Coolant temperature compensation | Fuel | Cranking fuel

[typer86]

Hi Hondata,

sorry for so many questions but I could not find in the documentation the logic to understand the feature correctly.

In our car (supercharged FN2 with AFM 750cc cal) in different cases the engine is starting hard but not always. So I checked your Tuning Starting Fuel guideline few month ago. But I must rolle up again this part....

The tuner provides only the basic calibration with the cranking fuel + Coolant temperature compensation + Fuel from the starting forced induction RSP calibration (310cc).

Engine start conditions:
> cold: OK
> hot: OK
> warm (car is off for approx. 60-30 minutes): not OK (approx. temperature range: 30C° - 60C°)

With your guideline it is good to tune the "Coolant temperature compensation" on the "Fuel" side. But I could not understand the following settings and their dependency's.

Fuel > Cranking fuel

start_fuel_2.PNG (6.81 KiB) Viewed 7258 times

Fuel > Coolant temperature compensation

start_fuel_3.PNG (18.04 KiB) Viewed 7258 times

Fuel > IAT (Air temperature compensation)

start_fuel_1.PNG (14.84 KiB) Viewed 7258 times

I will test today the configuration from your basic RC750cc MAP cal may it helps... But if not it would be nice if you could explain the Cranking fuel and their values and the other listed settings.

PS: I hope in few years I am an expert with the Hondata and I will answer questions :) lol

Edit:
Short test with the imported settings from the Civic-Si-Race-8-RC750 works fine. At the moment I tested the cold and hot conditions.
... The warm part will be interesting... I keep u up to date

[Hondata]

The table that affects the injector duration for a warm start is the 'Water temperature fuel compensation cranking'. You would need to datalog and see what the ECT is when you are starting the engine. From their try
However, a warm start problem is often from fuel vapor locks in the fuel rail. I'd do some experimentation opening the hood to cool off the engine and see if that makes any difference first.
Also, where is your IAT located? Does it accurately read intake temperatures?

[typer86]

In the attachment you find the described scenario.

I don't know where the IAT sensor is located. I think stock?!

Before starting the IAT reads 56°C (132°F) at the moment we have here in Germany hot summer days with temperatures of over 35°C (95°F) air temp.
May the IAT is the problem?

datalog0000.1.24.5-cranking.fpdl

(33.09 KiB) Downloaded 213 times

R-22837_MAF_Rotrex_FN2_v1.24a.fpcal

(16.43 KiB) Downloaded 192 times

[Hondata]

IAT of 56C is normal on a hot day.
The cranking injector durations looks ok for 750cc injectors.
I think it is a fuel vapor problem. Try opening the hood for 5 minutes before a warm start and see if that makes any difference.

[typer86]

Hi hondata,

Today I tested the starting issue with open the hood for 5 minutes before starting the engine.
Feeled a little bit better starting. So I think you're right the car have a vapor lock.

I Googled for possible solutions but I could not find anything for me.
... What is the "Fuel return line" may this cause the problem?

If you have any idea to fix this issue I am very happy.

[Hondata]

I'm not sure. I've not seen vapor locks as a problem on any Hondas recently. While they used to be common with carburetor engines, the higher fuel pressure for fuel injection pretty much fixed that problem.
It could be that the fuel is not quite right and changing the fuel temperature is enough to flood or starve the engine.
I would reduce overall cranking fuel about 10% and see if the problem is any better. If not, change it the other way. If you find hot starting is better with more or less fuel then you can change the ECT and/or IAT cranking tables.

[typer86]

Hi Hondata,

I tryed new settings (10%) leaner.
First testresult looks good but I will test few days if all conditions are fixed with the new setup.

I edit the "coolant temperature coolant" section
> fuel compensation low
> fuel compensation high
> fuel compensation cranking (10%) leaner in temps: 22 - 62C°

We will see next days if fixed.

Thanks again for you input and great support!

[typer86]

Hi Hondata,

In the attachment (uploaded on: File-Upload.net) I have created a little excel sheet to tune easily new parameters.

Unfortunately the tested parameters does not fix my issue... More tests are required to find out the correct startup values.

Coolant temperature compensation spread sheet:
Tuning_Fuel_Cranking_sheet.xls

[typer86]

Test: #1: 5% richer

Please watch the video from the starting.
Also you find the attached cal + datalog

R-22837_MAF_Rotrex_FN2_v1.34a.fpcal

(16.49 KiB) Downloaded 215 times

datalog0000.1.34a.2.fpdl

(2.78 MiB) Downloaded 232 times

(Audio is a little bit too quiet...)
https://youtu.be/p4uzLifR2cw

Test: #2: 10% richer
... To continue

[typer86]

Few tests again I could not resolve the issue...
If the car is to rich it's starts very hard... 10% richer was badly...
Result with 10% the engine starter need 3 sec until the car starts...
At the moment I am on 6% leaner and its a little bit better...

At the moment: (I must test)
I think 4% leaner is the best middle for this situation.

It is very strange issue because it is very hard to identify it. All looks like that the heat can not escape from whatever.
Or the Rc injectors go crazy if the gas is heated up but the water is warm only.

I will re-test the situation with open hood for 5 minutes before starting the engine.

If anybody have tips for me to fix this issue I am very happy.