Heated fuel setup...

[takza]

This is some info on how to set up a heated fuel system on a Tercel 3AC engine.

Actually...it's really a simple setup...but allows a gain of around 10% in MPG.

Also there is likely a gain in "power", though I haven't really tested this....except that I noticed a very good level of power on a 50F day with this setup & advanced ignition.

Cons: on an +85F day I get a dieseling effect where the engine will spin backwards when shut off.

I have noticed some hard starting after the car sits overnight.

Also, in city driving on a hot day...the fuel temps will get into the upper range and stay there....causing the engine to run "hot"...not by the temp gauge though.

Possible that various parts in the the carb will have a shorter life if the fuel is heated.

With my change to NGK plugs I expect some of these effects to be reduced.

Here is a pic:



This is 1/4" diameter soft copper tubing that is wrapped around the upper radiator hose about 8 times. I wrapped this line around something that was close to the diameter of the rad hose first...and then put it on the rad hose.

** the coil on the right is from a previous attempt at using heated water injection...worked but at a cost in "power" with no discernable mileage gain.

The line nearest the camera is coming from the fuel pump and the line in the background is going to the carb. The line to the carb was routed right above the heat shield under the carb in order to pickup some heat from the exhaust manifold.

The coil and the RUBBER line going to the carb need to be insulated...the best material being the foam/alum tape that is sold in hardware stores? Maybe fiberglass tape would work too.


This set up gives the following gas temps:

Used an in/out thermometer on the copper gas line around 6" before it enters carb:

<span style='color:blue'>* ambient temp = 80F</span>

* within 1 mile from cold start = 93F

* 129F to 132F on back roads

* sit 10 minutes = 143F and falling

* drive 1/2 mile = peaks at 147F...then drops

* 55 MPH highway cruise = 124F - 127F

So the faster you drive, the lower the fuel temps.

Have not driven this setup in winter...I WILL have to insulate the gas line going to the carb from the coil and also partially block the radiator to keep the coolant flowing thru the top rad hose.

* Have partially blocked the rad using some light sheet metal sprung between the ledges top and bottom at the back of the rad...plus some fiberglass insulation behind this to block the flow...and a coat hanger "security" wire across the sheetmetal to help hold it. Have about 1/2 the rad blocked...with most of the opening where the fan is and on the pass side. Above 50F, the fan will run some unless I run the heater on the second notch. Fuel temps were around 85-95F at highway speeds on a 35-40F day.

<span style='color:red'>Cautions about this installation:</span>

The heated coil is spliced into the line going from the fuel pump to the carb.

You need to watch the routing of ALL lines to avoid chafing and you need to use the copper line until you get to the back of the carb and away from the serious heat sources. Use ONLY rubber hose made for gas and new ss clamps. Tie the lines down at various places to avoid vibration and chafing.

I would use all new rubber hose.

Do I recommend setting this up? NO. This is just info that CAN be used by someone interested in this sort of thing....you DO have to pay attention to what you are doing...it is experimental in nature.

You DO NOT play with gasoline...it will burn you.

Due to there being no device to control the gas temps....if this was setup in the northern US-Canada it might be best to use 9-10 coils...in the southern US maybe 6-7 or so.

<span style='color:blue'>Postscript and addenum: after adding insulation for winter driving and where gas temps increased by 5 to 10F on an 85F day....con symptoms noted above were more or less absent...likely due to the NGK plugs. The Bosch plats run too hot.</span>

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Heated fuel results over winter:

* I had the radiator partially blocked in order to keep the coolant circulating thru the radiator during cold weather. The elect fan tended to run part of the time when temps got above 50F.

* I had no noticable mileage gain during this winter vs previous winters WITHOUT a blocked radiator and using heated fuel.

* Conclusion...not worth messing with.

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...added a bypass valve to heated fuel line...and did a power test:

* on a 60F day (ambient)...(2) 30 to 55 MPH tests show that it takes 8% LESS time to reach this speed in 5th gear with heated fuel.

no heat = 27.7 secs

heat = 26.4 secs

Fuel temp during this test was 123-124F....radiator was partially blocked.

During warmer weather I would expect the fuel temps to be adjusted to peak at around 150F....maybe the minumum at 55 MPH cruise would be around 130-135F.

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Newer heated fuel method:

* using a length of copper pipe the same OD as the ID for the top rad hose...wrap about 12-15 wraps of 1/4" copper tubing tightly around this and solder it to this pipe section...then insert it in the top rad hose using ss clamps.

* install (2) brass tees and a needle valve into the gas line running from the fuel pump to the carb....so that if the valve is open...most of the fuel goes directly to the carb and is not heated. If the valve is closed...all of the fuel is forced thru the coil and is heated. If the valve is somewhere in between open and closed...the fuel temps are regulated. Use a low flow fine adjsuting needle valve rated for 200F temps.

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[3A-C Power]

Did you know about the fuel heater that's already in the float bowl of the carb? It is set to go on when it's cold but is shut off when the engine is warm. If I recall correctly, all cars with the feedback system also have the fuel heater as well as the cold mixture heater in between the carb and the manifold.

