Continuing ignition timing debate from the 416 thread.

[TT5.9mag]

So, realistically how much power are we talking about for the investment? 1% 2% ?

I'm not saying it's not worth it but it definitely feels like "the little things" chasing a fully optimized timing curve.

I do understand the idea behind achieving a steady state before a result is realized, but how does that translate to real world, where steady state is purely academic?

I do have some experience dyno testing. Back in the day I was on a formula SAE student team, and we flogged the hell out of a cbr600 engine, "optimizing" all these things. That engine would sit pinned at 10,000 rpm while we tinkered with timing and AF.

You know what? We ended up having to make massive changes to the map to make the thing drivable. It didn't make as much power in the dyno, but it sure was easier to drive.

Im not arguing against the general theme here. It is interesting. But I can't help thinking it's all a bit academic.

Don't all the serious race teams tune based on load profiles that mimic specific tracks?

I look at it like this, instead of thinking about how much power was gained by accessing the 1-2-3%, what happens at peak torque on something with a very narrow tuning window (pump gas, boost, cast iron heads for example) and you’re 1-2-3% wrong in the other direction? That goes badly very quick and it pays to get it right.

 

[273]

I look at it like this, instead of thinking about how much power was gained by accessing the 1-2-3%, what happens at peak torque on something with a very narrow tuning window (pump gas, boost, cast iron heads for example) and you’re 1-2-3% wrong in the other direction? That goes badly very quick and it pays to get it right.

I think the point is how much is this really applicable to the average gear head ?

 

[Mean416]

I think the point is how much is this really applicable to the average gear head ?

Actually to me I don't see how steady state tuning is of value except for steady state applications i.e. boats and industrial applications.

 

[Newbomb Turk]

Actually to me I don't see how steady state tuning is of value except for steady state applications i.e. boats and industrial applications.

You’re certainly not alone in that thinking for sure.

It’s about finding MBT, which is Minimum spark advance for Best Torque. It’s like guys want to use the maximum timing they can, even if it doesn’t make more power.

I hate to keep harping on it but Steve Morris is bad about that. In a different video I didn’t post he took four degrees of timing out (thats across the whole curve and not specifically in one rpm range) and it didn’t lose ANY power.

I would have take four more out until it lost power and then went back up a couple and tuned from there. But he didn’t. He never does. Also, like I said he was moving the whole curve down four degrees. We don’t know (and neither does he) if the whole curve needed to be four degrees slower or if it wanted four less at peak torque and maybe it wanted two more at peak power.

You have no idea doing sweep tests if the engine wants the whole curve moved up or down or parts of the curve moved up or down.

If you do a steady state test at 2500, 3500, 4500, 5500, and 6500 for example you can load the engine at that rpm and add or reduce timing at that rpm at that load and you can easily find MBT right there.

Then you move to the next rpm and do it again. And so on. When you get done you will know what MBT is at those points in the rpm curve. Then you have to have them skill (mostly patience really) to stand at the distributor machine and make the curve in the distributor match the curve the engine wants. Of course, if you have a programmable digital ignition (I’m telling anyone and everyone who doesn’t have an ignition or who wants to upgrade to not buy an ignition that isn't programmable) you can easily go into the software and ride the dots to get what you want.

Then you do sweep tests and now when you think the engine wants more or less timing you can just move the whole curve because the curve is the curve. It doesn’t change.

How do you determine MBT doing sweeps? I know I don’t know how.

You can run FAR more compression than most people think IF you put a curve in the distributor, and it’s not even close.

And for the guys who street drive or turn circles (really even for drag cars that don’t use a power glide) drivability is paramount. So 1 or 2 percent may seem marginal but you can’t test actual drivability on a dyno. The proof is in the driving.

So Im all ears for someone to explain how you can find MBT doing a sweep test. If you can it would save me a ton of time because doing steady state testing take a ton of time.

Or someone needs to explain to me why not tuning for MBT makes more power, drives better or doesnt matter.

 

[Newbomb Turk]

I think the point is how much is this really applicable to the average gear head ?

It should be unacceptable to every gear head to spend money for tuning and the end up with a miserable driving piece of ****.

90% of the nasty driving junk cars out there are that way because the tuning is wrong. But you can’t say something or someone is wrong because hate.

It’s stupid this has been taken to this level. You have guys arguing who have never tried to do their testing any other way so they have no idea what they are talking about.

That includes Steve Morris. So far, no one has said they’ve watched the video I posted and that they agree with him and why on his spark advance theory.

I’ll say it. He’s ******* dead wrong. He’s not my God. He puts his pants on the same way as everyone else.

If you (you in the general sense not you personally because the Karen’s ore Karen’s) think his theory is correct then that means you think that Chrysler, GM and Ford are stupid for decades of using vacuum advance for more power and fuel efficiency and low load, high vacuum driving.

