Intake air flow modification

[zpiloto]

Wanted to see how intake air would affect FE with increased airflow and then with a restricted airflow. Removed the original 18” airduct that went from the air box to the forward corner of the engine compartment and replaced it with a 4” long piece of 2” diameter PVC that is directed towards the exhaust manifold. Reset the ECU and did runs with car configured with normal, 2” hose, and restrictor plate on a 41 mile test loop. The restrictor plate was made buy covering 2” hose with cardboard with a 1”x1”hole cut in the center. Each mod showed an improvement. With the restrictor there was a slight decrease in acceleration but good drivability. Max RPM was 3575 and Max speed was 60 MPH.
The restricted airflow shows promise but I forgot to reset the ECU for that run. During the run with the restricted airflow when I would shift into neutral to coast the idle RPM would only drop to around 1300 until the car would come to a stop then drop down to it’s normal 650 RPM. Towards the end of the run the idle was dropping to 1000 RPM so I think that it will eventually get back to its 700-800 RPM range which will save on fuel. Scan gauge results below.

Conditions: Beginning of runs calm winds 76
End of runs calm winds 70

Normal 36.4 MPG
40.0 MPH Avg

2’ Hose 37.0 MPG
38 MPH Avg

Restricted 37.3 MPG
39.0 MPH Avg

[Matt Timion]

Excellent test. I'm going to throw this into the Experiment's forum in hopes that other people repeat your test and post their results as well.

[SVOboy]

I had that idea to block off some flow a while ago, but never mentioned it cuz I forgot, :p, I'm glad someone clever with a scangauge got about to testing it. :)

[MetroMPG]

what's the fuel-saving theory behind restricting airflow?

[SVOboy]

I believe it is less airflow per throttle position, more throttle, less pumping losses, therefore equal power for less.

[zpiloto]

I’m just guessing but there is probably a sweet spot on the amount of air restricted to get the best fuel flow and still have performance acceleration without getting squashed getting on the highway. I basically reduced the airflow by 2/3. The original area of the 2” opening was 3.14 reduced to 1. I might try ¾” x ¾” opening in the restrictor and see if it chokes off to much air. The way it is set up now the acceleration starts to drop off once the RPM reach about 3200. My normal shift point on the automatic is 2500 RPM. I think that most of the fuel saving comes from the acceleration factor so if you were doing a lot of highway miles it might not show any improvement.

[krousdb]

I believe it is less airflow per throttle position, more throttle, less pumping losses, therefore equal power for less.

Perhaps this is part of the reason behind the smaller diameter throttle body on the D15Z1, 40mm vs 56mm I think?

[SVOboy]

Perhaps this is part of the reason behind the smaller diameter throttle body on the D15Z1, 40mm vs 56mm I think?

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.

[MetroMPG]

I believe it is less airflow per throttle position, more throttle, less pumping losses, therefore equal power for less.

i don't get it. help me out here.

assume 2000 rpm constant load and no restrictor plate. let's say the throttle is open at 4 out of 10.

now add a restrictor plate. to maintain 2000 rpm, now the throttle must be open to, say, 6 out of 10.

since we're at the same engine speed (load/power output), we must be consuming the same amount of energy (gas), and also inhaling the same amount of air.

it seems to me like all we've done is shift the location of the intake restriction from the throttle plate towards the restrictor plate - with no net change in pumping losses.

[diamondlarry]

Another thing I would be concerned about is the TPS. On OBD2 at least, the TPS plays a part in fuel injection rate. If you had to open the throttle more it seems like the ECU would want to dump in more fuel.

[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]

Perhaps this is part of the reason behind the smaller diameter throttle body on the D15Z1, 40mm vs 56mm I think?

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]

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.

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

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.

[Compaq888]

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.

I have a MSD digital window switch. I can make anything attached to it turn on or off at any rpm I desire. But I don't want to spend anymore money on my car. I'll just use what I got and attach a long hose from the bottom of the car to the airbox. That way when the car goes up really steep hills it will stay in 4th or when I accelarate a little bit harder. After extensive research my car gets the best gas mileage with the stock intake system. The stock intake system is just not good for going up steep hills because it doesn't supply enough air.

[kickflipjr]

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.

How does this work. Buy adding more restriction you can open up the throttle more. It doesn't seem like would work. Restriction=Bad. Velocity=Good.

Maybee a second throttle that you could adjust on the fly would work. It would be a better way of restricion (even though i don't think this is a good idea in the first place).

[Compaq888]

Think of it like this. You need restriction for constant speed. You need a good flow for accelaration.

