Ignition timing for Methanol vs Gasoline 2

[brobards]

My company has recently built a drag car that uses methanol fueling and high boost pressure. We are having some problems with burning through the head gasket, which I believe is due to an over conservative timing map.

Some info on the engine are: 3 liter of displacement (Toyota 2JZGTE), 40+ psi of boost pressure, 11:1 static compression ratio.

The timing that we used was similar to what we run on high octane leaded gasoline.

Some questions I have are:
1) How is the ideal timing of methanol compared to that of high octane leaded gasoline?

2) Could not having enough timing cause the combustion temparatures to reach a level which causes the head gasket to burn through?

 

[sbc438]

Brobards,

There are many things that can be causing this issue. More likely than not you are pushing the gasket out then burning it or the head.

We run a traditional Chrysler Wedge motor 526 ci on methonal @ 37psi from a roots blower. Our timing is 32 degrees advanced with 10:1 static compression. Not gasket issues. We use copper o-ringed gaskets and had to run 1/2" head studs to get enough clamp load on the gasket.

If I had to bet you are producing too much cylinder pressure and pushing the gaskets. There are many ways to fix this but you first need to know if you are detonating or if you need to upgrade parts to handle the boost.

More info may help me give you some direction

 

[brobards]

We are running the stock Toyota head gasket, but I am aware of other people that are running the same gasket on methanol with no problems.

The head studs are stock sized (7/16" I believe) but were upgraded to ARPs L19 material.

The timing was about 6 degrees advanced at 40 psi and 8500 RPM.

One thing that we noticed was that we were melting the ground straps off the spark plugs which leads me to believe we were experiencing pre-ignition.

Could our timing be too retarded and lead to high compression temperatures, pre-igntion, and melting the head gasket?

 

[sbc438]

How do the rod bearings look? If the chamfer on the bottom bearing half 180 out from the rod beam is being hammered out you are experiencing detonation for sure. Any ring issues? Look for missing chromoly on the top ring this also indicates detonation. From your coment on the ground straps it sounds more like a lean condition.

If you were to far retarded you would have high exhaust temps and be in danger of burning a valve, damaging a turbo, and overheating the engine. Is this a turbo car or SC.

Burning the head gasket is the least of you worries here!!! You are in line foe some seriuos piston and head damage if your burning ground straps off plugs!!!!

On our rig we don't even take 10% of cadnium plating off the ground strap.

More detail on the set-up would help

 

[brobards]

We are waiting to get the car back before we can tear into the engine, as it is currently getting a new intercooler installed.

We definately are not experiencing a lean condition as our datalogs showed that we were tuned at about 0.65 lambda.

This is a turbocharged car.

For reference we also have another race car running methanol which uses a Mitsubishi 4G63 engine which has more material between cylinders than the Toyota 2J engine. We initially had similar timing curve in the Mitsubishi as the Toyota engine and found that by advancing the timing 10 degrees we were able to obtain an additional 100 hp on our dyno (540 vs 645).

What I am really wondering is how much more aggressive you can be on the timing with methanol vs. Race gas?

 

[sbc438]

Unfortunatly I don't see a cannned answer for this one. So many things are nvolved as I'm sure you know (cam timing, ignition timing, piston geometry, chamber geometry, ect).

If it were me I'd recurve the timing to a safe point and add some fuel just in case. Then creep back up on the tune-up.

Just for my knowledge, what's the .65 lambda mean? We are restricted to mechanical FI and can only monitor EGT's on the car.

 

[DynoTuner]

methanol on a drag car should be tuned at 4 to 1 afr.... your afr of 9.5 to 1 (.65 lambda)is too lean.

 

[patprimmer]

Stoich for methanol is 6.4:1

0.65 lambda for methanol is 9.85:1

At 40# boost and 11:1
you need to be quite rich to suppress detonation.

a:f of 4:1 is lambda 1.6 which is very rich.

I would think a:f of 5.0:1 which is lambda 1.28 should be rich enough.

9.8:1 is so lean I am surprised it ran at all. If it has only blown the tips of the plugs and blown a head gasket, you have been very lucky.





Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NCShane]

lambda=(AF actual/AF stoich)

so lambda = .65 is an AF of 4.16

 

[DynoTuner]

I've got a car that runs 8.2 in the 1/4 consistently. 1000 hp, 20 #'s of boost on methanol.

it's tuned to 4 to 1 afr. What's good on paper isn't what works in the real world.

when I multiply 14.64 by .65 I come up with 9.55.

How do you get to 9.8?

 

[DynoTuner]

I'm sorry, when i multiply 14.64 by .65 I get 9.516.

14.7 multiplied by .65 is 9.555.

