Diesel fuel possibilities
Diesel fuel possibilities
(OP)
I have been on the hunt for a buddy who runs truck pulls and was curious on what I could do to improve the burn cycle by engineering a performance fuel. I had seen Mr Primmer mentioning Acetone does help, however I believe it kind of dries out the Diesel fuel since it is a solvent. In turn needing a lube additive no matter what. I had the idea of Biod for its lube properties and high Cetane quality.
The ideas I have had so far are using BioD, methanol, ethonal or another that could be mixed in. But, some are saying I will need some equipment to mix it properly and efficiently on whatever I decide on. I believe methanol can only be injected, assuming ethanol is the same way? Along with other additives, I would like to use another actual fuel if I can.
Any insight would be greatly appreciated!
The ideas I have had so far are using BioD, methanol, ethonal or another that could be mixed in. But, some are saying I will need some equipment to mix it properly and efficiently on whatever I decide on. I believe methanol can only be injected, assuming ethanol is the same way? Along with other additives, I would like to use another actual fuel if I can.
Any insight would be greatly appreciated!





RE: Diesel fuel possibilities
Regards
Pat
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RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
For a gasoline engine to produce more power generally the biggest constraint is the amount of air that one can cram into the combustion chamber - the limits being rich misfire & the knock limit.
With a diesel its more of how much fuel you can get into the cylinder and burn quickly & efficiently - the limits being exhaust temps & smoke.
The main attribute of a performance gasoline is its resistance to knocking (high octane number) whereas for diesel, which runs with excess air, it is the reduction in ignition delay of the fuel (high cetane number).
It is useful to remember that the combustion in a gasoline is laminar->turbulent whereas in a diesel it is a diffusion flame.
MS
RE: Diesel fuel possibilities
- Steve
RE: Diesel fuel possibilities
MS
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
MS
RE: Diesel fuel possibilities
http://www.chipit.com.au/product-info/diesel-petro...
RE: Diesel fuel possibilities
Things I have come across are Methanol seems to be the one most widely tested with diesel but has been known for eating up seals n the fuel system, although there are some that have done something with ethanol and diesel. Winfieldblue, thats what I am trying to achieve a faster burn cycle without reaching knock. If I remember right Methanol has a Cetane rating of 3.
I want to use a base fuel of No.2 Diesel because it has more BTU than No.1, but it, No.2, has a lower Cetane rating, thats where I need to improve the fuel. Now we haven't done any observing of the crown as far as just running with No.2 or 1 so I don't have any visuals to see. he is running around 3000rpms right now and the new engine will be between 3000 - 5000 operation range.
One person had mentioned microemulsion for mixing up fuel, then I will have to consult the manufacturer on if its safe to run a emulsified fuel in diesel, The only thing I have to think on some more is BioD, methanl and Ethanol are oxygenated which have less BTUs compared to Diesel, I had the thought of gasoline run by me on another forum, that brought the thought up of buying non-oxygenated gasoline, unless the oxygenated gasoline or methanol or enthanol will be benefit due to its cooling qualities because of the latent heat of vaporization since diesel is low in that department. Albeit, the diesel combustion phase is quite quick, so I am not sure if that characteristic will have an effect on horsepower production.
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
High cetane number means short ignition delay in premixed regions & effectively shortens the burn duration, with the charge being consumed, via diffusion flame, quickly & progressively.
RE: Diesel fuel possibilities
Leaner than stoich makes it irrelevant, why waste fuel volume with something you aren't short of in the first instance.
Reduced ignition delay means potentially more fuel burnt more quickly, giving a mre progressive heat release but, with CR, allowing for better control thereof. Only issue then becomes gradient of rate of pressure rise. Much more than 3bar degree becomes harsh & inefficient.
Ms
RE: Diesel fuel possibilities
So it would be better to use a non-oxygenated gasoline with a low octane like the basic grade 87? or would it be beneficial to test different grades up to 93 octane etc for mixing with No.2. Since these pumps get turned up, I think we aren't in a lean situation, I would say more around stoichiometric or slightly richer.
