ECM details

Lo bux... I have a few friends with drive by wire cars and when they've "chipped" their cars they say they feel increased throttle response. Is this accurate or is it just psychological? If it is accurate, how is this achieved. Also, would we benefit at all from a higher redline? I figure that since our maximum hp and torque are achieved below 6200 it wouldn't be useful at all. Would a turbo setup change those peak hp and torque measurements making it useful? Thanks for the input

It could be accurate. Drivability is a funny thing, and with the cable operated systems the ECM looked at the throttleplate position (using a TPS) to determine how much extra fuel to dump in to improve tip-in response. It worked alot like the accelerator pump on a carburetor.

With drive-by-wire control, the ECM controls the rate of opening directly, so it doesn't need a sensor to tell it where the throttleplate is, it already knows because it is controlling it directly. This means the fuel dump for tip-in can be better matched to the engine's needs.

It doesn't mean the factory settings are optimized for hard use though. They are optimized to give most reliable operation under a wide range of conditions. If you narrow down that range of conditions and go a little closer to ideal, you may find better response. I suspect that's what your friends are commenting about.

Red line starts as a function of mean piston speed. 20 meters/sec is the generally acknowledged acceptable speed for durability. The 2AZ hits 20 m/sec at exactly 6250 rpm; coincidentally our base red line is at 6250. If you are willing to accept shorter service life, you can spin up to 7630 rpm for the same 24.4 m/sec mean piston speed as a Type R Integra (the highest mean piston speed of any street production engine including Honda's NSX).

The real question about raising the redline is what is in it for me if I do? There are three big questions that go along with this:
1. Does the cylinder head flow enough to support raising the redline?
2. Do the cams (and valve springs) support raising the redline?
3. Do the intake and exhaust support raising the redline?

If the ports and valves in the head will continue to flow more air without the airflow going supersonic at higher rpm, then we've answered #1.

If the cam profiles have already been maximized to work with the bottom end geometry (rod length to stroke ratio) and the valves and springs don't float or oscillate at the raised redline, we've answered #2.

If the intake (all the way from where the air goes in the opening to the cylinder head's opening) and the exhaust (from where the exhaust port meets the header to the tip of the tailpipe) support the increased flow from raising the redline, then we've answered #3.

If we have a thumbs up on all three questions, we will make more torque at higher rpm, and therefore, more power. Ideally we make the same torque from the bottom of where we want the engine to be strong, all the way to redline, although usually torque starts to drop off before we get to redline.

A turbo, or any other kind of forced induction, will try to make more air move through the same system. Raising the intake pressure is always helpful, but again, you need to have the entire intake all the way to the valve seat correctly sized and the exhaust all the way from the valve seat correctly sized to take full advantage of forced induction.

Sure, you can slap on a pressure inducing device and get more, but if you really want to see the improvements, especially at high rpm, you'll need to take the head off and make some pretty radical changes to it to let more air into the cylinder. I've done this for an NA Supra head, and the port size difference between the stock GTE head and the stock NA head is huge. Basically just think of adding 4mm diameter to the entire port on the intake side. That's a LOT in the porting business.

So, if I took off the head and added some size to the ports and probably the valves too, we'd get more flow. More flow means more power at the high end of the rpm range which is where we planned to go anyway, so it's all good, assuming the rest of the intake and exhaust are up to the task. Without modifying the ports or without changing the cam profiles, you are correct; more rpm won't get you a whole lot.

Last but not least, you also have to pick your FI device to match your desired rpm range. A big turbo (like a T-61 for our cars) will give great boost at high rpm (because it needs a lot of waste heat to drive it and we don't start making lots of waste heat until we really get the rpm up), but may not be too fun around town for stoplight racing.

Here again, we have to decide what rpm range we want to be responsive and pick our components to match that range. Too big is just as bad as too small. Lots of would-be porting guys find this out the first time they do a head. They almost always make the ports too big and the engine builder suffers as much embarrassment as the driver does.

Your question about a turbo is pretty easy to answer: no matter what, the engine will make more power under boost, but it won't fix the problems you need to solve to make more power above redline all by itself.

The thing that lobux left out is that when you raise the redline you also raise heat. Meaning that you need a better cooling system if you plan to keep it up very long. Second, you will find that the bottom end also needs to be well balanced in order to keep the engine together. The oiling system also needs to work well or things will seize up. Most small import engines are well balanced and the cooling system usually works very well. Raising the redline is dangerous thats why its there. Toyota knows what they are doing. However that doesnt stop us racers. Just know that most real race engines are torn apart ever ten runs or so. Even the good ones. Doing all this head work and changing the redline is great But keep in mind the bottom end is just as important as the top end. My friend runs a power programmer on his truck. Mostly its for changing the top speed and for changing shift points, tire sizes, ect to make it pull or race better. However it only changes these things and not the overall power. You may see small gains from changing the fuel to air ratio buts thats about it. This may be what your freind feel.

