Methanol Injection delimas 3

[pimpsmurf]

We are planning to run methanol as a secondary fuel source. I use secondary instead of supplemental (to gasoline) only because we plan to run so much methanol.

At this point, I'm worried that we might be going too far.

Engine:
2.5L bored to 2.6L QR25DE. 100mm stroke x 90mm diameter. Roughly 9.5:1 static CR. 20-25psi with some nitrous on top.

I'm worried. I was setting up the primary fuel system to handle 300 or so crank hp. The methanol will be direct port progressive. I believe we will need around 67GPH of peak methanol flow to make the 260ish hp we need to put us over the top.

I have a couple questions:

1) This is around 1.3CC, as best I can tell, per cylander, per intake event. Do you think this will vaporize in the 1/50th of a second between intake events? My intake temps are very close to ambient at 20psi maybe up to 5*F hotter. Coolant temps usually under 190F. Excellent ventalation for the turbo, and the intake is never over 130*F

2) This is a little more difficult. I've read on here that a wideband configured for 14.7 stoich when using multiple fuel sources will be inaccurate. My question is, perhaps I'm ignorant, but if I'm tuning lambda for .8, which is around 11.7:1 on gasoline and 5.1:1 on methanol, when my gasoline calibrated AFR display is showing 11.7:1, will this REALLY be my calculated stoich of 7.1:1? I'm not tuning by AFR alone of course, EGT, plugs, etc will be involved, but I wanted to be sure that the AFR gauge will function in the way I understand it to.

If I missed some critical information you need, please let me know! Any other suggestions are more than appreciated! You guys are great.

-JNY

 

[patprimmer]

When you compress it 9 times it gets hotter, and when you light the fire it starts to evaporate real fast. I strongly suspect the burning event is a whole bunch of very small drops burning just away from their surface as they evaporate.

In diesels the fuel is injected directly into the chamber as a liquid mist.

Top fuel with nitro methane runs A:F ratio of around 2:1 and it still burns, although be it a bit slower than alcohol or petrol, and it is somewhat harder to light.

You may find your methanol petrol combo harder to light than petrol so you will need a good ignition system.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[pimpsmurf]

Thanks for the rapid reply.

What do you mean by compress it 9 times?

I've considered running nitromethane, but that stuff even scared me when I was doing r/c cars. haha.

I do have a decent ignition system. Individual coil packs considered to be worth 500+ hp on gasoline. They seemed to do fine at 400hp, but I was running out of fuel and had to get out of it. I believe at the 18psi or so of boost, my fuel presure was going so high (1:1 regulator) that the pump couldn't handle the flow. I'm going to be getting a walbro 255 which should solve that problem.

I don't mind upgrading the ignition system as well, but I had planned on doing that when I put a trigger wheel on the car so my megasquirt can handle more than just the fuel system. I suppose if it breaks up and misfires, I will just have to go ahead and do that, since I've been unable to find an aftermarket ignition system that might work with the stock ECU's 4 12v signals.

-JNY

 

[patprimmer]

9:1 compression compresses it 9 times or thereabouts depending on cylinder pressure vs ambient at inlet valve closing point.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[pimpsmurf]

Ahh yes. I got you. I don't know what the hell I was thinking. haha. My typical EGTs are in the 1200-1400 range w/ low methanol injection. My idea was to go big with the methanol, but I need to be sure about question 2 above.

-JNY

 

[patprimmer]

The relationship between lambda and A:F ratio of different fuels has been discussed at length in previous threads. A google search of the site should find them.

Short answer, lambda is not measuring a:f it is measuring unburned or partly burned fuel in the exhaust or left over oxygen in the exhaust, or simply rich or lean for whatever fuel.

To control mixture in very high specific output engines with exotic fuels is difficult as the time lag between detecting lean mixture and correction can be long enough to burn a piston.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[pimpsmurf]

I understand all of this. I might not have worded the question propperly to get across what I meant.

Will configuring my wideband for gasoline (as it asks, even though I output 10:1-20:1 lambda on the 0-5vdc output) affect the lambda output? IE, will configuring a lambda sensor w/ a stoich ratio of 14:1 cause the output to say .8 lambda when it's really not?

We will be tuning via many methods. Primarily EGT and plug reading. The AFRs are more for an idea of where we are. We plan to tune very rich, perhaps .7 lambda and go up from there w/ normal methods. We aren't looking to push the timing limit of the engine, but get it on the conservative side of perfect.

-JNY

 

[patprimmer]

Lambda is lambda 1 no matter what a:r is stoich.