Yes, in the general sense of reducing the ignition delay along with probably adjusting the injection timing point is what I am looking at.
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
if you could get your hands on some GTL diesel fuel,that would greatly help in your situation.
GTL diesel is made from natural gas,it has 30% more lubricity than ordinary diesel,it has a cetane rating in excess
of 65(depending on origin,Shell claims up to 70)
now the problem ,i don't think GTL is available in the USA.
however it is widely used in Europe,either straight or mixed with oil derived diesel fuel.
i think i saw an info sheet from Shell that said GTL has more BTU/LB than regular but cannot recall how much.
i hope this does not cause too much confusion for you.
just an aside,you can increase the density of GTL by cooling it,it has no wax in it so it
so it will not cloud up,and the viscosity changes very little.
you could really max out your fuel flow this way..
RE: Diesel fuel possibilities
From memory, it has just over 1/2 the btu per lb but needs to be a bit more than twice as rich at stoich.
That is why I kinda tongue in cheek mentioned nitro methane earlier. It has a huge amount of btu per lb of air, like about twice that of typical hydrocarbon fuels, but it is 1.9:1 air fuel ratio at stoich. I have no idea as to its cetane or burn rate or autoignition point or how it mixes with diesel fuel or how it lubricates fuel pumps and injectors.
Regards
Pat
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RE: Diesel fuel possibilities
It's must be borne in mind that the charge will be heteorogenous in nature & burn only occurs in areas that are locally combustible.
As for lubricity. Not my bag.
MS
RE: Diesel fuel possibilities
I realised that, but I have no idea of the cetane for nitro or if it can be mixed to give an optimal cetane. I just threw it in their for discussion. It is an unlikely fuel additive for a diesel as they are normally chasing BSFC not power density and of course nitro is great for power density, but really bad for BSFC. Also it needs to run so rich, it can be in danger of hydraulic lock even at 10:1 so more like 20:1 certainly won't help in that regard.
Regards
Pat
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RE: Diesel fuel possibilities
My understanding is that, as a combustion system, heterogeneous charge compression ignition engines are still very much pigeon holded & are yet to break into the performance game proper - hence a lack of literature.
Ms
RE: Diesel fuel possibilities
Matt & pat if I had a used up engine I could test and not worry about melting things, I would be already running mixtures of this or that and see what happens. Any other thoughts, I appreciate this insightful discussion guys!
RE: Diesel fuel possibilities
No problem. I certainly did not take it as patronising. Many SI engine guys know little of CI, myself included and I know that I don't know and I am always eager to learn.
Your posts are some of those I really look out for as they often contains gems I was unaware of.
Regards
Pat
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RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
rmw
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
I think the development effort of engineering a 1-off methanol engine for tractor pulls is not justified by the return in performance, compared to the traditional methods of more boost, more fuel, & beefing up the mechanicals as needed.
Assuming fuel rate is not a limitation, the goal is to get the highest oxygen density in the charge as possible and match it with fuel, up to the engine's mechanical limit. Other than boost, you can increase the oxygen density by fogging with nitrous oxide, or even pure oxygen. I would caution against pure oxygen though; too many hazard and I doubt it would be allowed at the race course anyway.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
At any rate, compression ignition engines do not have a detonation issue, under any normal conditions.
There is no particular technical disadvantage with using a glow plug (i.e. to assist ignition in a compression ignition engine), but if the engine is not designed for glow plugs, they will be difficult to add after the fact. Glow plugs are designed for intermittent use only (starting, idle, & low load). Even with methanol they are not necessarily required 100% of the time, but the required glow plug duty cycle with methanol will be high compared to diesel (especially direct injection engines, which have no glow plug, so the diesel duty cycle is 0%). Using glow plugs at higher than the intended duty cycle will accelerate their demise.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Diesel fuel possibilities
RE: Diesel fuel possibilities
However as I understand it the problem with lack of power etc. from a diesel is its slow rate of fuel burn and consequently the engine's lack of ability to use up all the available oxygen. This is apparently mainly due to the particle size of the injected fuel droplets.
