Big HP fuel problems (pic) Solutions?
06-13-2010, 04:17 PM
#76
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Chrysler Crossfire
Stock injectors flow 36 lbs/hr at 3bar. We've had great results upgrading the M112k injectors to 42-48 lbs/hr depending on the particular application.
Good luck with your project!
Good luck with your project!
06-13-2010, 04:37 PM
#77
Super Member
Thanks for the info!, I think I jumped the gun when I got the other injector, I did not relize at the time there were alot of bosch injectors on the market that are very resonable in price and may drop right in.
06-14-2010, 02:43 AM
#78
With all this talk about injectors I have one question. Is there a specific timeline when to change or clean injectors? I'm thinking about removing mine and having them sent out to be cleaned and calibrated.
06-14-2010, 12:07 PM
#79
MBWorld Fanatic!
One more pic, Since it seems difficult to the exsact spec's on the stock injector lets say it 400cc at 43.5 is close if o the injectors next to it in the image should flow 499cc at 43.5. The clips wil have to be changed and the mounting tabs on the rail may have to have a very slight bend in it to move the injector down a bit but I got all 8 for 120.00 so little tweaking i can live with. The clips are on a car the as been poduced into the millions so locating them should no be hard.
The stock injectors look like bosch Type 3. Lots of cars use them, notably LS GM engines, ford cobra 4.6's and turbo volvo's. Should be able to find a suitable match up to 60lb/hr ( Big green 42# can be found here: http://www.bmotorsports.com/shop/pro...oducts_id/1602). Do we know what the rail pressure is? looks like a bosch regulator in the rail at the back, what is stamped on that?
06-14-2010, 02:41 PM
#80
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Thread Starter
KLR CLS; Rail pressure should be at 80psi on a good working system..
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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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06-14-2010, 03:05 PM
#81
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06-14-2010, 04:01 PM
#82
Out Of Control!!
Exotic is correct. MB uses very high fuel pressure on the 55k cars. A properly running car should be at 80 PSI fuel pressure.
06-14-2010, 11:23 PM
#84
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BMW's
I have had stock 55k injectors flow tested in the past and they are 44lbs @43.5 psi injectors.
I would suggest those guys that are near the 600bhp mark or overshould run close to 54lbs injectors and get your car tuned for them, your tuner should be able to calculate your injector size for your application so ask for them to help you with that before over doing it.
I would suggest those guys that are near the 600bhp mark or overshould run close to 54lbs injectors and get your car tuned for them, your tuner should be able to calculate your injector size for your application so ask for them to help you with that before over doing it.
I've seen guys mentioning duty cycles when others inquire about their engine builds.
An injector is just a valve which is controlled by the ECU with an electrical signal that lasts a specific period of time called a "pulse width" usually measured in milliseconds. In terms of fuel injectors they're either open or closed. However, since you cannot simply open an injector all the way instantaneously due to simple physics it takes a small amount of time to go from 0% open to 100% open. It's this lag in the injector that causes problems at extreme ends of duty cycle.
Duty cycle (DC) is a measurement of how long the injector is open relative to how long it is closed. 50% DC means that the injector is open half the time. At 100% DC it's just open all the time and delivers the maximum amount of fuel as the injector is rated for. You cannot have a valve open more than 100% of the time. Oh there's no such thing as 110% duty cycle!
If you exceed 80% duty cycle then you get problems with the timing of the injector opening and closing in relation to the intake stroke of the engine when you're telling an injector to open and close 18 times a second or more and you can run the risk of running an injector static.
2%-80% duty cycle is fine for normal injectors. The problem of the injector opening and closing quickly enough at elevated DC's is realized as the time it takes the valve to close and reopen gets shorter and shorter.
Think of 90%-100% DC as "valve float" for fuel injectors. The time between the ECU's electrical signal turning the injector off and back on again is shorter than the time it takes for the physical injector solenoid to open and close. The effect of this is inconsistent fuel delivery. The injector is neither closed nor open and as such it's not delivering the proper amount of fuel. Considering that high duty cycle normally only occurs at elevated manifold pressures and means that your engine is running at maximum cylinder pressure. Essentially you run your engine lean at wide open throttle and you end up with detonation.
The opposite is true with very large injectors at low duty cycle but without the damage from detonation (low cylinder pressure). If you have a small 100cc/min injector at idle/part throttle operation it's easier to control than a 1000cc/min injector in the same engine. If you have the 100cc/min injector running a 10 millisecond pulse width (.010 seconds) you get ~.017ccs of fuel.
Example:
100cc/min / 60 seconds = 1.667ccs per second
1.667ccs/.010 seconds = .017ccs
100cc/min / 60 seconds = 1.667ccs per second
1.667ccs/.010 seconds = .017ccs
1000cc/min / 60 seconds = 16.667ccs per second
16.667ccs/.010 seconds = .167ccs
16.667ccs/.010 seconds = .167ccs
If you ran the 1000cc injector at the same pulse width you'd get ~.17ccs. That's 10 times the amount of fuel you need. So you'd have to crank the injector pulse back to 1/10th of 10 milliseconds or .001 seconds. It's very hard to control a large injector in such a short period of time. The ECU quickly commands the injector to open and close, but by the time the electrical signal ends the 1000cc injector has barely even opened. The effect of large injectors on low rpm operation is that you have inconsistent fueling, poor atomization, harsh driveability, and poor emissions.
So, running larger injectors is generally a good idea if you have extensive modifications to your engine that might push the limits of the factory injectors. A short term fix for stock injectors is an adjustable fuel pressureregulator. With the adj. regulator you can artificially increase the flow rating of the stock injectors by raising the fuel pressure, but it should only be used until properly sized injectors can be sourced and retuned.
I will be doing some extensive research on this and come up with a complete overhaul plan for the fueling system.
Last edited by Tony the Tuner; 06-14-2010 at 11:27 PM.
06-15-2010, 07:03 AM
#85
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05 ML-500 , 03 CLK5.5 AMG has left the Garage
Injectors
Thank you very Much. _PTEngineering
Talked to Rflow 306 ( Albert ) I asked about his fuel pressure. He said it pretty much stayed at 70 PSI ( Hot or Cold) and it was constant , 70 psi while racing or street driving. The only time he had a drop in the fuel pressure @ the fuel rail, is when he hit the NOS. It would drop about a 1.5 lbs and only for about 1 second . There is a control unit that keeps track of the fuel pumps Current draw and adds or subtracts to keep the fuel pressure constance. I even checked with the SLR tech @ my local dealer. This info is hard to find. The SLR techs remembers it to be about 4.2 Bar. on the Kompressor engines he has worked on. . Cheers _PTEngineering
Talked to Rflow 306 ( Albert ) I asked about his fuel pressure. He said it pretty much stayed at 70 PSI ( Hot or Cold) and it was constant , 70 psi while racing or street driving. The only time he had a drop in the fuel pressure @ the fuel rail, is when he hit the NOS. It would drop about a 1.5 lbs and only for about 1 second . There is a control unit that keeps track of the fuel pumps Current draw and adds or subtracts to keep the fuel pressure constance. I even checked with the SLR tech @ my local dealer. This info is hard to find. The SLR techs remembers it to be about 4.2 Bar. on the Kompressor engines he has worked on. . Cheers _PTEngineering
Last edited by PTE; 06-15-2010 at 08:13 PM.
09-15-2014, 10:43 PM
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CLS55 AMG, ML63 AMG, Cayenne S
If I want to replace sending unit and filter, then it should be two A 211 470 45 94 Delivery Unit with Fuel Level Sensor and Fuel Filter?, one for each side, correct?
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