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Vrooom PSHHHH
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Discussion Starter · #1 ·
I've been reading up a bit on what a P28 can and can't do and just wanted to get some conformation.


  • No EVAP?
  • EGR?
    • Will blocking this off cause any problems?
    • With it still installed, is it locked open or closed? Even with a hondata IM gasket and some coolant bypass stuff, my IM is getting really hot so I'm thinking it's still letting exhaust gasses circulate
  • No immobilizer obviously.
  • No IABs so I have the vacuum line for that hooked up directly to the IM so it opens based on throttle position.
anything else I'm missing? My S2000 TB doesnt have an evap port so I dont care if that's not working. Just trying to consolidate everything because I dont want to have parts that arent working anymore just cluttering up the enguine bay :)
 

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i kinda have the same question, but not to thread jack, but how are people installing their p28s in there car? becasue the p28 is a rectangle and the bb6 ecu is a square and it looks like you have to cut stuff to make the p28 fit.. or am i retarded and missing something?!? lol
 

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i kinda have the same question, but not to thread jack, but how are people installing their p28s in there car? becasue the p28 is a rectangle and the bb6 ecu is a square and it looks like you have to cut stuff to make the p28 fit.. or am i retarded and missing something?!? lol
you need an OBD1 to OBD2 conversion harness.

Sorry, O.P. don't know your answer.
 

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^ ? ours 5th gen is OBD2a. the p28 is OBD1. or am I drunk?

This one will do the trick


Make urself a favour, dont cut any wires. spend $90 on this instead and save alot of time and u'll get it done correctly.

there's different harness, the one u want is called. OBD2a -> OBD1
 

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I've been reading up a bit on what a P28 can and can't do and just wanted to get some conformation.


  • No EVAP?
  • EGR?
    • Will blocking this off cause any problems?
    • With it still installed, is it locked open or closed? Even with a hondata IM gasket and some coolant bypass stuff, my IM is getting really hot so I'm thinking it's still letting exhaust gasses circulate
  • No immobilizer obviously.
  • No IABs so I have the vacuum line for that hooked up directly to the IM so it opens based on throttle position.
anything else I'm missing? My S2000 TB doesnt have an evap port so I dont care if that's not working. Just trying to consolidate everything because I dont want to have parts that arent working anymore just cluttering up the enguine bay :)
p28 does still operate the EVAP. so if you leave it connected, it will still operate normally. but if you disconnect it, it will not throw a trouble code of CEL, so thats nice too.
egr is no longer controlled, and it will leave the egr valve closed at all times. i do however recommend getting an egr blockoff plate still, which i very highly recommend getting from rosko racing who makes the highest quality and best looking kit out there, for barely any higher cost than the cheapy crappy ebay kits.

and you are correct about the immobilizer and iab's
 

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i kinda have the same question, but not to thread jack, but how are people installing their p28s in there car? becasue the p28 is a rectangle and the bb6 ecu is a square and it looks like you have to cut stuff to make the p28 fit.. or am i retarded and missing something?!? lol
to the people that answered this above, he's not referring to the ecu plugs, he's referring to the way the ecu mounts to the kickplate.

yes, the p28 is different sized and shaped than the stock ecu, so it wont bolt directly to the kickplate, and iirc one of the brackets does get in the way so you do have to chop something off the plate for the ecu to fit properly behind it whether it's just laid back there or bolted to it
usually what i do is just wrap the ecu in some thin foam, and lay it behind the kickplate and bolt the plate back in place. or you can drill new holes in the plate and put bolts/nuts through the plate to hold the ecu to it.

but yeah, i'm a dealer for boomslang, so i can sell their conversion harnesses at discount prices. my prices on all of their products are $10 cheaper than if bought directly from them. so for an obd2a-obd1 conversion harness, my price is $90 shipped. directly from boomslang is $100 shipped
 

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I haven't found that the P28 operates EVAP normally. It does operate it though.
 

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Thanks moto, yeah i already have a conversion harness. but i thats what i though i was going to have to do, i just wanted to ask b4 i cut shit apart.. lol
but thanks alot:cool:
 

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Vrooom PSHHHH
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Discussion Starter · #10 ·
p28 does still operate the EVAP. so if you leave it connected, it will still operate normally. but if you disconnect it, it will not throw a trouble code of CEL, so thats nice too.
egr is no longer controlled, and it will leave the egr valve closed at all times. i do however recommend getting an egr blockoff plate still, which i very highly recommend getting from rosko racing who makes the highest quality and best looking kit out there, for barely any higher cost than the cheapy crappy ebay kits.

and you are correct about the immobilizer and iab's
So I checked out my old TB and the evap port on that one enters the TB right in front of the throttle plate. Since the S2k TB has no EVAP port, would it still work if I extended the line and hooked it up to a port on the IM plenum?
 

