http://kinsler.com/Cat_31_Web_HTMLs/020 ... een62.html

Read this page including the "to clear up a bit of confusion." section.

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

Sam

Yea thats not the idea fuel line/rail layout. But it will atleast hold pressure to the injectors because it is run right for what they call a dead head system. It would be better to put the reg after the fuel rail & the return line still coming off the reg. It really does make a big diff in how much a system will support ( Hp per flow) as the Turbo V8 guys or any other high HP setup have found out. One other good point about it is all debree that inters the fuel rail has only one place to go & that is in the injectors. To where if hooked up with the return coming of the end of it the debree has a chance of making it back to the tank & getting caught by the filter the next go around. Injectors stop up very easy with a system like you have, Just ask any Dodge V8 Truck owner that has a 1998 up model truck ( not 100% sure on the year they started the no return from rail system for the Dodge) I have replaced complete injectors on these trucks a whole lot because of this problem. And if they start building the trucks the system has to be changed to support any HP.


Some of the Mustangs have a fuel system ( OEM factory) like you have described on your car. One of the first things they have to do when they start making HP is changing this to a return after the rail system. No matter how much pump or injector you have this type of system can not keep up with demands. It is real bad for getting air in the rail & pressure waves that cause problems with some of the injectors not being feed evenly, on top of not being able to flow good.


Fuel pressure should be 45 with Vacume line disconnected. Now this is a good safe level, you can run less than this as long as your reg will still give you the high pressure you need when under boost. When you hook the Vacume line back on it should drop between 5 & 10 psi. The most important part is to not be under 40 psi (with Vacume line off) and that it adds One PSI of pressure for each PSI of boost. But to be safe 45 is what I run & recommend ( unless you have injectors big enough to compensate). If you had 60lb injectors (bigger than needed) it is not unheard of for tuners to bring base pressure down to a low number, mainly to help with idle quality when using bigger injectors on factory ECM's.

I am using a few different pieces of software to get the injector size needed. At 300hp it calls for 32's. At 350hp it calls for 38's. At 400hp it calls for 44's (minimum on these figures). This is calculated at 45psi base fuel pressure(vacume line off & no boost). You also have to figure that under power you are not running normal A/F mixtures, which add to the demand of needed fuel. These figures are based on 13:1 A/F mixture & under boost you should be somewhere around 11.5:1 A/F. Also the BSFC of the engine will come into play on injector size. The more effeicant the engine, the lower you can get by with on size injectors. The /6 is not very effiecant! Some software ( Like the one from RC injectors) even call for bigger injectors than what I have listed.

But as a general rule & a little safety built in ( very little) this is what I run.

Base pressure = 45psi - Vacume line OFF

UnderBoost = The Above (45psi) , plus One Pound of Fuel pressure for each pound of Boost added. ( must be read when under power - gauge at windshield, or somewhere readable) Be sure the vacume line that is used is capable of supplying a Boost signal when the throttle is open ( Like form the manifold)

Fuel pressure with Vacume line hooked up = Not that important as long as it drops 5 to 10 psi from Base (Base =45psi). ( can drop even farther as long as it doent cause tuning problems when cruising & exceleration, and you still have the base pressure that is needed) This is this way so that when you thottle it acts like a accelarator pump in a carb, it incresses what the injectors are putting out automatically from this.



If you have to spend to get a fuel gauge that you can read under power I would buy one of the pressure transduecers that are available so you could hook it to your DFI system. Then you would be able to log it. Works just like a Electric Oil pressure gauge only for higher pressure. You should have a analog input available on your DFI system that would read this. Then you wouldnt have to have a gauge on the hood or inside the car.

Injector size, IMHO, I Would Not, run anything less than a 44lb injector in your setup if it was mine. I would prefer to have 60lb if I was running this setup. And even that would only be exceptable if the fuel system is up to par. The Buick GN guys run 50lbs injectors for turning up the boost with the Stock Turbo. The Supra guys have 44lb injectors stock from the factory, they run out of fuel very quick if they start pushing things & need to upgrade. Real world demands often dont fall within the guide lines of calculated threories.


