| Author |
Message |
priss
Samba Member
Joined: May 06, 2010
Posts: 348
Location: bradford MA
|
 Posted: Thu Oct 27, 2011 5:06 pm Post subject: octane curiosity |
 |
|
1699 singleport
Dual Kads
Hemi cut stock heads
Engle 100
Stock exhaust
UNknown compression
I was just wondering about a engine symptom i noticed recently. I have had a bit of a run on problem (deiseling) with this engine from the begining. I shut off the key and it chugs a couple times before shutting off. I use the regular gas, 89
I had to buy gas while on a trip recently and my friend filled the tank with super 93. We continued on about another 30 minutes and when i shut off the car it didnt deisel at all. I have tested it with 2 tanks since altering between 91 and 89 and it is definetly the good gas that is not deiseling.
So the question is. Is there something i should be concerend about? Is there an adjustment i can make? It seems to me that if its so close to right that a couple points of octane can change the condition that there must be something easy to alter to make her shut off on 89 the same as she does on 91.
I tried timing changes to no avail. I'm not opposed to buying the expencive gas if its required. I am curious tho as to what is making it required.
_________________
I live in a state where all citizens are required to provide proof of insurance, but no person need provide proof of citizenship. |
|
| Back to top |
|
 |
ALB
Samba Member
Joined: August 05, 2008
Posts: 3504
Location: beautiful suburban Wet Coast of Canada
|
| Posted: Thu Oct 27, 2011 5:16 pm Post subject: |
|
|
What is the timing set at?
_________________
On a lifelong mission to prove (much to my wife's dismay) that Immaturity is Forever!! |
|
| Back to top |
|
|
modok
Samba Member
Joined: October 30, 2009
Posts: 27733
Location: Colorado Springs
|
| Posted: Thu Oct 27, 2011 5:29 pm Post subject: |
|
|
It is true that the higher octane is more resistant to dieseling, but the dieseling in itself is not absolutely a problem.
I've known some odd ball engines that did it so bad you had to use the clutch to stop them, but none of them have died from it yet, because they only do it at super low rpm, so when running they are fine.
One factor that may cause it to run-on is if set too rich at idle. The extra rich mix makes for more carbon, the carbon causes dieseling. Being a singleport with kadrons, it may not be possible to adjust leaner without side effects, so don't worry about it too much, but you could try leaning the idle mix a little and see what happens. |
|
| Back to top |
|
|
DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7543
Location: Whittier,CA
|
| Posted: Thu Oct 27, 2011 7:56 pm Post subject: Re: octane curiosity |
|
|
| priss wrote: |
1699 singleport
Dual Kads
Hemi cut stock heads
Engle 100
Stock exhaust
 UNknown compression |
As ALB asked, what is your timing set at? With hemi heads you'll need to increase timing 4 - 6 degrees over what you would normally run for stock. Modok may have given a clue as to the engine being too rich. With hemi cut heads you need to advance the timing. Berg ran as much as 40 degrees total. He advised that if you could run that much timing and didnt get any detonation or over heating then decrease the main jet one size and back the timing down to about 34 total. Might be something to try.
_________________
| Mitey62 wrote: |
| Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on. |
| RockCrusher wrote: |
JB weld the case halves....that'll keep the fretting to a minimum.  |
|
|
| Back to top |
|
|
mark tucker
Samba Member
Joined: April 08, 2009
Posts: 23947
Location: SHALIMAR ,FLORIDA
|
| Posted: Fri Oct 28, 2011 9:34 am Post subject: |
|
|
| ^^^ and run some chamber cleaner through.this is what happens when there is not enough quench+ torque is lower than it should be.low compression need more fuel,chambers with little to no turblance from quench have lower torque and need more fuel,and the extra fuel?well not all of it is burnt and becomes deposits that get hot & cause runon&detonation.if ti were mine I would snatch the heads and mill about .100 off to get a little quench back and then if the cr is to high do some chamber work that will not only help lower the cr but also make it breathe better. |
|
| Back to top |
|
|
craigman
Samba Member
Joined: March 28, 2004
Posts: 2425
Location: redding
|
| Posted: Fri Oct 28, 2011 10:22 am Post subject: |
|
|
How's your tune up? Valves, plugs, wires, points, ect.?