[krousdb]

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.
Admittedly, I too am having difficulty understanding the benefit of a second restrictor. The only thing I can think of is that on vehicles that use a TPS, you could achieve higher vacuum at a certain throttle position, thereby causing the ECU to trim the fuel differently. meh. Or maybe the MAP sensor would give a different reading causing a different fuel trim, but I don't have a MAP sensor so, again, I say meh!

[SVOboy]

Or maybe the MAP sensor would give a different reading causing a different fuel trim, but I don't have a MAP sensor so, again, I say meh!

Where'd your map sensor go?

Mehbe someone else with a fuel meter could go and test this out, meaning you.

[krousdb]

OK, then maybe I dont have a TPS. I don't have both do I? Anyway, I would like to know why two restrictors works better than one before testing.

[SVOboy]

I don't have both do I?

Yeah you do. Your TPS is on the side of the TB facing the firewall and has three wires coming out of it, and you MAP is on the top of the TB with three wires and says MAP sensor on it or mounted on the firewall right behind the TB and says MAP on it. B7s I have been seeing at the junkyard in civics with firewall mounted sensors, which makes me think that my IM/TB is not from a b7, or something, mehbe just the rail and tb, I dunno.

Anyway, I would like to know why two restrictors works better than one before testing.

Anyway, I would like to think that this is just the opposite effect of sticking a big *** 4" CAI, except with a small *** 1.5" HAI. So it'd follow basically the same principles, and as kickflipjr was saying, it would increase velocity as there is less cross-sectional area.

[Matt Timion]

Yeah you do. Your TPS is on the side of the TB facing the firewall and has three wires coming out of it, and you MAP is on the top of the TB with three wires and says MAP sensor on it or mounted on the firewall right behind the TB and says MAP on it. B7s I have been seeing at the junkyard in civics with firewall mounted sensors, which makes me think that my IM/TB is not from a b7, or something, mehbe just the rail and tb, I dunno.

Wait, you've been seeing B7s with with firewall mounted MAP sensors? Firewall mounted MAP sensors were obd0. OBD1 Map sensors should be on the intake manifold/TB. I can take a picture of my z1 if you guys want to see where it's mounted.

[MetroMPG]

Anyway, I would like to think that this is just the opposite effect of sticking a big *** 4" CAI, except with a small *** 1.5" HAI. So it'd follow basically the same principles, and as kickflipjr was saying, it would increase velocity as there is less cross-sectional area.

but the HAI feeds the engine less dense air, that's why the throttle has to open further. it needs a higher volume to do the same amount of work.

if you don't change the density of the air, then forcing the throttle to open further because airflow is being starved by an upstream restriction offers you no advantage.

analogy:

1. you're drinking a thick milkshake through a straw with the "mouth" end 75% closed (squished).

2. you squish the "cup" end of the straw 75% closed, which permits you to open up the "mouth" end fully.

have you experienced a change in the amount of effort to drink through that straw? any effeciency gains from the perspective of pumping/throttling losses? i don't see any.

[SVOboy]

Wait, you've been seeing B7s with with firewall mounted MAP sensors?

Yeah, three of them today, wanna fight about it?

[Matt Timion]

Wait, you've been seeing B7s with with firewall mounted MAP sensors?

Yeah, three of them today, wanna fight about it?

Lol... yeah... uhm, let's fight about it.

I was certain that all obd1 cars had TB map sensors. I even took one off of a obd1 Civic DX once. Guess you learn something new every day.

[SVOboy]

Yes, I was also surprised, but I don't know anything. I was gonna say wanna mess and then I did not, I'm in a mood today.

[rh77]

I'm entering this late since I've been on vacation, but I'm thinking that this experiment might yield might some interesting results. Let's break it down -- what happens if the same amount of air has to travel through a smaller tube? The air velocity increases -- like if you put your thumb on the end of a garden hose. So, faster air does what? Well, the throttle plate will be open wider to get the air moving, which we've determined allows better FE. But after the fast air hits the valve area, would it act like mini forced induction and require more fuel to prevent deadly detonation -- or introduce more air, less fuel?

Hmmm...

RH77

[JanGeo]

you guys are all over the place on this topic and forgot about the fuel mixture at different loads and the efficency at different loads of an engine. This goes back to driving up a hill at different speeds in the same gear to figure out the best efficency of the motor for MPG. There should be a power - speed setting for a motor that yields the best mpg all affected by the engine timing fuel mixture valve timing bore stroke thermal efficiency intake and exhost factors.

The trick is to find it and operate at that point.

