if you only drive for 30 minutes twice a day and you can make the car run 'normally' for 25 minutes of the trip rather than being in the normal range for 10 minutes of the trip and rich for 20 minutes, i can't be bothered to do the maths but you work it out, a rich mixture for 20 minutes or a normal mixture for 25 minutes of a 30 minute trip? i know what i would choose.

currently i have a 5kohm potentiometer wired in parallel with the 'engine coolant temperature sensor' at the moment i am just twisting small amounts and seeing how the car runs and performs and will also be checking the condition of the spark plugs to see if any fueling issues are showing up, the car still feels fine even with the pot at half way around, if i go anymore than that the car has trouble starting when hot and feels a bit 'lean' in mixture, the other issue is the fact that the weather changes all year round so different intake temps can have an effect and so can fuel quality blah blah blah, if you want to try this yourself then go ahead if you don't like the idea then do't do it. (it's my car i do what i want, it's your car you can do what you want) don't like what i do then don't do it to your own and vice-versa. i will not be held responsible if anything happens to your car which 'you' did, i can write up a guide with pictures if anyone really needs it? once i have found a decent setting using the potentiometer for all-year round use i will test the ohms and then just wire in a small resistor, some guys selling this stuff on eBay making claims you can make 20+bhp is a load of rubbish but the silly fools that believe it go and spend £9.99 buying the resistor that you can get from an electrical shop for about 20 pence.

if i find 'good' results i will inform you of what the ohms was that gave the better results, the ones on eBay are 4.7kohm but it's not the right type at all if wired in parallel. my pot is set now at about 2.5kohm but i need to do more testing as it doesn't quite feel right at the moment, although i am saving fuel (i am putting less fuel in the tank to get me to the same place as what i would do every week and i have been enjoying my car more as i can go on more trips now the fuel is more affordable and i'm using less fuel) i also have a heavy right foot so even doing this i can floor it more and to be totally honest i feel a lot happier with the car and myself (man and car bonding) my main problem when buying this car was the fact i already knew they are quite juicy as well as a few other things like the front tire issues and the cd player and the rear bushes and the sticky calipers and the list goes on, most of my issues are resolved, now to get the fueling down and squeeze some power out of the 1g-fe, one day i will see what the dynp says.

also if your interested in taking a look at what i did to modify that kick at 4500rpm have a look on the lexus is200 page on facebook where i have tried different options and have found good results, like the page as that's where i am most of the time, i can answer questions and give some advice if you need it or just show off your car with some cool pictures :)

here is the page https://www.facebook...79809172041079/

my name is David Bishop https://www.facebook...avid.bishop.566

Dave.

[sjrainsford]

Interesting.

Keep us updated with your findings. I do believe it takes them too long to switch to full closed loop control. But I also have my concerns with what you're doing, because you're actually modifying the fuel map to an extent and leaning it out. Lean = hot etc etc.

BUT - I'm all for saving fuel and I've always believed there is potential to improve the IS. It would have helped if lexus had used mass air flow monitoring rather than old style MAP.

[clifton 94]

hi 20 minutes to warm up is a long time i'm sure mine warms up a lot quicker than that but i will check on next journey

[davidbee]

Interesting.

Keep us updated with your findings. I do believe it takes them too long to switch to full closed loop control. But I also have my concerns with what you're doing, because you're actually modifying the fuel map to an extent and leaning it out. Lean = hot etc etc.

BUT - I'm all for saving fuel and I've always believed there is potential to improve the IS. It would have helped if lexus had used mass air flow monitoring rather than old style MAP.

i understand what your saying about it being lean=hot but i have taken the potentiometer to it's leanest levels and still had no detonation, the car is NOT turbo'd so the lesser fueling isn't making a lot of difference as the car see's ZERO boost levels, if it was boosted i would want to see LOTS more fuel for more psi.. also going to lean just makes the is200 idle and rev poorly, i have tried it at normal temperature with the throttle wide open in 5th gear at low speeds and zero det occurred but it didn't feel very nice to drive and some miss-firing was at idle and that's the reason i have turned it to half way, i also pulled it back a touch earlier today and cant fault the driving ability with it like this, it feels exactly the same as what it did if it was standard. just i'm using less fuel. i will leave it like this for a week or two then i'll take out the spark plugs to see any tell tale signs, you know you can read all sorts by looking at the plugs?

also with the lean=hot thing it's not making any difference as the cooling is done via the thermostat and the cooling fan in the radiator, and we have zero boost so not really a major issue, hence the reason 'I' am the tester and it's my car, if it brakes then i deal with it then, it shouldn't though, i've been a mechanic for 10 years, i know what an engine is supposed to sound like and know when it's running poorly.or not and today mine seems really good, i'm impressed but not satisfied until i see those spark plugs in a few days.

