EGT monitoring on each cylinder

[campbellju]

Does anyone have experience or some links for running an EGT on each cylinder on a GtiR or SR20?

I'm seriously considering doing this for my next build.

After 20,000 miles on my last engine running 1.9bar, numerous track days and RR's etc you can see cylinder 1 (timing chain) has had an easier life than cylinder 4 (Dizzy). (I've put the description in case I've mixed up my ends!)

Most sensors are averages for the engine: MAF, WB lambda, knock but with extended use Cylinder head temperatures (CHT) are rising higher at one end of the engine than the other.

The normal way to manage this is to back off ignition or increase fuelling.

I'm thinking for tuning it would be good to have a better understanding of what each cylinder is doing. 4 MAF's or WB lambda is not possible but 4 EGT's is.

With the PFC all I can do is tweak the fuel injector settings to squirt more fuel to the hotter cylinder (All the time) with progressively less until I get back to cylinder 1. If there is an imbalance in CHT across the cylinders then this method would help at high loads/rpm but may give issues at lighter loads.

Alternatively I could just run a more conservative map (boost, ignition, fuel) for more longevity.

Thinking through it, I could do both of these options without bothering with 4 EGT's anyway.

From what I've read on aeroplane sites, trying to perfectly balance EGT's is misleading too and should only be used as a guide. Car sites as ever have mixed opinions.

Anyone else come across this issue?


Jim

 

[PobodY]

Obviously I have no experience of this.

Is it a case of understanding what the temperature readings are saying? - I don't know about aeroplane enginges; are they usually air cooled? It occurs to me that in an application like that, the "front" of the engine will always run cooler than the rear by virtue of that being where the air passes first.
In which case it would be slightly different in a water-cooled car engine, and the individual port readings may have more meaning (thus the discrepancy between the two).

As you've detected that the front of the engine has run hotter than the rear, does that suggest that it's a coolant flow issue; simply that the rear (right) side gets better cooling?
Is it an issue of differential air/fuel mixtures caused by the plenum design or slightly un-balanced throttle butterflies? - In which case adjusting the fuelling by injector may be the answer after all.

I'm sure there are memebers who actually have knowledge rather than analytical training; I'd be interested to read what they say too. - I suppose what I'm suggesting is that you may need to isolate causation from correlation.

 

[stumo]

Rub yer balls on the manifold and all will be well.

 

[Trondelond]

isn't this caused by the plenum design? The airflow to each runner is different, and therefore produce different results as the injectors will dish out the same amount of petrol? Would probably need a different intake with a better end-to-end bias of the airflow I guess. Or the ability to map each injector individually - of course with an EGT in each exhaust runner. :-D

 

[campbellju]

I've been reading on Subaru sites about the problems their unequal length manifolds cause on high power cars. The longer runners on cylinders 2 and 4 apparently give higher EGT's so these are normal to fail.

I don't think tweaking the throttle bodies at WOT will have much effect but at low rpm/throttle be quite significant.

Increasing cooling I think has been discussed before. Log type intake manifold's I've seen. Equal length exhaust manifolds too. My only other option is throw a bit more fuel in one side.

I could just run a richer AFR by taking the average AFR on a known map. Add X% fuel to all injectors to reduce the AFR by 0.5 at WOT and see the effect at idle etc. With this knowledge I could revert cylinder 1 to the base setting and smooth across to cylinder 4 at the new setting and save some money on EGT's. Even with EGT readings I might end up at the same place but with the feedback on the changes I'd made.

I doubt I'm the first to have thought about this with an SR20 and I agree with your scientific mind.

 

[stumo]

I agree with your scientific mind.

Cheers, it's just shows what a good ballrubbing can do. 8)


With a PFR you could map the engine (equal amounts of fuel ) then trim No4 by adjusting the injector percentage?

 

[campbellju]

That's my thinking too Stu. (The PFC trimming rather than the ball rubbing. Ball rubbing would hurt on my manifold, it's wrapped so you'd get looks of silica fibres stuck in your sack).

... Funny your ball rubbing made me think. On my company's glass furnaces we insulate them when they're new to save energy but start stripping back after 10 years to aid cooling and longevity. Maybe I should uninsulate that side of the manifold to aid with EGT's and ball rubbing?

 

[warringtonjack]

Just out of interest (and nothing to do with ball rubbing), I've never lagged my manifold because as long as the air filter was kept far enough away and had a good cold air feed, I'd rather try and let the temps dissipate from the manifold (however miniscule that might be) before it hits the turbo.

