gnode

And there is the question about what if any input the ECU uses from those sensors for tuning purposes. Simply sending a signal that says "everything is ok" for the sake of not having a CEL is not enough, if that input is used for performance related calculations.


Kurtz: you are cluttering up this thread.

jcat_350

id imagine that was before they started making dual-channel output sims. if they work on a 2gs in a boosted application, they should work in a 2IS n/a. Hey, worse comes to worst, you install a neo and get even FURTHER control over a/f ratio.

lobuxracer

iTrader: (2)

This is why we're saying what we're saying. Nothing could be further from the truth. Engine's don't like backpressure no matter what. Less is better in all cases.

Putting in a cutout might make things better and it might make things worse.

The reasoning is this - a bigger pipe presents more pressure (not PSI, but PSI * in^2 of the pipe) to the engine, so the larger the exhaust pipe diameter, the greater the air mass the exhaust has to move out of the pipe before exhaust can flow. Moving air takes energy. The exhaust pulse has energy to move the air out of the exhaust and yes, the longer the pipe is the more energy will be needed to move the gases all the way out of the pipe. By the same token, the larger the diameter of the pipe, the more air has to be moved. Added to this is a larger internal surface area (by virtue of the larger diameter tube) to reduce the available energy for moving the air out of the exhaust by thermal transfer (the T) and by increasing the V in PV=nrT.

This is why your turbo spooled slower. Not "backpressure loss." Turbos work on pressure differentials and waste heat. Not pressure PSI, but pressure PSI*in^2 of the exhaust pipe. A bigger exhaust pipe means the turbo will undoubtedly spool later because the pressure differential is smaller.

So, your cutout might work better. And it might not. It will all depend on how you execute it. Saying the bends in the exhaust are the real problem is missing the forest for the trees. Saying the "restrictions" are the problem is again, oversimplifying the situation dramatically.

I've done a LOT of cylinder head work. I've learned that what is intuitive is often wrong. Intuition tells you straightening the pipes works better. But it won't matter how straight or curved the exhaust is if its the wrong size.

So here's a simple question - what's the difference between a "race" header and a "street" header? The obvious answer is the race header has bigger tubes. But why? To allow more flow? Not really. The race header is designed to make best torque across a narrower range of rpm typically at the high end of the rpm range. A street header is designed to make best torque across a wider range of rpm with a bias toward the lower rpm range. The header designer makes big compromises with both designs. Neither design is terribly concerned about "backpressure" and both are concerned about making good torque across the intended rpm range for the application.

This is why your top fuel drag engines have very short headers. They want to make best torque at high rpm and WOT. If you REALLY look at drag racing you'll see cars with full length headers and collectors because this design works best within the limitations of the class. Shorter headers would NOT perform better.

So, again, I wish you luck with your project because you'll need luck. Skill and engineering don't seem to be part of what you're trying to do.

Joe Z

iTrader: (10)

^^ Maybe I should consider making a 3" Full Exhaust for the IS-F and IS350...

... instead of the 2.25" for the V6 and 2.5" for the V8.

OK, never mind..
We already spent countless R&D hours designing a superior true dual exhaust system.

In the case of the IS350, the power was NOT better with 2.5" piping.

So just goes to show that bigger & free flowing is NOT always better.

Anyways to the OP, my experience is that the cut outs will not perform well on this car and will more than likely have a nice loss in Torque as well..

It will sound AMAZING and turn heads for sure...

Should sound similar to this:



I have seen and heard maybe 1-2 IS's with cut outs but never seen a DYNO..

So be the first and show us what it does.

Regards,

Joe Z

PaPaHoFF

iTrader: (19)

How hard is a ecutout to install? I currently deleted my secondary cats and resonator and have hks hipower and it sound sweet but brings a lot of attention lol. Id rather have it more subtle with just the HKS hipower until I flip the switch to make it sound nice.

gnode

Once you decide where to place it in the mid pipe, you will have to cut a section of mid pipe to make room to insert the cut out pipe, which is usually a Y pipe. The part of the pipe that branches off of the main pipe will have a valve (the cutout) already installed or you will have to weld or bolt one on.

You can either weld flanges on to the mid pipe so you can bolt on the cutout, or you will have to weld the pipe in the mid pipe.

Personally, I am going to buy a used stock mid pipe from someone to cut in to. That way I can also experiment a little with placement. That chalk method looks like a good start, but I doubt it is perfect.



Joe: Do you have any tips on dynoing with the automatic? I have never dyno'd an automatic before..

As far as "torque loss" goes.. it is important to not be tricked by dynos. More load on the engine will generally cause more torque in a dyno. A simple example is dynoing in 3rd gear vs 4th gear. Inefficient exhaust can effectively increase load on the engine, as it has to push harder to go up in RPM. This is what tricks people in the turbo world regarding spool and backpressure.

Joe Z

iTrader: (10)

^^ 4th Gear is the correct gear for Dynoing an IS250 or IS350..

I never did the dyno's personally, but you have to hit the sweet spot in 4th gear @ WOT (wide open throttle) so that it doesn't down shift to 3rd gear.

Trac Control completely TURNED OFF by holding the button down for 3 seconds on your 08'

Good Luck

Joe Z

gnode

Thanks for the tip!

lobuxracer

iTrader: (2)

Using snow mode prevents the downshift and doesn't affect power output at all.

4th gear & snow mode gives the widest rpm range without the gearbox interrupting the fun.