924Board.org

[simsport]

Ok guys, if any of you have experience of water injection please speak up.

I have a basic system to fit to my supercharged car, aims being to reduce the charge temp which can hit around 120 degrees Cent after the blower and before the intercooler on the longer tracks. Its that high because I am really running the Eaton m62 too fast in order to get the 11-12psi I need. However water injection might allow me to overspeed it a bit more.

Options are to apply the jet before the throttle to cool the blower and hence keep outlet temps down and perhaps improve sealing or to inject after the intercooler, which of course would just be about charge temp, ( about 57 degrees Cent on a warm day).

Unknowns are what water injection might do to an Eaton with its internal coating, although I would aim to inject it from quite low temps/boost levels. I can afford to do that because its a sprint car, hence dont need to worry about tank size etc.

Other issue is that water might drop out in the intercooler?..no experience of this but if it was just a little thats not too big a problem, again becuase its a sprint car.

Oh, I cant use meth, rules dont allow that.

Cheers
Simon
_________________
Blown is always best!

[fiat22turbo]

*sits back and waits to see what people come up with....*
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[jazz guy]

I have been running water/alc injection for a number of years on my '82 931 and very pleased with its' performance. but my turbocharged non-intercooled setup is different from your application. I have contemplated adding a front mount intercooler though, and wanting to keep the water/alc injection, I've done a little research into nozzle placement. Having read several conflicting ideas, I'm going to mount the nozzles post intercooler, which seems to be the generally accepted area. Here is a LINK to some nozzle placement guidelines and advice from a water/alcohol injection company.

Cheers, Brian
_________________
'81/'81/'82

[gegge]

I strongly recommend water injection AFTER the intercooler. The water will condensate/drop-out. No way around it. The intercooler will work exactly as a dehumidifier resulting in a inter(cooler)pool

Using waterinjection doesn´t do much for power as the intercooler. What it does is suppressing the detonation and pinging as well as allowe a leaner fuel mixture. Then you can raise the boostlevel in order to get the additional hp´s. The intercooler is a heatexchanger and is removing heat, waterinjection doesn´t.

Another solution is spraying water on the front of the intercooler. Use a highpressure pump and not a windscreen washer. A budget solution could be a 12V-230V converter and a ULKA espressomachine pump and you got 10bars of atomized moisture removing A LOT of heat from the IC.

Think Autospeed.com have written several articles about waterspraying the IC and calculated the benefits.
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[simsport]

Thanks but I cant use an intercooler spray for speed events as any external water spray gets a poor response from the startline marshals!

I will give it a go post intercooler but may try it pre supercharger at some point as well (we have an idea for a drainable drop-out tank).

Cheers
Simon
_________________
Blown is always best!

[Euro924S2]

Hi Simon. I have a fair bit of experience and input on WI as I fitted my brothers Devils Own kit on his 200bhp 1.6 MP45 supercharged MX5. He is an active member of the mx5 Nutz club (www.mx5nutz.com) and they have a wealth of experience with WI - free to read the posts - you don't need a log in.

WI isn't that great at cooling the heated compressed air - as said, it is much more useful at quenching the cylinder walls and any hot spots which cause detonation and pinking. It's been commonly said that any percieved drop in intake temperature is due to the water vapor condencing on the temp sensor causing a falsely low reading which is then slow to respond as it has to dry off before regaining it's accuracy.


Basically, pre-supercharger injection has been shown to do bugger all for SC outlet temperatures since most of the heat is contained within the compressed air, rather than the air being heated by the hot supercharger. Doesn't matter to you since your not allowed Methanol but injecting that pre charger is a REALLY bad idea (on some Eaton's) since it strips the coating off the rotors and results in a load of coating blowing through the intercooler and either blocking it up or going through and getting into the engine intake.

Pre- cooler is a poor idea since it drop's out in the cooler so never reaches the engine and thus looses its effect.

Ideally, the general consensus is a single point of injection. Multi point is potentially better until a jet blocks and the cylinder melting is the first thing you know about it!! There are flow sensors available which will monitor the flow rates and warns you if pre set parameters are exceeded. Unfortunately, if one or 2 of 4 injectors blocks, you just get increased flow through the remainders due to the higher pressure so the monitor doesn't register a problem.

Ideally mount the jet before the plenum in a fast flowing section of the track with ideally no tight bends after it. The jet should point downwards between the 9 and 3 positions on a clock to avoid the jet becoming blocked with sedament like oil vapor etc from the breather.

As for mapping, crudely it can just be on/off at a preset boost pressure but for ultimate power a 3d map based on RPM and MAP is ideal since you need WAY more water at 3500 RPM at 200KPA than you do at 6500RPM at the same boost since the knock risk is much less.
To do this you need a high speed valve (£100 ish) and a ECU to control it with a separate map. (I know adaptronic 420C will run it out of the box but I can't remember which ECU your using)


As a suggested alternative, have you thought about an auxilliary air/water charge cooler in addition to your A/A. As you know I'm working on a MP62 install on a 931 similar to yours and this is the route I'm currently taking - moderate sized A/A and then small A/W to suck out the rest of the heat. It's a bit of a odd setup but I think it will work better with the space I have and the access to cooling air through my 944 S2 bumper.

The A/W kit I have is a PACE unit designed to work with the A/A intercooler on a Ford Cosworth.

http://www.paceproducts.co.uk/public_html/php/products_info.php?parent=4&productID=car/rscosworth3

(Its the 3rd kit down, RS500 SPEC. CHARGECOOLER KIT)

Hope thats of some help - I owe you one anyway for the info you gave me!!!!

Cheers, John.
_________________
UK spec '83 N/A with 931 motor with Eaton MP62 'charger @ 15psi. EFI - 565cc inj. Standalone Adaptronic ECU. 951 FMIC. Ally rad. Twin throttle. Recirc valve. Custom manifolds and CAI. 232bhp

[jazz guy]

Hello Simon how goes the progress? I always look forward to hearing your 924 escapades. John (Euro924S2) gave some good information in his post. He mentioned working with a Devil's Own WI kit and the link to the info in my previous post is to a Devil's Own webpage. They have a good piece of experience in WI. I agree with John and the reasons for a more singular point of injection, rather than individual port injection. I actually use two jets but both are in the charge tube well before the throttle body. I have one start spraying at 10 pounds boost and the other one opens at 14.

[Euro924S2]

Hi Brian. Is your charge tube not cooler because some water droplets have collected on the Walls and then removed heat when it evapoates - in a similar way to the in cylinder effects - I guess hot air flowing through a cooled tube will cool the air ala intercooler but I thought it was a minor benefit and much less significant (as u say) than the in cylinder effects, so better to inject a bit closer to the head than way back behind the charger so that water gets into the engine instead of condensing in the inlet.

I'll google the fire now!!

Cheers. John.
_________________
UK spec '83 N/A with 931 motor with Eaton MP62 'charger @ 15psi. EFI - 565cc inj. Standalone Adaptronic ECU. 951 FMIC. Ally rad. Twin throttle. Recirc valve. Custom manifolds and CAI. 232bhp

[Tas931]