Secondary load parameters

[flak monkey]

I am trying to get my head around how these settings work in megatune, and would just like some clarification

I am running a boosted engine on throttle bodies, and will have map and tps hooked up. I would obviously like the best map I can get for both driveability and performance so am thinking I will probably need these settings. I am thinking of running primarily alpha_n and then from say 90Kpa speed_density to work with the boost. I am expecting very poor idle vacuum due to very large roller barrel throttle bodies.

Could someone explain in simple terms how the settings work? I assume this somehow uses 2 VE tables?

What is the difference between multiplicitive and additive?

What is the effect of the multiply primary load option?

How do these settings affect tuning? Is it still possible to use tunerstudios ve analyser or megalog viewer to do analysis of logs, or will I then need to do it myself?

And the same for ignition, what is the effect of using a secondary load here?

Thanks in advance,
David

[muythaibxr]

Could someone explain in simple terms how the settings work? I assume this somehow uses 2 VE tables?

Yes, VE1 uses primary load, VE2 uses secondary load.

What is the difference between multiplicitive and additive?

This is how the two tables are combined. You can either multiply the lookups from both tables or add them.

What is the effect of the multiply primary load option?

What version of the firmware are you using? I think this should probably be Multiply MAP now unless I'm remembering wrong. It just multiplies MAP into the fuel equation. I would recommend leaving this turned on.

How do these settings affect tuning? Is it still possible to use tunerstudios ve analyser or megalog viewer to do analysis of logs, or will I then need to do it myself?

It's considerably more difficult to use the analyzer once you move to tuning the second table, but it's not impossible if you bound things well when you're using the analyzer.

[/quote]
And the same for ignition, what is the effect of using a secondary load here?
[/quote]

It's the same as for fuel, only there's no option to multiply the tables. Ignition tables are only additive (and you can enter negative numbers).

My recommendation for ignition though is usually use % baro or speed density for load, even when running alpha-n for fuel. In my experience this works better.

Ken

[flak monkey]

Hi Ken,

Thank you very much for the reply. That makes it a little simpler to understand. I like to understand these things as best I can before I start, then I stand a better chance of getting it right later

You are right, the mutiply primary load is now multiply map and I will leave this turned on.

So when setting up my VE tables, I can set VE table 1 as TPS 0-100% then VE table 2 as MAP 90-200% and then the second VE table will only be used from 90Kpa upwards (once I come on boost) and effectively the 2 tables at this point either get multiplied together, or added together depending on my setting. I assume I then need to change the fuelling algorithm to alpha_n in configurator too?

Is it as simple as when on additive if the VE table entries are say 20 and 40 the result is 60? And when on multiply it would multiply them together?

Thanks again,
David

[muythaibxr]

Hi Ken,

Thank you very much for the reply. That makes it a little simpler to understand. I like to understand these things as best I can before I start, then I stand a better chance of getting it right later

You are right, the mutiply primary load is now multiply map and I will leave this turned on.

So when setting up my VE tables, I can set VE table 1 as TPS 0-100% then VE table 2 as MAP 90-200% and then the second VE table will only be used from 90Kpa upwards (once I come on boost) and effectively the 2 tables at this point either get multiplied together, or added together depending on my setting. I assume I then need to change the fuelling algorithm to alpha_n in configurator too?

Is it as simple as when on additive if the VE table entries are say 20 and 40 the result is 60? And when on multiply it would multiply them together?

Thanks again,
David

You have to be sure to blend the edges of both tables if you use multiplicative. So the bottom of the MAP table should have 100% in it to use only the alpha-n table.

Ken

[flak monkey]

Thanks, it sounds like additive is probably the best solution for my engine then?

Off boost run alpha_n then once boost comes in add in the values from the second table from speed_density.

Am I right in thinking the fuelling algorithm in configurator should be set to alpha_n (i.e the primary load) if I go this route?

[muythaibxr]

I'm not sure additive will do what you want... Actually, I'm not sure this feature will do what you want at all.

I think you want to use table switching and not blended tables.

I say this because if you use alpha-n for primary load, you can get into boost at different throttle positions, and the multiplier or adder will be different. You won't be able to tune on boost.

Ken

[flak monkey]

Doh, I thought that was how it worked. Obviously not


See my post below...

[flak monkey]

Actually scrap that last one....

