Anyone have a list of a few of the part#'s from the tops of 454 injectors and flow rates to match? I have a couple of sets with no visible color code.

 

http://www.crossfire.homeip.net/cfte...ID=18&CAT_ID=1

 

So using that sights info I find that mine are 11-93' 129 ml/cyc

Injector sizes: (in ml/cycle)
350 CFI Rear: 114
350 CFI Front: 111
350 2bbl truck: 103
454 2bbl early: 124
454 2bbl late: 129
305 F-body: 91
305 CFI Rear: 101
305 CFI Front: 100

what is a cycle's timeframe and what DC, what pressure, is that rated at?

 

I will guess DC is 80% and FP is 12 lbs. Somewhere a while back was the open time in msec. It was referenced as a maximum allowed/RPM B4 static occurs. I might find it. will search.

 

Grumpy said:
just for being easy to use.
At 6,000 rpm.
Divide by 60
so you have 100 revolutions per sec.
or
.010 secs
means
10 msec.
The above is for a batch fire system.
To read 11.5 at 5,800 rpm means the injectors are static.

If you remember 10 msec at 6,000 rpm., doing the math gets easy. 20 msec at 3,000, or 100msec at 600 rpm, etc.

So the injector has a ceiling of <10 msec?

 

Grumpy again:
At 6,000 RPM you have 10 msec between injector firing.
You don't want to exceed a 90% under those condition. So at 6,000 RPM you can't exceed 9 msec injector on times.

At 3,000 RPM you have 20 msec, since the engine is operating at half speed compared to at 6,000 RPM so you have 18 msec available at 3,000 RPM.

 

All those #'s are meaningless if I don't know what firing strategy the pcm uses in Asynch. I've been told it is a non referenced 12.5 msec interval, wich puts 90% DC @ 10.7 msecs. Would love confirmation/denial of this theory.

In regards to the injector lbs/hr rate itself, the reason I'm asking is that if I use a flow calc with modded pressure using the posted rate to start with, PW ends up being too small for fuel needed. Leaves me questioning the original figure/rate.
Also in one of the 454 bins the inj constant list the rate @ 68 lbs,not 75, so i'm not sure what figure to use as my starting constant.

 

Asynch "both" injs are firing at 12.5 msec. In synch inj's fire at each DRP?

 

Might be easier if you just post the numbers off the injectors you have at hand.
I know a few ( very, very few ) but there are others who know nearly all of them.

 

At 6,000 rpm you only have 5 msec between injector firings. To stay under 80% DC, you have 4 msec. TBI injectors fire twice per crank rotation or 4 times per cam/distributer rotation, in an alternating manner.

Async is one injection event firing BOTH injectors every 12.5 msec.

By 90% DC, you are already losing control of the injectors @ high rpm.

 

Soooo.....Are the injectors rated @ 80% of the 12.5 msec asynch strategy and 12 psi, or something different ?

 

Question:

In PE does an injector fire "synch" or must it be "asynch" for PE?

If possible to be in PE and fire synch at what point does the injector flip over to asynch? Would that be when the DC approaches 85%? IOW if I am in PE at say 4000rpms and I rev up to 5000 rpms would not PE need to utilize asynch to properly fuel commanded A/F?

 

Fast Quote:

At 6,000 rpm you only have 5 msec between injector firings. To stay under 80% DC, you have 4 msec. TBI injectors fire twice per crank rotation or 4 times per cam/distributer rotation, in an alternating manner.

Ron says:
I am confused. I believe your statement to be accurate. But as far as static goes each injector has a 10 msec interval B4 it needs to fire again. Is that correct? If one had a single TBI injector rather than two then 5 msec would be time frame they would need to meet to not be static.

Funny this post came up as I was trying to do the calc on paper last weekend.

 

To the best of my knowledge and belief, TBI injectors are rated at 13 PSI and static. Firing strategy doesn't matter.
It becomes a question only when you run out of time to move the pintle, which happens somewhere 85-90% duty cycle at high RPM. I've heard at that point they just kinda buzz, half-way between here and there, resulting in about half their rating, and a dangerously lean engine.
Since I've seen my duty cycles exceed 100%, knowing that anything above 80 or 85 is questionable at best, and damaging at worst, especially under sustained operation, it was time for a booster pump. Now, there's control. Good enough for now.
----------
NO !!

It means that each injector has a total of 5ms, during which time it must turn off, and turn back on to rated flow. Likely BOTH injectors are on for 4 of those 5ms.
Somewhere in the middle of one injectors sustained 4ms on, the other tries to turn off, and turn back on again. For most of the time, both are flowing their full rated capacity. When they start to buzz, then you have a problem.

 

Please respond to this...

Lets assume synch mode.

msec "clock" starts at 0 msec and injector #1 begins to fire.

it cycles and recovers(for lack of a better word) at 4.5msec(so it is available to fire again).

inj #2 fires at 5.0 msec same as above and recovers at 9.5 msec.

inj #1 fires again at 10.0 msec on the clock. In the mean time inj #1 is dormant/inactive (for lack of a better word) from 4.5 msec to 10.0 msec.

What prevents inj #1 from using all ten msecs to recover?

 

You have just rather accurately described a 45% duty cycle at 3000 RPM. Now think carefully, and describe 90% at 6000.

