TBI timing advance for max power.

[SkyHighColorado]

Hey there. I got a digital timing light and decided to properly set my timing since I just had the distributer out for the intake manifold gasket. I have a couple questions for people who have experience advancing the timing.

First off I should say what mods I have that effect performance right? Jet stage1 chip, Hypertech coil and cap/rotor, Taylor 8.2mm Thundervolt wires, Autolite iridium xp plugs gapped to .035, flowmaster Y pipe w/ high flow cat. 3" single exhaust with race bullet, Ultimate tbi mods (stock fuel pressure regulator), TB spacer, intake. running on 85 octane (I'm at 6000ft above sea level)

Ok so here goes. I want max performance, but need some help understanding a couple things. My timing when I 1st checked (EST wire disconnected) with my Digital timing light was 13.8* advanced and she was running fine. I reset the timing to 12* advance.

1st question: When I plug the EST wire back in and check timing its way up there way past the marks on the balancer. Is this normal? its running smooth and seems like great performance.

2nd: Can I increase my spark plug gap from .035 to .045? what benefits can I gain from this?

3rd: How can I tell if I advance the timing to much or retard to much? What signs or symptoms am I looking/listening for? I know to listen for knock but I haven't heard any yet while tuning the distributor.

4: if I run 91 octane can I get more power out of her?

5. just school me on everything you know about tuning these engines, I feel like a noob.

 

[SkyHighColorado]

With the wire plugged in my timing gun says its at 20* ish advance?

 

[Ruger_556]

4. No
- The higher the octane number the more compression it will withstand before igniting. Simply put, it's harder to burn. You won't gain anything running it in a stock TBI truck.

I'm sure someone will come along with a better explanation but I wouldn't waste your money.

 

[TylerZ281500]

ok here we go, plugging in your est wire means your advance is working again so you wont read zero or close to that as you should when its disconnected, 91 is useless on stock tbi, spark plug gap no, i tried didnt like it at all stock didnt like it anymore built, id leave it where it is, you dont need the extra thousandths because your heads arent " power plentiful" so to speak. if you advance or retard too much itll run rough, start, rough backfire through the intake or exhjaust, not want to idle and will want to die or choke out. you can tell if your timing is off, start at 0 with your est unplugged, drive it around the block or something, advance it and see how it sounds, youll either hear it even up and sound better or worse drive it around again and see how it feels and reacts to what you just did. people say theres a common amount that tbi trucks like and to an extent thats true, some people have told me to thier experience there tbi truck has liked 10 degrees advanced or so, mine like to be as close to zero as humanly possible, why? i dont really know im not that much of an expert.

you can get spark knock out of mistiming but not a bottom end knock, they do sound different.

you want max out of your truck spend a little bit and build something from scratch, or just redo the top end with a small cam and learn to do some tuning yourself, or hit up one of the guys at gearhead efi for some pointers. that site has been uber useful to me in the past. once you get into tuning possibilites are endless, but in the sense of hotrodding do what you like yanno. if you like building motors build one to swap in in the future while practicing your tuning. thats my 2 cents worth.

 

[SkyHighColorado]

Thanks man, I am not out to waste my money, hence the 85 octane haha. I just want to better understand the engine. How would I know if the knock sensor is detecting detonation and retarding the timing?

 

[SkyHighColorado]

ok here we go, plugging in your est wire means your advance is working again so you wont read zero or close to that as you should when its disconnected, 91 is useless on stock tbi, spark plug gap no, i tried didnt like it at all stock didnt like it anymore built, id leave it where it is, you dont need the extra thousandths because your heads arent " power plentiful" so to speak. if you advance or retard too much itll run rough, start, rough backfire through the intake or exhjaust, not want to idle and will want to die or choke out. you can tell if your timing is off, start at 0 with your est unplugged, drive it around the block or something, advance it and see how it sounds, youll either hear it even up and sound better or worse drive it around again and see how it feels and reacts to what you just did. people say theres a common amount that tbi trucks like and to an extent thats true, some people have told me to thier experience there tbi truck has liked 10 degrees advanced or so, mine like to be as close to zero as humanly possible, why? i dont really know im not that much of an expert.

you can get spark knock out of mistiming but not a bottom end knock, they do sound different.

you want max out of your truck spend a little bit and build something from scratch, or just redo the top end with a small cam and learn to do some tuning yourself, or hit up one of the guys at gearhead efi for some pointers. that site has been uber useful to me in the past. once you get into tuning possibilites are endless, but in the sense of hotrodding do what you like yanno. if you like building motors build one to swap in in the future while practicing your tuning. thats my 2 cents worth.

Thanks for the response I appreciate it. For now I just want to get the most out of my engine as it sits, only other mod I am considering is shorty headers. I have been thinking about picking up a 5.3 or 6.0 and doing a mild build on it, but that's in the future maybe. I see what your talking about with the running rough at idle and what not when I retard it to much it wont start and idles all slow and choppy. It is running great at 12* right now so I think ill keep it there till I get more play time with it and maybe go a little more and test it out. I am interested in how the altitude affects timing I have been reading up on it and apparently it would be normal for my engine to want to run more advanced at the higher altitude. The lowest altitude I take it is around 5000ft and the highest is about 9000ft on roads and 13,000ft on trails (not that often).

 

[someotherguy]

Bumping the base timing AND running higher octane fuel in order to prevent the detonation that advancing the timing causes, MIGHT gain you a small amount of power. You'd really need to drive around with a graphing scanner in order to truly know if you've found the sweet spot. Advancing base timing even a couple degrees while running the 87 octane the engine/tune is designed for, you can get detonation slight enough that you can't hear it (especially if you have loud exhaust) but you better believe the knock sensor heard it (knock counts), and told the PCM to pull back timing (knock retard) - costing you the power you hoped to gain, and more.

Have seen it in action myself on an OTC Genesys with just 2° of advanced base timing on a 1994 TBI 5.7

Factory spec is ZERO on the TBI small block, that's where you should have it set, after warming the engine up fully first.

Richard

 

[TylerZ281500]

shortys can be had cheap the ebay stainless arent all that bad. if your knock isnt working youll know youll have a variance of issues. like rich said factory spec is zero for timing they realllyyyy like to hold colose to that, even with mine build up im not far from that at all. everyones under the impression that hey advance timing is a mod and gains you power well thats not entirely correct, properly setting it to where the engine performs best is key wether that be the standard zero or 4 degrees advanced etc.

 

[SkyHighColorado]

Thanks Rich and Tyler! I drove it today at 12* to work and back and it performed well. I feel like it may not be pulling quite as hard in the higher rpm, but its running very smooth. I think ill set her back to 0* tonight and see how my drive to work is in the morning.

 

[SkyHighColorado]

0* seemed a little sluggish just now and the idle a little more Lopey sounding. I'm going to keep trying different amounts.