Water Injection and IC water spray system for Legnum

[eddyvr4]

Nathan, yes the car has a 530 x 300 x 76 intercooler + intercooler water sprayers + water injection.

Thanks steve - thats interesting and encoraging that my car doesnt neccessarily behave unusually. Yes - the (still unfulfilled) challenge is to see if there is a distinct advantge the water injection can deliver beyond a nice stable intake temp, and maybe a bit of extra confidence on a 'normal peformance tune'. To date i dont think i have proved that. hopefully throwing more water at the problem will yield something more positive.

Ok - i see what you are saying with the injectors re E85 , thats a shame.. i thought modern injectors would be stable well into the low -mid 90% duty cycle, but i dont know why i thought that....wishful thinking

 

[eddyvr4]

So the plan was to firstly log a series of road pulls through the middle of the powerband , through 3rd then 4th gear with and without the water injection and see the diference. The Best i could find nearby was a straight climbing road but with a series of rises and falls, so in the interests of generating as much knock as possible i generally did the pulls on the climbs and shifted to 4th quite early to really load up the engine with the foot right into it, on full boost, where typically you would let 3rd wind out further if you were in a genuine hurry. And as the graph shows 4th is where most of the action was at WRT knock..
　
Under my normal 'spirited driving' with the most recent tune the WI/sprayers, i am now occasionally seeing 3+ knock (My car has the ECU mod where my CEL light will illuminate for knock count of 3+ ) Maybe only 3 or 4 times in a hills blast of 25 min or so. But that still concerns me, - counts of 1 or 2 dont bother me but i dont want regular knock on the CEL, and id like to add more timing as well if possible! So the question is, will almost doubling the injection rate from 170 to 300cc help me? And, getting back to basics, is the water injection really doing much at all?
And here is the outcome: You bet it is!

My analysis:
the water injection + sprayers makes a big difference! (Vs no wi/sprayers)
In the graph with the system disabled (flick switch on dash), there is a lot of knock. (too much!) i had to abandon 3 of the pulls when onto 4th gear because the knock light did not go away and i was worried it could be knocking really badly. (thats basically every run where it did get booted heavily in 4th. the CEL light was on a lot! Looking afterwards on the graph the knock was generally on the way back down when i did lift, but still the knock could have been even worse/longer than what is shown there if id ignored the CEL light and just kept the boot in.

By comparison, going back and doing the run again with the system ON, whilst there was still knock, with the 300cc Wi + IC sprayers, it was a lot less in magnitude and duration. and if you look at the graph you see also i spent more time at 100% throttle as well. Unfortunately there were still a couple of concerning knock events - however the first may (it may not !) have been the nozzle wasnt primed. On the last one this was the most painful run i did for the engine for the night in 4th for about 4 seconds at 181 to 187 load, up an incline with the engine labouring agonisingly from 3700 to 4200rpm @ over 1 bar , and the knock did peak at 6 and come down to 4 (2 deg of timing pulled) on its own before i let off. I wish that one wasnt there, but i reckon on a flat road for example you may not have even have seen it, because it held around that load point for 2 full seconds (with just a little blip of 2 knock) until the knock of 6 occured.. But yeah.. im making excuses...

in terms of intake temps they were 25% reduced (40ish degrees to 30ish degrees) according to my intake temp probe, but i dont think that directly accounts for the reduction in knock (but more later)

So i came back home and made the next alteration. what if we throw even more water in?

the only way i could do that (i wasnt going to drill the nozzle again) reversibly was to blank off the IC sprayers so the pump was driving just the water injection, this should give me a bit more volume. I measured it now at 340cc/min.

so back out to the same stretch of road, same night, and try again . No IC sprayers but 340cc/min injection

The result:

Very interesting... again, the problematic knock on the first run, but excluding that, knock vastly reduced from the initial unnaceptable level to a now acceptable level. Wow!


Clearly (with low outside air temps) Its the WI suppressing the detonation, NOT the IC water sprayers. removing the IC sprayers altogether, and running slightly heavier WI gave even better than previous result. This time on the final 4th gear torture boot up the hill it only knocked a count of 2. Not to poo-poo to the sprayers, but just an indication that on a cold night, they arent neccessarily doing a great deal, and they dont seem to have a great bearing on supressing detonation. They are a good thing, epecially in hotter temps, but not so much for suppressing detonation. Which is what ive always thought.. for once .. vindicated?

