Proper Injection for Forced Induction
12-01-2011, 10:23 AM
#1
CF Veteran
Thread Starter
Proper Injection for Forced Induction
I have a 4.7 with an Avenger on the way with the 5.5 PSI pulley. I'm trying to determine what injector size I am supposed to be running. I'm going to be using an FTC to make adjustments with a 2.5 bar MAP sensor.
I was looking at running an FTC1-019B by Split Second. They make one that is designed to be used by the XJ (Cherokee). The guy that sold it (Avenger) to me is also adding in a 2.5 bar MAP sensor that he used to replace his stock one (only reads vacuum). I will only be running 5.5 PSI however. After looking around a 1.5 bar MAP sensor will read up to 7.5 PSI. I've already got an idea how to adjust the 2.5's readings for proper operation.
Here are the specs I have calculated for my engine:
+ 284~ cc (stock is 242) I got this number by calculating the percentage increase with liters from 4.0 to 4.7, then used the percentage to find out what that equates to in relation to 242, then added it.
+ 4.7 liter
+ 49 PSI fuel pump (98 XJ)
+ 24 lb FI's (Seller said he ran 26 lbs on his 4.0 when it was supercharged. I'm not sure if I should just add 5 more pounds to the injector since stock is 21) Horsepower at the crank is looking to be around 400-410. I just looked at a calculator and it said 47 lbs (493 cc/min flow rate) for 410 HP with 6 cylinders at 80% duty cycle with .55 BSFC (amount of fuel consumed an hour for a supercharged engine is .55-.60). This was measured with a 43.5 PSI fuel pump. Mine is 49. After doing some division and multiplication I came up with 41.1 lbs considering my fuel pump size. This is way off from adding 5 lbs to 26 lbs which leads me to some dangerous confusion.
Here is the calculator I used to come up with these numbers: http://www.witchhunter.com/injectorcalc1.php4
At this point I am going to assume WitchHunter has it correct while my logic of adding 5 lbs to 26 lbs is wrong.
CC~
I was looking at running an FTC1-019B by Split Second. They make one that is designed to be used by the XJ (Cherokee). The guy that sold it (Avenger) to me is also adding in a 2.5 bar MAP sensor that he used to replace his stock one (only reads vacuum). I will only be running 5.5 PSI however. After looking around a 1.5 bar MAP sensor will read up to 7.5 PSI. I've already got an idea how to adjust the 2.5's readings for proper operation.
Here are the specs I have calculated for my engine:
+ 284~ cc (stock is 242) I got this number by calculating the percentage increase with liters from 4.0 to 4.7, then used the percentage to find out what that equates to in relation to 242, then added it.
+ 4.7 liter
+ 49 PSI fuel pump (98 XJ)
+ 24 lb FI's (Seller said he ran 26 lbs on his 4.0 when it was supercharged. I'm not sure if I should just add 5 more pounds to the injector since stock is 21) Horsepower at the crank is looking to be around 400-410. I just looked at a calculator and it said 47 lbs (493 cc/min flow rate) for 410 HP with 6 cylinders at 80% duty cycle with .55 BSFC (amount of fuel consumed an hour for a supercharged engine is .55-.60). This was measured with a 43.5 PSI fuel pump. Mine is 49. After doing some division and multiplication I came up with 41.1 lbs considering my fuel pump size. This is way off from adding 5 lbs to 26 lbs which leads me to some dangerous confusion.
Here is the calculator I used to come up with these numbers: http://www.witchhunter.com/injectorcalc1.php4
At this point I am going to assume WitchHunter has it correct while my logic of adding 5 lbs to 26 lbs is wrong.
CC~
12-03-2011, 07:26 PM
#2
CF Veteran
Join Date: Dec 2011
Location: PA KOTUFU!
Posts: 1,777
Likes: 0
Received 16 Likes
on
15 Posts
Year: 1998
Engine: 4.0L 162,000
I think that you are a bit opitmistic on the HP.
The stroker will add 15% and 5.5lbs boost will add 33%.
190 x 1.15 x1.33 = 290HP + headers, exhaust (+10%) = 320HP max.