Why not inject the fuel at a very high temperature? Not high enough to cause coking problems but hot enough so that the the injected fuel immediately flashes into a vapour form (not droplet form at all) and the high temp also would increase the burning rate.
I realize that there would be a few technical problems - the fuel could only be heated just before it enters the cylinder, the injectors would need to be able to operate at a very high temp etc. - but the problems would not appear to be particularly insurmountable. Has it ever been tried?
You could even extend the idea to the direct injection of petrol into a typical SI engine with a CR of 10:1 or so - without the spark ignition operating and the fuel igniting because of its high temp. as it enters the cylinder - load control being by the amount of petrol injected, the engine operating at WOT.
RE: Diesel fuel possibilities
I watched one of the top Prostock tractors in the country last night, boy does that engine sing when its at WOT.
BigClive, good thought on heating the fuel to promote vaporization, but, then if we raise the fuel temp above normal engine operation temp we should take into account how the wear of the injector and other components would be effected in result of raising the temperature.
Another thing we will have to look at would be our piston crown surface finish to help keep our fuel off and from puddling if impingement is a problem.
RE: Diesel fuel possibilities
State of the art common rail systems are now operating in the 30,000 psi range. I have no idea how much higher would be needed to get the same penetration with vapour, but I suspect it would be a pretty tall order to develop a pump and injectors to do this.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Diesel fuel possibilities
IDI engine technology requires a pre combustion chamber to ensure the atomised fuel vapourises and initiates combustion within the comparitively oxygen rare confines of the chamber before emerging through the pre combustion chamber port, ricocheting off the specially shaped piston crown, mingling with chaotically swirling/tumbling air, and combusting with the oxygen present
Modern direct injection diesels employ high injection pressures & electronically controlled injectors, whose low mass components and nozzles with multiple, comparitively minute orifices ensure fuel is atomised into ever finer droplets, whilst delivering as many as 5 distinctly separate "puffs" of fuel per combustion cycle
The purpose of multiple injections is to create a minute space within the combustion chamber where fuel and oxygen may combust, into which the next batch of atomised fuel is delivered
The freshly injected atomised fuel introduced into that high temperature, oxygen depleted environment has sufficient time to completely vapourise before mingling and combusting with oxygen in the "fresh" air it soon encounters, thus simulating the dynamic of a pre combustion chamber - - without its disadvantages
Regardless of pressure, calibration, phasing, and droplet size, continuously injected diesel fuel lacks the opportunity to vapourise, homogenise, and combust as effectively as IDI and multiple injection DI systems
For proof, look at the trends exhibited by manufacturers whose contemporary diesels are employed in everything from passenger vehicles to road transport and industry
Tekton
RE: Diesel fuel possibilities
If what you say is correct, wouldn't GDI SI engines have the same problem?
RE: Diesel fuel possibilities
Indirect Diesel Injection engines, though rapidly being superseded by the direct injection designs permitted by superior materials, machining, and electronics technology, are non the less still specified for many industrial power plants where low noise levels and durability - - when in oe form - - are desired
However, Worldwide millions of crudely maintained and modified IDI engines are dying a premature death whilst hastening ours due to the excessive exhaust emissions they produce when carelessly - - or deliberately - - maintained or modified
Tekton
RE: Diesel fuel possibilities
So, question for Tekton: what is a typical penetration distance required by current technology common rail diesel injection (maybe as % of bore diameter)?
