FUEL TRIM

[babybenz]

All,
In "Fuel Trim" tab, if "Overall fuel trim" shows "-10%" and "Throttle tip in trim" shows "-30%", what does this mean?

Does it mean the fuel in these two fields will be LOWERED BY 10% and 30% respectively compared to the main fuel map?

[crucian]

All,
In "Fuel Trim" tab, if "Overall fuel trim" shows "-10%" and "Throttle tip in trim" shows "-30%", what does this mean?

Does it mean the fuel in these two fields will be LOWERED BY 10% and 30% respectively compared to the main fuel map?

Yes. If you have not already started tuning everything, set your overall fuel trim back to 0% and then tune. If it was tuned that way, leave it alone.

[babybenz]

Yes. If you have not already started tuning everything, set your overall fuel trim back to 0% and then tune. If it was tuned that way, leave it alone.[/quote]

crucian,
Sometimes, I can feel the car "jerk" (as in car hesitated) when i throttle in or lift off throttle.

Maybe the map is too lean and hence the hesitation. I have changed the two parameters to "0" but yet to try out the difference.

Btw, what is "Throttle tip in trim"? Is it the amount of fuel to be added/reduced when throttle in?

[crucian]

Yes. If you have not already started tuning everything, set your overall fuel trim back to 0% and then tune. If it was tuned that way, leave it alone.

crucian,
Sometimes, I can feel the car "jerk" (as in car hesitated) when i throttle in or lift off throttle.

Maybe the map is too lean and hence the hesitation. I have changed the two parameters to "0" but yet to try out the difference.

Btw, what is "Throttle tip in trim"? Is it the amount of fuel to be added/reduced when throttle in?[/quote]First off, we would need to know how hard you're stepping on the throttle when you experience your jerk/hesitation. What you need to do is a datalog and review where the hesitation is coming in. That's the only way to fix it. There is no guessing or maybes.

*throttle tip in adjustment is for when you suddenly step on the throttle all the way. Once again you have to datalog to see what changes need to be made. Most of the cars I've tuned wants the "throttle tip in" to be deep in the negatives. But every setup is different.

*once again with the overall fuel trim, if your car was tuned on a specific number put it back to that number.

[babybenz]

Crucian,
Today, I changed the overall fuel trim to "0" and throttle tip-in also to "0". Results were worse.

So, I revert to the original map. Instead, I increased the fuel map by three "clicks" and drove the car. It seems to be better. I will try again tomorrow.

I will also datalog and post it here.

Thanks for your help!

[babybenz]

Crucian and all,
Here is the datalog using the original map. It was tuned very well for several months but somehow the map has "run" after the idle valve was cleaned.

I have a wideband sensor in the car. I notice that at certain low load and rpm, the afr at certain cells showed 10+ to 12+ which is too rich.

Pls help me to check and let me know which "areas" have gone wrong.

Thanks to all... :-)

[crucian]

Crucian and all,
Here is the datalog using the original map. It was tuned very well for several months but somehow the map has "run" after the idle valve was cleaned.

I have a wideband sensor in the car. I notice that at certain low load and rpm, the afr at certain cells showed 10+ to 12+ which is too rich.

Pls help me to check and let me know which "areas" have gone wrong.

Thanks to all... :-)

I would need your tune sent to me to see what was done to it.

[babybenz]

crucian,
The behaviour of the car today is the worst so far! Pls see the datalog.

I contacted my mechanic who came to check on my car. He popped the bonnet and touched some sockets. Then he brought it for a spin.

Surprisingly, all the problems I stated earlier "disappeared". He suspected it was becos of some sockets (with wirings) that became loose due to the extra-stiff engine mountings - vibrations!

I will continue to monitor the car and keep all posted.

Thanks alot for paying attention to this thread.

[crucian]

That's good that you've located the possible problem.

[Johnny_9]

Did he used diaelectric grease - Shop manual recommends it. Never seen a machanic use it...

[babybenz]

Did he used diaelectric grease - Shop manual recommends it. Never seen a machanic use it...

Johnny,
I have no idea what that grease is. Anyway, car is so far so good thanks to my mechanic's magic touch... :-)

[ali hussain]

hey friends i have changed my fuel injectors late from 240 cc and replaced them by s2000 injectors with 550 cc so do i need to change anything like the overall fuel trim or crancking fuel trim or throttle tip in trim and what about the post start fuel adjustment please friends i need some help under this tab so could anyone help me??
if you can help me with any websites or anyone who can be in a direct contact with him i will be thankful to u all

[crucian]

hey friends i have changed my fuel injectors late from 240 cc and replaced them by s2000 injectors with 550 cc so do i need to change anything like the overall fuel trim or crancking fuel trim or throttle tip in trim and what about the post start fuel adjustment please friends i need some help under this tab so could anyone help me??
if you can help me with any websites or anyone who can be in a direct contact with him i will be thankful to u all

Well personally I think you would need a complete re-tune. I guess the answer to your question would be, Yes you have to change it all.

[ali hussain]

well thanks first of all
but i dont have enough experience in tuning and specially under this tab (fuel trim) so can you help me please like to how much should i set these numbers after changing 240 cc injectors to 550 cc injectors and in your opinion what would be the best value for the overall fuel trim and the crancking fuel trim and throttle tip in trim?? and what about post start fuel adjustment can you help me please!! and if you can explain it to me or a website by which i can get what i want? i would be thankfull to you bro

[babybenz]

I would need your tune sent to me to see what was done to it.

crucian,
Here is the map the car is on. This evening when driving off, the sudden "lean" problem happened again. Wideband AFR showed "---" and rpm suddenly dropped very low. Then suddenly jumped up to normal again. Strange...