Thread: OBS Boost prob

ok guys, maybe i'm just a retard, but I've been searching around this OBS forum looking for anything about a boost fooler. I was coming off HWY 5 tonight and hitting the wrap around on-ramp to the 78 east... So some jack&@# in his cobalt decided it was time to cut me off so I gave him a good foot full of the ol shut up button. I wasn't at WOT, but I was probly above 3/4 throttle. The tranny dropped to 2nd doing about 40 I would guess and the rpm spun up to about 3300 and my CEL promptly told me to knock it off. So I backed out, and drove it the rest of the way home, and the CEL stayed on for a few miles then went out. Got home, hooked up the scanner thinking I had the IPR code, but it was p0238. From everything I have seen on here, that is the overboost code.

Now the big Q here is, in overboost on the OBS trucks, does the system defuel like it does on the newer ones? I have heard that it doesn't, it just trips the CEL. Next Q, at what psi does the OBS PCM trip overboost? Last Q, is a boost fooler a necessary addition to my truck?

I had never gotten an overboost code before, and this is the first time that I just jammed the throttle since I did the DIY tymar and 4" straightpipe. Normally if I need to kick it and stick it, I'll spin the turbo up smoothly vice just jamming the throttle. So, I'm not worried about the light or anything, just wondering about those few Q's above. TIA guys!

ok.. i think P0238 is exhaust back press not sure how your getting a overboost i have a 97 an can hit about 44lbs an never get overboost. an the obs trucks supp dont defuel at higher boost i still put in a blow off valve to the map sensor.. i got thur one of the vendors..

yeah, if you put a blowoff valve on the map sensor circuit then you never will get an overboost code because that's a kind of boost fooler. Other guys use just a pressure regulator and choke it off below overboost pressure so that the map sensor doesn't see the high boost condition.

So we don't defuel for sure then? I think you're the second guy I have heard say no, but I have heard people say yes... Guess I'll put in a boost fooler and be done with it... I still need to know what pressure to set my reg at so that the boost fooler is effective

well i just put it on after a few runs didnt think hitting the map sensor with 40+ pounds of boost is any good.. i did run it with out an never notice any difference..

im sure 40 pounds would likely do something crazy haha. I don't really know what these stock turbos are even capable of. I figure topped out they might be just over 20 lbs. But I just need to know what the magic number is to set a boost fooler to so that I don't keep popping my CEL on if I need to get movin.

well if you start running really high boost levels you will jack up the turbo.. or the air will be superheated an not any good for performance.. i would prob say 24 would prob be max just a guess.. i did run a exhaust back presure fooler.. i think its still on there.. to help with that code.. got it thur a vendor if i do some searching i prob could find it..

During live tuning, Joey at Terminator saw his truck defuel starting at 20PSI, but it was not like the SD's do when they get too much boost. A boost valve is not really needed. Talk to Joey and he will explain better.

so OBS' do defuel? I keep getting conflicting answers from everyone I talk to. All I have is a single stage mild chip, stock turbo, diy tymar and a straight pipe. The stock turbo is only capable of mid 20's right? to be clear, the exhaust back-pressure is pressure post turbo in the exhaust system right? Or is it pre-turbo?

The code, P0238- (turbocharger boost sensor a circut high) refers to the MAP sensor reading feeding the PCM. How would EBP work into that at all? I know why I threw the code, it was because I stopped on it and the motor freewheeled on a downshift up to about 3300 r's, hence the turbo overboosting.

The thing I need to know guys, is what is the PSI at which i need to set a regulator on my MAP circuit to make a boost fooler? I'm guessing with my mild tuning and the open intake and exhaust, I might be pushing mid 20's... I know I need gauges and and intercooler, but that's comming in the future. So for the MAP circuit, what PSI do I need to regulate my boost fooler at? Oh and Matty, I'm moving back up to northern california on thursday, so I don't know if I'm going to be able to get that intercooler off you. Thanks alot for being cool and offering it bud, I wish I could have made it up there sometime. Everytime I went up toward big bear I had some PITA riding with me who wouldn't stand for a detour. Maybe once I get settled in up there I can send you some money if you might be able to ship it? Let me know bud, and thanks again

set it for 16 or what ever you can pull in stock setting.. that woudl limit the boost to the map an you will still be able to make more boost an power. an again.. i have read several times on different forums that obs dont defule.. but who knows..

http://www.powerstrokenation.com/for...p?t-11390.html

Confirmed with live tuning by Jody..

Bingo! matty, you are the man. Commin through for me again, thanks alot bud. so 22 psi is overboost, so i'll set the reg around 20 or 21 psi to get the best fuel info to the PCM. You're the man Matty