Injector Size Discussion

[Zmanco]

Fuel: 13 gal. Fuel Cell, Walbro 255LPH fuel pump (haven't bought one yet), 450cc Injectors, Hardwired CSI to work as a 7th Injector, Cold Fusion's Billet Fuel Rail (haven't bought one yet)

 

 

HP: Well the engine is already complete but I still need a few little parts before she can run. After the engine gets properly broken in, I will get the car dynoed. I'm hoping I can get 400HP at the crank (wishful thinking right?).

You might want to use an online fuel injector calculator to check the injector sizing. I don't think 450 cc injectors can support 400 HP, even if it's just at the crank.

[Project Z]

You might want to use an online fuel injector calculator to check the injector sizing. I don't think 450 cc injectors can support 400 HP, even if it's just at the crank.

 

Please note that I am using the Cold Start Injector as a 7th injector. I don't know how Nick is going to do it but it will be hardwired to spray while on boost. Nonetheless, 450cc injectors can actually handle 400 HP at the crank. I plugged in the calculations on the RC engineering website. That's what I will be running but I will be switching to 720cc's once the motor is running and broken in. Turbo will also be replaced later on with a T-66 ball bearing turbo. I forgot to add that.

[garvice]

Why not just start with the bigger injectors? Otherwise you have to tune twice, once with the 450ccs and again with the 720s. I know the second tune will be easier but still a nuisance.

[Zmanco]

Nonetheless, 450cc injectors can actually handle 400 HP at the crank. I plugged in the calculations on the RC engineering website.

I think you should go back and do the calculation again. I just used their site and at 43.5 psi, you need 573 cc injectors to get to 400 at the crank. At 70 psi 450cc is just big enough.

[Project Z]

Why not just start with the bigger injectors? Otherwise you have to tune twice, once with the 450ccs and again with the 720s. I know the second tune will be easier but still a nuisance.

 

Because all I have right now are 450's so once I have a budget for the 720's or maybe I'll just go with 550's, the car will be retuned. I don't want to clutter this thread, let's get back to the topic and I will make my own thread about my build. There you can give me feedback and advice as I will need it.

 

Zmanco: my mistake, the fuel pressure was set at 43.5.

[softopz]

zmanco The calculations differ the megamanual says 440cc will support 400 hp

[Zmanco]

I'm afraid this is sidetracking this thread, but just to clear it up, 440cc injectors will support a NA engine to 400 hp. It will not support a turbo motor, at least according to the various injector calculator sites I've seen. Remember the Brake Specific Fuel Consumption changes and is higher for a turbo motor than a NA motor. That's the difference here.

 

Now back to your originally scheduled programming ...

[BRAAP]

Please note that I am using the Cold Start Injector as a 7th injector.

 

Sorry to chime in off topic, but the quote above scares the bee-jeezers out of me. I’d hate to see you grenade a piston or two or pop the head-gasket, but relying on the cold start injector for fuel supply on a running engine is a very poor choice for a few reasons, location of the fuel being injected and the type of injector it is.

 

1) The cold start injector is not the same in design or function compared to the port injectors.

2) The cold start injectors have no real calibrated flow value, they just squirt "some amount" of fuel into the plenum that some cylinders will get, to aid in starting.

3) Cold start injectors have different spray patterns. I’ve seen vertical straight down on the plenum floor and I’ve have seen some that spray a fan pattern sideways aimed down the throat of the throat of plenum, right past #1 cylinder and just skimming the entrance of #2 cylinder! Those two cylinders WILL be running MUCH leaner with that style if used as a 7th injector!

4) Its function for delivering supplement fuel for cold starting is adequate, but NOT for supplementing fuel flow on a running engine due to the injector design and it's location in relation to the port runners!

 

 

If you are wanting a 7th injector, you are far better off using a regular fuel injector mounted ahead of the TB, between the AFM and TB, as that will insure a more consistent cylinder to cylinder mixture, (though still not ideal as “wet flow” into the first couple of cylinders will be different than the last cylinders, but a far cry better than the OE cold start injector location), and a regular injector is for more consistent in its quality and quantity of fuel delivered, as well as being a known flow rate!

 

Sorry for the tangent, but I couldn’t let this go without at least commenting. Hope this helps.

Edited September 16, 2009 by BRAAP
Typos.

[jc052685]

hum, slowoldcar did about 410whp on 440cc inj. just sayin. Also my brothers integra did 471whp on 1000cc inj on E85.

[Project Z]

Sorry to chime in off topic, but the quote above scares the bee-jeezers out of me. I’d hate to see you grenade a piston or two or pop the head-gasket, but relying on the cold start injector for fuel supply on a running engine is a very poor choice for a few reasons, location of the fuel being injected and the type of injector it is.

 

1) The cold start injector is not the same in design or function compared to the port injectors.

2) The cold start injectors have no real calibrated flow value, they just squirt "some amount" of fuel into the plenum that some cylinders will get, to aid in starting.

3) Cold start injectors have different spray patterns. I’ve seen vertical straight down on the plenum floor and I’ve have seen some that spray a fan pattern sideways aimed down the throat of the throat of plenum, right past #1 cylinder and just skimming the entrance of #2 cylinder! Those two cylinders WILL be running MUCH leaner with that style if used as a 7th injector!

4) Its function for delivering supplement fuel for cold starting is adequate, but NOT for supplementing fuel flow on a running engine due to the injector design and it's location in relation to the port runners!

 

 

If you are wanting a 7th injector, you are far better off using a regular fuel injector mounted ahead of the TB, between the AFM and TB, as that will insure a more consistent cylinder to cylinder mixture, (though still not ideal as “wet flow†into the first couple of cylinders will be different than the last cylinders, but a far cry better than the OE cold start injector location), and a regular injector is for more consistent in its quality and quantity of fuel delivered, as well as being a known flow rate!

 

Sorry for the tangent, but I couldn’t let this go without at least commenting. Hope this helps.

 

Thank you for the feedback Zmanco and BRAAP, let's get back to the thread. As for as both of your guys' concern, thank you but I will make my own build thread and like I said before, I will need everyone's feedback and opinions to make sure I get this thing running right. 400 at the crank is wishful thinking, you guys read too much into it. CSI as a 7th injector, sorry about that; this was my friend's idea to have it hardwired to spray on boost at which I thought about but haven't discussed with him. "Where is it spraying towards and will it be able to spray consistently?" And I also thought of the capacity of that injector being just used for cold starts meaning it sprays very minimal fuel. If anything, I thought of running 8 450 cc injectors but I don't know where to plug the 2 in. I will make the build thread as soon as I figure out what's wrong with my laptop (I'm at work sneaking a few minutes on the board ).