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Turn on pressure or turn on psi

Old 09-19-18, 01:56 PM
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Turn on pressure or turn on psi

I am just finishing a near complete over two year rebuild of my 94' FD. I am still sequential with the new Hitachi SP 3KAI's stock-like turbos and have added WMI with a post-IC sprayer and one pre-turbo sprayer each for the primary and secondary turbos. I am using the WMI for longevity reasons and higher boost with lower pre detonation potential. I have multiple additional mods including for thermal management. My question is the turn on pressure on the WMI controller, particularly during the primary only times during normal driving and not racing. I want to conserve my fluid but also want to keep my exhaust temps down but at the same time don't necessarily want to start spraying every time I accelerate from a stop light or stop sign. Should I start around 10 psi or so? 12psi or towards the secondary come on point? Should I start at 5 psi or so and get used to refilling the tank more often. My tank is in the hatch area and is a 3.5 gallon fuel cell type.
Thanks for any advice.
Mike
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Old 09-23-18, 10:37 PM
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Anybody?
Thanks again
Mike
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Old 09-23-18, 11:12 PM
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3.5 gallon (~13L) is a big water tank. I don't actually think it matters from a water consumption perspective. That much water should last multiple tanks of fuel I would've thought.

What are you using the control when the WMI kicks in? If using an ECU programmable output, you're not limited by just boost threshold. You could also limit by TPS and RPM, so that W/M isn't being injected under low loads.

Which brings me to the next point. The main reason I can think of for using WMI both pre and post turbo is out of concerns that the pre turbo spray will hinder spool. You might play around with having the post turbo sprayer come on in lower rpm, and the pre-turbo sprays only to kick in around primary/secondary turbo transition point, once everything is already spooling. Personally, I think a mechanical pre-turbo setup removes all of these issues and is just a much simpler and more reliable system all around. On these setups, the recommendation is usually to have the water kick in at around 8-10psi. 5psi just seems unnecessary for WMI, particular for the pre-turbo position where it could have a negative impact on turbo spool.

Can your ECU log data and do have EGT input into the ECU? If so, you could start with 8-10psi and then monitor boost vs load vs rpm against EGTs to see where you can pull W/M out safely to make the tank last longer.
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Old 09-24-18, 08:35 PM
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Thanks for the reply and insight. I have a AEM controller and plan to use psi to control the WMI. I don't have any EGT sensors to monitor the EGT. I do have a custom made system I developed myself for the secondary turbo. I use a low vacuum switch that detects the vacuum in the secondary turbo air intake pipe. When the secondary comes on line, I found the very small vacuum in the intake pipe will throw the switch, which will in turn throws a small solenoid to turn on the sprayer on the secondary. This is also dependent on the system being already activated by the set boost pressure setting. Therefore, my secondary will never see any spray until it is already producing some early boost. The spray in turn will shut down immediately on seeing the lack of boost or vacuum in the intake pipe. In primary only mode, the primary would see spray depending on the turn on setting, which if I used 8-10 as you suggest, would already be in mid to higher spool range of the primary. Should I even spray until I reach beyond the primary only mode or in the 12 psi range? Is there enough benefit below the 12 psi area to justify the methanol used since pre detonation in this area is a low probability and EGT temps are unlikely to be high on a properly tuned engine with conservative timing? Just thinking?
Mike
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Old 09-25-18, 09:43 AM
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Maybe I missed it but ...
What size nozzles are you using?
What is your maximum boost level?

You have a more sophisticated system than me with a huge reservoir. But for perspective I’m running a boost activated system with a M3 nozzle post IC/pre-throttle body on stock sequential twins. Pump activates at about 1 psi. My reservoir is the stock washer tank...about 3 liters. Depending on how hard I drive it the water tank lasts about 3/4 of a tank of fuel. So I just fill up both at the same time.
I guess the take-away is your tank might last a lot longer than you think unless you’re on the track. Granted I only have one nozzle but your reservoir is about 4.5 times larger.


