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Old 08-21-2008, 01:30 PM   #1
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DPFI Love.

Hey guy's. My car is a 1990 Civic STD Hatch. This means my car is equipped with the inferior Dual Port Fuel Injection (DPFI) System instead of a superior Multi Port (MPFI) System.

Most people would be quick to suggest a MPFI swap but I want to keep it REAL! After all I'm pleased with my average but there are some things that I am trying to learn about my car that will squeeze just a little more out of her than I am now. Any advice from personal experience would be appreciated. I'm using a STD 4-speed so I understand that there may be some differences with an HF or DX 5-speed transmission:

1. I've just started the P&G method on this current tank of gas. At 50mph (2300rpm) I'll accelerate to 65mph (3000rpm) using cruise control (I installed the Audiovox CCS100). Then glide down to 50mph. Any experience with P&G?

2. I only P&G on flat or downhill grades. On slight uphill grades I'll cruise at 50mph (2300rpms). Does anyone else find a better "Butter Zone" when running on a consistent cruise?

3. Light Throttle Low Rpms seem to work well. Right around 2250rpm is the suggested shift point on the STD according to the owner's manual but I think a little lower works better.

I also just found out I don't have a D15B2... the STD's came with a D15B1. Essentially a D15B2 DX engine with a milder camshaft, a restrictor plate under the DPFI, and an air flow restrictor inside the DPFI unit. I wonder what those restrictor plates do for FE?

My peak torque is also 83 ft lbs @ 3000rpm instead of the D15b2's 89 ft lbs @ 4500 rpms. I wonder what my torque curve does after 3k and if I should "Pulse" a little higher.

I'd love to see what other DPFI'ers have figured out with their cars. Even if you have a 5-Speed tranny or an HF Tranny on your DX, lets hear what you gotta say ... After all there's not a lot of DPFI love out there. But now lets turn that tide!
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Old 08-21-2008, 01:43 PM   #2
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Here's the discussion we've had so far in PM's:

Quote:
Originally Posted by aalb1
Do you know your approximate "sweet spot" on your d15b2? I assume your still using dpfi right? I'd like to stick with my stock setup and don't fully feel the need to convert it to mpfi. Unfortunately I'm having a hard time figuring out where the sweet spot may be.

Also have any other driving tips? there's not too much DPFI love out there.
Sweet spot? Not sure what you mean by that.

Yep, still using DPFI injection and an HF transmission. You're right about not much DPFI love being out there. I was going to convert to MPFI, but was getting good enough economy with DPFI, I decided to not invest.

Driving tips...let's see. Low RPM's, low throttle input - those add up to slow acceleration and less fuel consumption. It's a balance though, because if there is any positive grade in the road, you can get behind the power curve and not be able to accelerate. With the HF transmission I typically shift between 1750 and 2250 RPM. Learn to read the traffic lights on your normal route - the cross walk signals can help indicate if a light is about to turn red. I coast with the engine off a fair amount, and turn the car off at red lights.

Best of luck.
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Old 08-21-2008, 02:35 PM   #3
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In my '88 CRX DX auto, I'm getting mid to high 40's for my highway mpg while cruising at 3200-3500 rpm (70-75 mph roughly). I tried dropping to 2800-3000 rpm and dropped into the low 40's in spite of losing 6000 ft altitude over the course of a 150 mile drive and having less cargo in the car.... Go figure. I can't tell you right off the bat if I've got a d15b1 or b2 since I don't know the difference, but for sure my engine is more efficient at higher rpm (but still light throttle).

I can't tell you much about P&G. I just drive like I've got an egg under my right foot and it serves me well enough. But I'm considering swapping to MPFI since some of my potential future plans will require it anyway.
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Old 08-21-2008, 07:02 PM   #4
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Quote:
Originally Posted by aalb1 View Post
I also just found out I don't have a D15B2... the STD's came with a D15B1. Essentially a D15B2 DX engine with a milder camshaft, a restrictor plate under the DPFI, and an air flow restrictor inside the DPFI unit. I wonder what those restrictor plates do for FE?
The restrictor plate helps a lot. I just put it in my b2 engine and it runs much smoother, both in the low rpm and high. You can really tell the difference at highway speed. It makes the drive much more relaxing. As far as mpg... look at my gas log. I have one tank with the restrictor plate and it helped a lot.