That can make it diesel easy. |
|
| Back to top |
|
|
Luftgekült
Samba Member
Joined: December 30, 2007
Posts: 388
Location: Canary Islands, Spain
|
| Posted: Fri Oct 28, 2011 12:44 pm Post subject: |
|
|
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has?
_________________
'71 VW 1302 1300cc in progress....
'72 VW 1302S 2109cc
'84 Passat Variant GL 1.6TD |
|
| Back to top |
|
|
DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7543
Location: Whittier,CA
|
| Posted: Fri Oct 28, 2011 5:44 pm Post subject: |
|
|
Hellooooooo Priss.............are you out there? 
_________________
| Mitey62 wrote: |
| Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on. |
| RockCrusher wrote: |
| JB weld the case halves....that'll keep the fretting to a minimum. |
|
|
| Back to top |
|
|
RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
|
| Posted: Fri Oct 28, 2011 5:57 pm Post subject: |
|
|
| Luftgekült wrote: |
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has? |
Not stupid at all....I'd call it astute observation.
_________________
[email protected] Please use email for all general inquiries.
I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly. |
|
| Back to top |
|
|
Bruce
Samba Member
Joined: May 16, 2003
Posts: 17639
Location: Left coast, Canada
|
| Posted: Sat Oct 29, 2011 12:13 am Post subject: |
|
|
| Luftgekült wrote: |
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has? |
Dieseling is the A/F mixture self igniting after you turn the key off. It is caused by excessive temperatures in the chambers causing hot spots hot enough to ignite the A/F mixture. The excessive temps are caused by retarded timing.
IOW, advance your timing to prevent the hot spots that cause dieseling.
_________________
| overheard at the portland Swap Meet... wrote: |
| ..... a steering wheel made from a mastadon tusk..... |
|
|
| Back to top |
|
|
priss
Samba Member
Joined: May 06, 2010
Posts: 348
Location: bradford MA
|
| Posted: Sat Oct 29, 2011 11:20 am Post subject: |
|
|
| DarthWeber wrote: |
| Hellooooooo Priss.............are you out there? |
yes Darth.......waaaaayyy out there!
_________________
I live in a state where all citizens are required to provide proof of insurance, but no person need provide proof of citizenship. |
|
| Back to top |
|
|
GusC2it
Samba Member
Joined: June 23, 2005
Posts: 1376
Location: Orlando, Florida, USA
|
|
| Back to top |
|
|
millerje78
Samba Amishman
Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
|
| Posted: Sat Oct 29, 2011 3:44 pm Post subject: |
|
|
| Bruce wrote: |
| Luftgekült wrote: |
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has? |
Dieseling is the A/F mixture self igniting after you turn the key off. It is caused by excessive temperatures in the chambers causing hot spots hot enough to ignite the A/F mixture. The excessive temps are caused by retarded timing.
IOW, advance your timing to prevent the hot spots that cause dieseling. |
are hot spots necessarily the problem though? I understand that dieseling can also be caused by the idle being set too fast, or from the idle circuit being too rich.
_________________
always seeking a better way
my 73 standard project
do your research, consult with experts, and buy quality parts. you won't be sorry |
|
| Back to top |
|
|
Bruce
Samba Member
Joined: May 16, 2003
Posts: 17639
Location: Left coast, Canada
|
| Posted: Sat Oct 29, 2011 6:43 pm Post subject: |
|
|
When you turn the key off, it stops power to the ignition. Therefore, there must be some other way to cause the A/F mixture to ignite. A high idle speed or a rich mixture doesn't provide that source of ignition.
I've worked on plenty of engines that were set really rich that never ran-on after you turned the key off.
When you have retarded timing, the burn is still happening when the exh valve opens. That sends the head temps way up because all that fire is now in the exh port. If you advance the timing, more of that heat stays in the chamber and gets converted into work, pushing the piston down. Thus, the exh gasses that leave the chamber are much cooler, and head temps reflect that.
