articfriends

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As many of you have seen I have been posting about dynoing a slightly modified 502 mpi in my shop. After seeing some erratic afrs on dyno I replaced #8 injector with another used one. The erratic afr readings on that cylinder went away. This disturbed me as I am not monitoring 6 of the 8 cylinders so IF one of the 2 I'm monitoring was going lean then coming back to normal WHATS going on in the ones I cant see?? So I made the decision to buy a injector flowing, cleaning testing machine with a ultrasonic cleaner also. As soon as I got it I promptly flowed the 13 MPI 502 injectors I have, saw a 22% difference from the best to worse, saw several that at higher rpms just dont come close to the average. Also flowed a set of 500efi injectors, they too had a good 15 % difference and one was stuck open. Flowed a set of siemans deka 80 lb ones I had from blower motor that only had 5 hours or so of total run time on dyno that were never in the boat , a good 8-10% difference from best to worst on 7 of them with one that outflows the rest of them by a good 20%. Bought a set of "replacement" 502 mpi injectors from a seller on ebay that claimed matched and flow tested within one percent, TOLD seller I was going to be testing them, he assured me they were good. They were the WORST by far with a good 40% difference from best to worst PLUS they started shutting down at 40 psi and by 3 bar/ 43.5 ALL shut down completely!!
After cleaning, reverse flowing then flowing 20+ times I was able to find 8 of the mpi stock injectors that were plus or minus 6% of average (published data on racetronix website shows the majority of NON matched injectors you buy are either 4% or 6% +/_). Sent e-bay injectors BACK-TOTAL JUNK. After flowing, cleaning the siemans dekas they were closer to 4% +/- except for the over achiever that still flows 10+% more than the rest, quite disturbed that they got so bad from 5 hours of run time and sitting around about as long as what a boat normally sets all winter. Think about that, IF you were tuning a motor using a afr meter in each collector you could have 1 cylindermaking you think you are too rich when you really have one thats too rich and 3others that are lean. The 500efi injectors came in fairly good after cleaning except one weak one that flows consistently low. On the advice of Racetronix I am no longer going to flow any used injectors until after they are cleaned as to not foul testing solution in machine.
Also bought a set of matched 63 lb siemans dekas that tested within 2% =/- on my machine (its a entry level machine, not a 10,000$ one by any means but not a cheap Chinese import) so at least gives me a good picture of whats going on.
A fellow osoer sent me 16 injectors from a 502 mpi that ran fine but suffered reversion, AFTER cleaning and flow testing/reverse flowing the ones I have done so far are within +/- 7%, originally one was stuck on until ran thru ultrasonic for 4 cleaning cycles, they too started out quite out of range. I am disturbed that they are so bad in general, there is no wonder mercruiser tunes their motors so pig rich, if they tuned them to the edge and a injector flowed 10-15% LOW no wonder there are so many horror stories on here of burned up motors!!
What my feelings now are is I would NEVER buy a set of injectors that weren't match flowed to start with, still flow them to see for sure they do match ("matched/flowed injectors" is a claim made by many injector suppliers) and they need to be cleaned and tested anytime a motor is being rebuilt or apart, if your tuning afrs on a injected motor its prob best to go a little richer than what you think would be good for a safety margin down the road, maybe their is some merit to filling a water separator up with injector cleaner once a season or so, and all of these 502 mpi injectors for sale on ebay are cheap Chinese knockoffs, coils so weak they cant open at 43.5 psi, WTF???. In past I had sent my blower motor injectors to Crockett everytime I had it apart, I would now consider that 100% mandatory and fool hardy NOT to! Thought I'd share, Smitty
the picture is of the supposed matched set tested at 40 psi that I bought on ebay!

articfriends

iTrader: (1)

After seeing afrs all over the place I also invested in a daytona 8-pack o2 sensor setup for my dyno so I could see whats really going on in all the cylinders!

BUP

iTrader: (9)

Just bought 16 new injectors for these 502's to send to OSO member. OEM from Italy. His flow testing was bad as well. I suspect about 6 of them were ebay fake injectors as they all flow different as well. None of those flowed the same at all. Again DO NOT BUY INJECTORS from the net. You are asking for problems.

Even new injectors need to be tested. Simple tests first are for OHM's and you will see a difference in those as well. (New injectors) Test running Impedance and that will be different as well between new injectors. Funny Actually sad how they are not even meeting OEM spec differences between new injectors.

For a injector test machine - It is best to have a separate back flush system set up away from the path of the machine testing fluid. I do this always first before any flow testing of the injectors. The back flush really can help even new injectors plus nasty used injectors but not all the time. Keep in mind injectors are electrically and mechanically devices - with that said the electric portion of the injectors plays a huge role as well and no way a person can fix that other than sending it off to get remaned by professionals.

14 apache

iTrader: (1)

How are the bosch injectors out of the box?

Baja Rooster

iTrader: (1)

Generally speaking, for the sake of preservation, a TBI system might be more reliable than a TPI system with individual injectors?

articfriends

iTrader: (1)

Well, as bad as i have seen these injectors varying you would think there would be efi motors washing rings and melting down all over the place BUT other than a occasional post about a burnt piston here and there and motors with blowby from washed pistons surprisingly i havent seen alot of threads about efi motors going down so i wouldnt say tbi injectors would be a better solution. Alot of boats with black transoms though

articfriends

iTrader: (1)

Talking to rcinjection tech they tell me the reason you dont see it in cars is they dont sit like boats do but after what im seeing im definately NOT going to tune motors no more without leaving a little extra fuel in the tunes to account for injector degradation.

articfriends

iTrader: (1)

When bought in shelf stock, non matched sets Bosch says this:
Static Flow Tolerance +/-%: 5%
BUT I haven't tested any new ones yet, you could see 10% from best to worst new if what they say is true

Budman II

iTrader: (1)

Hmmm, would we be better off going back to carb setups?

A lot of us would probably toss and turn all night long if we truly knew what was really going on inside our engines. Nonetheless, excellent technical investigative work.

liquidlounge

iTrader: (1)

Once again Arctic, just GREAT and useful information. Thanks for sharing!