Manolis_D

iTrader: (2)

To make a long story short, I wasn't aware until last week that the front hub and pulley are a matched set from the factory. As it turns out, my timing has been about 10* too retarded, for the last year or two. I was having all kinds of problems - torque down low didn't seem right, spool took forever (15psi at near 5000 rpm with a .96 undivided p-trim 60-1), and power wasn't where it should have been either (estimated @ 330rwhp at 15psi boost, stock ports). To top it off, around town mileage never got above about 13mpg, and on the freeway i could only manage ~18.5mpg with careful tuning. At the time I thought the leading plugs were firing 13*btdc with a 15* split at full boost (15psi). As it turns out, they were at 3*btdc and 12*ATDC!

So my question is... how much of an effect would the timing have on these things?

Thanks!
Manolis

PS - I checked timing by marking the pulley with an apex seal at the rear trailing plug hole, and then marking it with the seal at the rear leading plug hole. TDC is between the two marks.

nevarmore

Everything. All of them. You have found the problem.

If the fuel/air charge is not being ignited at the appropriate point then you won't get as much power out of it as you could. You're not getting good milage because you arent making as much power as you can with as little fuel as possible. You're not building boost because that fuel is not being burned completely and isnt making enough pressure (or volume of exhaust gas) to spin the turbine.

setzep

What he said

Hmm.. I think I better check this also!

Wait.. when you can see the apex seal in the middle of trailing 2 plug hole it's exactly TDC?

mwatson184

nah, when the apex is exactly between the rear leading and trailing plugs you are at TDC.

Manolis_D

iTrader: (2)

yup - rear apex seal exactly between the two plug hole centers. I used a dental mirror and a flashlight, marking the crank pulley at both positions. Then i cut a piece of paper so it wrapped around the pulley from one mark to the other. Fold paper in half & make your mark (I checked the marks twice, and the paper measurement about 9x...)

EDIT- forgot to add... i twisted the pulley the way the belts will pull it with the engine running (CCW), then tightened the bolts that hold it to the hub- if you don't do this, your timing could be off up to about 3-4* just from the play between the holes in the pulley and the bolts that hold it to the front hub.

setzep

Wait a minute.... So you found TDC by watching the apex seal in the leading and tailing plug hole? I was just out in the garage and I don't think this will work accurately because different year rotor housings have the plug holes in different spots. My 13b-re has the leading plug hole a little farther down in the rotor housing than a S4 n/a one I have. Both have the tailing plug hole in the same spot.

After dinking around with a few different pulleys, rotor housings, e-shaft and a rotor I found the easiest way to determine if you're close to TDC is by simply looking at the front of your hub. Two bolt holes should be damn near vertical. Take a look at yours at what you think is TDC and if two bolt holes aren't verticle you're TDC mark isn't right.

Or maybe stick a clear hose in one of the #1 spark plug holes and fill the chamber with a liquid and rock the engine back and forth till you find TDC by watching the fluid level go up and down in the clear hose.

Manolis_D

iTrader: (2)

rats, you're right... i'll call mazdatrix again and see if they have an explanation...

I like the idea wih the clear tubing - when I get home again i'll take a look at it.

Henrik

cool, very timely - I just did the same thing myself (the between the
lead/trail plugs) and my "TDC" came out 20deg off from where the
stock pulley would have had it marked. (20 deg retarded). so, I'm very
interested in what you hear from Mazdatrix.

-Henrik

Manolis_D

iTrader: (2)

OK, time to yank the Front hub out again... With the keyway at 9:00 the front rotor is at TDC.

KNONFS

iTrader: (14)

Make sure you MARK it on the hub (i mark the key position on the hub itlsef), that's why I did at least, that way i don't rely on the pulleys at all!

Manolis_D

iTrader: (2)

Another little update... If you buy an SR Motorsports main pulley, chances are you'll grenade your engine Their pulleys do NOT come with a pulley hub, so when you bolt the pulley itself onto the stock hub, the timing marks won't be correct. Their tech guy kept trying to tell me that the pulley only bolts on one way (4 bolt eccentric bolt holes), and that because of this there wasn't a problem... =) The Racing Beat / Mazdatrix Underdrive main pulley replaces the stock front hub, so there are no problems here.

So, I'm just going to get the racing beat pulley, because no matter what I do i'll have to pull the front hub off the e-shaft, and it's not worth my time to jig everything up and mark my pulley correctly when for 65 bucks I can get one that should be perfect right out of the box .