I have a question to all the tuners here on injectors sizing. Seems like everytime we turn around a new theory hits the table on sizing of injectors.

Obviously we want to remain in control of the pulse widths so we are talking sub-static conditions.

All the big names here...what are your thoughts on a lingenfelter built, 420 CI motor, trapping at 132 MPH, miniram intake ~6500 shifts, ETs in the 10.02 range, pulling 1.30 60' times. This motor is easily putting out over 450 rwhp.

I would like to hear what you guys think the size injectors should be on this motor? In addition, please indicate the pressure setting you feel they should be at. Since obviously we can put smaller ones on and raise the pressure up or down to compensate. Lets stay within -/+ 5 psi from normal injector rating of 43psi, realize some are 39psi...

So lets here it.

 

I think this is better suited to the TPI Board. I'd be happy to answer it over there.

 

from all my experience dyno and track tuning I would suggest 34-36lb injectors set at 43-45 psi. I don't use formulas to determine injector sizing. I have linked up to enough cars to tell what an engine needs. But this is how I tune. Others may use different methods......

 

wrong no cigar

 

Don't ask for my opinion ,then tell me I'm wrong. I didn't tell you that you was wrong for thinking high fuel pressure was ok,"because the fords do it". Or tell you about 22lb injectors in a 406. I'm just saying it seems a little rude. I guess I'll just stay out of your threads if you don't like me. Don't undersand what happened, dont care. I will stay away from conflicts, like the one you are starting.

 

So, what are you using? I don't know the equation off the top of my head and have no way to make an educated guess.

 

ok to be more polically correct towards 11sorbust you are not right on your awnswear on this particular setup are you happy now i am sorry for offending you is that better

 

and another thing what is wrong with 22lb injectors in a 406 or high fuel pressure

 

You are just trying to hook some people. Why ask opinions just to "correct" people. You said no cigar, right!? Then you must know the answer. So why post this thread to get others opinions? You "seem" to know the answer so I will consider this thread nothing more that a hook with bait on it. Don't ask people for opinions when you are already know the answer, and want to tell others "no cigar". That just causes problems.I don't want problems at TGO, you shouldn't either. BTW, your apology was far from sincere.

 

11s your right there was a HUGE bait line out there, and it was suppose to be meant to be worded that way on purpose. I know all the naysayers would have not touched my post here in a million years.

Here is the deal. 420 CI lingenfelter motor, Miniram, trapping at 132MPH, 1.30 60' times running a current 30# injector.

The guy asked for my help tuning the car. Went down the other weekend and other items kept me from getting into the tune beyond telling him items to fix.

This weekend his Diacom would connect etc. Tuned his car with it starting off sooooooo pig rich is was sick. All the Duty cylces were in line etc. For quick changes to dial it in we kept lowering h is fuel pressure to biring in the narrow band o2 readings. Started out high 900s at ~50psi, black smoke out the rear of the car etc. Had to back it all the way down to 40psi so in actuality he was only running ~28-29# injectors. With every reduction he dropped both ET and gained MPH.

Dave was astonished. Few things I would like to point out here. Here is a motor that is running more power than anyone else here on this board naturally aspirated. 132+ MPH trap speeds, 1.30 60 ft times, 6500 RPM shifts and it only needs 28-29# injectors.

Why would anyone in their right mind think they need 36# injectors on a 350 motor?

This I'm sure will be a post that is regarded here as starting trouble etc. But in reality, it should be a HUGE eye opener to many that what they preach is far from real world results.

Furthermore I told Dave upon leaving tehe track that say he would be MUCH better off, with 24# ers at say 47psi for better atomizaton. Also it would cure his extemely overrich idle he doesn't like.

Here is a picture of his vette off the line. Nope no power there!

 

I really don't think baiting people is cool. I have tuned many ecms. I know what it takes to get results. If I touch the car it'll get better track times and driveability. There is two schools of thought on injector size regardless of the method. I have had 19lb injectors and 30lb injectors. So trust me I know which one is better. But I'm not going to get baited into a dead end debate. Cause my car ran great with the injectors I ended up keeping. I could explain why I use the size i have. But I dont need someone telling me "no cigar". Old Tim would have told him to take that cigar and... BUT I am not into arguments anymore. Ski, if you really want to know why I use certain injector sizes then please PM me. No bait and switch here

 

Yea, I can see that. Hell, the 24lb SVO's that I run can EASILY flood my motor (it still runs eye-watering rich at idle even at 39 PSI).