Last edited by Sgtblue; 09-25-18 at 09:52 AM.
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Old 09-25-18, 08:45 PM
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One correction. I looked up my paperwork on my tank and it is a little smaller at 3 gallons rather than 3.5 gallons.
I intend on running up to 18-19 psi, which the new Hitachi SP KAI's can handle, since their shaft size is 40% larger than the older versions of the stock twins, they have a 15-20% larger internal wastegate, and they have 360 degree seals rather than the older 270 degree seals. I also have custom Forge actuators for boost control. I have a M5 in the post IC position and once each M2's at the pre turbo positions. I expect to spray around 500-500 cc's per minute of a 50/50 mixture. Do these nozzles and the injection amount seem reasonable?
Thanks Mike
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Old 09-26-18, 03:42 AM
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Can't answer whether your nozzle sizes are appropriate. There are formulas buried in the stickys that I used. But a tank full of AI is going to last you quite a long time unless your on the track. And even then....
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Old 09-26-18, 09:18 AM
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Hi Mike,

i haven't researched your turbos but there have always been two issues w the OE setup, the turbos and the manifold. of course you have uprated the turbos but are still left w a restrictive manifold even if ported. both turbos exhaust at each other. when you combine more flow it could be that exhaust manifold pressure (EMP) becomes a major issue. a bit of manifold restriction and you are easily looking at 2000 F EGTs as well as EMP 3X boost. not saying you will but the only way you can rationally manage your setup is with additional instrumentation. i think you need to know your EGT and EMP.

as to sizing/timing... as you probably know an M5 flows 315 at 100 psi. your pump should produce a higher pressure. my pump generates around 135. since delivery is the square root:

135/100 = 1.35 sq root of 1.35 is 1.16 so 1.16 X 315 is 370 CC.

what power do you expect from your setup? what is your fuel injector sizing? what ECU?

.
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Old 09-26-18, 10:22 PM
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Howard,
Thanks for your reply. Yes I know the stock twin setup has limitations, which I did try to address as best as I could. I do have a ported and smoothed exhaust manifold as well as a ported turbo exhaust manifold which should help some. Also, everything is completely ceramic coated professionally, inside and out, to keep air velocity high. My downpipe is ceramic coated and was specially made by SMB in Australia before they went out of business with a larger bellow and 4" down pipe. My cat is a racing high flow 300 cell metal cat from Vibrant with a higher substrate melting point than typical metal cats. My catback is an older RSR 3.5 " feed dual tip. So I have tried to get the most efficient I can be given the inherent limitations.

These newer turbos have been available now for a few years. They are factory Hitachi turbos developed as a better replacement for the Japanese market. They are sold in the US by many of the typical vendors known to many of us such as Rotary Performance and Banzai. They are basically stock like the other versions on the exhaust side. The compressor wheels produce 12% more air, which is beneficial. The main benefit is the ability to run prolonged higher boost due to the larger shaft size and the 360 degree seals. Boost creep is addressed by the larger internal wastegate. I know EGT and EMP will still be an issue. Unfortunately, I didn't place either of the sensors in the manifold. Probably a mistake.

As for the power, this will be interesting to see. I have added extensive thermal management on the intake side. Everything is ceramic coated either for barrier or dispersant. The UIM and LIM are extrude honed, the throttle body is ported by RC Engineering. There is a ram air intake using a front feeding Abflug bumper, feeding an Autoexec custom insulated air intake with a forced air 700 cfm air temp controlled fan. The intercooler is specially designed dual pass SMIC feed directly from the front bumper, which is also coated for increased heat exchange, and is assisted by two high speed Spal 300 cfm fans. The intercooler is also externally cooled on demand by a fan sprayer by 250 psi liquid CO2 from a trunk mounted CO2 tank, which decreases the charge temperature by 60-70 degrees F. In combination with the WMI, I expect the AIT reading may be as low as 5 degree C at WOT. I would be disappointed if I don't at least produce 425 whp at 19 psi. Maybe I am too optimistic, by we will see. I do have all the necessary mods to meet the needs of this power. I have 550 cc primaries and 2200 cc ID secondaries. A rewired newer RP fuel pump. Rewired leading coil and a TwinPower. The engine is a street ported 3mm apex seal motor rebuilt by Chris Ott at RP. I have run the PowerFC on the car since 2004 and I do all of the road tuning since 2004.

