Bean

iTrader: (1)

Has anyone ever heard of or ever tried advancing their ignition timing on a typical boltons-only SC? like 2-3 degress?

lots of other cars do it, and i was wondering if the SC could benefit from it...

does anyone know if the SC has a knock sensor to retard ignition timing automatically if it senses it?

this is on a non-turbo non-nitrous car... in the other two situations, I would know what to do

awj

There are two knock sensors on the 2JZ-GE. I've been wondering about an advance procedure for most cars - should be about the - same for a while. Mark the distributor, loosen it and turn it? OR....

There are MSD advance kits at Summit, or are cam gears easier?

Bean

iTrader: (1)

cam gears are totally different, that advances and retards cam timing; which has to do with valve opening and closing, not ignition...

i know its pretty easy to advance and retard my ignition; but i was curious how much i could go?

its good to know there are two knock sensors though... i guess i can play some and still be ok

awj

Yea but Bean, the exhaust cam drives the distributor correct? So if you advance the cams, you would in effect advance the distributor all things equal. Or am I incorrect?

MadMaxSC400

Mine is advanced quite a bit, if I remember it goes as high as 10 degrees on the ECU's map. The motor doesn't seem to have any problem with it.

Bean

iTrader: (1)

i think the distributor is driven on its own gear, not on the exhaust cam...

plus with cam gears, you effectively spin the gears, not the cams to advance/retard the timing; those 3 or 4 little screws in the front tighten/loosen the cam gear from its backing so you can adjust its teeth on the timing belt/chain

CmputerWiz

The distributor is driven off of the exhaust cam I believe, I shined a light into the opening when I removed the distributor and could see the teeth on the cam.

As for the cam gears, when you undo the 5 bolts, you then turn the cam itself to retard or advance. The gear itself stays put, teeth are holding the belt tight.

SR

awj

Do you use this method on your set-up Wiz, or do you use the ecu piggy-backs and all for the timing issues?

Bean

iTrader: (1)

ah ok, but i still stand by my statement that advancing or retarding cam timing will have NO effect on ignition timing... they are two totally different parts of the car

i'm gonna try advancing my base timing 3-5 degrees this week and see how it goes

SoCalSC4

Bean: how could that possibly be on a car with a distributor?

If you retard the exhaust cam timing, the valvetrain events occur later relative to the piston being top-dead center... so would the ignition events. All the distributor 'knows' is that the rotor is passing by the contact on the inside of the distributor cap- it doesn't care if you change the effective timing of the events or not. You could compensate for this by re-clocking the distributor slightly.

BTW, I advanced the timing on my otherwise (internally) stock '85 MR2 (4-AGE motor)- made quite a difference in responsiveness.
If you're in a "smog state", you'll want to set the timing back to stock for bi-annual tests- the technicians DO check this, and you WILL fail!

Bean

iTrader: (1)

ok, well if it does that, its the gayest system ever devised, no car that i have EVER seen or heard of being modified has to worry about changing cam timing with ignition timing... they are two totally unrelated parts of the motor

if thats the way it is, then i take my statement back about how well designed the 2jz-ge is... thats a serious design flaw

SoCalSC4

Perhaps I misunderstood your statement: you can change the ignition timing without affecting the cam timing- if you change the camshaft timing, the ignition timing will be affected [if, in fact, the distributor(s) are driven by the camshaft]. Make sense?

As soon as I pick up my 'new' 97 SC400, I will experiment with ignition advance on the V8. I will also be playing with the exhaust & intake systems for a few extra ponies!

If the distributor is driven some other way (crankshaft or auxilliary shaft), or if the car is "distributorless" (coil-on-plug), this does not apply...

hyperopt

Valve timing system and ignition timing system on standard valvetrains (including all Toyota) are inter-related. Both systems are connected directly or indirectly to the crankshaft. A distributorless system behaves in the same way except that rotor and distributor cap is not needed. The design of the system is simple, reliable, and effective and not a design flaw!

Don't be surprise if you don't see any noticable and consistent gain in HP from advancing the timing in engines that have been tuned. You may gain a few here but lose some there. You'll need to more than just advancing the timing (eg. tune the fuel flow rate, injection volume table, ignition timing table, etc...), hence, reprogrammed ECU.

SCV8

One way to re-curve the timing map is to use a resistor in the temp sensor circuit,I've done this on other cars and it's worked out great along with some fussing around with the distributor position.
This however will gain some richness,and most tuning on late model cars involves leaning out the top end,so unless you have some exhaust mods to compensate,it could make it worse on the top.
These are pretty heavy cars,I wouldn't think there would be much to gain from retarding the cams.
I didn't try the resistor trick on my car,got a piggyback ecu instead.

Bean

iTrader: (1)

dunno; picked up some power when i bumped up the timing in my TTZ.. and even overly-tuned Honda VTECs get a small kick when playing with ignition OR cam timing