Second cat enough to prevent creep?

[AutoEuphoria]

I have a catless DP and MP right now. I have been trying a lot of different ways of trying to control a boost creep problem, with very little success. Everything I've read points to the fact that the exhaust is too free-flowing and the wastegate on the turbo is being overwhelmed. Logs also show this to be the case.

I am wondering if the second cat would provide enough restriction to take care of this boost creep issue? I would think it might, considering most people with the high-flow cats don't seem to have this issue. I just don't want to go through the trouble of making the switch if it's not going to do any good.

Thanks! This is my last resort before trying something more drastic.

 

[SallySpeed3]

I would think so. Not that I have any data to prove this. But Cobb advises the use of a DP with a free-flowing cat for all their tunes, and you're right, I've never heard of any complaints from people who run at least a 1 cat set-up.

 

[MSMS3]

OP: Could you please again refresh my memory regarding your other mods? Mine are in sig below and I do not get boost creep, so it must be something in addition to the catless dp/rp that is producing the exhaust overload of your wastegate.

I do have a 3 inch straight through reso in the middle of my race pipe to control drone. Maybe that was just enough to keep me from creeping? If our mods are otherwise similar, then maybe a high flow cat would get you where you can hold boost steady at target.

Mods list please?

 

[AutoEuphoria]

It's close to your mods, except I have a turbo inlet, upgraded BPV, and FMIC. I'm not getting boost creep all the time, but I do still see it...mostly in third and fourth (which isn't good if I'm at the drag strip)

 

[Darth Vader]

No question the stock second cat will control it, I ran that way for a while. A Turbosmart Boost T plumbed to manifold finally calmed the Test Pipe spike 'n Creep for me. The stock BCS is incapable of handling this.

 

[Mybeauner]

Would the cobb ap and a tune also help prevent creep?

 

[AutoEuphoria]

Not really, no. Nothing the AP can do about a small wastegate. I'll most likely be doing the switch this weekend, so if I see any results either way I'll be sure to post up.

 

[Darth Vader]

Well...that's the textbook correct answer, as boost creep is a mechanical flow issue. However, as usual on this car, it doesn't totally work according to the plan and assumptions that have served the turbo using community for decades don't work as expected on this car.

I think what most call "boost creep" here, even me, is a variation of pressure spiking moving slowly enough to imitate creep. Datalogging WGA % will tell you if it's creep or something else.

To a point you might be able to tone down this kind of creep with the AP but, the problem remains the stock EBCS isn't really up for this. What finally worked for me was what I posted earlier though, admittedly, I don't have an AP to try a solution there.

 

[anm6]

I have no creep at all with a catless DP and stock second cat.. See other mods in SIG.

 

[AutoEuphoria]

Yeah, second cat is going back on today. Boost target set for 17...saw a creep up to 21 today (not just a spike...a steady creep). I have done logs in the past as well that show WGDC was 100% (or 0%...whatever means full open) while boost was creeping up.

 

[destrux]

Anyone tried porting the internal wastegate? This has worked for me to eliminate boost creep on several other cars. You basically just open up the wastegate hole in the turbine housing so that hole is bigger, but not so big that the flap door can't cover it (with some overlap). Sometimes there's also some improvement to be made by removing material from the wall in the turbine housing that the WG gasses hit after they pass through the WG hole, and smoothing the transition area where the WG gasses separate from the turbine gasses in the turbine inlet area.

Of course, this does require turbo removal and porting tools.... but it's a better solution than restricting the exhaust and losing power.

 

[Saskatchewan17]

Having one cat in the system should be enough to prevent any major, threatening creep with the K04. Yes, destrux, porting the wg would solve the problem completely. Also, running a proper MBC set up helps limit the spiking. Best solution though is porting the wg, or just splurging for a reworked K04 or SST.

 

[coyfish]

Bump for this thread. Im also getting creep. Had the problem before I was tuned and now its more under control but still evident. At about 5200rpm (power sweet spot) my boost goes up. Before my tune I was also having knock / lean conditions. 1st-3rd gear usually are fine and don't go over 18-19psi. But 4rth+ I see 20-21psi all the time. Not spiking either . . . holding. I can hear that poor little k04 screaming.

I don't know what could be causing the problem. I am on the stock DP so I don't get it. The only thing that could be the problem is the Intake I have. But when I had just a CAI,test pipe, bpv . . . the car ran fine.

To me creep means im being TOO efficient. But im not even fully bolted so wtf !

 

[Darth Vader]

Maybe it's the awesome Scott RR tune.....

This issue ain't good, you're gonna break something doing that.

An MBC (Turbosmart), ungated, finally reigned in all this crap for me, oddly enough. I still get load cut in cooler temps. I'm on the stock tune, but I have all the in and out mods bar an FMIC.

 

[coyfish]

Maybe it's the awesome Scott RR tune.....

This issue ain't good, you're gonna break something doing that.

An MBC (Turbosmart), ungated, finally reigned in all this crap for me, oddly enough. I still get load cut in cooler temps. I'm on the stock tune, but I have all the in and out mods bar an FMIC.

The RR bashing was uncalled for. And I know the issue isn't good which is why im trying to resolve it. The problem isn't the tune so I was looking for other causes of creep. Don't mean to be an ass but I found those remarks kind of offensive.

But im glad your MBC is working out for you. Im already tuned so thats not an option for me.

 

[meicalnissyen]

Anyone tried porting the internal wastegate? This has worked for me to eliminate boost creep on several other cars. You basically just open up the wastegate hole in the turbine housing so that hole is bigger, but not so big that the flap door can't cover it (with some overlap). Sometimes there's also some improvement to be made by removing material from the wall in the turbine housing that the WG gasses hit after they pass through the WG hole, and smoothing the transition area where the WG gasses separate from the turbine gasses in the turbine inlet area.

Of course, this does require turbo removal and porting tools.... but it's a better solution than restricting the exhaust and losing power.

That would seem to address the source of trouble, guess it would depend on how bad the shape is in there.

haha, we used to Port cylinder heads, now its wastegates

 

[AutoEuphoria]

Just as an update...installed the second cat and it seems to have really helped the boost creep problem. I can hit and maintain my target psi now with little problem

 

[Mybeauner]

Has anyone experienced more creep in colder conditions? just wondering.

 

[FrequentFlyer]

Just as an update...installed the second cat and it seems to have really helped the boost creep problem. I can hit and maintain my target psi now with little problem

Have you noticed any reduction of power with the "butt dyno"?

 

[AutoEuphoria]

Not really...and I've taken it off and put it back on again since then. Very little change in power...maybe a little extra spool time...and less noise.