If you get Lambda 1 for14.7 on petrol you will get lambda 1 for stoich on methanol (about 6:1 I think from memory) or stoich on ethanol (about 9:1 I think)

If he gauge says 14:7 for lambda 1 on petrol and you are running methanol, the gauge wont know it, so it will still say 14.7 for stoich. Don't worry about the actul number, just wrry about rih or lean, ie lambda 1, or lambda 0.7 or whatever for ANY fuel.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[PowerTripp]

Is you methanol enrichment mechanical or performed via engine management?

If you are running methanol as an enrichment or cooling fuel on top of a gasoline based fuel, your target Lambda for best power will change at different rates of methanol flow. This is just like running at ever-changing ratios of mixed fuels.

You will need to find what works best at different loads and engine speeds by trial and error.

Lambda for gasoline, methanol, ethanol, etc. are similar at stoich. But not even all gasoline blends are the same. We race at far richer mixtures than stoich for best power. At best power mixture ratios the Lambda for each fuel WILL be considerably different. This is where those who do not (or have not) run alcohols or mixed fuels get confused.

The nice thing is that alcohols run well at richer mixtures before performance falls off than gasoline fuels.

On pure methanol, Lambda sensors are well out of their range for accuracy of tuning - even the LSU 4.9 sensor with a wider range cannot be trusted. Even the sensor's heater cannot keep up. This is an even larger issue with forced induction and its increased fuel requirements. You have to test and give the engine what it wants for best performance - just like the days before Lambda sensors.

And at higher rpm when you are really pouring in the methanol, the Lambda sensor/controller can lag behind the acceleration of your car by 1500 rpm or considerably more due to slew rates, distance from the exhaust valve, and all that.

On your turbo set up, the higher expansion ratio of methanol will produce more exhaust gas by volume. The more methanol you run, the larger the volume. This will spool the turbine more quickly, but if you are already pushing the limits of the unit, it may push it into higher speeds or higher pressure in the exhaust than you want. You may need to watch this closely.

I hope this helps.

 

[pimpsmurf]

Those are perfect posts! Both of you guys are awsome! Thank you very much.

OK. So this is the plan. Install an EG-Pressure gauge and monitor that closely. Installing a larger exhaust turbine housing may be in order. Start very rich on the dyno and pull fuel until torque plataeus for that area, then moving up the rpm ladder.

My main concern was that the AFR gauge will be accurate, which it won't apparently. Good to know.

Thanks again. great info.

-JNY

 

[pimpsmurf]

I forgot. Yes, the methanol injection is controlled via computer. It's from labantemotorsports, which I think is the original snow performance stuff. I'll have the digital flow meter, with the danger-output wired to a relay to disable the boost controller (ie, down to 10psi quick.)

It's not a great way of doing things (PWM on the pump, instead of a high speed solenoid) but it should work pretty well considering.

I plan to run 300whp worth of gasoline and 200 of methanol, at this point. I've installed the walbro 255-hp, with my 499cc (high pressure mopar) injectors which handle 80psi of base fuel pressure, should make for much more fuel. Hopefully I can tune 15psi with this setup. Then add the methanol and nitrous and another 5psi to make big power.

-JNY

 

[PowerTripp]

FWIW, almost all injectors will run fine at 5 bar/73 psi, and some will work at 7bar/101 psi. The Magneti Marelli Pico injectors are RATED at 10bar/145 psi.

http://motorsport.magnetimarelli.com/PDF/Fuel_System_Ignition_rev3.0_file/SF_IWPR_rev5.0.pdf

If you are forced to go up to 550cc injectors, watch out for the ones from RC. I really like RC, but I have seen a few of their 550cc units leak at 43.5 psi.

You mentioned the coils, what units are your running?
Are these coil-on-plug or coil-near-plug units?
There are big differences in coils for both inductive and CDI at higher combustion pressures and engine speeds.

 

[mattsooty]

Powertripp

Just read through this thread and couldnt help but notice a few misleading statements in one of your posts. I hope you dont mind me pointing them out: -

"Lambda for gasoline, methanol, ethanol, etc. are similar at stoich. But not even all gasoline blends are the same."

Arent the lambda values of all of these fuels exactly the same at stoich? ie lambda=1.

"On pure methanol, Lambda sensors are well out of their range for accuracy of tuning - even the LSU 4.9 sensor with a wider range cannot be trusted. Even the sensor's heater cannot keep up."

