I found this to be very interesting......some of you might have already seen it. Pay especially close attention to the comment from TPIS in the red on the right side.

I find it very enlightening that a tuned port specialist would say that 26# injectors can support 400+hp, and figuring a BSFC of .4 we could basically shift that HP output table down one notch to give us ~500chp with only 26.5# injectors. With a 85% duty cycle, and at 5000 RPM.

To me this sounds about dead nuts on, since that is exact about where I am running with injectors size. Based on a pressure of 43psi, and 24# inj. rated at 38psi. My shift point is 5200 with max power at 5150 RPM.

Guess this pretty much answers much of the controversy around my injectors, and how they car operate to those levels. Now take a slightly lower BSFC, and you can make even more power with the same small injector.

I think TPIS too thinks the same way I do. People over inject their cars and kill performance.

I would really like to hear what some of you others think about the statement TPIS is making. I would think that a reputable shop that tunes/builds/sells high end equipment/cars etc would know what they are talking about.

Many say its not possible etc. This seems to point the other way.
Interesting I must say.

 

Whooops forgot the img...

 

Let try this again. If I had my edit function it sure would make it easier.... Oh well chalk it up as increasing my post count..



ahh that is better...

 

Don't know why you keep hounding on about this. Your own data logged PW's shows that your injectors are static. Then you went and dyno'd while adding fuel. . . and guess what, no change in power unless the RPM was below the static point. This information is posted right here on TGO.

Now lets get to your calculations, from your immediate post:

Quote:

. . . and figuring a BSFC of .4 we could basically shift that HP output table down one notch to give us ~500chp with only 26.5# injectors. With a 85% duty cycle, and at 5000 RPM.

So lets do the math:

26.5 #/hr * 8 injectors = 212 #/hr

212#/hr * 85% = 180.2 #/hr

180.2 / .4 BSFC = 450.5 HP

Looks like 50 HP shy of dead nuts. And that isn't including the opening time where the injectors are not flowing any fuel. So even the possible 450.5 HP level is optimistic.

RBob.

 

Rrob,

I am just showing what other tuners/builders also think. Obviously they believe it to post it.

And your math while being right dead on, which I do not dispute, is what the problem is. The entire calculation comes down to BSFC. The lower that number is, the smaller the injector is that you can get away with.

Also your forgetting that EVERYTHING including my MPH, raceweight, and not to mention my DYNO results show that I am making well over 500 cHP. So the math that you did, while being mathmatically correct is far from being accurate. TPIS I think would also agree with this. And while I did post pulse widths etc, to satisfy the requests and yes they are saying I am static, there was still controversy with respect to the async modes etc. And I CAN show you dyno graphs of my last time at a dyno where I flooded my engine with fuel, 10.5-11.0 AFR through the entire RPM range. So the potential to add more fuel is there.

I am not trying to start a pissing match or cause any sorts of problems. I think we can all civily talk about this and listen to one anothers cases.

Back to the point. All the injector stuff I look at is WAY WAY overrated. With the exception of this most recent TPIS posting which also includes a statement along the lines of what I have been saying.

With that said, you have to admit the BSFC is a bit bogus in itself. What value do most use? .5 correct. Well these "standards" to pick from for your engine have been the same for years. .5 is typical of a "street motor" and ~.45 is typical of a "street/strip" setup. With that said. Do you think what the efficiencies of the motors since back in the late to mid 80's when most of this stuff was posted, is as accurate today? For instance if I have a 84 cross fire system stock "street" motor, do you think its efficiency is equal to that of a stock "street" 02 LS1? I do not think you would agree. So right there you are would be way oversizing your LS1s motor.

Many of our setups here are much better probably than the LS1 motor, yet we rate them using an outdated table pertaining to BSFC.

Do you see my point. Using your method I agree I should have 42# injectors to make 500chp. But obviously I do not need to. Bases on TPIS's chart, they say I could make nearly 700cHP! There is obviously a HUGE problem with these numbers. That is all I am trying to point out.

Most of the people here are running 30+ pound injectors which is way overkill.

I think there should be enough interest here that we could compile enough information to determine what the BSFC cutoffs are.

At the end of the day you have to admit that the motors of yesterday are far from the efficiencies of what many of us are running today.

