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QWKSNKE
09-15-2005, 08:56 PM
Well as mentioned in the other thread my driveability is getting a lot better. Been data logging and making MAF changes based off EA a good bit over the last 2 weeks.

The bucking seems to be coming from decelaration. Is this still due to the out of whack MAF curve or I am missing something else?

Disney Lincoln
09-16-2005, 01:26 AM
I would guess it's from the Dashpot decay rate.

QWKSNKE
09-16-2005, 07:01 AM
I would guess it's from the Dashpot decay rate.


tell me more

86GT
09-16-2005, 12:27 PM
It could also come from the spark tables. Look at FN125 to see where the tables switch over. Then look in the spark tables and make sure the transition between the tables is smooth. If the spark jusps or dips drastically it will cause all kinds of bucking.

This took me forever to find.

Disney Lincoln
09-16-2005, 02:18 PM
I couldn't start to talk about the Dashpot decay and preposistion functions..... I don't understand them well enough to offer tuning advise for them. I just spent a few hours one night going through the Yahoo group and the optlink board reading posts from people smarter than I.

Clint.... care to fill him in?

QWKSNKE
09-16-2005, 02:45 PM
One key note.....

I never had this problem when the car was tuned with the 42's and 42# univer. Only since I swapped to the 60's and the 55# univer have I started experiencing these problems.

Disney Lincoln
09-16-2005, 04:00 PM
Then, that would point to a MAF adjustment...

On the dashpot decay I just went in and made the values smaller. Car quit surging. I messed with the preposistion also, but that didn't help me any. The decay rate was noticable.

86GT
09-16-2005, 04:34 PM
I personally have not played with the decay or preposition yet. I due have a slight bucking, but I think it is due to my spark tables since that was the last thing I messed with.

If the only thing that you changed was the MAF and slopes, then I agree the MAF must be the problem.

93Cobra#2771
09-19-2005, 09:32 AM
If it makes you feel better, I still have slight decel bucking issues. I REALLY need to do a little more tuning...

86GT
09-19-2005, 11:09 AM
I put my spark table back to stock and the problem went away. I am going to do some testing to find out what caused it.

93Cobra#2771
09-19-2005, 11:13 AM
My spark tables are all stock - has always had the issue since day one. It got A LOT better after I dinked around with the ProM transfer curve, but still hasn't been totally fixed.

I have simply been too lazy/busy to do any more tuning on it. I have some ideas on what to try, though. :D

QWKSNKE
09-27-2005, 08:09 PM
I put my spark table back to stock and the problem went away. I am going to do some testing to find out what caused it.

Any updates?

It is very annoying. I believe my timing tables are still stock unless the file has gotten corrupted.

86GT
09-27-2005, 10:23 PM
My Spark tables are what caused mine. I also left my accel tables alone but raised the global accel multiplier to 1.2.

My bucking is gone but I do have a tad lean tip in. I have 90GT's tune and I am trying to figure out what he did.

93Cobra#2771
09-28-2005, 10:39 AM
My timing tables are from an A9L - made no difference, bucked the same...

86GT
09-28-2005, 12:55 PM
I only saw the bucking when I changed the spark tables in the mid range and they did not match one another.

These tables are inter twined depending on load. This is hard to put into words but the EEC uses three different tables depending on FN125. If your load is hovering at this cross over point, defined by FN125, and the two tables that are drastically different at this point then the bucking will occur.

I hope that makes sense.

I used the X3Z spark tables and then only messed with the loads above 100%

Italian LX
09-28-2005, 12:58 PM
I only saw the bucking when I changed the spark tables in the mid range and they did not match one another.

These tables are inter twined depending on load. This is hard to put into words but the EEC uses three different tables depending on FN125. If your load is hovering at this cross over point, defined by FN125, and the two tables that are drastically different at this point then the bucking will occur.

I hope that makes sense.

I used the X3Z spark tables and then only messed with the loads above 100%
I remember checking the three spark tables you are refering to and thety are all at the stock settings on Lee's tune.

86GT
09-28-2005, 02:15 PM
Chances are the spark is not the issue. If I remember correctley you stated the only difference was the MAF and injectors. If this is still true then it has to be the MAF.

What is spark, fuel, MAFV and TP at the bucking range?

QWKSNKE
09-28-2005, 03:04 PM
Do you think that I may have a bad MAF.

Italian will have to answer your question Clint. He currently has my car and laptop so I can't look it up

Italian LX
09-28-2005, 03:12 PM
Do you think that I may have a bad MAF.

Italian will have to answer your question Clint. He currently has my car and laptop so I can't look it up
Yeah, I've been offline typing up a response. ;)

Italian LX
09-28-2005, 03:14 PM
What is spark, fuel, MAFV and TP at the bucking range?
Let’s see if I can give some more information on the problem…. maybe some of this will enlighten other on what is going on.

