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mad_wolf

Help reducing fire risk

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I like to start a thread which might help us all.

 

After 2 times being in need of the fire extinguisher

because of fire from the carburetors and actual an other Elite completely burned down in Germany I decided to construct something to reduce potential fire risk because of backfire of the Motor. Remember I still have not mounted the bonnet yet and have the fire extinguisher always nearby while starting. Otherwise I would not have the need to work further on for this Lotus because it would be lying melted in my garage. My actual plan is to make trumpets curved up so that exceeding fuel does not drop out but runs into the carburetor again. These trumpets will have a two stage stainless steel sieve as a fire barrier.

But I'm sure there are a lot of Lotus enthusiast which have ideas or solutions. So please join this thread to stop the decrease of existing Lotus 907 cars

 

 

 

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Upgrade today to remove Google ads and support TLF.

The standard airbox helps reduce the risk of fire.

Fit a plumbed in fire extinguisher. I have had one fitted on my Esprit since the late 1980s.

My current one was purchased from JJC Race & Rally - they seemed to have stopped supplying the one I have.

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As Chris says I would say using the Lotus air box helps or have you ditched it?

 

buddsy


 

"Belief is the enemy of knowing" - Crrow777

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plus, if you install an open air intake the engine might get hot air instead of cold air which does not help.

I thought you had the orginial box installed, sorry...

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A very basic point is to ensure you don't have the ignition timing set with too much static advance. This will cause the kind of backfire you describe, and will eventually trash your starter motor because of the kickback it produces. Also ensure your ignition system and plugs are in A1 condition to avoid any buildup of unburnt gases.

An airbox is definitely a good idea!

ATB Richard

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I have the Distributor without vaccum so static timing  is" hard on the Edge". You mean I should use a bit less than Lotus specs ?

And are there not also burnd 907 with original airbox ?

I'm thinking of some short trumpets curved up inside the air box

 

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I'd be surprised if it backfired on standard Lotus specifications (which is 9 degrees I think for your spec 5 engine), but vacuum doesn't really make any difference during cranking anyway. I think a lot of fires are aggravated by poor quality or old fuel piping/connections.

Dyno reports I've seen (from the Jensen Healey forum) show better results using a standard Lotus airbox with filter than either the JH airbox or trumpets. I'm not sure about the trumpets inside an airbox though.

ATB Richard

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As Richard says, a lot of fires are due to old fuel pipes leaking on to the distributor.

The worst are the metal braided type as people think that because the braiding looks ok, then the rubber pipe must be fine, they need changing every few years.

Fuel dripping out of the trumpets could be wrong float height in the carbs.......but if you want some angled trumpets there are a set of 90deg ones for sale on ebay from an alfa at the moment.

Edited by pbharcourt

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Yes fuel pipes should be regarded very sensitive and in any doubt change them !

I have seen theses alfa trumpets but I think I could produce the fire preventing effect with smaler ones.

Another thing I did is to change the plastic oil pipe to the oil pressure gauge to a Copper one (with some coils to keep it flexible enough).

When melting and burning, this is an enormous fire accelerator. It can spray burning oil anywhere.

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About the timing specs: I use Spec 3 which is 16° static.

You mean I should reduce this and would automaticaly have less stress with fire ?

Lutus spec.pdf

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I replaced my ignition with an electronic one and removed the distributor. Gets the spark source out from under the carburetors and allows better control of timing, and easier maintenance.  Especially important on the 910 turbo motor, as the carbs are pressurized.   But you have to fabricate a crank sensor and add new coils and mounts etc, and you're well on your way to an electronic fuel injection installation.

 

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6 hours ago, mad_wolf said:

About the timing specs: I use Spec 3 which is 16° static.

You mean I should reduce this and would automaticaly have less stress with fire ?

