Is F Aftermarket Performance Exhaust?

[noby76]

H.K.S is your best bet when it comes to tuning Japanese cars but check out the price.

http://www.hopupracing.com/pecatbaexsyl.html

[noby76]

http://www.hkseurope.com/about_hks.asp

[Mcauley]

ok there is loads of headers for our isf the best is novel from japan but the header is 6000 and 6000 for the exhaust. and offering about 40bhp

i went for the ppe headers from the usa rhd version i done away with the first 2 cats and i still have the oem exhaust. i also have the i code induction and toms filter this will offer about 35/40bho as for exhaust all the top japan and us companies make them.

i also lowered my car with super now. and am looking at a toms lip.

with only 2 cats it still passes a mot

[noby76]

geez £12000 just to make 40bhp will this even be at the crank or at the wheels? might aswell get an IS300 in good condition and spend the £12000 on a complete engine/gearbox overhaul and a Turbo Kit. and you can make more than 600bhp that will scare the life out of any GTR , Ferrari or LFA for that matter.

[Cable]

Hi there, I'm new to the forum as I'm currently in the process of looking to buy an ISF. A recent addition to the family forcing me to get a 4 door, and what better 4 door than the ISF :)

For my first post the last thing I want to do is upset anybody, it's not my intention and I hope people understand, but I felt like I should clarify a few things regarding aftermarket performance parts. I don't work for any companies that make or sell these parts so I'm not intending to gain anything from this; I actually work for a car manufacturer.

There seems to be a lot of negative talk about filters, exhausts and other tuning modifications, and how the OE parts will perform better because the manufacturer has tuned them as such. This isn't necessarily true, as the manufacturer has to deal with many compromises when developing a car, the biggest being cost and noise, with things like fitment/packaging also important as they can't have exhaust hanging low, which could get caught on something etc. Aftermarket parts do not have these same constraints.

The manufacturer's aim is for the car to fit in a certain catergory. With the ISF, Lexus basically wanted it to compete with the M3 and Audi RS4, cars which have a power output of approx 414 bhp. If it had any more than power than this then it would increase the cost of ownership, which would then affect the insurance catergory rating, negatively effecting sales; obviously something they don't want.
The engine they've used, as you all know, is a 5l V8, with a high compression ratio of nearly 12:1, and cylinder heads developed by Yamaha with direct injection, titanium valves, VVTI, and an inlet manifold with velocity stacks for each cylinder. These are pretty impressive specs, to which you would happily expect it to produce 100bhp+ per litre, much like its competitors have been doing for years. 417bhp falls somewhat short of that, indicating that restrictions are in place. The easiest way to do that is through restricting the intake and exhaust somehow.

The C63 is a good example, the M156 6.2 litre is one of the all time great engines, the first time AMG built an engine from scratch, rather than uprating an existing Mercedes engine. This engine is used in a variety of different models, the C63, E63, C63 Black and SLS, to name a few. The E63 having 518bhp, some 60bhp more than the C63. It has been found that Mercedes simply electronically limited the throttle body from opening fully, on the C63. All it takes is some minor tweakery with the ECU to unlock about 50bhp.

Back to the ISF, and you can clearly see that the exhaust is restrictive, particularly where it splits into two for the back boxes. Mercedes use a dual exhaust system all the way through, unlike Lexus who have used a single pipe until the back boxes, most likely to save cost and to add some restriction, bringing down the power to the desired level. Same goes for the intake. Noise also being a significant factor, as Lexus are known for their quietness.

Seing some of the aftermarket exhausts, such as the Joe Z and the Borla, which are dual systems, clearly free up flow. Same goes for the manifolds from the likes of Sikky, these removing the cats, which obviously isn't ideal, but sure does increase the power, figures from the sikky website seam high but plausible. http://www.sikky.com/view_item.php?id=148&catid=15. Individually they're not massive gains, but they're not something to sniff at either. The power graphs of the K&N fitted show a rather healthy increase, clearly improving its breathing at the higher end of the rev range.

An independant test

http://www.motoiq.com/MagazineArticles/ID/1827/Project-Lexus-IS-F-Part-1-We-Test-the-KN-Typhoon-High-Flow-Air-Intake.aspx

page 5 for the power graph

http://www.motoiq.com/MagazineArticles/ID/1827/PageID/2673/Project-Lexus-IS-F-Part-1-We-Test-the-KN-Typhoon-High-Flow-Air-Intake.aspx

And their test for the Joe Z exhaust
http://www.motoiq.com/MagazineArticles/ID/1853/Project-Lexus-IS-F-Part-2-We-test-the-PTS--Joe-Z-Series-Exhaust.aspx

Admittedly it's generally much easier to gain power from a turbo car, the Supra being a classic one, where you replace the exhaust and remove the cats, the exhaust gass flow sky rockets so much that the turbo's overboost. You actually have to place a restrictor ring in the system to calm the whole lot down. Coupled with a larger intercooler to keep charge temps down and a better fuel pump, you easily see 100bhp+ over the standard car.

The first things I will being doing to my ISF, once I get one, is to change the filter box out and fit a dual exhaust, most likely the Borla. I will also be changing the rear anti roll bar as it's one of the best bangs for your buck mods you can do for most cars; reducing understeer to make a more neutral ride.

Anyway, I hope I haven't offended anybody, and I'm looking forward to meeting up other owners, to discuss their experiences and thoughts. I'm always happy to stand corrected.

