ddub

I put on my Racing Beat main underdrive pulley and I had a few questions about timing.

I know that leading is 5º ATDC and trailing is 20º ATDC. Here's the pic of the instructions for the RB pulley.




So RB sets marks for 0º and 10º ATDC but does not have marks for our stock timing. In that pic I have marked a red line in between the 0º and 10º ATDC. Am I right to assume that the timing for leading should just line up in the middle of those two marks RB makes, so where that red line is? Or am I missing something? I set the timing in between those two marks and everything was fine, but it seemed to idle better if I moved it towards the other two marks, which I thought was kind of weird. Just wanted to confirm that I do indeed have the right idea with where timing should be set, thanks.

ddub

Bump back to page 1.

If I get no replies I'm just going to assume I'm right and be on my way.

RotaryResurrection

iTrader: (8)

Stock leading timing (the only one to worry about with stock EFI) is 5* ATDC, and they give you marks for 0* and 10* ATDC. So obviously the correct stock mark should be halfway between those 2. Your stock trailing mark, if you wanted it, would be obtained by taking the distance between 0 and 10 ATDC, and adding that distance past 10 ATDC, and making a mark there, for 20 ATDC.

As for why your car runs better when moving it around, that's advanced timing...making the ignition pick up and fire sooner, closer to TDC. When doing so you gain some top end power but bring yourself closer to the threshold of pinging, and at a certain point you fire too early and can actually creat a conflict where the ignition event occurs too early and tries to push the rotor the wrong way. Those with advanced timing sometimes notice a higher idle and a funny sound during cranking (similar to a high compression piston motor) which is the ignition event interfering with the rotor's momentum.

Think of TDC as the rotor being centered over the plugs, BTDC as the rotor still closing (compressing) in/down towards them, and ATDC as the rotor expanding down/away from the plugs (combusting). By changing the point at which ignition occurs in relation to physical position of the rotor, you can change it's momentum characteristics and thus power. Fire too late, you've lost momemtum and potential power. Fire too early, and you can rob yourself of momentum. Finding the optimum timing gives you the best all around driveability and power. Most people stay stock, but you're okay with about 5-10* of advance in an NA...never advance timing on a turbo motor, that's suicide. Some turbo guys actually retard base timing as a safety net.

BlaCkPlaGUE

While we're on the subject, I thought the haynes and other people here for that matter said that you cannot put a main pully on wrong for the timing, cause it only goes on one way. However, when I took mine off the other day, theres no notch to align the pully, you can put it on 180degrees out of sync, or 90, or whatever! The only thing that lines up are the bolt holes. whats the deal?

RotaryResurrection

iTrader: (8)

The bolt holes are all 4 drilled in different spots...so you can only put them back in one spot. You'll see what I mean when you go to reinstall it. You slide the pulley on, line up one hole, but the other 3 don't line up...keep rotating it until all 4 do, then you're golden. You literally cannot install one the wrong way. You can, however, get your marks moved if you use a pulley plate from a different pulley hub. Always keep the plates and the hub that came together, together. Mixing them up can result in marks moved 20 degrees or more. I can explain why, but I'd rather not, so just trust me on this.

BlaCkPlaGUE

hahahha, damn, I get it now. Thanks my man!
I guess the next time this question gets asked all we have to say is
"when you re-install it, then you'll know"

heh..

thanks man!