Is there a recommended max timing at lower boost levels?

[bpu699]

Ok, per WSM max timing at 0.8 bar is 16-19 degrees (26 degrees minus retard of 10=16 or so)...

Thats easy to set if you have a programable MSD or MSD/BTM boost retard...

But how critical is the timing at 0.3 bar? 0.5 bar?

The stock system goes to full retard by 5 psi (0.3 bar or so)... IE. over 4000 rpm you have full mechanical advance plus full boost retard....

So...
0.1-0.3 bar (linear decrease in timing from 26 down to 16)
0.4 bar =16 degrees
0.5 bar= 16 degrees
0.6 bar= 16 degrees
0.7 bar= 16 degrees
0.8 bar= 16 degrees
0.9 bar= 16 degrees
1.0 bar= 16 degrees


Tons of threads on here by many folks (Mark, Cole, Alan, etal) on what the timing shouldn't exceed at 0.8-1 bar. This isn't in relation to that...

The question is, what is the max "safe" timing at 0.3 bar?0.5 bar?

Can you run 26 degrees at 0.3 bar? Whats safe at 0.5 bar?

Is there a rule of thumb?

There have been folks running the MSD BTM on here, and I have seen suggestions that you should start at 5 psi and then take out 1.5 psi per lb of boost... (Assume boost line disconnected from distributor, or distributor locked/not working. Mechanical advance on or programmed advance)

That gets you:

10 @idle, 26 at peak boost, and 16 at boost at 0.8bar... Sounds fabulous...

But at 0.3 bar you are at 26 degrees... at 0.5 bar you are at 23 degrees...! Is that ok?

I have plotted the variations 10 different ways...

Any thoughts from folks that have done the MSD AL2 or BTM?

Bo

[Tippy]

I'm probably the worst to give my input on this, but I'm over 30 degrees in the low boost areas on my 3.4 EFI engine tapering to low 20's at 1.4 bar.

This engine started life as a 3.2, so intake and head outflow the 930 bits. May have an impact on final numbers.

[bpu699]

Appreciate the data point...

My 930 had stock timing. I *think* I was having detonation at peak boost... MY car was set for 26 degrees max timing, and I am not sure my boost retard worked reliably... BestI can tell I was running anywhere from 19-23 degrees at peak boost and was getting funny/farting sounds...

Read most everythread I could find on here, and folks seem to all recommend 16 degrees under boost...

Not sure how others run such advanced timing?!

Any data points on whats safe at 0.5 or 0.8 bar?

Installing the MSD BTM tommorrow...

Here are some data points I have found:

*****

This shows the timing that is "stock" vs MSD BTM with what I see others on here running... At 5 PSI the BTM is running 10 degrees more advanced than the stock! At 8 psi its 8.8 degrees.

If you start the boost retard at 3psi, not 5 psi, it shifts the curve. So now its only 5 psi advanced over stock mid boost... but at peak boost, you just lost 3 degrees of timing!

Any setting that gives you 16 degrees at peak boost (0.8), nets a higher advance at lower boost...

Issue? Not?

edit... having problems putting up the spread sheet....

[Porsche 935]

There are a lot of variables. Octane in your area. air- fuel mixture. altitude. Like tippy , I run 21 degrees at 1.63 bar on pump gas but I use water-meth injection. Cheap insurance. Others run a little race gas. More timing, more Power.

[bpu699]

Originally Posted by Porsche 935

There are a lot of variables. Octane in your area. air- fuel mixture. altitude. Like tippy , I run 21 degrees at 1.63 bar on pump gas but I use water-meth injection. Cheap insurance. Others run a little race gas. More timing, more Power.

Makes sense...
I have an AFR in the low 10's at peak boost (sometimes dips lower?)... street gas (premium), increased andial intercooler, SC cams, free flow exhaust...

If you guys are running for example 1.5 bar at 21 degrees... What is your setting at 1 bar? 0.5 bar? Is it half of peak boost timing (21 in your case)? Or just a tad below the 21 degrees?

Does the question make sense?

Do you guys just set timing for peak boost and thats it? Does it not matter what timing is at lower boost levels? Is it a linear relationship?

