When setting the timing, unplug the brown connector and set timing to zero. Is there any advantage of advancing the base timing setting or should it be set to zero as indicated by the manual.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Setting Timing 1990 k5
- Thread starter Justin Fleming
- Start date
Burbdood 74
Giver of not a single damn...
I run my Suburban at 4* BTDC with no pinging or harm done so far. It's got a pinch more giddyup but I'm not sure if it's real or I just *think* it does.
Only advantage is as said already. Too much and you'll start hitting the knock sensor and lose power. Pretty intolerant of large additions of timing, 2* increments seem to be about right to try. Not many seem to be able to get much more than 4* over base without having issues.
4xcrazy
3/4 ton status
I always figured since the computer controls the timing anyways, what does it matter if you try to advance it any, the computer would just take over and either retard it back to where it needs to be, or naturally advance it, whatever it needs to make it run within spec.
I always just run mine at the factory setting 0*.
I always just run mine at the factory setting 0*.
because the computer assumes 0 so if you bump the 0 to say 8 it will add eight to the full curve. If it pings it will pull it all but if you stay out of knock it will add a little power. My 90 ran better at +8 and would get 18+ on a regular basis.
That's not how timing works in these setups. Timing is essentially fixed. Here is an example of a timing map (RPM is left, MAP kPa is top):
Really dumbing it down to say that main map there ("advance vs RPM vs MAP") is all there is, but that's the basis of everything the ECM does in relation to timing...it's all based off of that timing map. Everything is based off of those numbers. At 90kPa and 4800 RPM, the setup above will always be working off 22.85* of timing, same for every "cell" there.
The PROM "thinks" it has 0* of base timing (which is what stock is for most of our stuff that I'm aware of, thus why the core support stickers spec 0*, because that is how the PROM is setup). Therefore, 22.85* is 22.85* in the above map. If you advance the distributor physically, and base timing is now 10*, you end up with 32.85* at 4800RPM and 90kPa. But that is a global change (like increasing fuel pressure) and you've now increased timing 10* across that whole map. Might work ok in some spots, and not at all in others.
You may hit the knock sensor, but you don't want to be bouncing off the knock sensor...the problem starts before the knock sensor starts retarding timing. The fact that you can add some base timing on the stock setups means GM was conservative, but they were conservative for a reason...that leaves a margin of error for things like varying fuel pressure, varying fuel quality, etc.
Again, there is a lot more to it than that, but in general...
Really dumbing it down to say that main map there ("advance vs RPM vs MAP") is all there is, but that's the basis of everything the ECM does in relation to timing...it's all based off of that timing map. Everything is based off of those numbers. At 90kPa and 4800 RPM, the setup above will always be working off 22.85* of timing, same for every "cell" there.
The PROM "thinks" it has 0* of base timing (which is what stock is for most of our stuff that I'm aware of, thus why the core support stickers spec 0*, because that is how the PROM is setup). Therefore, 22.85* is 22.85* in the above map. If you advance the distributor physically, and base timing is now 10*, you end up with 32.85* at 4800RPM and 90kPa. But that is a global change (like increasing fuel pressure) and you've now increased timing 10* across that whole map. Might work ok in some spots, and not at all in others.
You may hit the knock sensor, but you don't want to be bouncing off the knock sensor...the problem starts before the knock sensor starts retarding timing. The fact that you can add some base timing on the stock setups means GM was conservative, but they were conservative for a reason...that leaves a margin of error for things like varying fuel pressure, varying fuel quality, etc.
Again, there is a lot more to it than that, but in general...
454Sub
5/8 ton status
My 90 454 runs 8*. Never pings and runs good, I run premium in it though as a safety net, but it will run on regular if you drive it correctly.
454/7.4L Initial (Base) timing is 4* (3.87) so your only adding 4.
so bare with me here.... I am assuming the timing tab is the original....starting at the right end there is the sight tube which I beelive is for a dealer ship type probe then you have the saw tooth cut valleys and peaks. Where is zero as I can not read the tab and what direction would be advanced towards the site tube or away from the tube....
thanks
thanks
How's this?
I can not open the photo...
I think that's because your not on paid membership...
chulisohombre
1/2 ton status
Turn dizzy counter clockwise to advance. Timing should move left I believe on the tab. It's been awhile. If you take a base reading first and see where it's at now. Then turn distributor slightly cc and shoot it again.
