PI Equivalent Flow of Stock Injectors

[Redline]

Disclaimer: in pursuit of knowledge/understanding; nothing else.

Backstory - we have a pretty knowledgeable guy on here who insists our DIs are equivalent to ~750 cc/min. I was very confused by this because more reputable sources than him said otherwise. When I kept asking questions along these lines, apparently the "bother" of being questioned was too much for him to take. Outbursts ensued. (This is the little-known "provocation" that started all the foolishness. How DARE I ask!?!?! LOL) /backstory

Let's check out this verbiage, straight from Kozmic's 5th/6th port kit page:



To me, places like Kozmic and PermTuning are going to know more about this than an individual with an Excel spreadsheet. I know Djuosnteisn, for instance, did a ton of practical testing on our fueling system with oscilloscopes/the whole nine yards. Accordingly, I put a lot more stock in what these sorts of sources say rather than the individual on here.

I'm curious if some of the tuners/well-experienced guys on the platform can speak to this, too? Maybe we can get @Jason@DizzyTuning , @Realgib3 , @phate , @rfinkle2, or other fuel-system knowledgeable folks to chime in?

 

[AYOUSTIN]

There isn't a PI equivalent because pressure vs flow is not a linear relationship. It's a root function, so flow per unit of pressure is much higher on PI engines compared to DI.

Doesn't really matter what they're rated at anyway, we know what their limit is.

 

[Jeff23spl]

I'm interrested to know it too.
For myself, i was doing an irrevelant reverse calcul based on peoples often telling we have stock fuel for about 350-400whp and according to some pi injector calculator, It would need 4x600cc of gaz at 45psi to make 450crank hp or about 4x700cc for 400 crank on E85...
So if all of that is right we can estimate at around 3000CC total...
But i also see some logs with inj duty above 100% and i'm not sure of ''how far'' we can go without injecting at the wrong time...Is the Kozmic spec based on 100% duty or above ?

It would be even better if someone providing answers can explain how they get it....

 

[Redline]

There isn't a PI equivalent because pressure vs flow is not a linear relationship. It's a root function, so flow per unit of pressure is much higher on PI engines compared to DI.

Doesn't really matter what they're rated at anyway, we know what their limit is.

Right, so it makes sense that the screenshot I cited above references rail pressure. But what I'm asking is what size PIs we'd need (at average PI system pressure - I know it can vary) to be equivalent to our DIs? Let's say 45psi, for the sake of comparison.

850s are what are mentioned in the screenshot, though unfortunately they don't say operating fuel psi. We probably all know we can actually use PI calculators to figure out how many CCs you need for a given horsepower at a declared IDC. I did so before and ended up with a figure that was much closer to 850cc than 750cc. Obviously if you run your PIs at 90psi, it won't take nearly as large injectors. But some people run them in the 45-50psi range too. That's why I' specifying.
[doublepost=1486061641][/doublepost]

I'm interrested to know it too.
For myself, i was doing an irrevelant reverse calcul based on peoples often telling we have stock fuel for about 350-400whp and according to some pi injector calculator, It would need 4x600cc of gaz at 45psi to make 450crank hp or about 4x700cc for 400 crank on E85...
So if all of that is right we can estimate at around 3000CC total...
But i also see some logs with inj duty above 100% and i'm not sure of ''how far'' we can go without injecting at the wrong time...Is the Kozmic spec based on 100% duty or above ?

It would be even better if someone providing answers can explain how they get it....

The general rule of thumb is that we can get to 370-380whp running ~E25 (which eats up an extra ~12% of our fueling headroom) on our stock DIs.

 

[Jeff23spl]

400-450 crank hp is in the ball park of 370-380 whp...I don't want to debate about dyno type etc.

And usually PI injectors specs are taken at standard pressure 38-43 psi and the calculator i was using to figure out the 750cc was at that pressure.
http://www.deatschwerks.com/resources/fuel-calculators/fuel-injector-calculator

And that one with a wheel hosepower results but no E85
https://fuelinjectorclinic.com/flow-calculator


What is important is that we can estimate an add on of 1x 1000cc gaz injector can give 25-30% more power headroom...

 

[Redline]

400-450 crank hp is in the ball park of 370-380 whp...I don't want to debate about dyno type etc.

And usually PI injectors specs are taken at standard pressure 38-43 psi and the calculator i was using to figure out the 750cc was at that pressure.
http://www.deatschwerks.com/resources/fuel-calculators/fuel-injector-calculator

And that one with a wheel hosepower results but no E85
https://fuelinjectorclinic.com/flow-calculator


What is important is that we can estimate an add on of 1x 1000cc gaz injector can give 25-30% more power headroom...

Good info. Practical experience has shown our drivetrain loss is ~12% on Speed 3s. I'm going to crunch some more numbers given this and a 43psi operating pressure to try to find out what the PI @ 43psi cc/min equivalent would be for our DIs. I did this before, but didn't take a screenshot or anything.

