Injector size/flow
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E55 AMG
W211 E55 Injector size/flow
from what I read the w211 e55 has 440cc injectors but is that at 43.5 psi or is that at a different pressure. What do the factory fuel injectors flow at 80psi, 70psi? Reason for asking is I want to know how much power I can push with the factory fuel injectors with a looped fuel rail and a health fuel pump?
Last edited by Bay510E55; Jun 15, 2020 at 11:32 AM. Reason: specificity
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2005 e55 AMG
Simple answer. The injectors are rated at their psi so lets say 440 cc at 43 psi. Now if you put more pressure behind the injector it will flow more fuel. So our stock injectors will flow 440cc at 43 psi and that is rated at 100% open injector.
The technical part.....
At 60 psi your injectors will flow, 520cc, at 70 psi, 561cc, at 80 psi 600cc. Look on line for "Injector flow rate or duty cycle or horse power " and the online calculators will pop up to help you.
Your fuel system will more than likely not hold 80psi so 65-70 is more like it at full tilt.
Remember injectors are really not made to stay open 100% and 80-85 % duty cycle is more acceptable and that will bring your flow rate down even more.
Then we need to know how rich you want the engine to run as supercharged engines need more fuel on average to keep the cylinders cool and prevent a lean condition
Get a good wide band and your engine will live a happy life.
I run 630cc injectors at 65 psi but run them at 95 % duty cycle because I keep the AFR around 11.5 and 10.6 on Nitrous so stepping up to 750cc would me my next jump to be safe and keep the duty cycle down a little.
The technical part.....
At 60 psi your injectors will flow, 520cc, at 70 psi, 561cc, at 80 psi 600cc. Look on line for "Injector flow rate or duty cycle or horse power " and the online calculators will pop up to help you.
Your fuel system will more than likely not hold 80psi so 65-70 is more like it at full tilt.
Remember injectors are really not made to stay open 100% and 80-85 % duty cycle is more acceptable and that will bring your flow rate down even more.
Then we need to know how rich you want the engine to run as supercharged engines need more fuel on average to keep the cylinders cool and prevent a lean condition
Get a good wide band and your engine will live a happy life.
I run 630cc injectors at 65 psi but run them at 95 % duty cycle because I keep the AFR around 11.5 and 10.6 on Nitrous so stepping up to 750cc would me my next jump to be safe and keep the duty cycle down a little.
Last edited by SICAMG; Jun 15, 2020 at 07:49 PM.
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From: Joshua, TX
2004 AMG E55
I logged injector pulse width, fuel pressure, and AFR on an Innovate data aquisition system. . At 80 psi (stock fuel system) I hit 95% injector duty cycle with stock injectors at full throttle. I dropped 12 psi to 68 psi under full load. AFR stayed steady.
My mods at that time were 77mm FSP, 82mm throttle body, stock cooling system other than CWA100 and engine bay tank.
When I added headers (long tube) I went to 630cc injectors and I am now at 67% duty cycle. AFR's were still steady. I drop about 10 psi (80-70psi). This is a 2004 E55 with 115k miles at the time.
I would consider a 77mm FSP andd 82mm with no headers over the limit of stock injectors as:
1. They have high miles on them and failure potential is higher
2. Anything over 85% duty cycle is asking for an injector to go static and hydro lock a cylinder.
My mods at that time were 77mm FSP, 82mm throttle body, stock cooling system other than CWA100 and engine bay tank.
When I added headers (long tube) I went to 630cc injectors and I am now at 67% duty cycle. AFR's were still steady. I drop about 10 psi (80-70psi). This is a 2004 E55 with 115k miles at the time.
I would consider a 77mm FSP andd 82mm with no headers over the limit of stock injectors as:
1. They have high miles on them and failure potential is higher
2. Anything over 85% duty cycle is asking for an injector to go static and hydro lock a cylinder.
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E55 AMG
The premise for all these questions is because of a discussion with kleemann. The tuners there say that injectors aren required until about 650whp. They said that tunes for larger injectors sacrifice idle and drivability and risk washing out your cylinders when running bigger injectors. I spoke to a member that has there tune and has factory injectors and has run a high 10 second 1/4 and praises there tune over all the other tuners such as eurocharged.
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From: Texas
2003 CL55
Pressure is key component to injector flow but line size can be a limit at a certain point as well. You can run much larger injectors and not wash out engine with tune. I ran 550CC @80psi and 850 CC @ 80psi. I have seen plenty of M113k fails at 560 RWHP range with stock injectors over the years. Old injectors can flow less. When the temps and barometer drop in the winter, fuel demand goes up and engines can lean out with stock injectors and to many mods. Not many cars that you can add 100 RWHP without adding more fuel. These engines make 415 to 430 RWHP stock IMO, all M113k engines on the road should have least changed or rebuilt their injectors by now. They are 14 to 18 years old. Rubber o rings and sitting around that long requires service on any high performance car .
