Injectors

[Tejun]

How many of you have replaced the injector on your Hisun ?  Where did you purchase your replacement injector from ?  I've replaced my injector twice. Replaced the original with an injector I purchased on eBay (from Dr Motorcycle I think), and then found one on Amazon. Yesterday I dropped both injectors that had been replaced at an Injector Cleaning shop. They will test them to see how they were performing before doing anything, then, clean,  replace the basket on inlet and both orings then run another test. The cost is $18/injector. I'm anxious to see the results.

[Easyrider]

Please post the results when you get them, really interested to see if it's worth the money because new injectors for the hisun aren't cheap!  Also where did you find this place to clean the injectors?

[Tejun]

They are in Houston (actually I think Sugarland). I’ve used them to test/clean the injectors for my Yamaha outboard. Will definitely give update after I pick them up next week. 
 

www.injectorrx.com 

[cliffyk]

I have never needed to replace a fuel injector in anything--I have upgraded them to higher capacity numerous times. Cleaning them is easy, I connect a 4" or so long piece of vinyl tubing; of appropriate ID to fit snugly;  to the outlet end of the injector,. Next fill the tube with cheap Super Tech carburettor cleaner from Walmart. Pressurize the tubing with compressed air to 40 to 45 psi¹ then activate the injector. Do that 2 or 3 times and it will be clean. Some do this from the inlet end, however I have found  back flow flushing to be more effective.

I also have a rig using a 100 cc graduated column (actually a big syringe) that allows me to time how long it takes the injector to squirt 100 cc of fluid--I use naphtha--that provides a pretty good indication of it's flow rate.

CAUTION: Make sure you do any of this in a well ventilated area--and use an enclosed switch to trigger the injector. Flammable aerosols and nearby sparks can make bad things happen!

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¹ - Most fuel injectors are rated at an operating pressure of 3 bar (43.5 psi).

[Tejun]

Got the injectors back today. They found the original injector (one it came with) to be bad and not serviceable. The replacement injector I had purchased off eBay, but not from Motorcycle Dr as I originally thought, was found with a Fair spray pattern and after cleaning it was upgraded to Good. Static Flow increased from 280 to 292 after cleaning.... (not sure what the 280 or 292 value measurement is). Attached is the report they provide when the work is completed.  Another note worthy detail is they do not charge for testing an injector that is found to be bad. All, in all I think the $18 + tax is pretty reasonable if the results are positive.

Anxious now to get back home and install the newly cleaned injector and see what (if any) the results are.

Injector Report 12162020.pdf

[cliffyk]

"Static flow" rate is the flow in units of quantity per unit of time with the injector held open. The 280 and 292 values are the flow in cc/min (cubic centimeters per minute)--divide cc/min by 10.5 to estimate the flow in lbs/hour (pounds per hour).

Gasoline weighs 6.073 to 6.2 lbs per gallon  (87 to 93 octane);

one gallon = 3785.4 cc,--therefore 1 cc = 0.00026417 gallon = 0.0016043 pounds (87 octane);

1 cc/min (87 octane) = 0.0962583 lbs/hour (0.0016403 * 60);

292 cc/min  = 28.1 lbs/hour (292 *0.0962583) (87 octane)

It looks like Injector ℞ used 6.0 lbs/gallon--close enough...

At 6.0 lbs/gallon, 1 cc/min = 0.0951012 lbs/hour; * 292 = 27.7695 lbs/hour.

[cliffyk]

BTW: fuel injector flow is pretty much directly relaed to the maximum HP an engine can produce--per this formula:

BSFC = Brake Specific Fuel Consumption; the rate of fuel consumption divided by the HP produced. The rule of thumb value for  naturally aspirated gasoline engines is 0.45 to 0.5 pound per hour per horsepower. So, our 27.77 l/h injector operating at a not actually feasible or possible 100 % duty cycle  could (if possible) support:

(27.77 * 1 [100%]* 1  [cylinder]) / 0.45 [BSFC] = 61.7 HP.

But at practical  75% duty cycle --and assuming dynamic flow rates at less than the static flow rate digress along a linear curve (hint: they do not)-- we get:

(27.77 * 0.75 [75%]* 1  [cylinder]) / 0.45 [BSFC] = 46.28 HP.

Or more likely 40 to 44 HP in our real world.

Back in my supercharged Mustang and Miata days I spent a lot of time pouring over crap like this

[Easyrider]

Thanks for all the great info...much appreciated!!

[Tejun]

3 hours ago, cliffyk said:

BTW: fuel injector flow is pretty much directly relaed to the maximum HP an engine can produce--per this formula:

BSFC = Brake Specific Fuel Consumption; the rate of fuel consumption divided by the HP produced. The rule of thumb value for  naturally aspirated gasoline engines is 0.45 to 0.5 pound per hour per horsepower. So, our 27.77 l/h injector operating at a not actually feasible or possible 100 % duty cycle  could (if possible) support:

(27.77 * 1 [100%]* 1  [cylinder]) / 0.45 [BSFC] = 61.7 HP.

But at practical  75% duty cycle --and assuming dynamic flow rates at less than the static flow rate digress along a linear curve (hint: they do not)-- we get:

(27.77 * 0.75 [75%]* 1  [cylinder]) / 0.45 [BSFC] = 46.28 HP.

Or more likely 40 to 44 HP in our real world.

Back in my supercharged Mustang and Miata days I spent a lot of time pouring over crap like this

Thanks !! good stuff for sure

[Tejun]

Installed the injector serviced by InjectorRx  today and the  engine ran better than it ever has. Proof will be in a sustained improvement but initial results are great. Planning to bring the injector I removed to them for servicing to have a spare

[Easyrider]

Thats awesome, great decision! Thanks for all the great info...much appreciated!!