The reason I'm most interested in this is figuring about how much methanol I'll need to run to hit 500whp with E25 in the tank. And because of the chemical properties of methanol, 2cc of it makes ~1cc the power of regular gasoline - it has a good deal lower energy potential: https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent (only about half the BTUs/volume of gasoline). So, for instance, 1000cc of methanol is like 500cc of normal fuel, besides wall wetting in the IM and other factors that can lower the potential power output/volume of methanol too. This give me the info I need to know roundabout what nozzles I'll be running.

 

[Jeff23spl]

Yeah right IT should be enough to give you a good idea of the size and tests will compensate for the error portion of the calculs...

Not sure 1000cc will be enough. And i bet it would be better to use 2 instead of a big one.
But why are you not mixing a little bit of water in it for cooling the charge ? I know it isn't a good idea to inject a lot of water but maybe a 150-200cc in the mix and account for larger injectors.

 

[PURPFOX]

The other key point to remember on PI injectors is most prefer to stay under 80% Ipw. they begin to lose control and become unpredictable. So typical to see up-sizing at least one level above calc requirements

 

[Redline]

Yeah right IT should be enough to give you a good idea of the size and tests will compensate for the error portion of the calculs...

Not sure 1000cc will be enough. And i bet it would be better to use 2 instead of a big one.
But why are you not mixing a little bit of water in it for cooling the charge ? I know it isn't a good idea to inject a lot of water but maybe a 150-200cc in the mix and account for larger injectors.

I tried various combinations of methanol and water content, and I personally found that my car loves 100% more than anything else. Regarding nozzles, I agree: I'll likely use two CM10s (right now I have one, which is 12.8GPH), so two will put me at 25.6GPH, which is ~1600cc. At the point of adding another injector, I may experiment with a little water content again. Thx for the recommendations

 

[Jeff23spl]

Do you have any idea what is the usual pump max flow ? Can it support 1600cc or you would need a second one ?

Btw i'm looking at it for myself too, it is for a little less power but i know the AEM mid size jet (550-600cc?) on a 50/50 mix isn't enough to supply a gt2871 during cool weather...My ringland tell me that...

 

[Redline]

Do you have any idea what is the usual pump max flow ? Can it support 1600cc or you would need a second one ?

Btw i'm looking at it for myself too, it is for a little less power but i know the AEM mid size jet (550-600cc?) on a 50/50 mix isn't enough to supply a gt2871 during cool weather...My ringland tell me that...

My pump can flow 1.3 gallons in a minute, that's 78 gallons/hour. I'll be asking it to flow ~25 gallons/hour. I'll be fine
And I was on a 630cc nozzle before (CM7). It definitely wasn't enough for my setup for my BATs to stay under IAT at redline on a 4th WOT pull, so I upgraded.

 

[Redline]

TL;DR Long post about figuring out methanol needs for my long-term horsepower goals. Get bored by long posts? Stop here...

Alright, it's been a while, but I haven't forgotten about this. So let's do some math to figure out what a reasonable equivalent PI injector would be, operating at 45psi and 80 IDC

First, we know that our stock injectors can support 370-380whp with an ~E25 mix, so long as ambient temperature is moderate (let's say ~75 degrees). Assuming the 12% drivetrain loss, this equates to ~426bhp (@ the crank). Now, when we figure in the extra fueling volume that's required when running E25, we should add ~15% more needed injector flow rate (a reasonable injector scalar is 1.15 for many running E25).

So, let's do more math: 426bhp * 1.15 = ~490bhp. This is what our injectors should be able to support on pure 93, assuming no knock issues, a turbo that can flow enough, etc.; basically, ideal conditions.

So what does 490bhp @ 1700psi DI translate into in cc/min @ 45psi and 80 IDC? According to https://www.injectorrx.com/injector-size-calculator/ , the answer is ~805cc/min port injectors running @ 45psi and 80 IDC. In other words, if we had PI, we'd need 805cc/min injectors running at 45psi and 80 IDC to hit 490bhp. This totals 3,220cc/min.

Interestingly, this is about halfway between what Kozmic and Djuosnteisn said (3,400cc), and what Enki is now saying (3,000cc).

Now the good rule of thumb is to use ~10% bigger injectors than you think you'd need, so a Speed 3 that was port-injected looking to hit 490bhp (431whp) should run ~880cc injectors @45psi. Now bear in mind that my calculations don't even touch on turbo efficiency islands and other influential factors. When those are considered, more (or less) power could be made with 3,220cc on 93.

So following the math step by step, Enki's Excel calculations don't add up. I recommend not telling him this/asking him about it, or you'll get blacklisted. He vehemently dislikes people calling into question his spreadsheets, especially with data from more reputable sources than him (not me, but Djuosnteisn, Kozmic, etc.)

What's the point? Well, it's summed up in here: https://mazdaspeeds.org/index.php?threads/how-much-methanol-or-pi-for-how-much-power.3575/ (basically, what amount of methanol do I need to spray to hit my power goals with an EFR7163: http://www.turbos.borgwarner.com/go/FET6LJ

In other words, I'll need 10% more fueling than is necessary to hit 513whp on a 90-degree ambient day.

