Need injector size help (Heartbeat SC)
 

I have a question concerning injectors ....

(Sammy has already mentioned the possibility that the LS9 / Bosch injectors that were supplied with my Heartbeat SC may be just about maxed out now).


My car is a 2011 GS with A6 transmission. Besides the Heartbeat SC, the car is completely stock except for a set of 1 3/4" Pfadt headers with cats and a Kenne Bell BAP.

Instead of using the supplied 96mm drive pulley when I installed the SC, I used a 93mm pulley and then had the car dyno tuned ... The car made 535 RWHP @ 6,300 and the AFR was 11.6 all the way through the dyno pull.

Howard Tanner (my tuner) at Redline Motorsports commented that the duty cycle of my injectors was right at 90% at the top of the pull.

I have now removed the 93mm pulley and replaced it with a 90mm pulley and the next size smaller Gates belt.

I don't think that I really need to have the car re-dyno tuned again just for this small pulley change, but I am worried that I might now need the next size larger injectors so as not to go lean (approach 100% duty cycle) at WOT / high RPM.

Of course, if I do install slightly larger injectors, then I certainly would need to have the car dyno tuned again.
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Question:

1. Considering my mods to my GS, do you think I will need to go with slightly bigger injectors, or [should] the standard Bosch injectors that were supplied with the Heartbeat still be ok ?

2. If I do need to replace the injectors, what would be the very next increase in size injectors that I might purchase ? (without breaking the bank) :)

BTW ... The standard injectors that are in the Heartbeat kit is the Bosch P/N: 0280158187 (52 Lb/Hr @ 58 PSI)


Thanks for any and all info you can provide,
Ron

Ron,

I would of hoped all our conversations at the front counter after we calibrated the car would of given you the sense that we are here for continued support.....regardless I will assist in your concerns;

The reason the supercharger companies supply the LSA 52# injector is for

1# is readily available
2# consistency
3# know injector data
4# fits the short height needed for there fuel rails
5# Doesn't requiring scaling in controllers that have a 64 lb/hour limit

However its also supplied with the assumption your running there supplied boost level (6-8 psi), and no other mods. When you start installing a camshaft, long tubes and more boost it all equates to more airflow which needs more fuel flow. This is why we have used up more of your injectors. 90% Duty Cycle is not unreasonable for on time. Its nice to stay closer to 80 but injectors like Injector Dynamics can be run to mid 90's and still be in control.

At your level of mods we would of recommended either the Bosch "60's"; which are 60 lbs/hr at 3 BAR but 74 lbs/hr at 4 BAR which is where the LS runs rail pressure.

Technically if the correct and credible injector data is supplied the swap to another injector should not make a change other then reducing the injector DC.....however I always see variances and prefer to re-validate the calibration when making these changes.

Good Luck!

Howard ..... Thanks a bunch for the info you provided ... I was going to call you about this.

My problem is that since I don't have the necessary gauges installed in my car, I don't know if my GS is going lean at WOT now that I just replaced the 93mm pulley for a 90mm pulley.

I guess the only way to find out for sure is to put the car back on the dyno, get one good pull, and see if it still holds that steady 11.6 AFR all the way up to 6,300 RPM.

.... Maybe I'm still good with the supplied Heartbeat injectors that are in there now.

If I do need a slightly larger injector, I was looking at a set of the FAST# 30657-8 (they are rated at 65 Lb/Hr @ 58 PSI) ...... Looks like they sell for $400 for a set

Here is a photo of the dyno pull after your tuning of the car:

Attachment 48347409

Ron, if you’re changing pulley sizes, you need, as a bare minimum, a wideband in the car before making the change, just so you can see what it does to the AFR. This is especially so if you know you’re close to max IDC already. As I’ve said before, my car ran fine with the 90mm pulley and stock balancer, also with just Pfadt headers and a BAP as the only other engine mods, in similar climate conditions to what you see in Florida, and the standard issue LS9 injectors worked for me, albeit at about their limit (~92-93%, iirc), although the tune was pig rich.
So, I’m not sure that you need to change injectors for the pulley change, but I’m sure that you should have it retuned, if you’re going to see a real benefit and just to be safe. So, if I were you, would take it back to Redline and get them to do a retune (which shouldn’t involve much) after the pulley install.
Now, if you’re going to keep modding the car (and you know you are, right?) and especially if there is a flex fuel conversion in your future, I would just do the ID1050Xs and be done with it. Yes, they’re expensive, but worth every penny, IMV. My most recent logs show that I’m hitting an IDC of just under 90% with those at @ 13.5 psi @ 6900rpm, with a 2.6:1 pulley ratio, 77% ethanol mix, with the PE AFR at a pretty solid .78 (lambda) throughout the run. And I’m maxing the shit out of my Heartbeat setup, as you probably know.

Listen to howard. No reason to do a barely smaller injector like those fast.

Honestly I would go right ot 850x or 1050 ID injectors. Injectors are not a place to save money or cheap out on.

If you were at 90% before a pulley drop, you are probably very unsafe at this point and over 100%.

Thanks everyone for the replies and info you have provided.

Instead of the FAST 65 Lb/Hr @ 58 PSI injectors, which are barely much larger than the Bosch injectors that are provided with the Heartbeat >>> plus, FAST does not provide Tuning Calibration Data ... how about this:

DeatschWerks 65 Lb/Hr @ 43.5 PSI injectors (P/N: 16U-00-0065-8) ... However at 58 PSI these injectors flow 75 Lb/Hr (and they do provide Tuning Calibration Data with these injectors)

Anyone here have an opinion on DeatschWerks injectors ?

I understand the ID1050X injectors are very good, but I just don't want to spend 1,000 bucks for a set of injectors.


https://i.imgur.com/dSeCed2.jpg

.

Don’t skimp on fuel mods. You will thank us later

Why not? Do you value a solid idle? Solid transient fueling? Accurate fueling for voltage differences? Do you care if the car hiccups or doesn't run perfectly just to save $300-400? If you can afford a vette, and a blower, you can afford to run good injectors.

Compare that data to what ID gives and you will see a HUGE difference. That graph above that may need to be fit to your tuning software compared to plug and play data for EFI live/HPtuners with 10+ huge tables of injector data, that all change when you swap injectors.

I would not even consider anything else and just upgrade the injectors, if not the fuel system pumps, at a minimum.

I have a set of FIC-Bosch 70 lb/hr @ 58 PSI injectors on order from East Coast Supercharging ... The car already has a Kenne Bell BAP installed.

Then it will be re-dyno tuned.