Jess

That was all very interesting, and alot to think about. I think I need to get the regulator/fuel rail configuration straightened out first, and then think about bigger injectors. I understand your logic Jess, concerning the debris issue on the dead-head style system. That alone is compelling reason to change.
Sam

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Mr. Powell,

Sorry if you have posted this and I missed it... Does your system batch-fire the injectors or fire each one individually?

-Mac

I understand why the dead end system might be less than optimal however I dont believe thats the reason for your difficulties tuning. There is no reason on a 300hp street slant it wont work. I also think 60Lb injectors is ridiculous. I run a 350cid 320hp towing vehicle with 130lbs per hour total .....there is no way your slant needs 360lbs per hour total.

I would check the duty cycle on your 30lb units as Lou suggested . I bet an afternoon with Smokey Yunick they are just fine.

Keep in mind a 225 slant is the same size per cylinder as a 5.0 Ford. They use as small as a 18lbs

A GM LT4 engine uses 36lb injectors.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Thanks for your voice of reason, Sandy. I agree on the fuel routing and the injector sizing.

Sam, your car may make 300 crank HP when everything is tuned up, but 30lbs should be just fine for that. When I have driven it, it felt more like 250-270HP. I have 2X85lbs = 170lbs/hr total on my 64 Dart, and the injectors are at around 80% duty cycle at 6000rpm and around 270HP. If you have 30lbs/hr then that is 180lbs/hr total, even running at 44psi.

I could certainly see if you had 24lbs/hr injectors and specced 30 in the software that it would take some really high values in the VE table to get it to run right.

The Best thing to do here is datalog injector duty cycle.

Lou

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Home of Slant6-powered fun machines since 1988

Dart270 - is your car forced induction? If not, your injector sizing will be different than Sam's. The turbo in effect makes Sam's motor act like a bigger motor(this may be obvious to you, so sorry if it is). The only way to truly tell, as has been mentioned, is to watch the duty cycle under boost/load and see if it is running out of fuel.

just my .02, not trying to rebuke anyone for the sake of meanness .

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69 valiant

Summit's catalogue chart for fuel injector size does indicate a larger size required for forced induction. This would suggest that NA road race engines may need less fuel than FI engines producing the same HP. Very interesting.
In any event, my fuel system seems to be not doing the job needed at this point.
Thanks for all your input. I hope this is helping others think about their projects in some useful way. We are headed into the coldest week of weather in five years here, so car mojo is mostly directed at this forum.
Sam

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Tom, My fuel pressure regulator looks essentially like the Kinsler 10745 listed on the next page. Do you have any idea how I can hook this up on the outlet side of the fuel rail? The fitting to the left in the Kinsler catalogue photo would be my high pressure pump input, the one on the right would be the output to the fuel rail, and the one on the bottom would be my return line. What I am not clear on is if both the input from pump and output to rail maintain the same adjusted pressure. Obviously what is excess is allowed to bleed off to the bottom and return to the tank. If both input from pump, and output to rail maintain the dialed in pressure than I can put my pressure gauge in one of these taps on the regulator, and put it all on the outlet side of the fuel rail. What light can you shed on this. Thanks in advance from anybody who knows.
Sam

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The Holley Stealth Ram comes with a 1000cfm throttle body supports 450 HP and comes with 30lb injectors.

HP is HP whether from forced induction or not. A MAF sensor reads the same for either.

Is Sams car making more than 450HP? Is it suckin up more than 1000cfm?

If the injectors are too big your driveability goes down the tube.

If this car could be fueled with a 750 Holley carb ....then 30lb injectors will work.