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E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
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instagram @ultimate_pd
facebook.com/ultimatepd
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2005 e55 AMG
Exotic got above me just as I finished typing so repeating of what he said.
Remember it is not so much for the horse power calculation. It is ALOT also about BSFC and where your engine need to be. I run at about .60 bsfc that put's a lot of extra fuel into the engine for safe guard....and run 25 degrees of timing. This requires more injector to keep up with that demand.
I leave horsepower on the table but do not care. The engine lives. Every engine is different and where you live temperature wise is huge as well.
Also the O-2 sensors keep the engine running clean with the larger injectors. I run 630cc and the AFR is 15.1 at cruise and runs perfectly clean. Gets the same mileage as my stock injectors did.
Remember it is not so much for the horse power calculation. It is ALOT also about BSFC and where your engine need to be. I run at about .60 bsfc that put's a lot of extra fuel into the engine for safe guard....and run 25 degrees of timing. This requires more injector to keep up with that demand.
I leave horsepower on the table but do not care. The engine lives. Every engine is different and where you live temperature wise is huge as well.
Also the O-2 sensors keep the engine running clean with the larger injectors. I run 630cc and the AFR is 15.1 at cruise and runs perfectly clean. Gets the same mileage as my stock injectors did.
Last edited by SICAMG; Jun 17, 2020 at 10:48 AM.
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Thread Starter
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E55 AMG
Exotic got above me just as I finished typing so repeating of what he said.
Remember it is not so much for the horse power calculation. It is ALOT also about BSFC and where your engine need to be. I run at about .60 bsfc that put's a lot of extra fuel into the engine for safe guard....and run 25 degrees of timing. This requires more injector to keep up with that demand.
I leave horsepower on the table but do not care. The engine lives. Every engine is different and where you live temperature wise is huge as well.
Also the O-2 sensors keep the engine running clean with the larger injectors. I run 630cc and the AFR is 15.1 at cruise and runs perfectly clean. Gets the same mileage as my stock injectors did.
Remember it is not so much for the horse power calculation. It is ALOT also about BSFC and where your engine need to be. I run at about .60 bsfc that put's a lot of extra fuel into the engine for safe guard....and run 25 degrees of timing. This requires more injector to keep up with that demand.
I leave horsepower on the table but do not care. The engine lives. Every engine is different and where you live temperature wise is huge as well.
Also the O-2 sensors keep the engine running clean with the larger injectors. I run 630cc and the AFR is 15.1 at cruise and runs perfectly clean. Gets the same mileage as my stock injectors did.
I would just like to remind everyone that your injectors are sized at around 43psi fuel pressure and not 80psi the m113k engines produce so your 550cc are more like 645 and your 630cc is more like a 745cc injector.
Last edited by Bay510E55; Jun 17, 2020 at 04:38 PM. Reason: additional info
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Joined: Jan 2019
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From: White Rock B.C. Canada
2006 CLS55
630cc injectors
Exotic got above me just as I finished typing so repeating of what he said.
Remember it is not so much for the horse power calculation. It is ALOT also about BSFC and where your engine need to be. I run at about .60 bsfc that put's a lot of extra fuel into the engine for safe guard....and run 25 degrees of timing. This requires more injector to keep up with that demand.
I leave horsepower on the table but do not care. The engine lives. Every engine is different and where you live temperature wise is huge as well.
Also the O-2 sensors keep the engine running clean with the larger injectors. I run 630cc and the AFR is 15.1 at cruise and runs perfectly clean. Gets the same mileage as my stock injectors did.
Remember it is not so much for the horse power calculation. It is ALOT also about BSFC and where your engine need to be. I run at about .60 bsfc that put's a lot of extra fuel into the engine for safe guard....and run 25 degrees of timing. This requires more injector to keep up with that demand.
I leave horsepower on the table but do not care. The engine lives. Every engine is different and where you live temperature wise is huge as well.
Also the O-2 sensors keep the engine running clean with the larger injectors. I run 630cc and the AFR is 15.1 at cruise and runs perfectly clean. Gets the same mileage as my stock injectors did.
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04 E55 AMG (totaled), 07 S550 4Matic, 14 E63S
For fun, injector flow increases with the square root of proportional pressure increase. So an injector rated at 500cc at 43 psi would flow the equivalent of a 500*sqrt(75/43) = 660cc injector at 75 psi.
