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    Help Analyzing S52 Dyno Graph

    To start, this is the 2nd iteration of tuning for my s52. I'm curious why there is a dip in the graph at 5,500 RPM and never returns to full power. Is this is tune issue, a system issue (Vanos, exhaust), or possibly a resonance issue?? Most of the other graphs I have seen for s52's with similar modifications seem to be linear to redline. We also played around with the intake filter and inlet conditions with minimal changes.

    Mods during dyno session are as follows:
    -s52 converted to OBDI
    -413 red ECU with custom chip by a knowledgable tuner
    -Stock s52 cams
    -24lb injectors
    -3.5" euro MAF
    -M50 intake manifold
    -Raceland headers to OBD II midpipe and supersprint exhaust
    -Rogue engineering pulleys
    -Rebuilt Vanos with Beisan's seal kit

    Graph is below and noted that AFR's are not shown, but my wideband read high 11's to low 12's until redline.

    Performed on a DYNOmite dyno

    1991 Alpine S52 318is
    Instagram:
    https://instagram.com/saltybeast/
    Build Thread:
    http://www.r3vlimited.com/board/showthread.php?t=210734

    #2
    I have no expierence with s52's on dynos but as i recall it's somewhat based on a M52. The M52 engine family has peak HP at 5500rpm and peak torque at 3500 to 4000rpm. But considering the S52 is labelled at 240HP on Wikipedia something seems to be way off.

    These Modification you've already done sound really promising for power and torque gains.

    was the ecu tuned on the dyno? what fuel are you running? is the pump sufficent?

    also i've never heard of a 20HP loss (compared to the 240HP claims on wikipedia) because of exhaust resonance issues either. Maybe you loose some on the way to the rear wheels.

    Comment


      #3
      Is that whp or calculated crank hp? Or from hubs?

      But can't tell anything without proper logs from the ecu during that dyno pull. And don't even know if you can get those from obd1 ecu. Original obd2 ecu of s52 would be much easier to get logs.

      Comment


        #4
        That's a huge loss up top. I'd pretty much discount anything to do with the exhaust system.

        1) Fuel delivery rate: Do you have any reason to suspect that your fuel pump even if it's new isn't delivering adequate flow? If not, check system pressure under load.
        2) MAF: Do you have a known-genuine Bosch 803 Euro HFM? Is the tune for the 803 and not 800 540i HFM?
        3) Did you break the VANOS in (i.e. drive around and activate it multiple times) before heading to the dyno

        Originally posted by whysimon
        WTF is hello Kitty (I'm 28 with no kids and I don't have cable)

        Comment


          #5
          Cam timing could be way off too.

          That should be closer to 250whp, no?
          Build thread

          Bimmerlabs

          Comment


            #6
            Without AFR's, or knowing what tune you have, the evidence isn't much better than the client that calls my shop and says "my car is making a tick-tick sound, what is it?" lol


            We need more info.

            EDIT: Just noticed you said AFR's are high 11 to low 12, that's actually horrible for an NA car. Will upload a pic of the engine I explained below which is actualloy running a fair bit rich since I prefer to leave it that way for long-track road racing cars.



            Originally posted by sebe20 View Post
            But considering the S52 is labelled at 240HP on Wikipedia something seems to be way off.

            240bhp, not whp.



            Originally posted by nando View Post
            Cam timing could be way off too.

            That should be closer to 250whp, no?

            I stuck a stock s52 on the dyno and it made 217.



            I just did a rebuild on an s50 last week that I used 11.5:1 86.5mm pistons, s52 crank and +1 intake valves, it made 255whp and 248wtq, with torque going over 200 starting at 2500rpm and peaking at 4800. HP was pretty flat at 250+ from 5500 to just under 7k (stock cams). Basically it's an s52 with 11.5:1 compression and s50 cams (very comparable to s52 cams).
            john@m20guru.com
            Links:
            Transaction feedback: Here, here and here. Thanks :D

            Comment


              #7
              right, stock would be around 215whp - but I think he'd be closer to 250 with those mods if it were running right, which it definitely isn't.

              Who's the knowledgeable tuner? 11-12:1 afr is way too rich, but I don't think that explains the big power drop off.
              Build thread

              Bimmerlabs

              Comment


                #8
                The red line is first pull with only 21.5lb injectors added. Blue line is after I trimmed the fueling. It would have made more power if the right of the AFR graph was at stoich at the rev limiter, but as I said, I like to run the road racing cars a little richer than for all out power.

