Can we have a real thread about speed density?

[tkelly27]

I have no idea what you guys are talking about, nor do I care, what I want to hear about is people who run speed density personally, what they think about it, how it compares to their old mas system, and how easy it is to tune/reliable.

I run Jackal speed density and I love it. Compared to running tunerpro with a mass air sensor, it lets me tune with values that I can see on my gauges. I mentioned earlier, I don't even use a logger for tuning fuel, it's all just there.

I know I am at Xpsi Yrpm and my afr is Z, I want Z to be Z*1.3, and then change the cell. I know I never go under 20inhg at idle, so everything under that is a 0 pulse width, injectors off engine braking. There is also a soft VE (how much total VE increases/decreases with boost/vacuum), so if I notice I'm rich or lean at a specific boost throughout the RPM, I can just pull a few points from that rather than adjusting the whole row.

My car always starts, and always runs. There are no problems in the 20* winters or 100* summers, I'm not even running the IAT which helps with those. Doesn't care if you have a boost leak, or if you even have the turbo attatched at all. I have no idle gear and it idles fine, all the time, although I do have stock cams and I hear this isn't the case with bigger cams.

There should be no difference in performance between how a car runs with mass air and SD. There is the slight restriction from the MAF (I've measured it, it does exist), and some people notice better throttle response, but with the same fuel for the same amount of air, and the same spark timing, there should be no difference.

 

[tkelly27]

Honestly boost fluctuates much more for a traditionally controlled turbo (MBC) you just don't see it because we use gauge pressure as our measure most of the time and not absolute pressure.

Gauge pressure = absolute - 14.7psi. If it were jumping around in absolute pressure, you would for sure see it jump around in gauge pressure.

As stated before, you can use boost or g/rev to control the torque curve. The speed density system in the 80's turbo dodges have a boost vs. mph curve and a boost vs rpm that keeps the boost low to prevent traction loss and prevent damage to the automatic transmissions, which were not as strong as they should have been from the factory. It works really awesomely. A g/rev and a boost system would have to be tuned to the specific car setup.

Vehicle speed is the better of the two as far as traction is concerned. I don't think the 1g VSS is so hot.

 

[Ludachris]

I was wondering if we could have a thread on here where everyone that uses or would like to switch to speed density could post openly without getting deleted or even banned from talking about link? How does it help the DSM community to delete every post that has anything negative about DSMLink in, alot of people would probably like to know.

We've had a problem with a small group of DSMers who appear to be trolling our site trash-talking DSMlink and their products, leading to DSMlink having to defend themselves and their products publicly - a situation that we would rather not see obviously. If that wasn't an issue, there wouldn't be so many posts being deleted or people getting banned that refuse to follow our site rules. It has nothing to do with DSMlink being a Supporting Vendor, it has to do with our policy against vendor complaints and trolling. The people attempting to discredit others for the sake of causing conflict, personal gain, or just for pure entertainment (as they laugh about it in another forum and insult our site and the people who help run it) are not welcome here. I don't pretend to know all the motives, but it's caused quite a stir and we don't intend to allow it to continue, even if our moderating efforts are criticized as being biased, which is untrue.

Look at some of the LinkBacks down at the bottom of this page and you'll get a better idea of what I'm talking about. If you want to be taken seriously and not seen as a troll on our site, don't go posting BS on another site about "tooners" with disparaging comments about the people who have dedicated years to helping grow this site and the DSM community as a whole. You're only insulting the people who have made the DSM community the great community it is today.

If anyone wants to reply to my post, or has feedback about the way we run this site, send me a PM. Do not reply to this post here in this thread, as it will be deleted. We will do our best to keep this thread on topic and free of trolling. Thanks to all those who have done their best to keep it informative for the community.

 

[the_mork]

Gauge pressure = absolute - 14.7psi. If it were jumping around in absolute pressure, you would for sure see it jump around in gauge pressure.