[Fingers]

Watch out for over heating of the fuel.

The IDEAL temperature of a air/fuel mixture when entering the cylinder is between 100-130 degrees f. So your fuel temps may be fine, but once running through the intake and combined with warm air/exhaust manifold heat and the combination may be too hot. Above 130 and the fuel begins to evaporate too much and come out of mixture, resulting in a poorly distributed charge in the comb. chamber. Below 100 and there is the possibility of pooling in the intake.

B.T.W. Did you all know that on an average we use close to 9000 gallons of air for every gallon of gas our engines burn?

[Guest_Lateer]

I'm still puzzling as to why you'd want to do this.

After all, once the engine is warm, the fuel hitting the hot manifold will vapourise, no matter what temperature it's at.

I'm not sure there's any gains to this at all...

[takza]

The point & purpose is to improve mileage and power...it does both. A 10% gain in mileage and as far as I can tell...not as much drop off in power in warmer weather.

The higher gas temp causes the gas to evaporate faster and more effectively and there is also a slight reduction in gas volume going thru the carb.

As far as the temps of the gas getting too high...the 9000 to 1 ratio of air to gas pretty much says that the air will control the gas temps entering the cylinders.

As I say...this isn't for everyone....this is useful information...and you shouldn't try it if you don't have a real interest in this sort of thing....cause you need to pay CLOSE attention to it.

[Lateer]

Wouldn't that setup alter the mixture going into the manifold, if you're reducing the volume going into the carb?

Oh. Silly me. The change in volume there would be absolutely negligible. Vapourisation however would be much, much better if the fuel was hotter.

It looks like the sort of mod someone would do if they were in a snowbound sort of place for most of the year.

I personally wouldn't, as it would expose too much fuel line to too much heat during summer. It would be nice in winter, though.

[Typrus]

Errrrrrr... Why not add a simple temp-controlled thermal fuel router? i.e. if the fuel reaches too high a temp, it is routed to a less-coil part. In other words, have two parts to the system. one with 6-8 coils and one with 2-4 coils. If the 6-8 gets too hot, it redirects to the 2-4 or uses them proportionally.

Hey, lets get really intelligent and use an electric heater than moniters fuel temps and adjusts heating accordingly. Why not, it could just be set up like a heating pad on the outside of some copper tubing, if that makes sense. Make there be an override switch that turns it off for the last few miles of your trip to prevent hard starts. This would probably be the most advantageous thing, as it would prevent possible carb damage from too high of fuel temperatures.


Just a little minds ideas.

[takza]

I would add a fuel thermostat if I could find one at minimum cost or at all. A solution would be to increase the number of coils to maybe 16 or so and then add a manual bypass valve so in warm weather the temps could be reduced....while in winter they could be increased.

An electric heater might work except that the alt would draw some power to run it and cost some amount of MPG....coolant heat is free.

The hard starting might be there if NO heated fuel as being used...can't say.

[Typrus]

What is the diameter of the fuel line? I want to examine the possibility of a 1-into-2, switchable valve that could divert the fuel to the coils, or in a straight path. Possibly a combination as well.

[takza]

They measure copper tubing by the OD...which is 1/4" and the measure rubber tubing by the ID...the gas line going to the carb is around 1/4" ID.

You'd basically need 1 valve and 2 tees...used with one coil of maybe 12 loops...I use brass barbed tees...1/4".

Easiest valve is one with 1/4" barbed fittings or you could use one that went into 1/4" copper tubing and clamp to that.

Open the valve and you'd get a regular flow of gas to the carb...close it and you'd get heated fuel....somewhere in between...you get a regulated temp.

[Typrus]

Where can I get ahold of these? I tried searching last night and found no valves that small and nothing but plastic Y's and malleable tees.

[takza]

The sources of last resort:

<a href='http://www.mcmaster.com/' target='_blank'>http://www.mcmaster.com/</a>

<a href='http://doityourself.com/store/' target='_blank'>http://doityourself.com/store/</a>


I look for valves that can handle 200 F temps. You'd want a fairly fine adjusting needle valve with pretty low flow rate.

If you find other souces for this kind of stuff..let me know.

If you try this setup...you DO need to pay close attention to it....since it is experimental....I use one of those in/out automotive thermometers to keep tabs on the fuel temps.

[raybbaby]

I'd like to do this as I'm installing my new Weber. Any trick to coiling copper hose without creating kinks and flatspots? Also wondering about putting in an inline pressure regulator and is there such a thing as an inline temp gauge to keep an eye on fuel temp and possibly add or subtract coils accordingly. Thanks for any pointers.

[takza]

I used a pipe about the same diameter as the top rad hose.

I wouldn't really do the fuel heat with a carb again...and am probably going to remove the fuel heater...espec if the mpg gains from the Condensator continue as expected.

Probably not a good idea with a new Weber?

[raybbaby]

What is a condensator and where did you get one? Are they readily available to the public?