Just trying to figure out why stock timing at any appreciable boost level is 16 degrees and stays flat...

If you have 21 degrees at 1.5 bar... do you also have 21 degrees at 1 bar? 0.5 bar?

Asked differently...

Is advanced timing at lower boost levels AS RISKY as at higher boost? If 19 degrees is "safe" at 0.8 bar... is 24 degrees SAFE at 0.5 bar?

Asked even differently... to what degree of boost can one run stock max timing? If max with no boost is 29 degrees... at what level of boost does that timing need to be retarded? 2 psi? 5 psi? 7 psi? etc...

I know its all relative, but is there are rule fo thumb or starting point?

Thanks!

[dos531]

Originally Posted by bpu699

Makes sense...
I have an AFR in the low 10's at peak boost (sometimes dips lower?)... street gas (premium), increased andial intercooler, SC cams, free flow exhaust...

If you guys are running for example 1.5 bar at 21 degrees... What is your setting at 1 bar? 0.5 bar? Is it half of peak boost timing (21 in your case)? Or just a tad below the 21 degrees?

Does the question make sense?

Do you guys just set timing for peak boost and thats it? Does it not matter what timing is at lower boost levels? Is it a linear relationship?

Just trying to figure out why stock timing at any appreciable boost level is 16 degrees and stays flat...

If you have 21 degrees at 1.5 bar... do you also have 21 degrees at 1 bar? 0.5 bar?

Asked differently...

Is advanced timing at lower boost levels AS RISKY as at higher boost? If 19 degrees is "safe" at 0.8 bar... is 24 degrees SAFE at 0.5 bar?

Asked even differently... to what degree of boost can one run stock max timing? If max with no boost is 29 degrees... at what level of boost does that timing need to be retarded? 2 psi? 5 psi? 7 psi? etc...

I know its all relative, but is there are rule fo thumb or starting point?

Thanks!

Stock timing is flat because it is an antiquated system and not able to adjust timing vs boost. One of the many benefits of EFI is having proper control of ignition timing. At peak torque around 3-3.5k I have about 18* at 1bar and drops to about 16 at 1.5bar. By redline the timing will advance ~4*. My numbers are very conservative considering I am running water methanol injection and have knock control.

You are correct that you can run more timing when your boost levels are low. At 0.5 bar my timing is around 27. Also remember that more timing doesnt always mean more power, thats where a dyno comes in handy so you can find the optimum timing for the engine.

[xbmwguy]

^^+1. Every motor has a different timing requirement. A dyno is great if not essential if you want safety and power. I too am at 16* at 1.5 bar

[Tippy]

Simple answer is yes, you can run higher timing in lower boost ranges as cylinder pressure is lower.

My ignition map pretty much tapers from say 48 to 50° at higher RPM in the no load range (deceleration or very, very light pedal) down to like low 20's for 1.4 boost.

Of course it's all lower in the lower RPM ranges.

This gives great MPG's and torque during light loads.

I'm pretty aggressive though on timing.

[Tippy]

Originally Posted by xbmwguy

^^+1. Every motor has a different timing requirement. A dyno is great if not essential if you want safety and power. I too am at 16* at 1.5 bar

Aren't you twin plug? If so, that's equal to around 24.

[PcarPhil]

I've been running 22ish at 0.8 bar for a couple years now. IMO part of the key of being able to run advanced timing on these engines is getting the individual cylinder AFRs and CHTs as balanced as possible.

These days I need more fuel at the top end (simplified '87 CIS). Once I get it I'll probably bump up the boost to 1.0 bar and leave things alone.

Tippy I bet your car is loads of fun to drive!

[bpu699]

I am pleasantly surprised at the timing you guys run... 0.8 bar at 22 degrees seems high?

If you go to 1 bar, do you dial it back more?

You guys running 1.5 bar... Wow. Care to list your mods? Must be plentiful .

[mark houghton]

Kids, let me give you something to think about. Bo has opened up the timing question once again and that's cool; lots left to understand and learn.

For those of you that are "old timers" on this forum, let me share a piece of conversation I had with a gone member years ago.....356-930 (Chris, if by chance you're lurking here still, I hope you don't mind). Here's a guy that wasn't afraid of pushing the envelope and was instrumental in getting me to play outside the normal boundaries of timing. Between Chris and David Cole (RIP) we shared a lot.

