Blending update

[Johnnojack Senior Member Find all posts View Profile Close Johnnojack]

Re: Blending update

While it will not help cold starting or running, the provision of a heat exchanger immediately before the IP will help warm up the IP before changeover to vegetable oil. When changing back to the start fuel, it will also help heat this fuel up to minimise the likelihood of "thermal shock" when cold fuel enters the IP.
I do not know whether "thermal shock" in relation to cold fuel entering the IP has any basis in fact, especially in Australia, and I don't have the facilities to perform any testing to demonstrate whether this is or is not an issue, but it is something to consider.

A Heat Exchanger in this location will also heat any cold vegetable oil from the filter, before it enters the IP.

Regards,
Tony

Pre heating the IP has got to be useful I guess. However I think one should not change to Vege until the engine is hot or at least up to operating temperature and at that stage the IP is usually hot as well.

As for thermal shock of cold fuel on a hot IP I believe it is a non issue for the following reasons. If you have driven far enough to justify switching to vege (I never switch unless I'm doing 20ks or more) then the whole engine bay is hot and diesel fuel in filters and lines within the engine bay will already be hot. Secondly diesel fuel has such a low specific heat value that on entering the IP it is immediately warmed up by the mass of the IP itself.
Finally if IPs were so prone to damage from thermal shock then it would be disastrous to drive through a puddle of water with a hot engine.

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Blending update

As I said:

While it will not help cold starting or running, the provision of a heat exchanger immediately before the IP will help warm up the IP before changeover to vegetable oil.

and

I do not know whether "thermal shock" in relation to cold fuel entering the IP has any basis in fact, especially in Australia,

But I believe that

A Heat Exchanger in this location (immediately before the IP) will also heat any cold vegetable oil from the filter, before it enters the IP.

is a valid statement and should not be dismissed.
This is also promoted by other experienced WVO proponents on this forum.
Regards,
Tony

[craigcurtin Senior Member Find all posts View Profile Close craigcurtin]

Re: Blending update

thanks for the feedback guys

Tbird - just to clarify - are you seeing a 20degree rise when using your injector line heaters ?

I have been blending for the last two weeks and have noticed a definite difference in how the car is starting compared to when it was on DinoDiesel - ambient temp this AM was 12celsius, running on a blend of 70% WVO, 25% Kero and 5%ULP the car took about 3 seconds to start, previously while there was still Dino in the tank it was almost instantaneous

Dave Jones - would you recommend adding more ULP or more Kero in this example ?

Craig

[tbird650 Senior Member Find all posts View Profile Close tbird650]

Re: Blending update

Tbird - just to clarify - are you seeing a 20degree rise when using your injector line heaters

Yep. This is how I've been able to discover that the heater has stopped working. Over 2 years the heaters have stopped 3 times for a variety of different reasons. I've now learnt to check the fuse, relay etc.

definite difference in how the car is starting compared to when it was on DinoDiesel

That is what I find too. Some extra cranking is required and it seems the behaviour is more accute as the temperature drops. I have wondered if there would be any additive that would help this?
For instance with methanol as fuel for racing, the recipe is something like 97% methanol, 2% acetone, 1% castor oil. The acetone in this instance was said to improve cold starting. I haven't noticed any difference when using acetone as an additive for starting with veg (at least none that I could determine).

Heat Exchanger in this location will also heat any cold vegetable oil from the filter, before it enters the IP.

I would go along with that, especially in cooler climates. I once run a 100w nichrome wire wrap on the veg filter. It would get very hot during the time taken to bring the engine up to temp, ready for changeover. It makes a difference in this case because the fuel is stationary. Once changeover occurs, the fuel rushes through the filter at 500ml a minute, then the benefit is minimal.

Finally if IPs were so prone to damage from thermal shock then it would be disastrous to drive through a puddle of water with a hot engine.

I don't buy into the idea of thermal shock either. I've never worried about it and I've never had IP failure (touch wood). I think at least in my case, at purge to dino, fuel runs through a hot valve, then through a hot fuel line before it reaches the IP. Then it's going to mix in with hot fuel in the IP. In addition, if the dino filter is under the bonnet, its' contents will be raised in temperature from heat radiation from the motor and radiator. After all, it has had to sit there stationary while you drive on veg (with a smile on your face!).

[neil Senior Member Find all posts View Profile Close neil]

Re: Blending update

Personally I wouldn't touch your blend.
There is this mindset in the veg game that starts have to be instant. My question is why? There is absoloutley no benefit to the engine firing as soon as you touch the key, in fact, the opposite is true.