I know that you are experienced enough to know that this statement isn't true. The boost gauge and the MBC only know what is going on inside of the intercooler pipes. There is no reference to atmosphere. You must have been getting ahead of yourself with that part. When it comes to air entering the engine it is pressure in absolute that matters which is boost pressure + atmospheric pressure which the boost gauge doesn't know and isn't always 14.7psi. If absolute pressure is the way to go with MAP sensors then shouldn't we tune boost that way too?

As stated before, you can use boost or g/rev to control the torque curve. The speed density system in the 80's turbo dodges have a boost vs. mph curve and a boost vs rpm that keeps the boost low to prevent traction loss and prevent damage to the automatic transmissions, which were not as strong as they should have been from the factory. It works really awesomely. A g/rev and a boost system would have to be tuned to the specific car setup.

Vehicle speed is the better of the two as far as traction is concerned. I don't think the 1g VSS is so hot.

As you can see from these graphics the way that it is done on the evos now is pretty slick and should work just as well as a boost vs mph table if you wanted it but can also be more flexible.

I actually started a thread on this earlier but I abandoned it because no one seemed even remotely interested. If anyone is then I would love to move the conversation there and have a cleaner discussion for both topics.
http://www.dsmtuners.com/forums/tun...t-control-evo8-h8-bcs-control-discussion.html

Gear adjustments.

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Boost control table - I couldn't find a current one easily but the difference at this point is that the top row now simply lists the gear and uses the gear adjustments table to control when that gear is activated. This can also be shown as (and controlled using a sufficiently large map sensor) psi with a little hacking thanks to mrfred. Edit: looking at this table more closely it is actually base wastegate duty cycle. If you want to know what the gear based boost control table looks like just change the numbers in the middle to reasonable load numbers like 190 or 260 or 310 or whatever you want and change the table name. The tables are identical in layout and I'm having a hell of a time finding what I want since my tuning laptop doesn't connect to the internet easily.

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http://www.dsmtuners.com/forums/tun...t-control-evo8-h8-bcs-control-discussion.html

 

[tkelly27]

There are only slight variations in pressure from day to day, and you loose 1psi every 2500ft or so, so for the majority of the driving world gauge pressure +14.7 is absolute. Unless you drive through super pressure systems while going up and down 2500ft hills. When you use the ecu to control the boost, you are using absolute pressure. Im not in the state of mind to think about mbc's.

 

[the_mork]

What it ends up coming down to though is that there is enough variation when you consider both pressure and temperature variations to make it worthwhile. There really isn't a downside either.

 

[Hal]

If you were able to control boost in order to achieve a target g/rev (or however you want to measure it), then you would have a tool that the bracket racers would love.

It would automatically compensate for changes in density altitude.

 

[tkelly27]

Thing is, by controlling in absolute pressure you already are compensating for altitude. If your boost target is 30psia then it will target 30psia, even if ambient is 10psia.

The difference will be compressor efficiency as it will have a 3:1 pressure ratio, rather than a ~ 2:1 with an ambient pressure of 14.7. As comp efficiency goes down, and PR goes up, temps go up, so you will be needing to stuff more boost in there to get the same g/rev.

This doesn't seem ideal for the average Joe, but a racer that is racing at tracks that are of different altitudes is probably going to be able to compensate for that.

I don't know about you guys, but really sitting down and thinking about this is really demystifying a lot more than speed density for me.

 

[airmail96]

Originally Posted by habitatguy187 View Post
I have no idea what you guys are talking about, nor do I care, what I want to hear about is people who run speed density personally, what they think about it, how it compares to their old mas system, and how easy it is to tune/reliable.

Jackel was the first tuning system I've ever used dsm wise and I was the first among my friends to go SD. I found it easy as hell to setup and get running. The car ran like it was suppose to be sd. Throttle input was crisp, and the car was just amazing. Like tkelly said it started every time and I wasn't constantly having to mess with it. Once I got it tuned the way I wanted to I drove the car around with out a logger or anything. I didn't even have a wideband gauge . SD I feel is what was meant to be on a DSM .

 

[Hal]

This doesn't seem ideal for the average Joe, but a racer that is racing at tracks that are of different altitudes is probably going to be able to compensate for that.

