really struggling to get to 40mpg combined

[guest001]

I have a 88-91 civic hatch, that I turbocharged. As hard as it is to believe I don't drive fast all the time. Honestly it's main because I've to really get it to run 100% properly as far as the tune, boost leaks, the pcv system, and other things. So the tune I'm using is a stock bin/maps for my car supposedly. though it ran my car great before and after turbocharging, with only changing timing in boost ( a few degrees retard per lbs of boost) and scaling down the fuel map for the larger injectors installed. The program doesn't have the ability to tune for temp changes but the o2 works and I get a 14.7 afr during cruising and idle.

I've never had the car dyno tune. The ignition maps could be way off as far as I know. I messed up on an alingment and did the front first. o and its lowered and I don't have a camber kit. other then that I rebuilt the motor, transmission, extensive tune-up. I incorporate a lot of driving techniques. FCOD, not using brakes as much as possible, not driving fast, not stoping at some stop signs, not really letting my car warm up for more then a few minutes to get settled.

I dunno, I've tried different plug gaps, the most recent thing I've started doing was FCOD and it seemed like I was going to get better mileage but I didn't get much more then 35. started using 5w30. nothing has really got me into the 40 range.

Anybody else kinda struggle or fill like they've maybe hit a wall, like what I fell. writing this I'm thinking a supermid or fuel mileage is what I need??

[1cheap1]

I could get 40 or better in your car but i would ruin the turbo. I have 2 3000gt vr4s with twin turbos so i know how hard it is to get every thing to run just right. I don't think mpg when i drive them, 35 in a turbo car like yours is just fine i would think.

[guest001]

Originally Posted by 1cheap1

I could get 40 or better in your car but i would ruin the turbo.

How??

35 is good. I get better highway, 40 +. I'd love to see 40 combined though.... maybe I will have my ignition timing tuned on a dyno. If I had the car running 100% like I'd really like I'd probably get way worse and drive way faster. having a turbo and complaining about mileage is pointless I suppose. turbochargers are so fascinating to me.

[jeep45238]

You really do need to get that thing dyno'd and tuned properly - conservatively by a bit though.

[guest001]

if the maximum torque is created when the peak pressure occurs at, what 15-20 degrees after TDC. ( I really don't totally understand this, peak pressure thing totally). then it would impossible to tune for best power with a dyno. but isn't the relationship between detonation and max torque.

no, there was a good link some posted on here. and he was explaining how an engine could be knock limited. so even if you where to tune to where your knocking, then back off the timing. you'd still be off. . or would it be. wait would ether way, being knock limited or not, backing off at the point of detonation would be a good start, or if you didn't have a dyno.

there's this thing people are making called a det can. that allows you to hear detonation really well.

[1cheap1]

Well, if i drove your car i would not let it warm up. Just start going and eoc before it was ever warm. In traffic would eoc at every opportunity, skip gears when starting from a stop, draft a lot and coast when ever possible. Stay under 2000 rpm and almost lug the engine. This would mean no cooling for the turbo because i would turn off the ignition as much as possible, would not use turbo timer to let it cool off. I do other stuff as well.

[guest001]

Originally Posted by 1cheap1

Well, if i drove your car i would not let it warm up. Just start going and eoc before it was ever warm. In traffic would eoc at every opportunity, skip gears when starting from a stop, draft a lot and coast when ever possible. Stay under 2000 rpm and almost lug the engine. This would mean no cooling for the turbo because i would turn off the ignition as much as possible, would not use turbo timer to let it cool off. I do other stuff as well.

I really only let it warm up for a few minutes. but I get the point.

I try eoc for a little, bit it didn't work so well. I could see it using a lot more gas then normal on my fuel gauge ( I look at my fuel gauge to see whats really wasting a lot of gas, I know its not super accurate). I take advantage of the fuel cut-off feature (FCOD). and that seem to help a lot. I also kinda do a variation of pulse and gliding. where, when I drive. I completely let off the gas (fuel injectors cut off), instead of stoping. and brake only if I absolute have to. and if I do brake I kinda pulse width module and only brake as hard as I need to.

I don't and wouldn't lug the motor. its really not good for the motor at all. I'm not going to go that far. I just rebuild the motor and transmission and I'm not about to tare it apart again prematurely.

I really don't turbo time at all, unless right before I stop the car I've been driving really hard. I get what your saying and taking it to these extreme would probably get me to my goal. but if that's the case, I guess I'll just be happy with 35.

[theholycow]

I've never seen it abbreviated as FCOD -- it's usually written as DFCO (Deceleration Fuel Cut Off).

I describe your strategy as P&DFCO (Pulse & DFCO). I tried it and it really held me back; when I quit P&DFCO and merely used cruise control, I gained nearly 10%. I quit when I really thought about it and realized that there's not a reason for it to work on most cars with manual transmissions. You're doing the same amount of work whether you're in DFCO or not; the engine is running at the same RPM and accomplishes the same quantity of revolutions. Normal P&G works because you generate power at maximum efficiency and then disconnect the engine from the road so that the engine can idle at far lower RPM, so in the same distance the engine goes through fewer revolutions.

Of course, if you need to decelerate or stop, DFCO is the right choice...but if you didn't need to decelerate and you are going to need to re-accelerate as a result then it's probably not the best option.

We do have at least one other user who seems to be getting good results from P&DFCO, but I suspect that it doesn't work for most cars and most drivers.

