Timing Query

[InlineUK]

Hello Guys,
I have a timing question for all your turbo guys and gals; how much initial and mech advance do you run with boost? How much do you retard under boost?

In my experience i managed to completely over look timing when planning my motor. I've now found out i need to retard timing under boost. A couple of guys i've spoken too have recommended locking out my dizzy and just running max timing and a boost retard unit.

I was told something like 36-40* initial and retard it back to 26-28* under full boost. Does that sound too much initial? Searching the forum i see some people running a max of 28*.

Any help is much apprieciated!

Nathan

 

[kirkallen143]

It will depend on what your motor likes from the start. First off I would start low and then work your way up on the timing. Start like at 20* total timing under boost and go from there. Then you can gradually increase the timing once you get it running under load and watching out for denotation.

Mine is a Duraspark II, I have base timing set at 15* and only get 10* of mechanical advance for a total of 25*. I welded the advance slot in the distributor to only give me 10* of advance. It works well for me, even with only 25* cruising the highways (it could be better with more timing, but I cannot afford a BTM now).

You could use a BTM like some do, that way you can get your timing up for daily driving and cruising the highways, and once under boost the BTM will pull timing out to stop denotation.

http://store.summitracing.com/partdetai ... toview=sku

Kirk[/img]

 

[addo]

What about (instead!) an ignition driver and CAS?

 

[Bort62]

I locked out my dist to only give 10* mech. That combined w/ 15* initial gives me 25 total.

 

[InlineUK]

Hi guys,

I plan to use one of these MSD 6BTM boxes.
http://store.summitracing.com/partdetai ... toview=sku

This will allow me to retard the timing with ref to boost.

Looking at your answers you guys seam to run about 25* total with no retard. So if i can run say 30-35* total and then retard 1* per lb of boost, when i hit max boost at 10psi i'll have retarded back to 20-25*.

I know this will need tuning once its setup, but initially i just need to get a rough idea.

 

[Does10s]

That'll work other than it may be hard to start if you have the dizzy locked at 30-35*.
If you did the 10* sweep method, set the dizzy up to around 20-25* initial, then pull some out with the BTM.
Personally I like it up around 28* total, but it'll be dependent upon the fuel used, and the motor itself. (Cam timing, compressoin etc)

We'll be testing this method this Sat. on Kelly's car. Just swapped the dizzy last night back to our old modified one.
So we'll see how that goes.
Will

 

[kirkallen143]

You know if you do set/run your intial timing high and it is hard to start, you can always use the white wire off of the module to retard timing while you are cranking the engine on a DSII system. That is what it is intended for, and if you play your cards right, you could hook it up to a hobbs switch and use it to retard you timing. Although you would not have any adjustability like the BTM, but it would/could work.

Addo, what is an ignition driver and CAS? And how would that work? Curious, I am.

Thank you sir.

Kirk

 

[InlineUK]

Hi Will,
Sorry i'm a little confused by what you mean when you say the "10* sweep method"; are you referring to limiting the dizzy to 10* mech advance? Then have 20-25* initial and then retard using the btm under boost?
Thanks

 

[Does10s]

Hi Will,
Sorry i'm a little confused by what you mean when you say the "10* sweep method"; are you referring to limiting the dizzy to 10* mech advance? Then have 20-25* initial and then retard using the btm under boost?
Thanks

Exactly!

I've done the 10* adv. sweep before without a BTM and I just set it up like KirkAllen stated above. Worked fine. Don't even bother to hook up the vac. adv.
With the BTM you can really put the timing in there for cruise power and fuel economy, then yank it out in a controlled manner, via the box, when the loud pedal is pushed!
Enjoy!
Will

 

[InlineUK]

Excellent, thanks!

 

[addo]

Kirk - I was meaning a Crank Angle Sensor arrangement , like the square-toothed steel or iron disc you see on many newer cars butting against the damper rear. They have a missing "tooth" which signifies TDC. The sensor proper, is a little coil wrapped around a magnet and encased in epoxy; it's bracketed off the block or timing cover to fit a hair's breadth away from the disc.

Each tooth on the disc creates a pulse via the sensor, as it spins past; the sensor is hooked up to a small computer that then considers RPM, if it's changing, and other peripheral input such as a knock sensor and the reading from an MAP or MAF sensor. It then makes the judgement call on when to fire the spark relative to TDC. Getting a signal back from the knock sensor causes it to reduce the advance until that response drops away.

It's really half an EFI system, and in fact an aftermarket computer can be used just to drive the ignition. Sometimes it seems odd to me when we buy a "standalone" unit that is no longer standalone in certain situations - in fact, requiring an intermediary box that is another cost, yet maybe doesn't offer the same degree of overall control that may be obtained otherwise...

 

[kirkallen143]

Thanks for the insite Addo. You mean something like this, huh...


http://store.summitracing.com/partdetai ... toview=sku

 

[addo]

That sort of thing, yep.