[MetroMPG]

Let's break it down -- what happens if the same amount of air has to travel through a smaller tube? The air velocity increases -- like if you put your thumb on the end of a garden hose.

i think that comparison may be misleading.

- the intake air isn't travelling through a smaller tube, it's just going through a smaller opening, into the original size tube. i don't think the pressure "advantage" is maintained. svoboy essentially pointed this out when he mentioned the intake manifold is different (smaller volume/cross section) in the more efficient motor. if you don't change the manifold size...

- blocking a garden hose pressurizes everything upstream of the block; adding a restrictor plate doesn't do anything comparable to the ambient pressure. and i'm not sure if the effects of a pressurized hose can be compared to a de-pressurized (vacuum) intake manifold - though i could be wrong.

- also, the garden hose is expelling its contents (water) into a different medium (air) - an apples-to-oranges comparison. if it were expelling its contents into water (a narrow opening into larger volume), the velocity effect would be quickly diffused relative to air.

sorry, but i still don't see how adding a restrictor plate to an otherwise unmodified engine would help.

[rh77]

It's just a theory -- perhaps an optomistic experiment I could try.

How about this: since you're essentially "choking-off" the intake air, more throttle input is needed, power decreases, but what happens? Would the ECU realize the problem and compensate with more fuel, or since less power is produced, less fuel is used?

Race drivers use restrictor plates to reduce horsepower to even the playing field. I wonder how their economy is affected...hmmm.

RH77

[JanGeo]

all the restrictor plate does is limit how fast you can burn fuel so you run a little / a lot lower max power level. in the case of a smaller intake manifold there is higher velocity air flow and better atomization but we take care of that with acetone.

[JanGeo]

ok anyone else seeing slow down on response and gassavers.org not available in the past few days? it's why the double post - took so long that I forgot I clicked post already.

Added some 5cc GP-7 to a friends Xtera last night then topped off the gas tank from the lawnmower gas can to wash it down - could not syphen even a drop of gas out of the full tank after he drove a few miles. Thinks he gets in the teens but has no idea what he gets - just spends $60 a week on gas and drives like a nut sometimes. The top off with the gas can really fills it up nice glugg glugg - thing has something like a 25 gallon tank visible from the wheelwell.

[rh77]

So I know this guy that has a problem in town with accelerating too quickly. I won't reveal his identity, but could a restrictor force lower power around town so I...I mean so he could accelerate more slowly and use less fuel in town? Then on the highway more throttle input is required creating fewer pumping losses? I mean, it would be easy enough to try out and I could get a reading of fuel-trim (the chip I have has the capability to analyze manifold pressure too, but the car doesn't report it). I get back home late Friday...

RH77

[JanGeo]

I have a problem with the gas pedal on the xB - it is too light so much so that I get a cramp in my shin holding my foot OFF the pedal. Try a step spring on the throttle, one that adds extra tension on the pedal about 1/4-1/3 the way to the floor or even less, then you have to push HARDER to burn gas. I think an adjustable tension point on the spring would allow you to use it like a cruise control. Something I am thinking of trying. The restrictor plate would work for this applicaton also.

[rh77]

The spring sounds like a good idea to try out, but when people are behind me in town, I always feel guilty that I'm holding up people that are in a hurry. I'd end-up stomping on gas despite the extra tension, and my right calf muscle would be buff. (See the Hanz and Franz pic in another thread around here somewheres). Anyways, if it's the car's fault (restrictor plate), I'm not entirely guilty -- don't blame me, it's the car - mentality. But that is only if it yields better gas mileage. But yeah, some Toyota variants that I've driven have a soft throttle -- it is painful to keep your foot out of the firewall.

RH77

[Ryland]

what I'm seeing happen is this:
if you block off your intake, you are able to open the butter fly valve in your throttle body farther, those butter fly valve cause alot of turbulance, causeing the air entering the engine to swirel, creating drag, so really it's a simaler affect as installing a smaller carb, or throttle body, you are able to run closer to WOT more of the time, thus a smother flow of air is entering the intake, it's all airodinamics.

[MetroMPG]

hi ryland (welcome to the site).

that's the first bit of evidence i've heard in favour of the restrictor.

if turbulence from the throttle plate is a fuel efficiency drawback in throttle bodies, i wonder why carmakers don't use a different design, like a variable diameter aperature rather than a butterfly valve.

[rh77]

It's easy enough to do, so if I can sneak into the garage this weekend, I'll block-off part of the intake and run a test. Drivability will definitely be very different. I just wish I knew the algorithm for throttle input and manifold pressure on OBD-II Hondas. If I got my hands on the ECU's schematic I probably wouldn't know how to read it, though.

