50/50 meth injection start boost
 

I was just wondering what psi some of you guys are starting to inject meth mix? I had mine at 10psi, but just recently bump it up to 15psi. This is with a mechanical pre-turbo injection kit from Wannaspeed.com. My boost is set at 23psi on a 9180 turbo. My thought process is that many people have safely boosted on pump gas to 17-18 psi. What do you experienced guys think?

Thank you,
Jose Nieves

I would set the switch just a bit above your base spring psi. I am using an AEM V1 water meth kit. it has a low level/alarm output wire that I wired to disable my boost controller. If the tank level gets low, I return to a safe boost pressure and no spray. I drive the car a lot and could not live without a level or failsafes. I know the mechanical systems have their advantages, but all the electronic systems do make it easier to keep tabs on things.

you can always fit a level sender to the tank.running mechanical inj doesnt effect having fail safes or not its just the method for injecting

I think you should inject the quantity needed for the air flow at X PSI.

so I would start the injection sooner so that the CC of water and meth are correct at 14 through 23PSI.

You could always ask this question in Wannaspeed's thread:

https://www.rx7club.com/auxiliary-in...wi-kit-807016/

Or you could PM him directly and ask him to chime in here.

I'm just looking to see what the masses have theirs running reliably at higher boost levels. I'm just thinking that running it at lower boost levels can cause a deviation in spool up also. I just don't see there being a problem injection later as this is when problems start occurring, please correct me if I'm wrong. So a differences between 10 and 15 psi and starting to inject a water/ meth mix, in my thinking, should be ok.

while detonation can happen at almost any RPM generally you want the most protection at peak torque which is the location of max combustion chamber pressure. of course you need to start the process in advance.

as far as some safely boosting at 17-18 without AI...

it is not about PSI/pressure, it is about flow.

17/18 w a GT35 is way different than a 9180.

that said, given our 80 cubic inch engines, 400 rwhp is 5.75 hp per cubic inch flywheel... this is no moderate state of tune and it is no mystery why engine s break at this level if they lack AI.

the amount of cooling from the water you are ingesting is subtractive from the fuel but it is very small V the BTUs of energy in the fuel. i have no idea about your specific setup but doubt it should be a factor re power at most levels.

howard

The problem you are stating is you want to start injecting later, that is the problem.

When you start injecting the kit may only inject 20% of the max capacity at this time. so when you are running 18PSI and making 450WHP, the engine should have 300CC+ of water and 300CC meth, for this power range and if you nozzle is say 600CC, you are only getting 20% of 600CC or 60CC water and 60CC meth which is not going to provide the protection you want.

So you need to start injecting earlier to "prime the system" and ensure that when you hit critical levels (400WHP+) that you have the right amount of water and meth at those levels.

I doubt you want to inject it all at once from 0 to 600CC in 1 PSI increment, I would probably ramp it in, from say 12PSI and max at something like 18-20PSI. This should provide good spool up and coverage.

Whatever you decide make sure you have the coverage, in addition, if you are running 50% meth, that is a fuel, so you will need to tune with that as well and then leave it alone.

With mechanical injection, you are at the mercy of the system for flow vs boost pressure. The nozzle rating won't tell you much when you are injecting at 15 psi vs the rated 200psi or whatever.

Best thing would be to set up a graduated cylinder, and measure the flow with water, using a compressed air source, to see how much your system flows. Then you can apply tuning rules of thumb such as injecting X methanol per X fuel at your target boost.

This is what I intend to do with my mechanical injection system, except I'll be tuning check valves and nozzles (no solenoid).

Are you two clowns for real?

1 The most basic air atomiser system like that are either on or off & the flow rate is simply dictated by the boost, else you map it yourself via PWM to a solenoid with appropriate frequency response. There is no "20% at switch on" based on boost. It is on and flowing as dictated by supplied pressure unless metered by a cycling valve.

2 These air atomisers are not rated at 200psi. F_ck me the flow rates between about 0.5- 0.7 bar air & water pressure feed to 4 or 5 bar or higher air and pressure feed (as well as a range of differentials between air and water pressure) at in the spray systems (or other suppliers) online catalogs (for various combinations of water nozzle and cap that are commonly used in these kits). Not only that, but for equal air and water feed pressures (or fixed ratios between them) you can accurately interpolate the flow rate increase/decrease from the table points using the square root of the ratio of increase/decrease multiplied by the rated flow at the given pressure point you are working from.

I'd have to read through the thread again, but I believe Wannaspeed tested the flow rate at different boost levels in the thread I linked.

Thanks for all the replies. Ill stick with starting to inject at 10 lbs preturbo.

I start mine off low at around 5 or 6, it's progressive up to full psi at around 18 psi. Because when the boost is rising quickly like when shifting gears you want it spraying good fast.