Just curious. I don't want to get into a discussion of midpipe vs cat. Just curious how many people are currently running midpipes with stock or upgraded twins. Ported wg or not.

 

I am. BNR Stage 3 twins, Bonez mid pipe, and HKS Hi-Power. Loud on the track at WOT!

 

I’m running a resonated midpipe, stock twins with ported wg.

 

I have had both unported and ported wastegate.I'm assuming you are wondering about our experience with boost creep? Because otherwise why would we port the WG...

​​​​​I went single turbo ages ago but I used to have a resonated midpipe, DP, Racing Beat catback, unported WG on stock twins and my car would creep to 12 psi.

I will note that the creeping wasn't a detrimental issue for me because my PFC was tuned to a much higher level than 12psi. But it still bugged me so I ended up porting my WG anything. And the creeping issue was solved as I was able to hold my low boost setting of 10psi all the way till redline.

 

Understood and to be expected. Curious, did you ever run it over 12psi? If you did would it still creep or was the 2 psi over 10 about the the creepin it would do?

 

I did when I was trying to tune my boost controller and hadn't zeroed in on a boost level.

Boost creep is a function of the wastegate not being able to vent the exhaust gasses fast enough to maintain a particular boost level. This is a physical limitation of the wastegate and that's why we port them. In my case, my car could not maintain control of boost below 12psi. So any boost level at 12 psi or above was controlled just fine.

​​​​​During a low boost run (10psi setting) my car would initially be at 10psi. But as the RPMs would climb, my boost climbed as well (or creep up) until it reached 12 psi at around 6500RPMs. In which it would hold 12psi all the way to redline. During a high boost run (12psi setting) the car held 12psi all throughout the powerband. No difference at 13psi. Start at 13 and it held it all the way till redline.

 

I broke my motor in with the midpipe. I have a magnaflo resonated. I have the 3KAI twins with a wg that is a tad bigger than the 93-95s and 99s. I ran it off the wg which would pull around 9psi max. It may have tried and hit 10 at redline. It's been so long and it was only a short time I had it on there.
I am just curious how many people are running them these days. I may put mine back on and obviously just make a whole separate map for it.
I am running an RX7 Bonez "custom" cat set up right now. It flows a bit better than my pettit HF Cat did.
I am still trying to decide what I want my high boost to be... I may do 15-16. I know the manifold is the limit on these twins. 15-16 for the strip or oval track and 13 for everything else. Not sure if I would want to hold my foot down on the oval with 16psi though.... the reason I bring all this up is that extra 15-20HP may be worth it vs adding that extra 1psi lol.... I believe last time I had it at Deals Gap I was running 12 and wanted no more.

 

Every car is a little different when it comes to boost creep. There's SO many little things - intercooler setup, cracking on the turbo manifold, exact restriction of the exhaust, etc. What holds true on one car will not on another.

My rule of thumb is the more open an exhaust is the more prone to boost creep the setup will be. Also a setup that doesn't creep at spring pressure may do so with a boost controller or at higher loads (like a 4th gear pull).

Also I'm just too old for the HORRIBLE stink of a mid pipe. A good high flow cat will get rid of most of the stink and flow 95% as good as a mid pipe.

I think a lot of people are running mid pipes, they are easy and cheap and do the job.

Dale

 

I am think about it for the track as I am running a decent amount of zddp in the oil I have and other reasons. Pick up a few ponies at less psi and save the cat if I am out pushing it a bit on the track. I love my exhaust set up now which is the Bonez DP a custom HF cat from Ari and RB dual.

 

Yeah I can see doing that, makes sense. Doesn't take much time at all to swap out a mid pipe either.

Hope to see you at DGRR! I'm doing my last bits of getting the FD ready today

Dale

 

Any recommendations on a good quality, catted mid pipe? I’m currently running an open one and the smell is getting pretty old!!!

 

The Bonez high-flow cat is always a good go-to. Solid and reliable.

I have an SMB high flow cat from Australia, I don't know if they are made any more, it's been awesome.

Some people have bought aftermarket high flow cats and had them welded into a mid pipe. You do have to look for a high quality metal cat that can handle rotary turbo exhaust heat and flow. I've known of a few that have gone that route to have the cat material ejected out of the tailpipe.

BTW you do NOT need an air pump with a cat. I've run my SMB cat with no air pump for about 15 years of abuse, zero problems.

Dale

 

I had the Racing beat Mid pipe and twin tip cat back with the BNR Stage2 twins. It would hold a stock boost pattern without creeping.

 

I think all the BNR had/have a ported wg no?

My 3kai have a mm or so bigger than the "stock"

 

When I tracked my car frequently ages ago, I had a 300 cell metal core cat welded into my midpipe to help control boost creep and eliminate some of the stink. Was difficult to control boost w/o an unported wastegate and midpipe. Worked great. Ran that for a few years until I moved onto racing Spec Miata and un-modded my car into more of a street car and installed the Bonez cat from rx7.com - much less stink and noise.

 

Yes ported wastegate.

 

Mine would not hold stock boost with a midpipe and Ganador Ti, non-port wg. With the wg ported it will hold 12psi or 14psi without issue.

 

Couple of questions…did you plug the pipe that connects to the air pump? Also, would you install a wide band/O2 sensor before or after the cat?

 

before

 

Wide band always before the cat for the best reading.

On my SMB cat I made a block off to seal up the port for air pump air. Banzai Racing has a great block off kit for the ports on the UIM that need to be blocked when you remove the air pump.

Dale