RH77

[Matt Timion]

hi ryland (welcome to the site).

that's the first bit of evidence i've heard in favour of the restrictor.

if turbulence from the throttle plate is a fuel efficiency drawback in throttle bodies, i wonder why carmakers don't use a different design, like a variable diameter aperature rather than a butterfly valve.



I know it's not exactly the same, but you DID make this post a while back:

http://www.gassavers.org/forum_topic/throttleless_premixed_charge_engine_ultimate_wai.h tml

I've been dreaming of it ever since :)

[DaX]

hi ryland (welcome to the site).

that's the first bit of evidence i've heard in favour of the restrictor.

if turbulence from the throttle plate is a fuel efficiency drawback in throttle bodies, i wonder why carmakers don't use a different design, like a variable diameter aperature rather than a butterfly valve.



I once wondered about an aperture style wastegate, but it would be expensive to create.

If turbulence from the throttle plate is a drawback, then the claims from devices like the Turbonator are definately bunk, as these types of devices do just that - create turbulence.

[rh77]

I'm hoping that more throttle and the choking effect has an impact on power production, as opposed to what the air is really doing, to reduce the need for fuel. I may be way off, but less air would require less fuel for Stoich, right?

RH77

[SVOboy]

I just wish I knew the algorithm for throttle input and manifold pressure on OBD-II Hondas. If I got my hands on the ECU's schematic I probably wouldn't know how to read it, though.

You want fuel and ignition maps?

[SVOboy]

I may be way off, but less air would require less fuel for Stoich, right?

Ya manG.

[rh77]

Ya manG.

Sa-Weet. My theory may hold. By the way, thanks for the fuel maps S-Dogg! I might consider altering the maps for optimum efficiency.

RH77

[JanGeo]

Now you can see where you should be going!

[Ryland]

If turbulence from the throttle plate is a drawback, then the claims from devices like the Turbonator are definately bunk, as these types of devices do just that - create turbulence.


you need turbulence to mix the fuel and air, an example of that is the intake mainfolds on some carburated engines have a sort of corkscrew like piece of tin in there, AFTER the carburator, there is no point in creating unneeded turbulence befor the carburator, or fuel injectors, of course the finer the mist of fuel you can get, the less turbulence you are going to need as well, but you still need some just to get the fuel mixing, altho, the valves should do some of that as well.
you can get multi barral carburators, and they are great at cutting down turbulance, the wider open they are, the more openings they have, but for a carburator to work, they need restriction, and that is where fuel injection is amazing, it doesn't need the restriction to work properly.
I once tride to make a throttle valve out of a camera iris, I never finished it, but if you could hook that to your TPS and calibrate it, I think it could work great, also useing a thrttle slide, insted of a butter fly valve could work, like motorcycle carburators use, only hook that to a TPS as well, the idea being to keep the throttle opening as smooth, and round as possible, another idea that I had was useing something like a piece if inertube, and air or water presure to close and open the inside of it, thus creating an extreamly smooth opening for your throttle body.

[SVOboy]

you need turbulence to mix the fuel and air, an example of that is the intake mainfolds on some carburated engines have a sort of corkscrew like piece of tin in there, AFTER the carburator, there is no point in creating unneeded turbulence befor the carburator, or fuel injectors, of course the finer the mist of fuel you can get, the less turbulence you are going to need as well, but you still need some just to get the fuel mixing, altho, the valves should do some of that as well.
you can get multi barral carburators, and they are great at cutting down turbulance, the wider open they are, the more openings they have, but for a carburator to work, they need restriction, and that is where fuel injection is amazing, it doesn't need the restriction to work properly.
I once tride to make a throttle valve out of a camera iris, I never finished it, but if you could hook that to your TPS and calibrate it, I think it could work great, also useing a thrttle slide, insted of a butter fly valve could work, like motorcycle carburators use, only hook that to a TPS as well, the idea being to keep the throttle opening as smooth, and round as possible, another idea that I had was useing something like a piece if inertube, and air or water presure to close and open the inside of it, thus creating an extreamly smooth opening for your throttle body.

This reminds me of somender singh's head grooving for FE by swirling up the ****.

[Bruce]

If flow restriction outside of throttle body is more efficient, does this mean that a dirty air filter would _increase_ FE (at the expense of WOT performance)?

