Alky PSI question.

[NY Twin Turbo]

Now that I have my alky psi readings on my XFI, I have a simple question.

I very slowly built some boost on the trans brake. I did a data log to see some basics. I wanted to study the actual initiation of the alky and how fast it ramps up against a slow boost increase. I noticed alky PSI begins to increase the same moment that boost begins to clime above 1 PSI. But until I reach 7 PSI of boost, the alky PSI does not overcome boost pressure. Then, of course, after that it increases exponentially.

Question...... This seems to me that the alky doesn't physically begin to spray from the nozzles until the boost pressure is overcome by the alky pressure. Correct? If both alky and boost PSI's are the same, nothing sprays.

In other words, no alky is entering the intake until after I hit 7 PSI of boost?

If so. That's fine. But it's nice to see and analyze the data and see the exact moments and begin to observe trends. This obviously makes recognizing a problem in the future easier.

 

[Mr.Spool]

I wanted to study the actual initiation of the alky and how fast it ramps up against a slow boost increase

I have played with a lot of different curves,you can increase or decrease the amounts even at lower boost with the controller.the volts really wake up the pump but it still works off the map.

 

[NY Twin Turbo]

I have played with a lot of different curves,you can increase or decrease the amounts even at lower boost with the controller.the volts really wake up the pump but it still works off the map.

I don't think I want to change much with the tune. It's currently a pretty well put together tune.

But, I guess maybe because I run very low boost for standard cruising, it may be nice to actually have the alky working a little sooner. Because otherwise I may not get much of an opportunity to take advantage of it.

But again, the question..........When alky and intake PSI are the same, nothing is spraying. correct?

 

[pacecarta]

you will read pressure from the manifold until the alky comes on and overcomes that pressure

 

[NY Twin Turbo]

you will read pressure from the manifold until the alky comes on and overcomes that pressure

So technically, in my example above, alky does NOT begin to enter the intake track until after 7 PSI. Because it is at this MAP that alky pressure actually overcomes.

 

[SpeedRacerX]

Subscribed

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[NY Twin Turbo]

So technically, in my example above, alky does NOT begin to enter the intake track until after 7 PSI. Because it is at this MAP that alky pressure actually overcomes.

Also, furthermore.......Then "true" alky PSI is always the differential of the 2 pressures.

Example.
Boost = 25 PSI
Alky = 82 PSI
82 - 25 = 52 PSI of true alky pressure at the nozzles.

Not that this stuff really matters much in the big picture. But it's nice to know. Makes understanding adding alcohol a little easier. Because an increase in pressure means nothing unless it's an increase in the differential of pressure.

 

[pacecarta]

i would not say at 7 psi alky is spraying, the pump may be on but until the alky psi is greater than boost there is no flowand if its only 1 psi difference thats not going to spray very well . i have my pump trigger at just under 4psi and try to see at least 75psi ALKY at 15psi boost.

simpler is ..assuming both sensors are accurate.. when alky psi is higher than boost psi ..alky is flowing in.
the actual flow is the alky psi less the boost psi . 150 psi on alky at 30 psi boost is 120 psi of actual alky pressure flowing through the nozzle

same applies to your injectors which is why we run a 1:1 fuel regulator so that as long as the fuel regulator works and receives the proper boost signal on the vac line under boost actual flow through injector can be calculated as injector flow will always be at base pressure ( which also results in a good spray pattern ) regardless of boost

 

[NY Twin Turbo]

i would not say at 7 psi alky is spraying,

This is what I figured. Yes, the pressure of the alky begins to overcome at this point, but I'm still not getting a nice "spray" yet.

If I want a little alky with a good spray pattern down low around 7 PSI then I should be looking for at least a 15 PSI differential. Maybe somewhere around a total alky pressure in the 22 PSI range.

Remember, I have 2 nozzles and I want to be somewhat conservative. But I also want to get a jump on some of the cooling effect during spool up.

So should I increases the initial a little?

 

[SpeedRacerX]

How are you guys measuring Alky psi? Does it take "next level" equipment to measure that?

