Hello. Im in the process of tuning my car and I'm just curious as to why on some points of the fuel map, fuel values drop slightly and pick back up?
Wouldn't we want fuel values to steadily increase as we go into higher rpm due to the increasing airflow of the engine?


Don't mind the highlighted boxes.. those aren't the points im speaking of. I'm talking about in general as the RPM increase at some points of the map fuel drops and pick back up.

Also is anyone else having problems with crome? It is giving me a message saying "This version of crome has expired. Please download the newer version" and just closes on me. I have the latest version. Checked the site, no update.

 

Volumetric efficiency

 

Here is a basic breakdown.

If you look across the tables at lets say 5000 rpm, as airflow increases, fuel values with increase with it.

If you look down the columns at say 3.8 pounds of boost pressure as RPM increases fuel values increase because volumetric efficiency is increasing. As rpm increases to a certain point fuel values drop because the engine has reached its max volumetric efficiency and is starting to decrease. Although air pressure stays the same VE decreases due to valves opening and closing faster giving less time for air to move into the engine at a certain air pressure. This is why bigger cams allow you to make more power up top.

When tuning a car position of the table never moves straight across or straight down. It moves at a downwards slope towards the bottom right.

 

That's not an VE (volumetric efficiency) problem. That's just a not-so-tidy fuel map, VE looks like this:



When in torque peak, we need more fuel to achieve a correct A/F ratio. In this case, 4000-5000 RPM is where most torque is developed by the engine.


That little VE table holes are simply untidy fuel points, that probably are not tuned correctly.

 

You'll find a well tuned fuel map (at WOT) will represent the torque curve (VE).

 

Yeah i didnt wana touch on how bad the map looked

Just a fact of why less fuel after peak ve

 

You need to either start from scratch with that map or interpolate, rescale, and restart. You are approaching the more time than it's worth threshold and are probably already chasing your tail in that tune. If you are adjusting that much all over the place, you either have a mechanical problem or your base map wasn't set up very well.

As far as CROME goes, get used to it. Just revert your computers clock back a few months.

 

The graph i just posted was actually done by another tuner. I was trying to study the graph to get an idea of how it works before attempting to tune my car.

Theres another thing i noticed about the timing maps that i don't fully understand. The cars timing map for the secondary ignition is set to the same number for every column. Is there a reason why a tuner would do this? This is a reputable tuner who has been tuning hondas for over 10 years so i trust his judgement. Just wondering why he would do this?

 

i hope you didn't pay too much for that tune.

How long was the car on the dyno? i assume the most an hour?

Fix that random 3

judging by that you're tuned to 15-16 psi? max

 

I think you didn't get a good tuning job. Timing is the most powerful tool to develop horsepower and protect the engine. Timing needs study, and development that are two things that i'm not viewing there. On WOT there is no problem, tuning probably works great, but on cruise/low load that's not good at all. For example: On torque zone you need to pull some degrees (Because when in torque peak engine needs less timing to achieve MBT).