Alternative intercooling idea

[Zuffen]

I found the following Site whilst looking into Opcon twin screw superchargers http://www.jagweb.com/aj6eng/supercharging_article.html and it has an interesting intercooling option.

Back in World War two when supercharging the Rolls Royce Merlin engine they injected a small amount fuel before the supercharger to act as a cooling agent to stop the supercharger itself heating up and therby cooling the charge air.

What would happen if when you went on boost a 9th injector came on line before the suercharger and fed fuel into the intake. You could lean out the other 8 injectors to allow for it. I figure it would be possible to use the cold start injector to a) start the engine and b) to cool the charge at high boost.

Have a read and let's kick the idea around.

It sure would beat water or methanol injection and be heaps lighter than any interccoler whether W2A or A2A.

 

[Lextreme II]

I think the biggest problem with that method would be tuning. The 9th injector acts as an fuel injector for cooling. Too little fuel, will cause leaness and too much fuel will cause richness. Its a fine line and the cold injector is not adjustable. Its on or off type of function. I would use a fuel injector instead of the cold start injector. With a piggyback you can control when and amount of fuel. Secondly, I am not sure what is the danger of fuel (flammable) entering the charger. Heat and Fuel might create explosion, but i am not sure.

I used fuel injection before on my LS400. Instead of Methanol, I used fuel instead. What I experienced was I actually loose power. Great idea and I think its workable if done properly.

 

[MWP]

I dont see why fuel is going to do any better job for this than a water or water/methanol mixture.

If you use water you also dont need to worry about running rich, and you also get the benifits of normal water injection.

BTW... injecting water/fuel before the SC also helps the rotors seal, giving higher air-flow/boost.

 

[Toysrme]

Water will always work better - It's just that not everyone wants to install & wonder about a water level.
Personally, I love extra (pre-tb) injectors as they have unique advantages.

AFA injecting fuel pre-compressor. Nothing is stopping you. I would do water, or water/ethyl alcohol (NOT methyl) if all you're looking for is charge cooling - water will kill fuel left & right.

I love cold-start injectors for an over-fuel / safety aspect.
1) Great atomization!
2) Any 8v+ will activate them
3) They come with a built-in solenoid - so no leaks under boost/vacuum
4) Not alot of fuel (15 or 30bhp of fuel @ around 40psi for most of them)

 

[Toysrme]

One of my many Toyota CSI's I have laying around test spraying water off a used Toyota windshield washer pump.
Old pics on a bad cam - sorry.







From off (top left) to on (bottom right)








Great atomization - even with straight tap water hah!

 

[Zuffen]

So the injector didn't mind the water? I would have expected it to rust in the pintle.

 

[Toysrme]

The Toyota one's I have experiance with (All the v6 & most of the S block i4's)

They *may* have the possibility of corrosion around the atomizer running water. I'll freely admit that - tho I've never experianced it. I *think* they're mild steel housings & the atomizer at the end is brass - if that's correct - then no - it'll never be a problem with corrosion. If it's aluminum tho, eventually I'll run into trouble!
A year of water injection through one on the car - I've never had it be a problem with the atomizer insert corroding closed. And if I give it voltage - you can hear the solenoid trip open & water flows throguh. I can't comment on how that reacts tow ater - but It hasn't been a problem either.

I was concerned about that to begin with - but after taking it out every few days - then weeks & the one on the car always sprayed a good pattern - I figured it should be good.




That may not be the glowing reccomendation that you want - but I like them! LoL!
If the idea scares you, just run fuel through one. It'll be constructive! Just won't get the cooling / anti-detonation affect.

 

[cribbj]

Rod, I see this is drifting into another MW injection thread instead of your fuel idea. The methanol does provide heaps of evaporative cooling and I'm planning on injecting it pre-supercharger for my application as well. I didn't look at injecting fuel pre-supercharger, as for my application with LPG, I wasn't planning to have any liquid fuel onboard.

I did a thread awhile back showing how much cooling effect there is with methanol injection, as modeled by a knowledgeable process engineer:

http://www.lextreme.com/forums/showthread.php?t=2380

 

[Zuffen]

If you look at the experience in the Rolls Royce engine, in the article attached to the first post the fuel contributed quite a lot. This was supported by the later use of the same system in motorsport.
The way I see it is the additional fuel you feed in pre-supercharger is balanced by injecting less fuel post supercharger.

I'm quite ambivalent about methanol/water and see no reaon to not use it.

I figure put up unusual ideas and you may hit a winner.

 

[skid]

I mentioned a 9th injector here:

http://lextreme.com/forums/showthread.php?t=5402

to do the same thing pre compressor, but was wondering about the volatility of atomised fual flowing through all the piping and an A2A intercooler plus how do you handle gas omissison from a dump or bypass valve.

I guess you can only use the 9th injector with fuel if there is no other form of intercooling and the boost surge is passed straight back to the compressor input.

Comments?