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[pacecarta]

200 psi sensor logged with XFI , powerlogger could also do it

 

[SpeedRacerX]

200 psi sensor logged with XFI , powerlogger could also do it

Ok, thanks. Sorry to jack the thread.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[X Ray]

This is what I figured. Yes, the pressure of the alky begins to overcome at this point, but I'm still not getting a nice "spray" yet.

If I want a little alky with a good spray pattern down low around 7 PSI then I should be looking for at least a 15 PSI differential. Maybe somewhere around a total alky pressure in the 22 PSI range.

Remember, I have 2 nozzles and I want to be somewhat conservative. But I also want to get a jump on some of the cooling effect during spool up.

So should I increases the initial a little?

The alky pressure does not overcome boost pressure...the system turns ON when the 3 bar measures the 7-8 psi mark then gradually increases with additional boost.
The pump will overcome any boost pressure it is given.

With this Alky control 3 bar simulator that checks your pump ...I measured 30-40 psi at 7 psi boost when it turns on and 70-90 psi at 11 psi boost and around 140 psi at 15 psi boost.
I hope this helps or I completely misunderstand your question .

 

[NY Twin Turbo]

I hope this helps or I completely misunderstand your question .

I think you did a little.

No. What I was saying earlier is basically exactly how Paul already put it into words. (See below quote)

"simpler is ..assuming both sensors are accurate.. when alky psi is higher than boost psi ..alky is flowing in.
the actual flow is the alky psi less the boost psi . 150 psi on alky at 30 psi boost is 120 psi of actual alky pressure flowing through the nozzle"

I understand the pump will always overcome boost. But, in the very beginning of "turn on", when pump pressure begins to rise, it takes a moment or 2 before pump pressure equals and then overcomes boost pressure. During this time, no alky is flowing yet even though the alky psi is showing up on the screen. And it is this time I am trying to minimize. Basically I may try to begin a small spray that starts happening right from the beginning.

I'm sure this will be accomplished once I get in the car and test and log. But I won't get a chance until the weekend. So, I figured I ask for a little advice first.

Oh, by the way. This data log was done while building boost very slowly over 10 seconds of recording. So I was able to observe exactly how the alky responds to each additional PSI of boost.

 

[X Ray]

The only thing I do to minimize the time, is prime the system with the test button. Anything else for my vehicle is not needed.

 

[pacecarta]

i run two 10gph nozzles . and the system should be primed with the test before a pull or a run , i do it before i move to the waterbox and watch for the correction to swing or the car to bog

 

[Mr.Spool]

But, in the very beginning of "turn on", when pump pressure begins to rise, it takes a moment or 2 before pump pressure equals and then overcomes boost pressure. During this time, no alky is flowing yet even though the alky psi is showing up on the screen. And it is this time I am trying to minimize.

this depends on the internal controller settings.its setup usually progressive but you go in to the controller and move the initial over and it will make it instant trust me.

 

[NY Twin Turbo]

this depends on the internal controller settings.its setup usually progressive but you go in to the controller and move the initial over and it will make it instant trust me.

Yes. I certainly will be playing around with the settings a little.

Setting up the alky a few years ago with readings off the XFI correction and air intake temps worked just fine. And I should just leave it as is. Because it's quite obvious that there was not much to correct anyway. My car's pure street performance is currently beyond my expectations and driver capability anyway. But given the ability to see a little more, sometimes I just can't resist the temptation to tinker.

Also, I always prime the system, and prime it well. My tank and pump are in the rear of the car. This is not an issue related to my alky data log observations. When I go into boost, the alky is at the nozzle ready to go.

 

[NY Twin Turbo]

Ok, thanks. Sorry to jack the thread.

Sent from my SAMSUNG-SM-G900A using Tapatalk

Don't sweat it. Not jacking at all.

Paul (pacecarta) had posted some good info in past threads about alky pressure sensors. I finally got around to installing one this winter. I screwed up the install at first and he gave me some advice to get it right. That's what has led me up to this point.

The hardest part about having additional information is knowing you will now need to take advantage of the new found knowledge and f*ck with everything.
Ignorance is bliss.

 

[Mr.Spool]

But given the ability to see a little more, sometimes I just can't resist the temptation to tinker.

if the car has no knock with a good afr and runs real good I would leave the curve alone.