what does advancing the timing do for your car? I read that alot of people advance their timing to like 6 or 8 degrees on their TBIs....

What exactly does this do and does it necessarily boost the car for better performance or what?


Is this something I should do, would it be good for my car...what can i expect from this...

 

Advancing your timing often gives you a slight increase in mileage and throttle response. TBI swirl port heads by design do not need a lot of initial advance. Going too far can have negative effects. A few degrees advanced from the base 0° can be worthwhile. You will most likely have to upgrade the octane on your fuel selection or pinging may result. This may not be in some peoples budget given the cost of fuel. Also, the factory setting of 0° is a "worst case scenerio" value. This is a safety blanket against the possibility of overheating, bad gas, or a multitude of other factors. Running a high advance out of the factory wouldn't have given the range of protection the general deemed necessary for these motors. The best way to judge what timing is best is to increase it 2° at a time and make a pass down the drag strip. When you reach your fastest ET increase the timing again until you repeat that ET. After that back it off 2° for safety and be on your way. This is the "old school" way of dialing in your initial advance. Fuel injected motors like yours really need the timing to be fully controled in the PROM. Chip tuning is the only way to truly dial in the right timing.

 

no offense but, if you don't understand most of the questions you just asked i wouldn't touch it at all. Anyways just for ****z and giggles and because, the fact that most of us are rule breakers i'll answer some of the questions and try to lead you in the right direction.

Ok well for the first thing people aren't advancing there timing per say. These are efi engines therefore the spark curve is electronically controlled. What they are actually doing is advancing there base timing.

What your timing is, is when your cylinders fire in relation to *s of crankshaft rotation.

By advancing the timing you are making the air to fuel mixture ignite at a different point in your power stroke (different * of crankshaft rotation).

if you don't know what you are doing you can cause catastrophic failure from pre ignition or at least loss of power though which is why i don't recommend this sort of mod to you unless you understand the basics of an engine.

The factory timing spec for my motor is 0*btdc my engine has 140,000 miles on it (1992 305 tbi). Anyways after many miles of wear and graces of engineering your engine could use the extra timing due to the fact that any manufacturer usually leaves a little play in there tuning (air to fuel mixture, fuel pressure, base timing, spark curves whatever).

My motor would have been outran by a gemetro with the factory 0* setting. It was horribly pitiful after i set it back to factory specs. Right after this i readvanced it back to about 10* which is what it likes the best.

To reset your base timing this is what you need to do: Unloosen the grey connecter near your distributor (it is a 1 wire plug) i think it's called the esc or is it est (something like that). Then you need to loosen the distributor hold down bolt. After this you should look at your harmonic dampner behind your bottom most (crankshaft)pulley. You will see an engraved line going from 1 side all the way to the other of the dampner. I recomend marking that line with permenant marker or white paint or something so it is more visible. After doing this you will hook your timing light to your 12volt battery and connect the connecter to #1 spark plug (closest to front of engine on the driverside i beleive if i remeber correctly). What you do is turn the distributor itself until your timing mark aligns with the idicater you wanted (can't go to far in either direction though).

This is just for your future reference if you are insistant on tweaking like i am unfortunately (tweeking things that ought not be tweeked can get expensive) Luckily for me my parents still pay for most of my stuff i'm only 16...

What the timing light does is flash everytime the #1 spark plug gets power to fire. When it flashes you will see the timing mark on your dampner align very close to the timing indicators on top of the dampner (you should anyways). The timing indicaters look like fabricated steel mountains sorta on top of the dampner itself. I beleive factory is set at 0* btdc (before top dead center) which is the highest point on the engines stroke. for these engines that * is the first bottom valley that go's lowest on the timing indicaters.

So if it's never been adjusted by a previous owner your timing mark should align with the first bottom most valley. I think from every peak to valley there is 2* of difference but, don't quote me on it.

Anyways g/l and make sure i'm correct on this stuff before fooling with it (i'm pretty tired right now) and if it's above your head don't mess with it.

 

Shifty- You like to go by ET. IMHO that is wrong, especially on street driven cars, I like to go by trap speed. You can tell if you are overadvanced at higher RPMs that way. You want to time your engine to give the best Trap Speed possible.