They aren’t stupid. They have physics on their side. Unless of course the physics change when the engine is considered a “race” engine. Of course, how the engine knows it’s a “race” engine knows what it is.

 

[Mattax]

I look at it like this, instead of thinking about how much power was gained by accessing the 1-2-3%, what happens at peak torque on something with a very narrow tuning window (pump gas, boost, cast iron heads for example) and you’re 1-2-3% wrong in the other direction? That goes badly very quick and it pays to get it right.

That's one of the things that can be trial tested on a more modern desktop dyno simulation. I posted an example using Dynomation 5 and I'm sure the newer versions can do it at least as well. I forget which cam was in the examples but IIRC the window narrows significantly above 2000 or 2500 or so.

One condition unknown in at least that simulation is temperature of the cylinder walls. A 1/4 mile car can run more timing and gain a little. An endurance racer running fully heat soaked needs to run a little less. Anyone asking why is forgetting why the flame is lit off early in first place.

edit: added link

 

[TT5.9mag]

Actually to me I don't see how steady state tuning is of value except for steady state applications i.e. boats and industrial applications.

I do because the common way of thinking, “get the timing all in early” or “lock it out” is costing not only power but engines. Sure there are applications where it won’t make any difference to get the timing right at peak torque, but there are far more where it will make a difference.

 

[Mean416]

I'm specifically only talking about the steady state tuning. How is it applicable to a dynamic acceleration? It seems like you should give the engine what it wants during the transient, not steady state

 

[TT5.9mag]

I'm specifically only talking about the steady state tuning. How is it applicable to a dynamic acceleration? It seems like you should give the engine what it wants during the transient, not steady state

How do you know what the engine wants for timing at a specific rpm (4500 for example) vs any other rpm (3100 for example) if you don’t park it there and test? Sure you can ball park and ramp the timing through that range but how do you know you’re giving the engine “what it wants”? How do you quantify it?

 

[Newbomb Turk]

As TT5.9mag is saying, how do you get a curve on a new engine?

Guess? Use a curve you think worked on a similar build?

Without steady state testing you don’t know what the engine wants.

And the steady state MBT will show up in a sweep test.

All you are doing in steady state is testing at specific rpm to find what the engine wants at that rpm under load.

It certainly translates from steady state to sweep tests.

 

[B3422w5]

Be really curious to see what somebody like PRH thinks of this topic

 

[TT5.9mag]

Be really curious to see what somebody like PRH thinks of this topic

Tag him.

@PRH

 

[273]

I imagine if you want to an engine probably benefit some by having each cylinder have it's own curve.

 

[Newbomb Turk]

I imagine if you want to an engine probably benefit some by having each cylinder have it's own curve.

And you can do that.

The issue becomes the time and the hardware to accurately sort that out.

I forget the name of the channel but it’s Ben Strader’s channel.

He did at least a couple of videos on in cylinder pressure testing or some form of cylinder measurement.

What they learned gained a fair amount of power on a very well tuned engine.

I actually looked into the sensor and related hardware and software and it was far too expensive for my customers.

It’s hard enough to get them to pay for two days on the dyno and the 300 bucks I charge to make the curve in the distributor match the curve the engine wants.

It’s all about money and time. I can do steady state testing and fit the curve to the distributor and that’s more than many dyno shops do, and I watch as many videos as I can find.

I’m not saying they don’t test for MBT but if they do they don’t show it.

 

[TT5.9mag]

I forget the name of the channel but it’s Ben Strader’s channel

Efi university

EFI University
Website


EFI University
You tube

 

[Mean416]

How do you know what the engine wants for timing at a specific rpm (4500 for example) vs any other rpm (3100 for example) if you don’t park it there and test? Sure you can ball park and ramp the timing through that range but how do you know you’re giving the engine “what it wants”? How do you quantify it?

Legit questions, but either way what it wants steady state must be different from normal accel sweep. I'm pretty sure that's accurate...?

One example is accel enrichment. You have to have it for transient changes. The engine needs that extra fuel to go from a steady state idle to a higher idle.

 

[Mattax]

One example is accel enrichment. You have to have it for transient changes. The engine needs that extra fuel to go from a steady state idle to a higher idle.

Not really.
An engine should go from 600 to 1400 rpm without enrichment.
Pump shot is needed only when the throttle position changes rapidly. It shows as a blip on WBO2.
Enrichment is needed for full load.

 

[Mean416]

Not really.
An engine should go from 600 to 1400 rpm without enrichment.
Pump shot is needed only when the throttle position changes rapidly. It shows as a blip on WBO2.
Enrichment is needed for full load.

