Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Benefits to adjusting timing on EFI engines!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by KRAZIE87K5, Aug 1, 2003.

  1. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

    Joined:
    Feb 23, 2001
    Posts:
    3,369
    Likes Received:
    0
    Location:
    Chicago, IL
    [ QUOTE ]
    Put the timing back to where it says it should be. There is no performance gains in doing that on a EFI motor. The computer will retard the 4 degrees right back out of it. The timing is run as advance as it can be till it gets spark knock and then the ECM retards to just under that point.

    What you are accomplishing is making it harder to start. The 4degrees advance is about perfect to make it start real easy and once the ECM finds it's place it will advance as needed.

    [/ QUOTE ]

    This is a quote from another thread that I had running, but I felt this subject deserved more attention. Grimmy (<font color="red">DISCLAIMER:</font>this is not an attempt to flame Grim by any means) made the comment that adjusting your timing from the recommended 0* yields no performance gains. I disagree. Read below...

    You cannot be serious here. I am tempted to start a new thread! I have ALWAYS advanced timing on EVERY EFI motor I've ever encountered, and have benefitted significantly from these adjustments. You are correct saying that the knock sensor allows the ECM to make its own timing adjustments by cranking the timing out to the edge of knocking and then retard it slightly.

    I cannot claim to know why advancing base timing (with the brown wire disconnected) has an effect on performance, but it DOES! I’ve had trucks that had little to no mid-to-upper end power, but after turning the timing to 11-12* the truck regains A TON of power.

    I am really interested to see where this one goes! Has anyone else out there advanced their base timing and found increased performance as a result?

    PLEASE COMMENT FOLKS! I am excited to hear all the opinions on this one out there! /forums/images/graemlins/grin.gif

    Thanks!

    -Dan
     
  2. ken

    ken 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,244
    Likes Received:
    0
    Location:
    Anaheim, CA
    Yes, it works. On my '88 V30 crewcab I advanced the base timing 4 degrees and it has more power.
     
  3. ji240

    ji240 Registered Member

    Joined:
    Jul 30, 2002
    Posts:
    16
    Likes Received:
    0
    Location:
    East Haddam CT
    There is one thing you are forgetting. There is cam timing and ignition timing. As an engine ages, especially a small block chevy, the timing chain begins to stretch which retards your cam timing. If you then advance the ignition timing you will remedy the loss of power to some degree. This is where I feel the majority of people are saying " if you advance the timing you get more power." It is a bandaid fix but does work to a point.

    If the motor is tight and the timing chain is not stretched I do not agree that you will get any noticable power gain on an EFI motor.

    Just my opinion but something to think about.

    Thanks

    John
     
  4. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

    Joined:
    Feb 23, 2001
    Posts:
    3,369
    Likes Received:
    0
    Location:
    Chicago, IL
    I'd love to do a demo using my Burb. I've got a tight motor that I just installed, and @ 0* the motor is a dawg. This is a '96 engine with Vortec heads, and a L98 roller cam. It should have some pep to it. I've got the timing @ about 12* right now (with more room to go - could probably go to 16* with a strict 93 octane diet) and the motor SCREAMS. Nothing changed except the ign. timing.

    [ QUOTE ]
    If the motor is tight and the timing chain is not stretched I do not agree that you will get any noticable power gain on an EFI motor.

    [/ QUOTE ]

    Not that I am trying to be rude here... but WHY don't you agree? I'd suggest you go try it on your EFI truck, but you have a 78 K5... have you retro'd a EFI setup on that truck?

    Anyone out there actually TRY to bump the timing on their EFI motor before? /forums/images/graemlins/blush.gif

    -Dan
     
  5. ji240

    ji240 Registered Member

    Joined:
    Jul 30, 2002
    Posts:
    16
    Likes Received:
    0
    Location:
    East Haddam CT
    I also own a 1989 GMC Jimmy with an EFI 350. Advanced the timing and no change. 1998 Grand Cherokee 4.0 EFI( no change ). 1993 Toyota pickup 22RE EFI ( no change ). I do own these vehicles and work on them myself as well as repair and test cars for a living. Your vehicle is not stock and may benefit from a timing advance. Not sure. I just put that up as food for thought and not a definitive answer. It is just what I have observed.

