ausmini :: View topic

I have only ever had SU carbies ice up (on a non-heated manifold), never had it happen to the Dell'orto. And a frosty Canberra morning is just about right for carby icing!

I wouldn't bother doing anything about it unless it's a regular occurance. The fact that you slowed down to 90 means that the throttle didn't end up iced-open at 110kph like tends to happen with SUs, so I don't think you need to worry too much :lol:

Just seems weird that both times it's been with Shell 98 fuel (which I never use as a rule)

Just wondering what is the best thing to do if you find yourself with a stuck throttle due to icing and your doing 65 mph toward a corner. Does a good jab on the throttle usually break it away?

And if you think you are driving in conditions where you may get icing how best to avoid it? keep the throttle varied??

Funny part about this is that Shell & BP fuels come out of the same refinery!

Doogie

Author:	drmini in aust [ Mon Sep 03, 2012 4:23 pm ]
Post subject:	Carby icing
Sailing down the M4 on Saturday at 110KMH (4600 rpm) my 45 Dellorto on a Redline 3005 manifold suffered icing inside. This made the car pretty much undrivable below 1/4 throttle (missing, farting, surging, give it 1/2 throttle and then OK above that) so I slowed down to 90 for a while. Once I got off the M4 onto Northern Rd (80kmh) it came good. The car is running Shell VPower 98, only because all the BP servos around here were out of Ultimate 98 at once. The car has done this only once before in the last 20 years, coming up the Hume Hwy from Marulan one afternoon (coincidentally, also using VPower 98 then for the same reason). Anybody else had this problem with a Weber/Dellorto and Shell 98 fuel? I could heat the manifold by welding a pipe round it and running heater water thru it, but how common is this problem? I'm inclined to blame Shell, but surely it's only the detergent additive that's different? [edit] I pulled the plugs when I go home and they are all fine, and the same colour. [edit 2] This was 10am in the morning, so it wasn't that cold, and no rain in sight.

Author:	Mike_Byron [ Mon Sep 03, 2012 4:36 pm ]
Post subject:
For what its worth it happens all the time here on my mini but less so on Regina's 1100S. Mine is a HIF44 though and I do run the hot water manifold from the UK and once the engine is up to temperature its no longer a problem. However we do have a more extreme winter that the Sydney basin. Neither the VT commodore or the diahatsu charade suffer the same problems even at -8 C - more of a windcreen problem then.

Author:	Morris 1100 [ Mon Sep 03, 2012 4:49 pm ]
Post subject:
You know sometimes when you go up a hill and the mirrors suddenly fog up? That is the conditions when the carby ice usually occurs. The M4 is probably one of the worst places I know of for carby ice.

Author:	Anto [ Mon Sep 03, 2012 5:05 pm ]
Post subject:
I have only ever had SU carbies ice up (on a non-heated manifold), never had it happen to the Dell'orto. And a frosty Canberra morning is just about right for carby icing! I wouldn't bother doing anything about it unless it's a regular occurance. The fact that you slowed down to 90 means that the throttle didn't end up iced-open at 110kph like tends to happen with SUs, so I don't think you need to worry too much

Author:	Darrell [ Mon Sep 03, 2012 5:28 pm ]
Post subject:
Doc its not the fuel its the formation of ice in the venturi due to the ambiant conditions it hapens all the time on carby powered aircraft can be fatal on takeoff or approach what you need is carby heat as we do on planes

ausmini https://www.ausmini.com/forums/

Carby icing https://www.ausmini.com/forums/viewtopic.php?f=2&t=78307	Page 1 of 3

Author:	drmini in aust [ Mon Sep 03, 2012 5:49 pm ]
Post subject:
Anto wrote: I have only ever had SU carbies ice up (on a non-heated manifold), never had it happen to the Dell'orto. And a frosty Canberra morning is just about right for carby icing! I wouldn't bother doing anything about it unless it's a regular occurance. The fact that you slowed down to 90 means that the throttle didn't end up iced-open at 110kph like tends to happen with SUs, so I don't think you need to worry too much Yeah I had it happen only once on Barney (1293 with twin HS4s) it was one foggy day, across the highlands of Tassie just before Queenstown... back off for a corner and it'd keep going. On the Dellorto I reckon the frost around the butterfly is mucking up the idle and progression circuits, once you hit 1/4 throttle it's fine. But that's be about 160kmh in my car... Just seems weird that both times it's been with Shell 98 fuel (which I never use as a rule)

