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Timing for egt’s

Understanding AFR

Discussion and questions related to the course Understand AFR


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Hey Andre I just hopped aboard here on your horsepower Academy. I had a question about a correlation or relationship between Lambda numbers and egts. On my combination I have a small on methanol and turbocharged. In 6 to 12 PSI boost range my Lambda readings are in the low 7's to High 6's but my EGT readings are 1300 degrees Fahrenheit sometimes more. My timing in that range is 34 34 degrees. Now I'm wondering with my Lambda AFR quitequite on the rich side why is my egts going over 1300 degrees. Does this mean that I need more timing? I just posted up my timing table.

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Not played around with methanol, as a fuel, but you are mixing up two different things there - the lambda is going to be somewhere in the 0.5-0.6 range, IIRC (and I most likely don't), with the AFR (NOTE! there is a different correction factor for different fuels from the lambda that is used for the raw data) around 3-4:1 with 'excessively' rich mixtures having little affect on power/torque but lean mixtures causing high exhaust temperatures.

Andre has some more information from his experience with methanol and i suggest you have a good read through all his comments on that, and any other information you can find on-line - bottom line is you will be paying for any repairs, so the better informed you are the better.

First thing I would suggest is checking the fuelling as, while relatively late timing will increase exhaust temperatures, you need to know if that is actually the problem as you should have already set that by the best torque results.

Bit of a long shot, but could you be using too small a hot side, that is holding too much hot gas in it?

I just posted a screenshot of daddy Dave egts. He has eight of them across his dashboard.

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Back up for a second.

What is the engine? What is the vehicle? What modifications and what ECU (looks like Megasquirt) ? When you say it's methanol... like an M100 blend ? What kind of usage for the vehicle? Drag racing?

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OK, found the thread I was looking for, I think, where Andre addresses the AFR/lambda for methanol - https://www.hpacademy.com/forum/understanding-afr/show/methanol-afr-idle-mid-and-power-range-afr

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To backtrack, if your (corrected) AFR is high 6 to low 7:1, then it is on the lean side which will certainly contribute to high EGRs - especially with a turbo' holding heat in the manifold. Bump it up to around 5.5:1 (0.85 lambda) and see how much of an improvement that makes - you should also gain noticable torque/power at that. If required, it would seem that you can run actually run significantly richer than that, even reports of 3:1 working well, to reduce exhaust temp's with some loss of power.

Oh, remember that oil dilution is going to be significant, so regular changes are a MUST!

Here is a screenshot showing my EGT numbers and Lambda number.

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Here's another screenshot showing the high and low of my egts

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What is the engine? What is the vehicle? What modifications and what ECU (looks like Megasquirt) ? When you say it's methanol... like an M100 blend ? What kind of usage for the vehicle? Drag racing?

This is a ford 351 Windsor v8. It runs on pure methanol. It's a 70 Mustang made for drag racing. It is a ms3x with can-EGT.

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Please, next time you upload a graph:

Graphs need to be clearly labeled as to what each channel is so people know what they are looking at.

Graphs need to be scaled appropriately so that we can see the relevant range and how the trace moves up and down.

That being said, the "max" indicated on your screenshot was 1462F. Where is that measured? Before the turbo or after?

It is measured before the turbo about 3 inches past the header flange. Here's another screenshot showing what EGT is what. Is there a way to upload my log file on here. That way you guys can view the whole data log.

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My whole question here is if I Advance timing under boost (15 psi) will that lower my egts?

And the answer is 'maybe' - but you are running lean, which is more of a problem...

If you advance your timing enough you will lower the EGT's. You might not see it with a degree or two due to the normal fluctuations of exhaust temps.

1462F is about 800C and is not hot for pre turbo. Your Grandma's Ford Escape will run over 1700F. The turbo will take 1700F no problem, however if you are concerned about heat cycling the manifold and cracking it you should be fine where you are at. If you want to reduce your knock safety margin you can advance the timing, but if the vehicle is already achieving what you want it to achieve I wouldn't get greedy with the spark.

And the answer is 'maybe' - you need to try it and see what affect it has on EGT and torque/power.

That said, your primary problem is you are running way too lean and need to address that first.

OP can you post a READABLE screenshot of a graph showing rpm, boost, timing and lambda? As in, not a grainy flip phone style camera pic with flat unscaled lines on it...

First up a safe and healthy on gasoline doesn't translate to methanol. If you try and shoot for EGTs that are safe on gasoline (1700-1800 F) then you'll be lucky to make it past the 60' mark. There are a multitude of factors that affect the EGT so it's not strictly possible to take a line in the sand and say XXXX EGT is safe. That being said, I'd recommend aiming for EGT in the 1200-1300 F range for the low boost you're running. On the very high boost small capacity drag engines I've been involved with I'd see as high as 1400 on occasion but that's higher than I'd recommend, and you need to factor in that these engines are running 45-65 psi boost too!

The timing really needs to be dialled in to find MBT. Yes it will affect EGT but that is a secondary concern really. The problem is that when we look at EGT we're trying to infer what's happening inside the cylinder (combustion temp is what we're really interested in) with the results of the combustion process. For example here, retarding the timing will give you a higher EGT reading but it's possible that it's actually not less safe for the engine. So the timing really needs to be set to achieve MBT or provide a safety margin to the knock threshold (in your case I'd imagine you'd be hard pressed to make the engine knock at such low boost).

The lambda targets that I mentioned in the thread Gord linked to above are suitable for small capacity import engines but it's quite common on large capacity V8 engines to be MUCh richer than this - I'm talking 0.50-0.60 lambda. What you need to understand with methanol is that it's incredibly forgiving at very rich mixtures and you see little taper off in terms of power (unlike pump gas). On the other hand it's very intolerant of lean mixtures and gives little warning before you have a bunch of melted pistons on your hands. The only challenge with the rich mixtures is lighting off the charge in the first place.

