A couple basic z31 questions.

[707redz31]

I have a couple questions:

First: I have a 1987 z31 na2t w/ a 1987 na computer w/ the 1987 base image. Should base timing be set at 15` btdc or 20` btdc? Car calls for 20` but in the nistune handbook it says 15` for most cars and in consult with it at operating temp it's showing 15` when trying to idle. What should I be looking at to tell me what base timing to use? I assumed 20` since that's what the car called for.


Second: I've had this car professionally tuned before by a tuner than hasn't done a whole lot of nistune. It had Walbro 255 fuel pump, 553cc injectors, .50 trim t3/t4e, intercooler, ford "other (mustang gt)" maf, and all basic mods (exhaust, boost controller). Car made 273whp/333ft•lbs at 11.5psi and 18` but the tuner said he couldn't advance timing past 18` without slight det. Does this sound like the k value wasn't right? Or maybe load scales are off?
*edit: k value was 200

[unreal-]

I have a couple questions:

First: I have a 1987 z31 na2t w/ a 1987 na computer w/ the 1987 base image. Should base timing be set at 15` btdc or 20` btdc? Car calls for 20` but in the nistune handbook it says 15` for most cars and in consult with it at operating temp it's showing 15` when trying to idle. What should I be looking at to tell me what base timing to use? I assumed 20` since that's what the car called for.


Second: I've had this car professionally tuned before by a tuner than hasn't done a whole lot of nistune. It had Walbro 255 fuel pump, 553cc injectors, .50 trim t3/t4e, intercooler, ford "other (mustang gt)" maf, and all basic mods (exhaust, boost controller). Car made 273whp/333ft•lbs at 11.5psi and 18` but the tuner said he couldn't advance timing past 18` without slight det. Does this sound like the k value wasn't right? Or maybe load scales are off?
*edit: k value was 200

To begin, im not accustomed to the Type 1 or Z31 platform, but if its a nissan, it should be the same so:

1. Whatever it calls for in the FSM is what you run. For example on my KA-T factory calls for 20* Base. The ECU is EXPECTING 20* base so it will read 20* in Consult. As long as the Consult value matches the Physical value on the crank pulley you should be fine.

2. Those are really good numbers for 11psi and the timing is right on the edge of possible det. Im not sure what kind of timing map Z31's run, but in the KA world, its 26-28* at 0 psi, and 1*/psi as you get into boost (for the conservative guys like me) In my case, i am running about 17-18* @ ~9psi, and 19-20* @ 7psi (WG) depending on what column the ECU is interpolating. The K value or load scale would not affect this at all. Its just the maximum that your motor can take, given the boost pressure and timing. Only way you could increase timing above that is to use Meth/Water Injection or higher octane fuel.

[Matt]

Check the factory service manual for the base timing. Usually its measured at 800rpm and normal operating temperature (about 80 degC). That is what the base timing should be on the vehicle

Most ECUs but not all are about 15 BDTC timing

With regards to timing on the dyno, this is only read from the timing map (when off idle)

K constant is your load and fuel multiplier and affects the fueling side of things (not timing)

[707redz31]

Check the factory service manual for the base timing. Usually its measured at 800rpm and normal operating temperature (about 80 degC). That is what the base timing should be on the vehicle

Most ECUs but not all are about 15 BDTC timing

Will check on this. edit: 1987 nonturbo is 20* and 1987 Turbo is 15*. So since the bin is turbo should i use 15* or since the ecu is nonturbo I should use 20*? I guess I just want to know whether to base timing off of the ecu itself or the image on it.

With regards to timing on the dyno, this is only read from the timing map (when off idle)

K constant is your load and fuel multiplier and affects the fueling side of things (not timing)

I understand both of those. I was wondering if the k constant was too low is it possible it would not allow the injectors to work to their potential not allowing more timing or boost? People are usually able to see another 100whp with my same or more conservative setup. Im fairly certain all my engine cooling components are even over sized for the power levels I'm looking to achieve.

[Matt]

Your tuner will be looking at the AFRs. If they are too lean over the whole fuel map, then K is increased. If its only part of the fuel map then the fuel map directly is changed

Sounds like with a turbo image it should be 20 degrees

[707redz31]

Ok, gotcha.