                You should keep the AFR's on the mid to high 13's with a little dip at peak torque. Timing on most 24's I have tuned didn't gain MBT after 27, but this one actually kept gaining torque until 33, but left it at 30 peak.

                You don't need a 3.5" MAF. They don't make more power than a 3". An LS1 has a 75mm MAF (2.9") and makes power well into the 400's. Your engine is restricted at the valves. Even a BBTB doesn't show peak power gain, just a tiny bump in the curve at throttle opening/transitions, naturally, as it "gulps" a little more air earlier than a stock TB. Having a MAF larger than the throttle opening is moot.
                Attached Files
                john@m20guru.com
                Links:
                Transaction feedback: Here, here and here. Thanks :D

                Comment


                  #9
                  AFR is not the problem, though there really is no need to be running that rich (11s). The difference in power/torque between .9 lambda (lbt for most engines) and .7 lambda is only about 3-4%. Most fuels these days are E10 with a a stoich AFR of around 14.08 so .9 lambda would be around 12.6, depending on how your wideband is calibrated. If you are making more power with AFRs closer to stoich then your o2 sensor is probably reading incorrectly, you'll never make peak power at stoich on regular pump fuel.

                  I'd guess knock sensor noise/spark retard or a cam timing issue.

                  Comment


                    #10
                    Originally posted by R3VM3UP View Post
                    AFR is not the problem, though there really is no need to be running that rich (11s). The difference in power/torque between .9 lambda (lbt for most engines) and .7 lambda is only about 3-4%. Most fuels these days are E10 with a a stoich AFR of around 14.08 so .9 lambda would be around 12.6, depending on how your wideband is calibrated. If you are making more power with AFRs closer to stoich then your o2 sensor is probably reading incorrectly, you'll never make peak power at stoich on regular pump fuel.

                    I'd guess knock sensor noise/spark retard or a cam timing issue.

                    The dyno graph I posted says otherwise. Look at the power difference when leaning it from 11 to 12.5 at 5500rpm. ;) In your thinking I went from ~.75 to .85 lambda at 5500 RPM, which is 10% difference from lambda. In most of the formats I have tuned, 10% adding/subtracting fuel is a BIG difference specially when OBD1 scales fuel at 0-255 as it's binary hex.
                    john@m20guru.com
                    Links:
                    Transaction feedback: Here, here and here. Thanks :D

                    Comment


                      #11
                      All the discussions of power and no indication of the ignition timing? Isn't ignition tining where you make power? For all we know he's 10deg more retarded than he could be.

                      Comment


                        #12
                        at 11:1 pump fuel hardly even burns. We're not talking about E85 here.

                        But I still think it's only part of the story. Need more info from the OP though.
                        Build thread

                        Bimmerlabs

                        Comment


                          #13
                          Originally posted by nando View Post
                          at 11:1 pump fuel hardly even burns. We're not talking about E85 here.

                          But I still think it's only part of the story. Need more info from the OP though.

                          On some cars. GM tends to like mid-high 12's with fast burn chambers, but are also knock-prone with much ignition.




                          ...and agree with you. The curve itself looks normal up until the bump in the graph. BMW liked to pull extra timing and add more fuel than it needed ate MBT. It's very apparent in the m20. BUT also the VANOS could be causing an issue, either in hard/software, maybe both?



                          Originally posted by e30davie View Post
                          All the discussions of power and no indication of the ignition timing? Isn't ignition tining where you make power? For all we know he's 10deg more retarded than he could be.



                          ...or 10 too much! :/




                          Also interested in who is tuning it, and if it's live, or via mail etc.
                          john@m20guru.com
                          Links:
                          Transaction feedback: Here, here and here. Thanks :D

                          Comment


                            #14
                            ^i lost like 10hp on the dyno going *3 more advanced from where it likes it.

                            Comment


                              #15
                              Originally posted by pazi88 View Post
                              Is that whp or calculated crank hp? Or from hubs?

                              But can't tell anything without proper logs from the ecu during that dyno pull. And don't even know if you can get those from obd1 ecu. Original obd2 ecu of s52 would be much easier to get logs.
                              This is from the hubs. The dyno reads about 10% low from what I was told, but still seems pretty low for the mods. I would love to data log if I kept the setup OBDII, but hindsight is 20/20.

                              1991 Alpine S52 318is
                              Instagram:
                              https://instagram.com/saltybeast/
                              Build Thread:
                              http://www.r3vlimited.com/board/showthread.php?t=210734

                              Comment

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