Base your injector needs on that HP.
The stroker will add 15% and 5.5lbs boost will add 33%.
190 x 1.15 x1.33 = 290HP + headers, exhaust (+10%) = 320HP max.
Base your injector needs on that HP.
12-04-2011, 06:29 AM
#3
CF Veteran
Thread Starter
(only I have a 4.7 instead of 4.6)
Avenger superchargers increases HP by "100" and Torque by "55%" per their site: http://www.avengersuperchargers.com/
This isn't including any of the modifications I have, and I have many. I did forget to mention that I would be running the hesco aluminum head which hold a lot of weight on the HP. It's 30 HP for a stock engine, and 50 for a 4.2. I have a 4.7 so I'm guessing that I'll have at least 70 added when it's all put together (and that's being very modest). Assuming it only adds 50 to my stroker that takes me from 360 to 410 on the dot at the crank.
12-04-2011, 08:24 AM
#4
CF Veteran
You need to know how much HP it takes to turn the Supercharger.
So its very possible that the engine needs fuel for 400HP even though its only making say 310 at the wheels.
I would look at other engines that are supercharged, the GM 3.8, Ford 3.8 the injectors
the factory used, then increase that by the percentage increase for displacement.
5.5PSI will take around 75HP drag on the crank to generate.
So its very possible that the engine needs fuel for 400HP even though its only making say 310 at the wheels.
I would look at other engines that are supercharged, the GM 3.8, Ford 3.8 the injectors
the factory used, then increase that by the percentage increase for displacement.
5.5PSI will take around 75HP drag on the crank to generate.
12-04-2011, 09:21 AM
#5
CF Veteran
Thread Starter
You need to know how much HP it takes to turn the Supercharger.
So its very possible that the engine needs fuel for 400HP even though its only making say 310 at the wheels.
I would look at other engines that are supercharged, the GM 3.8, Ford 3.8 the injectors
the factory used, then increase that by the percentage increase for displacement.
5.5PSI will take around 75HP drag on the crank to generate.
So its very possible that the engine needs fuel for 400HP even though its only making say 310 at the wheels.
I would look at other engines that are supercharged, the GM 3.8, Ford 3.8 the injectors
the factory used, then increase that by the percentage increase for displacement.
5.5PSI will take around 75HP drag on the crank to generate.
Anyone that thinks a stroker only gains only 15% horsepower over a stock engine isn't familiar with strokers. Even the most base build of a stroker with no other modifications but the crank increases HP by 20%, and no one ever does the bare minimum build. Just adding the Hesco aluminimum head unit alone makes 30 HP on a completely stock engine and that's about 18% alone. If building a stroker only made 15% horsepower then no one would be doing it.
75 HP drag for 5.5PSI on a twinscrew supercharger? That's a lot. It's supposed to produce 100 extra, so does that mean it makes 175 HP, and eats 75 of it? I need way larger injectors based off of that. How did you find out the twinscrew uses 75HP off of the belt? I've been looking and I can't find anything on it.
I looked around and found that Kenne Bell's twinscrew chargers are 90%+ efficient. Let's say Avenger is 5%~ less than that in efficiency simply because they're not "Kenne Bell". What I don't understand is the % efficiency vs. parasitic HP loss. What's the efficiency # for if we already know how much HP a charger eats?
Last edited by CoffeeCommando; 12-04-2011 at 09:29 AM.
12-04-2011, 10:02 AM
#6
CF Veteran
Thread Starter
Ok, I did a search. I found that the Kenne Bell at 5.8 PSI is using 23 HP. Because I'm using Avenger and Kenne Bell is the "leader" in twin screwing (pun intended), that means I can't be using any more than 30 HP. That's a 33% difference in efficiency between avenger and KB, assuming that the Avenger style twinscrew isn't nearly up to par on twin-screws.