The problems with GDI injection are not the same (and probably not as difficult, with respect to injector & pump design, since the desired results can be achieved with a fraction of the rail pressure compared to common rail diesel). Typically the goal with GDI is to have the charge preparation complete (or nearly so) at the beginning of ignition. That means mixing all of the fuel with enough oxygen to ensure complete combustion. Note that this applies to both homogeneous and stratified charge combustion. That said, penetration distance is a key parameter with GDI injection and is one that a lot of effort goes into ensuring suitable penetration under the obviously very wide range of speed/load operating conditions.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Diesel fuel possibilities
I became acquainted with IDI components and combustion technology during general study a generation ago, then intimately in the late 90's when developing a range of pre combustion cups and belatedly recognising no comparative information was available for parts stockists and service personnel
This attachment is one of many intended to educate the above and expose the rampant use of incorrectly dimensioned parts such as those responsible for the Mitsubishi exhaust emissions
A complementary series of component dimensional listings etc was also developed
"Engine Technology International" keeps me informed of current trends
Fahlin Racing, my apologies if I've sidetracked the thread
Tekton
RE: Diesel fuel possibilities
Within an SI engine, operating under normal conditions, the sequence is: -
Mixture Formation - Combustion Initiation - Kernel Formation - Rapid Combustion - Exhaust
A homogenous charge is formed within the cylinder volume, either through fuel being introduced into the air charge, remotely from the cylinder, or injected directly within the cylinder.
Upon firing the spark plug, a laminar flame spreads from the spark plug electrodes and a roughly spherical flame kernel is formed. This then quickly develops into a turbulent flame, due to in-cylinder gas motion; with this motion increasing the burn rate of the charge. All before the end gases auto ignite and cause Detonation.
Within a Common Rail Direct Injection CI engine, again under normal operating conditions, the sequence is: -
Start Of Injection - Ignition Delay - Premixed Combustion - Mixing Controlled Combustion & EOI - Late Combustion - Exhaust
After the start of injection, directly within the cylinder, a heterogeneous charge is formed by way of a jet of high pressure fuel at the edges of which liquid fuel sits in suspension as droplets, slowly evaporating within the relatively low in-cylinder temps.
Around these droplets sit local pockets of vapour, some of which possess an AFR within the combustible range. As the compression stroke continues the temperature within the cylinder increases and these combustible areas begin to do so, spontaneously. This Premixed Combustion can and does occur simultaneously in many different areas at once and is, in some ways, analogous to detonation in an SI engine, with a rapid rate of pressure change. This is associated with the characteristic Diesel Knock/Combustion Noise & damage to engine internals.
The Premixed Phase develops into the Mixing Controlled Phase; as the fuel continues to be injected the pressures, temps, charge kinetic energy & rates of evaporation all increase. The rate at which the fuel is burnt relies upon the fuel molecules being exposed to O2 in the correct ratio with which to react and the formation of areas of combustible AFR mixture. This is a function of the available O2 (boost pressure & internal EGR) and in-cylinder charge behaviour i.e. rate of evaporation/fuel quality.
So, for a given CI engine & fuel type, to increase the torque produced the mass of fuel injected is the dominant factor and is a function of (Rail Pressure, Injection Duration).
The Injection Duration (SOI to EOI) is always constrained by the following: -
SOI
The piston must be near enough to TDC to allow the injected fuel to be within the bowl of the piston and not impinge on the relatively cold walls of the cylinder – or some of the fuel is wasted.
With this as the maximum, the advance of the position of SOI towards such is also further restricted by an increase in Ignition Delay. This is due to charge temps being too low to promote vaporisation, and therefore combustion, leaving the fuel ‘sitting around’ waiting to be combusted. Which, when it does, tends to occur in one bulk reaction.
EOI
For good mixing & therefore combustion to occur, the EOI must occur before the injection spray misses the piston bowl where gas velocities begin to slow drastically (bearing in mind reduced O2 & increased EGR). Good combustion therefore begins to rapidly diminish, as the piston moves towards BDC. Another constrain on EOI is the increase of exhaust temps due to slow reacting fuel.
Once the above constraints are encountered the only way to achieve more torque is to inject the fuel at a higher pressure with a corresponding increase in boost pressure (available O2 & compression).
More boost pressure means more available O2 and higher compression temps with a decrease of Ignition Delay but an increase in rate of overall pressure rise, a higher peak pressure and a shorter combustion duration – certain provision can be made to offset this by intercooling the boosted charge. Exhaust temps are also reduced (analogous to advancing the spark in an SI engine) as the burn duration is reduced. However, the increase in rate of pressure rise can be, as mentioned above, very damaging to engine internals in the same way that knocking in an SI engine can be.
