Discussion in 'Start Your Journey Here' started by danlitch, Nov 11, 2006.

  1. danlitch

    danlitch Member

    Has anyone modified their car with an aftermarket intake and exhaust? The theory is to add power without using more fuel by allowing the engine to breathe easier. All sorts of kits are available for other types of cars, but I haven't found one yet for my 2003 Honda Civic Hybrid and was wondering if anyone else had looked into this as well.
  2. RH77

    RH77 Well-Known Member

    Excellent question, and welcome.

    First, the exhaust is a bit of a mystery. Experiments peformed by collegues and Physics discussions have left me still wondering about this one. Super-efficient cars of the past (Civic VX) had a very small diameter exhaust pipe and regular muffler. The problem is, only the vehicle's engineer knows what the engine wants -- because too much restriction is bad and too much flow reduces backpressure. The concensus is to stay stock.

    Regarding the intake. If you have the ability to monitor "IAT" intake air temperature, you want it to be where your car likes it. For my Integra, it gets the best FE on 110F air temps. Fuel maps below that temp tend to run the car rich to heat up the catalyst for emissions, etc., consequently burning more fuel. Mods to keep that IAT in the sweet spot are a good idea. If you have any specific questions or need a step-by-step how-to on an intake, feel free to let me know. Happy Motoring!

  3. danlitch

    danlitch Member


    Thanks for the thoughts. I am coming at this from the vacuum and blower point of view, as I am in technical sales, selling industrial vacuum pumps, air compressors, and blowers. An automobile engine is just a big fancy air pump, and the easier it can pass air through, the more power it can make. More specifically, the less power that the engine expends sucking air into itself and then blowing out the exhaust, the power it has available for doing what is requried of it - moving the car.

    A small diameter exhaust system like that on the Civic VX would be less expensive to make and when used with a muffler, would be quieter. But I think that a smaller diameter increases back pressure and thus decreases power, but without the tradeoffs of expense and noise.

    But clearly, I'm not too worried about those tradeoffs if I am looking into this.

    As for your comments about intake air temperature, what does that have to do with the type of inlet filter and inlet piping? Inlet air temperature will be much more dependent on the weather that day than what type of intake is being used. I want to look into using a less restrictive inlet filter and less restrictive piping to decrease the pressure drop through the intake so that the engine can inhale easier and make more power.

  4. Chuck

    Chuck just the messenger

    I have heard of someone that put a turbo on their Insight - not sure you want to go that far on a Civic, although you would be guaranteed to have an audience if you did.

    I've seen simple kits to bypass the muffler for a little better FE.
  5. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Dan:

    ___An ICE is more then just a pump and although you would think opening it up would provide better FE, when you look at propulsion as a system including the ICE, drivetrain, wheel/tire combo and body there is a whole lot more going on. As an example, the Accord can run at 48 - 50 mph with the TPS at just 12 while offering upwards of 50 mpg’s. The TPS range is 10 - 89. The poor thing is being choked off like you wouldn’t believe yet the FE is higher then when the TP is far higher or when the MAP is running closer to outside when opened up. Follow the FE at the various speeds in the following and you will see yet another real world result of these mostly closed throttle plates at very low load offering FE far beyond what one would normally expect … Beating the EPA … HP does not equate to FE directly so we have to be careful what we wish for. If HP was your goal, free breathing would certainly help but with a harshly throttled down plate allowing extremely great FE, I hope you can see where this is going. The other side of the coin is effluent contact with the CAT. Increasing effluent flow by decreasing back pressure may not be the best solution for that reason as well.

    ___And about the air intake itself. If you have seen how the intakes of some high FE automobiles are constructed, the intake air is sometimes drawn from behind the radiator instead of in front of it. The Insight is a classic example. On top of this, a warm air intake mods in an Insight allows Autostop in temps far below OEM specifications.

    ___When we discuss FE in terms of HW, we have to consider the whole package and not just a free breathing exhaust or cold air intake to increase HP. The OEM based intakes, combustion, and exhaust systems truly provide some amazing numbers as well as holding emissions down to a level that is for all intents and purposes are undetectable at load.

    ___Good Luck

  6. oldguy3939

    oldguy3939 Member

    Ok, let me try this again.
    The freer the air passes into the cylinder, the less drag on the piston in it's travel toward the crank, less vacume in the cylinder on intake. One must also consider air temp. for max combustion.
    A simple porting and polishing can help this. That includes "matching" the ports. IE lining up the intake and ports on the head.
    On the other side, creating a vacume or scavenging in the exhaust will give the combustion chamber a fresh full charge. Max combustion in the cylinder. more boom per pop.
  7. diamondlarry

    diamondlarry Super MPG Man/god :D

  8. psyshack

    psyshack He who posts articles

    I'm a pump man in the hydronics industry. I work with centrifugal pumps. We have a lot in common in our respect industry's. But they are not the same.