Doing a search on old posts I think I found what I wanted.

Running alpha_n primary load then speed_density secondary load in multiplicitive then I just have VE table 1 with normal values in, then VE table 2 start at 95Kpa up to 200Kpa. Set the first line values all at 100 then it will only use the alpha_n table under 100Kpa. Then once the boost comes in it will use the second table values as the multiplier for each point in the alpha_n table.

Is that correct? Seems simple enough if so?

Like this msq....

[muythaibxr]

The problem with doing it that way is that both tables are always active.

So when you're off boost, the lower part of your speed-density table will be getting multiplied by everything in your alpha-n table. Once you get on boost, the value being looked up in your alpha-n table will still be getting multiplied by whatever boost you're at. You won't be able to tune consistently that way.

Instead what you want is table switching set up to switch tables when you go over a certain kPa.

Ken

[flak monkey]

I thought that with the bottom row of VE2 set at 100 all it will do off boost is use VE1 (as everything is multiplied by 1) then as it comes on boost it will start to use the values in VE2 to multiply the appropriate point in VE1. Or am i missing something?

If I want to use Kpa for map table switching is it as simple as putting the jumper on the MS2 daughter card as described here:

http://www.msextra.com/doc/ms2extra/MS2 ... ableswitch

I dont fully understand the R10 references and additional switch input circuit, or is this only required with an external switch?

Finally, I assume if running alpha_n main table if I select the switch point to be Kpa for VE3 that it knows that VE3 is in terms of MAP and not TPS? From what I have read else where I was under the impression that the load for VE3 is whatever the load for VE1 is set at. Hence why I was looking at using secondary load.

Thanks again,
David

[flak monkey]

Anyone?

Is secondary load going to work for me? If not and I run switched tables and run VE1 in alpha_n will VE3 run in SD? If so how do I set this as its not obvious.

[muythaibxr]

I thought that with the bottom row of VE2 set at 100 all it will do off boost is use VE1 (as everything is multiplied by 1) then as it comes on boost it will start to use the values in VE2 to multiply the appropriate point in VE1. Or am i missing something?

You are correct, but say you're at half throttle and you manage to boost to 170 kPa (lets say for the sake of argument that this is the maximum boost you can achieve). Now you increase the throttle position, but boost is still at 170 kPa. It is likely that the half throttle spot in your alpha-n table is one VE, and the full throttle spot is another. It is unlikely that the amount that you increase by between those points in the alpha-n table are going to give you the correct AFR in both cases while at the same boost.

If I want to use Kpa for map table switching is it as simple as putting the jumper on the MS2 daughter card as described here:

http://www.msextra.com/doc/ms2extra/MS2 ... ableswitch

I dont fully understand the R10 references and additional switch input circuit, or is this only required with an external switch?

Finally, I assume if running alpha_n main table if I select the switch point to be Kpa for VE3 that it knows that VE3 is in terms of MAP and not TPS? From what I have read else where I was under the impression that the load for VE3 is whatever the load for VE1 is set at. Hence why I was looking at using secondary load.

Thanks again,
David

I'll have to look into the table-switching conditions. I'm pretty sure that you can make it so that you can switch based on kPa or alpha-n, but I'm not sure you can use different load calcs for both. I'll have to take a look at the code to be sure.

You might want to try the 2.1.1 beta or the 3.0.3 alpha code though which have much improved MAP sampling. You might not need to go to all the trouble of tuning 2 tables if the new MAP sampling code makes your MAP smooth enough.

Ken

[flak monkey]

Thanks Ken, I see where you are coming from now, makes more sense.

If you could check out the table switching conditions and if its possible to run different load parameters on each table I would really appreciate it.

Thanks,
David

[muythaibxr]

Will do, but like I said, the new MAP sampling code might make it a moot point. You may want to give that a shot too.

Ken

[flak monkey]

Well fired the engine up for the first time yesterday and have a few issues to resolve.

The idle MAP is around 75-80kpa, even using the latest alpha code with the new MAP sampling. I have the filters set at 20 and 140.

I am also having issues trying to get the idle speed down under about 1200rpm. Idle advance is 4deg and AFR about 14. Roller barrels dont seem to seal very well even though they are brand new and even with no visible opening idle speed is still too high. I dont appear to have any leaks either

Starting to wonder if I should have even bothered with DTH throttle bodies now