 

There is more to the whole injector sizing business then you understand. Yes, the BSFC is a major portion of it. RPM is the other major portion of it. The higher the RPM a motor spins the less time the injectors have to spray fuel.

The old/original injector sizing charts are most likely conservative. Why? So someone going by that information will be less likely to go lean and end up with malformed pistons.

So lets visit the 42#/hr injectors. You say they are required for 500 HP ().

42#/hr * 8 = 336 #/hr

336#hr * 85% duty cycle = 285.6 #/hr

Now for various BSFC:

285.6 / .5 bsfc = 571.1 HP (a bit more then the 500 you came up with).

285.6 / .45 bsfc = 634.7 HP, hmmm

285.6 / .4 bsfc = 714 HP !!!!!


Of course the one variable being left out is RPM. If spinning an engine to 7,500 RPM the injectors need to be even larger. Why? Because there is less time for the injector to operate. How about someone that is spinning to 8,500 RPM, not unusual for a race engine. NASCAR engines go to > 9,000 RPM.

At 8,500 RPM there will be 7.06 msec between injectors firings (batch system). A saturated injector takes ca 1.6 -1.8 msec to open. At 85% duty cycle (of 7.06 msec) leaves 6 msec for injector operating time. Sub off the opening of 1.7 msec: 6 - 1.7 = 4.3 msec of spray time (I used an avg of 1.7 opening time. And I believe the opening time may actually be greater, 2 msec?).

Now, for how long is the injector spraying fuel over time?

4.3 msec / 7.06 msec = 61%

Now that 42 #/hr injector is only a: 42 * 61% = 25.62 #/hr

25.62#/hr @ .45 bsfc = 455.5 HP

Way down from the 634.7 HP when the injectors can be used for a longer time frame. Interesting. . .

Shall we talk about the fuel you are using? How much toluene are you dumping into the tank? IIRC you are buying it by the 55 gal drum. Did you know that toluene has a density 17.4% greater then gasoline?

That in itself will allow more fuel to flow through a given injector over a given period of time.

Maybe this winter you can find a dyno where they have air intake and fuel flow measurement equipment and find out what your engines true BSFC is. Air density and fuel density specs need to be included.

RBob.

 

Rrob,

I fully understand that as RPM goes up the time alloted to spray is reduced and that is a significant part of why I am able to get away with using the injectors I have. No one is disputing that fact.

conversely a too large of injector is only able to be trimmed back to a point where you loose adjustbility, pressure and atomization.

People seem to always forget that I have tons of room with adjustments upwards with fuel pressure. I am just barely tweaking the injectors up from their rated pressure of 38psi to 43psi. As TPIS chart clearly shows one 26.5# injector covers a WIDE hp range when pressure is increased. Which I have plenty of room to do if necessary.

This increase also will shorten the injector pulse widths.

These items are all factual and obvious. The point I am trying to make is the BSFC tables you base everything off of. How factual are they. IMHO they are WAY WAY off. You show how you can go from 450hp to 700hp with just changing that value from .5=>.4

A point I am trying to point out is that many of the people on with these calcs and charts are led to believe they need to buy 36# injectors. With a .4 BSFC =>288#/hr=>.85%=>612 HP yet they are lucky to have a little over 300 rwhp. So what they do to compensate the gross overfueling is cut FP back to 3Xpsi, and alter the bin grossly to get the car to idle and function properly. At the end of the tuning all they did was take an efficient motor and make it less efficient to match a BSFC of .5 or higher! The inefficiencies come from lack of atomization etc. Conversly, raising the pressure to reduce duty cycles etc, only help to make atomization with the fuel better. This atomized fuel then carries into the cylinder and mixes more efficiently with the air. Generating a more efficient overall motor.

As for the toluene jokes or comments save them. No-one here is doing anything as a personal attack towards you specifically or pointing any fingers. And we know what happened to the last person that took that road. So lets not go there.

The fact of the matter is where do you choose to start? This seems to be the key to getting an well balanced system. Is it like a carb, where you figure your going to need 850CFM so you downsize it to the next size CFM carb for best performance? Or do you over fuel it and then try to trim everything back to an acceptable level?

I just do not see the reason why people need 36# injectors even at .5 BSFC that can support 489chp when they are only making 300RWHP.