[Ryland]

my main question is, when you are doing all this stuff with changing the air intake duct work, are you reducing the size of the duct in just one area, or are you changing the size of the whole thing? because just like exaust, the air intake is tuned, that is why the d15z1 engine has a smaller throttle body, and air intake, is it's running at a lower speed most of the time, requring less air, and you want to keep that air velocity high, this is a very key point in air box, and intake manifold design, in an ideal world, your whole air intake would change in langth, and diametor as your engine speed changed.

[kwtorbe]

I plan on testing this theory on my '97 civic HX with a d15z1 intake manifold. I need a VX intake because I want to maintain the EGR valve.

I will port match the head to manifold ports. Then I will either port the TB area out to accept the larger HX throttle body and use HX injectors and sensors (may need to make an adapter which I can do with a drafter friend of mine and his machinist friends), or I will use the smaller VX TB and the smaller VX injectors and sensors (but then I worry about compatibility of the electronics).

Ford 5.0 guys install larger mass air flow sensors, TBs, and fuel injectors for more horsepower; why not install a smaller TB and injectors for better FE?

The theory I am going off of is Q=VA. mass flow=velocity*area. The VX has smaller runners so the same mass of air with move with a higher velocity. I believe this may increase FE, but I know it will increase my torque and HP at lower rpms and decrease my overall horsepower and torque which is found at higher rpms in a 4 cylinder.

From personal porting experience on mopar 318ci heads to the port size of 360ci heads, I know that heads with smaller ports provide better FE and a lower rpm powerband, while ported heads provide better high rpm power but kill low end performance. This is the reason racers use high stall torque converters and steep gears with massively ported heads and large lift camshafts.

If nothing else I believe my d16y5 will have better low rpm power.

Any suggestions on VX throttle body vs. HX throttle body and there abouts are greatly appreciated.

[jeffreymccoy]

I'm hoping that more throttle and the choking effect has an impact on power production, as opposed to what the air is really doing, to reduce the need for fuel. I may be way off, but less air would require less fuel for Stoich, right?

RH77

Any updates on this experiment RH77? Wondering if you have tested and what the results have been?

[rh77]

Any updates on this experiment RH77? Wondering if you have tested and what the results have been?

Well, it's been a while -- a few conclusions...

I attempted to reduce the airflow by reducing the intake diameter, but it seemed like the PGM-FI controller (on the Honda engine) became confused with the lower Manifold Pressure vs. the Throttle Input. No improvement was noted over several months -- in fact, it seemed to slightly reduce FE performance.

On another note, it was noticed throughout the test that 90-100F intake air temps resulted in optimum FE. I ran 91-octane fuel for 140+ air to prevent detonation, but again, no improvement was noted, and more money was spent on the higher grade fuel.

Too cold, or too hot = decreased FE. First, check a shop manual for IAT response (cold temps force a rich situation -- but too hot: the fuel charge needs cooled to prevent pre-ignition, which equals more fuel injected) -- and each engine design is different. At the same time, hotter engine operation than stock (in my case) has resulted in a a mechanical advantage to increase FE (including a hotter thermostat).

Quicker-to-normal temps from the Block Heater get the engine to closed-loop, and increased efficiency with the automatic transmission. Tightening the throttle-transmission cable has increased hydraulic pressure, quickened and tightened shifts, and increased the torque converter lockup response (places the engine in the optimum RPM range for FE, sooner). Some vehicles, on the contrary, will be quick to downshift with this mod, and decrease FE. Mileage will vary -- only tests can confirm results.

Geez, I think I just summarized most of my major engine experiments :o

RH77



The conclusion was that each engine series is different. I encourage experimentation and the data

[jeffreymccoy]

Great summary - Thanks RH!

[thisisntjared]

Great summary - Thanks RH!

bro you are doing really well with your f150!!! congrats! when any newb with a truck is asking how to get better mpg with their v8 i am going to point them to you!

[jeffreymccoy]

Hey thanks for the encouragement. I couldnt have done it without the awesome information compiled by the users of this site. I look forward to finding more ways to improve things... hopefully one day, Ill be able to contribute - or at least have a singe place (my garage) with all the mods and what they have done to help the tank that I drive.

[bowtieguy]

Hey thanks for the encouragement. I couldnt have done it without the awesome information compiled by the users of this site. I look forward to finding more ways to improve things... hopefully one day, Ill be able to contribute - or at least have a singe place (my garage) with all the mods and what they have done to help the tank that I drive.

have you tested acetone? some of the guys like it, others do not. i'm split because my olds likes it, but my wife's camaro does NOT.

[jeffreymccoy]

Tried acetone on a couple of tanks - no noticable difference. Probably will not continue. It may have hurt it some, but was hard to tell for sure.