Anyone checked inlet temp on a C230 Kompressor?

[StavFC]

As title really. Im guessing no, but wondered before I go and do it, saving me a job.

The way the car drives feels to me like on cars when the intercooler is struggling, but its a fair size and the boost is v.low, so kinda surprised if it is, and the odd shape pipework makes an upgrade not a particularly easy task, so rather not unless its really struggling.

If anyone has, through the ODB2 or an external sensor, thatd be great

 

[ched999uk]

I'm not trying to teach you to suck eggs but if you are right and the charge temp is higher that desirable. Then an easy way to assist in cooling the intake charge temp is to spray the OUTSIDE of the intercooler with a mist of water. The water greatly assists the cooling of the actual intercooler its self.
I am guessing, by your Mazda RX7 500bhp/ton you know a few good tricks

Sorry I dont have any data on the inlet temp. I guess you will have to do a fair few full power runs to get the intercooler temp up?

 

[StavFC]

Spraying the outside of the intercooler with water, unless its totally heat soaked, and thats highly unlikely on a moving car, will do nothing at all of any worth.
If you are spraying water, spray it into the boost pipe or compressor inlet.

And would test it by basically holding it through the rev range in all gears, sometimes they cope for lesser amounts of time in lower gears but only stuggle higher up.
The only time an intercooler itself gets too warm is extreme situations so not likely, but that doesnt mean it can cool the air rushing through it properly at hundreds of miles an hour.

 

[ched999uk]

You would be surprised how much difference spraying water on the outside of the intercooler makes. On my golf it only had a small intercooler and it wasn't effective enough when I got up to about 10psi. So I had a play with thermocouples and spraying water on the outside of the intercooler reduced the inlet temp by about 20-30 degrees! OK so no where near as good as spraying water into the inlet manifold but a lot less dangerous. Ideally use a charge cooler (water to air intercooler) as they are much more efficient. when I had a play with water spraying I just used bits and bobs I had lying round the garage

 

[StavFC]

Ah right, in testing I've done in the past spraying onto the intercooler made no real difference according to my charge temp gauge, but there is going to be plenty of variables.

I'm currently spraying 660cc of water directly into the compressor inlet of my turbo on my RX7 with no damage at all, was spraying about 350cc into the inlet manifold before, and similar amounts on two of my other cars, no problems.
Its not dangerous if done right, despite people claiming spraying anything pre-turbo is, never mind over half a litre a minute.
I dont see much point of spraying anything anywhere barring pre-compressor, but everyopnes got their own ways.

Chargecoolers are the most effective for their size in theory, but only if you got a suitable sized water radiator to keep the water cool enough. People fit chargecoolers the size of a shoebox, and a radiator even smaller, and expect it to be as good as a massive front mount intercooler, but it never is.
Aside from drag applications where you running for sub 10sec and you can just fill an ice chest with water or get away with a small rad, an intercooler is almost always better.

 

[Bellow]

I'm currently spraying 660cc of water directly into the compressor inlet of my turbo on my RX7 with no damage at all, was spraying about 350cc into the inlet manifold before, and similar amounts on two of my other cars, no problems.
Its not dangerous if done right, despite people claiming spraying anything pre-turbo is, never mind over half a litre a minute.
I dont see much point of spraying anything anywhere barring pre-compressor, but everyopnes got their own ways.

I'm intrigued by this!!
Firstly, I would have worried that water introduced pre-turbo could/would damage the impeller, and be inclined to be centrifuged out and cling to the walls of the ducting rather than atomising in the airstream.
Secondly, I would have expected it to be more effective sprayed into the hotter post-compressor air stream.

What manifold or boost pressure are you using, and is there a difference between the quantities of water required for the same effect depending on where introduced?

PS.
Not quibbling, I am genuinely interested in this!

 

[StavFC]

Theory and internet myth says it will damage the turbo and wont be as good as post compressor.
Reality, countless WW2 combat aircraft, Indy/Cart race cars, and countless tuned road/drag cars prove otherwise.
The right jets, the right positioning, and other bits and pieces done right, and your going to break something else before water damages your compressor.

I know of people injecting 1500cc water pre turbo without damage, and IIRC Indy/Champ cars inject over 6 litres of methanol per min pre turbo at full chat, so what I have done is nothing.

Don't understand why anyone would want to inject post compressor unless race rules stated it. Why cool air heated by an inneficient compressor when you can make it more efficient (ie stop it making the air so hot in the first place), effectively making it work like a larger compressor would.

On my RX I 'was' running 23psi, injecting from about 15 (will be different once its all back together), and personally I go by power levels rather than boost levels for the amount of water injected, but different peoples got different ideas on that.
And even the amount totally depends on if your ignition can cope and opther things- just like all car tuning, theory and reality is very different so it just means trying stuff until you find whats best for you.

Although when I first mentioned it on here someone claimed it would kill the supercharger on a Merc super fast, I cant see where they got that idea from, when I get a chance I'll do it, looks a pain in the **** to get a decent sized intercooler on a C230K to me.