_________________
| overheard at the portland Swap Meet... wrote: |
| ..... a steering wheel made from a mastadon tusk..... |
|
|
| Back to top |
|
|
millerje78
Samba Amishman
Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
|
| Posted: Sat Oct 29, 2011 6:58 pm Post subject: |
|
|
| Bruce wrote: |
When you turn the key off, it stops power to the ignition. Therefore, there must be some other way to cause the A/F mixture to ignite. A high idle speed or a rich mixture doesn't provide that source of ignition.
I've worked on plenty of engines that were set really rich that never ran-on after you turned the key off.
When you have retarded timing, the burn is still happening when the exh valve opens. That sends the head temps way up because all that fire is now in the exh port. If you advance the timing, more of that heat stays in the chamber and gets converted into work, pushing the piston down. Thus, the exh gasses that leave the chamber are much cooler, and head temps reflect that. |
this explanation makes good sense to me, Bruce. The reason that I mentioned idle speed is because I am currently dealing with a wandering idle speed condition in my sedan. I do not know why my engine is doing this, but sometimes it idles nice and low and sometimes it idles quite fast, above 2000 RPMs in fact. When I shut down the ignition when the idle is high, it diesels a bit; when I shut down the ignition when the idle is low, it stops cold. hmmm....perhaps I should get to the bottom of this idle situation.
_________________
always seeking a better way
my 73 standard project
do your research, consult with experts, and buy quality parts. you won't be sorry |
|
| Back to top |
|
|
modok
Samba Member
Joined: October 30, 2009
Posts: 27733
Location: Colorado Springs
|
| Posted: Sat Oct 29, 2011 7:41 pm Post subject: |
|
|
yeah, ok
mixture and timing will have an effect on it
Is it a problem? maybe maybe not.
But you can notice if it is worse or better depending on changes in mixture and timing, and that might tell you something useful |
|
| Back to top |
|
|
Bruce
Samba Member
Joined: May 16, 2003
Posts: 17639
Location: Left coast, Canada
|
| Posted: Sat Oct 29, 2011 8:01 pm Post subject: |
|
|
| millerje78 wrote: |
| I am currently dealing with a wandering idle speed condition in my sedan. I do not know why my engine is doing this, but sometimes it idles nice and low and sometimes it idles quite fast, above 2000 RPMs in fact. When I shut down the ignition when the idle is high, it diesels a bit; when I shut down the ignition when the idle is low, it stops cold. |
I bet you have a 009 distributor.
_________________
| overheard at the portland Swap Meet... wrote: |
| ..... a steering wheel made from a mastadon tusk..... |
|
|
| Back to top |
|
|
Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 80120
Location: Sneaking up behind you
|
| Posted: Sat Oct 29, 2011 8:08 pm Post subject: |
|
|
| Bruce wrote: |
| millerje78 wrote: |
| I am currently dealing with a wandering idle speed condition in my sedan. I do not know why my engine is doing this, but sometimes it idles nice and low and sometimes it idles quite fast, above 2000 RPMs in fact. When I shut down the ignition when the idle is high, it diesels a bit; when I shut down the ignition when the idle is low, it stops cold. |
I bet you have a 009 distributor. |
D'oh.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare
עַם יִשְׂרָאֵל חַי |
|
| Back to top |
|
|
lostinbaja
Samba Member
Joined: December 19, 2004
Posts: 4036
Location: Frankfort, Illinois
|
| Posted: Sat Oct 29, 2011 9:16 pm Post subject: |
|
|
There is a reason VW designed a fuel shutoff solenoid for the idle circuit of the carb. Is it working? Shut off the air and the fuel and it WILL NOT keep running, no matter how many hot spots there are. 
_________________
Jerry...
If it's being towed, it must be a trailer!
"Vee Grow Too Soon Oldt Und Too Late Schmardt"
RIP Morgan
My photos
http://www.manxgallery.org/gallery/album92 |
|
| Back to top |
|
|
modok
Samba Member
Joined: October 30, 2009
Posts: 27733
Location: Colorado Springs
|
| Posted: Sun Oct 30, 2011 12:19 am Post subject: |
|
|
kadrons don't have cutoff solenoids.......right?
But yeah, they surely put those on for a reason |
|
| Back to top |
|
|
|
