poping/coughing hard shift upper KPA/RPM please help

71jeep · Post by **71jeep** » Sun Jul 30, 2006 2:04 pm

MSNS-E 029Q2 V3 Megatune 2.25 Fuel only
Hi all ..

I am still having a backfire/coughing problem at high rpm kpa but I think I am on to something but need suggestions.
First let me get you up to speed.I redid the entire fuel system new injectors fuel filters ect.This made a big difference in the idle and mid range but did nohting for the pop/cough when I am really romping on it up a hill .I do not see my injector duty cycle hiting anymore than 93% seems to be normal and the motor seems to be very rich and it is still doing it.
It is now doing it when the motor drops hard off of a down shift when pulling hard.
I made it much better almost got rid of it one small cough by increasing the decel to 125 and turning decel off ubove kpa 90 with no ego on.
What essentially am I doing by doing this?
When I turned ego back on it went right back to what it was doing even worse.
If anyone can help me it would be greatly appreciated this is getting to be a real thorn in my side.

Thankyou 71jeep

71jeep · Post by **71jeep** » Mon Jul 31, 2006 8:19 am

Reading the manual I know that decel pulls fuel from the engine when you drop the throttle but am a bit confused as to what happens when I make the number bigger than 100 am I on the right track to fixing this problem or masking another.
The motor is pulling 95kpa at 3300 rpm and when it drops out of passing gear into drive it drops to 85-90 at 2100 and right after coughs and pops.It has very steep set of gears.
If anyone help please.
Anyone please
Thankyou 71jeep

71jeep · Post by **71jeep** » Mon Jul 31, 2006 6:57 pm

Could someone point me to some reading material to help me out?

Thankyou 71jeep

71jeep · Post by **71jeep** » Tue Aug 01, 2006 1:09 pm

I checked the timing it is right on the motor has a new set of lifters and heads.My wideband is telling me I am extremly rich and the motor is sluggish but strong like it is rich but it still wants to pop and cough through the intake when it down shifts.
I have tried number in the VE 20-30 percent higher with no change.
I know that poping through the intake is a sign that it is lean so it is going lean on the sudden change when it shifts why ?Is it decel causing it ?
One thing I have noticed with the decel ubove 100 is it takes much longer for the AFR to stablize when you go from a high Kpa to a low kpa is there a way to change this?
Can anyone give me a suggestion or something I missed in the megamanual please I have this last hurtle to overcome and am not sure what to do.

Thankyou 71jeep

JNygard · Post by **JNygard** » Tue Aug 01, 2006 2:32 pm

It's not decel causing the problem if its popping when it pulling higher rpms to shift. You need to make that portion of the ve table much richer. Add 10 to those upper rpm values and try again. You want that pretty rich like 13:1.

I run my decel at 90. If megasquirt can even handle numbers over 100%, depending on how it was written in the program, that would mean you are adding fuel on decel.

71jeep · Post by **71jeep** » Tue Aug 01, 2006 2:49 pm

Its poping on the sharp rpm drop from passing gear to drive I just checked one of my datalogs I am at 3100-3200 rpm and when it shfts it rapidly drops to 2100 to 2200 and then a few seconds later it will pop.
And I was wrong the kpa it does not drop into the till after it pops it stays up in the low 90s.

Thankyou 71jeep

JNygard · Post by **JNygard** » Tue Aug 01, 2006 2:56 pm

Ok then try fattening up the ve table around 90 and 2200rpm level. Then when it settles back to cruising portion of the map of 70's and 2200rpm that should be about 16:0 to 1 ratio or what ever you decide for economy.

71jeep · Post by **71jeep** » Tue Aug 01, 2006 3:09 pm

I will give that a try and see if it helps thankyou very much for the idea.
I am running out of things to try Lance and chicksdigwagons thought maybe my fuel system was the culprit at first and it may well have been I found a cloged up fuel filter but with all the new goodies I put on I had to lean out alot of the table because it is working so well.
And now it is pegging the wideband at 10AFR and holding it there it never did that before but I am still getting this darn pop.

Thankyou again 71jeep

maztah · Post by **maztah** » Fri Aug 04, 2006 5:37 am

i also had this similar problem of lean mixture at 90+kpa, the VE table got odd values when it reaches above 80kpa. right now i am suspecting my throttle body bore diameter is oversized, 1.3L engine with 76mm diameter. i got rid a little of the problem when i noticed the fuel pump is not getting enough supply and tried to hook it directly to the battery. It somewhat improved though it is still very consumptious. the mechanic diregarded the fact that the fuel filter might be blocked since its new. How can you tell if its blocked? and how can you easy tell if there's a problem in the supply without doing fuel presure check?

71jeep · Post by **71jeep** » Sat Aug 05, 2006 10:28 am

Maztah..

The best way would be to do a fuel pressure check to be sure if you have a problem with fuel pressure.
Or just pull the fuel filter and replace it like I did it is cheap insurance to know that it is just not a fuel filter.
I hope to get back to problem this weekend and give a few thing a try and see if they help I will update the thread with what I find.

Thanks 71jeep