what causes bogging when pushing at low rpm?
06-01-2011, 10:19 AM
#1
6th Gear Member
Thread Starter
Join Date: Oct 2006
Location: Cork, Ireland
Posts: 6,417
what causes bogging when pushing at low rpm?
Hi all,
carb/ignition set and I'm quite happy with the results. makes plenty of power at 3000+
when warm I have no lean bogs driving off a light (no matter if slow or fast). no holes when shifting etc
the only weird problem I see is when I drive down a steep hill in 1st gear no gas. lets say you want to keep the car driving at around walking speed down the hill.
the same thing seems to happen when I shift down to deccellerate for a traffic light. as soon as the rpms drop below 1000 it happens as well.
the car seems to bog. as in me moving forward and backward in my seat.
it's quite similar to first time ever driving a motorcycle in 1st gear. too little gas, too much gas, too little gas too much gas. just not as extreme
I have no idea what could happen. maybe ignition too far advanced so it fires against piston?) lean or rich condition?
Last time I checked I believe I drive with 16 initial, but am not using vacuum advance (locked out). so if that's the case I can't believe its too much timing thre
i don't seem to have that problem going up a hill (load). i can creap up a hill in 2nd gear close to idle.
anyone know where this comes from?
carb/ignition set and I'm quite happy with the results. makes plenty of power at 3000+
when warm I have no lean bogs driving off a light (no matter if slow or fast). no holes when shifting etc
the only weird problem I see is when I drive down a steep hill in 1st gear no gas. lets say you want to keep the car driving at around walking speed down the hill.
the same thing seems to happen when I shift down to deccellerate for a traffic light. as soon as the rpms drop below 1000 it happens as well.
the car seems to bog. as in me moving forward and backward in my seat.
it's quite similar to first time ever driving a motorcycle in 1st gear. too little gas, too much gas, too little gas too much gas. just not as extreme
I have no idea what could happen. maybe ignition too far advanced so it fires against piston?) lean or rich condition?
Last time I checked I believe I drive with 16 initial, but am not using vacuum advance (locked out). so if that's the case I can't believe its too much timing thre
i don't seem to have that problem going up a hill (load). i can creap up a hill in 2nd gear close to idle.
anyone know where this comes from?
06-01-2011, 02:47 PM
#5
6th Gear Member
Thread Starter
Join Date: Oct 2006
Location: Cork, Ireland
Posts: 6,417
i just checked again and I had it hooked to ported vacuum with least advance setting on vacuum. I am going to lock it out (which shouldn't be really a difference with throttle plate close going down a hill), then I try manifold vacuum. I'll see from there then if it's worse or better
06-01-2011, 04:17 PM
#6
4th Gear Member
Join Date: Apr 2010
Location: NJ
Posts: 1,027
New cars have a much more efficient oiling system and can safely run the rpms lower. Older vehicles have to have a little more rpm so that the complete system gets oil. The pumps aren't as good, the tolerances are not as close, oiling to different parts is not as good, like rocker arms, or lifters. Older engines just need a few more rpm to have the system work correctly.
http://stores.precisionoilpumps.com/...%2C/Detail.bok
06-01-2011, 09:05 PM
#7
6th Gear Member
Join Date: Jan 2007
Location: AR
Posts: 5,469
My initial thought was not enough timing coming off idle.
I think your plan to come off of ported vac and on to "manifold vac" may help.
Your oiling issue can be addressed with a Henry A. Dobbins Lubrifiner Accelerator device.
I think your plan to come off of ported vac and on to "manifold vac" may help.
Your oiling issue can be addressed with a Henry A. Dobbins Lubrifiner Accelerator device.
06-01-2011, 09:23 PM
#8
Moderator
Join Date: Dec 2005
Location: Hills of California
Posts: 5,208
I make 40psi at 700 rpm 75psi above 2000 attempting to run the engine with the valve cover off results in oil all over everything its rad... it may not be efficient but it sure is overkill ....Awesome!!!
06-01-2011, 10:01 PM
#9
2nd Gear Member
Join Date: Dec 2005
Location: MO
Posts: 439
It sounds like your vacuum advance might not be working properly. If it's bogging as in no power, you probably need more advance, and the ported vacuum might be the wrong spot (try the manifold). If it's bucking, it might have too much advance.
06-02-2011, 04:23 AM
#10
6th Gear Member
Thread Starter
Join Date: Oct 2006
Location: Cork, Ireland
Posts: 6,417
i'll see the difference when driving back from work today. i disabled the vacuunm advance but I think I wasn't clear in my description (bogging vs bucking). I'm not native english, so that makes it worse.
at the time it happens I want no power
the foot is fully off the throttle
i'm either decellerating towards junktion or traffic light and the engine gets in the lower rpms
or i'm driving down a hill motorbreaking in 1st gear (steep hill. only for 200 metres to get to the main road). I usually end up idling in neutral down there and using the footbreak to avoid the problme.
what it feels like is if I would run over randomly placed pilons. or if someone would kick the front of my car at random intervals
I rather think too much timing could cause that.
Kalli
at the time it happens I want no power
the foot is fully off the throttle
i'm either decellerating towards junktion or traffic light and the engine gets in the lower rpms
or i'm driving down a hill motorbreaking in 1st gear (steep hill. only for 200 metres to get to the main road). I usually end up idling in neutral down there and using the footbreak to avoid the problme.
what it feels like is if I would run over randomly placed pilons. or if someone would kick the front of my car at random intervals
I rather think too much timing could cause that.
Kalli