logalinipoo

Well lets bring up a old topic in a new thread. I have searched a lot before posting

Has any one ever tried attaching this formula to our Cobb AP Injector Scaling.

The Yellows are listed at 425 CC's @ 3 Bar from denso. If you adjust your Pressures for absolute It works out like this

(The square root of (72.5/58))*476=425.75 CC/Min

Reds( I can't find the Manufacturer lising on these.)

(The square root of (72.5/58))*369=330.04 CC/Min

72.5=58 fuel PSI+14.5 Absolute PSI
58=43.5(3 bar)+14.5 Psi Absolute Psi
476= The Bank 2 and 3 fuel injector scale
369= The Bank 1 Fuel injector scale

dannobre

iTrader: (3)

What are you running for injectors? What do you have them scaled at?

logalinipoo

Stock yellows and reds, with 140,000 miles on them. I cleaned them well during the rebuild. Right now they are at Lone star injector being cleaned and flow tested.

Scale
Bank 1=369
Bank 2 and 3=476

logalinipoo

Do you have larger injectors?

Post your injector size, Rated Flow and pressure, andwhat you have them scaled at.

I'll double check my math and See if they are scaled close to the calculation.

TeamRX8

iTrader: (25)

you might as well have thrown money into the trash can as have 140k mile injectors cleaned and flow tested

otherwise you don't have to be overly concerned about scaling them in the grand scheme of things

in the end what they actually flow has a lot of variables; elevation, atmospheric conditions, fuel temperature, ethanol content, etc. so no matter what you use it will never be perfect

logalinipoo

Well yeah I realize that. They flow test when they clean and check them. I am having a problem with major negative fuel trims. So I suspect that one of them might be leaking or sticking open.

I am also trying to understand where the numbers 476 and 369 come from in the stock cobb map. So with a 3.5 Bar and 4 Bar flow test I might be able to confirm my calculations above. It should at least be pretty close.

I wouldn't Imagine that most of those variables will not make a lot of differance, thats why there is STFT to account for. Elevation would have the most, and at 10,000 Feet that is only 4 PSi or so. That would increase the Differential pressure

So it would bring yellows from 476cc/min to 489cc/cmin or 3%

dannobre

iTrader: (3)

Don't try and equate the COBB scaling # as anything relating to actul flow in cc/min or otherwise.

Look at it as a number that needs to be altered to get the expected results..it will make your life a lot easier

Same with most other values in the ATR.....

logalinipoo

I realize that also, but there is a lot of speculation and different numbers on Injector sizes. I see reds posted 280, 290, 310. Yellows I see posted from 380 to 440, even though the manufacturer calles them 425@ 3 bar.

Call it a little bit of OCD. But when I put the actual flow numbers to the yellows they do add up.

dannobre

iTrader: (3)

Just don't think you can throw in a set of 650cc injectors and imput the # and expect them to work..not that simple.

Glad to see you throwing stuff out there though....a lot of this has kinda died on here lately

I think you will have a bit of a tuning curve to get the engine idling properly...once you understand what is happenning you will get it though

PS:..you might want to pickup a set of new injectors ..yours have enough miles on them that I would be surprised if they didn't act strange at the low flow end

TeamRX8

iTrader: (25)

that's all I was driving at, and most of these injector places don't do a thorough evaluation across a brought range of pulse and duty cycle ranges. I would be very suspicious of high mileage injectors having solenoid operation inconsistencies regardless of how they may flow

logalinipoo

No I won't and I appreciate all the help. I would think 650's on stock pressure would be 726.7.

I am working at it bit by bit. I'm going to try to get a good tune by mazda maniac then work from there.

I will be going turbo, how long I don't know. Its more about how the car is running then anything else.

I Want to work everything into place Piece by piece. Get a good tune, Then I can work towards my own MAF scaling and getting similar results.

When I have good stable a/f ratios, Then I'm going to change my intake to what I plan on using with the turbo. That way it can be scaled, Then install bigger injectors. All 4 will be upgraded to keep the latency the same. Then they can be precisely scaled. From there it is getting the turbo and having that diled in.

I want to have a better understanding before it gets a turbo, but I will not be tuning the turbo I'll leave that up to someone who knows what they are doing.

logalinipoo

What do you mean?

logalinipoo

Bump, Come on people. What is your injector size, Fuel pressure and what do you have them scaled to. If you have non stock injectors that is.

FazdaRX_8

iTrader: (1)

you have these backwards, they should read

Yellow injectors
(The square root of (58/72.5))*476=425.75 CC/Min

Red Injectors
(The square root of (58/72.5))*369=330.04 CC/Min

what I think your suggesting is Mazda simply whats a cc/min at the appropriate pressure, this makes sense to me.

Most people are getting KG to "uncap" yellow and blue injectors they test there stuff at 2.5bar
on average uncapped yellows on the reports are around 850cc

72.5=58 fuel PSI+14.5 Absolute PSI
58=43.5(3 bar)+14.5 Psi Absolute Psi
50.75=36.25(2.5 bar)+14.5 Psi Absolute Psi

(The square root of (72.5/50.75))*850= 1015 CC/Min

so in a naturally aspirated car this may work out great, however with boost your actually loosing fuel pressure. due to the boost. as much as 10psi that is why boosted scales are much different especially for the P2 typically your in boost by the time they turn on. so P2 for boosted cars @10psi might look like

(The square root of (62.5/50.75))*850= 943 CC/Min

logalinipoo

The presure Issues could be taken care of with a rising rate regulator.

Or I think the better option would be to move the Baro pressure sensor to the intake post turbo but pre Throttle body with a recirculating BOV. Then recasle the pressures in the latency tables.

The Turbo works by changing the Atmospheric pressure the engine is seeing. If the sensor was in the intake then the injectors would be able to compensate for the pressure.

Also with uncapped injectors the Latency is going to change.

Brettus

iTrader: (2)

Have tuned a car with one - couldn't really see much advantage apart from the extra flow from the injectors.


Can't see that working - the Baro sensor affects calc load and would bring loads up way too high if positioned in the intake.


Yes , UC yellows flow considerably less than what they do on the bench when running on the stock yellow latency table.


As far as the scaling goes - I prefer to go with what actually works in real life rather than work off calcs. The method i use for this on a boosted car involves replicating NA conditions and looking for staging anomalies that become obvious if scaling is wrong.

logalinipoo

I kind of figured as much.


Yeah, I am still real new to tuning. It is just a personal thought, But I remember oltmann finding the partial pressure table and saying that it is affected by the Baro sensor.

It would be real nice to find someone who has a dump of the ECU that would have the calculations and table referances in it. But most of that hex crap is over my head, or maybe I'm just too lazy to get into it.



I agree I would just like to have it close. Can you explain a little more on replicating the conditions?

Brettus

iTrader: (2)

Basically accelerating from a low rpm to redline while keeping the boost gauge as close to 0psi as possible .

It serves two purposes :
1/makes the injector staging points clearly visible (if they are scaled wrong)
2/confirms if you have a boost leak . With 0psi in the manifold Pre throttle boost can be as high as 7psi at relatively low air flow so any boost leak becomes a high % of the total flow past the maf and afrs will go very rich.

TeamRX8

iTrader: (25)

It's a reference number and its only importance is the magnitude relative to your tune and conditions. Trying to justify or analyze the number relative to some theoretical flow rate is a complete waste of time and effort. You analyze it relative to gour tuning requirement and nothing more.