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Discussion Starter · #1 ·
posted these questions elsewhere but thought they deserved a stand-alone thread.

does anybody have info about the stock ECU map and what the MAF readings are (% of peak Volts) and what the injector duty cycle is under WOT conditions? never owned a direct-injection engine but I assume it works along the same principles as side-feed injectors. meaning the stock injectors are rated for a certain max flow rate (mass/time) - what is that flow rating? and lastly how's the stock MS3 fuel pump compared to the max injector flow rate?

again, coming from a Subaru background, these were very real limits and concerns when it came time to increase the volume of fuel/air burning through the engine. the WRX was especially limited by its small stock injectors and the fuel pump needed to be upgraded from day-one.

perhaps these questions belong on a thread for a ECU mgmt system like the Xede but I thought I'd raise it here. if this has been discussed elsewhere, I'd appreciate a friendly linky.


edit: opps. probably belongs in a different topic area. can a Mod please move this to "General Powertrain" forum?
 

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Unfortunately, I dont' think the Mazdaspeed 3 community has been alive long enough to report the information you're asking about.

There just haven't been many, if any, doing their own, private research into the technical data of the stock fuel system. And none of the tuning companies have relayed extensive info like this...yet, at least.
 

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Discussion Starter · #5 ·
if anybody can find the published data on "sizes" for the injectors, fuel pump, and MAF sensor (peak) flow rates that would be a good start.

but the kind of insight that I'm referring to here comes mainly from testing and data acquisition during dyno runs. The MAF sensor voltage (typically 5V peak) is captured real-time. You really don't want to exceed about 4.8V peak or you risk running out of calibration range. That means the MAF sensor will not actually sense more air flow (mass) beyond the peak value so the fuel volume (AFRs) can go wacky lean and you burn up the engine real quick.

I'm not saying the stock setup is prone or even close to this kind of situation with simply mods like a CAI and freer-flowing exhaust. What I'm saying is I'd like information about this stuff to KNOW if there's a good reason for concern. I guarantee you it becomes a real concern when you start thinking about high-power mods like a bigger turbo.
 

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Might be too late but, it was discovered/revealed by CP-E that the stock injectors are only putting out 25% of their use at WOT but either the in-tank pump or the pressure pump or whatever its called is causing the power limit of about ~325whp?
 

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[quote author=tvissues link=topic=69882.msg1534296#msg1534296 date=1183440824]
Might be too late but, it was discovered/revealed by CP-E that the stock injectors are only putting out 25% of their use at WOT but either the in-tank pump or the pressure pump or whatever its called is causing the power limit of about ~325whp?
[/quote]

I was going to say the same thing, although when you think about it that duty cycle seems way off. They seem to know their stuff, but 25% doesn't seem right.

So it appears in order of being the most restrictive:

1. In tank electric pump
2. In line mechanical pump
3. Injectors (which if CPE is right, should let you go above 500 hp so, probably don't care about those.
 

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Believe it or not, the duty cycle is in fact that low. I think we have some data logs from our SPEED3 somewhere around here, and if you want I'll gladly dig them up. In a waste case, I have a TON of SPEED6 datalogs, and considering that they're basically the same engine, the data should be representative of the SPEED3.

And to clarify, the high pressure pump is likely the most restrictive component in the fuel system. We don't have data to verify this claim, but a Mazda engineer I spoke with clued me in on the issue when I spoke with him several months ago. He was correct in claiming that the fuel system runs out of mustard at about 300whp in the SPEED6, so I have no reason to doubt his claim that the high pressure pump is the weak link. But, we still plan to verify which pump is checking out early as soon as we get the chance.

Let me know if you guys want to see some numbers and I'll make up some charts.


Jordan
 

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[quote author=www.cp-e.com link=topic=69882.msg1534817#msg1534817 date=1183475351]
Believe it or not, the duty cycle is in fact that low. I think we have some data logs from our SPEED3 somewhere around here, and if you want I'll gladly dig them up.[/quote]
When you said that the duty cycle was 25%, do you mean relative to being on (open) continuously?

The reason I ask is this: Being a direct injection system, isn't there a "time window" in which the injectors can work? For example, I doubt that you would want to fire the injectors during the exhaust stroke.
 

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[quote author=ZooZoom link=topic=69882.msg1216124#msg1216124 date=1171862272]


does anybody have info about the stock ECU map and what the MAF readings are (% of peak Volts) [/quote]

At WOT, the MAF output is typically just over 4 volts.
 

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Discussion Starter · #12 ·
[quote author=www.cp-e.com link=topic=69882.msg1534817#msg1534817 date=1183475351]

Let me know if you guys want to see some numbers and I'll make up some charts.

Jordan

[/quote]


YES! Please post up whatever data you can. It can only be a positive thing to have more information. and Thank You!
 

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[quote author=GT1 link=topic=69882.msg1535335#msg1535335 date=1183494392]
When you said that the duty cycle was 25%, do you mean relative to being on (open) continuously?

The reason I ask is this: Being a direct injection system, isn't there a "time window" in which the injectors can work? For example, I doubt that you would want to fire the injectors during the exhaust stroke.
[/quote]


Yes, you're absolutely right. A traditional port fuel injector can remain open throughout the entire engine cycle (100% DC) because it's spraying the back of the intake valve, whereas these DI units spray directly into the cylinder. So it is reasonable to assume that keeping a DI injector on all the time could create problems. But for the sake of consistency I've kept the duty cycle calculation alone.

