Okay, I am not an advocate of large injectors, or as large as the formulas say to run, but that is my opinion, as my Car runs very well with the injectors I have. But, if any of you guys are able to chime in, at the corvetteforum website, and see if you can help out with this ongoing debate.
We can all use education and experience has proven the best.
http://forums.corvetteforum.com/show...96&forum_id=48

 

Nobody wants to chime in, WOW.

 

Those guys are running low 10s at 132mph on 24lb SVO injectors? Every weekend for several years without a problem? sheesh.

Makes the 42lb SVO injectors I got seem like a waste of money.

 

i had 24# injectors on my 383 running mid 10's with no problem, but my inj duty cycle was maxed out at WOT, so i put 42# delpi units in and it still runs perfect

 

Running injectors static and controling fuel delievery with a AFPR is hardly the way to go.

 

Let one of them have a bad tuning day at the track and see who else wants to go with the injectors going static.
A 24# with the fuel pressure at 100PSI might come close cause I have made over 600+HP with 30# but the FP was 92PSI. It was on the dyno and had no other injectors and no time.Not the way for street or race duty.
There are a lot of cars out there making descent HP with IMO to small of an injector,but what will the make if they had the right size????

A 24#@45PSI will make 400FWHP@45PSI@ a 98.2% duty cycle.It will make 450FWHP@60PSI@ a 95.7 duty cycle all with a BSFC of.50.Those guys are good or a bunch of BS,or their car weighs 2500LBS
It is posible to double fire the injectors,but a bigger injector is a lot less brain damage and cheaper.

 

No kidding, its all because he can't get 30's to idle in a 400+ cid engine. He even says he can't.

 

"Tuning expert"???? I leave the computer tuning to the guys that do it.I just know what I want the engine to do and they know what buttons to push.
It gets an old fart by.

 

Lets get some support over there, come on guys, register and let them know WTF is going on with injectors.

 

I think its useless, let him continue on his way.. His response to everything will be.. my car is faster than yours so i'm right.

 

Use a BSFC of .4 rather than .5 and you have close to 500bhp. Jack the 3bar up to 50psi and sure, you can start making more power than is at first assumed.

My problem is that too many assumptions are being made. First BSFC makes a big difference in the calc. Ok so lets assume his information is legit, rather that argue the physics, it makes more since to find out **WHY** it is working for him.


--Maybe the BSFC is not .5?

--Maybe the FP is rising with RPM due to the fuel pump seening a higher voltage at higher rpms as compared idle FP. So his 44psi is really 50psi+ at speed. I've seen some weak alternators out there.

--Maybe the higher FP really helps atomization to the point BSFC is better

--Maybe his dyno is off and/or the vehicles is superlight




I have no problem with 100% DC because few people ever hold it very long and he is right in the fact that you seldom hear of someone burningup and injector. Personally, Id say the BSFC and FP being higher than is expected will be the key




Its kinda hard to get an injector to double-fire if it is already at 100%DC


Also it seems they don't recognize how offsets play into the tuning at idle with the larger injectors. It is true that the speed of the PCM/ECM plays a big part in the ability of larger injectors to be tuned at idle. The higher the rez the lower the commanded pulsewidth avaliable. The GEN7 might not have as much resolution as we have,I don't know.

-Craig

 

1-If much lower than 5 ya really got an effecient engine' that is not likely.
2-The only way ya get that big a jump in FP is to have a BIG pump and have it set that way to make that kind of HP to run 10's
3-If ya have no problem with going static,go ahead.Maybe ya don't understand the control issues involved.
4-Ya don't understand "double fire" that's 2 times a rev instead of once--more fuel.
5-I have run 116# on a blower car and had NO problem with idle ay 1800RPM's.

To run in the 10's ya got to make more than 450FWHP,a lot more and to do it with 24lb injectors is only posible with at least 100PSI of fuel pressure---BIG PUMP___
He may have a 2500# car also.Tube chassis? Not likely.

 

Well guys I am not taking any sides but my car has stock 24# injectors and weighs 3,500lbs. I have run 11.24@120.8mph with stock 3.42 gears in the 10bolt. I could have gotten into the 10's with some 4.10 gears and a transbrake. I have run 10.17@134mph with a 200shot and my fuel system consists of the stock intank pump along with a NOS booster pump. I know I could use some 30#'s but the car runs great and it hasn't been on the dyno. JMO experiences. later Clint

 

But do you know? He is running a nice setup. I'd doubt he is much lower myself but you won't see me saying he isn't with any confidence

How many guys do you know with stock injectors on a Head/cam lt1 that put down 400rwhp? Obviously your 400FWHP is a poor assumption. Just look above at Jay_Lt4s statement "i had 24# injectors on my 383 running mid 10's with no problem,"

It really is hard to argue with facts, if they are doing it, it is foolish to say they can't. Obviously, your understanding isn't matching the emperical evidence



You might reconsider your understanding. Follow the facts. If it was fat in the first place anhe is able to do the 10s after leaning it up the injector isn't static. Simply, the only tuning with an EFI without active FP control is injector PW. If you can open it longer and make it richer, you aren't at 100%DC.


No you don't undertand. The otto 4stroke cycle allows for 2 revs(4 stokes) per cycle, so the 4stoke DC takes that into account. Using the normal example. If the injector is at 100%DC and the rpm is 6000, you have a PW of 20ms. That means the injector is open for not 1 but 2 revs. If it is already open constantly, how can you open twice? It never closes.

here is the math for you: 2revs/(6000rpms/60)=20ms




First off, 116# injectors is pretty much uncalled for for most any car.

And your point? Now did you use a stock computer? Was the smell of unburned gas noticable at idle? Take note of what many of use have noticed. The min PW amount of opening of an injector is constant, regardless of size. Running injectors twice as large as needed will always spray twice the amount of fuel. The higher the idle the less of an issue. So now make that 116# inj idle at 800 or 1000rpms rather than almost 2K and tell me you share the same opinion. Simply the smallest inj you can get by with will ultimately give the PCM the greatest control of fuel delivery.


Did you happen to look over the guys configuration. It is not close to stock. So you might wanna assume he is running a decent pump. Anyways a long time back I ran a 5176 kit and the booster pump had not problem pushing 100#. Most FMU apps on vortechs and prochargers push that level too with 24s. It is not an issue as long as the fuel volume stays within certain levels.

Not to be an **** but comments like your double firing of an injector explaination while also talking about the injector being static, isn't helping your argument any.

 

PS, the answer to #5. Remember we are talking min PW and the same PCM.
Let me restate this:
...

The min PW/amount of opening of an injector is constant because of the resolution of the PCMs internal timer, this regardless of size of the injector. Running injectors twice as large will always spray twice the amount of fuel at this minimum PW. The higher the idle the less of an issue because the lower PWs will not be necessary. So now make that 116# inj idle at 800 or 1000rpms rather than almost 2K and tell me you share the same opinion. It will do it but the sniffer around will notice the emissions are not clean. Simply the smallest inj you can get by with will ultimately give the PCM the greatest control of fuel delivery