filetofit

So I finally got the custom chip burned for my ECU that incorporates 450cc injector fueling and timing retard for boost up to 11 psi using the stock MAP sensor. And I'll be damned it it didn't work.

It took me a while because first I had to replace the pistons that had cracked ring lands from before I chipped the ECU and wasn't running any timing retard. Then I had a bad chip that wouldn't even run the car. Now it runs so smooth. Started up the first time, no CELs.

Anyone else interested in being a guinea pig? If you are interested I'll put you in touch with the guy who does custom chip burns and I'll help you mod the stock maps for boost (or I'll do it for a small fee, maybe $20). You'll also need to wire a potentiometer in line with the MAP sensor ($2 at Radioshack) and of course you'll need 450cc injectors.

Oh yeah I forgot obd0 and obd1 only, the specific ECUs this works on I'll post later as I've got to ask the guy who did the chip burn which one's he can do.

The setup I'm running is an LS/Vtec t3/t04b I believe the A/R is 0.50 on the compressor, 9 psi intercooled, Gen 1 b16a head on a b18a block, PR3 ECU, disabled closed loop, crower cams, stock bore, JE spherical dish pistons CR = 9.0, stock rods.


[Modified by filetofit, 12:45 AM 1/2/2003]

BudaKai

Does this mod have any limitations on compression or boost levels?

Glad you finally got it to work . What did you use to write your maps? Can you just use the fuel maps and leave out the ignition? I have a spare PR3 I'd like to try it on, but can I change the maps if I need to update them?

Sorry I've been waiting to hear some progress on your project...

UberTeg

Why do you need a potentimeter? Why not just use a regular resistor?

filetofit

With the stock MAP sensor boost is limited to 11 psi. This method could be used with a 3 bar MAP sensor to boost up to 30 psi but the vacuum part of the fuel and timing maps would be limited to about 5 columns which is quite coarse. Around the town driveability might be rougher than stock.

Compression ratio doesn't matter as long as the maps that you start with are tuned for that CR.

Yes I suppose you could just mod the fuel maps but I don't know why you would do that.

Changing the maps would involve burning a new chip. Just like another commonly used system.

Oh, and yes I suppose you could create a voltage divider out of resistors rather than a pot but the pot allows for tweaking.


[Modified by filetofit, 1:48 AM 1/2/2003]

kenbdSi

sounds good. Might get back with you on that.

SiRkid

good job!

BudaKai

Sorry, I have ideas just floating around my head all the time so sometimes I ask strange questions.
Such as this one.
Do you have the voltage maps for the various sensors; o2, MAP, crank sensor, etc, etc?
Sorry to ask I can find them anywhere and I can't get them from work. (yippie, I work for Honda!)

filetofit

not quite sure what you mean by a voltage map. But the voltage range for the MAP sensor is 0.0 to 5.0 volts with 3.0-3.1 volts being the limit at which the ECU will throw a CEL. The range for the o2 sensor is 0.0 to 1.0 volts. Crank sensor I have no idea. You could put your voltmeter on AC and measure the voltage on the crank sensor at 3600 rpm and multiply by 1.414 and that should get you close to the max crank sensor voltage.

JalopySiR

I am interested in this setup as well. I am currently running a cammed B20 right now, that will be boosted by this summer. I am running a 91 LS ECU, but my AFC has dyno tuned cam settings on it. Is there some mathematical magic you could work on these settings, melding them with some 450cc settings, so I don't lose them? Or, would the burn be of a stock LS program, albiet with 450cc tune and boost timing retard, and I can further refine with the AFC? Also, what is the retard per pound? User defined? Please get back to me on this, as I am VERY interested. Hit me up with an IM. Thanks, and keep up the good work. The Honda-Tech community does appreciate it.

Joseph Davis

Your hack will work, I've been running something similar since June. Due to how the MAP represents a dynamic resistance with regard to pressure, you skew the pressure to voltage linearity of the signal slightly. Play with a fixed resistor and a pot in line and see how voltage drop changes if you aren't familiar with the concept.

That being said, the skew is minimal and the resistor based trick will work - and work well. I'm just a high-toned **** bitch, so I levelled the playing field by using an adjustable voltage regulator to drop the referrence voltage going into the MAP down to 3 volts, which tweaks from the other side of the sensor and does not contaminate the signal.

I'm glad to see someone else is aware of how the ignition maps get fucked with S-AFC hack and MAP hack boost setups, that you're in full ignition advance during transition to boost as well as low boost with the stock Honda ROM. I've gotten into a few arguments with people who have been told otherwise (siting H-T as their source), it's good to see someone who knows what they are talking about posting here.

That's strange... I've only seen 88-91 ones go to 9.25 and 92+ ones go to 10.65. The 11 psi (or 11.3 psi Hondata claim) one is still mythical in my world. :D

FYI, I think calibrating for the GM 2 bar sensor (14.5 psi) is a good thing, as it does not alter the resolution of the stock Honda maps much - even though the sensors are physically limited to ~9-10 psi by design, the voltage scale they are on has 5 volts = 11.8 psi.

As far as a GM 3 bar... the 88-91 Honda ECUs have 255 points of adjustability compared to the Accel DFI's 256 points - and the Honda ECU interpolates the exact fuel/ignition curve instead of stepping it in increments like the DFI does. It still has potential, but just be careful, eh?

I have both PM6 (88-91 Si) and PR4 (90-91 LS) .bins with 1.0 per psi retards up on the PGMFI Forum, and a half dozen others squirrelled on my harddrive. Anyone surfing that way who's interested should go through the newbie threads, hell, every single post there, before asking any questions outside of email (hint: email newbie questions). It is very much a tech site, and they get pissy about signal:noise ratio.

