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Upgrading the GM900/9-3 fuel system – Information needed

With this post I want to find and gather information about upgrading the GM900/9-3 fuel system. I have heard of several types of upgrades but I would like to find some good links or write-ups that detail how the upgrade is performed and what its benefits are.

I have heard that the stock fuel system can support up to 300 hp. This Saturday I am having my Saab dynode with wide band O2 so I will be able to see how my fuel mixture is doing. The next modification that I am planning is to upgrade my T25 to a T28 so fuel mixture and delivery will likely be reaching the limits of the stock system.

For C900 a lot of people upgrade their injectors and FPR but I only know of one who has done this to a GM900. The fuel injectors for a GM900 SE are 176 ml per 30 seconds, and the fuel pressure regulator is set at 3.0 bars. I have heard of several people who have crushed their FPR to 3.8 bars and I would like to know how this is done. It seems like this should be a cheap and easy upgrade. I also know someone who has upgraded the fuel rail on his earlier model GM900 to a 1998 model. Apparently the later model fuel rails are designed differently and can flow more fuel, but as of yet I have not been able to get anymore information from him.

I am asking for a lot of information, but I want to use it and compile it so that I can display those upgrades on my website.

Thanks
Eric
 

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Re: Upgrading the GM900/9-3 fuel system – Information needed

The 'crushing' of fixed-rate fuel pressure regulators is just that - using a vice or a hammer.
Rising the fuel pressure as much as from 3.0 to 3.8 bar above engine vacuum/pressure will however richen the mixture across the board - to get the idle/light load/low rpm maps back in line the Trionic will need to be reprogrammed. And if you have the Trionic fuel and ignition maps reprogrammed anyways - why not do that while uprating the injectors at the same time?
 

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Discussion Starter #3
Re: Upgrading the GM900/9-3 fuel system – Information needed

Originally posted by Eric van Spelde:
[qb]Rising the fuel pressure as much as from 3.0 to 3.8 bar above engine vacuum/pressure will however richen the mixture across the board - to get the idle/light load/low rpm maps back in line the Trionic will need to be reprogrammed. [/qb][/b]
Although it is the best way to go you do not necessarily need to reprogram the ECU. The cheap (and potentially dangerous) solution is to add resistance to the MAP sensor, up to 300 Ohms. So at 20 psi boost the ECU sees 15 psi and provides fuel for 15 psi, but the fuel is at a higher pressure and is enough for 20 psi. It sounds counter productive but it does allow for higher boost pressures above fuel cutoff. The guy who runs this system also relies heavily on water injection to control detonation, but uses a stock ECU. If I had my own dyno and wide band O2 I would be willing to try this but it is very risky without good data.
 

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Re: Upgrading the GM900/9-3 fuel system – Information needed

Eric Burr once told me about a DIY fuel pressure regulator mod. He'll probably be able to tell you more about it.
 

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Re: Upgrading the GM900/9-3 fuel system – Information needed

If you really do want to adjust fuel pressure, then I would have thought the most sensible way to do it is to purchase an aftermarket regulator that is adjustable and can be set up with an FPR meter. These are widely available from performance outlets. The problem with crushing your standard one in a vice is that (obviously
) it's difficult to change it once you've crushed it...

The only other thing is whether the fuel pump can support the higher pressure/flow rate needed. It will prorbaly also be worthwhile upgrading/replacing your fuel filter for one that has less in-line resistance.
 

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Re: Upgrading the GM900/9-3 fuel system – Information needed

ERP,

Brad at KC Saab mentioned the thing about crushing the FPR. It was a long time ago when he told me this, but I believe he said that the car would be overly rich and run like [expletive deleted] for a while but then the Trionic would start to adapt to it and start to run better again. Maybe you can try e-mailing or talking to him.

Eric Burr
 

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Re: Upgrading the GM900/9-3 fuel system – Information needed

Eric, I am interested in a fuel system upgrade also. Going with what I know about the Similar turbo buick V6, An upgraded fuel pump will no doubt require an AFPR. I don't speak Swedish in any way but, Speedparts.se seems to sell both a higher flow bosch fuel pump and different style Fuel pressure Regulators. When talking injectors, The stock Turbo Buick has an older pintle style injector rated at 28lbs you can safely go to the blue top 36lbs injectors without changing anything. So not knowing what the stock injectors are rated at, I'm theorizing 8lbs over stock would be no problem. The AFPR could probably be set 10lbs over what the injectors are rated at safely also. As a final note, run a thick guage cable to the fuel pump from the alternator, then a thick ground. We call this a "Hot wire" this gives the pump all the current it could possibly want...I have to address something here at work, I can post some Links to related tech bits if you want. Also I'll try and link directly to the parts on the Speedparts.se site for ease of finding.
 

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Discussion Starter #9
Re: Upgrading the GM900/9-3 fuel system – Information needed

Hi Tweek, It’s nice to see you over here. The problem for me is the lack of information that I have on the subject. I don’t know what mods I can do now and get away with and what ones require a new ECU to function. I have heard that the Trionic can cope with up to a 25% change in the fuel system. I got this information from Mike at ValhallaPerformance.com, he has an upgraded fuel rail and FPR, 3.8 bar to the stock 3.0, which will increase the fuel flow by 24%. So after a few runs the Trionic would adapt and performance would increase. He has told me that there is a noticeable increase in performance and I am thing about getting it, the cost is $175.

I just don’t know what should be upgraded; the pump, the filter, the rail, the FPR, the injectors. Okay the obvious answer is all but I would like to find out the most efficient way to go about it. On Maptun’s site they are producing over 300 hp with only an injectors upgrade, which would lead me to believe that the rest of the system is not overly restrictive.

The “Hot Wire” sounds like a good idea, I’ve heard of it before. The nice thing for me is that I have all my amps hooked up in the trunk. So it would be a short run to the pump. Also the pump would have the added benefit of being hooked up to a 1 Farad capacitor for when it really needs some juice.
 

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Re: Upgrading the GM900/9-3 fuel system – Information needed

Maybe the only way to go on this is just to see what happens. $175 sounds good for all those goodies. Once I hear back from the fuel pump people and the Auto Diagnostic people, I can formulate a good list of stuff to pick up. BTW, does anybody know The bosch serial number for the fuel injectors? I have the saab pn but not the actual bosch number. Perhaps this looks like a call to Goldwing is in order. My expirement will be this spring/early summer. I'll pick up an AFPR, Higher flow stock mount walbro and hot wire it, and some injectores set to 10lbs over stock flow. With the Software I'm hoping for I can watch the O2 volts, and Degrees of knock retard to make sure things are going according to plan.
 
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