Lastly, my WMI system uses a Devil's Own 200 psi pump with the AEM controller and has the AEM Failsafe system in place to monitor flow. I believe I may need up to 500-550 cc total of a 50/50 mixture at WOT. Does that seem reasonable? With the additional two M2's at the pre turbo position, does this meet my needs?

Thanks for everything.
Mike
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Old 09-26-18, 10:26 PM
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Howard, one more thing. What do you think for the turn on pressure setting, which was the original question asked in my post?
mike
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Old 10-08-18, 01:04 PM
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Howard,
Taking your advice, I will add a single EGT sensor. I have a plugged extra O2 sensor bung on my SMG downpipe that is not used, right at the typical stock location. I know a single post-turbo sensor is not as ideal as dual pre-turbo sensors, but it is better than none at all. I have read that in a post turbo location you have to typically add 200-300 degrees F to the readout. Does this change for me since my exhaust and turbo manifolds are ceramic coated inside and out. Add 150-200 degree F?
Mike
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Old 10-08-18, 11:21 PM
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Temp drop should be the same, regardless of thermal lagging, arguably more with the choked turbines as the temp drop corresponds with pressure.

You are aware Marcus and perhaps others are machining the turbine housings and fitting larger hitachi turbine wheels or even fitting complete gt28 (?) Cores to improve turbine flow? Zac from high performance academy in NZ high flowed his own turbos too. He has a build thread on hpa maybe elsewhere too.
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Old 10-13-18, 10:34 AM
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all of the turbo changes V the original spec are in the right direction..

it is interesting to compare the OE twins to a GT35 as it will shift the focus to the real issue.

.................................................. .................................................. ...................compressor area.............................................. .............. turbine area

twins (area is total for the two turbos)........................................... ............................ 5.972............................................. ................................. 5.25

GT35.............................................. .................................................. ................... 6.386............................................. ................................ 5.171

not very far apart as to turbo sizing yet quite far apart re output and way different re EGTs and EMP. it is of course the manifold. no doubt significant efforts have been made to reduce the heat and pressure however the
fact is the turbos turbine flow work against each other! what should be a flow out of the primary turbine wheel directly into the downpipe directly faces the secondary turbine flow! this all happens in a small plenum and the exit from the plenum to the downpipe seems to be an afterthought. you can port all you want but the two turbos work against each other and as output rises EGT and EMP will rise faster.

you have recognized this and have made many good mods to improve things but most will have no effect on your main challenge: EGT and EMP. you have spent lots of thought, time and money on your setup. i believe you owe it to yourself to instrument preturbo EMP and EGT. . all you need is a 0-150 pressure sensor, some stainless steel brake hose and fittings. i recommend Full Function Engineering's sensor protection module that comes w lines and fittings. your Dataloggit can handle it. i ran such a setup with my Power FC from 2003-2012. you need 1 EGT as you should be looking at the system temp. a post turbo EGT will be of no help as you are in uncharted waters. the post turbine and pre turbine readouts vary greatly, from almost zero at idle to often 300 degrees at full power but that is on a very well flowing system not what you have w your manifold.

instrumentation is the least expensive add you can put on your car. especially YOUR car.

i also recommend and run an EGT in the UIM IAT location. unlike other IAT sensors an air temp EGT delivers 4 readings per second and is accurate to plus minus 4 tenths of a %. it operates on the same scale as other thermocouples so would work well w your Dataloggit.