    You have brought up some interesting points. Some of what your speaking about is being practiced in modern automotive intakes and exhaust. The intake side of the problem imo is much easier to work with. the exhaust being a bit more static if you will.

    Lets look at my R-18 Civic. It has a semi Atkins head / vtec of the economy type.

    The air intake horn is placed just inside the drives front fender. And yes its a horn. Looks like something out of Dr. Suez if you ask me. It appears to me to be under positive intake pressure. Not a ram air but solid positive intake pressure when the car in in motion. The air intake tract is complex with a resnation box hidden down low. Now we both know that a resnation chamber in your line of work and a bladder tank in my line of work do basicly the same thing. They smooth out the shocks and flow of a system. And sometimes help out with noise. Noise being a example of disruption or uneven flow / friction. The air flow path is very simple and straight forward. This leads to the intake manifold and head. There are pictures on the net of the head with valves out. The ports are very clean for a mass produced head. The castings over all are a industrial work of art imo. And for the money cant be improved on much with a port and polish job done on a good flow bench. Now in this tricky little head design lays the semi Atkins part. When under low load conditions and under 3500 rpm. The head has the ability to hold the intake valve open a milsec. longer on a compression stroke. Thus pushing out part of the induction charge to approx. that of a 1.5L engine. And then holding that charge in the intake tract for the next induction stroke. The only way this charge can be held in check like this is positive intake pressure. If it wasn't positive. The expelled charge in my mind could be broken down and raw fuel running back down the intake tract. A two stage or variable length intake manifold is used also. Pretty high tech stuff over all.

    Heres a link to a video. It does not stream well for me. Maybe your luck is better.

    I honestly believe some of what your looking into is being done.

    Bottom line is power cost fuel. CIA's give the engine the ability to suck in more air at say full throttle. But more air means more fuel. and cooler air means more fuel.

    Now if we could control the fuel to air ratio. Then I would have a lean burn R-18. :)

    Have Fun

  9. oldguy3939

    oldguy3939 Member

    What you have done with the head, Is increase combustion chamber efficiency.
    Is the head holding the charge? or is the cam configuration doing it?
    Getting the air/fuel mix to the cylinder and removing the spent fuel charge/gases would be the question.
    It sounds like what you have, The horn that is, Is what we, In the old days called a velocity stack.
    If you look up old pictures of drag racers using a Hilborn injection system, You may even see me in the background of some of the Ford 427 SOHC engines converted from Nascar to NHRA/AHRA drag racing.
    Yeah, Them were the good old days. We never put any thought to the future.
    Winning races, sold cars. Horse power spoken here. Mass quantity's
    Gas Ronda ( yes, that was his name) Mickey Thompson and a few others used the air intake you discribe. But, In them days it was "Hit-r-miss", As to lenght, Diameter, and location of air intake.
    You are very correct when you say the air passing, Is making noise, or it is taking it's time, Or being disturbed on it's way to the combustion chamber.
    Unless of course, You just have a whole bunch of air moving in the "Duct work".

    My cat wants to talk with me. Later.
  10. GaryG

    GaryG Well-Known Member


    Your bringing back the days that I port matched my early '67 GT500 (202 made at LAX) 427 medium riser. I'm sure there is plenty of areas to improve efficiencies, but my thinking has changed along the lines of Wayne Gerdes' response.

    Things like you CC and polish the combustion chamber and the top of the pistons will help keep things clean and balanced, but designs have come a long way now. Not sure these days of how everything like clearances of pistons and ring end gaps are, but when I built the old big block engines, they were way off from the factory.

    Things have gotten better as the competition for MPG is the big race now. Computers are making the adjustments and combination sensors give detail information as to what air/fuel mixture goes into the cylinders and gases going out of the exhaust.

    You can tell a lot about improving FE just by the climates many of us live in and post the MPG their getting. I wouldn't dream about breaking down my ICE in my FEH to do the old tricks to the engine when I can alter my driving habits to improve FE by almost 100% with it stock and under warranty. But your right about intake and exhaust being very important, I just would be cautious about taking today's ICE under the knife to improve FE.

