I'm new to the turbo world and trying to figure everything out so bear with me. I just put a 3" 5zigen cat back exhaust system on my 04 WRX. Everything is stock except for that.(unless you count removing the muffler before the air filter) Right after I put it on I noticed that my car dropped the boost from 13-14 psi to about half that as I get into higher RPMs I've noticed it drops sooner in RPMs and faster the lower gear that I'm in. I have an extended warranty so I dont want to put customize anything to the point that I cant switch it back for warranty work in the future. The only thing that I can think of is put the stock mid section on with the 5 zigen axle back bolted to it. If you have anything for me let me know!!!
If I understand correctly you only have a catback and you removed the Intake Silencer? Neither mod you described should mess with boost. BTW- how are you measuring your boost? Sound like you have a leak somwhere. Easiest and most common culprits are the IC hoses. Check all your clamps/connections and make sure they are tight. you mentioned an aftermarket warranty. Did you buy the car used recently?
get some carb cleaner and spray around your hoses listen for your idle to jump... do you have an aftermarket bov/bpv?
So wait a minute here....you are seeing 13-14psi at lower revs and then it drops down to 7-8psi at high revs? If so, that's totally normal. Also, it's normal for the car to run less boost in 1st and 2nd gears.
I'm measuring with the stock boost guage. I didn't even think of checking for intake leaks. It's just ironic that it started directly after I put the cat back exhaust on. I did just buy the car used. Stock BPV. I'll double check all the intake connections because right before the exhaust it got a new short block under the warranty when i bought the car. I'll double check all that then I'll post what happened.
just FYI, the stock turbo can't push enough air into the engine when you're at 5k+ rpms....the engine just sucks in more air than the turbo can push...so....boost tapers off. unless this isn't it...
I checked for any kind of intake leak and checked all the connections to make sure they were tight and everything checked out good. I'm gonna try putting my stock midsection back on with the 5zigen axle back and see if it goes away.
No leaks is good. And I have to agree with Wall of TVs and Fuji K. If your running a stock set-up besides the catback you will see a drop in boost in the high rpm range. What gears and RPM are you noticing the drop? I wouldn't take the exhaust off. If your concerned have someone check it out before you do anything.
if you think about it, you are loosing boost because you are moving the exhaust out faster, which isnt a bad thing! when i had my thunderbird s/c (supercharged) i upgraded to a full exhaust, and lost 3 psi of boost, then added a pulley and got it back, along with an assload of power
Thats how a super charger would work, but on a turbo you will not loose boost. As for loosing boost, 14-16 in the mid and tappering off to 8-10 up top is about right for a 2.0l wrx. Then since you are running a 4eat, your boost curve will look alot different than the 5-speed cars. Russ
even if this were the problem how would I get more boost out of it without reflashing the ecu or putting a manual boost controller in?? One of the parts guys at Morries BP subaru mentioned something about changing the size of what i would call a restricter in the vacuum line between the charge pipe and the wastegate, but before the boost controller vacuum line. Does anyone know anything about that or what that parts purpose is??
Don't go swapping any more parts or changing the restrictor pill. Whatever you paid for your exhaust, spend an extra $100 and get somebody to log and tune your car. That will tell you what is going on with your car. Guessing without logging is FTL.
Again, by changing the exhaust you will not loose boost. If you are running the stock map, you will only have 14-16psi in the mid and 8-10 up top. If you want more than that you need to get it tuned. Russ
Well, either way you will only be in the 14-16 mid and 8-10 up top. What are you running for boost?? How are you measuring boost?? If you are running a aftermarket gauge, what line are you tapped into?? Russ
Im using the stock boost guage. im running about 14 then when I get to about 5500 rpms it drops like a rock sometimes as low as 5-6 psi by the time i get to 6500 rpms. I understand that its supposed to drop but it seems a little excessive.
I would woatch it. Wastegate pressure is 8psi, so it shouldn't drop below that, but that does sound about right. Once they get into the upper rpm, the boost drops down to wastegate pressure. Russ
Keep in mind, the stock boost gauge is mechanical I believe. And the vaccum line used to get readings runs from the engine bay to the inside of the car. This can cause lower than normal readings due to the pressure drop across the hose. 5-6psi would be in the region of 6-8 psi possibly. And Fuji nailed it on the head earlier...I don't think the TD04 can feed enough air to keep pressures up at the top of the RPM range because the engine draws in more air than the TD04 can deliver. Have someone ride in your car, or if you are trusting, have someone drive it. There are a few people that regularly visit Firestone that might be able to rule out boost leak by simply taking it for a quick hop on the freeway.
The stock line running in to the car has massive sidewalls. There may be a little pressure drop but it wouldn't be huge. My stock gauge differs from what Enginuity says I'm running for boost by about 1 PSI. Is the boost gauge inaccurate or is it a pressure drop? I always figured it was the gauge but maybe it's a bit of both.
^^ it's probably your gauge. And the boost drop is due to a few things. 1. the stock ecu calibration targets 13.6psi up through 4800rpms and then tapers it off to 11.9 by 5600rpm and then down to wastegate boost (~7psi, but it shows 6.65psi in the ROM) by redline. 2. the turbo can easily flow more than this at any of those engine speeds, however the stock BCS can have a hard time "keeping up" with bleeding off the pressure from the wg actuator when you jack up the boost targets.
What people are you talking about?? And what does it have to do with Firestone? Either way I would like someone that knows these cars inside and out to go for a ride just to be sure.
Me or wall of tvs or a number of other people can log/tune your car pretty quickly if that cat-back is the only modification you have. I live on the east side of town, wotv's lives on the west side. PM one of us. There's probably nothing wrong with your car, you just need a tune.
I have a cable and laptop as well, and live close to firestone. Let me know if you're going to be down there on a Friday or Sat, and I'd be happy to help you grab some logs.