[sjrainsford]

Am interested to see your final results then. Think I may join in later on and do a similar experiment. My general journeys are 20+mile trips on mainly A roads, so I see any improvements quite quickly.

Are you currently keeping the resistance in circuit all of the time, or removing it once the car has reached standard operating temperature to achieve normal burn? In other words, are you trying to lean the mixture out at all temperatures, or just when cold?

Incidentally, how did your ACIS valve mod go? And did that give any gains in terms of fuel economy or otherwise?

[sjrainsford]

Any news?

[Stuart Aspey]

This sounds fantastic. I'm not mechanically minded, but if I asked a mechanic I use to fit this, would he?

[davidbee]

i wouldn't ask any mechanic to do anything at the moment, i've been using the obd2 connected to my laptop and reducing the temp by 1 degree after a week or so or driving, it still isn't quite right on cold mornings it has some starting issues, i wouldn't do anything just yet. i'm not satisfied yet.

[davidbee]

Am interested to see your final results then. Think I may join in later on and do a similar experiment. My general journeys are 20+mile trips on mainly A roads, so I see any improvements quite quickly.

Are you currently keeping the resistance in circuit all of the time, or removing it once the car has reached standard operating temperature to achieve normal burn? In other words, are you trying to lean the mixture out at all temperatures, or just when cold?

Incidentally, how did your ACIS valve mod go? And did that give any gains in terms of fuel economy or otherwise?

remove the pipes and then plugging the pipes then refit them to the intake and the valve, works a treat! no more waiting for the revs to slowly build up and then at 4500 it goes like a rocket, i can over-take quickly and smoothly blasting from 50-80 with no issues :D

[Stuart Aspey]

i wouldn't ask any mechanic to do anything at the moment, i've been using the obd2 connected to my laptop and reducing the temp by 1 degree after a week or so or driving, it still isn't quite right on cold mornings it has some starting issues, i wouldn't do anything just yet. i'm not satisfied yet.

Thanks Davebee. I'm quite fortunate that I'm a cautious driver. I'm getting 400+ miles from my 70 litre tank regularly with a mix of b roads, hilly driving and stop/start city driving ( including short journeys ((2 miles))

I will be fitting Hankook, b rated for fuel efficiency, tyres and possibly filled with nitrogen mix with oxygen (or whatever they use when they put the green caps on) to further help fuel efficiency.

I know a lot of people have said that if I want a more fuel efficient car, I shouldn't have bought an is200. But I really like this car and I'm happy with the current levels of mpg, but feel I could get more out of it.

[sjrainsford]

Am interested to see your final results then. Think I may join in later on and do a similar experiment. My general journeys are 20+mile trips on mainly A roads, so I see any improvements quite quickly.

Are you currently keeping the resistance in circuit all of the time, or removing it once the car has reached standard operating temperature to achieve normal burn? In other words, are you trying to lean the mixture out at all temperatures, or just when cold?

Incidentally, how did your ACIS valve mod go? And did that give any gains in terms of fuel economy or otherwise?

remove the pipes and then plugging the pipes then refit them to the intake and the valve, works a treat! no more waiting for the revs to slowly build up and then at 4500 it goes like a rocket, i can over-take quickly and smoothly blasting from 50-80 with no issues :D

So you're saying that to get the acis to always be in the same state it is above 4000rpm, you have to block the vacuum feed to the valve?

[davidbee]

Am interested to see your final results then. Think I may join in later on and do a similar experiment. My general journeys are 20+mile trips on mainly A roads, so I see any improvements quite quickly.