Thanks for the correction. I'm not an expert in tuning. Just an engineer with a solid grasp of fundamentals.

 

[92b]

The reason why I say you can’t do that with a sweep test is how do you decide where to put the timing at what rpm?

You have no reference.

How I do it is my reference is the first sweep.

The reason why I say you can’t do that with a sweep test is how do you decide where to put the timing at what rpm?

I do it the same way you do it on a sweep

 

[Mattax]

"The accelerator pump shot is meant to replace fuel that condensates on the walls of the manifold runners etc when the vacuum drops with throttle opening."
- Bruce "Shrinker" Robertson 08-17-2008 Innovate Motorsports forum

Lets break this down.
High vaccum or low pressure will cause vaporization or partial vaporization of a liquid.
If everything else remains the same, opening the throttle moves the pressure in the intake closer to atmopheric pressure.

When the throttle is opened slow enough, the increased area of the transfer slot opening beneath the throttle, coupled with the decreased transfer slot opening above the throttle provides enough additional fuel droplets to compensate for the additional air into the cylinder as well as fuel that is condensing onto the walls.

But the low speed circuit can not respond quickly to quick changes in throttle opening. Therefore we use a mechanical pump to immediately supply additional liquid fuel until the circuits catch up. This is generally less needed less on the main circuits.

Also I'm sure you've seen or read of engines with poor slow idle vacuum that cracking the throttle increases the vacuum. And other engines can be very lopey and the film on the wall may grow and shrink in various locations. My only point being there physics is the same but what it does can vary.

That's probably enough to mull on for now.

 

[92b]

I look at it like this, instead of thinking about how much power was gained by accessing the 1-2-3%, what happens at peak torque on something with a very narrow tuning window (pump gas, boost, cast iron heads for example) and you’re 1-2-3% wrong in the other direction? That goes badly very quick and it pays to get it right.

I don't think anyone is suggesting that you should intentionally over time an engine. But rather you may give up a tiny percentage by having it under timed in an area. To avoid the exta cost of building a custom curve for that tiny percentage left on the table. Not saying that is how I would do it for myself but for some of my customers that is the option they would choose.

 

[Newbomb Turk]

How I do it is my reference is the first sweep.

I do it the same way you do it on a sweep

Ok, so you use your best guess to get a starting curve. I can get close doing that, but it will still not be what it really wants for MBT.

How do you determine what your next move is if you say raise the curve and it makes more power at peak but loses power at and around peak torque?

 

[92b]

Actually to me I don't see how steady state tuning is of value except for steady state applications i.e. boats and industrial applications.

I generally agree with that but there will always be some exceptions. This is also what super flow said in the paper that turk posted.

 

[Newbomb Turk]

I don't this anyone is suggesting that you should intentionally over time an engine. But rather you may give up a tiny percentage by having it under timed in an area. To avoid the exte cost of building a custom curve for that tiny percentage left on the table. Not saying that is how I would do it for myself but for some of my customers that is the option they would choose.

Average power is what moves the car. In your 602 crate engine example that tiny percentage can be the difference between qualifying for the A main and coming through the heats.

Plus, you cant account for drivability on the dyno. Bill Jenkins called it the “nebulous factor” in his book.

And the issue isnt being under timed in an area, it’s being over timed in an area.

 

[Newbomb Turk]

Legit questions, but either way what it wants steady state must be different from normal accel sweep. I'm pretty sure that's accurate...?

One example is accel enrichment. You have to have it for transient changes. The engine needs that extra fuel to go from a steady state idle to a higher idle.

It is not different from steady state to sweep testing.

Doing a steady state test allows the tuner to get MBT (which is overlooked by many evidently) at any rpm you decide to test.

It is uncanny that 50 years after Jenkins wrote his book, his published data about timing curves and advance degrees per 1k is about spot on.

That is because the physic haven’t changed.

That means that locked out timing or all in timing below peak torque are fighting against physics. That also means that a curve that is outside what Jenkins published is also incorrect, with exceptions where mixture motion is so high the burn rate doesnt slow down after peak VE. And those heads and engines are very rare.

What I do know and can say is the two guys that taught me how to develop a curve have spent their lifetimes doing it. One was for a huge company. And he told me personally that outside of emissions requirements and things like that, so in other words when power is the goal the published Jenkins advance is where the curve will likely fall.

I suppose if you made some pulls with the timing locked out you could see the peaks and put a curve in the distributor that uses the Jenkins math and you’d be pretty close.

Like I posted before, how many guys would end up with a curve that needed 25 initial at 1k and 34 total at 6500? That’s what a 505 hp 395 inch iron headed small block wanted.

I don’t remember how much power it lost with the timing locked out at 26, 28 and 30 but it wasn’t 5 or 10.

Plus, the way the car drives is amazing.