Adjusting Exhaust Timing: Will Need Some Help

[Ladogaboy]

Okay, so here's the deal. A few people have been asking questions recently about the effects of adjusting exhaust timing. I have the hardware/software necessary to make those changes on my car, and will start posting results as I am able. I could use a little help in terms of making adjustments and areas of focus, so please feel free to chime in. I wanted to post this up right now, but I will follow up with some graphics of what the exhaust timing profiles look like for my car.

To start with, the following are the stock exhaust timing profiles:

Cam #1



Cam #2

[oil pan 4]

You have to watch out because exhaust tuning usually yealds the least results in terms of fuel economy unless you are working on a diesel then the gains are just small.

The closing of the intake valve has the greatest impact on engine preformance of the 4 open/close events of the intake and exhaust valves.

Messing with the intake cam may produce better results.

If you have the stock timing gears there isn't much you can do besides skip the belt by 1 tooth on the exhaust side towards the direction you need for retarding it. That should be good for about 4 degrees.
I did this with my little 1.8L toyota I had when I was over in japan years ago, but I advanced the intake timing by 1 tooth.

[Ladogaboy]

Okay, so I just downloaded my current exhaust timing map, and it seems that the first cam is for normal coolant range, and the second cam is for low coolant range. There's quite a big difference between my current maps and what is listed as stock.

Cam #1:



Cam #2:



Now the question is where to start. Most of my driving is in the 2,500 to 3,500 rpm range at 40-70% load, and I'm really looking to focus primarily on my highway mileage (3,000-3,500 rpm and ~60% load).

[Ladogaboy]

Originally Posted by oil pan 4

You have to watch out because exhaust tuning usually yealds the least results in terms of fuel economy unless you are working on a diesel then the gains are just small.

The closing of the intake valve has the greatest impact on engine preformance of the 4 open/close events of the intake and exhaust valves.

Messing with the intake cam may produce better results.

If you have the stock timing gears there isn't much you can do besides skip the belt by 1 tooth on the exhaust side towards the direction you need for retarding it. That should be good for about 4 degrees.
I did this with my little 1.8L toyota I had when I was over in japan years ago, but I advanced the intake timing by 1 tooth.

Well, the thing is, I have control over both the intake and exhaust timing, but I want to focus on and track the results of the modifications separately. I won't have to do anything mechanical since the timing for both is adjustable through the ECU.

[mwebb]

those #s do not really mean much

you are going to need EVO and EVC values and IVO and IVC values , you can calculate them if you know exhaust valve open duration in degrees -
you do not want the exhaust valve closing too soon as if it does it will not allow all of the spent combustion gases to escape ... prior to the next combustion event .

you will be adding EGR , intentionally , EGR is good , HOT EGR is not as good as cooled EGR , with regard to FE .

something that plagues those who just dial in cam advance on single cam engines .
most users who tamper with cam timing have no clue why results are so terrible
the engineers really did already provide very close to the optimum map.

you will really need to plot real time pressure / vacuum in the combustion chamber , or use the data from someone else who has this stuff .

case in point
inside the red oval see pressure spike in the combustion chamber due to advanced cam timing , and above with stock OEM cam timing , combustion chamber pressure is represented by the green traces , follow the labels in the balloons for descriptions .

in that application , 10 degrees of cam advance caused the engine to run poorly with no power and no improvement in fuel economy .

here is a Honda civic
with a advanced cam due to jumped timing belt , same issue is present

i have overlayed pressure waveforms , good and bad using AESannowave software , to show the effect i described above

that pressure spike at about 350 degrees is caused by trapped exhaust gases that cannot be vented to the exhaust , they will displace incoming air fuel mixture and effectively reduce the size of the combustion chamber , which describes what EGR does .

if that is what your goal is ... carry on .

[drmiller100]

I THINK what you have posted are two different maps for the same cam? One is low coolant temperature (cold engine) the other for when the engine warms up????

In general, retard the exhaust cam at low rpm. You are keeping the exhaust valves closed longer for every bit of power.
As you rev the engine up at higher rpm's you open the exhaust cams sooner.

[spacetiger]

Keep posting updates, this thread looks interesting.

BTW, what car/truck/suv are you driving?

Also, what tool are you using to map out the timing with? And how can you change the map of the ignition timing (with the tool?).

Jerry

[Ladogaboy]

Okay, I apologize for getting back to this sooner. Just for background information, I've been using a Tactrix OBD-2 with the ECUFlash interface:

Tactrix

I might just create a thread with an overview of everything that I'm doing and then create separate threads each of the specific changes and their results. The one thing that will probably need to take precedence over most of the engine tuning is aerodynamics. I've found that this engine is extremely efficient when at low loads, but getting to those low-load levels at highway speed is going to require some adjustments. Anyway, more on that later!