I know for A modern UHEGO sensor, especially Bosch LSU 4.9, should have no problem reading down to lambda=0.64, which is just over 4:1 AFR - I cant imagine any need to go richer than this. Also, the sensors heater has nothing really to do with its ability to measure Lambda. That functionality is down to the sensors O2 pump circuit (nernst cell).

"at higher rpm when you are really pouring in the methanol, the Lambda sensor/controller can lag behind the acceleration of your car by 1500 rpm or considerably more"

I have never heard of an EMS system that utilises closed loop fuel control during WOT acceleration, for the very reasons that you cite! The fuelling control during transients is always open loop hence no bearing on the lambda sensor or controller.

"On your turbo set up, the higher expansion ratio of methanol will produce more exhaust gas by volume. The more methanol you run, the larger the volume."

Is this right? Surely the more methanol introduced (past that which is involved in combustion) the more the temps of the exhaust gases will decrease, with a corresponding decrease in pressure? As explained by the Ideal Gas Law.

As I said above please dont think I'm splitting hairs and I certainly dont wish to offend.

MS

 

[Lou Scannon]

For what it's worth, I found mattsooty's points to be valid and well informed.
I'd be interested in clarification of the last point... the volume of the exhaust gas is constrained in the first place by the power cylinder (prior to exhaust valve opening), so I agree with the gas law analysis. But if there is more methanol (in the form of liquid droplets) in the trapped reactants, then the n in PV=nRT is larger. This would counteract a lower T in PV=nRT. So the net effect on P is indeterminate at this qualititive level of analysis.

 

[patprimmer]

MS

Thank you for the infusion of clearly outlined fact.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[PowerTripp]

Matt,
Please feel free to question any point I make - I am far from an engineer, and further from perfect. I can only relate from my experiences and limited knowledge.

Perfect stoichiometric conditions do not actually exist outside of the lab. It actually requires a specialized "gasoline" to be run in a test engine that uses intake heating to fully vaporize the fuel and elaborate mixture preparation to homoginize the mixture to get true stoich conditions.

In the real world, Lambda sensors are imperfect at reading Lamdba = 1.000. Bosch LSU 4.2 and 4.9 Lambda sensors/controllers are calibrated so Lambda 1 = AFR 14.57 not 14.7 to closer relate to actual gasoline mixtures in running production engines. The problem is that "gasoline" at the pump and various race gas blends vary so widely and require greatly different conditions for optimization that it is very hard to even define "gasoline". Add in the large differences of different alcohol fuels, different mixture preparation, different stratification, and different combustion events (mechanical and thermal) and things vary even more.

Using a Lambda sensor to determine actual Lambda is not very accurate. A lambda sensor has no way of actually measuring the air and fuel amounts entering the engine, it simply samples gases in the exhaust. Misfires that occur at low engine speeds or in lean conditions throw off these readings, as does the ignition timing and a few other issues.

In order to keep the gas samples within a known range of temperature the Lambda sensor's heater is used to offer a correction and widen the range in which it operates. As mixtures become richer or leaner, more unburned fuel is entering the exhaust, or the fuel's cooling aspects are involved, the exhaust gas temps can drop to a point where the heater simply cannot keep up, and the sensor and controller are no longer accurate. This can be WELL within the range that Bosch or NTK quote for accuracy of their sensors.

Some controllers/meters use the readings from the Lambda sensors differently, as well as the heater control. This throws another wrench into the gears when striving for accuracy.

The only way I know that we can actually get a reasonable accurate reading of mixture ratio is to use a multi-gas analyzer and use the Brettschneider equation. But this is an expensive option for most racers and even many tuning shops. But many of us have gone this route to improve accuracy greatly over Lambda sensors. But Lambda sensors still offer benefits that make them a valued tool.


Many (like the original poster) use Lambda at WOT as a tool for tuning the engine. This is different than EMS corrections. Some better EMS can use Lambda at WOT, but using Lambda is difficult for best performance at all loads and engine speeds. Most OEM EMS only use Lambda to correct for near-stoich at idle and low loads for pure emissions reasons to keep catalytic converters within their operation temperatures and mixture ratios that work well from an emissions stand point. Best performance and fuel consumption are found far from stoich.

Different fuel blends have different Reid vapor pressures, expansion ratios, and cooling effects. This means that the mixture preparation can vary greatly, as can the actual combustion dynamics of a given fuel in different engines at different engine speeds. If more fuel is making it to the exhaust in unburned liquid form, more expansion occurs in the exhaust. This is where ideal gas laws are made more complex.