As for lugging, I don't know if your car is new enough to have computer-controlled ignition timing and a knock sensor, but if so then it's probably almost impossible to lug. There's a link about it in my signature, but in short, with modern vehicles either it goes or it stalls, the computer prevents lugging. If so, you still don't want to cause the engine to rumble a lot, but you don't have to fear low RPM...if it rumbles you either downshift or ease off the throttle until it quiets. Shifting as low as possible definitely helps my 2008 VW; I can't say for sure that it would help your car, but there's a pretty good chance.

[guest001]

Originally Posted by theholycow

I've never seen it abbreviated as FCOD -- it's usually written as DFCO (Deceleration Fuel Cut Off).

I describe your strategy as P&DFCO (Pulse & DFCO). I tried it and it really held me back; when I quit P&DFCO and merely used cruise control, I gained nearly 10%. I quit when I really thought about it and realized that there's not a reason for it to work on most cars with manual transmissions. You're doing the same amount of work whether you're in DFCO or not; the engine is running at the same RPM and accomplishes the same quantity of revolutions. Normal P&G works because you generate power at maximum efficiency and then disconnect the engine from the road so that the engine can idle at far lower RPM, so in the same distance the engine goes through fewer revolutions.

Of course, if you need to decelerate or stop, DFCO is the right choice...but if you didn't need to decelerate and you are going to need to re-accelerate as a result then it's probably not the best option.

We do have at least one other user who seems to be getting good results from P&DFCO, but I suspect that it doesn't work for most cars and most drivers.

As for lugging, I don't know if your car is new enough to have computer-controlled ignition timing and a knock sensor, but if so then it's probably almost impossible to lug. There's a link about it in my signature, but in short, with modern vehicles either it goes or it stalls, the computer prevents lugging. If so, you still don't want to cause the engine to rumble a lot, but you don't have to fear low RPM...if it rumbles you either downshift or ease off the throttle until it quiets. Shifting as low as possible definitely helps my 2008 VW; I can't say for sure that it would help your car, but there's a pretty good chance.

Yes, I meant DFCO, I couldn't remember. but um, I don't do P&DFCO exclusively the whole time on the freeway as a technique for a whole trip. I just do it when I have to stop. in traffic. plus it increases brake life. really don't get p&g? even if your rev up the motor to an rpm where your at a higher efficiency aren't you using more fuel? I dunno, I haven't really read anything on it.

I have electronic ignition. but I don't have a knock sensor. I'll have to check out the article. I shift at about 3-3.4k, cause it seems if I don't I don't go anywhere and I have to accelerate faster.. I really need to somehow put all my techniques together and kinda develop a style so new technques results can really be seen.

do you have a mpg gauge??

[theholycow]

Originally Posted by guest001

Yes, I meant DFCO, I couldn't remember. but um, I don't do P&DFCO exclusively the whole time on the freeway as a technique for a whole trip. I just do it when I have to stop.

OIC. I wouldn't compare that to P&G, and I wouldn't call that P&DFCO; it's just using DFCO when you're planning to slow anyway. That is, IMO, the best way to use it.

really don't get p&g? even if your rev up the motor to an rpm where your at a higher efficiency aren't you using more fuel? I dunno, I haven't really read anything on it.

You're using more fuel during the pulse, but then using less fuel during the glide -- and it adds up to less fuel spent by the time you get to your destination. You have to look at the big picture and spend the least amount of energy to get to your destination, rather than being too concerned about how much energy you're spending at any given moment. During the pulse you invest some gas, and it pays back with interest during the glide.

Here's why it works:
- You're making gas into kinetic energy more efficiently, by operating closer to your maximum BSFC RPM. The engine produces work most efficiently when it is at 100% load.
- Your engine has to turn fewer revolutions to get to your destination. While in gear, it's going to turn the same quantity of revolutions as before, but when out of gear it will turn less. Each revolution turns some of your energy into engine friction; engine friction is waste.

Above, I wrote that the engine produces work most efficiently when it is at 100% load. This is in part because the throttle is more open (so it doesn't have to work so hard sucking air through a closed throttle -- part of a phenomenom described as "pumping losses"), but probably mainly because it's subject to almost the same friction/reciprocating losses while making a lot more power. Whether you make a little power or a lot of power, the piston rings scrape the cylinder walls, the pistons and connecting rods have to change direction repeatedly, and so on.

I have electronic ignition. but I don't have a knock sensor. I'll have to check out the article. I shift at about 3-3.4k, cause it seems if I don't I don't go anywhere and I have to accelerate faster..

Your car can probably lug, then; the knock sensor is what prevents it. Your high RPM needs match Honda's reputation, so if you can't lower your shift points and still accelerate well then I'd say don't worry about it.

I really need to somehow put all my techniques together and kinda develop a style so new technques results can really be seen.

do you have a mpg gauge??

I just got a ScanGauge II for Christmas. It requires a 1996 or newer car.

Previously I've been using a DIY fuel rate meter, which doesn't tell me MPG but it does tell me fuel rate -- great for telling me which gear to use at a given speed, and great for indicating DFCO. That DIY fuel rate meter would work with your car and there is a link about it in my signature. I think inside that post there's a link to another post about using an Acura MPG gauge on a Civic (ok, I just looked, here it is).

A dozen years ago, when I didn't care about fuel economy, I had a 1987 Cadillac with a built-in MPG gauge.