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Superd00d
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Would there be any advantages of installing new fuel injectors? Or is that just a waste without the right ECU tuning to go along with it? I was just browsing around on MSD's site and read quite a few pages of fuel injectors, fuel pumps, fuel pressure, and injector capacities. Is this anything that would help at all? Could it help even out the lean running tendencies of this engine at all? It even mentioned that running slightly higher fuel pressure would increase the flow through the injectors. Any thoughts?
 

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bigger injectors alone would help very little. If you were to add an aftermarket/piggy back fuel computer with larger flow injectors there is more power that can be easily had with no other mods at all. Higher fule pressure would push more gas through the injectors but the car would soon learn and once again back off the amount of time the injectors are open.
 

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Superd00d
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Discussion Starter #3
This ECU thing sux... that's the entire stage1 upgrade for the SRTs. New fuel injectors and a new controller... 20hp. Someone needs to rip this thing apart ASAP....
 

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Sp00ner said:
This ECU thing sux... that's the entire stage1 upgrade for the SRTs. New fuel injectors and a new controller... 20hp. Someone needs to rip this thing apart ASAP....
Workin on it
Have a "mule" ECM to work from and gathering gear to attempt to offload the code.I was hoping the box was going to be directly compatible with "LS1edit" and some of the other tuning tools out there- but it's too different! :mad:
Right now it looks like it would take a lot of "luck" to just locate all of the offsets and prperly scaled values to make even a minor change (like eliminating/raising the rev limiter which is my first goal)
Anyone here have experience with Motorola BDM??
WOT
 

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Superd00d
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Discussion Starter #5
Motorola BDM? What is that a language or something?
 

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Motorola's Background Debug Mode (BDM) is the best known of the proprietary on-chip debug solutions. It defines a communications standard for interfacing to a debug core via a 10- or 26-pin connector on the target system. A host computer, running a BDM-compatible remote debugger, can communicate with and control the processor through this interface.

From http://www.netrino.com/Publications/Glossary/BDM.html

Sounds like a great way to get some stuff done with the ECU, assuming it's a motorola processor.
 

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Superd00d
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Discussion Starter #8
I did take some classes on programming for this exact kind of embedded system. Well, embedded systems in general, I still have my little circuit board, key, and crap. I can make LED's blink in pretty shapes! ;)
 

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^ ^ ^ i feel ya, LOL.
i don't know ... programmers speak a completely different language- one i do not speak either.
 

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^ ^ ^ i feel ya, LOL.
i don't know ... programmers speak a completely different language- one i do not speak either. I see motorola i think cellphone.
 

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Bigger injectors alone without other modifications or tuning would actually be harmful.

The engine controller is calibrated for a specific injector size. It works on pulse width modulation - First it decides, okay, based on current engine conditions, I need X amount of fuel. Knowing the injector flow rate, it decides, okay, I need to hold the injector on for Y milliseconds.

If you swap that injector with one with a higher flow rate, the engine controller won't know, and will hold the injector open for that same Y milliseconds, which would result in too much fuel. In other words, if you swap a 15# injector with a 30# injector without modifying the ECM's calibration, it will unknowingly inject twice as much fuel. Obviously that's bad.

Fuel pressure works exactly the same. Double the fuel pressure without recalibration of the engine controller, and it'll inject twice as much fuel. (roughly - for you sticklers out there, I know that flow doesn't vary exactly linearly with pressure, but you get the idea)

Besides, unless the stock injectors are up over 90% or so duty cycle, there's no reason to need bigger injectors in the first place.

As far as "evening out lean running tendencies", that's a job for a tuner, not a bigger injector. Correcting from 14:1 to 13.5:1 does not mean you need a bigger injector, it means you need a slightly corrected fuel map. Unless the stock injectors are SOOO overtaxed that they can't even provide a tiny tiny amount more fuel. And I doubt they're that maxed.

In other words, injectors would be useless on a stock motor. Think of it this way - injectors do not MAKE power, they ENABLE power to be made. The stock injectors on the LSJ may be pretty taxed already, possibly only good for maybe 220-230hp. But unless you have other mods that will up the output to that level, upgrading injectors is a waste.
 

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Superd00d
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Discussion Starter #12
DanM said:
Bigger injectors alone without other modifications or tuning would actually be harmful.

The engine controller is calibrated for a specific injector size. It works on pulse width modulation - First it decides, okay, based on current engine conditions, I need X amount of fuel. Knowing the injector flow rate, it decides, okay, I need to hold the injector on for Y milliseconds.

If you swap that injector with one with a higher flow rate, the engine controller won't know, and will hold the injector open for that same Y milliseconds, which would result in too much fuel. In other words, if you swap a 15# injector with a 30# injector without modifying the ECM's calibration, it will unknowingly inject twice as much fuel. Obviously that's bad.