That seems much more realistic. I'm running slighly less PSI than that anyways. I found the info.. here: http://www.google.com/url?sa=t&rct=j&q=Parasitic+loss+twinscrew+supercha rger&source=web&cd=2&ved=0CCMQFjAB&url=http%3A%2F% 2Fkennebell.net%2FKBWebsite%2FCommon%2Fpdfs%2Ftwin screw-vs-roots-fromcatalog.pdf&ei=Q5TbTpLQJIiXhQfC1v26Cw&usg=AFQj CNERCnmsRUV83LGzLkPxzrNJttVpnQ
That seems much more realistic. I'm running slighly less PSI than that anyways. I found the info.. here: http://www.google.com/url?sa=t&rct=j&q=Parasitic+loss+twinscrew+supercha rger&source=web&cd=2&ved=0CCMQFjAB&url=http%3A%2F% 2Fkennebell.net%2FKBWebsite%2FCommon%2Fpdfs%2Ftwin screw-vs-roots-fromcatalog.pdf&ei=Q5TbTpLQJIiXhQfC1v26Cw&usg=AFQj CNERCnmsRUV83LGzLkPxzrNJttVpnQ
12-04-2011, 10:07 AM
#7
CF Veteran
Thread Starter
...so after adding 20HP from the head unit (just to be on the safe side) and another 30 parasitic, with 460 HP internal to the engine I need 57.5 lbs with a 43.5 PSI pump, but I have a 49. So that's still 51 lb fuel injectors. This can't be right. That's over a 100% increase in fuel injector size for 5.5 PSI.
Someone help me.
"Project Tweety" (a 4.7 stroker with the Avenger) is estimated to produce 400+ horsepower. I just saw this on their site. So I'm definitely not far off with my numbers.
Someone help me.
"Project Tweety" (a 4.7 stroker with the Avenger) is estimated to produce 400+ horsepower. I just saw this on their site. So I'm definitely not far off with my numbers.
Last edited by CoffeeCommando; 12-04-2011 at 10:18 AM.
Trending Topics
12-04-2011, 10:33 AM
#8
CF Veteran
Join Date: May 2009
Location: Glen Burnie, MD
Posts: 1,844
Likes: 0
Received 3 Likes
on
3 Posts
Year: 1994
Model: Cherokee
Engine: 4.0 H.O. K&N, Borla headers, custom down pipe, magnaflow hi-flo cat, flowmaster to turn down tip
you always want to run your injectors at no more then 80% duty cycle, and i know there is a calculator on here some where, but for example i run 42lb injectors on my Trans Am and it makes about 520 crank horsepower. my duty cycle is pretty close to 80%. now on supercharged/turbo motors, you want to add an extra 20-25% of more fuel capability then Naturally Aspirated engines, so if i was making 520hp with a blower, then i would need 60lb - 70lb injectors.
your engine control unit that controls the supercharger should be running the fuel to air ratio, but you want to make sure that you dont run out of fuel. always better to accidentally run rich on boost then run lean. it can run rich a few times with only causing washed down walls and poor gas mileage, but the first time it runs lean....BOOM!
here is another example, the 2003 mustang cobra uses 39lb hr injectors and makes 390hp to the crank stock
the N/A LS3 makes 426 crank horsepower and uses 42lb hr injectors.
i would just call up ProCharger and tell them exactly what you told us, they will tell you what size you need. they are a very well know supercharger company and are very knowledgeable with this stuff. i would go with 60lb injectors though, just my 2 cents.
your engine control unit that controls the supercharger should be running the fuel to air ratio, but you want to make sure that you dont run out of fuel. always better to accidentally run rich on boost then run lean. it can run rich a few times with only causing washed down walls and poor gas mileage, but the first time it runs lean....BOOM!
here is another example, the 2003 mustang cobra uses 39lb hr injectors and makes 390hp to the crank stock
the N/A LS3 makes 426 crank horsepower and uses 42lb hr injectors.
i would just call up ProCharger and tell them exactly what you told us, they will tell you what size you need. they are a very well know supercharger company and are very knowledgeable with this stuff. i would go with 60lb injectors though, just my 2 cents.