Are you currently keeping the resistance in circuit all of the time, or removing it once the car has reached standard operating temperature to achieve normal burn? In other words, are you trying to lean the mixture out at all temperatures, or just when cold?

Incidentally, how did your ACIS valve mod go? And did that give any gains in terms of fuel economy or otherwise?

remove the pipes and then plugging the pipes then refit them to the intake and the valve, works a treat! no more waiting for the revs to slowly build up and then at 4500 it goes like a rocket, i can over-take quickly and smoothly blasting from 50-80 with no issues :D

So you're saying that to get the acis to always be in the same state it is above 4000rpm, you have to block the vacuum feed to the valve?

exactly that :) i tried various things first like connecting it directly to the inlet but i got no power past 4500rpm it was sluggish, i blocked the pipes now i just get what feels like a normal full revving engine.

Stuart Aspey

before i got my lexus (i wanted one for a year and a half) i knew it was the type of car to drink a bit of juice and i said i wanted to fit a diesel, even a 1.9 tdi from a vw golf would feel better to drive than the sluggish straight 6 24 valve and with better fuel consumption. even the old petrol redtop engine in the vauxhalls was only 4 cylinder and making the same bhp and used less fuel. why can't we have any of those options in standard form in the lexus is200!

i always felt that i had to struggle to get my car from A-B with the same amount of fuel as what used to be put in a mg-zr 120+ that we used to use, i noticed my foot was quite far to the floor in low rpm's but i wasn't really going anywhere fast but was probably using quite a bit of fuel even at cruising speed or just to even overtake a lorry was hard work and had to build up speed with my foot down quite hard before the car reached it's powerband at 4500rpm then it was safe to overtake. since bypassing the valve on the underside of the inlet manifold i no longer have this problem, i can be driving along in 4th gear at around 50 behind a lorry and then pushing my foot down the car picks up and goes and i'm hitting 80mph pretty sharpish! this is good for me and i feel it was the best FREE mod i've ever done to the lexus because i like power on tap and i feel i have more control over the power it gives rather than letting the car think for a minute and then get up and go. it may be a good idea for you to try this and just see if you save any fuel just driving normally the way that you do now, with maybe even less throttle opening to say 40% instead of 60%, i can't say if it will help you or not but it's up to you try it out, if it don't work just connect the pipes up again and you'll be back to exactly how it was before.

[Harry N]

Good morning David , unfortunately i`m not on Facebook . Would it be possible to copy the relevant pages of this FREE mod here ?

Cheers

Harry

[sjrainsford]

Isn't the solenoid valve quite easy to get to? It's just the actual ACIS valve that's difficult to get to I thought. I'm sure my solenoid valve is located by the wheel arch strut mount sort of down by the throttle body area.

[davidbee]

i'ts one of the hardest things i've had to get to on the lexus, the solenoid and the valve is tucked under the inlet manifold, i suppose you could remove the alternator but i did mine by going under the car behind the front wheel with just enough room to get one hand up there, pulling of the pipes was difficult, the valve isn't sitting flat and it is hard to feel which way to pull the pipes to get them off, they are a little bit stuck, don't expect to be able to get any screwdrivers up there to pry the pipes off because you don't have enough room.

[BillNick]

The theory is genius....I am keen to follow this thread for finite results and recommendations. Thanks to you Dave for playing guinea pig ;-)

Only wish I was a bit handier around the engine compartment. I can service, brakes, standard shizzle like that but taking my inlet apart is not something I shall be attempting. I will pass your results to a trusted Mechanic however.

Intriguing....these cars are over 10 years old now, its about time someone cracked them!

[Diablo333]

I am really keen to try this on my IS200- I am in South Africa, so our climate is a little warmer here, nevertheless I once the ecu sees what it thinks is a warm motor it will maintain normal fueling. Any verdict yet on the right resistor to use? Oh and do you connect in parallel with the sensor?

[ColinBarber]

A few points:

Questions around the poor performance/economy of the IS200 engine - this is mainly because it is a very, very old engine design - the 1G-FE was first used around 1990 and is based on a design that is 10 years older than that. It is designed for smoothness not performance. The FE in the 1G-FE engine model relates to the head/valve design, the performance variant is GE and believe it or not FE is actually the economy design.