Fuel pressure works exactly the same. Double the fuel pressure without recalibration of the engine controller, and it'll inject twice as much fuel. (roughly - for you sticklers out there, I know that flow doesn't vary exactly linearly with pressure, but you get the idea)

Besides, unless the stock injectors are up over 90% or so duty cycle, there's no reason to need bigger injectors in the first place.

As far as "evening out lean running tendencies", that's a job for a tuner, not a bigger injector. Correcting from 14:1 to 13.5:1 does not mean you need a bigger injector, it means you need a slightly corrected fuel map. Unless the stock injectors are SOOO overtaxed that they can't even provide a tiny tiny amount more fuel. And I doubt they're that maxed.

In other words, injectors would be useless on a stock motor. Think of it this way - injectors do not MAKE power, they ENABLE power to be made. The stock injectors on the LSJ may be pretty taxed already, possibly only good for maybe 220-230hp. But unless you have other mods that will up the output to that level, upgrading injectors is a waste.
The injectors are near maxed, hence the reason I asked. I was also pretty sure that you needed new tuning, just needed clarification. Since the car runs real lean, I was wondering if getting a little more fuel into the cyl's would be a bit helpful...
 

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Since the car runs real lean, I was wondering if getting a little more fuel into the cyl's would be a bit helpful...
If the car is running on the lean side, then yes, more fuel would certainly help.

However, you don't tweak a fueling curve with injector changes. That's like trying to sew a sweater using a hammer. Wrong tool for the job .. overkill.

To correct a slightly lean stock fuel curve, what you need is a guy with a dyno, a wideband o2 sensor, and some software.
 

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Superd00d
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Discussion Starter #15
DanM said:
If the car is running on the lean side, then yes, more fuel would certainly help.

However, you don't tweak a fueling curve with injector changes. That's like trying to sew a sweater using a hammer. Wrong tool for the job .. overkill.

To correct a slightly lean stock fuel curve, what you need is a guy with a dyno, a wideband o2 sensor, and some software.
It's something I read on the MSD website, refering to their injectors. That's why I posted the question. Seemed a little too simple to me...
 

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Sp00ner said:
It's something I read on the MSD website, refering to their injectors. That's why I posted the question. Seemed a little too simple to me...
Yeah, they're I think more referring to a situation where the thing leans out considerably due to the injectors being completely saturated. :)

I would highly, highly doubt that the LSJ, or any other stock car, would be that close to max. The LSJ injectors may not have a TON of room left, but they're not sooo saturated that you can't correct from 14:1 to 13.5:1. Like I said, all you need there is a good tune. :cool:
 

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Superd00d
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Discussion Starter #17
DanM said:
Yeah, they're I think more referring to a situation where the thing leans out considerably due to the injectors being completely saturated. :)

I would highly, highly doubt that the LSJ, or any other stock car, would be that close to max. The LSJ injectors may not have a TON of room left, but they're not sooo saturated that you can't correct from 14:1 to 13.5:1. Like I said, all you need there is a good tune. :cool:
I'm not sure of all the specifics of the injectors, but the Psi-Fi guys said that they were running so close to max that it was scary. MotorMouth did the math himself, he seems pretty good at that, I think someone else did as well, can't remember. It was pretty close man. I should look up the thread, but I'm a lil lazy right now.
 

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Sp00ner said:
I'm not sure of all the specifics of the injectors, but the Psi-Fi guys said that they were running so close to max that it was scary. MotorMouth did the math himself, he seems pretty good at that, I think someone else did as well, can't remember. It was pretty close man. I should look up the thread, but I'm a lil lazy right now.
Yeah, I hear what you're saying. I believe you that they're close. But consider that they still have enough headroom left to be able to adjust slightly and make 14 more hp when a CAI is added, or 20 more when a header is added, etc. If they have enough headroom for that, then they're fine w/ a tune on a stock application. :cool:
 

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i am about to get black and grey and charcoal and spanish gold trible flames down both sides and over the roof (painter has painted for 30 years) for 600$
 

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Superd00d
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Discussion Starter #20
DanM said:
Yeah, I hear what you're saying. I believe you that they're close. But consider that they still have enough headroom left to be able to adjust slightly and make 14 more hp when a CAI is added, or 20 more when a header is added, etc. If they have enough headroom for that, then they're fine w/ a tune on a stock application. :cool:
The worst part is tuning... so far, no one has been able to do it, Psi-Fi claims to be close, but results speak louder. It's been a long term issue with Saturns, the ECU is a SOB to hack and modify. I'm trying to get someone to explain it to me.

I was thinking about the fuel injectors with a full load of boltons, since no one has them yet, there's no telling what would happen. Most people here were appaled at the fact that you couldn't raise the boost with a pulley change without bigger injectors...
 
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