One thing that happens in addition to the bucking is a weird surge while increasing the engine speed (while the car isn’t moving). I’m thinking this is directly related to what’s causing the bucking while the car is cruising, so I will explain what I have experienced:

The car idles great at around 900RPM. However, if you run the motor up to 1500 it will start a surge that runs up and down a few hundred RPM at about 100 cycles per second. The datalog shows the MAF voltage bouncing back and forth over about a .3 volt range and the pulse widths bounce between .8 and 1.8ms. Also, the timing is up around 37.5 to 42.75* during the surging. It seems to me like something is causing a slight surge and then it starts a cycle.

Jonathan and I had both mentioned that maybe the BOV may be not opening properly and is causing some surging across the MAF that starts the cycle.


As far as the rest of the tune goes, the car feels really good under acceleration and we now have the KAMRF’s staying relatively close to 1.000. There seems to be no bucking as long as the vacuum is below 14 in-hg… but anything above that and you’re very prone to a bumpy ride. :huh:

Wall96cobra
09-28-2005, 03:26 PM
Jonathan and I had both mentioned that maybe the BOV may be not opening properly and is causing some surging across the MAF that starts the cycle.


As far as the rest of the tune goes, the car feels really good under acceleration and we now have the KAMRF’s staying relatively close to 1.000. There seems to be no bucking as long as the vacuum is below 14 in-hg… but anything above that and you’re very prone to a bumpy ride. :huh:


Yeah I'm still leaning towards the blowoff valve, that mondo vlave was set very loose and I believe the pre-load spring was even cut. The min race BOV is smaller plus probably set tighter so he may need to adjust it and add my old bosch bypass valve to it. It really sounds like a BOV problem to me, my car used to buck and surge before I added a second BOV although in the end I was able to run just one but I had to cut the pre-load spring in the BOV and set it very loose...and even then there was a slight buck but nothing too noticable.

86GT
09-28-2005, 03:48 PM
Try two things:

1) Try unpluging the spout to remove EEC spark control.
2) The BOV is what I was going to suggest too. Disconnect and plug the vacuum to the BOV and see what happens. Is this an adjusable BOV? Draw Thru? If it is one of the typical Bosch Bypass valves then make sure it is installed in the right direction. I had Powerdyne tell me that it did not matter which direction it was installed. That is not the case. If you have positive pressure fighting the return spring on the Bypass valve then it will take a lot more vacuum to open it.

Wall96cobra
09-28-2005, 04:03 PM
It's a blowthru setup and the BOV is a vortech mini-race which is adjustable. I was gonna let him try my bosch bypass valve in there with the mini-race, it doesn't take much vacuum at all to open the bosch and with the intercooler that is a large volume of air to try to bypass with just one BOV

86GT
09-28-2005, 04:16 PM
If adjustable, then it should be set to 2-5 psi above the idle vacuum. If the BOV is prior to the MAF then just vent it. If it is after then it must be re-routed to the intake.

Pictures???????

Italian LX
09-28-2005, 04:19 PM
If the BOV is prior to the MAF then just vent it.
It is vebt to atmosphere. :nice:

Italian LX
09-28-2005, 04:19 PM
Pictures???????


:shrug:



http://myweb.cableone.net/blombardi/ifotfd.gif



:D

QWKSNKE
09-28-2005, 06:46 PM
:slap:

QWKSNKE
09-28-2005, 06:48 PM
If adjustable, then it should be set to 2-5 psi above the idle vacuum. If the BOV is prior to the MAF then just vent it. If it is after then it must be re-routed to the intake.

Pictures???????

what do you want pics of?

86GT
09-28-2005, 10:02 PM
I was refering to the MAF and BOV setup.

86GT
09-28-2005, 10:06 PM
:shrug:



http://myweb.cableone.net/blombardi/ifotfd.gif



:D

:rofl:

fireguy50
09-29-2005, 12:10 AM
These tables are inter twined depending on load. This is hard to put into words but the EEC uses three different tables depending on FN125. If your load is hovering at this cross over point, defined by FN125, and the two tables that are drastically different at this point then the bucking will occur.
http://fordfuelinjection.com/images/FN125.gif

93Cobra#2771
09-29-2005, 07:54 AM
Welcome to the board, Ryan!

86GT
09-29-2005, 08:33 AM
http://fordfuelinjection.com/images/FN125.gif
Thats it. Thanks Ryan

fireguy50
09-29-2005, 10:16 AM
Personally, I changed FN125 to make FN901 a dead table.

Dale McPeters
09-29-2005, 10:47 AM
Personally, I changed FN125 to make FN901 a dead table.

Ryan,

I have also been doing this for the past week just to see how it was going to work. And so far seems to be working a lot better this way in my application.
Will know more by next week.