93 fd power loss w/normal boost
 

PFC, Pettit intake, PF sidemount hks bov and downpipe. I run pre-mix and occational octane booster from local solvent plant. I recently steam cleaned both rotors.42k original miles.

I have noticed in the last couple of runs that I have made in my the fd that my car has suddenly been making less power under boost. This is troubling to me because i had just fixed the first boost leak i have experienced with the car about a month ago (coupler from y-pipe to IC pipe). The car seems to boost fine (9-10lbs.) but im not getting the peppy surge from the stockers. The transition to the secondary is felt and seems theres no problem there. My knock levels run from 35-55, under vacuum it has gone higher. I guess my next step would be to check for more vacuum leaks, compression test change plugs and wires. Is there anything else i should be checking? Voltage readouts? Please tell me someone else has the same problem?? Any help or guesses is appreciated.

Thank you,

Elliot

Thanks. This weekend im going to be checking to see if the hose connected to the air bypass valve may have come loose when i installed my downpipe. I remember being able to slide it side to side even with the spring clamp on. Car ran great right after the steamclean and downpipe install. Maybe i just worked its way loose.

Again any ideas would be appreciated.

I'd skip the octane booster and stick with good gas personally.

How did you fix that coupler at the Y pipe? Did you replace it? What kind of clamps did you use?

My experience has been that you need to replace that coupler with a good silicone coupler and good "T Bolt" clamps. Like these:
http://www.atpturbo.com/mm5/merchant...egory_Code=CLA


Definitely re-check the vacuum lines as those are known issues - especially if they are the original hoses which are probably brittle by now.

I did use a nice silicone coupler but re-used the original worm clamps. I re-check them again and get some t-bolts. It seems like I fix one thing it runs great untill the boost causes the next weakest link to break. I have been a little timid to tackle the other vacuum lines because they look "ok" when given a visual but im sure they be toast here pretty soon. I sure hope i can figure this out. yeah octane booster didnt really reduce any knock. I was a little bummed because the stuff seemed legit and it wasnt cheap. Thanks for the advice.

Where is your boost gauge getting it's reading? I hesitate to disagree with gracer7, but I don't think it's a boost leak. If your gauge is getting it's reading at the manifold (as it should be) then you turbos are apparently working as advertised and the boost is making it that far. I've never heard or dealt with it, but a sticking double throttle maybe? Other than that, I guess I'd be looking at your tune and ignition settings on the PFC. Have you done a sensor check?

Off-topic, but advertisements for octane booster that will raise your level 2 or 3 "points" is really referring to tenths. So they raise it from 91 to 91.3. Usually nothing significant. If knock levels concern you, consider a simple boost activated Auxillary (water) injection system. You'll control knock AND carbon and get cooling as well.

i have been getting my readings from my boost gauge plummbed into the UIM nipple and also the pfc. both read outs look good as far as boost delivery and stability. It seems that there is lag in the actually power delivery and and power throughout the power band. I just installed the downpipe and the first run was amazing. When i installed the dp i had noticed that the rubber pipe from the y pipe to the charge relief valve would twist side to side freely even with the spring clamp applied. I am hoping this is the problem but am not sure because of this is a new problem and the hose has always been somewhat able to twist. The pfc was tuned by SR motorsports for my set up so im confident that lack of tunning is not my hang up.

It feels like the turbos are working in proper fashion and making normal boost it just feels like the engine is slow to respond to the boost its getting. I cant hear any boost leaks and im not really losing any boost pressure... the crispness of the power and top end isnt there. When i had my y-pipe couler tear you could easily diagnose it from the UIM boost data because pressure would drop big time when the secondary turbo would actuate. This feeling is similar in power loss but still shows normal boosting patterns. I'll check my PFC for sensor V and get back here. Thank you for your time. People like you and gracer 7 are why this site is the best.

Sensor check
 

I dont have very much experience with the PFC so i dont know how to trouble shoot when it comes to the voltage readouts. Let me know if there's anything out of place here. Thanks again.

I fixed the problem!!! pressure tank was leaking and thats why I was having secondary boost problems! The car got a complete tune up and my compression is outstanding.