Great info lo bux

Our plan is to build a turbo system that provides an optimal low to mid/upper mid powerband with high reliability factored in. This is just for our purposes, we will drive it alot to events, autocross, drags, maybe road course track days, audio competitions, etc, etc. I have always been a fan of a wide powerband and long term reliability(as much as possible) It seems this little motor we have will do just that.

In the realm of reliability I am looking at a cast iron manifold, if done right they can produce great bottom end and flow plenty well enough for strong mid and upper midrange RPM use. And, if built well can last a very long time

As I am sure you are aware, most of us love to brag about big numbers when it comes to HP and Torque and small numbers when it comes to ET's, I am as guilty as anyone else

Unfortunately those are best relegated to racing applications. For serious street fun, smaller numbers can be acheived with a wider power band and if you make a plot that includes average time spent at each RPM point and how often you are at that point, you can have substantially more power available than a high RPM power band with bigger numbers can provide. More real world power where you need it the most and more reliable and easier to use the power as well, that is what I prefer to build and drive

My last engine project, that I abandoned due to needing to take care of my disabled buddy, was being setup to have a wide powerband but also very high rev limit. But, it was also being setup to drop boost off at super high RPMs because I really did not need alot of power there, I needed to be able to not shift so often during autocrosses on the tighter tracks. It was going to have a remote on the steering wheel to switch between two seperate tuning curves, low boost with smooth onset and drop off at high RPMs, timing and fuel mapped accordingly. Then for some fun when hooked up on the faster sections a map for more boost, come on sooner, stay on longer, to take advantage of the places where I could use more power effectively. This was going to be tuned for road course track days, higher speed autocrosses and drags, if needed.

That is past history now, this new car/engine is going to be easier to build good power with and have one tuning setup, well, we will have it programable from the touch screen of the carputer, hmmm, maybe we will have more than one tuning setup afterall, time to do more research!!!

Rick

Originally posted by kckid@Mar 22 2005, 09:03 PM
The thing that lobux left out is that when you raise the redline you also raise heat. Meaning that you need a better cooling system if you plan to keep it up very long. Second, you will find that the bottom end also needs to be well balanced in order to keep the engine together. The oiling system also needs to work well or things will seize up. Most small import engines are well balanced and the cooling system usually works very well. Raising the redline is dangerous thats why its there. Toyota knows what they are doing. However that doesnt stop us racers. Just know that most real race engines are torn apart ever ten runs or so. Even the good ones. Doing all this head work and changing the redline is great But keep in mind the bottom end is just as important as the top end. My friend runs a power programmer on his truck. Mostly its for changing the top speed and for changing shift points, tire sizes, ect to make it pull or race better. However it only changes these things and not the overall power. You may see small gains from changing the fuel to air ratio buts thats about it. This may be what your freind feel.

Click to expand...

Ummm, sure. The oiling system does not need modification unless you want to install an oil cooler because we didn't get one from the factory. High volume oil pumps are not only not needed, but they will cause seal failure in Toyota engines. Simple rule of thumb: 10psi for every 1000 rpm up to 75 psi. If you have that, you have no worries. It's been true for years.

The tC cooling system has a much greater capacity than it needs, as is typical of Toyco designs. It would be the least of my worries.

Engine balance is not a worry with any Japanese engines, the manufacturers all do a stellar job of getting this right at the factory. All their cranks are forged and rods are shot peened so that's not a worry either.

Real race engines are torn down after every event or every run depending on the level of the sport. Top Fuel and Funny Cars are rebuilt after every run. Obviously you missed my points about service life and mean piston speed.

Toyota bottom ends are legendary. The 2JZ in the Supra has made over 800 hp bone stock from the factory in daily driven cars. I have no reason to doubt the 2AZ is any different, despite it being an aluminum block. It is one of the primary reasons I choose Toyota over other makes.

Horsepower is in the head. Longevity is in the bottom end. Been that way as long as I can remember, and not likely to change any time soon.

Damn isnt there a dealership that can sponsor lo bux with a tC. So he could make a turbo for us, the daily drivers. All i need is 100-150 hp at the wheels, and the car to last more then 100,000 K miles. :>

I mean 100-150 more. I'd be happy with a 240-280 hpw turbocharged.