Why does my redtop idle and accelerate so much better at 20 deg. BTDC than 15 BTDC?

[DORIMON]

So I have just finished my 2nd redtop in my S14 and now I'm just troubleshooting the timing. This motor came with an auto tps, so I had to change that with my old motor's manual tps, I adjusted the voltage perfectly on that according to the S14 SR FSM. This redtop came with Platinum NGK PFR6B-9 spark plugs, which I have gapped to .028 and decided to test the motor out with on stock boost (7psi) until my BKR7E's come in. After the motor went in, the car started up on the 1st try and idled suprisingly smooth. I checked the timing (with the engine warm, fans off, TPS harness disconnected, revved up a few times then using an inductive timing gun) and it was around 20 degrees BTDC. It idled around 1000 rpms and I took it for a very short drive and I noticed the car seemed ridiculously fast for 7 psi, I thought it was my newly installed exedy flywheel that made a big difference. Then, I adjusted the timing to 15 degrees BTDC and I noticed the car's idle was slightly rougher and the idle had dropped about 300 rpms which I raised back up to 1000 rpms using the adjustment screw. I took it out for a drive and noticed acceleration was ok, but it didn't pull as hard as 20 degrees BTDC did. It also would have a little backfire after going WOT. I didn't have any backfire (or pinging/knocking) at 20 degrees BTDC. So, right now I've left it at 15 degrees BTDC, but I would love to set it back to 20 where it ran so much smoother. I don't want to ask what is the safest I can advance the timing to because that answer varies. I would just like to get some feedback from what you guys think about this. Thanks.

[sr240mike]

I've noticed that when I set timing to 15 degrees at 800 rpm it will be at 20 degress at 1000 rpm. Since you are running low boost a few degrees of advance will make more power, but that can be dangerous with more boost.

[DORIMON]

I've noticed that when I set timing to 15 degrees at 800 rpm it will be at 20 degress at 1000 rpm. Since you are running low boost a few degrees of advance will make more power, but that can be dangerous with more boost.So your saying with the different rpms it will be a different timing? Like if you set it to 15 degrees and then set the idle to 800 rpms, and then drive the car, but later raise the idle to 1000 rpms with the idle adjustment screw, the timing would be up to 20? If so, now it makes me think. Maybe tomorrow I should mess around a little more with the idle adjustment screw while I adjust the timing. When you set your timing, how closed is your idle adjustment screw turned? I think I'll redo my timing with different adjustments on the idle screw, for example, before I set it to 15 degrees, I'll see if I can turn the idle screw all the way down (closed) which will lower the rpms and then see if its possible to turn the CAS more or less to get it to 15. Like, if the screw was almost fully opened, wouldn't the CAS setting for 15 degrees be in a different bolting position as opposed to the screw almost fully closed? The idle raises and lowers as you advance and retard the CAS, so is there a specific adjustment on the idle screw to properly check timing?

[skatanic28]

im not sure if its similar to the ka at all, but anyways....
i believe on the ka you have to unplug the tps and then set it at 700 rpm. then you can time it from there. at different rpm's the ecu will give and pull timing, so maybe that is whats throwing it off? check the sr fsm, maybe they show ya in there?

[DORIMON]

im not sure if its similar to the ka at all, but anyways....
i believe on the ka you have to unplug the tps and then set it at 700 rpm. then you can time it from there. at different rpm's the ecu will give and pull timing, so maybe that is whats throwing it off? check the sr fsm, maybe they show ya in there?Yea its the same with the SR as for the method, but the location of the cam angle sensor or distributor can vary on when you set the rpm. For example, you say after you unplug the tps, you set it to 700 rpm, but where is the timing at before you set the idle speed? That one factor could vary because idle speed can raise and lower also by advancing or retarding the distributor or CAS. So, I'm curious to where the idle screw and the CAS should be set to before setting the timing. I guess I'll mess around with everything tomorrow. I think I'll see if it makes a big difference of setting the idle after the position of the CAS is in the middle of the adjustment bolts versus setting the idle after the CAS is all the way retarded or advanced between the CAS bolts.