99% of the information put forth on the net and elsewhere are generated by the injectors companies which are in the business to sell injectors. Also I have yet to see an injectors fail from duty cycles over the 85% magic number. Corky probably has over 300+ passes on his car(with a pressure at times down below 38psi). I have easily over 150 at a min since the injectors were introduced. Not to mention countless highway miles on both motors.

Funstick pointed out a while ago also that the ECMs could be going into an async mode past a certain point which would then completely blow the lid off the sizing parameters.

There just seem to be many variable left unanswered to just dismiss it as 100% solved. It seems like with many components on a car, from the intakes to the heads to the cams to the gears to the RPM, that overkill is typically worse for performance, than undersized components. And as I pointed out with injectors you have plenty of wiggle room to move the injectors up to an acceptable limit. This seems MUCH more viable than going the opposite direction.

 

The problem I see is that you want to keep it factual and obvious while at the same time use twisted numbers & emotions.


What I showed was that you can go from 571.1 HP to 714 HP with a change in BSFC from .5 to .4. Facts are facts. If the engine runs with a BSFC of .43, then use that for inital injector sizing. I don't have a problem with that.


Again you are mixing apples & oranges, chp vs. RWHP. What is chp? And what if the guy is making that HP at 7,800 RPM? Check the size of Quad4 injectors. . .

The reason I brought up your fuel should be obvious as I stated the reason; it has a higher density then gasoline.

You came in here touting how great you were and running 26-28 #/hr injectors and saw no problems with it. You were rebuked. Each time you attempted to prove that the injectors were not static, the data you provided showed that they are indeed static.

If you feel that all the methods of injector sizing (except TPIS's) are bunk, then maybe TPIS's method is too. Are they taking RPM into account?

Facts are facts.

RBob.

 

Rrob,

OK. First off there is no emotion here what so ever. We are just talking civil about a topic that obviously interests us both, and perhaps others that are reading. Nothing more, nothing less.

I 100% argree that RPM directly effects the size of injectors you need to choose. No doubt. But bringing 9000+ RPM cars to the table is obserd. Anyone going over 6500 RPM, needs there heads examined or I have to take off my hat to them for spending MAJOR money on head components, in the order of $10k per head. But I have not seen anyone fitting that bill here.

With that said though. You can increase the fuel pressure to achieve less duty cycle to control that duty cycle. So a person that has a 350/219/190 AFR setup with 24# could do exactly what I did and build a shortblock 406+ and still use those 24# injectors. There is no need to go out and buy new injectors.

Anyone that does raise the pressure should upgrade their pump, especially if its the stock one with probably some miles on it. So upwards of 60 psi is nothing for a good pump. Mine is rated to 80psi with not a blink. If I raised my pressure to 60psi, well within the range of my fuel system I could make my 38psi rated 24# inj look like ~30#/hr injectors.

Now my whole entire reason for posting this topic is to point out there is are deficiencies in the formulas/BSFC....

Assuming a .5 BSFC for a motor nowdays, is insane.

For my motor with that assumption I would only be making:

25.53/hr x 2 x8=> 408cHP that is a wopping 100+ HP off from what I am currently running.

A point .43 gets us closer @ 474cHP. But still that is a far cry from the real power output. Simply put the formulas are not accurate. And in your benefit they were assumed at 100% DC.

A .36-.38 BSFC gets us probably in the arena, but that is still at 100% DC.

While you may think, hell is is making my exact point (that in itself is a moot point, I will admit its at a high DC, in the 90% range at the last dyno, but show me PROOF that injectors WILL fail over the magic 85% point. If I see I need more DC, all I have to do is raise my pressure), I am also making the exact point of the post.

Where does efficiency come from? The entire setup of your motor basically, but more specifically in the heads in where most of the power is developed/or is lost. A person sporting a SR/219/AFR 350 motor should have roughly the same efficiency of my motor. But if you use the .5 BSFC, you will have WAY WAY TOO much injector. That is the point of the posting.

I think there is a whole lot more to the story with the fueling, async etc than we now know. Coupled with the now days lower BSFC the motors are running at, the yesterday way of determining injector size is out the window.

 

That is a good point, I don't think that was out of line either .
Also the main reason you get away with such a small inj. is allowed time. You shift at 5300 leaving you with .01132 fire time,
where as I am shift at 6500 leaving me.00923 time to fire.
That leaves you 19% more time to fuel there for you can run an inj. that is 19% smaller. I run 30lbs you could run 24.7lb inj.
Assuming we make the same HP, But I think you may be about
20 hp higher than I .