On performance and race engines, they disable the ignition until the engine cranks sufficiently to get some oil pressure and then they power up the coil and off the thing goes. If you are consistently getting 3 second starts and the car fires up reliably, I would be very happy. This isn't too long to crank the engine and without doubt does it more good than harm.

One must remember that the engine was designed for dino not WVO or blends thereof. Just because it starts instantly on dino does not mean there is anything wrong when it dosen't start exactly the same on a blend. While it takes 3 seconds to fire from cold, I'll bet the hot starts are instant. When the engine is warm/ hot, the oil will flow a lot more freely and the oil pressure will come up very quick. Giving the engine a few seconds to get the oil moving before the stresses of a cold start kick in is only an advantage not a detriment in any way.

You MAY get faster starts with a different blend but it will be at increased expense of petro fuel and may also cause a deteriation of running performance when the engine is hot. ULP is going to be the most effective at making the starts easier but without doubt will also knock the performance off the most effectively. This is another reason I would lnot try to modify the blend for faster starts.

As the weather warms up and your cold starts are warmer, you can start backing off the kero. I run a 5% Ulp blend in summer and it worked very nicely as did a 25% Bio Blend. With the blend you are using, once the weather warms up and your start temp is 20-25, your starts will become more rapid but IMHO, your exactly where you want to be right now. I'd be backing off the kero a bit as the weather gets hotter to maintain the sort of start times your getting now and be satisfied your blends are right on the money.

David any specific ULP you use in the blend. eg. E10 or straight ULP.
Neil

[TroyH Senior Member Find all posts View Profile Close TroyH]

Re: Blending update

I think if you look up the BTU and heating values and work out the temp rise 1W of energy will give oil, You'll plainly see it is completely insignificant for our purposes.

I'm sure the scientists will chime in to correct my lazy maths but I believe that you are looking at about 1 watt per 1.5 o temp rise at that flow on oil. Maybe less.

You have to realise that a Watt is not a unit of energy, it is a unit of the rate of work (energy per unit time). 1W = 1 joule/sec

according to some info from the net, vegetables oils have a specific heat capacity of 1.6 Joules/gram/kelvin. The density of vegetable oils is about 0.92g/mL, so 25mL weighs about 23 grams.

So with a 25W heat source, you have a total of 25J/s*60s= 1500J available for heating.

Q=mCpdT
So 1500 = 23*1.67*dT
Thus dT = 1500/(23*1.67) = 39 degrees

So assuming that your flow is 23g/min of oil, that your injector heating coil is producing 25W of heat, and all of that heat is getting into the oil (which won't be happening), then potentially you could see a 39 degree change in temperature.

[TroyH Senior Member Find all posts View Profile Close TroyH]

Re: Blending update

Over the residence time in the "heat exchanger"

[craigcurtin Senior Member Find all posts View Profile Close craigcurtin]

Re: Blending update

Dave Jones - thanks for the update and feedback - your first line - (personally i wouldn't touch your blend) had me going !! I thought i had copied exactly what you were doing from earlier posts - then i got what you meant - my blend was fine ! Thanks !.

Troy, thanks for the clarification on what you have said - i think the potential for a better start is probably even better than what you have indicated as you have to also take into account the fact that you have a length of Injector line (say 300mm) which you would heat for a couple of minutes prior to turning on - so that first rush of fuel should be nice and warm.

I was also going to ask for clarification on another point - Dave Jones - mentioned that even if we heat the oil, the Injector will suck that heat right out into the engine block - i would have thought the amount of heat wasted to the block would be minimal and would be to do with the amount of time resident in the injector prior to hitting the swirl chamber (i.e. IDI not DI engines) ? Also theoretically the injector line heater should be actually adding some heat to the injectors also i would have thought. (again assuming i turn on for a couple of minutes prior to starting)

Craig

[TroyH Senior Member Find all posts View Profile Close TroyH]

Re: Blending update

Think about one thing, when you think about the injector "sucking" heat out of the oil.

The only way the heat can flow from the oil to the injector, is if the oil is warmer than the injector. Now, if you don't heat the oil at all, the oil is probably at the same temperature of the injector already (assuming you've been stopped for some time). If you do heat the oil, then the temperature at which the injector and the oil will come into equilibrium, will be somewhere between the original temperature of the oil, and the injector. So it will be warmer than if not heated.

To what extent it is warmer, will depend on a lot of variables. It has nothing to do with how you are heating the oil, only the temperature to which it is heated, and the flowrate.
Certainly the injector will cool the oil, but I imagine the injector would also be one of the first components heated by the combustion that is occurring?

[Johnnojack Senior Member Find all posts View Profile Close Johnnojack]

Re: Blending update

Think about one thing, when you think about the injector "sucking" heat out of the oil.