  11. oldguy3939

    oldguy3939 Member

    Without a doubt I would think long and hard before opening up a new car engine still under warranty.
    I thought one of the posters had replaced the head, In the past it was a "As long as I had it apart" thing.
    Ah yes. The 427 med riser. If you got the "Tunnel port" heads, the air flow was very close to the high riser.
    The most I have done to my cars lately have been installing a K&N air filter, Double plat plugs and run the lightest weight oil I dare.
    Of course run the tire psi about 5 lbs over what the maker recomends, I have been exploring the use of nitrogen in the tires.
    The boys running the 1/8 mile and 1/4 mile ovals are saying the tire temp does not change. The tires run cooler. much.
    I wonder what helium would do?
  12. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Oldguy:

    ___About N2, He, or anything else … Spend some time reading some of our past discussions on the how’s and whys of hypermiling before hitting the HW approach to hot and heavy. The high tech HW add-ons are a very small part of this thing we call hypermiling to reduce our footprints. Most here will never run an 1/8 or ¼ mile oval or even a straight up ¼ but we are trying to raise our FE and reduce our emissions in everyway possible. Adding N2 or He will not do the trick :(

    ___Good Luck

  13. psyshack

    psyshack He who posts articles

    If refering to me about a head replacement. Its all OEM Honda stock. Well except for the WAI. And thats a $2.00 hose. :)

    Ive been watching my tire psi real close for many years. I have a nitorgen bottle with regulator. Even a vacume pump so I could get all the mosture out of a well set tire. And I dont think its worth the time to put nitrogen in the tires of a street car. Sure it will be more stable and will cut down on leakage thru the rubber. But your still going to have leakage thru the valve stem. I just make it practice to check tire psi in my weekly ispection of the car. Its nothing for the wife or myself to put 400 to 600 miles a week on our cars. So check ups are important to me.

    Be good or bad at it.

  14. oldguy3939

    oldguy3939 Member

    Hi, Granted most hypermiling will not entail racing, But the race guys are doing what the hypermilage guys are doing.
    Get the most out of a car.
    Reduce friction, improve airflow around and under a car, streamline it. get rid of extra weight, improve engine efficiency, adapt/change driving habits to exsisting conditions.
    A 1/2 percent here, A 1/2 percent there, can all add up.
    Running n2 in the tires will reduce heat transfer to brake rotors and thereby wheel bearings will run cooler, Less rolling resistance.
  15. antrey

    antrey Well-Known Member

    My 9-2x is currently modified to 285Hp up from 227Hp. The modifications include various exhaust components (cat still in place) and a programmable UTEC ECU. The UTEC allows me to adjust turbo boost, timing, and air fuel ratios. Generally, though, the ECU only modifies the stock ECU signal when under load i.e. boost. When hypermiling I don't use any boost and I stay below 2000rpms at all times so the UTEC is having no effect. Similarly, the exhaust modifications only come into play under boost and higher rpms. Small throttle openings which are typical of hypermiling do not take advantage of the modifications. One way I could take advantage of the UTEC ECU is to run much leaner at low load conditions such as are typical of hypermiling. One UTEC user is running Air Fuel ratios as high as 18:1 withouth knocking or other problems during 0 boost conditions. Running at 18:1 would result in a nearly 20% gain in FE. I may play with a fuel economy map but am concerned with the increased NOx emissions that running lean produces. I would be significantly reducing the amount of carbon dioxide emitted but would increase other emissions. I need to work this out. I'm going to have to dig up my high school chemistry book and see what the result of running leaner is. If increasing NOx while reducing CO2 still helps reduce global warming then it is still in the spirit of hypermiling. Does anyone have insight on the negative environmental effects of increased NOx and other emissions as the fuel mixture is made leaner?
  16. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Oldguy:

    ___Unfortunately, adding N2 to your tires does nothing but possibly make you lose a few $’s and decrease your FE. We rely on a given fill pressure cold. With a temperature increase due to pavement and tire friction, increased pavement temps as well as direct sun, the std. Air filled tire will have a greater increase in pressure then the N2 filled one. N2 for FE is a no go.

    ___WRT increasing temps on wheel bearings, we actually need this although most do not receive the increase through disc or drum brake heat as we try not to use the brakes except under the most adverse of circumstances.

    ___Spend some time looking over the threads regarding N2 fills, tire pressures, and general hypermiling techniques as it is about the fastest way to get onboard if you so desire.

    ___Antrey, leaning out the mixture will bring about a huge increase in NOx, which is bad enough, but the worst part is higher cylinder temps causing damage later on.

    ___Good Luck

  17. oldguy3939

    oldguy3939 Member

    From an engineering standpoint I will have to disagree with you.