Well I will be at PRP tomorrow to try and better my time,
Hope to see ya there.
Should be some nice weather.

 

87_TA,

As I said to Rrob, I do not dispute that RPM is a major factor for me being able to make the power I am with the injectors I have. But anyone running a SR is in the same boat. 5200-5300 is tops.

That is not the focus of my posting its the BSFC being way off. For your car, for my car, probably for Rrob, etc.

The toluene is not a big deal here its cut down 1 part toluene to 3 parts 93/94octane gas.

So the end octane is about 99-100 octane. Not a real show stopper. Depending on what part of the country you live in 100 octane is available at the pumps and considered "pump gas"

At the end of the day, you too could simply increase my injectors to 60psi and run them with a size of 30#s. When your car is tuned to that setting your DC will be not any be longer or shorter than your are now. THAT is fact.

I believe that would be better than running 30s backed down to 30 some PSI, where you start to loose atomization.

The higher the pressure, the more atomization you will get. I played around with building an atomizer at a powder factory years ago, and pressure was the key. Too low the spray was uneven, and fluid flow was inconsistant in quantity. This is the same concept when adding fuel. You want it to stay in suspension as much as possible and be quickly carried into the cylinder. You do not want it collecting on the manifold walls and running into the cylinders.

On a different note....was planning on going to Keystone tomorrow, but changed it when Corky wanted to run out in OH. Close to Dayton, for a few I think that might want to come and see first hand the cars run

I think its pretty safe to say one or both of us will click off a 10 run if traction and weather are there. Guess we will see.

 

Here is a recent thread where the gentleman posted his BSFC:

https://www.thirdgen.org/techbb2/sho...highlight=bsfc


Here is his basic setup:

400ci

Camshaft - Cam motion hydraulic roller

lift .596" intake with 239 degrees duration at .050"
lift .603" exhaust with 245 degrees duration at .050"
109 lobe separation angle

Brodix Track1 heads

And the dyno results:

Test: CB40608 - vic jr
Corrected Power
Range: 4100 RPM - 6000 RPM

EngSpd: 5050 RPM
STPTrq: 439 Clb-ft
STPPwr: 420.7 CHp
VolEff: 94.6 %
Fuel A: 94.9 lb/hr
Fuel B: 95.5 lb/hr
BSFC : 0.483 lb/hph
WtrOut: 160 degF

He also tested the this engine with a Performer RPM manifold. The BSFC was higher at .493

RBob.

 

My hand is up. I've built several motors that are shifted at 7,500 RPM. It isn't hard. Currently I am helping someone put EFI on one of these very engines.

This engine is currently running an ECM for timing control w/a carb. Biggest issue we are having is getting the fuel injectors sized & selected. I'd much rather go to PnH's but that brings additional costs and complexity.

RBob.

 

Some interesting reading on BSFC.
Not to lost in the read, is the fact that it varies with different fuels.

Since everyone is latched onto WOT, and BSFC I won't dare mention AE, and the effects of injector sizing on that.
Or the relationship of closed loop tuning, and injector sizing and BL's.
Or the fact that this is all in the archives.

http://www.prime-mover.org/Engines/GArticles/bsfc.html

http://www.aempower.com/faq.asp?sid=15

http://www.grapeaperacing.com/GrapeA...linjectors.cfm
http://www.grapeaperacing.com/GrapeA.../fuelspecs.cfm

http://personal.riverusers.com/~yawpower/cfsmeth.html

http://www.mrgasket.com/accelpdf/Injector.pdf

http://www.rceng.com/technical.htm#WORKSHEET

Goggling for MSDS, for gasoline, and then the chemicals that are used to formulate gasoline is also a nice read. Not to be confused with just reading up on Reed Pressure, lowend aromatics, fuel vapor pressures, etc..

 

I am very much enjoying the 'nice' banter in this thread. Great job guys!

Now for my personal experience ....

I run a much bigger injector than what I need. Why? Let me put it as simply as I can. Bigger injectors give me more room for growth so I won't have to invest in another set for awhile.

