Dynamic Map Sensing Throttle Feedback

[greasemonkee]

I don't drive much, nor have I compared with/without the device. On a bone stock 94 Integra with 200k on the clock, it looks to be averaging 33 mpg city. That is over a 3 week period per tank and about 4 cold starts a day. I really need to tune the pig or at least get a narrow band afr monitor so I'll know how much I can load it.

I may have been loading it too heavy this last tank. The larger air cylinder just came in, it's going to get an upgrade this week

[greasemonkee]

This seems to be approaching full authority feedback. New cylinder installed, it doubled the feedback force. The pedal is quite aggressive during higher engine loading. No conscious effort is required to use it. Accelerating from a dead stop now requires feathering the clutch more since it throttles back automatically.

The next step would be a constant rate spring that depresses the pedal instead of your foot. Apply pressure to the spring and you set the load for the engine and it remains constant regardless of rpm. Some people on here are using hand levers for throttling, adapting a spring to that design would make this a constant load cruise control if there would be anything to gain from it.

[greasemonkee]

So it's been about 10 months now, enough for me to get a few tanks of fuel in and establish a solid number. Our last pure gasoline station pulled out recently and after checking ethanol content of the stations in town, I found Enmark to be the least at 4-5%. Oddly, I so no change in economy.

Only mod other than the feedbackis a partial grill block on the integra, otherwise bone stock -

City/rural/daily routine driving averages just a hair over 40 mpg. I normally hit the rev limiter about every other day when my patience runs thin with the slow pig (and to blow the carbon out), but also coast engine off on the downhills to work. Tank refills occur 3-4 week intervals

Interstate at 70 mph is about 40mpg as well, slightly increasing with diminishing speed. I only had the opportunity to check this on a couple tankfuls this summer thus a greater error probability.

The gizmo is still solid and maintenance free, and once I learned how the engine wanted to be loaded, the numbers increased, with no gauges...

[theycallmeebryan]

I personally think it is an outstanding concept. I am pretty sure a driver's reaction to feel is quicker than reaction by sight, when comparing looking at a vacuum gauge to this device. Drivers will be able to keep their eyes on the road and will be able to use another sense to drive efficiently.

If big manufacturers ever caught on to something like this, they would have to make a disconnect switch or button for liability reasons. You don't want any lawsuits because people claimed they couldn't accelerate fast enough out of a situation.

[usergone]

WOW, I like this idea! I may just go implement this on my truck. I wonder how my numbers would change because I usually use a heavy foot and shift low with my weak engine and heavy truck.

How does the cylinder work? Did you put a spring inside of it, then hook the line on the back to the manifold vacuum?

This seems very similar to a speed governor on a small engine (like a lawn mower). The "throttle" control just pulls more or less on a vane that is pushed on (by oil or air, usually) increasingly at higher speeds, which pulls opposite of the spring, and is hooked directly to the throttle. If you go and manually push open the throttle, it pushes back at you with the increase in speed.

[greasemonkee]

That's it, but instead of governing it to engine speed, here we're governing it to load. The aft side of the cylinder is connected to the vacuum reservoir.

I've let a few folks drive the car (who didn't understand the concept), they only seem to say "it feels like a really big spring on the gas pedal". Makes me wonder if the cylinder is big enough to suit the average driver. By nature they tend to "force" the throttle open into a higher load at low rpm. It really doesn't take a lot of effort to override the cylinder.

Following a gauge alone is mighty tricky, for me at least. Driving cars other than mine now give me a strange feeling, like driving a car with a fixed steering wheel.

The drawings for a full autothrottle are complete, just I've had a challenged initiative to make it real.

[cfg83]

greasemonkee -

Thanks for the update. So you were getting 33 MPG (city) and now you are seeing 40 MPG?

What's neat is that you are creating a "foot gauge". It's like when computer GUIs are supplemented with strategic beeps and sounds to increase the feedback to the user. Your eyes stay on the road and your foot knows what's going on.

CarloSW2

[orange4boy]

I like the idea. Simple and analog. It's really a great idea.

The one problem I have with it is that I understand that engines are, roughly speaking, most efficient at about 75% throttle between 2000-3000 rpm. So in effect the best driving should be brisk acceleration at those parameters then a high load, low rpm cruise, or better yet, pulse and glide averaging around cruise speed.

Do you see where I'm coming from?

For this, you need to hook it up the opposite way as an earlier poster assumed you were going to do.

You'll have a lot of vacuum (heavy pedal) at idle, and little vacuum (light pedal) at wide throttle, low RPM (where I try to drive). You might find that you have less control and smoothness during the transition between the two. Maybe the extra feedback in your foot is worth the loss of sensitivity.

I have tested this theory myself and found that using heavy acceleration as opposed to light gave me a bit better MPG in an automatic. Many others have seen big increases in manual cars. Not what would be expected as we are often told to "avoid jackrabbit starts"

[greasemonkee]

It really depends on throttle body sizing vs. engine displacement as to what throttle position is most efficient at X rpm. Here I'm aiming to regulate manifold pressure to achieve it's peak efficiency. But you're right, very light loading is quite inefficient and better to shut the engine off and coast. There is a fine line in loading engines with a factory tune running closed loop - once you cross the threshold by loading too much by either falling out of lean burn or, at the least, falling out of stoichiometry. I don't like to use throttle position as a term for referencing loading, since (at least hondas) closed loop threshold is determined by the ecu via the table values - throttle position vs. rpm - and using the algorithms to generate the final value. In the end, the table more closely mimics manifold pressure. Generally, the cars I tune gently taper down to rich after 750 millibars, so my intuition tells me somewhere in that area is the target for lowest bscf.

It did take a bit of shifting my driving style around to figure what it liked. I do know that she doesn't like to be loaded much (manifold press) at low rpm (1000-2000). Theory meets reality.

I don't care for pulse and glide unless it's down hill of a .5 mile minimum and can retain the posted speed limit

[orange4boy]

OK, you could teach me a thing or two.

I've always wanted a way to indicate the mixture at any given moment. My van does not have a wide band oxy sensor though so the easy way is out. I have not been able to find the BSFC chart on my engine. For now I have to just wing it and guess at best throttle position. I have a vacuum gauge that I have to hook up again which I suppose would be the simplest if I knew at what point it started to enrich.

Ideas?