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  #11  
Old 20-04-2017, 01:24 PM
theboostshack theboostshack is offline
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Default Re: WMI tuning and results Part 2

Rice Racing, I agree with your findings on CDI being the best ignition set up when using water injection. It's an option will pursue if/when my current system reaches its limits. Until then, I will soldier on and see where it takes me.

Rotrex, thank you for sharing that link. Those are some good results which has definitely got my attention. I have read a lot of your posts on the benefits of port injection and, like myself, most people seem to take a more conservative approach with regards to how much water meth they inject. Based on your advice, and some previous tips from Rice Racing, I will move forward with larger 0.6mm DP jets and a small (50-100cc) post intercooler jet. Taking this into account, what size pre turbo jet would you recommend?

Thanks again for all your feedback guys. It is greatly appreciated.

Cheers.
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  #12  
Old 22-04-2017, 07:49 AM
rotrex rotrex is offline
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Default Re: WMI tuning and results Part 2

Boosting a 1800cc Datsun engine to 500HP I would not call conservative.
When I was trying pre turbo on my Rotrex C30-94 I found that 0.5mm jet gave IAT fluctuations. The sensor was mounted after the charge cooler. this indicates bigger droplets accumulating on the IAT sensor. A 0.3mm jet did not yield such fluctuations.
To me it sounds odd that you run a modern port fuel injection system and then combine it with single carburetor style water injection, but without the manifolds designed for wet flow.
Can be done, but needs a different spray spproach.

Again, skip that post IC jet. I won't do much.exept getting you an unequal water and methanol distribution = unevenly distributed knock and AFR rates across the cylinders.

At your boost level, you would also be well suited for a air assited system such as what riceracing is offering. It would simplify your setup as it gets away with mutiple jets, pumps etc. its very fine mist makes it resonably uniform even trough dry flow intake systems.
The trick is that it starts with a very fine mist, much finer that pressure driven nozzles, and sprays it into the turbocharger. Here a big fraction of the methanol and some of the water will evaporate making the mist even finer. This fine mist, probably better called fog :-), stays reasonably well suspended in the air stream and makes it into the cylinder.

Now you run significantly more boost (3+bar?) and with its much higher exit temperatures. I may swallow a bigger jet with flow rates of 150 or even 250cc/min.

Still at first I would only run DP to see where it gets you.
Rob's Evo in the link i posted did not gain any power anymore with more ignition advance. At his current boost level of 1.85bar tapering doen to 1.55 bar (realtive) he is not knock limited anymore and can run an optimal ignition timing. He achieved this with 4x 0.5mm jets and some 5 bar differential spray pressure, so just some 600ml/min total. He said he will increase boost next.

The total flow of mix only tells you half the story. The other half is how much of this flow rate makes it into the cylinder as actual mist and how well it is distributed.
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  #13  
Old 23-04-2017, 11:19 AM
UCTURBO UCTURBO is offline
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Default Re: WMI tuning and results Part 2

Since my last post here Ive upped the boost to 30ish psi and still injecting 1750cc/min at 50/50. My plug gaps are at 0.5mm with IGN1A coils without ignition issues.

Since going direct port with a heavy shot I wouldnt go back to a single jet. Well I was using around 1300cc pre turbo with an air atomizer but still had distribution issues which caused silly missfires etc since DP no issues. Cheers
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  #14  
Old 23-04-2017, 12:05 PM
rotrex rotrex is offline
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Default Re: WMI tuning and results Part 2

Just had a look at your drag video. For water injection, the AFR was in the 11.2-11.5 range. That is a tad too rich for heavy water meth injection in my experience. Flame speed drops a fair bit that rich. I'd try to not run richer than 11.8.
With 30PSI you should see insane HP numbers. :-)

The more complex and "bended" the intake manifold is, the worst central injection systems become or the more advantageous direct port with well positioned jets gets.
BMW uses 2 jets for their M3GTS with water injection, but have positioned them well in the plenum chamber for good distribution across the 6 runners. They also only spray small amounts and with it add litte extra power.
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  #15  
Old 23-04-2017, 12:14 PM
UCTURBO UCTURBO is offline
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Default Re: WMI tuning and results Part 2

I was thinking I was on the rich side. When you start running plenty of water/meth would there be a point where you start having to aim at a lower afr as it gets closer to a methanol engine running petrol lol? Yes it is making a bit of power lol, Id say up around 700hp as it feels as quick as when it had run 9.6@141mph on a previous setup ( 1jz twincharge ). Cheers
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  #16  
Old 25-05-2017, 02:00 PM
theboostshack theboostshack is offline
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Default Re: WMI tuning and results Part 2

G'day guys,

So I've made the switch back to direct port injection utilizing 140cc DP jets. I also used a 260cc jet post intercooler and a 140cc jet pre turbo. On the dyno, things did not go as planned as the car ran out of injector flow and also developed an inlet manifold leak. I did managed to collect some useful data though:

In the log below, the car was running 20psi boost without WMI. Cylinder EGTs were consistent and pretty much equal throughout the rev range.