    Thanks

    John
     
  6. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    You probably answered your own question.
    [ QUOTE ]
    a strict 93 octane diet

    [/ QUOTE ]

    Cylinder Pressure is the key to power. Advancing ignition timing (to a point) increases optimum cylinder pressure. Higher pressures = higher heat, higher heat will cause pre-ignition if the fuel mixture is not stable. When auto manufacturers design/test/build engines, they ASSume a safe Octane rating (usually 87 or below). With that in mind they build ECM's, distributors, etc to make use of that octane in a realiable AND fuel efficient way (thanks to new emissions standards). By advancing the timing, you will see performance gains (to an extent), but alot depends on the rest of the motor. Stock compression ratio?, stock materials (cast, forged, hyperutecnic pistions)?, stock cam profile?, stock rocker profile?, Octane?, intake mods?, exhaust mods?, etc. They take into account what environments a stock vehicle will see, and then build in a buffer. Right from the factory, most vehicles could gain performance with a tweak or two here and there. That being said, I don't doubt YOU see a gain, especially with higher octane fuel (which won't pre-ignite at the same advance as someone running 87). Crate motors aren't the same as factory spec'd motors either.

    As far as EFI motors, I was pretty sure (not an expert here), that the computer "governed" advance even if base was not exactly "0". No matter what though, maximum advance is governed by the knock sensor (regardless of baseline timing) in an ECM controlled vehicle. Running higher octane will allow the ECM to bump the advance up higher through all RPM's and loads, which will effectively increase performance.
    Run a couple of tanks of 87 through your rig and then take it out for a cruise. You will probably notice a significant loss in power. On that note, a person with a regular distributor (no electronic advance), will not benefit by running higher octane, without resetting the timing and/OR re-setting the advance curve of the distributor (weights, springs, and vacuum advance).

    If you go to one of the EFI boards, I'm sure someone could give you a definitive answer as to what exactly happens when you run advance other than 0 on your ECM controlled motor (keeping in mind it is NOT a stock motor).

    The only thing that makes sense for you is that the stock ECM can only advance the time so far. In a normal engine it can't get it close to the point of pre-ignition, so by starting the timing advanced, you are allowing the total advance to be more........again ask the experts.
     
  7. 6.2Blazer

    6.2Blazer 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    4,675
    Likes Received:
    26
    Location:
    Ohio
    When you add in the fact your engine has Vortec heads and a different cam than it's a whole new ballgame. While a standard TBI engine can "change" timing, it can only change it a relatively small amount........plenty to compensate for most differences in fuel, altitude, load, etc... on the stock engine. But do some modifications to the engine and I don't doubt that bumping up the timing would help, but all it's really doing is putting the timing back into the normal operating range for that particuliar setup.
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    /forums/images/graemlins/thinking.gif

    You aint stock...Are you timming to 89 spec or 96 spec? Are you running 96 EFI or 89 EFI. Your cam grind efeects a lot as well. Not the stock cam.
    Do you have emmisions testing and has it passed?

    Get WINASDL from Economy EFI and see what this thing is doing then contact the guy and let him see your test results.
     
  9. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

    Joined:
    Feb 23, 2001
    Posts:
    3,369
    Likes Received:
    0
    Location:
    Chicago, IL
    I am not timing to any "spec" really... I am timing it based off what it tells me. My expereince says to time it as far out as possible, without loss of power or detonation.

    The TBI is from the 89 Burb, all stock, nothing is changed. Not even the pressure regulator... yet! /forums/images/graemlins/grin.gif

    The cam is a roller cam from an '89 Vette. Not ideal for a 6000 Burban... but its getting the job done for now.

