Walbro 1107 choke removed.....

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shaunomercy

Active Member
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40
Just ordered a new tuned g320 and in the specs the carb has the bearing mod which I know about and the choke removed....
This caught my attention...
Not a great deal of info about the benefits but came across a bit on a helicopter forum...!!!!!!
Apparently adds over 5% more power...
Can any of you experienced gassers elaborate more on this mod ? Clearly it's to do with flow rates thru the carb...
Engine is a g4z Evo 32

Cheers.
Paul
 
I know OBR has a new updated carb wt-1242 they say they collaborated with Walbro on. Some of the features are ethanol resistant primer bulb, sprial wound diaphragm (approved for ethanol as well).

I think the biggest performance mod is the pop off spring pressure (aka metering spring) is lower. If memory serves correctly a stock 1107 pops at around 30 psi. The new 1242 spring pressure is set at approx 18-20 psi. The main benefit should be more fuel a little quicker at the low end. This results in less bog during the transition between when the high side circuit is fully engaged.

I just ordered an OBR engine with this carb that is the only reason I am slightly familiar with it. Guys please correct me if this is inaccurate. Your carb may be similar.
 
Seandonato73
Yes the choke Rod hole has been plugged. It's definitely an 1107 m8
Very good, since we didnt have any pics of it had to assume it's a 990. You'll see marginal performance increase at WOT. Doubt you'll notice much difference anywhere else, as the butterfly limits flow, and venturi size hasn't been altered. Hence why its claimed an 990 and 1107 flow similar, the 990 doesn't have the choke and the 1107 does. I still typically favor the 1107 for ease of starting, I have never notice any major performance differences between the two. All things being even I think a 5% gain from removing the butterfly is very optimistic. Say the engine claims 9 peak hp. 5% is .45 hp. No choke removal is going to give you that much more power or even close to half a hp.
 
Guess I ordered about a month too early, modded bore 1107was just released by OBR.
 

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Sean got the engine in and run in. Got to say I'm well impressed with the g4z Evo 32. Pulls well and has a screaming top end.
Don't think I'm to far off tune with the high needle. Maybe needs richening a little more.
It's not easy going on colour as I'm running alkylate petrol or white gas as it's better known your side. Far far cleaner burning and no ethanol.
I'd appreciate your thoughts tho.
Cheers Paul.
 

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Cheers Sean.
Think I've got the tune pretty much spot on now.
A nice tan colour. I highly recommend white gas too.
Far cleaner burning in the engine and no ethanol issues and no gumming up of the carb..
I'd love to see if there's any power difference between pump fuel and white gas, tho the main bonus for me is there is negligible smell to white gas, so the car doesn't smell and neither does the garage or house when working on the car.
 
White gas - Figured is add this.👍

White gas is a common name for a number of flammable substances:
  1. As a generic term for camp stove and lantern fuel, its most popular current usage, also called Naphtha, 100% Light Hydro Treated Distillate, or Coleman fuel
  2. Pure gasoline (without additives), commonly used when leaded gasoline was the norm to prevent fouling in situations where the properties of the lead additive were not required
  3. Un-dyed gasoline
White gas should not be confused with white spirit, which is more akin to kerosene.

 
Striikar

Yep you are correct. Coleman fuel or alkylate petrol.

Sadly its not as cheap as it is your side of the pond but plenty of benefits for the cost being ethanol free, long shelf life and doesn't stink the garage or back of the car out unlike normal pump petrol..

I can work on the car in the dining room without getting grief city as there is no smell...
 
Striikar

Yep you are correct. Coleman fuel or alkylate petrol.

Sadly its not as cheap as it is your side of the pond but plenty of benefits for the cost being ethanol free, long shelf life and doesn't stink the garage or back of the car out unlike normal pump petrol..

I can work on the car in the dining room without getting grief city as there is no smell...
Surprised you don't have access to aspen fuels. Very similar, but made for engines. As far as I know white gas or camp fuel has a low (around 85) octane rating. With the addition of having non of the additives that engine specific fuels have. I have never ran it in an engine so can't attest to long term viability.
 
Surprised you don't have access to aspen fuels. Very similar, but made for engines. As far as I know white gas or camp fuel has a low (around 85) octane rating. With the addition of having non of the additives that engine specific fuels have. I have never ran it in an engine so can't attest to long term viability.
Tried an experiment at the weekend...
Bought 2 litre of premium 99 octane that's supposed to be ethanol free. Esso brand in the uk.
Run a full tank of that back to back with the Aspen fuel...
The engine certainly is more responsive with the Aspen.
I can only attribute that to the fact the Aspen is far cleaner burning than the pump fuel.
The reason for buying the 99 octane was that's supposed to be ethanol free, the regular 95 pump fuel has ethanol @ 5%. I know these engines don't make use of the higher octane...
 
Ethonal isn't going to hurt the engine unless you letting it sit in the carb. And no you don't need 99 octane lol. Glad you liked the aspen fuel, highly recommended by some mates from across the pond.
 
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