Downpipe/J-pipe Options

I'm looking for a high flow catted downpipe to put on my LGT. Anyone have any advice on which brand to go with? I've been looking around for a while, but as you all know, aftermarket parts are a headache to find for these cars..

2010 2.5GT

Borla cat-back exhaust

COBB AP V3 Stage 1 - (91 OCT ACN map)

I'm looking for a high flow catted downpipe to put on my LGT. Anyone have any advice on which brand to go with? I've been looking around for a while, but as you all know, aftermarket parts are a headache to find for these cars..

Been looking into this too. If you were going catless my understanding is the IQ J-pipe is one of the best. For catted I think you are looking at Invidia Catted as not sure if others are still making a catted downpipe for our the fifth gen LGT. Maybe some other members will chime in.

If you read up on it you'll find that boost creep can be an issue with many catless downpipes so going catted apparently helps with this issue. The IQ catless design as I understand it doesn't seem to have the boost creep issues so prevalent with other catless designs. In general the recommendation seems to be if putting in an aftermarket j-pipe to consider an aftermarket BPV as well as consider installing an ECBS too.

I've had an Invidia catted downpipe for a couple years now and it works well. I got it from Rallysport direct. Looks like they're out of stock at the moment but might be worth a call to see if they expect to get more.

The aftermarket BPV is a must if you want to take full advantage of your turbo. Most people just tend to do it at the same time as a downpipe because the stock one leaks so much that your tune may need some fine adjustments to account for the extra air.

I've had an Invidia catted downpipe for a couple years now and it works well. I got it from Rallysport direct. Looks like they're out of stock at the moment but might be worth a call to see if they expect to get more.

 

The aftermarket BPV is a must if you want to take full advantage of your turbo. Most people just tend to do it at the same time as a downpipe because the stock one leaks so much that your tune may need some fine adjustments to account for the extra air.

The bpv leaking doesn't affect the air since both ports are post MAF, the leak does affect the amount of work the turbo has to do to keep boost pressure on target.

Also, I don't believe the invidia jpipe will be coming back in production especially as demand for them has already peaked from a very small portion of the LGT owners in this gen. I would highly recommend the IQ jpipe. Also you may want to join the facebook 5th gen group quite a few members from this forum are on there as well, so there is a lot of good information there as well.

Check Mach V - they show the catted J pipe on their site. might be out of stock if you add it to a cart, but who knows.

https://www.fastwrx.com/collections/downpipes/products/invidia-j-pipe-downpipe-2010-2012-legacy-gt

The bpv leaking doesn't affect the air since both ports are post MAF, the leak does affect the amount of work the turbo has to do to keep boost pressure on target.

I’m not sure I’m understanding your logic on this. The maf is the only component monitoring the total air coming into the engine. If you lose air that the maf already accounted for, the engines going to expect that air to get to cylinder. You want everything sealed after the maf to ensure the computer doesn’t get confused.

The bpv is also after the turbo, meaning compressed air is escaping and the turbo has to work harder to hit peak boost.

FLlegacy is right - our BPV is a bypass or "recirculating" valve, meaning any air that is "released" is just sent back to the inlet of the turbo (post-maf). A "leaky" BPV just makes the turbo work a little harder on our cars.

A stereotypical blow-off valve does release the air back to the environment and you would be right, but ours recirculates 100% of the air.

 

I’m not sure I’m understanding your logic on this. The maf is the only component monitoring the total air coming into the engine. If you lose air that the maf already accounted for, the engines going to expect that air to get to cylinder. You want everything sealed after the maf to ensure the computer doesn’t get confused.

 

The bpv is also after the turbo, meaning compressed air is escaping and the turbo has to work harder to hit peak boost.

Ok, so it’s an internal leak passed the diaphragm and not a leak to atmosphere.

The BPV would only leak to atmosphere if it was physically damaged, in which case the car would probably not run or run very poorly. And yes exactly as I stated in my post the turbo does work harder to compensate for a leak in the bpv.

It is honestly best to replace the oem bpv with an aftermarket like the turbosmart or gfb just to make sure leaking doesn't become an issue.