Does anyone have setup parameters and/or screenshots for a working Alpha-N configuration on a 13b NA?
Or if i could be pointed to some where they have been posted (or even actual saved MegaTune files).

Ken, the NA (i am assuming it is an NA) you have running on MS2 were you using Alpha-N or speed density?

Thanks,
Aaron

 

Stock, street, bridge, or peri port? 4 port or 6 port? What ignition are you using, etc. etc. BTW, not including these important details is *my* trick.

 

haha, yeah i should have put all that.

i'd be interested in stock and streetported 6-port 13b NA, using stock S4/S5 fuel and ignition components.

 

I was using speed density. It's a stock engine (we still managed to gain about 30 lb/ft of torque on the dyno too over the stock computer, and all we did was swap in the MS... don't know on HP, the dyno operator kept stopping us at 5500 rpms... he's an old v8 guy, so he thought any higher was dangerous I guess).

Ken

 

heh, that is kind of funny. but 30lb/ft of torque is quite a bit on these cars.

anyway, so no alpha-n (TPS v. RPM) maps out there for stockport NA?

 

so has everyone with a NA 13b been doing speed density?
through some research it seems alpha-n would be better suited to running an NA rotary but if everyone is just using speed density then i guess that is fine.

i would still like to see a good working alpha-n map because i know someone who is trying to get an alpha-n tune working on their Haltech and have been having some issues. they can't find an alpha-n base map for NA for Haltech. i'm wondering if anyone has one for Megasquirt just to look at.

 

I believe everyone is using speed density, I have and have never had a problem with it. Most would have to install another TPS to run alpha-n, as the stock narrow range TPS is little more than an on-off switch.

I'm curious to know why you think alpha-n would be better? Plain alpha-n gives poor low-load performance in my experience. Even on engines with ITBs, like the 20v 4age I've tuned, using speed density at low load, and switching to alpha-n at higher load has worked much better than just plain alpha-n.

Ken

 

i have S5 so the TPS is not an issue. installing a full-range TPS though is not such a big deal also.

as for alpha-n being better i don't have any first hand experience actually seeing if it's true.
i think the advantage comes from the fact that actual load in an NA that might be measured in terms of pressure is not a very wide range. you typically will see higher vacuum for low load but once load starts increasing it doesn't take much to get near high load (pressure-wise). and for an NA throttle percentage is directly related to load, so it just takes time to be able to get a proper working map since you are basically inferring load based on the TPS. but you get a full fixed range with a TPS.
also at low constant loads such as idle, if you have slightly erratic manifold pressure then it may be harder to get a stable tune with speed density, although that is contrary to your experience.

whether it is better or worse i guess is hard to say unless both methods are tried.

but i can see why speed density can give better driveability, since for example actual engine load will change depending on gear, etc. which a speed-density system can "compensate" for.

could you explain using speed density and alpha-n for different parts of the map? is that with Megasquirt?

i was also thinking of using alpha-n for fuel (VE) and speed density for ignition map if that is possible.

 

That's not entirely true... For example, if you're going down a hill, Speed density will show a different load given a fixed throttle position, but alpha-n won't. Same for going up a hill... The result is that the AFR doesn't stay where you tuned it.

It's actually 2 different maps with their outputs set to multiply by one another... you just set the bottom part of the alpha-n map to all 100%, and the top part of the speed density map to all 100% and blend a bit in those areas. This is with ms2/extra.

I don't think code to do that was ever included in ms1... but ms2/extra supports this.

Ken

 

yeah i understand your point about varying load (updated my post to mention that).

i didn't know you could actually mix the maps like that. interesting to know.
so what was your need to disregard the load reading for the top part of the map?

and yeah i'm referring to be able to do that with the ms2/extra code.

 

Well, for most engines, speed density alone works fine, because stepping on the throttle doesn't immediately take you to 100 kPa (or % in ms2/extra). You don't actually go completely to 100 kPa until you are nearly 100% on the throttle.

With the 20v 4age, it has ITBs stock from the factory, and with those, at low revs, stepping on the throttle even 8-10% results in MAP going to 90-100 kPa. At higher revs, it's more like 10-15% throttle. So what I do is from 20-89 kPa, I run speed density, and then 90 kPa and above, I run alpha-n, since at that point, whether I'm going up or down hill will have little effect on load.

The benefit of doing this is that low load and cruise operation is very smooth, with no popping in the exhaust due to too much fuel, and I get better fuel economy. I can actually tune between 15% throttle and 100% as well, where with plain speed density, I could only tune up to about 20% throttle, then 100%, and nothing in between.

I added the ability to run two tables on two different algorithms specifically to deal with this issue, but that code can also be used to do other interesting things, such as running alpha-n on a boosted engine (good when the engine has crazy cams), etc..

You'd just run alpha-n on the primary table, then tune boost on the second table.

I also added 16x16 VE tables to the 2.0.x alphas, so using this code, you could potentially get a 16x30 map (2 bins for blending) or 30x16 map... we didn't really think 16x16 was necessary, but we did it anyway b/c people were asking, and because we could :p

Ken

 

ah ITBs, that makes sense. that's interesting stuff.

and i just assumed ms2/extra was still using the 12x12 maps. 16x16 maps is nice especially running dual maps as you mentioned. gives people who bitch about Megasquirt not having enough resolution less to talk about i guess, heh.
i can't wait to get the Megasquirt in the car and start fiddling around with it. but i needed a new soldering station and it still hasn't come in the mail :angry:

 

Well, 16x16 is only for VE... don't think it's necessary anywhere else (or there for that matter, but we did it anyway)..

We also figured it'd stop people who don't know any better from complaining.

 

This is also the case with my bone stock RV-engine Volkswagen. Touch the throttle below 3k, not even enough to open the secondary butterfly (it's like a 25mm/32mm setup or something grody like that, progressive like an injected 13B) and intake pressure goes to atmospheric.