Intake air flow modification

[SVOboy]

There are two reason why this works. One is that the higher the gear, the lower the frictional losses. By getting to 5th quickly, the total number of engine revolutions is reduced, with a corresponding reduction in frictional losses. The second reason is pumping losses. This is the work done to force air past a partially closed throttle plate. The more closed the throttle is, the higher the losses. Accelerating quickly reduces throttle losses, because the throttle is open. In addition, engine speed is lower in fifth, so to generate the same amount of power, you have a larger throttle opening (and hence lower throttle losses) - this is another reason to get to higher gears as quickly as possible.

The best fuel economy is gained by a combination of the gas petal to the floor with shifts at as low an rpm as possible to sustain your desired acceleration. This ensures a fully open throttle during the entire acceleration event and gets you out of the lower gears as quickly as possible, for lower frictional losses.

Taken from insight central, a slight description of throttle position and frictional losses, I will try to find something better.

[Matt Timion]

Originally Posted by SVOboy

I am in agreement, but the manifold is also vastly different to suit that so it's not just the smaller TB. I'd say a D15Z1 IM/TB would be quite a good FE upgrade, considering the way it is designed with the resonance and all that that Bunger explained.

if you ever go to a CX/VX/HF intake manifold be sure to get a different intake hose as well as air box top. The smaller bore TB requires a different intake hose.

Lucky for me I found on in a CRX HF a few months back and have been saving it for my engine swap.

[krousdb]

Originally Posted by SVOboy

Taken from insight central, a slight description of throttle position and frictional losses, I will try to find something better.

Here is a quote from Wayne Gerdes, also about the Insight. It seems to contradict the quote above:

Originally Posted by Wayne Gerdes

Given the IMA based Insights best FE came about by riding leanburn (even during acceleration!), I was always the go-slow, no-assist, bring her up in a low RPM driving scenario kind of guy. I never ever touched VTEC and never had I seen > 4 bars of 20 of assist during my own brand of low G accelerations … Unless something needed to be ran away from or traffic was building behind for example. On warmer days (80 + degrees F), she would allow me to reach 100 mpg in less then 3 miles using this approach. No one using the WOT, 1-2-5 shifts, or heavy assist w/ maybe 1/2 throttle all the way to WOT had ever seen those kinds of numbers using those higher G acceleration rates that I know of. Because of the slow and steady accelerations, I know the mechanical friction losses are at a minimum and the strain on any given component was minimal at best let alone did I rarely if ever touch the pack. I am an absolute believer in longevity from whatever we drive and the go slow approach should yield superior results to a larger throttle plate opening/lower pumping losses at higher RPM’s.

See the entire thread here:
http://www.cleanmpg.com/forums/showthread.php?t=255

I am absolutely tentitive on the WOT approach, while simultaneously feeling a definate maybe on the go-slow approach. There you go. The choice is obvious.

[SVOboy]

I actually saw on insightcentral some controlled testing contrasting these two types of acceleration and WOT won. Lemme try and find it.

EDIT: http://www.insightcentral.net/forum/viewtopic.php?t=4139&highlight=full+throttle

[krousdb]

Originally Posted by SVOboy

I actually saw on insightcentral some controlled testing contrasting these two types of acceleration and WOT won. Lemme try and find it.

EDIT: http://www.insightcentral.net/forum/viewtopic.php?t=4139&highlight=full+throttle

Well it seems that the guy performing the test did get better results with WOT. 75.6 vs 74.4 MPG I think?. But WOT is easy to do. What is hard is mastering gentle accel usng leanburn. Wayne had a lifetime average of 92.8 MPG in his Insight before he sold it, over 90k miles IIRC. His best tank, on which he used the gentle acceleration technique was 109.0 MPG for 1523 miles.

At least in the case of the Insight, I would put my money on gentle acceleration with leanburn.

[Matt Timion]

I think that someone should invent a "gentle accel" cruise control. Tell it your target speed and then it will slowly accelerate over the period of like 3 or 4 minutes to that speed.

[Compaq888]

I think the WOT theory is good, think about this.

My best mpg comes from my 4th gear because the torque converter locks up.

My strategy has always been accelarate slowly and smoothly on the streets and I rarely get into 4th because by the time I get up to 4th gear there is a red light. But if I were to accelarate first and get into 4th gear and stay there I would get 35mpg+. I think at 40mph I get 40mpg+. Until 4th the torque converter doesn't lock up. So I think on the streets I would gain some mpg if I get into 4th sooner and stay there because accelarating slow almost never gets me in there.

[MetroMPG]

but we've kind of shifted from a discussion about the potential FE benefits of using an intake restrictor, vs the potential benefits of using WOT on an otherwise unrestricted (or stock) intake.

i understand the theory behind WOT.

but i still don't understand the theory behind adding an additional intake restrictor (i say additional, because the throttle is also a restrictor by definition).

i think svoboy was onto something when he said:

I am in agreement, but the manifold is also vastly different to suit that so it's not just the smaller TB.

in order for pumping losses to be reduced, you want to have as close to ambient pressure as possible in the manifold. i don't understand how adding a restrictor upstream of the throttle addresses that. sure the throttle is open further, but the upstream airflow is now restricted, so the pressure in the intake manifold can't be as close to ambient as if there were no additional restrictor.

[Compaq888]

I've restricted my intake and it did increase my mpg by 1 but it killed power. Everytime I had to go up a small hill it would downshift because the car barely moves as is in 4th. I also opened up the intake and lost 1mpg but there is more power in the low end and the engine breathes better. I think the best setup would be to have a special box that opens up based on rpm conditions. Like in front of the airbox. It's better to stay in highest gear and use more fuel than to downshift and use even more fuel.

[SVOboy]

You could make that intake switcheroo deal if you want, it'd be rather easy with just a hacked up vtec activator or you could make something special to read the rpm signal off the distributor and have it going that way.