    Emissions testing DOES exist in my area, however, I've only had the truck on the road here for 2 weeks. I won't get the notice for another 3-6 months probably. So I can't say if it will pass. If I had to guess... I would say YES, since the exhaust smells just fine to me. I have smelled failing exhaust before... this is nothing close to that.

    I've got WinALDL software already on my laptop from the K5... now I need to get another cable. /forums/images/graemlins/frown.gif Is WinASDL different from WinALDL, or was that a typo? /forums/images/graemlins/blush.gif

    -Dan
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    [ QUOTE ]
    My expereince says to time it as far out as possible, without loss of power or detonation.

    [/ QUOTE ]

    If the knock sensor is working, the only way you will see detonation is by watching knock counts with a scanner, or looking at winALDL.

    My recollection of ECM's is that the timing is mapped out already from the factory, so the early ECM's couldn't advance timing, they just based the calculation for it on throttle position, engine speed, etc. They retarded it obviously, but to change the timing specs under various conditions, you have to reprogram the PROM.

    I could be wrong on that, but I think only the much newer ECM's of some manufacturers can actually advance or retard timing based on how the fuel is performing...advance it if running 91, retard if running 87 for instance.
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Typo...sorry.

    Yeah I would get that thing data logged. The cam is going to probably change a LOT of things. That's why yours runs better with the timing advanced. What's timing supose to be on the year vett that cam is spec to and what's the compression ratio on the motor that cam matches?

    All that is going to effect timing and the timing curve that cam needs is not going to be anywhere close to what the 89 TBI wants to give it. That cam was matched to the TPI. That cam proably wants a lot more advance then the 89 TBI will give it. That's why advancing made such a difference on YOUR truck. If it were stock it would not have made any noticable change except it would probably make it harder to start.

    On my 88 454 burb I do gain a little power running higher octane because it does start to edge the timing up. It does get better MPG but not enough that I'm willing to feed it higher octane all the time. It goes from 9.79 mpg up to 10.2. Cant justify the extra 10 cents a gallon to gain less the 1/2 a MPG.

    6k....who are you kidding...try 7k buddy! My K5 is well over 6k with trail gear /forums/images/graemlins/rotfl.gif
     
  12. dodgedude99

    dodgedude99 1/2 ton status

    Joined:
    Jul 12, 2003
    Posts:
    784
    Likes Received:
    0
    Location:
    burbia of illinois
    [ QUOTE ]
    I also own a 1989 GMC Jimmy with an EFI 350. Advanced the timing and no change. 1998 Grand Cherokee 4.0 EFI( no change ). 1993 Toyota pickup 22RE EFI ( no change ). I do own these vehicles and work on them myself as well as repair and test cars for a living. Your vehicle is not stock and may benefit from a timing advance. Not sure. I just put that up as food for thought and not a definitive answer. It is just what I have observed.

    Thanks

    John


    [/ QUOTE ]
    you will never see any change in a 94+ chrysler truck by advancing the timing. you could advance it till your blue in the face, the PCM controls all of it, which is why for my Ram i was stuck getting an aftermarket programmer to do it. on the 318/360 dodge motors you can advance the timing by modifying the crank positioner sensor.
     
  13. rick88blaze

    rick88blaze 1/2 ton status

    Joined:
    Jan 24, 2003
    Posts:
    2,342
    Likes Received:
    1
    Location:
    Knob Noster, Mo.
    i've ran my '88 K5 at 8* ever since i've owned it. i tried bringing it back down to 0* and it took away alot of power. i brought it back up to 8 and it runs awesome. and i pass emissions here in vegas with flying colors. by the way, my engine only has about 30K miles on it.
     
  14. crazykev4x4

    crazykev4x4 1/2 ton status

    Joined:
    Jun 30, 2003
    Posts:
    430
    Likes Received:
    0
    Location:
    Watertown,Wisconsin
    are u running premium fuel?
     
