Carb Icing Pissing Me Off
Turbo Mini Forums

For the last few days my car has been runnung crap soon after leaving for work. And for the last few days it's the first time I've used the car as a turbo in the freezing conditions.

I assumed that it was carb icing causing the problems, so when the boost gauge 'froze' this morning, I stopped to investigate. Carb icing is definately the problem.

However, I'm not sure of a solution. the manifold has had its heating pipes cut off, but I'm not sure they would help. The manifold its self was warm and ice-free, just the carb was being affected.

I think I need to either find some hose and duct warm air from the rad to the carb, or use a bit of copper pipe wrapped round the manifold and then round the carb, and hope it transfers some heat.

Any other thoughts

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Maybe some insulation on the bonnet above the carb and just stop the cold air directly hitting it.

I had carb icing on my turbo a few years ago, it was a pain in the ass!

other than than, more boost and no intercooler! ha ha!

dont think you are running an intercooler though are you? if you are it could be the cause.

Yes i do have an intercooler. I did consider taking it off to see if it made a differance.

Might be worth a try.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

you could try fitting that thermostatic flap thingy which is fitted to the Renault 5 turbo intercoolers in your intercooler, what intercooler are you using?

Team Racing

Series 2 RS one, so not that easy.

I can quite easily replace it with a bit op tube for the winter though.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Wil, I suspect you already know all this but here goes anyway.
There are two types of icing,
1) manifold iceing, where ice forms on the bends in the manifold and restricts airflow. This is generally cured by utilising a heated manifold.
2) Throttle plate iceing where the reduced pressure at the throttle plate causes a temperature drop and consequent ice formation.
The key factor in all this is Humidity.
It is quite possible to have carb icing at 50-60 degrees F if the humidity is high enough. In fact if the ambient temp is below freezing the humidity will be low and icing will not happen.
It's generally a few degrees above freezing on damp days when it happens in theUK.
I think you are suffering from throttle plate iceing and I would bet it is occuring not long after start up and before the engine is up to working temperature. Once you are using boost the inlet air temp should be high enough to prevent it.
The fix would be to duct warm air into the filter and blank off the intercooler while the weather is crap.
Connecting the water to the manifold will not be much use to fix the problem if it is throttle plate icing, you need to raise the inlet air temperature.
Regards
Dave

You're spot on there Danboy. The only thing is that once it's frozen (as you say early on), crusing aong the A59 makes no differance, it just stays frozen. The only way to un-freeze it atm is to stop the engine and let the heat-soak melt it away.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Wil, Once it begins to freeze the pressure drop causes a lower temp and the bigger the amount of ice the lower the temp becomes creating more ice.
I think the secret is to stop it freezing in the first place by feeding warm air into the carb.
Regards
Dave

My only experience with carb icing was actually caused by water in the gasoline. Might be worth a try to add one of those methanol-based drying agents to the gas.

1275 with Back Door Turbo

ah, i'd go with blocking the intercooler off, either by linking it out or just by covering it over to stop the airflow through it.

i think there will be enough heat then from the compressed air to keep the carb warm enough.

i had this with the v8 when i was running an su , in the end i wrapped a length of heater hose, with engine water running through it ,around the ally pipe connecting the carb to the turbo (suck through), and bolted a copper plate to the ex manifold and it sat under the turbo . made a big diff .
in your sit wil i'd try taping up the intercooler gills with a piece of card board to stop the air going through,and run a pipe from the turbo inlet to a filter mounted above the ex manifold , you could baffle the filter so it only collects air from the manifold area too .but high boost would be a bit of a no no !

Edited by robert on 14th Dec, 2007.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

pipe water through the inlet manifold like it should be and tape the intercooler up with duck tape for now while the freez is over

you should then be fine
metro turbo never suffer this problem

dont the renault 5 use a carb heater? a little electric fan on a switch in the cabin that can be sticked on when needed? blows hot air onto the carb.
seen it on my mate r5, not sure where it got its hot air from though. puzzled me that one did.

not sure if thats any help to you, it just clicked that this might be what that is for.

The R5 thing is known as the anti-perc fan, the idea was to blow COLD air at the carb to stop the fuel vapourising when stopping the car after a run, helping with hot restarting.

Wil, try getting some 10mm cooper pipe and wrapping it around the dash pot and then plumbing it up to the engine coolent, you may find this helps

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didnt nic post a pic recntly of an teeny tiny electric blanky you can wrap around your carb?

think it was for air coled vw's but cant remmber now

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Hi,
As said above stuff a 15mm copper pipe through the inlet manifold, may cover the I/C if you've still got problems after.
Once it's froze the only thing is to spot and wait a couple of mins the re-start, doesn't take long to re-freeze though :(
Cheers,
Gavin :)

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Apparently there are some sort of "pill" fuel additives that can help reduce this.

Ive heard of them, but never seen them. This was always a problem with mine too during winter. I just blocked off the IC core...it did help, but it needs a proper thawing out once frozen.

In a thread over on PH a while back, someone suggested that VW had these fuel pills ( although thats probably from a LONG time ago ) as Polo's used to give terrible icing trouble.
I had heard that Motorbikes suffered from it, and thats where I was told to look for the additive.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

On the way home I stuffed a big padded envelope infront of the IC. It was fine all the way home. However, it was a tad warmer this evening than this morning.

Cheers for the ideas, I might try a few over the weekend.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

In Sweden we use "K-spirit" works great! Lower CO aswell –good for mot. Vaporisation af the fuel "steel" the heat around the carb mouth, then the water in the air build up the ice, when it get colder the problem dissapear due to less humidity.

Cheers!
Marcus

internationally known as "big" swede

Marcus, What is "K-spirit"?
Regards
Dave

internationally known as "big" swede

internationally known as "big" swede

Doe it come out of a petrol pump at the garage?
Regards
Dave