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  • Question about timing...

    I have an 88t ecu (which are supposed to run more timing under boost), a t3 stock boost, and an NA block.

    So let me get this straight...

    To get more power (to a certain extent of course), you advance the timing to a higher BTDC, right?

    BUT, I'm looking to keep it from detonating on 87 octane, so I need to retard the timing to a lower number, right?

    My hood says it should be 20 BTDC. My parts car said 15 btdc for a manual transmission, but i don't know what car that hood came off of, it's not original. The books I have (haynes/chilton, i even checked the 88 fsm found nothing) don't give stock numbers, just say to look at the hood sticker
    A gentlemen on Zchat last night suggested I use something around 17. What do you suggest? I know all engines are different, but what would be a good concervative number? It's frigid here today, so I want to be plenty concervative so it won't detonate on a 99 degree day next summer...

    I'm a bit confused on this and will be warming up the car and setting timing as soon as i get this ghetto exhaust on. Sorry for the newbish question, but I don't want to screw this one up...
    My beloved Z:1987 2+2 NA2T w/30a swap.
    My black sheep: 88ss parts car (pretty much stripped and gone)
    207k miles and counting. Turbo'd since 155k.

  • #2
    Stock timing on a 88t manual is 10 degrees. Since you have higher compression and youre running low octane fuel I would suggest leaving it at 10. You may even need to go lower. As far as finding the best setting for your car it's going to be trial and error or take it to the dyno. Your main concern is avoiding detonation so make sure you have some way to monitor it.

    Comment


    • #3
      wow, only 10 degrees, eh?

      The engine is an 87na auto, so it should be at like 20 right now.

      I have no availible dyno, and I have an untrained ear for it, so I'm looking for a concervative number to start with.
      My beloved Z:1987 2+2 NA2T w/30a swap.
      My black sheep: 88ss parts car (pretty much stripped and gone)
      207k miles and counting. Turbo'd since 155k.

      Comment


      • #4
        Dang, 87 octane... Isn't that just asking for Detonation?

        Or are you intercooled? Maybe I just don't understand why you want to run 87

        Terrible idea putting those wheels on...

        Comment


        • #5
          no IC. I was hoping to be able to run 87 to save money. I will probably run 91 premium in the summer or anytime i plan to do any kind of spirited driving. Tonight i ran 7psi up to about 4,000rpm and noticed not detonation, but held it breifly, only a few seconds of boost. I need to get the brakes bled better and the steering aligned before i do anything else.

          But MAN what a ride. I about shat myself when i put it in fifth and rolled on throttle at 2 grand to watch it spool... and what a noise, you've gotta love those sounds...

          on a side note, the clutch is very light. I've only driven a stock z31 clutch once for a test drive, but the SBC/DXD stage 1 clutch is very light. Almost like my mother's Accord...
          My beloved Z:1987 2+2 NA2T w/30a swap.
          My black sheep: 88ss parts car (pretty much stripped and gone)
          207k miles and counting. Turbo'd since 155k.

          Comment


          • #6
            I ran my car @ 30BTDC in the HOT weather. Bet you could hack 87 at 10 BTDC

            Terrible idea putting those wheels on...

            Comment


            • #7
              Keep in mind 10 degrees on an 88t ecu is not the same as 10 degrees on an 88na, 84t, or some other year/aspiration ecu. The timing value we are refering to is really only the set idle timing for each of the ecus and varies between ecu types. When you set the timing you are really only calibrating the distributor position relative to the crank based on the idle timing for that particular ecu. In the case of an 88t ecu the stock idle timing is 10 degrees so you would use your timing light to adjust the distributor until the timing reads 10 degrees at idle because thats what the ecu is spitting out. An 84t ecu might have an idle timing of 20 degrees. In this case you would want to set the distributor to 20 degrees because thats what the 84t ecu is spitting out. In both cases the distributor will end up in the same spot because all you are doing is calibrating it ot the crank.