So, in a nutshell, the challenge is to be able to inject enough fuel between the piston position constraints of SOI & EOI without an excessive Ignition Delay and provide an acceptable rate of pressure increase during Premixed Combustion. Whilst moderating the rate of pressure rise and decreased burn duration during Mixing Controlled Combustion but reducing the high exhaust temps that occur (the Late Combustion) due to the excessive fuelling by increasing boost pressure/reducing charge temps.
And that’s before we start talking about smoke…..
See why I hate Diesels?
MS
ps please attribute any typos etc to the few G&Ts I've imbibed, just to wet the whistle!
RE: Diesel fuel possibilities
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Diesel fuel possibilities
I think Navistar did a bit of testing using the additive DME (dimethyl ether) a few years back. There is at least one SAE paper documenting the effort. I think I also recall that the engine demonstrated a lower BSAC (Brake Specific Air Consumption - Pat's point much earlier in string).
Dick
http://papers.sae.org/950061/
RE: Diesel fuel possibilities
I got a 1990 Pajero with a blown engine and rebuilt with a donor block - new pistons, reground crank, every bearing etc, and used the original cyl head as it was undamaged. This was at 210,000km, injector rebuilt and pump set with DTI, EGR blocked. I thought it went as well as any I've driven, and going over a certain hill into Auckland would only just stay in top gear and converter lockup....one passenger and it would kick down. At 270,000km this head cracked in the combustion chamber - fair enough I thought, it had been overheated several times (customers car) until finally running out of oil.
I fitted one of these replacement heads as they were cheap and uncracked OE heads non existent. It was down a little on power, and the temp gauge erratic - it lasted 3 weeks and 3,000km. They supplied another, it performed the same and lasted 30,000km...out of warranty. Both heads cracked below an inlet valve seat, so not a normal cracked head symptom. I suspect a thin casting in that area.
By now I had sold my workshop and was working in a Mitsi dealership, and was able to use a good head taken from an NZ new L200....just needed a cam cap repair. The difference in performance was stunning - now I was rolling off the throttle up the hill to stay under the speed limit, and would pull a full load of 7 adults without kicking down. As the heads looked identical I suspected it was different pre com chambers, but as this was all in hindsight there was no way to check without pulling the head again. I had rechecked the pump timing with DTI, and it was still the same. Black smoke was a lot less, but as we had gone to ULS diesel and smoke is down across the board I can't confirm that either.
RE: Diesel fuel possibilities
Turbomotor, thank you for the link! Again, everyone who has contributed I greatly appreciate the insight and help.
RE: Diesel fuel possibilities
Mr Lada, with the hundreds of thousands of Asian IDI engines manufactured, the total lack of oe technical data to permit ready identification of sibling components and, shall we say "misinformation" provided by aftermarket suppliers, I've not the slightest doubt tens of thousands of fellow motorists have suffered similar experiences
A scandalous situation World Wide: so far as Australasia is concerned and NZ in particular, regional authorities and politicians were well aware of our studies, some of whom received hard data such as the Uniservices generated report which they chose to ignore despite irrefutable air care studies, one of which states " - - air pollution claims at least 486 premature deaths per year in the Auckland region - - 253 are due to motor vehicle emissions"
Here I need some guidance: I'm willing to post technical data including the dimensions and internal volumes of the IDI component we nicknamed "Conductor of the Combustion Orchestra", the pre combustion chamber cups - - well over 100 of them
This and other information was distributed throughout Australasia through the late 90's to mid 2000's, but never IT accessible - - the copywrite Uniservices Report has never previously been released to the public or posted
However, the Steinz Manufacturing data was generated for Engineering and Marketing purposes - - perhaps disqualifying it from Eng-Tips?
If not, anyone care to suggest a thread title?
Tekton
RE: Diesel fuel possibilities
Here's the link I meant to post:
Tekton
RE: Diesel fuel possibilities
I did use a pipette to measure the pre coms on a 4JG2 engine - I was fitting the wrong model head, but my engine guy knew we had to get the pre coms right for it to work. Otherwise, we get what we are given, and assume someone else has got it right. I didn't want the heads I was supplied, but there was no real other choice.