Best regards

Neil

[noby76]

nice write up Neil.. thing with all this is, are modern ECU's not meant to overwrite any new performance parameters gained from bolt on performance parts like intake and exhaust after 100's of miles of driving unless the ECU has been remapped to permanently accept the mods due to their intelligence? I might be wrong on this though.. Lexus vehicles for one all have locked ECU performance parameters on their vehicles.

[stevet]

Nice write up Neil.

The ISF tuning scene in the UK is tiny due to only about 200 sold so consequently parts have to be imported at a high cost. Plus the ISF is so good as standard.

If you get one keep us informed on any mods you do.

[Cable]

Hi, it's a fair point regarding the ECU's. This isn't my area of expertise either, but from what I understand is that during a 4 stroke cycle the available sensors, e.g. airflow meter, throttle position sensor, MAP sensors (depending on what car) will tell the ECU that, for the sake of simplicity, 1 litre of air has been drawn in. It then looks at a table of parameters for that volume of air and injects the desired amount of fuel into the mixture.

Just say you increase the air flow, whether it by exhaust, filter or forced induction, so now 1.1 litres of air has been drawn in. The ECU you may well have the parameter there for the correct fueling, but if not, the O2 sensor in the exhaust should pick up that the fueling may be running a littler lean and the ECU adjusts accordingly for the next cycle.

There's obviously a limit to how far it can go with this system, and most cope well up to a certain level, some even in a panic injecting too much fuel into the system making it run rich.

Another point is that with most intake/exhaust mods on a NA car, gains are mostly made nearer the top end of the rev range, because previously the standard exhaust/intake system simply could not flow enough near the top revs. If you look at the power graph on the link http://www.motoiq.com/MagazineArticles/ID/1827/PageID/2673/Project-Lexus-IS-F-Part-1-We-Test-the-KN-Typhoon-High-Flow-Air-Intake.aspx you can see that at 5400 rpm, the standard car's power plateu's, whilst the K&N fitted car's power continues on. Again for simplicities sake: the K&N fitted car at 6000rpm is essentially using the same fueling parameter (per cycle) as it was at 3000rpm, it's just that twice as many cycles are happening in the same time frame giving twice as much power.

Apologies if this doesn't make any sense; I'm a bit tired and probably shouldn't have attempted to type something like this, this late at night :D

Stevet, you're quite right, the ISF is very good as standard; I just can't help myself :P K&N already bought, and I haven't even got a car yet.

Night

Neil

[Glenn1981]

Great write up Neil!

A lot of these restrictions were present on my 350Z, it did change the performance of the car when I had swapped everything for aftermarket, but the big change was wiping the ECU for new software. I think I only saw 30bhp after spending loads though, trouble with NA engines.

That said, if in the ISF there may be 100bhp to release then it may be worth doing!

When you getting the F?

[noby76]

Sure makes perfect sense. I know car manufacturers compromise a little if not a lot with regards to the way they design intakes and exhausts to pass emission and sound laws and also to make the car drivable and bearable for daily driving and these mods are there to make the engine more breathable at the top section of the rev range and all will depend on engine design and ecu mapping of course and i recon there is some bhp waiting to be unleashed in the IS-Fs for sure waiting to see what you do with it once you get it. :-)

[Cable]

As much as I would like to, I don't think I'd go the way of the changing the exhaust manifolds; very good gains, but the cost involved in buying and fitting is very high, but also the noise level would be too much to live with as a daily drive, though they sound utterly fantastic.

I'd most likely go with an exhaust, filter and tweek the chassis, setting up the geometry to be a bit more playful. As mentioned the rear anti roll bar would be done and long term some Bilstein dampers would be good. I have my track car for the more extreme stuff.

I'm currently looking for a 2008/2009 Cadoxton slate grey ISF, preferably from a dealer. I almost had one from Coventry Lexus a few weeks ago, but my stubborness and principles got in the way of negotiations. They recently moved one in from a Lincoln dealer for me to look at, unfortunately its condition was... well... not loved. I think they've tidied it up since, but I would always know.

Neil

[Cable]

Intake manifold porting would be a nice little modification too. Something I would do myself, if I bought a spare manifold to do the work on at my leisure.

http://www.lexusfforum.com/forums/showthread.php?t=2219

[noby76]

Yeh most always think performance of a car solely lies on high bhp output but forget to invest and tweak things like brakes, better tyres and most important suspension setup. I personally recon 420bhp is more than enough power one will need on our roads or on a racetrack unless one wants to build for professional drifting or straight line quater mile runs or top speed runs. Bilsteins are said by many tuners to be ace but are quite pricey. Hey good luck with the search and don't forget to post some pics of the beast and the mods.

[Cable]

Agreed, my track car has modest 290bhp, but the weight being low (about 1150kg) and all the suspension/ geometry work, plus brakes and most importantly tyres, have made a car happily capable of keeping up with much more exotic vehicles.

If I'm honest, the main reason I'd be looking to change the filter/exhaust would be for the extra noise, as the sound of the car is one of the most important factors for myself. The ISF already sounds good from the intake, but the exhaust is almost silent; when compared with other V8's such as the Jaguars, Merc C63, M3 etc. If as a byproduct I release a few more ponies, then even better :)

Anyway, I sure am looking forward to getting an ISF