These cars can handle a lot more timing than one thinks,,,to a point.

http://forums.pelicanparts.com/private.php?do=showpm&pmid=1035315

[John at J&S]

Please excuse the shameless plug, but I make an excellent knock control ignition.

It features individual cylinder knock retard (with knock window), boost retard, rev limiters and more.

It can drive an inductive coil directly, or trigger a BOSCH or MSD CDI.

It even has an option for a second ignition driver for twin plug (two coils).

[dos531]

Originally Posted by John at J&S

Please excuse the shameless plug, but I make an excellent knock control ignition.

It features individual cylinder knock retard (with knock window), boost retard, rev limiters and more.

It can drive an inductive coil directly, or trigger a BOSCH or MSD CDI.

It even has an option for a second ignition driver for twin plug (two coils).

If you guys are still on CIS and distributor, do yourself a favor and get one of his safeguard modules. You can advance your timing on the distributor and use the module to retard it based on boost. I did that before efi and the increase in response out of boost was huge, not to mention the peace of mind from having reliable knock control. Cheap insurance IMO

[Tippy]

Originally Posted by mark houghton

Kids, let me give you something to think about. Bo has opened up the timing question once again and that's cool; lots left to understand and learn.

For those of you that are "old timers" on this forum, let me share a piece of conversation I had with a gone member years ago.....356-930 (Chris, if by chance you're lurking here still, I hope you don't mind). Here's a guy that wasn't afraid of pushing the envelope and was instrumental in getting me to play outside the normal boundaries of timing. Between Chris and David Cole (RIP) we shared a lot.

These cars can handle a lot more timing than one thinks,,,to a point.

http://forums.pelicanparts.com/private.php?do=showpm&pmid=1035315

Mark, link states PM on my phone. Was this supposed to be a thread?

And yes, I ran 30° at 1 bar (don't do this!!!!) for awhile even in 100° weather. That was too much though, and backed it down.

[RarlyL8]

I use the single pot 3.3L Euro ignition distributor at 26° of timing on boost (0.75bar). This works for 89 octane gas in the Alabama summer. Lots of power, mileage, and drivability left on the table with the stock USA curve.

[Tippy]

Originally Posted by RarlyL8

I use the single pot 3.3L Euro ignition distributor at 26° of timing on boost (0.75bar). This works for 89 octane gas in the Alabama summer. Lots of power, mileage, and drivability left on the table with the stock USA curve.

That's good to know and pretty close to what I run too. Luckily, we get 93 octane here.

[RarlyL8]

We have 89/91/93 octane gas everywhere and race fuel in a few locations. I tune for the lowest octane fuel and the most hot/humid temperatures.

[bpu699]

Thanks for the input guys... Folks are posting what timing they run at beak boost... There are tons of threads on that... And I probably read them all until my head hurt... Twice...

What hasn't been hit on, is with a programable system, what setting is safe a lower boost? That's the part I don't get...

If you are running stock, it's easy. Anything past 5psi the system retards 10 degrees so regardless of your settings, you are running a flat timing curve...

If you run 28 peak, you are running 18 under boost... Whether 5 psi, 10 psi, or 15 psi...

But if you can run adjustable timing, what could you run at 5 psi, 10 psi, 15 psi? What do folks with the programable units like the msd al2 run at these boost levels?

Not sure if I am asking the question right...

356-911 was running 28 degrees at 5 psi, 24 at 9 psi, 18 at 12 psi... Using the msd btm...

Is a real 24 degrees at .5 bar ok? Asked another way, at what boost level do you start taking timing away???

Will post some info as soon as I can get the btm to work... Installed it today, and now my ignition won't work. Sigh... More putzing tomorrow...

Thanks all...

[Alan L]

Originally Posted by RarlyL8

I use the single pot 3.3L Euro ignition distributor at 26° of timing on boost (0.75bar). This works for 89 octane gas in the Alabama summer. Lots of power, mileage, and drivability left on the table with the stock USA curve.

I got the same dizzy and timing and I run it up to 1 bar. Nothing fallen to bits. Yet.
Alan