To be technically correct, I guess you could double the injector duty cycle value since they can really only inject fuel during the intake and compression strokes at wide open throttle, which is two of the four cycles. Even then, the DC is still only 50-60% on full bolt-on cars, which is good :)

[quote author=ZooZoom link=topic=69882.msg1216124#msg1216124 date=1171862272]
YES! Please post up whatever data you can. It can only be a positive thing to have more information. and Thank You!
[/quote]


Honestly, that's what we want to be here for. We want to share the information we find with you guys so we can discuss what should be done next to the car. It's really a win-win situation. Discussing these things is good for us as a business because we'll make parts that people really need, and you guys benefit because you'll get the products that you want most. So if you guys have any burning questions about these cars, we've learned A LOT through tinkering with the SPEED6, so please do ask if you're curious about something. The worst we can say is that we don't know! ;)

Anyway, here is a datalog of a SPEED6 equipped with a cp-e intake, cp-e turboback exhaust, and Standback engine controller running 17psi:





Jordan
 

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Discussion Starter · #14 ·
Jordan,

thanks for the info. very interesting stuff. clearly the DI injectors aren't a limiting factor for power upgrades assuming they can be judged (capacity/duty-wise) the same way traditional injectors can be.

so this means greater understanding of the fuel supply / fuel pressurization system is needed to know what's required for upgrading to a bigger turbo. the whole high-pressure DI system is obviously a new animal and there's far less "tribal knowledge" of how to work with it. since a dual fuel pump system is employed that makes it doubly complicated.

I know that APS already offers bigger turbo kits for the Speeds. APS is a very reputable company so they must have a full understanding of these issues. Does anybody know if the APS upgrade kits include a higher capacity, high pressure mechanical fuel pump? Or a larger in-tank electrical pump?

Personally, I doubt that I will ever go down the bigger turbo upgrade path. I sold my Subaru Legacy GT after living through two larger turbo upgrades and all the immense expense that comes with the supporting mods. I easily dropped a grand alone on the fueling system upgrades.

Still, I will continue to watch for more information as I learn about what it takes for DI engines. Obviously, DI is the future in performance automobiles.
 

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Jordan,

Dont really know much here but just thinking logically -- Wouldn't the maximum duty cycle on a direct injection engine be roughly 25%?

I am thinking that direct injection engines have a small window for injection due to the compression stroke only being 25% or 180 degrees of the full engine cycle 720 degrees.

There for if you are measuring 25% duty cycle would the injectors be almost tapped out?

Although This link shows that some fuel can be injected during the combustion stroke but it seems that the maximum duty cycle would be rather low on a DI engine

http://www.freescale.com/files/shared/doc/selector_guide/SG2022.pdf
 

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[quote author=BellaBeagle link=topic=69882.msg1541536#msg1541536 date=1183832792]
Jordan,

Dont really know much here but just thinking logically -- Wouldn't the maximum duty cycle on a direct injection engine be roughly 25%?

I am thinking that direct injection engines have a small window for injection due to the compression stroke only being 25% or 180 degrees of the full engine cycle 720 degrees.

There for if you are measuring 25% duty cycle would the injectors be almost tapped out?

Although This link shows that some fuel can be injected during the combustion stroke but it seems that the maximum duty cycle would be rather low on a DI engine

http://www.freescale.com/files/shared/doc/selector_guide/SG2022.pdf




[/quote]It's no different from PI. It's still injecting on the same steps
 

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Jordan,

One other question.

Also if the High pressure fuel pump is the limiting factor. How hard would it be to replace it with a larger pump?

I have read that it is driven off the cam shaft. Dont really know how that would work. I am guessing that it is mechanically driven by a belt or something?

If this is typical for DI cars wouldn't there be other pumps that flow more that may be able to install in our car?

Just looking to see how upgradeable this car is.

Ideally I would like 300 hp to the wheels safely. And the power band to be expanded to red line giving a larger hp range.

But when you get into the higer rpm range getting enough fuel in that shorter time can be tricky.

Any thoughts?
 

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One more thought.....

If we could raise the fuel pressure after the Low pressure (LP) pump but before the HP pump; this "in theory" could raise the output of the HP pump. Maybe we could install a regulator between the pumps that allow this?
 

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It's no different from PI. It's still injecting on the same steps

No, with PI you can be putting fuel into the port when the intake valve is closed as well as when it is open on the intake stroke, (ie the old Bosch K jetronic system).

With the DI system you can start injecting fuel as soon as the exhaust valve closes (intake and exhaust valve overlap happens at the start of the intake stroke, and if you start to inject fuel before the exhaust valve closes you will be pumping raw fuel down the exhaust and you don't want to know how hot your exhaust gas temps will get when you do this)

If the exhaust valve closes at apx 10 deg ATDC intake and the spark plug fires somewhere < 40 deg BTDC compression you have a total of apx 220 crankshaft deg. that you can inject fuel. This is just a rough guess, there may be some detonation problems if you try and inject the fuel that close to the time the spark plug fires but part or the advantages of DI is that it does help cool the air/fuel mixture.

So under perfect conditions you could only use a duty cycle of somewhere around 30.6%
 
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