 

[stumo]

Just out of interest (and nothing to do with ball rubbing), I've never lagged my manifold because as long as the air filter was kept far enough away and had a good cold air feed, I'd rather try and let the temps dissipate from the manifold (however miniscule that might be) before it hits the turbo.

you want it to be the opposite, as hot as possible....

 

[PobodY]

...to keep the gas flow fast until it has been through the turbo (to get better turbine speed)?

 

[skiddusmarkus]

Maybe a 4 point WI setup with graded nozzles(ie more water for the hotter cylinders) for each cylinder?The nozzles would obviously be a lot smaller than the normal 1 point injection.
You aren't supposed to put the nozzle too close to the plenum or it can stop the water mixing with the air properly but if you used a small enough nozzle the mist will be incredibly fine so should aid mixing.

 

[PobodY]

You know what's funny, I was just thinking about this recently! - On the basis that we've actually got four throttle bodies, it might make sense to run 4x0.2mm nozzles rather than 1x0.9mm (or whatever the size would be for your application).
Also, I'm not sure about this, but a smaller nozzle might give you better nebulisation for the same line pressure; so you'd get four fine jets (of smaller volume each) rather than one large one which might be giving you bigger droplets.

The other thing I was wondering was, with so much debate about it, is it worth running 1x0.1mm (or whatever the smallest nozzle is) pre-compressor, and 1x0.8mm pre-plenum; that should limit the damage to the compressor wheel and still give you some of the performance gain (supposed to make the compressor map behave like a much larger turbo), and the rest injected just before the throttles for DET control mainly.

I'm also back on to thinking about the optimum mix for the injection; I know that anecdotally 50/50 (by weight) is the best, and that there is no azeotrope of water and methanol... but if I used an ethanol or iso-propanol azeotrope with methanol, could there be some benefit? Were the WWII era mixtures (with a touch of lubricant) a good idea, and if so what could you use?
As an example; there's a ternary azeotrope of methanol with acetone and cyclohexane, but I'm not sure that you wouldn't need to map specifically for this kind of injection.

 

[Fast Guy]

The aircraft I used to work on injected water/meths dierect into the eye of the supercharger. The mix was either 60/40 or 70/30. I'd have to fire up my old computer to find the data sheet for the mix. There was no lubricant in it that I'm aware of, but it the data sheet should say if there was or not.





On the quad egt note I was looking round a while back and found an aircraft gauge. Not sure if they'll be 28V gauges or not though.
http://www.aircraftspruce.eu/images/products_max_800x600/10-01276.jpg

I also found this.
http://msextra.com/forums/viewtopic.php?f=67&t=35218&sid=20e0ef8c4a3da1147bf2bbd0a7b7c6e3&start=30

 

[skiddusmarkus]

I don't know about the other kits but with my ERL Aquamist you aren't supposed to use ethanol as it can kill the seals inside, that's why you cannot just fill it with any old screenwash.I look a right saddo in car spares reading the ingredients of screenwash trying to find one that still contains methanol.

 

[PobodY]

The aircraft I used to work on injected water/meths dierect into the eye of the supercharger. The mix was either 60/40 or 70/30. I'd have to fire up my old computer to find the data sheet for the mix. There was no lubricant in it that I'm aware of, but it the data sheet should say if there was or not.

I'm just going by what I read on Wikipedia there. I've got no experience of it, other than it was called MW50 for Methanol und Wasser 50/50

I don't know about the other kits but with my ERL Aquamist you aren't supposed to use ethanol as it can kill the seals inside, that's why you cannot just fill it with any old screenwash.I look a right saddo in car spares reading the ingredients of screenwash trying to find one that still contains methanol.

Ethanol and methanol are really not that different; I'm surprised they make that distinction. We're talking 15amu and one carbon (CH3CH2OH Vs CH3OH)
Maybe it's because ethanol does form an azeotrope and that's what does the damage (in which case I should abandon any idea I had of formulating a super mixture right now)?

Having said that, I already know that you're looking for the screen wash that says it's rated to -20C ;-)
I'm thinking of just putting in an order for 20L of high-purity methanol, and taking deionised water from work; then I can mix-up my own... which is why I got got thinking about making my own recipe.

 

[red reading]

syvrcs s6gp,

 

[fubar andy]

M800 or just buy 4 sensors, plug them all in to one reading gauge