Mark

 

[Lextreme II]

Fuel as a source of cooling is the most easiest. All you need to do is to run a fuel line from the fuel rail. Secondly you dont need additional pump or reservior. When the 9th injector or cold start injector is on, the fuel pressure and volume will decrease from the rest of the eight injectors. That can cause some leaness especially if the system is in boost. So tuning would be very critical. As mentioned above, the volatility of atomised fuel might dangerous. Conbustion (Fuel, Air and a source of ignition) in the supercharger is very dangerous.

 

[Zuffen]

Spraying fuel in pre compressor is only like adding Propane/Butane pre compressor which everyone seems fine with.

The compressor temps (on centrifugal and twin screw only) are low enough there shouldn't be any problems of spontaneous ignition in the compressor.

You couldn't use this system with an A2A or W2A cooler as the fuel could settle on the cooler core and lean out the mixture.

I only suggested the cold start injector so the concept is easier to follow plus it would be easier to mount.

I'm not convinced it can't work.

 

[Pro]

if you mix a small amount of household ammonia with your water injection you get hydrogen added to the mix, but also nitrogen - which is inert.

i would just stick with WI myself.

 

[skid]

Spraying fuel in pre compressor is only like adding Propane/Butane pre compressor which everyone seems fine with.

The compressor temps (on centrifugal and twin screw only) are low enough there shouldn't be any problems of spontaneous ignition in the compressor.

You couldn't use this system with an A2A or W2A cooler as the fuel could settle on the cooler core and lean out the mixture.

I only suggested the cold start injector so the concept is easier to follow plus it would be easier to mount.

I'm not convinced it can't work.

Good point about fuel dropping out and sitting at the bottom of an intercooler.

I guess you're right it would work in the right application such as a straight forward bolted on M112. Infact the more I think about it the more I believe its a brilliant idea!

Cheers
M

 

[Anaema]

Fuel as a source of cooling is the most easiest. All you need to do is to run a fuel line from the fuel rail. Secondly you dont need additional pump or reservior. When the 9th injector or cold start injector is on, the fuel pressure and volume will decrease from the rest of the eight injectors. That can cause some leaness especially if the system is in boost. So tuning would be very critical. As mentioned above, the volatility of atomised fuel might dangerous. Conbustion (Fuel, Air and a source of ignition) in the supercharger is very dangerous.

bad idea, unless you are using Ethanol or Methanol. Gasoline doesnt cool as much as alcohol does when it evaporates. and water is even better at cooling the intake charge than either alcohol or gasoline.

 

[MWP]

Good point about fuel dropping out and sitting at the bottom of an intercooler.
I guess you're right it would work in the right application such as a straight forward bolted on M112. Infact the more I think about it the more I believe its a brilliant idea!

As long as you are not spraying huge amounts of fuel, spraying before an intercooled SC wont be a problem.
If the fuel is properly sprayed (atomised), once its through the hot supercharger, itll be completeley evaporated into the intake air.

I would be more worried about an inlet backfire... would create a HUGE amount of damage.

 

[Toysrme]

Avoid Methanol.
It's problematic over time, and neither ethyl, nor methyl will completely combustion is a gasoline dominated environment. (Both quickly drop under their Lower Explosive Limit of oxygen.) If you have to run an alcohol, run ethyl.
From here, my opinion on the water/alcohol matter:
As far as running an alcohol - Unless you need the lower freezing point that alcohol provides VS straight water. Forget it entirely. You always hear people gloat *so* much about how much better water is with alcohol.
What they never tell you is the fact that you could easily throw nearly your entire volume of your fuel mixture in as water on top of fuel on the high compression & high effective compression ratios that people run on engines today when they're really cranking out power.
Which to me, sets water/alcohol mixing back to "Why would I want to both with alcohol, when I can just run a fraction more water in the first place." To which my only logical answer to that is, "Because you live somewhere that water is in danger of freezing!".

I wouldn't be concerned about pre-compressor fuel, once you find out the operating temperature of the supercharger. Like any intake manifold, I'm sure it can get up 300-350*F easily enough just sitting on top of the engine.
To me, the only question would be if the surface temp of the metal would be hot enough - and the gas stay in contact enough - for it to cause a flash.
I don't think it would, but I don't know on a first hand basis. So you can decide for yourself.
Pre-intercooler fuel, yes it's a problem. It can pool. (We all know that one.)
Pre-turbo/centrifugal compressor fuel, yes it's a problem. (NOT because it damages the blades - which is a falsehood, but because fluids will pool in the turbo housing.)


I like the idea, I don't think you'll have a problem with it. My only hang up is how cheap a pump & a big container full of water is & how much "better" that might possibly be VS what it costs.
(I really don't believe when people tell me they don't like checking water all the time. I ran 3 1/2 - 4 gallons of water in my nose 4x 1 gallon containers. at one point when I was running water injection 24x7 trying to see the impact it would make by letting me do a lean-burn cruising around town.)