radix power

[zippy]

well, after some work with the fuel pressure regulator we have the 03' fueling the stock pulley rather well. we're going to get a solid tune in there tonight and try the 2.8 pulley. the owner sent his Z06 off to mallet and told us that the SS doesn't stand a chance. TJ told him the truck will beat the Z06 to 60 when he gets it back if we have anything to do with it. on for more testing.

[BenKey]

TJ told him the truck will beat the Z06 to 60 when he gets it back if we have anything to do with it. on for more testing.   

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Hope TJ didn't bet anything worth losing ;) Good luck!

[BenKey]

Thats interesting.  Who did your initial tune?  The stock MAF table scales up to 454 Grams/Second at the highest value, which corresponds to 12000Hz raw MAF data.  You should not "see" or log anything higher than 454g/s or 59.9 lbs/min unless your MAF is scaled differently.  What you can do is log the MAF Hz which will still increase beyond 12000.  The PCM won't be able to calculate a flow rate for anything higher since thats top of the table.

Richard

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Richard,

I saw the same thing as you logging with EFIlive, as I'm sure you are also. Have you noticed that those giving values above the 454gsec/59.9lbmin all seem to be using HPtuners? I can't remember anyone else seeing values above that using any other logging software.

[SSLink]

Thanks, BigTex. So the bottom line difference is that on the '03 and older trucks actual (vacuum or boost) manifold pressure readings are taken to adjust fuel pressure as much as is necessary, while on the '04 and ups the system will only adjust to a preset level based on what it knows manifold vacuum to be at idle and/or WOT. That sound right? Because even if the newer system adjusted to the assumption of a smaller injector, it would boost pressure through that injector to compensate, wouldn't it?

 

I guess imperical evidence like Zippy's is what we really need to test for. We need to find out If bigger injectors help and if we need more fuel pump capacity to drive them. H2Racer's testing would seem to support Mr. Zip's findings, that in spite of what most of us have previously assumed the 42 pounder injectors aren't getting the job done at the power levels of a Radixed LQ9 with a smaller pulley.

[BigTex]

SSLink - Forget what you just typed. How about this:

 

The fuel regulator on the 03 trucks adjust fuel pressure based on manifold pressure. The regulator has a hose connecting it to the manifold so that vacuum (or boost) pressure can alter fuel pressure. The PCM is completely unaware of the changes in fuel pressure, as its mechanically handled by the regulator.

 

The 04 trucks fuel pressure is always set to 58psi. There is no mechanical way for it to adjust to manifold pressure, so the PCM has to handle it. The solution GM came up with is to have a different injector flow rate for different levels of manifold pressure (MAP). The PCM reads the MAP pressure, then looks up the injector flow rate value for that pressure for its fuel calculations.

[H2Racer]

I hooked up the magnacharger fuel pump voltage booster today.  What I found out was not all that I hoped to see.  I have a 2004 H2...

Big Tex: Increasing voltage on an in-tank regulated fuel pump will only keep fuel pressure up, but not increase it any. Any additional fuel flow from the over-driven fuel pump is immediately released back into the tank by the regulator.

 

My response: Right. This addition of the voltage booster was to combat the flow drop resulting in a pressure drop that was happening. It fixed that.

 

I believed I would connect the booster and see my injector time constants drop from the 22.8-23.0 ms time constants that I was seeing at high rpms.

Big Tex: You would not see any less injector time constants unless you made a programming change. Just increasing fuel flow or adding larger injectors wouldn't alter the PCMs injector calculations unless you changed some values in the tuning. It would still open the injector the same amount of time, but you would see a difference in the AFR.

 

My response: I've got a commanded AFR of 10.77 to 1 that couldn't be reached before the addition of the voltage booster. If the 42's could reach it with they would have. It just further proves that 42 lbs are not enough on my combo. The booster closed the AFR "gap" but still didn't reach the mark. As such, they aren't big enough. I actually want a 11.2 across the board but it just isn't going to happen with 42's.

 

Airflow: 455 g/s and 59.4 lbs/min

Airflow: 451 g/s and 59.4 lbs/min

Airflow: 460 g/s and 60.68 lbs/min

Airflow: 464 g/s and 61.26 lbs/min

Big Tex: Thats interesting. Who did your initial tune? The stock MAF table scales up to 454 Grams/Second at the highest value, which corresponds to 12000Hz raw MAF data. You should not "see" or log anything higher than 454g/s or 59.9 lbs/min unless your MAF is scaled differently. What you can do is log the MAF Hz which will still increase beyond 12000. The PCM won't be able to calculate a flow rate for anything higher since thats top of the table.