 

I don't like to double post but Just FYI, I haven't used a timing light on a TBI engine yet. I just align the mark on the balancer to whatever I want the timing to be, take the cap and rotor off, then adjust the distributer until the two sets of magnetic tips align. The tips on the reluctor and the pickup coil need to be aligned. It will then fire at whatever you have the balancer at. I usually use 6* but have found that my newest engine only likes 30* of advance.

 

I can respect that on the basis that total ET is more influenced by traction and track condition rather than power alone. I think this is what you mean. Trap speed gives you an idea of the total power you are making regardless of driving skill (assuming you can drive straight and shift when you need to).

 

Exactly, with MPH you are negating 60' times, etc. You are basically down to power, drag, gear ratios, and shift points. Also if you have the timing TOO advanced, it won't necessarily show up in ET but will show up in MPH. Also most V8s like a certain amount of over-advance in the mid-range this same over advance limits top-end power. This info is out of a book that is full of tips from old Smokie himself. Hence the top gear timing retard that most drag racers use. Your car may actually accelerate faster with more advance but will have less top-end, that results in quicker ETs and slower Trap speeds, if that makes sense in a way.
Trust me, I think that over-advance at high RPM is part of the contributing factors to the crank breaking in my old 355. The bearings were hammered from detonation pretty bad.

Edit- Shifty, I am not trying to say that your way is off base or doesn't work for you as I could see some ET improvement from higher trap speeds. The aerodynamic bricks that I work with like alot less timing at higher engine speeds often times less than 30* total. But they typically like around 36* @ 3,000. But you know how it goes, two people, with two different methods, and two different opinons.

 

Oh no problem at all. Using trap speed is far better especially if you are a novice driver and can't produce consistant 60' times. Using total ET was just a generic way of making a point. That point did need to be explained more. Gotta keep me on my toes

 

My Camaro is my every day street car, but I will occasionally take it to the strip.. it has 53,000 miles on it. What should i set my base timing to? Should I go by Trap Speed or E/T? How much of an improvement can increasing your base timing make?

 

if it has only 53,000 miles on it i would leave it alone.

My motor has 140.000+ on it and it likes 10* base. The reason being is that i'm sure after 140,000 miles of run time that the chain has stretched slightly and wear is starting to show. It runs fairly good at 6* base to but, it's a little snappier where throttle response is concerned at 10*s.

You could probably get by with upping the timing to 4-6*.

If its running good though my advise is leave it alone (i say this even though i am a diehard tweaker) but, things can happen when you play with things that aught not be played with..........

 

Not enough to quantify a significant change. Since you have an auto I would go between 2° and 6° advanced and leave it be.

 

I loosened the distributor, let the engine warm up, took a quick peek at the timing marks, but I mostly set the base timing by ear. Fully warmed up my rpm's are at 700-750. I may have 4 advanced, may be 6 *shrugs*

 

That isn't a good idea. You can get a timing gun for $20 which will aleviate all doubt.

 

Oh this was with a timing gun hooked up ... but I ended up shooting for 4 or 6 ... and combining it with a nice idle ... and that's how it ended up just right

I got a stock engine.. so it worked just fine

Basically I did a thingy where I looked at the timing light.. 4 .. or 6.. and tried to get it at 700 or 750 at the same time

 

ok forgot to mention one thing .. reason I'm saying 4 or 6 .. is.. I don't remember what I set it at *lol* that's all ... next time I'll try to remember

 

yah i was going to say it's probably not a good idea to go off the tach for your rpms. When i hooked my motor up to an engine analyzer it idled between 700-750 warmed up but, only shows 600-650 on the tach. In other words it's probably best not to judge this way.

 

Which is why I did hmmm kinda .. a combo of both .. *lol* ear and tach ..... my main concern was to get it running without stalling

 

I need to do a search on this forum .. and in my books .. about how much compression a 305 can take .. and still run on 87 gas ... how much advanced timing it can take etc


Wasn't that one one of the original plus things about the Vortecs when they first came out ? Being able to handle higher compression while still running regular pump gas ?