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Merc Injectors. How big are they really?

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  • Merc Injectors. How big are they really?

    I've seen three different flow rates mentioned for the 0-280-150-036 injectors. 380cc, 420cc, and 480cc. I can only recall one person posting results of a flow test which was Gregmatic. His results showed the injectors flow ~420cc @ 50psi. Now if you calculate the flow at a more standard 43psi test pressure you get roughly 380cc. This is the same flow stated on most documents (online and in books) that I've seen for this particular injector. I believe 380cc to be the correct flow rate. Of course which base fuel pressure you go by changes that.

    Also, the fuel pressure regulator on the z31 keeps fuel pressure at a constant ~37psi. At 37psi the same injector will flow ~362cc which is pretty low. It should be noted that many newer Nissan models (z32, 240sx,..) run a base pressure of ~43 psi which would make the injectors flow the documented 380cc.


  • #2
    I bought a used set of Bosch 420cc's from a guy down here. Around that same time, Morgan still had his 240 running with the L28 and was having problems with it breaking up at high rpms I believe. Anyway, he ruled out about everything but the injectors. He asked if anyone had a set he could borrow and he would pay or trade something. I told him he could borrow mine, but he would have to flow test them for me. He flow tested them and said that they all flowed right around 420cc.


    • #3
      I can only tell you:

      1. That the people who have flowed them in the past had them come back 420cc.

      2. Judging by the k value adjustments I made when putting them in place of stock injectors, the ones I had were easily over 420 at stock fuel pressure. Maybe someone should call JWT and ask? Ken(450rwhp) and Tempastasz(480rwhp) both used these injectors at 58psi with Z32 pumps, so even if the flow rating is less they can still provide more fuel than most people will ever need, right?

      3. A guy at BZF was running them on a stock ECU with the fuel pressure cranked down below 20PSI and the car still ran PIG rich (tons of black smoke). That would be about 300cc/min at that pressure if they were 420's, meaning he's getting 40cc's more than stock and explaining the extreme loss of power he was experiencing. If they were 380's then 20psi would make them 280, and would 20PSI explain it running THAT rich? Stock injectors will flow 280 with just a few more psi, and never run that rich.

      edit: 4. also note this link 2+2 turdo pointed out also has incorrect information:

      we can't trust the internet... wow.


      • #4
        There is alot of debate about the flow ratings of the benz injectors. I will give you my perspective on my benz "420cc" injectors. I pulled them literally from a 1975 450SE, not SEL. I dynoed 398RWHP 404RWTQ and when under full boost on my SDS it said about 85% duty cycle. However, remember i am at 6K feet elevation and my numbers are corrected on the DYNOJET. In all reality i looked at the uncorrected numbers and they were only like 345RWHP or so, and my duty cycle was showing 85%. If you look at the dyno i was like 13.5:1 on spool up and slowly richened up as RPM's went up to 11:1 at my 6300RPM redline. So take it for what its worth considering in uncorrected numbers i was only 350RWHP with 85% duty cycle with those air fuels. I really dont know but my guess is that they are around 410cc/min at 37psi stock pressure.... so basically 420cc/min. Me and my bud have seen alot of benz with these injectors at junkyards before and he has sold a few sets on our forum for like $150 a set. They are in many years, like 71-75 and in the SE and SEL. They are not that rare really. I see a set every month or two in the yards.


        • #5
          I flowed a set of OE replacements from Borg Warner. 43psi at 100% duty cycle and they were closer to 480cc.

          The difference in size probably has to do with the mfg. They were flowed and found to be within 1% of each other when new.