IAT thermocouple discussion (includes P/N) starts on page 152 of the linked Google Drive document,

as to turn on, it is a bit arbitrary and also depends on how you are using your car but i would suggest it start (and hopefully it is progressive) at 9. you should put another pressure sensor in your AI line so you can actually calculate how much is going in your engine.
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Old 10-13-18, 03:30 PM
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Howard,
I unfortunately cannot at this point in my rebuild change the EGT to pre-turbo. I am stuck with post-turbo and will have to see if it helps. I will at least know if my EGTs are getting near any extreme. I bought my sensor from The Sensor Connection, which you have used also. I read your IAT discussion and have a few questions. Can I use an air-temp K couple to feed directly into the Power FC from the stock AIT location. Is it the same response curve? Also, I already have a air-temp K sensor in my Efini crossover pipe leading out of the turbos, like you have done and I also have an air-temp sensor in my Autoexe air box. I will be able to compare air temps from the air box to post-turbo pre-IC to post-IC post throttle body locations. I already have the AEM failsafe system installed on my WMI and will monitor WMI flow and cut boost immediately if pressure drops through the Power FC ground link enabled system.
Thanks
Mike
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Old 10-13-18, 07:29 PM
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"Is it the same response curve?" yes

it will be nice having temp data from your turbos. expect it to be 400F+ at peak boost. maybe not w preturbo AI. i look forward to you getting up and running.

there's nothing wrong w your failsafe re pressure drop and boost response however as we all know if you start to get knock at 6000 rpm you need relief... on the next rotor face.
the rotor faces are going by, AIR, around 60 per second at 9000. how long after pressure drop occurs does the boost cut/reduction happen? the only "failsafe" response to save
a motor is ignition as it happens at the speed of light. (haven't checked that but i will take their word for it)...

there certainly could be a situation where your setup could alert you to something amiss so it is a positive. a knock reactive system dropping advance to zero is the only solution if something
goes really bad.

when i had my PFC i used a J&S Knock system which worked O K. it only worked on the IGL so i was limited to 10 retard running 11 split... but it worked.

anyone looking at a new ECU needs to ask, as THE first question... does it have a windowed, active knock system that can start to function at a certain TPS setting. if it doesn't, expand your search.
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Old 10-13-18, 11:34 PM
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Howard,
The AEM failsafe system is a learning system that stores your flow curve with cc/min on one axis and boost or rpm (in my case boost) on the other axis. Once you store your data after a few runs, it sets up limits below the curve at which point the alarm is sounded. This is user adjustable from as little as a few % to 10% or more. The same limit can be set for a ground signal or even a 12V signal, also user determined, which is immediate when the envelope is breached.. If I set it tight, the risk to the engine would be less but false alarms would more common. I could change this to trigger a relay to cut the ignition, which would be safer for the engine.
Mike
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Old 10-14-18, 09:50 AM
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yes, you could enable an ignition total cut. people say it is hard on the engine however when i was running my PFC on the dyno we had a few and it had no engine effect.of course the actual enable/cut point would need to be sneaked up upon.
it will be interesting to see your IATs. also your knock readings. the PFC/Dataloggit does provide dependable helpful knock info but you always have to be ahead of the trend. knock should be around 50 driving around but should drop as boost rises to around 10. if
you see something different it would be time to figure out what is happening and fix it.
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Old 10-15-18, 01:24 AM
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Just to be clear on ignition cut you need an active electronic system, if you just use a dumb mechanical or solid state relay to cut power to the coils you could effectively fire them at ramdom ignition advance and still have enough energy to ignite the charge. It really needs to be ecu based or an ignition specific system, you probably could adapt something like a retard module aimed at carby turbo v8s triggered by the failsafe output of your injection system, i image they are cheaper and easier to get hold of than j&s gear.
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