The only way the heat can flow from the oil to the injector, is if the oil is warmer than the injector. Now, if you don't heat the oil at all, the oil is probably at the same temperature of the injector already (assuming you've been stopped for some time). If you do heat the oil, then the temperature at which the injector and the oil will come into equilibrium, will be somewhere between the original temperature of the oil, and the injector. So it will be warmer than if not heated.

To what extent it is warmer, will depend on a lot of variables. It has nothing to do with how you are heating the oil, only the temperature to which it is heated, and the flowrate.
Certainly the injector will cool the oil, but I imagine the injector would also be one of the first components heated by the combustion that is occurring?

I did some calculations and confirmed Dave Jones quoted flow rates ( I got 30ml per minute) that equates to 4 /100ths of a ml per injection. Not a lot of oil. Take an injector, have a look at it, feel the weight of it. When it is cold and in a cold engine head that tiny flow of even very hot oil is going to make bugger all difference to it. While injector heaters may help I still think the only way to heat up injectors is by heating up the head first, ie running the engine up to operating temp. Why do we need hot injectors? To ensure good spray patterns and therefore combustion.

[TroyH Senior Member Find all posts View Profile Close TroyH]

Re: Blending update

Can't be any colder than without the injecter heaters tho, can it. :P

I couldn't quantify how much the injector would cool the oil, without knowing a bunch of factors. Thats why I was simply discussing the potential for heating the oil.

[Nuddy Senior Member Find all posts View Profile Close Nuddy]

Re: Blending update

Posted in another thread but this is about blending:
"Got on a boat mid-day Friday, home monday afternoon.
Friday morning on 75/25 blend the patrol would not start on the starter motor.
Rolled downhill and it started immediately I released the clutch and ran perfectly from cold. However hill starting only from cold is no acceptable so I am back to 50/50 for now. Left from Friday mid-day to Monday night and then started first kick on 50/50. I agree with David (written elsewhere) that it is better for the engine to crank for 3 seconds or so from cold rather than first kick with all the lube oil drained off and no pressure. I am thinking that I will in future crank the engine for 3 secs before cycling the glow plugs.
I will stick with 50/50 till I can get the 2 tank operating."

I'm still to phobic about petrol in the IP to run any petrol in my blend. Otherwise I would try 95% WVO and 5% petrol.

The patrol runs perfectly from cold on 75% WVO/25% distillate, it's only the starting from cold that is a problem. My troopy was quite happy on 100% WVO from 20oC engine temp but wouldn't start on it.
I believe that just minutes after starting the injector tips and thus the fuel injected are over 100oC.
As soon as I have the 2 tank set up I will experiment with how long I need to run on distillate before switching to WVO and get good clean running.

[Jeffrey S. Brooks Banned Find all posts View Profile Close Jeffrey S. Brooks]

Re: Blending update

I know when my 100w injector line heaters have stopped working because the difference in temp is about 20'C......and if left idling the temp will climb extra 40'C on top.
So what it amounts to is that you can't solely use current for heating.

I think the reason this works as it does and electric heating in the primary fuel circuit doesn't is because:
Each injector line is 25w. The amount of fuel movement in each line is a fraction of what the primary fuel circuit has to deal with. The total primary circuit fuel flow is 500ml per minute (typical Jap rotary IP). Each injector line fuel flow is somewhere in the region of 20ml - 50ml per minute.

If the flow is indeed 25ml. and the watts is 25, then each ml has a watt to heat it. Compare that to 500mls passing through the lift pump primary circuit, and trying to heat it with a 150w GP....no wonder it doesnt make much impact on temps!

So, we now get to the bottom of why your engine is experiencing vapour-lock on ULP blends. I would think a ULP blend would not need injector line heaters, so you could put in a switch to shut them off if you wanted to run ULP-based blends

[tbird650 Senior Member Find all posts View Profile Close tbird650]

Re: Blending update

Um, no, wrong assumption JSB. I haven't used those heaters since '09. They were for use with unblended svo which I quit at the time as well.
Blending ever since though. I'd also agree no heat is necessary or desirable with blends, especially so with ones with a ULP component.

[Jeffrey S. Brooks Banned Find all posts View Profile Close Jeffrey S. Brooks]

Re: Blending update

Um, no, wrong assumption JSB. I haven't used those heaters since '09. They were for use with unblended svo which I quit at the time as well.
Blending ever since though. I'd also agree no heat is necessary or desirable with blends, especially so with ones with a ULP component.

Then, I cannot understand where your heat is coming from to cause vapour-lock on your fuel system with blends containing ULP. There should not be significant heat in the engine compartment for returning fuel blend to cause vapour-lock of a ULP-based fuel blend, unless there is a significant heat source, such as a heat exchanger or fuel line heater.