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Posted: Sun Oct 28, 2007 1:08 pm Post subject: Damn you direct injection!

Damnit! Ran out of fuel! I have officially found the limits of making power in my car. It has 2 fuel pumps, the typical one in the tank, and then a high pressure cam driven pump that feeds the direct injection system. The cam driven one puts out a ridiculous 1700psi, and welp...I maxed it out. No more power to be had from this motor until a new pump comes out. Mad

I suppose I could tweak the throttle plate so it doesn't close, and then I wouldn't be hitting fuel cut. But if I did that, I'd probably run so lean I'd toss the rods out the back of the block.

Maybe add a third pump, and a second set of injectors tapped into the manifold???? Hmm...

The quest for 500+ whp is not over, its obtainable.

Posted: Sun Oct 28, 2007 4:55 pm Post subject:

You may have run out of flow capacity, not pressure. Flow through orifices like your injectors is proportional to the square of the pressure drop, but flow through a positive displacement pump is constant (at a given rpm).

If you're using all of the flow from the pump (no recycle), you need to spin it faster or use a larger pump or put a second pump in parallel.

Posted: Sun Oct 28, 2007 7:09 pm Post subject:

Thats the problem, spinning the pump faster would mean spinning the entire motor faster, which would require more fuel to do so. And then theres the fact that an upgraded high pressure pump for direct injection doesn't currently exist in Mazda world....the injectors themselves aren't anywhere near close to maxed out, they are only running at 25% utilization.

Fuel injection and direct injection are two completely different birds. If I was fuel injected, I could just drop in a 255gph walbro and be good to go, however direct injection requires an insane amount of pressure, so I need to find a pump that can flow more capacity while still keeping the high pressure. Which, as I said doesn't exist. However, with GM, VW, and Mazda making several different models of direct injected vehicles, I'm sure such an option won't be too far off. I just have to make sure I don't get too greedy with power and try to get more out of what I have that I run lean and start to toss my rods out the back of my block onto the highway.

Posted: Mon Oct 29, 2007 2:41 am Post subject:

There's no way to remount the pump with a gear drive?

How sophisticated is the management system that's keeping track of your fuel mixture? Is it likely to be tricked by a change in weather and go too lean?

I certainly notice how frisky my car's V-TEC gets when the weather turns cool and dry.

EEps · Posted: Mon Oct 29, 2007 6:38 am Post subject:

Can't you regear the manual pump? Got a piccie of the shaft? Wink Smile

Posted: Mon Oct 29, 2007 8:53 am Post subject:

<insert shaft joke here>

500 hp in a 4 banger?... I like the idea... but the danger of something seriously breaking/blowing up... I wish I had the funds to not worry about such things. Right now... I'd be happy to get the idle down on the pontiac boat I have now so it won't diesel if I turn it off when it's idling really friggen high

Posted: Mon Oct 29, 2007 1:33 pm Post subject:

JustAnEngineer wrote:
There's no way to remount the pump with a gear drive?

How sophisticated is the management system that's keeping track of your fuel mixture? Is it likely to be tricked by a change in weather and go too lean?

I certainly notice how frisky my car's V-TEC gets when the weather turns cool and dry.

The mazda ecu is actually very smart, which is a good thing, and a bad thing at the same time. It's nearly impossible to crack, but it adapts to certain changes very well.

I suppose regearing the pump is an option, but I'd also have to bore it out to allow more flow. Not exactly something I'd want to attempt myself, as the precision required in doing something like that is pretty extreme.

Slymer, I really don't need to worry about breaking anything provided I have a good tune, this motor is quite strong, comes factory with a forged crank, rods, and pistons. This motor is actually very similar in terms of an SRT-4 in build quality. There are several guys out there pushing 600+ hp on stock internals with a good tune. Even though the motor itself can handle that much power, don't get me wrong, if you have a shitty tune and run lean, you can still toss rods out the back of the block even if you only have 300hp. Seen it happen. There's a guy here in St. Louis with an 05 SRT-4 pushing 670whp on a stock motor, he has a fully built motor sitting around waiting to go in when the stock one blows, but 50k miles later, hasn't had a need for it. He's actually at the point of boring and stroking it out to see how far he can go. Shocked

I don't know why, its an 8 second car already, but this guy is crazy about power. He's already been banned from the track until he puts a cage in it, but he doesn't want to put a cage in it, go figure.

I'm kinda lucky my car ran pig rich from the factory, 10 to 1 air/fuel ratio before I started to toy around with it, which gave me some leeway in getting some power out of it.

I'm not too concerned about the engine, I'm more worried about the transmission. I'm just hoping the transmission quality isn't similar to the one in the Mazdaspeed Protege, that would make me sad.

Posted: Mon Oct 29, 2007 2:49 pm Post subject:

yes... having a good tune is something I'm not used to (driving old V8s that aren't exactly in the best tune). But if it's set up right... you should have good reliability as long as the cooling system doesn't fail. Seen and heard of some wicked meltdowns... err... welding jobs performed inside the engine/tranny.

Posted: Mon Nov 05, 2007 8:41 pm Post subject:

Posted: Tue Nov 06, 2007 6:04 am Post subject:

EEps · Posted: Tue Nov 13, 2007 10:49 am Post subject:

http://www.gmmodernmuscle.com/forums/viewtopic.php?t=2779&postdays=0&postorder=asc&start=0

Posted: Tue Nov 13, 2007 12:39 pm Post subject:

Damn that link is floating around the entire internet...

Posted: Tue Nov 13, 2007 1:20 pm Post subject:

The person who posted that is either BRILLIANT or dumb as a box of rocks...

Posted: Tue Nov 13, 2007 4:03 pm Post subject:

crewsr wrote:
The person who posted that is either BRILLIANT or dumb as a box of rocks...

F'ing retarded comes to mind.

Posted: Wed Nov 14, 2007 6:07 am Post subject:

I'm thinking it was a joke... I think it's funnier that so many people thought the original poster was serious.