An introduction from an unlikely hypermiler

[theunchosen]

I kinda figured you were running high grade fuel. I would be cautious moving the horsepower forward. Obviously stock boosted cars can undergo HP performance enhancement without worrying about the engine but the greater the power-to-weight ratio of the engine the more dangerous knock becomes.

I was pretty sure Saab would have anti-knock systems in place since they are more of a up-scale manufacturer, nothing against those that don't, mine doesn't. Combining the economical driving with the performance you will want to carefully watch engine temps and exhaust temps. Squeezing the block one way a little is fine, but then squeezing it the other way a little too you get into places that pre-ignition is more common. IF that happens because WAI eco and some grill shielding while performance driving Carmen will need a heart transplant in a hurry.

[Ritmusic2k]

There are no worries on bumping up the power. My first priority is to keep the engine healthy. Following a well-established path, I'm going to make the engine more powerful and more robust, and I'm stopping well short of where I could go. There are 450hp Viggens out there.


The key is, I won't be trying to get one configuration that is both powerful and miserly, so I'm not going to have to worry about a 300hp setup that runs dangerously lean and hot. In my mind, my eco-tune will effectively turn the turbo off, and soften the hell out of the throttle mapping. I can also set torque limits for each gear. I probably won't lean things out too much; I don't want to save a little gas at a cost of dumping ridiculous amounts of NOx into the atmosphere. But the point is, in eco mode, she'll prolly only be able to make 170hp as a result of the modifications.

Ideally, it'd be as easy as turning a knob to switch modes, but I'm a little way off from that.

[theunchosen]

If you leave the turbo on you can get outside the 14.7-30:1 NOx range. Anything leaner than 16:1 and you produce NOx while anything higher than 30:1 and it goes away again. around 20:1 is where its worst so a little lean is alot worse for the environment than a lot lean.

That said you won't have anywhere near 150 HP if you lean out to clear the NOx range. But highway driving won't require probably anymore than 50-60 HP and then you could jump into lean and burn very little fuel. If you are going lean though and forcing the ECU to do it I would stay away from WAI and go CAI as it will serve you better for the HP gains anyway and keep you well inside the quasi-equilibrium-esque dome away from turbulent knock and pre-ignition areas while boosting and running ultra-lean.

[Ritmusic2k]

Wow, that's great info; I'll take it to my ECU gurus and see what they have to say about achieving this! Many thanks!

[theunchosen]

I would test it very carefully and very slowly. Like after the car has cycled through fast idle and moved on to "I'm not ready to be out of bed" mode. If you can get it below 400 RPM you're only getting around 2 combustions per second which is slow enough to shut it down if the engine doesn't like it.

And I would start with small ratios(A little NOx in the testing stages is way more Eco friendly than a new engine). I would also ask a mechanic more familiar with the Viggen or the B235( I think thats what you have). The particular engine really might not like the idea of that much "cool" air without as much "warm" fuel.

Ultra-lean burn is an evolving field so field testers are taking it slowly because very few autos go to that range.

I think you might be able to get outside the 30:1 because you've got 240 hp to work with. I've got 100 and 25% of that is not really enough to be useful.

[Ritmusic2k]

Hey all!

So, I haven't really been posting since, well, since I wrote up my introduction... but I have been playing around very much. A quick update and some shocking developments I discovered just this afternoon.

First, I installed my Scangauge II and it made an immediate impact on my mileage. It won't look like it when viewing my fuel log, but that's because I've spent good amounts of time driving the crap out of her lately... rest assured, the SGII is, it turns out, all I needed to achieve my original goals.

And the breakthrough is this: I didn't actually achieve 45mpg highway, I achieved 45mpg city.

I never gave Carmen enough credit for it because she's tuned to be a high-RPM screamer, but she makes practically diesel-ish torque at low RPMs... I just never had the cojones to find ]out .

Well, today, on my way back from work, I short shifted a little too soon and was surprised to find out that my engine could drag me around at idle RPM at almost no throttle in 5th gear... sitting at a pretty 30-35mph. And in doing this, I was achieving sustained instantaneous mpg readings between 45-55mpg!

With a little pacing and route memorization, I think I'm going to see incredible gains over time. It's a surprisingly comfortable way to travel, and I've caught the economy bug all over again. Cheers!

[cfg83]

Ritmusic2k -

Congrats to you and Carmen! 5th gear is your friend.

CarloSW2

[SentraSE-R]

Wow! You'll have us all out looking for torque monsters now .

[Nevyn]

Can you imagine a population of Viggens being driven for economy? We all buy 'em, and go on a road trip as a convoy.

Somebody rolls past in an M3 or a Corvette or a 370z or what have you, and sees a troop of Viggens chugging along at 50 MPH. The look on their face would be priceless!

On a more serious note, congrats on the accidental discovery! Most people say that to shift for economy, pull the lever between 1700 and 1900 RPM. You'll have to experiment, but there's a start.

[Ritmusic2k]

Originally Posted by Nevyn

Can you imagine a population of Viggens being driven for economy? We all buy 'em, and go on a road trip as a convoy.

Somebody rolls past in an M3 or a Corvette or a 370z or what have you, and sees a troop of Viggens chugging along at 50 MPH. The look on their face would be priceless!

On a more serious note, congrats on the accidental discovery! Most people say that to shift for economy, pull the lever between 1700 and 1900 RPM. You'll have to experiment, but there's a start.

Hah, the more the merrier.

Regarding the upshifting: when driving conservatively, my last 9-3 (same generation as the Viggen) would illuminate the shift-up light for 5th gear at 35mph. That would've put it at about 1200rpm. I ignored it because that 2.0 and smaller turbo didn't have the guts to chug along that slowly. But the Viggen's 2.3 and larger turbo make all the difference. I end up upshifting from about 1500rpm and setting at 1000rpm in the destination gear. It's such a weird feeling, but she seems to like it.