Ford Racing uses 30lb injectors on 460cid motors....60 lb would be excellent for 500 to 600 hp

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I agree that boosted motors make more than non-boosted for a given HP - this is known. BSFC, brake specific fuel consumption, is the term, and is higher for a turbo than NA. Even so, 8spi of boost on a mild Slant should not cause fuel starvation, I believe.

Datalogging will set you free...

Lou

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Home of Slant6-powered fun machines since 1988

I am sorry but Hp is not HP between N/A & Turbo engine. The Turbo engine requires more fuel per HP than any other setup (that you would run on the street) out there . This is why the BSFC comes into play on your figures for size & the A/F choisen for the engine will effect BSFC.



For example a 300hp 6cyl N/A reguires 28.62lbs injector. This engine has a BSFC of .045 ( you will see this number on Dyno sheets)

A Turbo motor of the same HP(300) with same 6cyl will have a BSFC of around 0.65. These engines calc out to needing a 41.34lb injector just at 300hp, in the RC Injectors software on there website for injector sizing.


A 44lb injector would get the job done for Sam ( and I say that with caution). But If I where buying new I would get 60's. Just incase he finds the rest of that HP that would come with more boost & a proper setup. This turbo is good for a little over 400hp if you push it. AT 400hp the RC site comes up with a 55.13lb injector needed. I guess this is why the Buick GN guys that have run the stock turbo into the low 11's with a 3700 car are running the 60lb injectors.

I am not trying to dissagree with anyone but I have ran this stuff for years in many different type cars & setups. And you dont want anything smaller than a 44lb injectors for a setup like Sam's, and that would be if you dont plan to turn the boost up. Right now I would suspect Sam's car is only putting out around 230 to 245HP, & partly because of the setup. When he should be putting down more, like something over 300hp with ease.


RC injectors is a very high quality injector sold in the import area. Here is the link to there calc run the numbers , and be sure to read the footnotes on BSFC. BSFC will go even higher on a engine that is not effiecant. Be sure and use what ever Base pressure you run ( like the 45psi wihtout the vacune line)

http://www.rceng.com/technical.htm#WORKSHEET
I have other software that I use, but this is a good one here.

Jess

OK, it is really getting interesting now, and I am really feeling old as well. . Rance states on the receipt, which I located, that the injectors are 36#, and the part number on the receipt agrees with DFI's web site that these are supposed to be 36# injectors. I remembered for "sure" that these injectors were 30#. My grandad used to say that "it is not what you don;t know that will hurt you, but what you know for sure". To there you go. OOPS! While Rance was not a good support resource for communication style reasons, I do trust his judgment on injector size. He himself has a small displacement turbo charged DFI controlled engine in his car.

The injectors have the number 9267 printed on the side. They came in Accel boxes which were thrown out long ago. Does anyone know if this number is indeed for 36#? The fuel regulator is Paxton part number 8F002-004. It looks just like the part pictured in the catalogue on the web site Tom linked us to, which I referenced in my previous post. I wonder where I could find manufacturer's information on how this thing is configured?

I suspect these injectors were actually made by Holly, or perhaps Bosch. Anybody have a parts number reference for injectors from either of those companies? I will go looking on the web myself.

It seems obvious that the fuel delivery is messed up here. Regulator set up, and/or perhaps something as dumb as a bad gauge could be possible culprits.
Sam

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I'm kinda bit confused with the injector sizing as well.

On megasquirt there is a calculator and it suggested about 24-27 lb for a 2.5L 4 cyl 16 valve engine of estimated 150-160HP. Also I estimated the injectors with "turbo intake but no turbo" for stock mopar 2.2 with SLIGHT bump in HP to appox 100-110 and it still is over 20lb. What about the injectors from the 3.3L V6 which is rated 19lb for this 2.2?

Cheers, Wizard

Wizard brings up an interesting point.

The Megamanual injector sizing section: http://www.megamanual.com/v22manual/minj.htm#size

sez: a 300HP turbo car with 6 injectors would need 32 lb injectors

.....~

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Yeah....Im the one who destroyed this rare, vintage automobile.....