MPG Quest

[Mishakol129]

I want to get the best gas mileage I can right now for my JDM F23 F22b DOHC engine. Right now it has double stacked IAB plates with the butterflies deleted, a 2.25 ex., short ram filter, and a EDM PT4 ECU.

What I'm thinking is maybe I need to get the PT6 ECU, get the IAB's connected properly, and perhaps go back to a 2" exhaust.

All of the basic stuff is replaced, fuel spark and stuff. It could be more ignition timing is off a hair but can't be that off. My tire pressure is good and its aligned properly. I really think my low end velocity is causing some fuel issues and possibly the PT4 ECU. There's a lot of popping going on when I let off the throttle. What do you guys think?

[ol blue]

If you wanted the most mpg possible, you should have stuck with the f22a. Or get a tune for your own engine.

[Mishakol129]

If you wanted the most mpg possible, you should have stuck with the f22a. Or get a tune for your own engine.

My engine is similar to a OEM setup, its just a F23 with a DOHC head on it. And I know I need a tune but that is not possible for

[H311RA151N]

Having too much volume or more volume than necessary would slow down the intake velocity... It makes sense.

If the intake velocity were dramatically reduced wouldn't it negatively effect fuel atomization? I hope someone chimes in as this is a good question.

[sonikaccord]

I thought fuel atomization was controlled by fuel pressure and injector design. I'm not sure if the velocity of the intake charge makes a huge difference. I am sure that domesticated knows the answer. If this is true, boosted setups would have the best atomization.

Your right foot and a tune. I haven't seen anyone push over 30mpg city in a tuned CB so I'm not sure how much of an increase you are looking for.

[H311RA151N]

I thought fuel atomization was controlled by fuel pressure and injector design. I'm not sure if the velocity of the intake charge makes a huge difference. I am sure that domesticated knows the answer. If this is true, boosted setups would have the best atomization.

Your right foot and a tune. I haven't seen anyone push over 30mpg city in a tuned CB so I'm not sure how much of an increase you are looking for.

I'd bet he does too. I'm having a hard time wrapping my head around intake velocity and it's effects.

I'm thinking volume helps make power up high and velocity helps torque down low... If that's true I'd like to know why.

[Stoner51]

What transmission are you using.
My mpg quest has about stopped until I change transmission. Currently I am at 28.5 mixed city and hwy.
Setup is tuned p28 running 14.9afr with rdx injectors and a coil pack retro fit. I'm pretty sure the stock cb7 transmission would get me to 30

Steve

[jasen klems]

I just did a treatment of seafoam on my car and i have seen much improvement in how the car runs. It is a cheap ( as in cost not product quality) thing to do you put a 3rd of the can in your oil and a 3rd in the fuel and a 3rd in a vacuum line. It help by eliminating deposits of carbon in the intake and on the valves and will also clean the fuel system and injectors. It is a great product to use.

[EsperHamid]

look who's talking hahahahahahaahahaha

[wagon-r]

I thought fuel atomization was controlled by fuel pressure and injector design. I'm not sure if the velocity of the intake charge makes a huge difference.

Fuel atomization is primarily controlled by fuel pressure and injector design. Intake charge velocity also plays a role, but the relatively minor impacts caused by the IABs will not have a significant impact. Especially at low engine rpms, as the fuel has more time for mixing and atomization and will atomize well even if velocity is not the best.

The IABs can have an indirect impact on fuel economy. They do increase intake charge velocity at low rpm, which increases the load range under which the engine can run at stoichiometry. By avoiding enrichment or up-shifting at higher loads, the engine can run efficiently in a lower gear. The impact on torque is much larger than the impact on fuel economy, but there is some improvement of fuel economy as well.

[Mishakol129]

I just did a treatment of seafoam on my car and i have seen much improvement in how the car runs. It is a cheap ( as in cost not product quality) thing to do you put a 3rd of the can in your oil and a 3rd in the fuel and a 3rd in a vacuum line. It help by eliminating deposits of carbon in the intake and on the valves and will also clean the fuel system and injectors. It is a great product to use.

Yeah that probably would help but I got a low mileage block with around 25-50,000 miles. What I think was causing my mpg loss is that some of my rings were frozen cause I was mysteriously losing oil. Not losing any more oil and I think my mpg's are around 28-29 mpg.

But the Seafoam would have been a good idea too I just have been driving regularly and sometimes revving the engine up which I think fixed it.

[Mishakol129]

look who's talking hahahahahahaahahaha

You talking to me?


Still running the Pt4 ECU, does anyone know if that ecu uses the IAB's?

[GhostAccord]

Sticking with the stock F23 would have netted you the best MPG and overall reliable power. Now the only way to get more MPG out of your hybrid build is a tune or keeping a lead foot of the pedals.

There is no magical engine additive or cleaner that will gain you the MPG that this engine could be achieving with a tune.

[johnl]

.... power up high and .....torque down low...

Don't get confused with the 'power up high' and 'torque down low' thing. Power is power and torque is torque, and both exist at any rpm. Torque however is a 'real' thing that can be directly measured, whereas power is 'only' a calculation that includes time (the 'minute' in rpm). If you have X power at Y rpm, and want X+ power at Y, then the only way you will get it is to increase torque at Y rpm. This applies across the whole rpm range.

Very simplistically, what you feel increasing the velocity of the car is torque, an actual force, whether it's lower or higher in the rpm range. What you feel as 'torque down low' is the torque produced at lower rpm, what you feel as 'power up high' is torque produced at higher rpm. What you perceive as 'power' at any rpm is probably the rate at which torque is increasing as the rpm rises over time.

Power vs torque is an argument that confuses even very knowledgeable people, and smarter ones than I am. The previous paragraph is just my take on it...

I'm thinking volume helps make power up high and velocity helps torque down low... If that's true I'd like to know why.

The volume of air (i.e. quantity) entering the cylinder is what it's all about at any given rpm.

At higher and higher rpm the air flow through the port (and to a lesser extent the induction tract as a whole) will at some point become cross section limited, you can only flow so much air in a short time period through a given sized port, unless you push it in harder than atmospheric pressure can do (turbo anyone...). With a larger cross section more air can flow in the same short time. At higher rpm the time available from valve open to valve closed is relatively short, so a bigger port will tend to flow more air in a shorter time. If the port is too small for a given rpm then the air flow becomes 'choked'.

At lower rpm the airflow isn't cross section limited, but is velocity limited. Air will pass at a slower speed through a larger port, faster through a smaller port. There is more time at lower rpm to fill the cylinder, and the faster the air moves the more will get into the cylinder. Increasing the port size results in the air speed slowing down. For a given port there will be a point on the graph where at a particular rpm the air velocity is at it's maximum, and not slowed by 'excessive' port size. This will be the point at which maximum flow rate for that port at that rpm will be optimal. Any larger and the air speed will slow too much resulting in less inducted air.

This is all affected by cam timing, valve size, port length etc. What may be an ideally sized port (no such thing exists really, since the rpm is constantly changing) for one camshaft etc. may not be for another. It's all about choosing the best compromise for intended purpose.

[wagon-r]

Nice explanation, John.