 

[brobards]

You have to multiply .65 by Methanol's stoich A/F ratio which is 6.4

.65*6.4 = 4.16

You are thinking of gasoline's stoich A/F ratio.

What I really need to know is what type of additional timing we can add with the methanol vs. Gasoline. Is there a rule of thumb like: with methanol you can add __% more timing??

 

[NCShane]

I can't say that I have any experience with methanol. On E85 we run about 3-4 degrees above base timing on an NA engine. I would think that 6 degrees total (is that total or on top of your base timing??) wouldn't be nearly enough. EGT's will definitely get high if have too much advance or too much retard. Do you have the ability to monitor EGT's on your dyno? That's how we used to tune our ignition map.

 

[patprimmer]

I quoted another internet post that lambda is A/F stoich divided by A/F actual. It was from an unreliable source and I did not verify, so it could be (most likely is) wrong, so I will accept your version.

brobards

How do you know the lambda reading. Is it average, maximum or minimum. Is it dyno or track data. Is the gasket and plug burning at the track, dyno or both. You might have a fuel supply to the engine problem that only occurs part way down track caused by something like collapsed or restrictive fuel line, g force on the fuel in the line, restrictive fuel filter, uncovering the fuel pickup, aeration of the fuel in the tank from poor return line design, inadequate tank vent.

You might also have bad methanol with jelly like lumps, to much water or corrosion by products causing an instantaneous temporary lean out.



Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[brobards]

A/F was fine as we have logged every pass that was made with the car whether it be on the dyno, or track.

 

[patprimmer]

Is your oxygen sensor accurate and working as designed.

I am asking because you should not be blowing tips of plugs and burning gaskets at that timing, CR and boost. You should be close to the limit, but not past it.

With a 4" plus bore and wedge head, high 20s, low 30s deg timing is conservative. A pent chamber central plug 4 valve with low to mid 3" bore should need maybe 10 deg less timing, so I would think 15 deg would be a good starting point, BUT THIS IS A GUESSTIMATE not based on specific experience with a similar engine to yours.

If I were you, I would be very keen to see the piston tops and valves.

i think this was already mentioned, but how high is the exhaust manifold pressure, is it higher than boost pressure and do you have a lot of valve overlap, allowing a lot of hot exhaust gas to flow into the chamber and overheat the charge and cause detonation.



Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[DynoTuner]

Brobards in answer to your timing question. My drag car has timing at 45 degrees btdc.

I really don't think timing is your issue, you need more fuel. the huge amounts of fuel being run through the intake will cool the motor down so much that detonation should be non existent, allowing gobs of timing.

You should be shoving enough fuel through the motor that the intake will frost up.

The plugs should allways look clean, like brand new. The only thing you should see on the plugs is slight discoloration down the electorde side strap towards.

 

[patprimmer]

I tune methanol fuelled engines by reading heat discolouration of the plugs in the thread area and the electrode. You need cad plated plugs in silver or gold colour to do this.

I look for the plating to be burnt off of 3 threads on the electrode side of the plug with less at other points around the plug, and the earth strap to have gone shiny and discoloured to just before the bend.

A/F ratio has more impact on heat in the thread area, and ignition timing has more impact on the earth strap, but adjusting one will effect both to some degree.

This method only shows the maximum heat reached during a run, not the average or what variation.

A data logger with EGT will show variations along the track but are not reliable re actual mixture, just good for cyl to cyl or for variations during the run. O2 sensor also useful. Very good for A/f ratio, but not for indicating chamber condition during combustion. Also I think they react a bit slow, so not as good as EGT for indicating exactly when change happened.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[nextgen03gt]

Hello,

I have been running methanol injection in our supercharged and turbo charged 2.7L Hyundai V6 engines as an octane booster for higher boost levels on pump gas, 93 octane. I understand that gasoline is 14.7:1 stoich and methanol is 6.4:1 stoich. When supplementing approximately 20-30% of the gasoline with methanol and we look at a wideband that is calibrated for gasoline, the wideband shows extremely rich. If I tune the car to 12.2:1 A/F with the added methanol, how do I figure out what the actual A/F ratio is with the addition of the 25% methanol. I was told that even though I see 12.2:1 A/F on the wideband, the mixture is actually leaner than what I am seeing because of the difference in stoich between the two fuels and beacause the wideband is calibrated for gasoline. Can anyone help me understand this a little more cleary with some sort of formula that I can use to calculate the actual A/F? I would greatly appreciate it.

Thanks T.C.
Next Generation Motorsports

 

[NCShane]

The combined A/F is simply %A/F 1 + %A/F 2
So for 20% methanol, .2(6.4) + .8(14.6)= 12.96
This still doesn't help you since your A/F meter is calibrated for a stoich. ratio of 14.6. You can set your meter to read Lambda, then multiply by your combined A/F ratio to find your correct A/F.