What is overboost? In regards to removing cat from DP.

[Marauder.45]

Saw a comment regarding overboost when running a test pipe. What is this? Does it always happen when you take the cat out? Is it something you can tune out safely?

 

[Super Shredder]

boosting past the pressure capacity of the turbo or super charger. caused by an inadequate wastegate. manifold/wastegate and tuning will solve. are you thinking of boost spike? or creep? which in an untuned bolt on vehicle is very likely during certain situations.

 

[Marauder.45]

Not thinking anything specific yet. I saw the phrase in a thread and wanted to know what the deal was. I just ordered a whole mess of s*** for my car, which I'm the second owner, and I decided to go with a test pipe ($95, thank you Boostdspeed6) until I can come up with the loot for a cat'd DP. I have the Cobb AP on order in that mess of s*** for the car.

A quick explanation of creep and spike wouldn't hurt. I'm pretty sure I've figured it out, but no reason not to get a real definition.


OT: I think I saw you the other day. I'm in Jersey too, and I saw a car that looks just like your avatar on Cross Keys Rd, stopped on the overpass over 42/xpressway.

 

[jracer]

i have a testpipe and magana flow cat back exhaust.. cobb tip/sri.. with the ap.. i am getting overboost with the stage 1+sf93v101u map...
but stage 2 doesnt run as good.....i am getting aloittle pissed with this thing...

 

[Blendercloud]

i have a testpipe and magana flow cat back exhaust.. cobb tip/sri.. with the ap.. i am getting overboost with the stage 1+sf93v101u map...
but stage 2 doesnt run as good.....i am getting aloittle pissed with this thing...

With nearly identical mods to you I had to jump up to Stage2+SF 93 because my LTFT's were 14 and it was really sluggish with the Stage1 map.

To the OP: Boost spikes are exactly what the phrase describes. When you engage the accelerator at WOT and the turbo begins making full boost if you are experiencing a high boost spike you will see your boost level jump way above your target and then drop down to your target. From what I've gathered you will probably always see at least a very small degree of boosting over your target before it levels out. For the sake of this example think about this: Your target boost level is 15.5psi. Upon full acceleration you make 17.5psi and a second later you're down to 15.5psi. You just experienced a boost spike.

Boost creep is where you are at a target level of boost at WOT but over the period of your pull the car begins to make more boost than your initial target. As an explanation it sounds like the boost is 'growing'. For example: Your target boost level is 15.5psi still. Upon full acceleration you make 15.3psi. In .5 seconds you're making 15.7psi. Another .5 seconds later you're making 16.3psi. And another .5 seconds after that you're making 17psi.

Boost spikes and boost creep is not mutually exclusive. You can have both simultaneously.

 

[Marauder.45]

How dangerous are all of the issues discussed?

My set up will be as follows. All of these parts have been purchased, except the Forge.

CP-E Xcel CAI (from previous owner)
PG TIP (new one they are selling here)Ordered
Forge BPV- not ordered but I think it's going to be needed
SU Test Pipe- Ordered (until I can scrounge some loot for a full DP with cat)
Magnaflow catback (from previous owner)
AWR motor mount- Ordered
Cobb AP.


Anything I'm missing? Pretty good set up? Yes/No

 

[Blendercloud]

That test pipe and TIP are really going to open your car up. Couple those with the AP and a Stage2 map and you're going to love this car at least 3 times more than you already do!

As for the danger of those issues... I wouldn't say either of them are 100% dangerous 100% of the time. It seems like overall they are efficiency concerns more than anything else. Granted, if your target is 15psi and you're spiking at 21psi... that's dangerous and it's a big problem. Also, if your target is 15psi and you're creeping to 19-21psi that's a pretty big problem, too. I wouldn't be overly concerned with it until you get your AP and are able to datalog to find out the actual numbers.

I did see one thing missing from your list that you should look into with the rest of those mods. Denso ITV22's (one step colder than stock). It's essentially going to be the best $45 you can spend on your car. My car went from falling on its face with a 3.5-4.2 KR (spark-knock timing retard) to a "holy s*** my nipples just flew off" with only a .35 KR at 2300 revs. It makes an enormous difference.

 

[kylefire5]

So if I have a similar setup but without the cobb ap. How could I tell if this was happening?

Should it be somthing to worry about?

 

[Blendercloud]

How do you tell if which is happening? Knock retard of the timing or boost creep and/or spike?

 

[gimpo2]

Get a boost gauge and watch it.

 

[Super Shredder]

all of these things will lessen the longevity of your turbo and engine. if you are overboosting, you need to get a tune, or do some sort of modding to your turbo. the wastegate cannot release enoguh pressure at the right rpms. the cobb ap should really help this over stock, but since your mods do not fit the exact maps that cobb offers, an e-tune or protune will help prevent it. a turbo manifold with a tial wastegate will not only help your low and mid end, but will prepare you nicely for a turbo upgrade. you should have full gauges and/or an MSD dashhawk to be monitoring.

 

[tunersteve]

Cobb has came out and said that overboosting can occur if you remove both cats from the exhaust. By not allowing the wastegate to effectively expel gases, you can get boost spikes and potentially dangerous effects as a result. The AP can help it somewhat, but there's no guarantee with that. Your best bet is to leave the downpipe with some sort of cat in it at the very least.

 

[Marauder.45]

I forgot the plugs, I did decide to go Denso over NGKs.


I know the recommended is to have a cat in the DP, but so many people seem to not be running one that it doesn't seem like a huge risk. I have a factory warranty to 5yr/75k and I keep all my factory parts. Should I have a problem, I can always put back on the OE parts and go to the dealer with a quizzical look and say "what's wrong?" I paid extra for the insurance, so I feel okay with feeling protected by it. I would rather just get the cp-e DP with hi-flow, but I can't drop another $950 just this minute. I need a little recovery from getting all this s***.

Thanks for the input.

 

[tunersteve]

I forgot the plugs, I did decide to go Denso over NGKs.


I know the recommended is to have a cat in the DP, but so many people seem to not be running one that it doesn't seem like a huge risk. I have a factory warranty to 5yr/75k and I keep all my factory parts. Should I have a problem, I can always put back on the OE parts and go to the dealer with a quizzical look and say "what's wrong?" I paid extra for the insurance, so I feel okay with feeling protected by it. I would rather just get the cp-e DP with hi-flow, but I can't drop another $950 just this minute. I need a little recovery from getting all this s***.

Thanks for the input.

There's not much difference between a catted and no cat DP in terms of performance, but they do make an impact on how the car runs. You want the cat in there. Cobb's maps are designed with some restriction of a cat in mind. Keep in mind too, a DP is no easy install, plan on spending some time getting that put in.

 

[Marauder.45]

Is TP only an easier install than full DP? Or is it the same either way?

 

[tunersteve]

Is TP only an easier install than full DP? Or is it the same either way?

TP is a breeze compared to the DP. 4 bolts and 15 minutes and you're done. DP is a lot more complicated, removing O2 sensors and bolts on the turbo, then manipulating it out from under the car.

 

[Blendercloud]

I would keep a day fully open to swap out downpipes. Things are hard to get to and even harder to get out once you get to them.

 

[Marauder.45]

Good info.


Thanks.

 

[Super Shredder]

id rather have a dp with a cat tho, it sounds 1000 times sicker.

 

[Marauder.45]

I would too, and I will down the road. Just need a quick fix until I can come up with the next round.