 

Visual aid:

 

Grumpy said:
just for being easy to use.
At 6,000 rpm.
Divide by 60
so you have 100 revolutions per sec.
or
.010 secs
means
10 msec.
The above is for a batch fire system.
To read 11.5 at 5,800 rpm means the injectors are static.
If you remember 10 msec at 6,000 rpm., doing the math gets easy. 20 msec at 3,000, or 100msec at 600 rpm, etc.

At 6,000 RPM you have 10 msec between injector firing.
You don't want to exceed a 90% under those condition. So at 6,000 RPM you can't exceed 9 msec injector on times.

At 3,000 RPM you have 20 msec, since the engine is operating at half speed compared to at 6,000 RPM so you have 18 msec available at 3,000 RPM

Cflick says:
You have just rather accurately described a 45% duty cycle at 3000 RPM. Now think carefully, and describe 90% at 6000.

Ron asks: What is the flaw in Grumpy's calc? Or is there no flaw?

I can see if there is one injector firing only it would need to cycle under 5 msec but there are two and they alternate per my "clock" example. What am I missing?

 

There is no flaw in Grumpy's reasoning for, as he stated, a batch-fire port injected system.
The visual aid RFMaster posted is REAL good for a TBI sync firing at 3 and 6K.
( thanks )
Async is simply both injectors firing together 80 times per second with no regard for where or what the engine is doing.

Remember, alternating injectors each firing once per reference pulse, means each injector fires TWICE per revolution, not once as in Grumpsters batch-fire description. At 50% duty cycle, one of the two is spraying fuel ALL of the time.
As soon as you go over 50% then both are on simultaneously for some part of their cycle.

 

Now I get it. Our TBI is NOT batch. Clear now. But I am certain I will have another question. Just give me a few minutes ! Thanks.

 

OK...This is the way I understand it, correct me if I am wrong.

In SYNCH firing strategy the injectors are fired by the DRP (distributor reference pulse) wich in my case(V8) is 8 pulses in a 360 degree rotation.
Each injector firing sequence uses every other DRP as the event timer wich means 4 pulses per rev. Dist turns 1/2 crank speed.
6000 RPM /2=3000/ RPM dist speed*8 pulses per dist-rev =24000 pulses/2=12000 pulses per injector/60sec=200 pulses-sec per injector/1000
msec =.2 pulse per msec* 5msec =1 pulse. (think that was longform)

In ASYNCH firing strategy BOTH injectors are fired simultaneously on a 12.5 msec interval independent of DRP, but were originally referenced by a DRP.
The way I see all this tying together for the topic is there is a significant difference between the two strategies as far as the amount of fuel the injector can output given a specific timeframe/pressure. If the injector has to open and close 4 times vs 1 the 1 will deliver more fuel.

SO....IMO.. duty cycle is irrelevant to injector rating unless the rating also list the duty cycle. 80% of 10 minutes is 8 minutes and I doubt an injector could withstand being on that long without overheating.
I believe the whole purpose of duty cycle is to cool the coil down so as to prolong longevity of operation. What the ideal on/off cooling cycle timeframe should be is probably dependent on injector design.

Having said that, I would love to know how my injectors are rated.
And technically TBI is a double batch fire if you will.

 

You pretty much have the idea on Sync/Asynch and the additional fuel flow t hat can be achieved in Async mode.

The ratings that I have seen on TBI injectors are at 12 psi and are flown static, on a flowbench.

PS- Here is what GM did on my 1992 TBI 350 ECM for High Load Asynch.

; SYNC/ASYNC RPM & MAP SWITCH QUAL'S
;---------------------------------------------
LD26E FCB 96 ; 45.8 Kpa, ASYNC to SYNC
LD26F FCB 48 ; 1200 RPM, ASYNC to SYNC
;
LD270 FCB 112 ; 51.7 Kpa, SYNC to ASYNC
LD271 FCB 52 ; 1300 RPM, SYNC to ASYNC

Above 51.7 KPA AND 1,300 RPM it would enter asynch, once it dropped below 45.8 KPA OR 1,200 RPM Async would be disabled.

 

There must be a flaw in my programming I've overlooked. My injectors are part#17084304 from a 93' 454 TB. If they are rated at 75#@12psi then they should be 101.5#@22psi (where I have it) wich makes them 12.78 grams sec.
I have most of my bins WOT upper rpm range @ 99% and if I use 12.78 as my constant it goes lean with a quickness. If I use 11.70 as my constant the AFR stays fairly close to commanded. I realize there is no way the engine's efficiency is 99% but irregardless it would need more fuel with raised efficiency anyways. The PW's are just too small if I use the larger constant...what gives?????

Coincidently if I use 68# as my starting amount with the added pressure it comes out to 11.60 wich is probably close enough to 11.70 to not notice a significant difference in AFR. Makes me wonder...68# is 90% of 75# and is probably close to the ragged edge of properly operating duty cycle.Maybe this is why I saw a 454 bin with the constant at 68#. Helps with the low rpm PW's.


Here's where my bin switches over, it's still where factory set it.

 

Same number on my injectors.
My best info is that they are rated 80.5# at 13 PSI.
I thought I once was told 65# but experience said more. ( I was measured 10 PSI )
Mine were going static somewhere around 3000. 25 PSI and now they're something like 65% on a WOT pass as high as that T400 will allow it to go.