12-04-2011, 10:56 AM
#9
CF Veteran
Thread Starter
you always want to run your injectors at no more then 80% duty cycle, and i know there is a calculator on here some where, but for example i run 42lb injectors on my Trans Am and it makes about 520 crank horsepower. my duty cycle is pretty close to 80%. now on supercharged/turbo motors, you want to add an extra 20-25% of more fuel capability then Naturally Aspirated engines, so if i was making 520hp with a blower, then i would need 60lb - 70lb injectors.
your engine control unit that controls the supercharger should be running the fuel to air ratio, but you want to make sure that you dont run out of fuel. always better to accidentally run rich on boost then run lean. it can run rich a few times with only causing washed down walls and poor gas mileage, but the first time it runs lean....BOOM!
here is another example, the 2003 mustang cobra uses 39lb hr injectors and makes 390hp to the crank stock
the N/A LS3 makes 426 crank horsepower and uses 42lb hr injectors.
i would just call up ProCharger and tell them exactly what you told us, they will tell you what size you need. they are a very well know supercharger company and are very knowledgeable with this stuff. i would go with 60lb injectors though, just my 2 cents.
your engine control unit that controls the supercharger should be running the fuel to air ratio, but you want to make sure that you dont run out of fuel. always better to accidentally run rich on boost then run lean. it can run rich a few times with only causing washed down walls and poor gas mileage, but the first time it runs lean....BOOM!
here is another example, the 2003 mustang cobra uses 39lb hr injectors and makes 390hp to the crank stock
the N/A LS3 makes 426 crank horsepower and uses 42lb hr injectors.
i would just call up ProCharger and tell them exactly what you told us, they will tell you what size you need. they are a very well know supercharger company and are very knowledgeable with this stuff. i would go with 60lb injectors though, just my 2 cents.
What PSI is your fuel pump?
12-04-2011, 11:17 AM
#10
CF Veteran
Thread Starter
60 lbs is massive. I'm wondering whether or not I should install this thing. I've always wanted to supercharge a vehicle, but the size of the fuel injectors is making me think twice. I might just sell this thing to the highest bidder. I just wanted a little added HP. I'll have to see what size pulleys I can get to lower the PSI a little. Maybe 3.5'ish. I wasn't expecting to run any larger than 34 lb injectors.
12-04-2011, 12:39 PM
#11
CF Veteran
Even though you was insulting and recanted.....
A 4.6L Ford with Kenne Bell SC on it.
http://www.kennebell.net/supercharge...ra_99-014v.htm
From the quote above assuming the Ford uses about the same fuel pressure as an XJ,
42lb injectors should be all you need. Your not going to have the volumetric efficiency of the DOHC 4V Ford and the HP it makes so I can see any reason your going to need more fuel than that.
One thing I forgot, that is with 8 injectors and you only got 6 injectors..... So 42*8/6=56lb.
So if your planning on making 400HP or close to it your 60lb would not be that far off.....
The original Ford 3.8L Supercharged T-Bird was reported to have a crank load of 275 to 300HP on the bearings from an old MM&FF article and used the same style whipple charger as the Avenger or Bell, and produced around 220HP at the wheels and thus the reason for the 75HP drag in my earlier post.
Good luck with your build.....
A 4.6L Ford with Kenne Bell SC on it.
42lb Injectors - At 5 psi, the 80mm stock meter is "pegged" at 400HP and 5 psi. The Kenne Bell 90mm and Cool Air Kit make another 26HP and 6.5 psi, but the stock injectors - particularly older worn injectors - become marginal. New 42lb injectors (not shown in photo) included in this kit.
From the quote above assuming the Ford uses about the same fuel pressure as an XJ,
42lb injectors should be all you need. Your not going to have the volumetric efficiency of the DOHC 4V Ford and the HP it makes so I can see any reason your going to need more fuel than that.
One thing I forgot, that is with 8 injectors and you only got 6 injectors..... So 42*8/6=56lb.
So if your planning on making 400HP or close to it your 60lb would not be that far off.....
The original Ford 3.8L Supercharged T-Bird was reported to have a crank load of 275 to 300HP on the bearings from an old MM&FF article and used the same style whipple charger as the Avenger or Bell, and produced around 220HP at the wheels and thus the reason for the 75HP drag in my earlier post.
