Is the MAP sensor on an ODB I Honda a variable frequency type, or just variable voltage? I'd guess variable voltage, since the S/V-AFC hack works...If so, I found a neat-o set up. Not as good as AFC, but about $300 cheaper http://www.autospeed.com/A_0008/page1.html?src=twr

Possibly one of the best web sites I've ever seen...

 

That is a neat article! It's pretty much doing what the VAFC does for us but with more bling blingyness so technically you could get some DSM 450's and some pots and be done with your FMU setup for less than $75!

I really liked where it talked about disconnecting the O2 wo stay in open loop to calibrate the pots!!!!!!!! That is the answer I was looking for in my "calibrating a modified fuel system" thread.

Great find Ion!

 

Bling Bling? I'd say the VAFC has more bling...fancy vacuum flourescent display, hehe...I honestly don't want one of those (visible) in my car...very ostentatious and asking to get stolen...
The thing that sucks in the article is that it might work with a "variable frequency" type MAP sensor...I'm not sure what the honda is, since I don't have an oscilloscope, heh. I think I'm gonna take a gamble and try to wire it up when I get my 450's...anyone know what type it is, for sure?

As a sidenote...I'm going to get the "audiophile grade" pots made by Alps(they make the crossfaders/pots in all the good mixers) so that I'll be able to REALLY tweak it, and they only cost $2.99 each at the shack...so, I'm thinkin for about $15, I'll have a crude VAFC in a case

Another aside...I think I'm going to make the EGT gauge they have in there...if you follow the link to the company that makes the chips, you can merely say you're part of a firm and get two of the chips for free...I did that with another company to get some chips to make an A/F meter (though I still haven't finished it!)
Damn, I get excited about DIY ****. heh


[Modified by ion_four, 8:29 PM 4/20/2002]

 

I'm almost positive that our MAP sensors are variable voltage. They work on a 0-5V scale. That's why they're so easy to manipulate.

I was thinking more about tuning by disconnecting the O2 and DUH!!! You can't just disconnect the O2, you have to still give it 5V and report back to the A/F gauge. Now I am thinking about putting a toggle switch in-line with the O2 signal just before the ECU, after where the A/F taps in. That way you could just flip a switch and be in instant open loop and tune the entire RPM while cruising, leaving WOT tuning to a wideband on a dyno.

 

Cool, I think that I'm going to have to go for that when I have time in a couple weeks...I was just under my car trying to get to the oil pressure sender for the 'oh-****' light, and I guess you have to take off the filter? I just put Mobil 1 in last weekend...and am a cheap bastard...any idea what the fitting size is for that? I need to buy a T.

 

Ion-four,
Thanks for posting up that link. It's interesting and i'm thinking of attempting it instead of the AFC-DSM method, but i have a question you or someone else may be able to answer.
The afc allows you to richen fuel at higher RPMs. Is it really necessary to change that 10% within the RPM range with DSM 450s on an LS T3 boosting at 9 or 10 psi? If the ECU can adjust it automatically, i want to try the method stated in the link. Thanks for reading

 

I have found my narrow throttle adjustments and wide throttle curve adjustments to be pretty stable. IE my narrow throttle curve takes out -25% +- 3-5% and my wide throttle curve takes out -40% +- 3-5%. This 3-5% deviation on the wide throttle is based on a wideband dyno session and the 3-5% on my narrow throttle is based on my invention that came to me after reading ION's article.

To tune my narrow throttle I have placed a toggle switch in-line from the O2 signal and the ECU. By flipping it and not letting the ECU see the O2 output I can tune the AFC to where it is stoich at 500 RPM increments. My car seems to like about -25% taken out when in narrow throttle but id varies from RPM to RPM.

 

I've never used an AFC, so I'm not exactly sure how this mod would work with narrow vs. wide open throttle...
I'm not that good with electronics, but I'm trying to think of a REALLY simple circuit that would let you have different adjustments for for high/low rpm or no-boost/boost...any thoughts? I was thinking something that might use a voltage limiting circuit(diode?) to give a certain resistance when the original MAP signal is at a certain level and then bypass that resistance and give less resistance at a higher MAP voltage, ie. less vacuum, more boost. Any Electrical Engineer types wanna throw me a bone?

I'd think this mod would allow the honda MAP to see the boost and not throw a code, right?

To me this seems like it could be really great, since it can save you $300 and is probably ~90% as good as the AFC, but even if it isn't, it'll let you run some boost!

 

I'd just like to say how much I love Autospeed.com, again. They have some really great DIY articles...intake air temp meter, EGT meter...they also have kits for sale on there...There's a turbo timer kit with case for I think $16(American, not $30something Australian) that comes with a case and everything!!!So, that's gettin ordered real soon. It won't say something fancy on it, but at more than a hundred less than the cheapest prebuilt, I can deal. Serious, check out the site, really addictive.(I should be studying for finals next week!!!!)

EDIT: Alright, I'm a post-*****...So, is this hack all that the greddy blue box does? Without ever having seen one, I'd almost bet a nut it is. It just hooks up to the MAP wires, right?


[Modified by ion_four, 9:53 PM 5/5/2002]

 

has anyone ever had success with what is discussed in this link

http://www.autospeed.com/A_0008/page1.html?src=twr

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ion_four &raquo;</TD></TR><TR><TD CLASS="quote">&lt;BLOCKQUOTE&gt;quote:&lt;HR&gt;Th at is a neat article! &lt;IMG As a sidenote...I'm going to get the "audiophile grade" pots made by Alps(they make the crossfaders/pots in all the good mixers) so that I'll be able to REALLY


[Modified by ion_four, 8:29 PM 4/20/2002]</TD></TR></TABLE>

Make sure the pots you get are linear - most stuff for audio is going to be logorithmic taper (or sometimes called audio taper.)

Volume and level controls will be log taper, not sure of the others.

 

this looks very similiar to filetofit's old map-hack circuit. anyways, keep us updated. i'd like to see how it turns out. to great research