Author:	MiniVLT [ Mon Sep 03, 2012 6:22 pm ]
Post subject:
I had it happen to me cruising through the Otways in Vic in winter, 45 DCOE, 1360, no manifold heat / coolant heating.......backed off at 110 ~ 3800rpm & it didn't back off....clutched it & the engine rev'd to ~ 4300rpm Had to pull over, jump out & pop the bonnet.....pulled back on the linkages & you could hear the ice break off & go down the inlet....back to normal idle then. I had been cruising at a constant rpm for a fair while! Cheers Shane

Author:	AEG163job [ Tue Sep 04, 2012 12:18 am ]
Post subject:
drmini in aust wrote: Just seems weird that both times it's been with Shell 98 fuel (which I never use as a rule) My Subaru serviceman says Shell fuels are the worst, although not sure if that opinion has any veracity. But he does rally Rexes and makes 'em go pretty fast, so I guess he must know something.

Author:	phillb [ Tue Sep 04, 2012 6:28 am ]
Post subject:
Just wondering what is the best thing to do if you find yourself with a stuck throttle due to icing and your doing 65 mph toward a corner. Does a good jab on the throttle usually break it away? And if you think you are driving in conditions where you may get icing how best to avoid it? keep the throttle varied??

Author:	MiniVLT [ Tue Sep 04, 2012 7:25 am ]
Post subject:
I did hear Shell Optimax fuels were hydroscopic, which means they attract water! If I remember correctly I was using Shell when my icing occurred. I moved away from their fuels & now use Caltex only. I can't justify BP fuels, they're the most expensive fuel company & when i tried their 98 Ulimate I didn't see any difference to the 95 Premium from Caltex I was using. Using Caltex I found I got better mileage and my cars seem to run smoother. Personally I haven't run these fuels through an A series motor as my last mini was back in 1998 & fuel companies are constantly changing their formula, but when my next one is on the road I'll be starting off with Caltex 95 & then 98. I'll be running a basic ignition computer with 2 different advance curves so I could even swap between the 2 depending on how rich I feel when I fill up! phillb, I had to grab the linkages & physically pull them back towards idle, just stabbing the accelerator pedal only made me go faster! Cheers Shane

Author:	doogie [ Tue Sep 04, 2012 8:11 am ]
Post subject:
Funny part about this is that Shell & BP fuels come out of the same refinery! Doogie

Author:	diecast [ Tue Sep 04, 2012 8:43 am ]
Post subject:
Yes, that is true, BP and Shell fuels are from the same refinery in Sydney and pretty much identical. I was chatting to an operator from Shell Clyde Refinery recently who not only said that, but more interestingly said that when they run low on regular unleaded stocks at the refinery, they will ship premium fuels to service stations to be sold as 91 unleaded. Now thats a bonus! They never swap out 98 and replace with 91 though.

Author:	smac [ Tue Sep 04, 2012 8:46 am ]
Post subject:
phillb wrote: Just wondering what is the best thing to do if you find yourself with a stuck throttle due to icing and your doing 65 mph toward a corner. Does a good jab on the throttle usually break it away? And if you think you are driving in conditions where you may get icing how best to avoid it? keep the throttle varied?? If your brakes can't overcome your throttle you need better brakes.

Author:	bnicho [ Tue Sep 04, 2012 9:25 am ]
Post subject:
doogie wrote: Funny part about this is that Shell & BP fuels come out of the same refinery! Doogie Almost all raw 91 and 95 octane fuels come out of a local refinery. The blend of addititives each company uses for it's own specifications are added at the terminal. I don't know about the others, but BP Ultimate 98 only comes from BP's Kwinana or Bulwer Island refineries. It's trucked everywhere from there. Part of the reason it's expensive.

Page 1 of 3	All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/

Author:	drmini in aust [ Tue Sep 04, 2012 4:28 pm ]
Post subject:
doogie wrote: Funny part about this is that Shell & BP fuels come out of the same refinery! Doogie BP used to come out of Shell's Clyde refinery but not now, I believe it's shut. There is/was a pipe between the refinery and the BP terminal, under Duck creek.