BudaKai

I meant maps as in what the resolution would be with each device. Sorry I couldn't think of the word and my friend and I were calling in mapping because you plotting maps based on voltages. Makes sense now?

Wow that's a pretty technical there J.Davis, but 2 bar is actually 29.4psi...

1 bar = 14.7

Speed PHreak

Good to see you posting J. Davis, nice info.

filetofit

I'm just basing the 11 psi number on the fact that at atmospheric my MAP registers 2.9 volts so (15 psi /2.9 volts) x 2.1 volts = 10.86 psi. I've never actually measured the max voltage put out by the MAP sensor so you could be right and it might top out at 4.5 volts or something like that.

As for the skew, I actually use an op amp circuit to isolate the MAP output before I divide it so the resistance the MAP sensor sees is actually almost infinite. I figure for most people though a voltage divider pot with a R of 10K or so should do the trick I measured the voltage drop across a 100 ohm resistor in series with the MAP sensor once and the input resistance of the ECU works out to be about 100K. So a 10K divider should be large enough to not fry the MAP sensor but small enough so the ECU current draw isn't significant. ALthough hopefully the input resistance of the MAP sensor is <10K (hmm, didn't think of that).

Joseph Davis

No, I'm correct. The first bar of the GM 2 bar is atmospheric pressure, the second takes you to 14.x psi depending on your elevation/atmospheric pressure. Furthermore, 1 bar = 14.5 psi, not 14.7. 14.7 is atmospheric pressure at sea level, more or less, depending on weather.

Stephen, nice to see you too. How's the POSrex's big brother doing?

filetofit, (I think) I recognize you now from the PGMFI Forum; the opamp bit confirms it. I'd love to hear any details you have to give on how things are working out from your angle. It's a shame the hack will be obsolete soon.


[Modified by J. Davis, 5:25 AM 1/3/2003]

JalopySiR

Bump, for informative purposes.

BudaKai

Umm where'd you get that info. It's wrong. BAR is the metric representation of atmospheric pressure. 14.7 Just go ask any German engineer. It is a German measurement. When boosting you never count the starting pressure you count how many PSI or BAR over the starting pressure. So 2 BAR would be 2 BAR over the atmospheric temperature. Stick to computers your better at them. Leave the engineering to the engineers. Otherwise a very informative post except none of you have any idea where your going with any of this do you? I already went through the ECU hacking phase. The stock ECU's can't do much as far as I'm concerned. Especially when I payed $150 to built my own standalone that rivals MoTeC (I'd still love to have a MoTeC with that screen and everything).

BlueShadow

http://www.convert-me.com/en/convert/pressure

1 BAR = 14.5 PSI
1 ATM = 14.7 PSI

1 BAR does not equal 1 ATM

ATM = atmosphere


[Modified by BlueShadow, 1:25 PM 1/3/2003]

Joseph Davis

Thank you, Blue Shadow.

I'd rather give up the computers and stick to the engineering, tzsir. I'm much better at the engineering.

Speed PHreak

Aww I wanted to say it. Just kiddin. My POS needs some big *** injectors. 850-900cc would make me happy. I can't boost over 8psi or rev above 5500 RPM...The power is awesome though

1.8T_EG

great info!!!

Joseph Davis

Sounds like you have the boost you are running tuned in fairly well if your problem is lack of fuel.

I'd up the fuel pressure to about 50 psi and retune the maps so you can rev higher. A quick crushing of the stock regulator in a vise should do the trick


[Modified by J. Davis, 5:53 AM 1/4/2003]

Speed PHreak

Heh, my FJO wideband owns !

Nah, i've got an adj FPR........but I don't think my stock pump would be happy with 50psi and then 8~10psi of boosted rail pressure on top of that ..... I found some 85# injectors for cheap today actaully. I'm gonna lower my static rail pressure to like 30psi so that my fuel pump will flow more volume without have to run so my pressure......even at 30psi on the rail those 85# will still flow like 720cc'rs....... heh heh

Joseph Davis

Very smooth.

I had the stock HF pump fail on me a couple months back, as I was pulling out of the driveway. It only had 220K on it, too, can't Honda build a damn thing right? Pile of import garbage... Anyway, I spent that night after work swapping an LS fuel pump in a gas station parking lot. Had to drop two tanks that night, much fun.

I've been up to 9psi without a problem on mine, but my turbo is a lot smaller. 9 psi with a .42 trim T3 is a lot less fuel requirement than you need.

BudaKai

Umm go enter 1 for your BAR value on that site and hit convert it says it's equal to 1 ATM value I believe that would be 14.7. Nope I think your wrong there with that 14.5 PSI = BAR. 0.9869233 is the exact ATM value. Umm maybe your pump fried because you were pushing to harder than it was designed for. Honda actually made them very nicely if used with-in specifications. A DX pump was designed for a 1.5 liter economy engine...








[Modified by tzsir, 3:09 AM 1/4/2003]

dbman96

I work with european automakers frequently. ANY engineering conversion calculator will convert 1.00 bar to 14.5 psi. If you put in "1 bar" and convert to ATM it may very well say "1 atm" because you're only inputting 1 significant digit, so it can't accurately say that "1 bar" = "0.98639 atm"

"1.00000 bar" however, equals "0.98639 atm" equals 14.5 psi


Regarding your confusion on the 2-bar, 3-bar, whatever MAP sensor... try breaking down that M.A.P. abbreviation. Manifold ABSOLUTE Pressure

Absolute pressure means pressure relative to zero. Not relative to standard atmospheric pressure (that would be gauge pressure). So a 2-bar MAP sensor sitting on your desktop in open air will read 1.02 bar.

It will continue to measure an additional 0.98 bar of BOOST (gauge pressure or pressure above atmospheric) to reach its maximum range of 2 bar.