Sure, if he's willing to build boost curves to do it.

That's why having the controller do it is such a good idea.

 

[twdorris]

Thing is, by controlling in absolute pressure you already are compensating for altitude. If your boost target is 30psia then it will target 30psia, even if ambient is 10psia.

True. One difference would be that boost control using airflow per rev would also account for changes in air density related to temperature (assuming, of course, you have an accurate airflow measurement). Control by absolute pressure would not. Of course, we're getting pretty nit-picky at that point. But if we're talking theory, might as well toss that in too.

The problem I see in either case would be that there's no compensation for changes in power due to things not related to airflow. For example, having to spin the turbo faster to build the same airflow per rev or absolute pressure in the manifold requires more power. Without some compensation for that, you'd end up with slightly different times anyway. Maybe boost control with a g-sensor input would be ideal for bracket racers.

Thomas Dorris
ECMTuning, Inc.

 

[bling5tatus]

Aww, c'mon there's got to be more "the major stand alones are doing it wrong" talk to be had...

 

[twdorris]

The ECU calculates the amount of air in the cylinder based on the ideal gas law (PV = nRT). The stock code measures everything in front of the turbo. The MAF counts vortices in the airflow to know the velocity of the airflow. Since the MAF has a known cross sectional area, we know the volume airflow through the MAF. The stock car also has the Baro and IAT sensors in the MAF. Once the ECU knows these 3 things (P, V, T), it can then calculate n, moles of air (mass). This is accomplished in the ECU by multiplying the volume flow rate from the MAF by compensation factors to account for pressure and temperature.

Yup, looks right to me.

Thomas Dorris
ECMTuning, Inc.

 

[SRiz]

Basic Install summary please?

MAP sensor, ideal is on the intake manifold directly connected. Farther from the intake manifold = bad.

IAT sensor, after the bov, but before the throttle body? Is this ideal?



IAT sensors on stock cars are in the stock airbox, im assuming since the turbo compresses the air and makes it hotter then the intercooler makes it colder you need the sensor in a boost pipe after these things.

If this is true what about METH? The meth will greatly cool the incoming air and make it a bit more dense. I know the IAT is a small part of the A/F calculations, but would putting the IAT after a meth nozzle kill the sensor?

Thanks for any help!

 

[snowborder714]

Basic Install summary please?

MAP sensor, ideal is on the intake manifold directly connected. Farther from the intake manifold = bad.

IAT sensor, after the bov, but before the throttle body? Is this ideal?

Yep, that's it.

The MAP should be as close to the intake manifold as possible. I drilled/tapped a spot on mine so I could thread it right into the plenum. If you can't do this, make the vacuum line as short as possible to it, and have it be the only item being fed from that line if possible.

IAT sensor is typically installed in the throttle body elbow, or around that area.

 

[knochgoon24]

My MAP sensor has about 3" of vacuum hose. to connect it to the IM.
The IAT is in a piece of IC piping about 2" from the start of the throttle body elbow. I've seen people suggest that you don't stick it directly in the IM or the throttle body elbow because it will heat soak the sensor. My putting it in the IC piping, you separate it from that heat by a silicone couple. You IC pipe is also thinner than the TBE and will cool off faster.

 

[the_mork]

Basic Install summary please?

MAP sensor, ideal is on the intake manifold directly connected. Farther from the intake manifold = bad.

IAT sensor, after the bov, but before the throttle body? Is this ideal?



IAT sensors on stock cars are in the stock airbox, im assuming since the turbo compresses the air and makes it hotter then the intercooler makes it colder you need the sensor in a boost pipe after these things.

If this is true what about METH? The meth will greatly cool the incoming air and make it a bit more dense. I know the IAT is a small part of the A/F calculations, but would putting the IAT after a meth nozzle kill the sensor?

Thanks for any help!

You're pretty much correct, as for meth the IAT should be after the injection point by a distance that is arguable but I would suggest whatever it takes to fully atomize the meth. Probably about 10" or so. Turboglenn has done quite a bit of playing with meth and SD on a Haltech and didn't have any problems. I also don't expect that meth should kill an IAT sensor.

