Well i think i am finally ready to tune my first car. I am in the process of doing a engine swap into a RX-5 Cosmo and the customer asked me if i would tune it. I feel that i have a decent grasp on A/F ratio at different load points but the timing seems to be a very touchy subject. Here is a run down of what i think the timing should be doing. If i am off please help me out, i want to learn!!!!


High vacuum (decel)- fairly high amount of advance, maybe something in the 35-40 degree range?

Idle- 10 degrees 25 degrees depending on what the motor wants and how the motor is ported?

Idle to 0 PSI- slowly advance the timing till it peaks around 30-35 degrees?

0 to 10 PSI- Slowly taper off from 30 degrees to around 20 degrees by 10 PSI?

10 to 15 PSI- taper from 20 degrees to 15 degrees by 15 PSI?

15 to 20 PSI- taper from 15 degrees to 10 degrees by 20 PSI?

This is on a stock port 13BT with a T70 turbo running 93 octane.


I think i also have a pretty good grip on the effects of trailing split. From what i understand "MOST" people like 6-8 degrees at idle and low load and slowly increase the split until about 12 degrees at medium to high boost. Several people seem to like 0 degrees split but i think that is a bit rich for my blood.



Any input would be greatly appreciated. Please don't flame anyone if their views are different than yours. There is always more than one way to skin a cat.

He has a WB02 and an EGT in the car. Is there anything i should look for in those two gauges while adjusting the timing?


I envisioned the timing map looking something like this.



By allenrx3 at 2007-08-02

 

id like to hear a little knowledge about this also.
ill have a wideband and a dual EGT gauge fomr pineapple racing.

 

Anyone???

 

I'm running way more advance at idle....~40 degrees.

thats the extent of my tuning knowledge

 

Thanks for your input. Every little bit helps.

 

anyone ever start with hitmans timing maps?? are those "safe" enough for a good boosted run? i KNOW every car is different but even the best tuners have to start with some sort of "safe" timing map right!

 

i ran a hitman base map and had no problems boosting.


i turned afr's via wideband and haven't touched timing yet

 

You don't feel there is any more power to be had by optimizing the timing?

 

good to know!!
how long you been boosting on his timing MAP?

 

oh there most defenitely is! although im not running anytime of auxillary injection yet and dont feel the need to run agressive timing yet. i dont feel comfortable quite yet to do this myself. steve kan is coming out my way again though and am thinking about having him tune my car.

 

about 10,000 miles

 

thanks for the quick reply.
how much boost? have an est. of how much HP your pushing and how much more you think it has?

 

about 300-315 at 10 psi. dave at speed machine performance thinks 400 at 15-18psi. we'll see ill have it on the dyno here soon.

im sure theres at like 30 rwhp from timing but i want longevity and am just scared to run agressive timing with no injection on pump ya know?

 

^Bump^ would like to know more about this too...

 

If you are looking for more info on fine tuning ignition under boost then do a search for EGT tuning on top of AF tuning. Timing effects EGT more than air/fuel adjustment. You could be running 11:1 af at 7k at 15psi and have a huge range in EGT soly based on ignition timing. Keet egt at a set value at about 1450 +/- degrees F and you'll get a pretty good timing tune. Try to adjust the ignition timing to change EGT.

It sounds odd but you advance timing to cool off EGT and retard timing to heat it up. You really need to do a search but basically it has to do with the completness of combustion. The trade-off is increased motor heat (water/oil) leaning tward detonation with advanced timing, OR increased EGT causing other hazards like preignition from overlap and overheated exhaust from timing retardation. The tough part is finding the happy medium.

And then theres ignition split to add to the equation..

 

Wait a sec.. are you wanting to know about lead advance or trail-split?

B

 

id like to know about both!!!
LOL

 

I think i got the effects of split down. It is leading timing i am more concerned about.