Good luck with your build.....
Last edited by Caish; 12-04-2011 at 01:18 PM.
12-04-2011, 01:37 PM
#12
CF Veteran
Just did a quick google and found this.
http://www.witchhunter.com/injectorcalc1.php4
six 42lb injectors @80% at 43psi can produce 400HP.
http://www.witchhunter.com/injectorcalc1.php4
six 42lb injectors @80% at 43psi can produce 400HP.
12-04-2011, 05:29 PM
#13
CF Veteran
Thread Starter
Just did a quick google and found this.
http://www.witchhunter.com/injectorcalc1.php4
six 42lb injectors @80% at 43psi can produce 400HP.
http://www.witchhunter.com/injectorcalc1.php4
six 42lb injectors @80% at 43psi can produce 400HP.
Another site I found with a calculator said for SC'ed engines it had to be between .6 and .7, so that's conflicting information.
I input my stroker information and it says I'm supposed to run 27's. I have 24's in there. I know at idle when I was looking at the fuel trims it stayed right at 0%. Didn't check it while I was throttling it though.
12-04-2011, 07:32 PM
#14
CF Veteran
Join Date: Dec 2011
Location: PA KOTUFU!
Posts: 1,777
Likes: 0
Received 16 Likes
on
15 Posts
Year: 1998
Engine: 4.0L 162,000
I just finished putting a Powerdyne S/C on my F150 4.6L truck at 7-8lbs boost and I am using 36 lb injectors. Stock is 220HP + 8/16boost is about 330HP.
See: http://www.f150online.com/forums/sup...t-98-4-6l.html
Still on a 280CID (4.6L) engine that is not optimixed as far as compression ration and intake manifold etc with 8.5-9.0:1 CR and stock Jeep intake madifold the most you can expect is about 1.1HP/CID So that is 310HP but I would say you are closer to 1.0HP/CID around 280HP. Again with 5.5lbs boost you can add 30-35%max HP.
So, 280-310HP + 30-35% = 364-418HP but probably closer to 375HP and only 6 injectors and you are looking at about 72 lb injectors. But you are only doubling the stock HP 190 to 380 and stock is 22lb injectors so double but the stock is lean so ? 50 lb injectors. You need a wideband A/F ratio meter and see where you are. You are in unchartered territory. Good luck.
See: http://www.f150online.com/forums/sup...t-98-4-6l.html
Still on a 280CID (4.6L) engine that is not optimixed as far as compression ration and intake manifold etc with 8.5-9.0:1 CR and stock Jeep intake madifold the most you can expect is about 1.1HP/CID So that is 310HP but I would say you are closer to 1.0HP/CID around 280HP. Again with 5.5lbs boost you can add 30-35%max HP.
So, 280-310HP + 30-35% = 364-418HP but probably closer to 375HP and only 6 injectors and you are looking at about 72 lb injectors. But you are only doubling the stock HP 190 to 380 and stock is 22lb injectors so double but the stock is lean so ? 50 lb injectors. You need a wideband A/F ratio meter and see where you are. You are in unchartered territory. Good luck.
Last edited by CobraMarty; 12-04-2011 at 08:01 PM.
12-04-2011, 08:08 PM
#15
Seasoned Member
Join Date: Dec 2011
Location: Texas
Posts: 307
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1997
Model: Cherokee
Engine: 4.0L Inline 6
With injector sizes being larger, can they still open small enough to maintain correct fuel/air mixture for say a completely stock engine (maybe not that extreme). Or is the pulse width size bracketized so with larger sizes the minimum runs larger too?
What PSI is your fuel pump?
What PSI is your fuel pump?
Just FYI, most stock cars don't run injectors at near peak IDC's.
I just tuned a single cab chevy with an LS3 that made 427 to the wheels and while it has 82lb injectors, I'm only running them at around 45-48 lbs to keep the IDC's low.
I agree with those numbers being a bit optimistic. The stroker with mods might make about 200-215 to the wheels. I would expect maybe 270-300 with the supercharger. Search for a vehicle that comes stock with that amount of power and swap those in to save cash.