Lutus spec.pdf

Ah! I see you have the 1975 engine. I believe the spec 5 (from 1976) has the E cams which are slightly milder and give better low down torque. Yours is, if you like, tuned more for top end power. Do you regularly experience backfiring when you try to start it? If so you could try reducing the static advance by a couple of degrees and see if it makes a difference, but I would say that the standard settings should be OK.

ATB Richard

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Personally I will be fitting an under bonnet fire extinguisher system and moving the fuel lock valve as close to the tank as possible to limit the amount of fuel available above the exhaust. This has been after changing the fuel pipes from the nylon, which if still original, will be very perished by now.

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Dear Richard,

 

yes I see he backfireing while starting and in the warm up period when I try to rev up.

When the Motor is warm I have a good iddle behaviour.

But the Motor behavious like a race Motor. Very different to my Jensen Healeys.

 

I have allready tried different positions of the distributor but then the motor feels like sluggish and tired far away from ist promising power.

 

And yes Thomas it will end up in an electronic injection system as I already have this mad Convertible Esprit Turbo injection car.

And the hint of mike will also be followed.

 

But first I will have to get the TÜV / MOT and need 1 year experience with the car in original behaviour.

There is allready an accu spark ignition in the distributorand a good new coil.

 

The intendtion of this thread is generaly to help all owners not to sacrifice their car to the Flames.

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Another name for the airbox is the "the flametrap".

Running without the airbox increases the prospect of fire.

I do not think upturned bellmouths to stop petrol dripping out is a good idea. One backfire and I think you will just have coated your engine bay in petrol droplets.

I could be wrong, but I dont think this is a good idea.

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This is a worry to all of us, I have a simple ignition kill switch under the dash, a battery isolation switch in the engine bay and an extinguisher mounted across the front of the drivers seat.

The closest I have been to having a fire is from oil dripping on to the exhaust manifold from a leaky cam cover.

The carbs do flood if the floats are set wrong and petrol pours into the air box and evaporates, The box contains it and although  I have real worries about a possible fire, so far the box had kept things under control, I can't see any advantage in trying to contain the fuel by upturned trumpets, the engine will be overfuelled.

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OK I have understand,

you all trust the air box so will I.

But did anyone tried to use some metal sieve inside as a flame barrier?

And I will build in an fire extinguisher.

But this thread is about preventing.

So are there more adjustments on the motor possible to reduce the risk.

For example should I use a 123Ignition and reduce the static timing but end up with the 32° for this motor ?

Or should I use vacuum to reduce the timing?  My observation is that at idling the motor runs with this 16° absolute fine and smooth.

The most of the backfiring comes while starting and above idling until 2000 rpm.

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You shouldn't have any backfire through the carbs when the engine is tuned correctly. I would suggest you get the engine tuned. It sounds to me like the carbs are out of balance with each other. The static timing should be about 9 degrees btdc. Any more than that will cause difficulty starting and general running. 

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Dear Jason,  I agree.

But the carbs where tuned. Days before the motor does start better an did run better.

Nothing changed in between.

So at this unhappy day something went wrong but did lead to fire.

So I'm looking for reducing the Risk even when something is not at best condition.

 

And does someone know what is special on a spec 3 Motor that id should have this strange timing.

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Don't over look poor wiring as the source of ignition. 40 year old wiring and capacitors all wrapped up behind the dash with some foam would also be a prime candidate as an ignition source. Don't just focus on the inherent risks with the fuel. Make sure the wiring is in good condition and still fit for purpose. 

As Dunc has done, fit a battery isolator or overspec a new loom.

Also don't park near the walkie talkie in London as I have heard it focuses light onto the street and melts cart trims. A fibre glass car might not fair to well.

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There are some other possible Risks:

Oil dropping on the exhaust manifold. Neopren sealing on the camshaft cover do a better job then the original.

Fuel tank higher than the carbs can flood the intake manifold. (Fuel cut of Valve). 

And as I'm from Germany, the risk with the walkie talkie in London is not very high for me and my car.

 

 

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