However, as always, the car wasnt going to let me triumph without a fight, and of course there was a slight problem. if i kept the boot right in once revs climbed over 5900rpm to 6300 or so and the load dropped below 150, the engine would start to bog down a little bit - sort of a miss/roughness - the tell tale signs of too much water injection..

see the wiggle in the rpm below, only just noticible driving, that is it. you would never know just looking at the graph, but i could feel it mildly in the car.

it wasnt particulary pronounced or consistent, but i did notice it if i took the revs right up.
Note this is above the RPM where my car makes its peak power anyway, i would normally have shifted below this point, however I think its important to see that obviously im starting to approach limits of what water the engine will happily ingest. its interesting its a problem at higher rpm as i thought it would be able to move more water at higher RPM, but i think because the load drops, so the fuel drops, and the proportion of water becomes too high. This, i guess is where staged/mapped Water injection becomes useful.
　
So to summarise:
No water injection - too much knock (on my tune)
300cc WI + IC sprayers = much reduced knock, although still some possible concerns - further logging + work required.
340ccc WI + no sprayers = reduced knock even more, however introduced some stutter at very high rpm.

My initial knock on first power run needs investigation - WI maybe not holding prime / to slow to prime .
　
　
My current tune is already to agressive to cope without the WI, so im not sure there is much room left to get more power, although we can try, currently i have the boost wound back a tad across the board. And weve never tried to tune it with more than 170cc WI, i thought that was enough...

Possibly a more programmable/advanced WI system would help to adjust the volume of water at various load points, this might allow more targetted tuning without too much water when you dont need it.

This testing is no where near exhaustive enough or controlled enough to make really accurate or conclusive statement on what can be consistently achieved. (ie, on a legnum, you can gain 'x' degrees of timing or reduce knock by 'y' counts if you add WI.) Sorry about that. But i think there some good base data to build on here.

As a footnote, The IC sprayers seem to be more effective at keeping intake temps consistently low, (and thus keeping the power output fairly consistent) especially in high ambient temp conditions. (But low intake temps does not mean the engine itself wont get heat stressed if you push long and hard enough, that is where the engine cooling system itself then needs upgrading, but my car does not see the track, its a non issue for me)

However i think i can say with a decent degree of confidence for my car, the WI helps significantly with supressing detonation, and reducing intake temps.
　
　
　

 

[eddyvr4]

Following the above experimentation ive reverted back to the 300cc injection and IC sprayers, & do some more logging, i feel most comfortable with this combination at the moment

i need to see if i can work out why i see above that initial knock on the first power run even with the water injection, firstly if its consistent, and then see if its maybe a priming issue. certainly my system has no sophisticated priming (better systems have a small accumulator tank with water 'pre-pressurised' ready to fire instantly when required, just like fuel injection) . my system just turns on a pump and opens a solenoid at the time the water is required, so its quite agricultural. the nozzle does have an anti siphon valve, but maybe after running on vacuum for a period of time some water is still being 'sucked out' of the nozzle/hose, which would explain why i see a lack of water (and hence knock) on the first power runs above, but not on subsequent ones, because im not letting the engine go back onto vacuum (not for any length of time) between the pulls. Its a theory.

 

[lathiat]

Any chance of taking a video of the intercooler spray pattern? I don't want to go as far as water IC personally which seems to ironically be your bigger push but I definitely want to an IC spray going.

I'm wondering if firing a cone type nozzle sideways is really the best approach. I also think some bumper re-engineering would net much better IC flow. I have race days in mind so a bit different to just the street. Since I have a spare somewhat cactussed bumper I'm thinking of modifying it to expose the IC entirely.

 

[TME_Steve]

Nice write up eddy!

 

[eddyvr4]

thanks Steve.. Trent - have you looked at the pic on page 2 of the spray in action? of course how it performs in dynamic conditions - ie moving at various speeds i dont know, however based on their position, the water must end up on the intercooler one way or another. when stationary, each sprayer throws water right across (and beyond) the full length of the intercooler. In hindsight probably one sprayer would have sufficed.
When i get home usually there is residual water dripping of the bottom of the bumper.

I was able to avoid modifying the plastic bumper or grille at all with my setup. its a bit exposed but ive never had any problem with them getting bent or pulled off.