I ran my stock 22lb/hr injectors (LPE Blueprinted) on 3 setups.
- Large Tube Runner
- Semi-Siamesed Large Tube Runner
- Mini-Ram

With the MR I calculated 115% Duty Cycles when shifting at 6500rpms and running 52psi at the rail. I didn't want to take a chance on blowing up my motor so the small ~$200 for a set of SVO 24lb injectors seemed reasonable. My DC's dropped to ~93% when running 45psi. These were brand new and I wasn't happy with the 93% so I immediately sold them knowing that that I could get back almost all of my investment. I then purchased a set of SVO 30's (33lb according to GM standards). These immediately dropped my DC's down to ~78% (give or take - I don't remember). I was specifically striving for a low Duty Cycle to give me PLENTY of room for growth with minimal investment.

Real world experience at the track showed a significant gain when going from the 22# injectors to the 33# injectors. 13.0's to 12.5's ... with a best of 12.2.

IMHO - the main issue with ski's setup is that he is shifting so low in the RPM band. I shift at 6600rpms+. No high dollar motor either ... stock shortblock with AFR 190s and stock AFR springs (but I am running a good harmonic balancer). Do I need 30's (33# GM)? No - I don't. I am sure I could get away with 24lb GM injectors at 52psi. But now I have plenty of room for growth .... AND the peace of mind ... AND the ability to adjust without worrying about the injectors. I now can rule them out of the equation.

IMHO - I would rather run injectors that are too big than to run injectors that are borderline. The investment is so small that it is nice to rule the injectors out of the equation. Why take the chance and possibly ruin a motor ... and waste dyno time ... when you can spend a couple hundred on a bigger set of injectors? It's a cheap enough investment for A LOT of peace of mind. Also - bigger injectors allow for lower pressures at the rail. This is GOOD because it won't tax your fuel pump. Higher pressures are terrible for fuel pumps unless they were designed to operate at those pressures. Atomization is not a big deal for 2 reasons...
1) As long as you are above 40psi then there is plenty of spray.
2) It's a bank fire system anyhow. Fuel is GOING to puddle on the intake valve

My last dyno (364rwhp @ 6600rpms) gave me ~78% DC @ ~45psi. I'm real curious how my new setup (Lethal EFI Performance camsahft, CC 987s, etc) is going to modify this. I definitely should have a lower RPM for max horsepower along with significantly more power ... AND torque

Tim

 

I think part of the confusion is due to the way TPIS rates their injectors. In the chart they give they show the LB/HR that they tested at that pressure with a pulse width approximateing 85% dc at 5000 rpm. In other words the 26.55 lbs you are quoting has already been derated for duty cycle. It is also funny that if you calculate the rating as if the bosch injector was an FMS injector the results are quite surprising.

26.55 lbs/hr * sqrt(39 psi/30psi) /.85 dc = 35.6 lbs/hr

Kind of makes your wonder if they are selling the 36 lb FMS under a new part number.

Also figuring that

26.55 lbs/hr / .85dc = 31.24 lbs/hr

then plug that into the formula

31.24 lbs/hr / .5BSFC * .85 dc = 424.8 HP

Which is what they have in the chart.

It kind of looks like they are putting a different twist on the same old formula. This would allow them to get more for the same injector by derating it and claiming that a 36 lb injector would be to large and would cause problems with idle quality. And under there rating system it might since an injector that flows 36 lb/hr @ 30 psi and 85% DC is quite large.

John

 

I ' ve also seen TPIS info on injector sizing.......But lets bring another company to the table......G.M. In 1998(I think they had 28# injectors in the ls1's.(345hp) and to add also to g.m.'s thinking they went down to 26# in the later years.To spell it out
why would g.m. put 28#ers in a car rated at 345hp???I know it's not 3rd gen. but the math and/ or principles still apply.???

 

I think this topic is a very good one and taking a good course. Thanks everyone.

I do believe that you can use the route that we are using. Or like trax said, take the conservative one and derate them.

RPM is definately a major consideration. Along with BSFC.

There are tons of variables and the only way to really know what you can use is to pay attention to others setups and try to learn what they are doing and how they are doing it.

The problem is there are things like yesterday that happen to me at the track. Although the temps looked to be great for some good ETs. The DA was relatively high. ~2600'.

