1st Gen Haltech ECU Discussion

How heavy are your current tires?

 

Around 70lbs. With the wheels each corner should be around 94 lbs.
My previous setup I calculated should have been around 64 lbs, so the goal is to get under that.

 

That's a pretty significant difference. I don't really drive my truck around other than a few times a month for pleasure otherwise it is for camping/exploring trips so the tire weight is necessary but sometimes I think it'd be fun to put the land cruiser wheels/tires on. But would look goofy with my fenders and probably wouldn't be ideal with my gears either.

 

There's just so much inertia in it, I feel like there's a good chance I'm robbing myself of a lot of fun. Worth a shot I think

 

You're on stock gears huh? I didn't like my truck starting from a stop or not revving out on 4.10s and 35s. Auto would be worse since you've only got 4 ratios and likely none of them feel great in the tiny window of rpm it lets you use. With the 4.56 out of boost and from a dead stop my truck feels like stock. With an auto you'd probably need 5.29 to feel similar since that also robs power like no ones business... tires vs trans swap though... I'd do the trans to a manual and you'd instantly pick up a ton of "seat of the pants" power.

 

I believe it. I rode in a manual once and was like wow. I never regeared either because I feared what it would do to my highway mpgs

 

The regear has helped me keep my MPG and still feel good around town, I barely need any pedal to maintain 70 and I cruise at like 2650rpm. But no load in that window with cruising AFR at ~15.5+/-.5.... sheeeit I can still get 18mpg in this thing loaded for a weeks adventuring. If you were to overgear it could hurt MPG for sure but with how the auto makes an engine struggle on this platform and you being on 35s I don't think overgearing is a possibility really. Plus being able to cruise with TC locked more (less load) helps MPG for you too.

 

Dang that lean huh? I should probably drive... Not 85 lol. My psi gauge is basically atmospheric at that speed, cruising. Seems like no matter what I average 12.5mpg though

 

Yeah you can go into the 16s in cruising if you really wanted to. It's totally fine as long as the load is low. The only reason manufacturers don't do it in the US is because it produces more NOx. But like if you use HP tuners and look in an LS ECU the lean burn mode that they have is in the computer but it's turned off in US markets. They go deep into the 15s in low load cells

 

Also yeah 85 with your aerodynamics and automatic transmission and crap gears is a bad combination for miles per gallon I'm amazed you're actually not getting 10 miles per gallon or lower.

 

If my estimate of fuel left is correct, I just got 16.5mpg highway after 130 miles tonight... Probably averaging 78mph or so

 

That's not bad, I get my best MPG somewhere around 68-72mph.

 

I'm still mulling over if I should put the effort into connecting my MAF back up for load based ignition timing. Anyone come across documentation of mass airflow vs throttle position in a general sense? If they're relatively linear I would just use that but I want to see a graph vs RPM and pressure and can't find one.

 

I've never seen anyone do this for any reason unless they were running a full alpha-n setup, this just adds a layer of unpredictability especially since the MAF on these can be maxed out in a turbo setup relatively easy. Why remove resolution from your system and have two required sensors for operation. Your spark map is already deterministic by pressure which is related to load (it is your load measurement in speed density) in your system. Why not just get some knock ears and buy some Dyno time to actually dial yours in instead. I can't imagine why your setup would be an exception to a system that works well for just about any vehicle unless something in your setup was fundamentally wrong to begin with

 

Well because #1 it wouldn't remove resolution, it's an additional modifier, and #2 the actual mass airflow varies with throttle position, gear, RPM, and pressure and isn't seeming to be captured fully by the speed-density tactic. eg: at various RPMs I can be at any level of pressure, and that doesn't translate to load directly. I can bounce around my throttle within let's say +/-5% at a given setpoint, and still be at the same RPM and pressure (and you can audibly hear the engine load change). It might be an A/T or torque converter thing, idk, but there's definitely something amiss. Knock tuning I would want the same thing, an actual load axis.. But that is my next concern: where does the MAF max out and how do I handle failure or disconnection since that would advance my timing under this scenario


btw after getting to know my Saab ECU much better, I'm sold on the mass air/torque request model as the superior tuning method, though it is substantially more confusing to wrap your head around (but that doesn't matter rn)

 

Yeah this isn't going to prove fruitful. If you aren't having consistent easily repeatable desirable results with something as simple as speed density, something in your setup or mapping is wrong. Before you embark into the work of esoterica and over complication, return to step one and start fresh. If everything is running well and you're are only perceiving a load change then you're probably just overthinking things. Hell log the calculated engine load parameter if it makes you feel better. Exchanging one load measurement for another and thinking it's going to solve an issue indicates the problem is elsewhere.

 

Ok, I'll do some more logging if for no other reason to disprove/prove my own insanity lol
Really really do want to get that timing dialed in though (get my knock sensors in), it's itching me now

 

Right on, if you had a weird engine configuration with like individual throttle bodies or something. Or like one of those Atkinson cycle engines or heck even a two-stroke where there's a ton of reversion I'd say maybe using a different load measurement would be wise but really we have like the simplest engine configuration and speed density is more than capable.

 

I did some efficiency tuning while road tripping the last weekend and picked up 3-4 mpg!

I do have a CAN gauge so I can see AFR's and coolant temps. It barely hit 200* on a couple climbs but immediately recovered so far running good.

I am a bit sad I can only make 2psi above 9500', I think it's time to machine the snout down and swap the 58mm pulley on.

 

I am concerned that logging Haltech calculated load is going to be self-defining (cyclical) since there is no MAF sensor, after reading this: https://mechanics.stackexchange.com/questions/17537/how-is-engine-load-determined
It's going to use some kind of alternate formula based on the VE table, so I'll have to connect the MAF anyway to do a reporting comparison
Just for the record