 

[Hitchhikkr]

You're pretty much correct, as for meth the IAT should be after the injection point by a distance that is arguable but I would suggest whatever it takes to fully atomize the meth. Probably about 10" or so. Turboglenn has done quite a bit of playing with meth and SD on a Haltech and didn't have any problems. I also don't expect that meth should kill an IAT sensor.

The big thing to worry about with meth/water injection is what is known as the "wet thermometer" syndrome. Meth/water droplets formed on the surface of the IAT sensor render it inaccurate, since it cools the sensor. Regardless as to whether or not the meth/water is suspended in the air charge, you will always have some of the 'fuel' fall out of the charge in a closed container.

Not saying you cant do it, just saying it makes the IAT sensors feedback less accurate. Sir Harry Ricardo proved this back in the early 1900's if you want a reference.

 

[the_mork]

I certainly wouldn't argue against you on that but usually you should be able to make it work out. One of the things about tuning for SD (really tuning in general) is that whether or not a sensor position or input is optimal becomes less relevant as long as you are able to tune out discrepancies. It is part of the reason why we can place the IAT sensor in the manifold, on the TB elbow, or on the charge piping and still make the car function very well. It all comes down to compensating for what should be a fairly predictable situation. I have no idea what my air temperature or pressure are as my charge heads through the intake ports and into the cylinder but it doesn't matter because I know what my air temp and pressure are at the TB inlet and manifold and I can adjust my fueling for a predictable change. Meth adds another variable that we have to tune around but it is definitely doable with enough trial and error.

All points that you are probably aware of but as long as the "wet sensor" is a predictable phenomenon it can be dealt with. Plus IAT compensation is comparatively minimal anyways IMO.

 

[Ceddy]

Plus IAT compensation is comparatively minimal anyways IMO.

The IAT plays a bigger role then is apparent from just the IAT/Baro Compensation table.

I was running SD with no IAT and temp locked at 78*F. (0% Compensation)
In winter the car had a harder time starting and AFRs were off more then a full point.

Playing around with settings, I set IAT to ~220*, and the car wouldn't even run for more then a few seconds.

 

[knochgoon24]

This thread has many of the same arguments as "Speed Density 2.0" over on EvoM.

 

[twdorris]

I was running SD with no IAT and temp locked at 78*F. (0% Compensation) In winter the car had a harder time starting and AFRs were off more then a full point.

FWIW, we posted a small "results" section at the bottom of this page.

SD Theory

Thomas Dorris

 

[Ceddy]

FWIW, we posted a small "results" section at the bottom of this page.

SD Theory

Thomas Dorris

Good info, I think I would have had more drastic AFR differences if I didn't tune my Injectors and VE to no IAT, think they were compensating some at WOT.


Have you looked at Baro compensation with SD? I always thought manifold pressure is manifold pressure and its not effected by outside pressure. But some of the Evo SD guys at high altitude(7500+ ft) have complained of problems.

 

[twdorris]

Have you looked at Baro compensation with SD? I always thought manifold pressure is manifold pressure and its not effected by outside pressure.

I would tend to agree with that, but I guess I don't have any real data to back that opinion up. I only change altitude by about 1300ft each day and that's probably not enough to really notice anything.

I can say I've never heard of anyone on our forums mentioning any such issue with SD at higher altitudes. One of our first beta testers was actually Hal Landry and he's up there pretty far I think.

Just not sure I understand the source or nature of their issues.

Thomas Dorris

 

[Hal]

If you're measuring absolute pressure, I don't see why you would need barometric compensation.

Now, if you were measuring pressure relative to current atmospheric pressure, then I could see needing it.

It seems that if the V/E table is correct, fuel metering should be correct regardless of manifold pressure.

I could easily see fuel metering being inconsistent if the V/E table is off and the tuner simply adjusts fuel to compensate.

Another dimension is the accuracy of the IAT. If you're using a GM IAT, but the ECU has OEM IAT scaling, you'll see issues when the outside temps get cold.