injectors for high hp pump gas

[zilo900]

I wanted to know if I should be going with 850cc injectors, or something bigger

 

[andymoraitis]

I apologize if I'm talking out of turn and you already know this, but as long as the injectors are providing adequate fuel supply at a reasonable duty cycle (85-90%), the size of the injector you choose will have no bearing on how much power you can make or how fast you can go. Please allow me to extrapolate:

Pump gas has poor knock suppression therefore in the presence of adequate fueling as mentioned above, the bigger issue is the maintenance of low intake temps and putting a motor combination together that has excellent volumetric flow. Take the time to choose component assemblies like cams, intercooler, exhaust and intake parts wisely as these will also have an immense impact on how the motor flows and how the parts work in concert.

As your stage, I would also be concerned with adequate fuel supply to the rail. A setup of that nature may necessitate two 255 pumps or a larger Aeromotive unit although a bit of research into some 10 second combinations on the track times page might reveal diferently. Also take the time to speak directly with Forced Performance and listen carefully to their recommendations.

Off the cuff, 950's or 1000's are suitable for your application and will provide some headroom if you plan on going larger. With DSM Link, you can pretty much run whatever you want and have it idle like a stock 450 through deadtime and global adjustments. Just keep the entire picture in mind and you should easily be able to meet your goals on a good tune and good driving, especially the 11 on pump gas.

If you want an idea of a mismatched system that's not operating at optimal flow, feel free to take a look at mine. The lack of a frontmount, better clutch or an upgraded intake manifold certainly isn't helping matters and is more of a choke point than anything else. Can I go fast with my parts? Sure, but it's not the most optimal setup and I know it. Think big picture and you'll be in good shape.

Excuse the novel,

Andy

 

[Kevin Jewer]

The thing to keep in mind is that you can never flow more air than the turbo can provide, no matter how much or how little power you make or what the rest of the setup is. So I always size fuel system components to the turbo's max flow capacity. In this case, 65 lbs/min. I've proven a 255LP rewired to be completely inadequate at 64 lbs/min (13.5:1 AFR and a blown motor), but an HP rewired will do it. I too would suggest some fuel delivery upgrades since the HP will be close to maxed out. FIC 950s work great at this level, IIRC, mine were at 84% IDC at that 64 lbs/min with a target AFR around 12:1. And with DSMlink, the FIC 950s run so well I went straight to 950s on the EVO even though I'm still on the stock turbo. In your case I definitely would not go any smaller, and I don't think going bigger will get you anything.

 

[Dark_Horse]

With DSMlink, I think you should go as big as you can stand. If nothing else, it gives you room to grow if you decide that a GT35R is too small.

The biggest size that provides good daily drivability for everyone seems to be FIC 1150cc injectors. People do run 1600cc injectors, but there are reports of poor partial throttle performance. Then again, there are people that say their 1600cc injectors drive just like the stock ones did. With 1600's, it seems to be hit or miss, though it could be that the ones reporting poor part throttle performance don't have their global exactly correct.

 

[Tom N]

I ran 11`s on pump gas using a evo316g and fic 850`s if that helps you any.
If you want 1600`s I have a brand new set of them I`ll sell you for $250.

 

[Rice Over Wheat]

With DSMlink, I think you should go as big as you can stand. If nothing else, it gives you room to grow if you decide that a GT35R is too small.

The biggest size that provides good daily drivability for everyone seems to be FIC 1150cc injectors. People do run 1600cc injectors, but there are reports of poor partial throttle performance. Then again, there are people that say their 1600cc injectors drive just like the stock ones did. With 1600's, it seems to be hit or miss, though it could be that the ones reporting poor part throttle performance don't have their global exactly correct.

Sorry to interject here, but if injectors that size offer good daily drivability, why was FP's tech guy trying to talk me into 550s when I wanted the 650s? I still bought the 650s since they were sold out on 550s, but he was saying that my ride would suffer the larger I went.

 

[andymoraitis]

If you were tuning with an AFC, that's why FP would have told you to run the smallest possible injector to meet your goals. As you compensate for larger injectors the airflow subtraction required to make them run like 450's skews the timing maps. If you were tuning with any kind of piggyback their recommendation makes perfect sense.

Edit: Looking at your mod list, they made the right call. 650's are doable, but not fun on pump gas.

 

[Rice Over Wheat]

Ah ok, that makes sense. But if 650s baseline is -30%, I still have 20% more margin to work with right? Starting to wish I never got the SAFC as it seems it's going to have to be tossed out soon for some real management. I need to get DSM link.

 

[andymoraitis]

It's not how much an AFC can correct for that's an issue. It's the fact that the more you subtract, the more you raise the timing to knock inducing levels. It's a flaming piece of trash as a sole tuning solution as far as I'm concerned.

 

[Rice Over Wheat]

Yes, well I didn't foresee myself increasing my mods this much. With just the t28 on 450s and smic, I thought it was sufficient. My optimum tune was -5% at 15psi.

 

[Tom N]

It's not how much an AFC can correct for that's an issue. It's the fact that the more you subtract, the more you raise the timing to knock inducing levels. It's a flaming piece of trash as a sole tuning solution as far as I'm concerned.

I couldnt agree more.

 

[oztofrdm]

Well the first couple weeks that i had my 35r setup togther i had it tuned on race gas to 28psi on 110 octane and managed to pull a 11.66@120

Now that time has passed and i have had time to mess around with the tune and i have gotten about 27 psi on 93 octane with no knock what so ever. and on race gas now i have maxed out my 30psi gauge so i think im running around 31-32. So i need to get back to the track and see if i can get alittle deeper into the 11's

All of this is done on denso 720cc's, safc2, gm-maft, and chiped ecu. The next things im planing on doing is upgrade the fuel lines and install a inline pump, and i might get dsmlink.

 

[Kevin Jewer]

Ah ok, that makes sense. But if 650s baseline is -30%, I still have 20% more margin to work with right? Starting to wish I never got the SAFC as it seems it's going to have to be tossed out soon for some real management. I need to get DSM link.

In addition to Andy's point, that -30% is only to get back to the factory 9.5:1 maps You typically need another -14% or so to get to 11:1 for pump, and closer to 21-25% to get into 12.x:1 for race gas. I remember back in the old days when people would downgrade from 650s to 550s and go faster, because they would then have enough range to lean out fully on the race gas.

 

[Rice Over Wheat]

^^^

Thanks for the info. I won't be running race gas however...it's just too expensive and I don't go to the track.

Zeitronix and DSMlink are next on my list of upgrades.