 

[Bellow]

Wherever the water is introduced, at some point in the cycle, either before or after the cylinder, it is going to turn to steam.
Any ideas what effect this has on combustion and the effect created as it expands through the turbine? Is the steam essentially stored energy capable of being utilised by the turbine?

I assume you're primarily injecting water to lower inlet temperatures to avoid detonation, or are you considering it from the combustion perspective also? And if so, what is the perspective?

 

[StavFC]

I don't really know what you are asking as such, when you say turbine, you mean actual turbine side, or the compressor?
Either way, in no way does steam get used as any kind of power source, its surely to decrease inlet temps, decrease the chance of det, and in my case of pre-compressor, increase compressor efficiency.

 

[Bellow]

Just wondering what the water does next, once it has been through the compressor and makes its way through the engine and turbine side of the turbo!
I have a book that should explain it though. Time for me to get reading...

 

[StavFC]

Its nothing by then.
Water is oxygen and hydrogen, neither of which would survive the combustion process in any way aside from if you totally flooded the engine, and even WAY before that the car would missfire and/or be hugely down on power.

 

[Bellow]

If that were true we could run engines on water alone!

The water goes somewhere....

 

[StavFC]

If that were true we could run engines on water alone!

The water goes somewhere....

No you couldnt, not by a long shot.

The ins and outs of it is the water does nothing else but help suppress det, lower inlet temps to some extent, and with what I do improve compressor efficiency.

I'm not sure if you just having a laugh or are serious, but this is rather off topic and getting pretty ridiculous.

 

[Bellow]

I'm not sure if you just having a laugh

Not me.

 

[NormanC]

I don't really know what you are asking as such, when you say turbine, you mean actual turbine side, or the compressor?
Either way, in no way does steam get used as any kind of power source, its surely to decrease inlet temps, decrease the chance of det, and in my case of pre-compressor, increase compressor efficiency.

This is all fascinating. Any chance you could attach your curves of compressor efficiency versus water injection rate, please.

 

[StavFC]

I have nothing like that, there's no way for a normal person to ever log compressor efficiency. For any normal person its purely testing from experience, trial, and error.

You might find logs if you look in to gas turbine generators etc at power stations (they call it wet compression normally), as they use this same method. But as they have to go on for years and years constantly (ie far longer life than a tuned car), I doubt they push the water levels to anywhere near optimum for them, just keep it very VERY safe.
Might find some kind of logs if looking at WW2 planes too, or Indy cars, but I dont know.

I never go by other peoples numbers or theory so never worried about that, I just go by if it looks like it may work, try it, and if it works, keep it and try and optimise it for me.

I did blow my engine by running without it for a few seconds though...

 

[NormanC]

I have nothing like that, there's no way for a normal person to ever log compressor efficiency. For any normal person its purely testing from experience, trial, and error.

Ah...I understand.

It is interesting that Toyota for their rally cars preferred charge coolers to intercoolers and used water spray onto the outside of the charge cooler radiator. I can only assume that their massive test program showed that charge cooling had advantages over intercooling and water spray was worthwhile.

If water is injected prior to the compressor it is being injected into cold air. Under these circumstances it is likely to remain as a mist of droplets with virtually no vapour. I wonder how passing droplets of water through a compressor improves its efficiency. Also these water droplets replace an equivalent volume of air (the compressor can only ingest a certain volume of matter) and isn't it, effectively, the more air the more power?

Water injected after the compressor is being injected into hot air (often 150+ degrees C I believe) and will instantly vapourise, its latent heat of evaporation giving a massive cooling effect to the charge. With the charge being cooled this allows a higher effective compression ratio i.e. higher boost without detonation.

I see that you're spraying 660cc/min of water. Where do you store all this water?? This rate of water consumption is perhaps greater than your fuel consumption so your water tank is bigger (and when full significantly heavier) than your fuel tank. As the water used is generally regarded as having to be of "boiler quality" or at least ion free it must be an expensive hobby to fill the water tank.

In answer to the question as to what happens to the water after it has been through the compressor, the engine and the exhaust you say "Its nothing by then. Water is oxygen and hydrogen, neither of which would survive the combustion process in any way....."

Water can exist as as steam, either saturated or superheated, at temperatures and pressures well in excess of those experienced in a combustion engine. As to oxygen and hydrogen not "surviving" the combustion process I think that you need to think again. Oxygen survives as a component of the CO, CO2 and NOx produced and hydrogen survives as a component of the water vapour produced by the combustion of hydrocarbon fuel. What does happen to the additional water injected? It comes out of the exhaust pipe as steam or water along with all the other water produced by the combustion process.

As a final point, I agree with you completely that water injection into the inlet of an internal combustion engine can improve performance. I just wonder if it has any sensible application for road vehicles. If it did, would'nt we by now being going into a petrol station and filling up with 50 litres of petrol and 50 litres of water?

