Need advice on injector size with BBSC/AEM

[StGeorge]

Would the BBSC pundits please help with this.

I am an early install but the car has been essentially idle pending upgrading all systems. I have upgraded the fuel delivery (340 gpm), added AEM ECU and dual wideband, Mark's aftercooler, oil cooler, upsized air intake and exhaust (headers/no cats), removed the VVIS, and assorted maintainance.
The engine internals are stock.
I would like to see ~ 9lbs at the intake.

The orginal RC 440 injectors seem inadequate. The AEM allows excellent control of the injectors. So why not oversize (e.g. 650s) and control with the AEM. This would seem to provide great margin for any future tuning--thoughts
The downside of the "ideal" size is pushing the injectors at WOT and future aggressive tuning. What is the downside of oversizing and tuning the injectors with the AEM?

Thanks

 

[Lotus_Esprit]

An engine running rich is better then an engine running lean, running lean can make your engine go KABOOM! while a rich engine is only getting you fewer mpg:biggrin: . on my sti, the stock injectors were 565cc i bought 950cc and i stilled used my stock vf39 turbo + upgrades + ecu + the usually turbo upgrade stuff (did i mention i shoot fames without cats ) .

Does supercharger shoot flames? I dont think they do because supecharger is running the belts but you never know.

Any Turbo NSX shooting flames?

 

[WOODY]

Would the BBSC pundits please help with this.

I am an early install but the car has been essentially idle pending upgrading all systems. I have upgraded the fuel delivery (340 gpm), added AEM ECU and dual wideband, Mark's aftercooler, oil cooler, upsized air intake and exhaust (headers/no cats), removed the VVIS, and assorted maintainance.
The engine internals are stock.
I would like to see ~ 9lbs at the intake.

The orginal RC 440 injectors seem inadequate. The AEM allows excellent control of the injectors. So why not oversize (e.g. 650s) and control with the AEM. This would seem to provide great margin for any future tuning--thoughts
The downside of the "ideal" size is pushing the injectors at WOT and future aggressive tuning. What is the downside of oversizing and tuning the injectors with the AEM?

Thanks

I had my car with intercooled bbsc running 9.5 lbs for a while on RC 500's, no problem. In fact I think I might have them around . If interested PM me...I will give you an insane deal. I dont see the point of the 650's if you are only running 400 rwhp or so

 

[StGeorge]

From what I have read (of course that is always suspect), it seems that the 500s can max out at 9-10lbs WOT or even run lean. Even if they are providing adequate AFR, they are probably at 95%+. It seems that 550s would be true target. However, if I have to buy new injectors my question is why not factor in substantial buffer (600-650) for which the AEM will adjust?
What is the downside?

 

[WOODY]

My BBSC with 9.5 psi measured at the throttle dyno'd at 396 rwhp with a reasonably conservative tune using second gen SSBB. 500 cc injectors were fine for this. I suppose there isnt a problem with sizing up a reasonable amount. The AEM does have very good injector resolution. I would be cautious about " future aggressive tuning" beyond the 9.5 PSI on stock internals, It has failed more often than it has worked.

 

[RON98]

i would run a bigger injector.

run a 750, 850 cc.

its always better to run with more fuel then less fuel.

also depends on fuel pressure.

600 at the crank according to the RC injector calculator at 80% duty cycle and 43 psi needs 6 800 cc injectors at BSFC of .6

im sure we are all seeing higher fuel preasure so we would be getting more fuel.

meh my 2 cents. more fuel is better then less fuel.

when you change over to a bigger injector, the aem automatic injector conversion is no good. you'll have to retune.

most cars fail due to detonation. if you have a sc with out aftercooler youll definitly be getting lots of that and blow your motor.

you can use fuel as a chemical intercooler, i would HIGHLY suggest all of you FI guys look into water or 100% meth injection.

I run 100% meth on all my turbo cars with very very good results in iat and detonation numbers.

meth allows me to run high boost (25-30psi) on 91 octane.

 

[MiamieNeSeX]

The issue with running injectors that are larger than you need is the duty cycle that they will run at. If the duty cycle is to low the injectors loose efficiency. For what you want to do, you could run with Woody's 500s but not larger than 650s.


Armando

 

[Devin@AEM]

I deffinately agree with Armando and Woody - size your injectors appropriately for the HP output. This should help with the quality of your drivability and high load tune regardless of how good your tuner is.

 

[RON98]

only 400hp

my bad. 800 cc calcuation was 600 :biggrin:

 

[StGeorge]

I deffinately agree with Armando and Woody - size your injectors appropriately for the HP output. This should help with the quality of your drivability and high load tune regardless of how good your tuner is.

How precise does the "sizing" need to be. The RC website provides calculation to size, but these require numerous assumptions which may or may not be true. Real world is hard to extrapolate due to variations in FI set-up/fuel delivery/tune, but probably more relevant.

At >$600 a set, it would be nice to get it right.

It would seem reasonable to achieve 400 crank HP with my described system without being too aggressive (given an experienced tuner.)
From what I am hearing, 550-600cc is the window. What, if any, impact does this +/- 50cc have??

Thanks

 

[Devin@AEM]

Not exact by any means, but the 10% injector flow difference you mentioned should accommodate a 10% range in HP.

500cc - 550cc injectors should easily cover the HP range you are talking about based on past setups similar to yours.

 

[NA1MT]

I am running 9.5lb pulley with the RC550 and everything has been fine. Dynoed 380HP

 

[Elite]

The 500's WOODY has are a perfect fit for your stock motor BBSC with Aftercooler. I'd buy those.

 

[swerve2007]

is the aforementioned aftercooler a part of original kit or something purchased afterwards? if so how much is one of those for BBSC?
thx

 

[StGeorge]

Mark Basch produced some of these a number of years after the BBSC release. It consists of a pump and reservoir mounted under the front hood (no spare tire), a school bus heater core mounted in front of the radiator, and the aftercooler mounted between the SC and intake. It also required modification of the SC outlet by Vortec.
The cost from Mark was ~$1,700.

It would not be too hard to reproduce and even improve on this (larger aftercooler)

 

[swerve2007]

thanks,
one more question please- are there any hardware differences between 3.0 and 3.2 bbsc kits?
thanks again.

 

[coldhammer]

I am running 550cc at 8.7 psi on the bbsc and only seeing about 50% max duty cycle.

Definitely dont see the need to go higher than that for what you want to accomplish.

I was making 396 whp with no headers and a built engine but I had to back the timing off some because the iat was getting a bit high. (i have no cooling). Now I am putting down around 360ish with no issues. So with stock compression you shouldn't have an issue hitting your goal of 400.