Exhaust Opens At X Rpm...

[Looney]

Has anyone attempted to change the rpm at which time the exhaust butterfly valves open at? Am talking about changing from 3600 rpm to something like 2500rpm....

Also, apart from going to lexus direct, where do people get spare parts for the ISF... like the 4 chrome tail pipes

[fjcfarrar]

There is no exhaust butterfly valve. The 3600 rpm change involves reconfiguration of induction/injection/valve-timing etc. required at higher RPM to give greater combustion efficiency. It could possibly be reprogrammed; but would only make engine characteristics worse.

[Looney]

so what you are saying is that the lovely noise found above 3600 is not possible at lower RPMs ???

Certainly dont want to go playing with things that have a dedtrimental effect to the IS-F ...afterall... Lexus spent a lot of time and money making it such a great car.... i just wish the noise was achieveable without having to have the revs so high...

[fjcfarrar]

so what you are saying is that the lovely noise found above 3600 is not possible at lower RPMs ???

Certainly dont want to go playing with things that have a dedtrimental effect to the IS-F ...afterall... Lexus spent a lot of time and money making it such a great car.... i just wish the noise was achieveable without having to have the revs so high...

The Gearbox, Engine Modes, Suspension Tweaks etc are all integrated together in the overall control system, so the exhaust noise can only really be easily altered by fitting a different silencers etc. However, have to point out that most of what you hear from inside the car above 3600 rpm is induction noise, so even a different exhaust may not do what you want.

[fjcfarrar]

If it is any help, the attachment was issued to Lexus Dealers when the ISF first appeared. It is a provisional document (Nov 2007), not generally issued to customers. Because it predates UK cars, there are a couple of small specification details that are incorrect - like tyre-pressure sensors, which were not actually fitted.

It contains quite a full technical explanation of what goes on with the gearbox and engine management in the various driving modes.

Because it started out written in Japanese & was converted; not all the graphs line up properly in the PDF file, but it is obvious enough.

Hope it helps.

ISF Spec MY08.pdf

[Tel]

Picking up on the Tyre Pressure comment the 2011 Model year has aTyre pressure sensor for 2 Sets of Tyres i.e Road & Track.

Tel

[fjcfarrar]

Picking up on the Tyre Pressure comment the 2011 Model year has aTyre pressure sensor for 2 Sets of Tyres i.e Road & Track.

Tel

Have never had tyre-pressure sensors; but have been told that they are not much better than giving the tyres an occasional kick & just tell you that you have a flat if you had not noticed the flop-flop noise & unusual handling.

Is this just "information" from jealous people who haven't got them?

[Tel]

I do believe they are good to have as the tire profile is relatively shallow they can often "look low" & the fact that, even on short journeys @ moderate speeds, the tire pressure increases by c.10% from the cold setting.

@ 130mph on an Autostrada TPWS is nice to have!

Tel