 

Using only the formulas and endless wisdom I've collected from this forum I'm going to have to say that 24 lb/hr injectors, a stock 48mm throttle body, and a stock MAF should be more than enough.

Now for my own opinion:
Given the above intake restrictions (which may not be true), at 4000 RPM and up it should drop pressure in the intake so badly that very little fuel would be needed. Of course when pressure drops in the intake at WOT the injectors will flow more as if you'd raised the fuel pressure since they are no longer firing into atmospheric pressure.
I'd also wonder if the intake port volume is in the 240 to 250cc range as well, because if it's not at least close to that range then that will account for even more pressure drop right around the injector.

If it's running with any backpressure plus some significant overlap on the camshaft that will further reduce the engine's need for fuel due to charge dilution. A quick look at the cam-card and a pressure probe in the exhaust could answer those questions. Big inch engines tend to need a pretty healthy exhaust system to avoid backpressure.

I'm just stating some more opinion to keep it technical, but not looking for any cigar from the 11.0 crew. Thanks anyway.

 

Just my opinion, but first I'd look at any given injector you were considering running, then check into an ideal pressure that gives ideal atomization.

Could be 46psi or 50psi, who knows until tested.

Once proper pressure is realized, flow the injector at that pressure and do the math for your engine taking into account the duty cycle at WOT you're trying to achieve, then tune accordingly.

My guess would be guys like Rich at Cruzin Performance, or others who flow injectors, have a pretty good idea of what an ideal pressure is for any given injectors.

 

So let me get this straight. Running big injectors is wrong, because there are a few fast cars that run small ones?

What about fast cars that run big injectors? Are you saying they would go faster with small injectors? Or that there aren't any fast cars running big injectors? Or?

Rather than bait arguments, why not just share information. You've found that 30lb injectors can support 132mph in a car of unspecified weight. Impressive? Sure. Enough to base a rule of thumb on, not by a longshot.

Don't forget, even if they are 'enough' to support the power, maybe they don't have the DC margin that some people desire. Which brings me back to the questions of paragraph 2.

 

Here is my 2cents:
22lb injectors on a stock TPI.
GM put 24lb inj on a stock LT1 for a reason.
Put 26lb on a LS1 ,
then in 2001 upgraded to 28 LB injectors.

Though you can run with less injector - Go ahead.
I like my 30's and they like me, Fuel pressure is stock to.
Duty cycles are in check as well. 80% @ 6000. Sure I could go with a little less, but why?
:lala:

 

ROFMLMAO....GM is obviously WRONG. Someone better put a call into central engineering post haste

 

 

Almost fell out of damn chair with that comment!!!:hail:

 

Guys I think your missing the entire point here. Isn't it to help other out and save people money? That is the reason for pointing out the power that can be made so those people with small 22 pound injectors can made big power without having to spend money on larger injectors.

200 dollars 87_TA might not be much to you, but to some people it is. And had you stuck with the stock units, you might not be puffing black soot out your pipes on launches, and be a little happier than you already are.

Nuff said, off to work on details of a 500+ rwhp motor with 24# injectors.

 

FYI, My 406 NEVER smoked with the 30lbers. I think 87_ta's car smokes a bit because of the 6 inch rods....

 

Yep, off we go...

 

Nay, ski and I are old MAF buddies. I'm not debating anything or trying to push my views....

 

Inwo was saying good-bye.

 

Running small injectors at high pressures wreak havock on fuel pumps, unless you have a killer one. If I was using a stock computer i would stay on the small side. but DFI i would go large. Tuning a stock ecm with a large injector is tedious to get the drivability right.

Just my $.02

 

Hold your guns Ski,
I was not throwing jokes - sorry it was taken that way.
$200 IS A HECK OF ALOT TO ME! Believe me.
But if you are building a 9 second 9000 RWTQ machine that you are talking about it would be cheap insurance.
I don't mind my smoke, Better than a head gasket.:lala:

 

Looking at some very basic parameters here, a 406 cid engine has 16% more volume than a 350 cid engine. In a direct proportion 22 lb/hr injectors plus 16% would be a
25.52 lb/hr injector.

If the volumetric efficiency (VE) or the RPM range of the 406 is also increased beyond the 350 cid engine, then I'd have to say a little more fuel flow should be tacked on to that to keep things in-line with the factory proportions.

I think it's safe to say that most people building a hot 406 will easily exceed the VE and RPM range of a stock 350 TPI engine.
I also know that you can get away with running a small injector, just as you can get away with running a small TB, carburetor, or exhaust.