    First, Inflating tires from compressed atmosphere, (air), To a preset tire pressure and then counting in the RR of the tire to increase tire temps and therefore TP, You are going from a known to an unknown.
    How long (Time/Miles) will you have to travel before you reach optumim TP, and what is that TP?
    A lot of that will depend on climactic variables, I.E. Ambient air temp, Road conditions, Road surface composition and weight of vehicle to tire size.
    By using N2, The tire can be prefilled to optimum TP with little or no change as to conditions.
    This in turn would creat a constant as far as TP's.
    Then other variables could then be addressed as to increasing FE.

    Just as a side note, The next time you drive for a distance, As soon as you stop, Put your hand on the tire/wheel and feel the temp, This heat has to go somewhere.
    As I am sure you have seen the brake rotor/drum wittness marks from the wheel bolted on. The rotor/drum will act as a heatsink and draw the heat from the tire/wheel to the wheel bearing.
    Some heat in the wheel bearing is desirable to reduce the grease viscocity allowing some what less drag. But the RR of the bearings will produce this elevated temp on their own.
    This is one reason large trucks went to oil lube bearings on the axels, That and they are easier to check, clean and maintain.

    From what I have seen so far of this site, There is really nothing new.

    Acronyms have changed, Instant readout gauges have replaced vacume gauges and pencil and paper for calculating FE, The cars are more conducive to this then 30 years ago, But the driving techniques have'nt really changed all that much.

    One thing that can be improved upon is coming up with a way to get more of this information to the average driver.
    Make people more aware of their driving habits.
  18. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Oldguy:

    ___Place 44 #’s of N2 in one tire and 44 #’s of std. air in another. Drive 10 miles. Measure your new pressure. The Higher pressure has the lowest RR and that will come about from the Air fill, not the N2 fill. It doesn’t matter about “some” final pressure it matters what the delta is and that is where the std. Air filled tires exceed a N2 fill every time.

    ___WRT bearing temps, you apparently have never conducted coasting experiments at temps below 20, 40, 60 and 80 + degrees F from cold soak. We need the heat or our mechanical drag is huge. You may also want to ask Hobbit what kind of temps he felt on the Ranger’s rotors and tires after a little run we had together this past summer. There was no temp gradient to speak of because I did not have to touch the brakes and my accel and decel rates were slow enough that you could not discern the difference between external ambient and tire/rotor surfaces.

    ___As for the rest, you only need to look at real world accomplishments compared to 50 + years ago. You did read the Hypermiling Article from 50 years ago, right? We just happen to hone the techniques in a lot better is all. WRT nothing new, you know your Mustang’s and Taurus’ EPA. You only need to start tracking and posting your tanks and then compare showing us what is and isn’t so new in today’s traffic environments vs. "what traffic" from the old days. With CO2 emissions becoming the problem that it is, I would hope you would consider maximizing your FE no matter what you are driving and from your tone, I don’t believe this to be the case? I hope I am very wrong about that last statement ….

    ___Good Luck

  19. oldguy3939

    oldguy3939 Member

    What I am getting at, is prefill the tires with the n2 to the pressure of the the air filled tire after 10 miles.
    Then you will be at optimum TP from the start.

    I guess one thing I did fail to mention, Is distance. The shortest commute I have had in the Las Vegas Vally is 16 miles one way. With speed zones 35-45 mph. With lights.
    The tires would never heat to any appreciable temp.
    This was the shortest route with the least stops I could find.
    I tried a bunch.

    Some commutes have been around 100 miles one way for a short time.

    The other thing is temp here. You can cook things on the sidewalk. I tried. Eggs sunny up.
    It took about 8 min.

    My 06 mustang does have a "Information" center in it.
    Milage, Average, total, ETC.
    I have found I have adjusted my driving habits as there is a instant readout.
    In the past I watched a vacume gauge.

    I have read milage reports dating back to the Chrysler Dynaflow and before.
    The first car to have better aerodynamics going foreward then backward.

    Yes I am concerned about emissions, But, One has to add practicality to this.

    As a matter of fact, Some believe that the worlds oil reserves have or are about to peak.

    The N2 is being considered here just for the temp.
    Tires with any age to them are prone to blowouts in this heat.

    As far as my tone. Don't take offence. I can be a grumpy oldman at times. Nothing personal.
  20. oldguy3939

    oldguy3939 Member

    I keep my cars in very good tune, Comes from my racing days.
    I had the annual smog done on the taurus and the operator was amazed at the numbers.
    For a 1988 it was passing 2000 standards.
    It runs very clean. I keep it that way.

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