RB20 boost problems don't know..

[lyon23]

I don't know what more to do.. my rb started runing good at 10psi and holding now after adding different piping (and I checked no leaks, I've done this too many time to count) after changing many vacuum hoses to new ones(still runs the same).. the car just doesnt want to hold boost.. it starts out at 12.5 (I know this is not stock, I bent the wastegate rod to get more boost) then it drops to 7 or so and by looking at my A/F gauge(which is not something to really go by) it reads lean. I tried activating one of my additional injectors on my intake and it still runs lean.. I changed the line goin to the wastegate actuator from the turbo and move the rod back to get stock boost and now it feels a lot stronger at 7 psi on first gear than the 12 I was runing before. But it still reads lean and boost drops from 7 to about 5 on first then if I shift to 2nd it starts at 9 and drops to 6 and it does this while reading lean and it starts at about 4500 rpm and stepping on it from the beginingof first. Now if I start at about 3 gran from a roll start on second it starts and goes to 10 and stays there until I get to 5500rpm and then it starts to fall then I shift to 3rd and it holds 10 with no problem and reading rich like before. I also changed the stock blow off cuz it was leaking and now I got a new blow off that sounded like leaking but the adjustment was so tight that it didn't realease the air I actually heard the turbo spooling so it was not leaking. I'm runing out of things to do can some1 give me anything they think might be wrong if I have to check things again let me know you will not get an I tried that from me...I just want to get my car runing right. I have an apex safc2 on it but its really doing nothing since I'm not making the inkectors work I have it on a normal setting. I have 450cc injectors I don't want to put on till i figure out what this might be. my stock turbo has some shaft play in and out about 1/8 of and inch. I was thinking of a bigger turbo but is not goin to help me if the same thing is goin to happen. If all else fails I might have to take it to a shop and have it dyno tuned and put a wideband on it and try to determine weather it is getting gas or not enough. Just needed to vent this is driving me crazy..

[IvoryJ30t]

if the crappy af gauge is reading lean while your on boost, just be thankfull that your motor is still in one piece.

[JonPowell]

Ok, you changed your piping, did you go much larger?

Understand that boost is not a measure of airflow, but rather a measure of back pressure in the intake system...I dont know EXACT numbers and each situation is going to be different so understand this is just for explanation....

A vehicle with 1.5 inch intake pipes running at 12.5PSI will flow say 100CFM.A vehicle with 3 inch intake pipes running 5 PSI might flow 150CFM

Boost is not what you should ultimately care about, but rather what your actual, not disco light gauge, air/fuel ratio is.

If you were losing boost, you would have lots of problems with the engine running right.

As RPM goes up the need for air goes up so your boost pressure will go down.....air flow will not but restrictions in the intake tract will as the engine tries to consume more air in the same amount of time.

[Joe]

jon is correct, the rb20 turbo isnt the greatest high flowing turbo to begin with so if you are running a large pipe setup you could easily be going over the turbo's efficency range.

but why are you running lean? it shouldnt run lean espically if you are underboositng.

[JonPowell]

Less pressure with more air flow could DEFINATELY lean it out.

Boost is a measure of the back pressure, not air flow...so underboosting could also mean the new junk is less restrictive.

Maybe the new piping allows the turbo to work more at flowing air instead of pressurizing pipes. at first there is pressure because the engine is at lower revs....as the revs come up the engines demand for air increases so the pressure will drop but the airflow will be the same.

[Joe]

Less pressure with more air flow could DEFINATELY lean it out.

Boost is a measure of the back pressure, not air flow...so underboosting could also mean the new junk is less restrictive.

Maybe the new piping allows the turbo to work more at flowing air instead of pressurizing pipes. at first there is pressure because the engine is at lower revs....as the revs come up the engines demand for air increases so the pressure will drop but the airflow will be the same.

but if the MAF is flowing X amount of air, wouldnt it subsiquently add the fuel? the air that the turbo is moving obviously isnt making it completley to the engine to pressureize it, so it should run rich because the ECU thinks it has stock piping, and X airflow will mean X fuel is needed, no?

[JonPowell]

As long as the flow is not maxing out the airflow meter, it should be fine.

Maybe this new turbo IS maxing out what the MAF can read and that is why its going lean...maybe airflow is over what the MAF can accurately measure while boost pressure is low because of less restrictions???

I knowthat hte stock sidemount intercooler is WAY restrictive and the FMIC/Piping upgrade may allow SO MUCH more air.

I say wideband and take it to the dyno with your NEW injectors and turbo installed and have them tune the SAFC.

Try resetting the SAFC also. Maybe you changed something on accident.

Which knock sensor signal did you attach the SAFC to? Maybe trying the other wouldnt hurt....did yous et up the knock correction right?

[lyon23]

I attached the knock to signal one like the afc wiring said it was te one giving me the higher reading. I did the holding at certain rpm and record the signal and again at a higher rpm. I think you might be right on the rb20 turbo not providing great amount of air... I got 2.25" piping and it's set up like the skyline kit they sell on ebay. after I changed the wastegate actuator line from the turbo the cars runs like before and it feels a lot better. After I purchase the turbo I will take it to a shop and have dynoed and tune... I'm still undecided about the turbo wether I should go with a .63 or .48 exhaust...my friend just put a .63 exhaust with a 57 trim compresor on his integra 1.8 and he doesnt' get full boost untill 5500.. I'm thinking the rb20 will be a little better but not that much...I believe it was nick who said his get 10psi at 4800..So i was thinking a .48 wil get me boost a lot faster ...untill that time i'm treating my rb20 with a lot of care until i can get it tuned and upgraded... kind of hard to hold back on not racing..but thanks for your info

[goofynick6]

I'd go with the .48 housing, unless you are going for like 400whp or huge top-end, then I'd go .48..I almost thought about switching lately so I'd have more down low grunt.

NIck

[lyon23]

Thanks for the info Nick