 

My response: I did all my tunes beyond the stock Magna one. What I have reported is exactly what my HPT data logger spits out. I know you're driving at a error based on MAF rescaling. That isn't the case and I definitely wouldn't post it if it was.

 

 

 

Blanket statements that the 42 lb injectors are or are not enough are worthless without more information.

Big Tex: I think you are right here. Zippy didn't state he was working on an 04 truck until after I made my first post. I do think its safe to say the 99-03 trucks get more out of the 42lb injectors than the 04+ models.

 

My response: I think we're starting to get the good info together on what it take to make the big power out of the Radix. There are several who have already been there and made more but the information shared is full of holes. Maybe I've been able to stitch one of those holes up... maybe not.

 

Richard

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[BigTex]

H2Racer's testing would seem to support Mr. Zip's findings, that in spite of what most of us have previously assumed the 42 pounder injectors aren't getting the job done at the power levels of a Radixed LQ9 with a smaller pulley. 

 

Only for 2004+ trucks.

 

I'm running the heck out of my 2003 Radix'd SS. I've currently got the 2.75" pulley strapped on it, and have basically every mod I can do besides upgraded cylinder heads. I'm pushing well past the MAF limit of 60 pounds and am still running the 42pound injectors.

[BigTex]

Dennis, I see you looking at this thread. How much airflow or HP would you expect from a 12700 Hz MAF reading?

[H2Racer]

H2Racer's testing would seem to support Mr. Zip's findings, that in spite of what most of us have previously assumed the 42 pounder injectors aren't getting the job done at the power levels of a Radixed LQ9 with a smaller pulley. 

 

Only for 2004+ trucks.

 

I'm running the heck out of my 2003 Radix'd SS. I've currently got the 2.75" pulley strapped on it, and have basically every mod I can do besides upgraded cylinder heads. I'm pushing well past the MAF limit of 60 pounds and am still running the 42pound injectors.

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Definitely agree on the 2004 truck point. They are still supporting mine as well but not at the safe AFR I want. I don't like seeing 12.7 to 1 AFR on a FI vehicle. Also, my truck gains power the richer I run it. And to think I don't have a cam or headers yet!

[zippy]

this may be from what you were getting at earlier richard. if the stock 03' fuel pressure regulator is indeed adding fuel pressure under boost acting in the same manner as an fmu then it's increasing the capacity of the injectors just as the procharged truck was seeing. i believe the 42's were rated at 58 or so psi and as you get past that psi number they just get bigger. the 04' on the other hand stay's at the pressure that the pcm and intank pressure regulator allows. this would be keeping the fuel pressure down around where the injectors are still actually only a 42lb injector.

[H2Racer]

this may be from what you were getting at earlier richard. if the stock 03' fuel pressure regulator is indeed adding fuel pressure under boost acting in the same manner as an fmu then it's increasing the capacity of the injectors just as the procharged truck was seeing. i believe the 42's were rated at 58 or so psi and as you get past that psi number they just get bigger. the 04' on the other hand stay's at the pressure that the pcm and intank pressure regulator allows. this would be keeping the fuel pressure down around where the injectors are still actually only a 42lb injector. 

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I think this just may be the truth, Zippy.

 

When I look at a stock 2004 file for my truck I see the injector rating vs KPA scales from 24.49 @ 0 kpa vacuum to 27.10 @ 80 kpa. Looks like the factory scaled the flow that way. However, the Magna tune just sets them at 41.67 across the scale. I haven't altered the flow rating table from the magna numbers.

[BigTex]

H2, email me one of your tunes please. Something doesn't sound right. richard (at) z71.net

 

Zippy, you got it.

[zippy]

so you're saying my theory on that is likely correct?

[SSLink]

So is there any way to boost fuel pressure on the '04's via a programming parameter, or is the answer likely to be to switch to an '03 setup or just go to a larger injector and tune to lean it back some?

[zippy]

i believe the voltage mod will increase the volume, just not sure about the pressure. if this is the case then you just do the voltage mod and go with larger injectors.