ACIS - If you open the ACIS valve then you shorten the inlet. This provides more power at high revs, which is why it opens around 4,000 rpm, but you want a long inlet at low revs to increase torque. Toyota wouldn't have bothered with this complexity if it wasn't of benefit. If you keep it in one position then you lose one way or the other and I certainly wouldn't want to lose torque on an engine that doesn't product much in the first place. I believe there are third party controllers so you can alter the engine rpm at which it opens, this may be of benefit to tune to a specific engine / driving style but you don't want to move +- 500 rpm from the standard.

Economy - Toyota/Lexus have traditionally fuelled slightly rich, therefore avoiding a lean situation even with manufacturing tolerances, to improve engine reliability, so there is room for improvement provided you can tune for a specific engine. Once you go closed-loop however they isn't much that can be done - the ECU will do all it can to hold a 14.7:1 air/fuel ratio using the O2 sensors because this ratio is need for the cat to work, any outside influence on the various sensors will get trimed out straight away. You either need to alter the ECU behaviour or provide false O2 feeds into the ECU if you want to improve closed-loop mode but then you run the risk of failing emissions because the cat isn't working well.

As an aside, it is a shame that governments are still insisting on cats. Engines can be designed to run leaner than 14.7:1 these days, we would instantly see economy improvements in new vehicles without them.

[Diablo333]

Valid points there Colin,

On the topic of the ACIS valve, there has been a fair amount of discussion about the success / viabilitiy of the various ACIS / TVIS implementations that Toyota have introduced on their motors over the years, Certainly for a motor in it's standard guise there may be little that can be done to improve on the system, however the one thing about dealing with an old motor is that there is more likely to be room for improvement. In my case the first proposed modifications will include polishing and porting the intake and applying a piggyback management system and hopefully later adding a low pressure supercharger and gas flowing the head.

Thankfully for the like of us in South Africa, there is no regular MOT testing and no easily enforceable emissions laws. So unless your vehicle is belching black smoke you are not going to get into trouble and you can modify the motor to your hearts content. Depending of course on your social conscience :-)

I would love to see a dyno graph of a 1gfe motor with the ACIS valve in normal vs always open vs always closed operation, mainly to prove that it isn't just a fancy intake muffler :)

[sjrainsford]

Hi all. As this has been a little quiet of late, and being an electrical engineer I like to tinker. I've started looking into fooling the water temperature sensor reading as well. Currently I'm using fixed resistance to take measurements and run tests as I have stacks of them knocking around the garage.

I will however probably move to variable resistance, but in my case by adding a second temperature sensor.

For those interested, I'm currently running about 3500ohm in parallel with the sensor. This is quite easy to do inside the engine management housing in the engine bay. It's just a case of stripping two wires.

With this the car shows that it is warming up within about a minute of driving. Much quicker than standard. Going too far makes it difficult to start though, so I've found that this resistance is about right in the current weather. The car is obviously much less rich on start up just by standing behind it ticking over.

I've not yet had any figures to speak of as the last tank full was used during experimenting. I'm currently on my first tank full with it untouched. I'd say this would have a bigger impact on people doing shorter journeys rather than people who only do long runs.

[ColinBarber]

I would love to see a dyno graph of a 1gfe motor with the ACIS valve in normal vs always open vs always closed operation, mainly to prove that it isn't just a fancy intake muffler :)

Reducing intake noise is another benefit of ACIS however it isn't the main reason. Toyota have been using this system in one form or another for 20+ years now - think of all the money they would have saved by not fitting it to all those vehicles if it didn't achieve anything.

They also continue to develop the system and therefore spend R&D money. The IS has just a two stage system where as the series I RX for example had a three stage implementation.

It would be interesting to see dyno graphs for the 1G-FE. If you search around on the net you will find results from the 3S-GE from Celicas and MR2s. Some of their results are interesting in that seem to want to stop it from coming on, rather than making it come on early, because they are seeing a drop in torque however I think if it didn't come on the engine wouldn't continue to rev so freely past 6,000 rpm.

I must admit I did spend a bit of time trying to alter the ACIS behaviour a number of years ago on my old 3S-GE MR2 without seeing much difference, I then gave up and just got a 3S-GTE MR2 Turbo instead ;)