You obviously have a lot more experience of these things than I do so I'd appreciate being shown where I'm wrong. Similarly, it is too many years since I studied the thermodynamics of the compression of water/air mixtures and you must remember a lot more about this than I do.

Thanks.

 

[Bellow]

De-ionised or not Norman, I hope you have plenty water on hand as you are no doubt about to be well and truly flamed - for talking sense!!

I know it is a little rude to threadjack, but as rudeness seems to be no bar to posting on some current threads.... Do you suppose the turbine extracts usefully energy from the steam present in the exhaust, or would it see the same energy were the water/steam not present, through a higher temperature in the exhaust products alone - assuming the turbine could withstand the additional temperature?

 

[ched999uk]

Interesting NormanC. StavFC has a Mazda RX7 with over 500bhp so I am guessing that its mainly a 'fun' or track day car. I am guessing that the addition of water is what is required to get the power he has.
I would also agree that to me cooling charge air is best achieved after you have warmed it up so to speak. Otherwise you would just be adding water to your charge, both at ambient temp. From my recollections of development of the WR21 combined cycle gas turbine engine. The charge was cooled between compressor stages not before compressing.

I am not knocking StavFC as he has said that his experience has been gained through practical experimentation. Sometimes what works in practice isn't necessarily what the theory dictates but sometimes the practicalities of the theory are difficult.
If you inject water before the compressor then air is at virtually ambient pressure so its easy to spray water in. If its after the compressor then you have to overcome the boost pressure, maybe 20psi, before you can spray the water, thus a higher pressure pump would be required.

Anyway, as StavFC said he is just trying to find out inlet temp data.

I think this is a great discussion, as there seem to be very few posts about increasing the performance of the Kompressor engines here.

 

[NormanC]

De-ionised or not Norman, I hope you have plenty water on hand as you are no doubt about to be well and truly flamed - for talking sense!!

I know it is a little rude to threadjack, but as rudeness seems to be no bar to posting on some current threads.... Do you suppose the turbine extracts usefully energy from the steam present in the exhaust, or would it see the same energy were the water/steam not present, through a higher temperature in the exhaust products alone - assuming the turbine could withstand the additional temperature?

As to whether the turbine extracts extra energy from the additional water vapour, it's difficult to say, as I think that it's a matter of swings and roundabouts.

Logic seems to say that there is additional energy available because of the increased mass of water vapour present. However, it seems that water injection reduces the peak temperature of combustion and thus of the exhaust. Hence we have, possibly a higher exhaust mass flow rate but at a lower temperature - swings and roundabouts. I wouldn't like to say without some testing.

However, most turbocharged applications have more than enough energy available to give maximum required boost. When boost needs limiting the waste gate opens and exhaust is diverted past the turbine.

My GT4 reaches max boost (approx 1 bar) from about 3800rpm up on full throttle. I suppose that means that at any speed above 3800rpm exhaust energy is being dumped through the wastegate. I can't, therefore, see any realistic gains in increasing exhaust energy - unless you are just trying to extract the absolute maximum boost from an undersized turbo!

An interesting thoughts arises here! With a turbo charger you are only compressing as much air as you need - when you have sufficient pressure you efffectively don't drive the compressor any more, i.e. you dump exhaust. With a positive displacement compressor once you have sufficient pressure you dump the excess compressed air . You supplied power to compress this air and consequently heat it but then you just throw it away!! Does this mean that a turbocharger when providing boost is more efficient (i.e. produces lower temperature air) because it isn't having to compress air which is then thrown away? I don't know!

If we go back to the meat of the thread, StavFc was asking if anyone had data on the inlet temperatures of a C230K. Not an obvious question to ask for most people but his experience and knowledge throws this up as a query - and quite rightly in my opinion.

However, let me postulate that I have some of the figures he is requesting. What do they mean? For them to be relevant to resolving his problem he must have his own set of figures. How comparable are they? They really need to be compared at a set speed and load (steady state) or under a rigourously controlled cycle, under known conditions of ambient temperature and pressure and relative humidity.

Let us now assume that these hypothetical figures show that he has a problem of a high inlet temperature. What can be done about it?

As the question was asked about a C230K it isn't unreasonable to assume that any solution must be practical for an every-day road car. Possibilites appear to be:-

1) Clean the inside and outside of the intercooler - laborious but very cheap and should recreate original performance.

2) Fit a larger intercooler. Lots of work and not necessarily cheap.

Beyond this I just don't know. Intercooler water spray and/or water injection are, in my opinion, not practical for a daily driver.

As a consequence, my only advice to StavFc is, if the car doesn't perform as you think it should due to intake system anomalies, change it for one that does UNLESS you want to spend lots of money and lots of time tyring to resolve the problem.

But.... it's only my opinion - I would be very happy for anyone to show me where I'm wrong!

Finally, thanks to StavFC for prompting this interesting discussion. It's great to have people like him contributing his knowledge and experience which are outside the sort of thing that we normally see in these forums.