7MGE Better Fuel Economy

[teamdrinkalot]

Has anybody fiddled with the cam timing on a 7mge.
I have and using the existing timing sprockets, I picked up 10% better economy and increased low down power and torque. This took just 30 minutes.

[Cressida91GLX]

care to explain further? what exactly you did and why toyota forgot to fiddle with the timing?

[haison]

Be careful playing with that. If you advance/retard timing too far (can't remember which way) your engine may start detonating at higher revs. Which basically means the fuel/air mixture ignites before the plug sparks purely from compression.

...I think.

[teamdrinkalot]

There are 3 camshaft locating holes in the timing sprocket, it was just a matter of undoing the belt tensioner spring, unbolting the inlet sprocket and relocating to another locating hole. One hole advances the cam by 1/3 of a tooth and the other advances by 2/3. 1/3 is all you want and I think that was the back hole (not 100% sure). I have this 7mge fitted into a Hiace that carries a lot of weight and unfortunately the 7mge is a high rpm power - torque engine and a bit impractical for a work truck. It sure makes light work of overtaking B doubles though.
Advancing the inlet cam gave me more bottom end which is where I need it, and it also gave me better fuel economy. Compression went up a bit but it does not ping. I use premium fuel.

[cambelt]

I have done it before but i cant remember which way does what , I thought retarding the inlet gives better fuel economey but not as much top end power, and advancing gives better low end power with not much difference in fuel consumption.
Dave-

[myne]

I guess you tend to spend most of your time in the low end of the power band.
Reducing the overlap would reduce the amount of unburnt fuel making its way straight out of the exhaust.

[rvrolla]

Is this really safe? Mine pings a little at low RPM when not under much load, could changing the locator position help this at all?

Cheers,

[cambelt]

Its funny you say yours pings a bit under not much load, is it a series 2 mx 83 , For some reason only the series 2 has that pinging problem , i have serviced many that do it and when you back the timing off they have no power when cold,,
Dave

[rvrolla]

Thats exactly it Dave, mine is a Series 2! I have tried backing it off and the pining seems to be worse, and when you do it is a bitch to drive cold!! It's probably just under 10deg at the moment, would it be worth going a little higher?

If the car is at idle or just cruising and i step on it, it clicks really loud, like it knocks for a sec then nothing. Someone mentioned on the Cressida forums that this is normal as the computer adjusts the ignition timing or something? Someone also mentioned it could be sticky valves?

This is not my cressida, (CACressida off thermactor) but it makes the same sound:
http://videos.streetfire.net/Player....9-DFA199D1A18E

[RONA]

Hiace that carries a lot of weight and unfortunately the 7mge is a high rpm power - torque engine

WTF
Interesting idea, I'll wait a few weeks to see if your engine grenades and then consider it

[rvrolla]

I was thinking the same thing

[cambelt]

Try removing the air flow meter cover and richening it up a bit , loosen the screw and let it move 5 or 6 notches(the black disk wheel ) , make sure you mark the original position first tho .
Dave

[rvrolla]

Turn it clockwise or anti?

[cambelt]

I think it anticlockwise , what ever way the spring wants to turn it is richer.
Dave

[rvrolla]

you say open the AFM cover, do you mean the black plastic on top that seems to be sealed?