i came across a p72 recently and am considering doing an obd1 conversion on my 99 lude base. from what i gather, the p72 will cause my car to run lean in comparison with the p5p i currently have. i do however have a VAFC to correct the lean problem. what i really want to know is has anyone here done this conversion and what was the outcome? what are the problems i can expect and were the any gains noticeable? also, if i am correct the p72 is set up for peak/hold injectors whereas the p5p is saturated. will this cause a major conflict and is this the cause of the leaning out problem? if so, couldnt i change the injectors to the 310s from a 4th gen (which i think are peak/hold) to solve this problem? if it will help any, here are the mods i have performed as of now: AEM CAI, Greddy EVO cat-back, DC header and the VAFC. any input here would be appreciated.

 

Ahhh finally someone that has done their research first before posting.

You don't need to change injectors. All Honda ecus send injector pulses the same way. As long as your resistors match your injectors, which they do since they aren't changing.

Your main issue is fuel. I have not seen results of V-AFC +P72 but I'm hoping you can make some good out of it. Do not run the P72 until you are on the dyno with a wide band O2. With the V-AFC:

1) Set VTEC to 5000
2) Add +10-15% fuel across the board
3) Tune from there.

Last thing you want to do is grenade your engine, spend the time on the dyno and you should get great results.

 

i believe the P72 is setup for saturated injectors, which are used on the 94-95 integra... so you shouldnt need a resistor setup.

one of the big attractions for the P72 swap... injectors work, IAB capability, and knock sensor capability.

 

That does not matter. Even if his injectors were peak and holds with an external resistor box, he would not have to do anything if he swaps the ecu.

 

what about timing issues? do you have your car tuned on the v-afc w/current setup to compare? the v-afc does not change timing at all does it? the p72 doesn't swtich to vtec till like 6k, i think, so even useing the v-afc wont timing be off from 5 or where ever you end up w/vtec(4.6-4.8 is usally best)-6k be off...if you already have v-afc try it and post results, if not get a hondata s100 w/the p72.

 

Timing won't change...so yeah that's why I wasn't sure if you could really get all the benefits with just a v-afc

I'f you look at the side by side comparison by Import review,


If you raise VTEC to 5000 I don't see any real problems...then just tune the fuel..

GS-R engages around 4500


[Modified by satan_srv, 4:06 PM 11/29/2002]


[Modified by satan_srv, 4:08 PM 11/29/2002]

 

yeah, the timing issue crossed my mind too. but my next item on the list is the MSD digital 6+. then ill work on the fuel system and maybe add a bottle later on. right now im working on a collection of trannys to build a custom geared one. and thanks for all the help too. ill post the results when i get the ecu swap done.

 

That MSD is a waste of money on N/A. Good when you have the nitrous system, but useless until then really..

 

please elaborate. i would think having more control over your timing would be a good thing. especially when doing the ecu swap i am considering. not to mention the convenience of the 2 step rev limiter. i understand it will be of more use after the n2o is added but i cant see how it would be a waste of money.

 

What control over ignition timing are you getting? Even with the ecu swap you won't be able to advance/retard static ignition timing unless you swap an OBDI distributor and rewire the CKP sensor wiring to there. Then after that, timing is still controlled by the ecu until you hondata chip it.

The MSD will make the ignition more responsive...but it won't make any noticeable power...read the install/article by my friend Mark on our site http://www.hondaprelude.to/install_msd.html


[Modified by satan_srv, 1:00 AM 12/3/2002]

 

im getting hondata too and to run it on mine i run off the p72 ecu. so i can keep my peak hold injectors too right..

 

P72 normally runs saturated injectors...but it doesn't matter Honda ecu's all work the same way. Just use your injector resistor box and peak and holds and it will work fine..

I have a p72 on RC pnh injectors...no problems...

 

Get a hondata system and your set. You can control the fuel, ignition, vtec, rev limiters. Its the ****. I got one myself with an obd1 conversion.

 

p28 vs p72.

is it even worth it to do the p72? I mean. it's only the secondaries that the p72 control..which the p28 doesnt.

can a difference be felt between the p28 and p72?

 

well, not 100% on this, but im sure the fuel maps would be different. and as discussed above, the timing also. from what i understand the p72 or p13 are the best options for a prelude obd1 conversion.

yeah, after doing a little more research, i have decided that the MSD isnt gonna realy be of any help till i get the N2O on it. that money can be well spent on something else like the adapter cable i need for obd1 conversion and a test pipe. which brings me to another question. since im reverting to obd1, the second o2 sensor will be unused. correct? so can i just cut the wires or tie the o2 up somewhere incase i decide to go back to obd2. and where would be the best/cheapest place to find the cable i need for obd1 conversion. i know skunk2 sells them, but there has got to be somwhere that sells them for under $200.

 

Just leave it where it is...what are you gonna do, leave a hole in your exhaust?