My first pass down yielded a new best 60' time 1.50sec with an ET of 11.2@120MPH. The entire way down the track I was at 11.7-11.9 AFR on my WB

Got back to the pits to check the Da meter to see what the heck was up. Corky reported that he too was PIG rich. So I determined that since I have made some mods like now running a full exhaust not to mention adding over a 100 pounds to the car with the exhaust and roll bar, harnesses etc. I figured for a quick fix, I would turn down my 43psi fuel pressure to 41psi. Unfortunately the regulator I have only backs down to 43, then the screw comes out of the POS thing. So all day I ran terribly rich . But still making the best of the situation. I managed two new bests.

One included a new best 60' time =>1.49sec
And a new best MPH in the 1/8 mile =>97.51MPH

I KNOW if I would have been able to turn the pressure down to 39-40psi, I would have been able to click off some more new best. Corky proved it when he took his pressure down to mid 30s. That means his injectors were well under 24#/hr, yet he hit a new best 60' time =>1.46sec and several other new bests. One which was 11.02sec@120MPH! None of these times were afforded to us by way of a better DA. Its just making extremely good power with what you have.

The 24# injectors are too much, I couldn't imagine 30+# injectors.

At the end of the day I think there are several ways to skin a cat. You have to know what your setup is going to be run at, know the amount of air your gonna be breathing and be sure to add enough fuel to make the power you have available with that airflow.

Without proper testing its unfair for me to say that going 30+# injectors and derating them is less effective. And likewise, it unfair for you saying to me that going small and raising the pressure is a poor choice.

This is why I always say you have to have a well balanced setup to run good. And know what its going to do. RPM, Airflow, fuel etc. This is also why I brought up the point that when trying to figure this out, before building an engine, it very difficult to determine using the current BSFC.

 

Ski, would you post the numbers off of the injectors you are using?

RBob.

 

I sure will. I will have to get the numbers off them tomorrow.

Here is a picture of the motor going together the last time. You can clearly see the "blue" tops.

Just got back from putting the street tires back on and flirting with the 509.

 

Here is some more food for thought. I captured a WOT run and have it here with some added columns showing the calc PW and DC. Anything over 85% DC shows up in RED. Keep in mind we shift at 5200 RPM. This is at the 43psi with vac line off.



If the picture doesn't come through real good, cut and paste the info into the address line to see it better.

PS will get those numbers at Lunch today if all goes as planned.

Later!

 

Ski, the math isn't working out fo rme. Mind sharing what you are using to find DC? I am more familiar with the

Duty cycle (%)_Batchfire-mode = RPM * PW / 600

 

My bad I should have named the calc PW => avail time. instead.

The column just to the left is the actual PW.

So DC=5150*9.99/600=>85.74% This is the first red one. Also take the % off the Duty Cylce column.

Sorry, it was before I had my coffee this morning

 

Still isn't working out for me...

I get:

 

My bad again mistake in the spreadsheet. I made it look worse than it actually is. The time available column is messed up...Correcting it now. Sorry.

Also the part numbers off my injectors are: F1TE D5A & another I could find is: 280 150 947 It was very tough to see in with them in the car. Hope these make sense.



Appologize for the mistake in the first entry. Was using the time available with actual, therefore the DC was off. As luck would have it, I checked it with one that freakishly worked out. lol

 

Here is what I have on the injector listed:
And from another source:

Bosch 0 280 150 947 255 cc/min (Light) blue - FORD Truck 7.5L V8(IC-080)
Bosch 0 280 150 967 356 cc/min Sapphire (dark) blue - 1994-95 Ford 3.0L V6 S/C(IC-084)(BLUE)

I included the 280 150 967 as it is a dark blue injector with a much higher flow and a part number that is one digit different.

RBob.

 

Rrob,

Thanks for cross referencing that information for me. As I suspected they are the 24#s....Here is a picture of them as we put together the motor...







The surprising thing to me is I have always heard that they were rated at 38psi, where here they are listed at 39.15psi, which means instead of the 25.5#/hr @43psi, they are really only about 25#, not that its a big difference.

On another note Corky told me last night that last year he was still runnimg the original injectors 22#ers! Now that even blew my mind

 

Actually - the calculation still works out to 25.5 lbs/hr. If you use the figures above the injectors are 24lb/hr @ 38psi. They just rated them at 24.35lb/hr at a higher pressure (39.15). Theoretically you could get 28lb/hr if you ran them at 52psi so you still have plenty of room for growth. If it were me - hehe - I would bump the pressure up to 48psi and then redo my BIN with a 27lb/hr injector constant. Why? This will allow you to globally lean it out a lot (since you are having problems with the AFPR screw) and will also give you better duty cycles when it gets really cold out and you need more fuel. What do you think?