So 513whp - 375whp = 138hp difference. How much methanol does it take to support 151hp (extra 10% added in)?

Going back to the calculator, I'm going to find out what size single PI injector would be necessary. And since M1 methanol has almost half the energy potential of pure gasoline, I'll have to double that injector's cc/min rating. Turns out, one 1000cc/min PI @ 45psi and 80 IDC can support 152.38hp. So, I'll need 2000cc/min of methanol. A little simple math with a Google converter tells me that this means I need 31.7GPH.

Now, my CM10 is a 12.8GPH nozzle; 2 would put me at 25.6GPH. Awaiting word back from CM on the flow rates for their CM12s and CM14s (I couldn't find them). Update coming soon...

 

[Sho]

TL;DR

Going back to the calculator, I'm going to find out what size single PI injector would be necessary. And since M1 methanol has almost half the energy potential of pure gasoline, I'll have to double that injectors cc/min rating. Turns out, one 1000cc/min PI @ 45psi and 80 IDC can support 152.38hp. So, I'll need 2000cc/min of methanol. A little simple math with a Google converter tells me that this means I need 31.7GPH.

Now, my CM10 is a 12.8GPH nozzle; 2 would put me at 25.6GPH. Awaiting word back from CM on the flow rates for their CM12s and CM14s (I couldn't find them). Update coming soon...

Confirming your math(that you're pretty close) , it took me spraying 2000cc/min meth through two 1000cc AEM nozzles to hit just over 500whp. I did have 2 gallons of E85 to 10gallons 93 in the tank at all times, which did eat up a little DI headroom

 

[Redline]

Confirming your math(that you're pretty close) , it took me spraying 2000cc/min meth through two 1000cc AEM nozzles to hit just over 500whp. I did have 2 gallons of E85 to 10gallons 93 in the tank at all times, which did eat up a little DI headroom

Sounds like I'm on the right track, then. Thanks for the confirmation. There were lots of variables/steps to get to the end result, but your testimonial is the real-world confirmation I was looking for. Enki is underestimating our DIs, IMHO, at least according to the sources I've cited and the results I got when I crunched my numbers.

 

[Sho]

It honestly would have never happened had I not gotten my injectors cleaned. I was out of fuel at 5psi less boost than I was at to hit 500 before I had them cleaned and the filters and all that replaced. So condition of the Injectors (DI) will play a big part. We were stuck around 450 at the time. The Injectors probably had 180k on them at that point (with over 100k straight miles of running an e85 mix without ever switching to straight 93), before I sent them off to get cleaned and we gained headroom back to turn the boost up more.

 

[Redline]

It honestly would have never happened had I not gotten my injectors cleaned. I was out of fuel at 5psi less boost than I was at to hit 500 before I had them cleaned and the filters and all that replaced. So condition of the Injectors (DI) will play a big part. We were stuck around 450 at the time. The Injectors probably had 180k on them at that point (with over 100k straight miles of running an e85 mix without ever switching to straight 93), before I sent them off to get cleaned and we gained headroom back to turn the boost up more.

Good info again. Thx. Mine have 72k on them, and I switch to 93 usually at least quarterly, besides running some special fuel injector cleaner every so often that's professional-grade/very hard to get. But when the time comes, I'll send off the injectors for cleaning too.

 

[Redline]

Any input from @Jason@DizzyTuning , @Realgib3 , @phate , or @rfinkle2 regarding what PI cc equivalent (@~45psi/80 IC) you estimate our DIs to be? Or maybe information you could share regarding how many cc/min or GPH of M1 methanol you had to use to hit 500whp @ 7,000 rpms?

 

[Jeff23spl]

So the important part is that one
Quote:
So 513whp - 375whp = 138hp difference. How much methanol does it take to support 151hp (extra 10% added in)?

Going back to the calculator, I'm going to find out what size single PI injector would be necessary. And since M1 methanol has almost half the energy potential of pure gasoline, I'll have to double that injector's cc/min rating. Turns out, one 1000cc/min PI @ 45psi and 80 IDC can support 152.38hp. So, I'll need 2000cc/min of methanol. A little simple math with a Google converter tells me that this means I need 31.7GPH.




Even if the result remain the same, i would rather calculate it this way:
138 dwhp = 157bhp + 10% = 173bhp
Calculated back with the web calculator it gives
-824cc of fuel for 100% bhp (1650 for meth)
-908cc for 110% x2 = (1816cc of meth)

80% idc limit of fuel injectors may not be mandatory in the calcul. Injectors heat at high IDC but the meth pump is designed to go 100%. (Some don't even use controler on it but a switch)...So using it just give you another 20% room.

Just not sure if they measure jet flow at atmospheric pressure or under boost in a pipe. A 30psi boost is 30 psi less from your methanol pump. If nozzle are spec at 200psi, you just get equivalent to 170psi meaning you lose something there too. We probably can't say it is a 15% lost but it is probably not that far...

At the end of all this another long post the same 2000CC is still the right size needed...