So to sum up, get your timing dialled in for peak torque and try running the engine a little fatter. I'd try running around 0.60-0.65 and see how that affects your EGT.

I did a print screen

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here is another one

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another

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I'm not quite sure what to make of the three screen shots you've posted? There are several differences between them that make it hard to draw any real conclusions. For example the lambda, boost, rpm and timing vary between the three so it's understandable that the EGT will also be influenced. To get meaningful data you need to hold all variables steady and change one at a time. The other aspect that needs work is that you've got quite a large spread in EGT which you can tune out to a degree using individual cylinder trims. I personally try and match the EGT under high load conditions to within 20 deg C or better (approx 70 F). I recommend you do this by adding a small amount of fuel to the hottest cylinders and watching the effect on your EGT.

Reason I harped on about the fuelling is that WILL bring down the EGT, which will be a lot safer for the engine than playing around with timing in a lean condition as you're rolling the dice on melting the engine down. As Andre said, you're most unlikely to be giving up power, but rather the reverse.

Then you can play around with the timing and fuel trim for best torque while keeping the exhaust and engine temperatures within an acceptable range.

However - your engine, your call, your bills ;-)

The egt is measured before the turbo about 3 inches past the header flange. I see what you're talking about there's a wide spread between cylinders. EGT two is at 1424 Fahrenheit and EGT six is at 1138 and this is only at 6000 RPM that 5. 7 lb of boost. On my ms3x I do have injector trim. One other thing I wanted to mention is my timing is sitting at 33 degrees at this boost level. Do you think that this is about where it should be? here is a screen shot of my timing table. there is some cells in the cruising range that are in the 40's. I found by running the timing way high my egt's dropped quite a bit.

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IN THEORY a retarded ignition point will mean less energy used to move the piston and more passed out the exhaust, meaning higher EGT, with over advanced reducing EGT at the risk of detonation/pre-ignition damage.

As Andre has often said, you should be aiming at MBT - Mean Best Torque - where the engine is most efficient, and I have usually commented along the lines of 'with acceptable EGT'. Some turbochargers are more tolerant of high EGT* than others but either way, excess heat will weaken the turbine blade material if it is higher than the material used can cope with.

Easiest, and IMO best way, to drop the temperature of the exhaust is to run it rich and, as you are apparently running lean of stoich' for the fuel you are using anyway, I strongly suggest you run that significantly richer as a first step. THEN you can adjust the ignition timing and fueling (and trim) for best torque/power while keeping the EGT in an acceptable range - I honestly don't get why you aren't doing that?

*Exactly what are you using - some can have a recommended max' of 1300f, or even less - note, some are sustained, some are maximum and you need to check if given in f or C. Actually, what is the full spec' of your application - could also be a restrictive hot side holding in heat, could be the exhaust manifold design.

This is from Mr banks' site and is for diesels, but same principle applies for ALL turbochargers.

"We’ve already mentioned that excessive EGT can cause engine damage or turbocharger damage, but let’s get more specific. Which parts will fail first is a matter of the design and materials used in the various parts of the turbo-diesel, but usually it starts with the turbocharger. Under sustained excessive EGT, the square corners at the outer ends of the vanes, where the material is thinnest on the turbine wheel, can become incandescent and then melt, resulting in a rounding off of the square corners. If you or your mechanic finds this indication before anything more serious happens, consider yourself very lucky, because shortly after the tips melt, the turbine wheel goes out of balance and wipes out the turbocharger bearings, which may or may not result in shaft failure and destruction of the turbine and compressor wheels. Excessive EGT can also erode or crack the turbine housing. In extreme cases, high EGT can drive the turbocharger into an overspeed condition that exceeds the designed operating speed due to the additional heat energy. When this happens, either the turbine wheel or the compressor wheel may burst. If the turbo doesn’t go first, excessive EGT, if sustained, will damage the pistons. Such damage can include piston deformation, melting, burning, holes, cracking, etc. This damage is cumulative, so if you slightly burn a piston top, the engine may continue to run without problems, but the next time you run excessive EGT more damage may be done, and so on, until failure occurs. Piston failure can be catastrophic — that means very expensive. At a minimum, an engine overhaul will be required, and that too is expensive. Excessive EGT can also cause exhaust manifold and cylinder head cracking. Exhaust valves can fail from high EGT as well. Among the first engine parts to suffer damage will be those made of aluminum since aluminum has a lower softening and melting temperature than steel or cast iron. Diesel pistons are aluminum, and a growing number of diesels also use aluminum cylinder heads."

Also - http://www.dieselhub.com/performance/egt.html - won't let me C&P the relevant parts, so please read it - again a diesel site but same principles apply regarding temperatures and material limits and failures.

Pretty much everything above 100 kPa was targeting in the low .700 Lambda. So I don't believe that's very lean. This is one of my friendshttps://www.facebook.com/kevin.kwiatkowski.92 on Facebook .

Said this.

I read in lambda. I target 0.85 at 0psi, which makes best power and rpm on my combo. I ramp down to 0.7la by about 15psi and then 0.6la by about 35psi. Under boost, I have not seen much difference in power from 0.56-0.61la. Haven’t really tried leaner.

Ah, if you are using a raw lambda value of ~0.7 it is indeed rich - you had said a lambda of low 7s to high 6s which I had interpreted as whole numbers and hence the AFR which would be lean- my mistake it seems, so disregard my comments re: mixture.