When you add in conditions where fuel is used for cooling in forced induction engines, yet richer mixtures (especially with alcohols), can keep the engine alive, but add even more confusion to the issue.

I hope this helps.

 

[mattsooty]

Well yes, I suppose a lambda sensor is 'imperfect' at reading lambda - in the same way that a rule is an 'imperfect' way of measuring distance, however, both serve their purpose pretty well......

As I think Pat has pointed out before, whilst there is a direct correlation between AFR & Lambda, a Lambda sensor does not measure AFR - it measures O2 content (or lack thereof) in the exhaust gas. The calculation to AFR can then be carried out once you know the stoich. AFR of your fuel, which you hopefully you will.

I'm still very sceptical about your claims of overpressure in the exhaust from the prescence of liquid fuel. Unless of course combustion is occuring therein (which is doubtful because you mention running richer than stoich so no excess air).

Anyway, this debate is moving far away from the OP.

MS

 

[PowerTripp]

Matt,
Simply put, Lambda is a mixture ratio.
A Lambda sensor does not actually sample enough gases to give a true Lambda reading. It is a good tool, at a reasonable price, but it has limitations that need to be understood for best results.

Anyone can alter the Lambda reading displayed on a good meter with an engine held at a specific load and engine speed, by simply altering ignition advance and no changes in the actual air and fuel delivered to the engine. Do this on a small bore engine for even more variance. This means that the way we are measuring Lambda is suspect, not that actual Lambda is.

Using multi-gas analysis and the Brettschneider equation, you can see that just because O2% changed on a Lambda meter, does not mean that actual Lambda did.

I have yet to see an engineering paper where a thorough testing was performed using a Lambda sensor for measuring mixture ratios.

I cannot explain it any more clearly than this.


As for the differences in methanol in the exhaust, all I can ask is to perform your own testing, and determine the results for yourself. I am more than willing to accept that I am wrong by those who have results showing differences from mine. But the theory does make for an interesting discussion - as long as it is civil.

Based on question #2 of the original post, I feel that this discussion is still very much on topic.

After reading the forum policy and seeing the reception here to real world results and a disregard for accuracy, perhaps I am in the wrong place. As I am more concerned with accurate results than talk of theory.

-Wayne

 

[Lou Scannon]

PowerTripp, I think we all understand that the oxygen sensor is used to infer lambda based on the quantitative presence or deficit of oxygen, and has limitations doing this in different gaseous mixtures due to chemistry effects. If you really want to "know" the air/fuel ratio, I agree, you need more sophisticated measuring equipment.
Back to the OP, if you're going to use an oxygen sensor for tuning different fuels, that's fine, but the tuning target may and probably will change with different fuels due to the fuels' characteristics' effects on combustion (primary) and the oxygen sensor (secondary).

 

[mattsooty]

Must we......I really don’t enjoy games of ‘Thread Tennis’ you know!?

"A Lambda sensor does not actually sample enough gases to give a true Lambda reading"

So you would you not consider the exhaust gases in the exhaust system a homogenous mixture? Surely the amount of heat and turbulent flow would remove any chance of heterogeneity?

"Anyone can alter the Lambda reading displayed on a good meter with an engine held at a specific load and engine speed, by simply altering ignition advance and no changes in the actual air and fuel delivered to the engine. Do this on a small bore engine for even more variance. This means that the way we are measuring Lambda is suspect, not that actual Lambda is"

No, what this most likely means is that your Lambda sensor is incorrectly placed or that you are experiencing misfire. In the industry we go to great lengths to ensure proper O2 sensor placement, using all sorts of clever FFT software to validate this. In my years doing exactly this sort of thing, ad nauseum, I have never witnessed the phenomena to which you refer.

Seriously, arguing whether lambda sensors are good or not, is rather a moot point, dont you think?

I'm quite happy using good old lambda sensors (LSU 4.9 Advanced in the current application) in my quest to meet EU5 and ULEV2, along with every other OEM - so I dont suppose they can be all that bad. Unless of course you know something we don’t???

"After reading the forum policy and seeing the reception here to real world results and a disregard for accuracy, perhaps I am in the wrong place. As I am more concerned with accurate results than talk of theory."

Have you thought that you might be coming at it from the wrong angle? There are some very knowledgeable people on here, for whom I have a great deal of respect, who know what they are talking about. They, like I, are professional engineers who know the theory behind things, have seen it for themselves and also do it for a living. Whilst it may be the case that you also fit into this category I will withhold judgement for the time being, thanks.

MS