              What's important to you is not the actual idle timing value (10, 15, 20) but rather how far from the stock value for that ecu you have the distributor set. Lets say an 88t and 84t ecu had the same timing maps but different idle timing. The 88t ecu would read 10 degrees at idle and the 84t ecu would read 20 degrees at idle but timing values when you are not idling would be exactly the same because you are using hte same ignition maps. However if you were to use the 84t ecu and set the distributor to 10 degrees at idle even though the ecu is spitting out 20 degrees you would effectively retard the entire ignition map by 10 degrees across the board.

              So about the 88t ecu. The stock idle timing for the 88t is 10. If you set the distributor so it reads 10 degrees at idle you are basically setting it to the stock timing for an 88t engine. If you set it to 20 degrees you will actually be running 10 degrees advanced timing to the stock map. This could be dangerous considering youre running higher compression, more boost, and lower octane than the ecu was originally tuned for. That's why I suggest running 10 degrees or less unless you have some way to monitor things to make sure you are still safe.


              Sorry to confuse anyone or try to teach anyone something they already know. I just want to make sure people understand that comparing timing values between different ecus is like comparing apples to oranges.

              Comment


              • #8
                Stinky wrote: Keep in mind 10 degrees on an 88t ecu is not the same as 10 degrees on an 88na, 84t, or some other year/aspiration ecu. The timing value we are refering to is really only the set idle timing for each of the ecus and varies between ecu types. When you set the timing you are really only calibrating the distributor position relative to the crank based on the idle timing for that particular ecu. In the case of an 88t ecu the stock idle timing is 10 degrees so you would use your timing light to adjust the distributor until the timing reads 10 degrees at idle because thats what the ecu is spitting out. An 84t ecu might have an idle timing of 20 degrees. In this case you would want to set the distributor to 20 degrees because thats what the 84t ecu is spitting out. In both cases the distributor will end up in the same spot because all you are doing is calibrating it ot the crank.

                What's important to you is not the actual idle timing value (10, 15, 20) but rather how far from the stock value for that ecu you have the distributor set. Lets say an 88t and 84t ecu had the same timing maps but different idle timing. The 88t ecu would read 10 degrees at idle and the 84t ecu would read 20 degrees at idle but timing values when you are not idling would be exactly the same because you are using hte same ignition maps. However if you were to use the 84t ecu and set the distributor to 10 degrees at idle even though the ecu is spitting out 20 degrees you would effectively retard the entire ignition map by 10 degrees across the board.

                So about the 88t ecu. The stock idle timing for the 88t is 10. If you set the distributor so it reads 10 degrees at idle you are basically setting it to the stock timing for an 88t engine. If you set it to 20 degrees you will actually be running 10 degrees advanced timing to the stock map. This could be dangerous considering youre running higher compression, more boost, and lower octane than the ecu was originally tuned for. That's why I suggest running 10 degrees or less unless you have some way to monitor things to make sure you are still safe.


                Sorry to confuse anyone or try to teach anyone something they already know. I just want to make sure people understand that comparing timing values between different ecus is like comparing apples to oranges.
                . . . end rant. :wink:
                [strike:ff0tp92h]1984 300ZXT[/strike:ff0tp92h]
                [strike:ff0tp92h]1986 300ZX 2x2 NA2T[/strike:ff0tp92h]
                2000 Porsche Boxster
                2007 Toyota Yaris

                Comment


                • #9
                  Thank you for the information.

                  I have my timing set at ~9 degrees and I haven't yet noticed any detonation. I'll try to run at least half a tank of premium any time i plan to drive hard, or when weather is hot in the summer. %85 of my driving is to/from work/school/food or whatever were the car barely gets warmed up, and i've already resolved to stay off boost untill it's good and warmed up properly. The car is at an alignment shop now, later today I'll cruise around a bit and test the workmenship before i take the drive back to kearney.
                  My beloved Z:1987 2+2 NA2T w/30a swap.
                  My black sheep: 88ss parts car (pretty much stripped and gone)
                  207k miles and counting. Turbo'd since 155k.