In this log, the car was running 32psi boost with WMI. You will notice that cylinder 4 EGT falls to around 40 degrees lower than the rest soon after the WMI is activated.



I have a strong feeling that a lot more of the liquid from the post intercooler jet is making its way into cyl 4 than the other cylinders. I would really appreciate some feedback on what you guys think after taking a look at the logs. please note that in the logs, AN6 - Voltage 0-5V is reading the voltage output from the Aquamist flow sensor.

Cheers.
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  #17  
Old 26-05-2017, 10:39 AM
UCTURBO UCTURBO is offline
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Default Re: WMI tuning and results Part 2

Good to see youve gone back to DP theboostshack .

After hurting a piston at 30psi I decided to do a little research and came across this http://www.turbobuick.com/threads/al....378231/page-3.

It pretty much says with large amounts of meth ( and water in my case ) you need to tune the engine a little richer by the gas afr scale. I had my engine tuned at 11.3 when it hurt it and going by the plug that had the hurt piston it was lean, after putting it back together Ive settled with 10.5 to be safe and the plugs look happy.

You would think the water would cancel out the heat/lean issue but these are my findings, it may not be necessary for all engines but mine needs to be that rich not to hurt stuff. Cheers
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  #18  
Old 27-05-2017, 10:10 AM
rotrex rotrex is offline
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Default Re: WMI tuning and results Part 2

The higher mix percentage you inject the more uniform the spray needs to be. it has litte to do with lambda.

A central injection point is not going to work well past a certain percentage and optimal lambda values for power.
The only exception are engines with dedicated wet flow manifolds from yesteryear with centrally mounted carburetors or central throttle body injection. they were DESIGNED to distribute the liquid fuel reasonably uniform across the cylinders.
A dry flow manifold does not do that.

The work around is to drown the engine in fuel from the (direct port) fuel injectors to keep everything on the rich side.
the other work around is folks using high percentages or even pure methanol.
This also covers up distribution issues as is burns well across a wide range of AFRs with excellent knock properties.
This is why IMHO often people with simple single nozzles systems make more power on meth alone that with a 50:50 mix.
WW2 and F1 in the 80is have shown that 50:50 water methanol is capable of higher power levels that methanol alone. BUT it has to be distributed uniformly across the cylinders.

You probably have seen the engine bay pictures of the WRC Subaru cars that featured Aquamist systems.
What did they use with the modern port fuel injected engines? You guess is: direct port injection with 4 nozzles pointing straight to the head's intake ports.

On a 50:50 mix you lose power once you go richer that 11.8 given you have a uniform fuel distribution. It starts to burn really slowly past that.

if you don't pay attention to distribution, you can have a single cylinder running at 15:1 and the others at some 11:1 leading your wideband sensor to read some 12:1 on average.
This can lead to piston failure.
it is the same mechanism you lose a piston if one of the fuel injectors has issues.

Big power on a large mix flow should go direct port IMHO

Last edited by rotrex; 27-05-2017 at 10:18 AM.
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  #19  
Old 27-05-2017, 10:47 AM
UCTURBO UCTURBO is offline
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Default Re: WMI tuning and results Part 2

Mine was direct port when it cracked the ringlands on one cylinder. Distribution isnt an issue. I think with forged pistons I may not of hurt it, but would've over time had I left the tune. Not sure, maybe my afr gauge is off by 1 point lol. Cheers
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  #20  
Old 27-05-2017, 01:56 PM
rotrex rotrex is offline
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Default Re: WMI tuning and results Part 2

cracked ring lands on hypereutectic cast pistons is a typical failure due to excessive rpm and/or cylinder pressures, i.e. high mechanical loads.
No needs for knock or detonation for that type of failure.
It seems you have found the mechanical limits of your cast pistons then :-)
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