MSD BTM /w JWT ECU

[S13FX]

Is it even worth getting a MSD BTM /w a JWT ECU, since JWT retards the timing so much, or should I just use my SAFC to fine tune A/F r's?

[Craving4Boost]

you dont need a btm, you should even ADVANCE your timing since its so conservative. but at least your safe right? yeah the JWT isnt perfect so if you already have a safc then go ahead and use it to fix your idle or crusing AFR's and such if there needs to be any

[4felix20]

i have an MSD 6BTM for sale if you're set on going that route. selling it for around 280$ but i'm open to offers..

i used it with my safc2 and it was awesome. at 13psi on my T3 super 60 it was great. i LOVED it. i ended up dusting almost every car i went up against..even my neighbors corvette with some sort of 'chip'.

[S13FX]

Ok so I did it again I posted my question with out doing my homework heh sorry. So today I have spend my whole day learning and reserching how to tune your car, and I found out that with playing with your AFR's you retard or advance timing too.

So I guess my question is. Is that the reason why JWT programd ECU's are so retarted on timing hehe :-p cause they make them run so rich for safety? And also if I plan on doing my own tuning with a wide band, and a safc, I shouldnt really have to spend the 500 dollars to get a JWT tune ecu. Especialy if I only plan On running about 10psi, 370cc, and a z32 maf?

[DRIFTEADOR]

yes, they need a safety margin to make up for things like available octane (some states only get 89) and difference between engine setups. no two motors are the same.

if you're going to be dyno tuning the car, a jwt ecu, imo, would be a waste, but you're going to need something more than just a afc hack. you'll need something to control timing, too.

[S13FX]

well since Im only going to run 10psi for now, can't I simply just retard my distirbutor by 5 degrees, I have a SOHC, in that case that would put me at 10. Im going with the .5 for every pound of boost suggextion.

Here is a question, So I know I can retard my timing by turning my distributor counter clockwise and advance it by turning it clockwise. Lets say I did get something to control my timing. Does that mean the device or ecu turns the dostributor for me? or is there another way that happens?

[DRIFTEADOR]

you can but it will hurt pre-boost power unnecessarily. i don't know what the recommended timing retard is now but last time i was here everyone seemed to suggest .75-1 degree for every psi after 7, iirc.

electronic timing control, like a btm, controls timing at the ecu. this is the better way since you can retard timing only where its needed. when you clock the distributor you're adjusting the base timing which affects the entire rpm band. thats where the computer starts adding/retarding from. for instance, lets say your base timing at the dist is set at 20btdc and youre idling with a ecu advance of another 20 btdc, you have a total of 40 degrees advance. when you turn the dist forward 10 degrees, you still have the same 20 degrees advance of the ecu, but only 10 base timing for a total of 30 degrees btdc.

[S13FX]

Ahhh I get it wow that's rly simple heh... So what I found out today about playing with your AFRS retards or advances your timing is true. So basicly since a SOHC timing is set at 15. Running at 10psi I shouldnt even worry about touching my base timing, just make sure I set my AFR's correctly and I should be good to go. For future refrence though whats the timing set in the ecu for a KA24E?

Wow man thx a lot for showing me the light heh.

[DRIFTEADOR]

eh, it gets a little more complicated

piggyback fuel controllers allow the use of bigger injectors by modifing the MAF signal to the ecu. basically it tricks your ecu into thinking there is less airflow so it will inject less fuel and the motor won't flood. this is supposed to be a stock ka timing map (notice the load axis is converted to manifold pressure instead of mass airflow):

you can see that the lower the load (flow/pressure) the more timing advance the ecu adds. well, since the afc tricks the ecu to thinking there's less airflow, it's at the same time telling it to add more timing.

[S13FX]

ahh I see wut your saying so basicly it's just takin a short cut, and takin short cuts is not a good idea, especialy if u plan on boosting more then 10psi. So my question still stands, what is the base timing set on the ECU? and what do u recomend on controling it with? And if I do get something to control my timing electronicly should I still leave my Base timing at 15 or retard as necesary? I guess Im just trying to find the best setting for my set up right now, Untill I rebuild the engine next summer.

[DRIFTEADOR]

heres the pic, i had to wait until i was back at the work computer to post it (credit to I believe devious for the pic)



thats what i meant by its more complicated, it's not just one number. it changes depending on load and rpm. the top row, 100kpa= wide open throttle in a n/a motor, while the bottom row would be in full vacumm.

[S13FX]

oh man you right and I bet, all those change big time once you start boosting and changing afrs. It looks simple enuf to do if I had everything else to look at like with an emanage which after this whole post I think Im going to have to consider lol. I think Iv gotten drawn into a new hobby.

[hannibal]

i don't know what the recommended timing retard is now but last time i was here everyone seemed to suggest .75-1 degree for every psi after 7, iirc.

I think the recommendation is "after 7psi, retard .75-1 degree for each psi of boost". So at 10psi, you retard 7.5-10 degrees, not just ~3degrees.

I explicitly asked this question cause Ive heard it said both ways

[S13FX]

whoa that would put me at a base of 5 to 6.5 deg on my base timing that seems kind off heh.

[DRIFTEADOR]

thats how i've understood it to work too but here, people say 7psi is fine on stock timing. why then the big jump from 0 timing retard @ 7psi to 8 degrees retard for a 1 psi difference? doesnt make a lot of sense, .75, or even .5 per pound of boost starting from 1psi sounds more logical to me. timing should be fairly linear.

hey fiz, wanna share a screenshot of your map

[hannibal]

^ Good points about the big juimp in timing retard. I could be wrong, but I know Ive heard that answer from someone.

Maybe somebody will clear this up.

[DRIFTEADOR]

probably from enthalpy on fa

one of the things that people miss most about making basemaps and tuning cars is the linearity of the system. if you have big bumps or changes in your maps you are doing something wrong. the engine is a remarkably linear device. evene when you include turbocharging...values should always be smooth for both fuel and ignition.