                  Comment


                  • #10
                    I would recomend sucking it up and running the high octane. Just pretend like thats all that available for your car.

                    $2.00 x 19 gallons = $38
                    $2.20 x 19 gallons = $41.80

                    Usually goes up $.10 per grade SO you save about $3.80 every time you fill up, what once a week for daily drivers? Is it really worth chancing that its not going to detonate on the crap fuel for $4????? You save a whopping $200-$250 bucks a year(depending on your gas prices) wooohoooo :roll: you can put that toward your new forged pistons after your stock ones blow up! :lol:
                    85 Z31 6.0 LSX turbo 766whp/792wtq
                    04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                    Comment


                    • #11
                      SATAN wrote: I would recomend sucking it up and running the high octane. Just pretend like thats all that available for your car.
                      ...
                      Is it really worth chancing that its not going to detonate on the crap fuel for $4?????
                      This is probably a lesson best learned from experience. I can say I learned it well and this is 100% sound advice.

                      Comment


                      • #12
                        hm. Okay. That settles it then. From here on out it's premium. I can't get 93 octane around here, just 91 with no ethanol. I've been avoiding ethanol for some time now. I've been rather worried about it, so I'll just run premium and be done with the matter.

                        On a side note, this is probably the fastest car I personally have ever driven. I say that based on the few short test trips I've taken. The 3rd gear power oversteer is new to me. I just got the rear SS sway bar in tonight (i'm s'pose that'll change the balance a bit) and my ghetto exhaust finished up, so I will go out for a test-ride later, after i fuel up with some good stuff. Man what i ride, I can only image what these cars feel like with the kind of go-juice some of you have. Many of you put down double what i've got. Scary to think about :?
                        My beloved Z:1987 2+2 NA2T w/30a swap.
                        My black sheep: 88ss parts car (pretty much stripped and gone)
                        207k miles and counting. Turbo'd since 155k.

                        Comment


                        • #13
                          I agree with you on that

                          Terrible idea putting those wheels on...

                          Comment


                          • #14
                            Az4u2c wrote: hm. Okay. That settles it then. From here on out it's premium. I can't get 93 octane around here, just 91 with no ethanol. I've been avoiding ethanol for some time now. I've been rather worried about it, so I'll just run premium and be done with the matter.

                            On a side note, this is probably the fastest car I personally have ever driven. I say that based on the few short test trips I've taken. The 3rd gear power oversteer is new to me. I just got the rear SS sway bar in tonight (i'm s'pose that'll change the balance a bit) and my ghetto exhaust finished up, so I will go out for a test-ride later, after i fuel up with some good stuff. Man what i ride, I can only image what these cars feel like with the kind of go-juice some of you have. Many of you put down double what i've got. Scary to think about :?


                            Also keep in mind though, just cause you are running better gas doesnt mean you can just be careless about your timing. Higher octane gas creates a slower burn instead of a violent explosion. The explosion part may sound cool, but for making power but it is less controlled and more prone to detonation. That does not mean
                            premium cures detonation. If this were the case there would be no need for race fuels.
                            85 Z31 6.0 LSX turbo 766whp/792wtq
                            04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                            Comment


                            • #15
                              I've retimed it to 10* btdc, and I haven't heard it detonate yet. I haven't been running it all that hard, but i have hit full boost and 5k a couple times on 87 and didn't hear of feel anything out of the ordinary. So I should be okay running premium, I think. I don't plan to go crazy with this thing.
                              My beloved Z:1987 2+2 NA2T w/30a swap.
                              My black sheep: 88ss parts car (pretty much stripped and gone)
                              207k miles and counting. Turbo'd since 155k.

                              Comment

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