I was amped up about doing a mpfi but I think there is hidden potential with this set up.

As far as tranny goes I would definetly dump that 4 speed. The fun thing about Honda is that there are so many trannys out there with different gear ratios you can make any kind of hybrid tranny you want. I made a hybrid tranny and it was pretty simple.
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Old 08-22-2008, 05:00 AM   #5
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Quote:
Originally Posted by civic lover View Post

As far as tranny goes I would definetly dump that 4 speed. The fun thing about Honda is that there are so many trannys out there with different gear ratios you can make any kind of hybrid tranny you want. I made a hybrid tranny and it was pretty simple.
So what's your hybrid tranny looking like? If i'm not mistaken the four speed has all the same gear ratio's as the HF minus the 5th gear and also a different final drive.

Everyone will be quick to suggest that the four speed is inferior... it only seems logical. And I was thinking of swapping it out for an HF tranny but read how someone on hear did the same with their STD and were disappointed with the results. Why drop the tranny if I don't have to. Maybe if I was 25 years old and I wanted to get my hands greasy. I'm at an age now where I only work on cars if I have to... by the way now I'm 26
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Old 08-22-2008, 02:28 PM   #6
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I'm 33 and I still get my hands dirty.....

I'll probably tear into it this weekend, but for my CRX, I've got a DX 5 speed and an HF final drive. With my tires (185 50 r16s), that will allow me to cruise in 4th at around 3200 rpm on the highway (75 mph) and 2600 in 5th. Seems like a good setup to start with, but time will tell.
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Old 08-22-2008, 04:12 PM   #7
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So how do I tell the difference between a D15b1 and a D15b2? I have three '91 Civics - a DX sedan, an LX sedan and a DX HB. They are all 5 spds and everything is stock. The LX sedan runs great but really seems to lack "pep" relative to my DX sedan. (Am I remembering right that the LX 5 spd has different gears that the DX? That could be part of it.)

DPFI is fine with me. I can't complain. My DX sedan now has 270k on it.

Bill
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Old 08-22-2008, 04:24 PM   #8
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37 here, and will get dirty **When required** I've stopped doing my own oil changes years ago because by the time I buy 5 quarts of synthetic oil and a filter I've hit the price for Wal-Mart to do a Mobil1 oil change, and I don't have to get dirty... When I told my brother in law what they charged me to do an oil change on my truck he mentally added up the cost of the filter and 5 quarts oil... He determined that they changed the oil for free, which is the conclusion that I came to years ago. Why get dirty when once you buy the oil they will change it for free?
work smarter, not harder.
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Old 08-22-2008, 05:06 PM   #9
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Quote:
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So how do I tell the difference between a D15b1 and a D15b2? I have three '91 Civics - a DX sedan, an LX sedan and a DX HB. They are all 5 spds and everything is stock. The LX sedan runs great but really seems to lack "pep" relative to my DX sedan. (Am I remembering right that the LX 5 spd has different gears that the DX? That could be part of it.)

DPFI is fine with me. I can't complain. My DX sedan now has 270k on it.

Bill
the only way you can tell is by looking at the engine code. The lx has the same gearing as the dx, unless your dx hb is a 4 spd.
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Old 08-22-2008, 05:57 PM   #10
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Quote:
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I'm 33 and I still get my hands dirty.....
No need to unzip our pants and have a measuring contest. I'm just saying why get my hands dirty for nothing? Someone on this board bought and swapped an HF tranny into their STD and were very disappointed with the results. I'd only be willing to do this if the HF tranny will net me better gains and for my commute I leary it won't.


Any critique on my P&G methods below?
Quote:
Originally Posted by aalb1 View Post
1. I've just started the P&G method on this current tank of gas. At 50mph (2300rpm) I'll accelerate to 65mph (3000rpm) using cruise control (I installed the Audiovox CCS100). Then glide down to 50mph. Any experience with P&G?

2. I only P&G on flat or downhill grades. On slight uphill grades I'll cruise at 50mph (2300rpms). Does anyone else find a better "Butter Zone" when running on a consistent cruise?
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