high/low impedence injectors

[68ls1]

Gents, can someone explain to me the difference between high and low impedence injectors. When is one type prefered over the other. As an example, what size/type injector would be sufficient and then some for 500 N/A hp LS1?

Thanks in advanve, Noel.

[chicane67]

The primary advantage of low impedance injectors is a shorter triggering time. When large injectors are fitted to high output engines, low impedance injectors will often give a better idle quality because of this fact. The primary advantage of high impedance injectors is the fact that less heat is generated in the drive circuit and often no external resistors are used.


Injector impedance describes the electrical resistance of the solenoid windings. These are usually grouped in two categories:

Low- 1.7 to 3.0 ohms
High- 10 to 16 ohms


There are essentially 3 different types of nozzles:
Pintle, disk and ball.

And here is a good injector size calculator:

http://www.z31.com/software/injector.pl

[68ls1]

Thanks Chicane,
Thanks for the reply, good answer and really good link. One more question. Given my horsepower goals, and say and additional 150hp for future mods a 42# injector would work out. Question is on something that will be driven around town alot and raced everynow and again, would a guy want low or high impedence. Is 42# considered a large injector. Would I want to keep to whatever type the factory runs on an 02' LS1 (what type are they BTW?) Thanks again for the help.

Noel.

[Cdog]

What kind of fuel injection do you have? High impedence are well within your HP range. In the holley system you have to go to low impedence after 55lb. injectors. The good news is the high impedence set up is cheaper and readly avaliable. In fact I have a set of 44lb. injectors with about 20 hrs. on them. They are within you HP range. Injectors can be boosted a little with fuel pressure or turned down the same way. They are like brand new, in fact I can show you the recept and build date. There is a formula you must know to figure your injector size. I am putting a procharger on my 540 that these are comming off of and have to step up to 60lb injectors. Let me know if your intrested. I can give you the # to the engine builder, he's a cool guy who will talk you thru it and help you with the set up.

[68ls1]

Cdog, I'm leaving work today, should be home in a couple of days and will consider you offer. What kind of price did you have in mind and will they fit into the ls6 intake on my LS1. I have a factory LS1 PCM, nothing fancy at all, but I am sending it of for reflashing to make it work in the 68, I'm sure my guy can make the necessary adjustments to accomodate the bigger injectors. The 'system' is FAST fuel rails, Aeromotive A1000 pump with electronic controler, 10 and 100 micron filter and Aeromotive regulator. The lines will be -8AN to the rails and -6AN return.

Thanks, Noel

[Blown353]

I am putting a procharger on my 540 that these are comming off of and have to step up to 60lb injectors. Let me know if your intrested. I can give you the # to the engine builder, he's a cool guy who will talk you thru it and help you with the set up.

You may want to rethink that number. I'm running 55# injectors on my "little" Procharged 353, and they are going static at only 5500 rpm. I'm stepping up to 75 lb/hr units. I think you may want to consider 83's or even 95's for your application, even a mild boost level on the 540 will probably max those 60's. Remember, with the Procharger you need to factor in a higher BSFC into your calculations; I like to use .60-.65 for the calculations to be on the safe side.

Remember, you really don't want to work the injectors much over 80-85% duty cycle, as that increases the chances of one sticking. Running them static or close to it means the injector driver is in full "on" mode all the time which means constant amperage draw and more heat, both in the driver and in the injector's coils.

Back on the original subject, an N/A 500hp LS1 should be just fine with 42 lb/hr injectors. Assuming a conservative .50 BSFC and plugging in 80% max duty cycle I get 39 lb/hr per injector as the requirement. A little bigger won't hurt things either. The problem with going too big is the pulsewidth at idle gets so small you can't accurately meter the fuel, and you may encounter erratic idle speed/mixture. I'd go with 42 or 52 lb/hr for your application, either will do the job nicely.

Troy

[Cdog]

Cdog, I'm leaving work today, should be home in a couple of days and will consider you offer. What kind of price did you have in mind and will they fit into the ls6 intake on my LS1. I have a factory LS1 PCM, nothing fancy at all, but I am sending it of for reflashing to make it work in the 68, I'm sure my guy can make the necessary adjustments to accomodate the bigger injectors. The 'system' is FAST fuel rails, Aeromotive A1000 pump with electronic controler, 10 and 100 micron filter and Aeromotive regulator. The lines will be -8AN to the rails and -6AN return.

Thanks, Noel

Just shoot me a pm when your ready. Meanwhile i'll talk to the engine guy about your application to make sure these injectors are what you are looking for. I believe they are the right size injectors for your app. I can't remember if their 42lb or 45lb. The engine builder will know. They will support a 500-600 hp engine depending on displacement. As far as price goes, I have to figure out what the new ones will cost but, I know they'll be a good deal for ya.

[Cdog]

You may want to rethink that number. I'm running 55# injectors on my "little" Procharged 353, and they are going static at only 5500 rpm. I'm stepping up to 75 lb/hr units. I think you may want to consider 83's or even 95's for your application, even a mild boost level on the 540 will probably max those 60's. Remember, with the Procharger you need to factor in a higher BSFC into your calculations; I like to use .60-.65 for the calculations to be on the safe side.

Remember, you really don't want to work the injectors much over 80-85% duty cycle, as that increases the chances of one sticking. Running them static or close to it means the injector driver is in full "on" mode all the time which means constant amperage draw and more heat, both in the driver and in the injector's coils.

Back on the original subject, an N/A 500hp LS1 should be just fine with 42 lb/hr injectors. Assuming a conservative .50 BSFC and plugging in 80% max duty cycle I get 39 lb/hr per injector as the requirement. A little bigger won't hurt things either. The problem with going too big is the pulsewidth at idle gets so small you can't accurately meter the fuel, and you may encounter erratic idle speed/mixture. I'd go with 42 or 52 lb/hr for your application, either will do the job nicely.

Troy

I checked my notes and your right. He did say 70-75lb injectors. This is the same guy who builds the test engines for procharger so he know his stuff. Great guy. Al Fonse at www.fonseperformance.com Right now they are testing a 1500 hp BBC and they've run it on the dyno over 50 times and keep throwing more boost at it. If you ever need help with this stuff give him a call. Tell him Corey from Ca sent you. He's the kind of guy who appreciates refferals.