I think it should be obvious that everyone will not choose to do it the same way due to personal differences and monetary restraints. I do believe it's a good thing that people do post up what they've done and what you CAN get away with, because that only increases options for all the readers.

 

I also know of 350 engines that cannot run on 24# SVO injectors @ 50 psi. You just cannot over generalize. If you are going to error, error on the side of too much injector and tone it down.

If you error on the side of too small of an injector, you may find yourself buying another set or worst.

I suspect the fact that SDI used a solid cam has a lot to do with the better BSFCs which are a factor in computing injector sizes. Very few people run a solid cam, but if a person were to take a small solid roller cam of roughly the same duration & lift @ .050, you'd find a lot of interesting differences between the two. Differences in efficiency (BFSC) being just one of them.

We need more guys to dump their hydraulic roller cams and go solid roller and then I think a lot of interesting differences will become apparent.

 

Not to mention that BSFC is based on pounds of fuel. When you increase the density of the fuel with additives, you increase the weight of the fuel. Increase the density 10% and the BSFC, can change 10%. Not to mention the energy content of what your burning, er, adding. For a comparison of BSFC's means using a given fuel type, other then that and your playing apples to oranges.

I've adjusted too many valves to think of going back.......

 

That's true. In the past whenever I've added octane in the form of race gas I always had to lean the mix down to get things right again.
Some people just add spark advance but I think leaner with less advance gives more power.

 

I know in my last log after switching to 7749 and FMS 42 lb'ers I was getting into the upper 90's injector duty cycle short shifting around 6200 and that is with 47 lb's base fuel pressure. I don't have a FP guage on full time but that seems too close for comfort to me. I am running the stock in tank pump with the procharger boost pump.

 

I was wondering why SDI or the cigar guy wasn't replying.


So this is my thoughts on injector size. You have certain things to consider. The most important thing is projected HP. That means you'll need to look at the HP range you engine will see now and in the future. I bought 30lb injectors for my 406. I had tpi and the duty cycles was kind of low. But I knew the engine was getting a high flow intake and large cam,someday. I am putting the same 406 back together with a HSR and fat cam.I'm sure my duty cycles will be in check. AND I didn't need to get different injectors.

Small injectors and high f/p will work. But at the cost of fuel pump (over time). Injectors are rated @ X psi. If you raise the pressure the factory injector rating means nothing. Different types of the same XXlb injectors will flow different lbs/hour at higher fuel pressure. So 22lb accels and 22lb bosh injectors @ 45psi could flow different lb/hour. Injectors are rated @ XXpsi so I suggest running the injectors at their rated fuel pressure. Otherwise it's up in the air what size the injectors are with raised f/p,generally.

The injectors have a kind of operating range . From idle to WOT @ redline. Raised fuel pressure and small injectors might get your wot duty cycles in check. But you could have idle fueling issues. The right sized injectors will be able to control idle and wot much better than the other.

 

I'll log data before and after I switch to solid lifters. So you are saying the duty cycles will drop some?

 

Don't forget where that HP is made in the RPM range.
I'm with you though. Given a choice I'd go bigger than necessary on injector size, but I'd still run then engine to the lean limit with tuning.

I'm not sure what Glenn is getting at because he didn't elaborate very much on that idea with the solids.

 

Glenn,

I find this statement quite interesting, but I have never heard anything about these differences between solid and hydraulic roller cams relative to BSFC. Is there any way I could get you to elaborate a bit? If its too far off topic, a PM would work OK too.
Thanks!

 

Guys,

Please rate your injectors according to GM standards. My guess is that those are not 30lb injectors in the vette. They are the same ones that I am running. That means that they are 30lb according to Ford standards. But, when rating them to 43psi we are talking about a 33lb injector. I am running that red-top SVO injector in my car and use a 33lb injector constant. I made my 11.6@117mph pass on those injectors and it gave me 82% Duty Cycles. Plenty of room for growth. These injectors will easily support 10's. Furthermore, I can see running this injector at higher pressures and getting low 10's out of it. Remember - everyone rate their injectors the same way so that we can all speak about injectors on the same level playing field. A 24lb SVO injector is NOT a 24lb GM Injectors. A 30lb SVO injector is 10% bigger than a comparable GM injector.

Tim

 

Great point Tim, I do not think many people knew that

 

Starting at about 3,000 RPM all the port type injectors I've run at near 95% DC start going erratic. You can actually hear them chatter. This is on the ecm bench.

 

Same on the street.


RPM is the x factor, like 305sbc said. Look at the olds quad4...