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p28 does still operate the EVAP. so if you leave it connected, it will still operate normally. but if you disconnect it, it will not throw a trouble code of CEL, so thats nice too.
egr is no longer controlled, and it will leave the egr valve closed at all times. i do however recommend getting an egr blockoff plate still, which i very highly recommend getting from rosko racing who makes the highest quality and best looking kit out there, for barely any higher cost than the cheapy crappy ebay kits.

and you are correct about the immobilizer and iab's
Really??

Wierd... My immobilizer still works... perfect!
 

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Vrooom PSHHHH
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Discussion Starter · #13 ·

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So I checked out my old TB and the evap port on that one enters the TB right in front of the throttle plate. Since the S2k TB has no EVAP port, would it still work if I extended the line and hooked it up to a port on the IM plenum?
actually, it wouldnt work that well, cuz it would be under vacuum when the plenum is in vacuum, causing the solenoid to open at times when it shouldnt be.
the reason they put the evap port before the throttle plate is so it sees ambient pressure at all times. but close enough to the TB plate so that when it does purge, its guaranteed to enter the intake mani, due to the fact that it is only supposed to purge when at part throttle, and never at full throttle or zero throttle
you'd be better off just putting a nipple on your intake pipe somewhere immediately before the TB
 

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Really??

Wierd... My immobilizer still works... perfect!
actually the immobilizer only cuts off the starter but it cannot disable the fuel and spark like your stock ECU can so the car can still be push started when a P28 is in place..

also with a P28 you will loose the knocksensor as it lacks the circuit to make it work along with the IAB that's why the best ECU choice is a P72 or if the person doing the reprogramming is good at it and knows what he's doing and not just bootleg chips. he can add the IAB into a P28 or VTEC into a P06,P08,P74,P75 ECU and even the knock board making it into a P72.
 

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actually the immobilizer only cuts off the starter but it cannot disable the fuel and spark like your stock ECU can so the car can still be push started when a P28 is in place..

also with a P28 you will loose the knocksensor as it lacks the circuit to make it work along with the IAB that's why the best ECU choice is a P72 or if the person doing the reprogramming is good at it and knows what he's doing and not just bootleg chips. he can add the IAB into a P28 or VTEC into a P06,P08,P74,P75 ECU and even the knock board making it into a P72.
yeah but the problem with the p72 is the high cam maps only have half the tuning points as any other vtec ecu, making for nowhere near as accurate of a tune in high cam (aka in vtec)
that plus the code base of p72's is very quirky and doesnt always work properly, with any system
also, the knock board in p72's only works in 92-96 ludes, it doesnt work properly with 97+ ludes; different knock frequencies and different sensors
 

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actually, it wouldnt work that well, cuz it would be under vacuum when the plenum is in vacuum, causing the solenoid to open at times when it shouldnt be.
the reason they put the evap port before the throttle plate is so it sees ambient pressure at all times. but close enough to the TB plate so that when it does purge, its guaranteed to enter the intake mani, due to the fact that it is only supposed to purge when at part throttle, and never at full throttle or zero throttle
you'd be better off just putting a nipple on your intake pipe somewhere immediately before the TB
It doesn't work that well anyway with a P28. In terms of drivability it would be best left not connected.


I wouldn't use a P72 knock board with any H22.
 

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yeah but the problem with the p72 is the high cam maps only have half the tuning points as any other vtec ecu, making for nowhere near as accurate of a tune in high cam (aka in vtec)
that plus the code base of p72's is very quirky and doesnt always work properly, with any system
also, the knock board in p72's only works in 92-96 ludes, it doesnt work properly with 97+ ludes; different knock frequencies and different sensors
thats strage as from what I understand any of the P06,P08,P28,P54,P30,P72,P75 codes are all interchangeable into each ECU as the hardware is the same as I have converted P06 into a P28 and P72 with the knock disabled and ran fine as the P72 code 272 may have less tuning points you can load another code in like a P30 but of course the cost of the P72 as for the knock sensor they can be swapped out as I would feel better that its there but it's just a choice.
 
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