Tim

 

Trax,

yeah I thought about that at the track and driving home. But ever since I put that regulator on the car, back when it was a 350 I did not like it.

When I redid the motor it was one of the items I regretted not upgrading. It works fine for regulating the fuel and keeping a constant pressure on the injectors, but its not the quality I would like to see.

I am going to be putting the single plane intake on the car after I return from the boundry waters of minnesota/Canada from my fishing trip all next week. It has a billet aeromotive regulator. If that one works nice I will most like, IFI go back to the SR get one of them. Also the Holley Regulator is a super nice unit. The entire top of it is a large **** that is simple to adjust. The guy that was there with us, racing on Saturday, had on. Said you can go all the way down to zero PSI with it.

That is something I will definately look at though if I go back to the SR. Thanks for the advice.

 

I haven't looked at all the previous posts in depth but I do believe it's possible for those injectors to be supporting that kind of hp.
If an injector goes static it will stick open and flow a LOT more fuel than at an 85% duty cycle. Going static and staying open all the time means the injectors never close or open in there small alocated window of time.
The biggest problem with this is tuning, you no longer have the ability to tune WOT AFRs once the injectors go static. As I've seen it the injectors actually take a noticable while before they become "unstuck."
Ski, when you let off at the end of the track do you bet backfiring through the exhaust that is more noticable than when you lift at a lower engine speed? The instantanious manifold vacuum might be able to kick those injectors back "on" but I haven't done any tests nore have I seen results either way.
In any case, going static is just a design flaw, yeah it'll work but once you here injectors going static (I have) you won't ever want to subject your engine to it ever again!
Just get bigger injectors like 30lbers at the very least. Then go turn better times

 

JPrevost,

The log I posted shows just slightly higher than 85% DUTY Cycles. So as I have stated I have complete control of my AFR. Actually I am pig rich, so the DC should come down even more with the adjustments I make.

Its funny, although I have not lost any ET or MPH, running an exhaust not has caused a much richer AFR than before. Which in my case with the injectors is a good thing.

But still it begs the questions of the injector sizing charts being accurate or not. The fact that we are able to make the power we are surely says that the tables are grossly off. I have been reading some articals to the subject, and it seems to me everything is way over rated. Which is not always a good thing. Some of the reading even states the obvious idle problems with larger injectors and slow throttle response as a result of having too much injector.

No my car doesn't backfire at all. The WB goes to 25:1 when I let off with the DFCO settings.

PS: I like the sang you have in you signiture. That is why I won't get the 30# injectors

 

What are you doing to go from this:

(reposted in thread: https://www.thirdgen.org/techbb2/sho...lable+AND+time)

To the data you posted in this thread?

Everytime you post about your injector PW & duty cycle something changes. Fuel type? Fuel pressure? PE AFR tweak?

RBob.

 

RRob,

I do believe that my stock fuel pump was getting weak and I was compensating to make up for its fading performance. Since the walbro pump, I have tweaked it at the dyno just slightly in the PE. Also down to ~43.5 PSI, where before I was at 45psi.

I have also noted another change since the pump install, the car doesn't seem to bog when launching at under 1/2 tank of gas. This weekend I let it get down under a 1/2 tank, and it still didn't bog when launching.

I had someone on the the vette forum tell me that fixed the bog problem they were having, but I did not believe it was pump related, nor have I really taken it down low and launched it. When you see the design of the tank and the position of the pump you can clearly see why there would be a pickup problem with low fuel and extremely hard launches and turns. The reserve light just came on when I was pulling into work after lunch, I would like to test it with some hard takouts this afternoon, but its tough to do a hard launch with the street tires on this thing, it just blows the tires off at any thought of laying on the gas.

So yes there were several items that I have tweaked since that posting back in early summer/late spring. The one that seems to have made the most effect was the walbro pump that is hot wired. The stocker while appearing to have been keeping up, must have been falling slightly behind.

As for the bog, guess the next time I hit the track, I will have to sacrafice a run to see if I can get away with a 1/4 tank. As I would love to loose some of that added weight I have to carry with a 1/2 tank