  15. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

    Joined:
    Feb 23, 2001
    Posts:
    3,369
    Likes Received:
    0
    Location:
    Chicago, IL
    Right now I've got 87 in her. I have in the past used 93... but I know better than to set timing on 93, and then switch back to low grade 87. As a matter of fact, the tank thats in there now I got at the local 7-11 store! /forums/images/graemlins/blush.gif

    -Dan
     
  16. rick88blaze

    rick88blaze 1/2 ton status

    Joined:
    Jan 24, 2003
    Posts:
    2,342
    Likes Received:
    1
    Location:
    Knob Noster, Mo.
    i run straight 87 octane. with some injector cleaner about every other month. if i'm gassing up to go wheeling then i'll either put mid grade or a big can of octane boost in it.
     
  17. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

    Joined:
    Feb 23, 2001
    Posts:
    3,369
    Likes Received:
    0
    Location:
    Chicago, IL
  18. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    Here's my 2 cents /forums/images/graemlins/laugh.gif
    I run my 89 TBI at 4-6 degrees advance. Has better usable power there than at 0. I have had it as high as 8 degrees. It ran real good but the fuel mileage fell off a little so I went back to 4-6. I am more into fuel milage than performance. I get 18 to 20 on the highway depending how fast I drive.
    I think the stock ECM only has around 28 degrees total timing advance written into it. So adding advance to the base timing will give you more total advance.
    I have a scanner and have monitered the knock sensor readings and mine does not ping with advance up to 8 degrees.
    I live at 5000 ft ele and run 89 octaine gas my cam, heads, and manifold are stock.
    I have also advanced the timing on some other TBI trucks with good results.
    I built a TBI engine for a buddy for his K2500. Put on better heads and Edl manifold and mild cam. It runs real good at 6 advance degrees with the stock chip.
    Advancing the timing on TBI engines has always produced more power for me.
    My Mustang has a MPFI system. Advancing the timing 6 degrees on it really made it come alive. Bumping up the timing on EFI Mustangs is pretty much the standard practice for performance. Some people can run as much as 20 degrees base timing with no ill effects.
     
  19. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    I would think that if you set it to say 8*, and the computer sets it back to zero, it is loosing that 8* of range, so that's just 8* that it cant retard your timing and that's why you're making more power.

    If your knock sensor retards the timing, how far does it go? In the past, I had ESC, and I remember it backing off my timing up to like 20*!! Reducing the capability for the computer to retard your timing may be the reason that it's acting like that.

    I dunno though just my theory on the whole thing.
     
  20. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    Basicly thats how it works. The ECM does not know what the base timing is set at. It is pre programed with a set timing curve and uses it no matter what the base timing is. The ECM cannot change base timing. It always assumes it is set at 0
    So setting the base timing at 8 BTDC gives you = +8 deg all through the timing curve letting you get to full advance faster and giving you more total advance. 28 + 8= 36 total advance which, as you know is good for making power.
    The only thing that can have a major effect on the timing is the knock sensor picking up pre detonation. If the ECM sees knocking it reduces advance in 4* incriments till it goes away. If it doesn't go away at a pre programed setting it throws the trouble code.
    As long as the ECM sees no knocking it will make no changes in the pre set timing curve.
    There are other factors that affect timing such as speed, rpm, vacume and EGR position. but these usually only come into play at cruise speeds for better fuel economy and emissions.Because at cruise it usually runs full advance Running too much base timing may give a knock at cruise speeds. Causing the ECM to reduce timing. So if you advance the timing its best to check it out at cruise speeds to make sure there is no knocking.
    If you are going to mess with the timing it is best to move it in 2 degree incriments till you are are comfortable with the performance and get no per-detonation.. Its also nice to have a scanner to monitor the knock sensor to see what its doing. it will also show you how much advance the ECM is giving the engine. But you have to add degrees for how far the base timing is advanced off 0.
    This is how I understand it works. And it works for me.
     

Share This Page