I have a 92 GSR with a B18c.out of a 94 GSR. Went from B17 to B16 to now B18c. I am currently running a p28 in it with No problems and vtec engages at 5600 rms which is the same ecu i used for my B16. I'm wanting to switch to a virgin p72 ecu bc it was with the B18C.

Today I put in a p72 and the vtec will not engage. We took the p72 and put it in a prelude and the vtec engages at 4500 rpm without a problem.... Put the p28 back in and it works fine.

For some reason the vtec wont engage with the p72 but works with the p28......

Both ECUs are obd1.
My knock sensor is there and hooked up. What could be causing this???

 

is your p28 chipped or stock? Vtec isn't something you always "hear" so maybe since the p72 is a stock map, you're having trouble "hearing" it. Are you running the stock intake manifold on the b18c?

 

The P28 is chipped, but to be honest with you I have no clue what kind of chip. The P72 is stock (virgin). The intake manifold as of right now is STOCK, but I will 100% be getting a skunk2 IM withing a month. Also read today that the P72 is kind of pointless once you upgrade to the SKUNK2 IM, bc the P72 still acts as if it has butterflies. Has anyone head anything about that also??

 

A stock gsr with its low vtec crossover of 4400 is almost never heard or felt. Its pretty smooth and you will hardly ever know it came on. What you will notice is the butterflies opening just before 6k. If vtec didnt come on i would guess the ecu will know and not activate the butterflies, could be an indicator. Someone will probably correct me there. Im used to my gsr so i could usually tell when vtec was on but like i said its incredibly slight if u notice anything. Vtec obviously works on the motor since it does with the other ecu and you say the p72 works on a prelude so id guess what im suggesting is true. You just arent feeling it. This is the way honda built the gsr. I think i read recently that the prelude has some type of butterfly system also and it comes on before vtec so you might be noticing this instead. Again someone will have to correct me here.

Your p72 will not matter once u change the manifold. You can run the stock ecu but better off with ur p28 if its a better map then the stock p72 and the higher vtec crossover will be better. When i say you can run the stock ecu i mean only as a temporary cuz its a poor choice to keep with a skunk2.

 

So youre saying it would be better to stick with the P28 with the Skunk2 IM? I was thinking it would be better with the P72 because of the early Vtec engagement. The P28 ECU isnt for the gsr so im not quite sure how my butterflies are working right now. Is it possible that its not even engaging the butterflies? The only reason I was wanting to go with the P72 is because I was thinking it would give me better performance since I have the B18c gsr in the car. (Im still trying to learn all of this)

 

Another question is how can I find out WTH kind of map i have on my P28 or what its chipped for/with?

 

You need a chip burner to read what's on the chip. Depending which software was used to burn. You can hear your vtec crossover on the p28 because the transaction is not smooth or has been changed. Yet you wouldn't know since you have no idea what map is on the chip. Vtec crossovers should be smooth. Loudness does nothing.

 

I actually don't hear mine at all right now but I feel it open up at 5600, seems like the car just starts pulling harder once it engages. kind of a stupid question.... Chip burner... Something I can buy?

 

Yes. Heres the Xenecron BURN2, its a usb chip burner that plugs into your laptop.

http://www.xenocron.com/chip-burner-...7565244f926eca

 

Only reason i said the p28 is better with the S2 manifold is the higher vtec crossover. Since we dont know what is actually on that p28 no one can give u a real answer on that. Its completely possible the p28 was setup with a higher vtec but still work butterflies but still this is something we dont know. Im in a similar situation with a p28 i have but i know for sure it was running a gsr with a skunk manifold on. I dont know if its a gsr map, custom or type r.

You should probably just use the p72 until you swap the manifold then decide to use the p28 as is until you tune or get a diff ecu thats for a gsr running a skunk 2 manifold. Like i said earlier, i believe your vtec is coming on at 4400 and u just cant tell and right before 6k its the butterflies opening up. Dont mistake that for vtec. If you want to confirm that it is the butterflies opening up on the p72 you can disable them and if u no longer feel/hear something at that point then it is the butterfly operation.

Looking back you never said if you heard or felt anything at all with the p72. So you dont get any change into the higher rpms with that ecu at all? Oh and you wont hear much at all without an intake.

Sounds like youre not that knowledgeable about this stuff (like myself!). Make friends with the search button. Similar topics on all subjects here have been discussed and ive learned a lot myself by reading them. Googling stuff will pull up results from other discussion boards too.

 

With the P72 i hear nothing. Would I benefit from getting a Hondata S200 for the car? And another stupid question..... What are the benefits of having a Hondata S200?

 

I say wait on the hondata...especially if your motor is stock. For right now, stick with the p72 ecu since you're using the stock intake manifold and don't worry about "not hearing vtec". The "pull" or "extra power" you're feeling at 5700 rpm is the secondary butterflies in the stock manifold opening up. As everyone has stated, we don't know what program you're running so if you're really curious, take your car or ecu to a tuner and have him download the map and look at the values from there. OR, if you got your ecu off of ebay or wherever, open up the ecu and you'll see in the lower corner a chip with a sticker label on it. Sometimes tuners label the programs if its a "generic ebay chip" ie mugen, skunk2, etc. Every motor acts differently based on the mods, how it was built etc. When I rebuilt my GSR, the tuner tried different vtec x over points and we found that at 6k, it was the smoothest transition in power with the most power gains.

At the very least, you could hit up your local tuner or phearable.net to have him send you a base map to run in the mean time, or even after you have your skunk2 single stage manifold. If your car is running right, leave the p72 in there. You'll get better gas mileage, your stock manifold will work properly, and you don't have to worry about running rich with a chipped ecu that was't made for your set up. I know all of this info because I used to chip ecu's for the HT community a few years back.

 

Thats the thing, I dont have a P72. I only have my chipped P28. I tried out someones P72 bc I was going to trade, but didnt feel any difference and the VTEC feeling went away with the P72 so I didnt go through with the trade. So i have a chipped P28 right now that kicks on at 5600. Im gonna have a SKUNK2 or BLOX (cant decide which one to go with), CAI, No CATs, and possibly going to do my exhaust, i just dont want to have a rattle can. Is Hondata just a programable chip???

Truth be said my brother and I are kind of new to the honda world, and he has a 92 prelude with a JDM H22. Im trying to get my car ready to be able to take him on the track 1/4 mile. As of right now on the street we are even up to thrid gear, but once thrid gear kicks in he smokes me. Im def getting the Skunk2 or BLOX, and already have the CAI. In the far future i want to boost or put a supercharger but thats atleast a year out for now.