Does anyone run these products and what exhaust do they pair them with? They’re both 3.5” and was thinking of using them with my racing beat dual tip 3” exhaust. Would that limit the flow much? or do I definitely need to buy a different exhaust.

Going from stock to smic, autoexe intake, pfc, downpipe, hfc/midpipe.

 

A 3" exhaust flows enough for the vast majority of users.

You won't "need" a larger catback, especially not with your other mods.

Does the SMB midpipe/cat section terminate as 3.5" or does it step down to 3" before the rear flange? If it's got a 3.5" flange then you'll run into trouble trying to mate it up with anything other than a 3.5" rear exhaust section.

 

Just so I’m sure I’m following you here....the “stock” intercooler IS a SMIC configuration. And is it a hi-flow cat (hfc) OR a midpipe? It’s kinda hard to have both.


And if you’re contemplating a downpipe/midpipe on the stock twins you might want to read up on boost creep. The stock twin’s wastegate is on the smallish side and often can’t handle unrestricted exhaust flow. That can cost you an engine AND turbos.

 

overkill for the stock twins IMO. if you plan on upgrading them at the same time then go for it. for reference, with the STOCK intercooler, aftermarket intake, 85mm turbos back exhaust, and a restrictor after the downpipe, I was still seeing 14+psi. if you go this route you will want to upgrade your fuel pump and secondaries as well.

 

I've had an SMB high flow cat for ages, super well made and top quality all around.

I agree, 3" is plenty for what you are looking for. My high flow cat is 3" and bolts up to any cat-back out there with zero problems.

If you do want to go 3.5" I would email SMB and ask about compatibility with a standard cat-back. I know they will also custom-make parts, in theory they could make a mid pipe that has a regular flange on the back but you'd be choking the exhaust down at that point.

Dale

 

Appreciate all the good info. Okay then I’ll start looking into 3” downpipe or reach out to them to see if they can make it custom so I don’t have any issues with the catback.

Yeah, the plan is to get an upgraded smic, autoexe intake, hfc and tune of course. With that setup, would I still need to worry too much about boost creep? And porting the wastegate?

I’m trying to keep things simple and close to stock as possible, and im motivated to go this route cause my stock cat is hollowed out so I want to get the car set up “right” before i do any damage on the 60k mile original engine. (Compression shows decent numbers and hoping to last another 20-30k before rebuild if i don’t chase hp)

 

To keep it simple I’d suggest a 3” Bonez or HKS downpipe, a 3” Bonez or SMB hi-flow cat and your R.B. cat-back. All good quality, all will fit and function, sound good with no creep or smell. Boom.

If you feel flush, have the DP heat coated or (cheaper) header wrap it.

 

Appreciate the suggestion. Im a noob and sometimes while digging through the forum im not sure if im selling myself short by taking suggestions from 2004, etc..

 

So in the case of using stock twins your main exhaust flow restriction/chokepoint is going to be in the turbo manifold. Opening up the exhaust itself beyond 3" won't really be beneficial. In fact, going *too* free flowing can hurt twins because it could lead to boost creep when the WG's just get overwhelmed.

If you don't have the 3.5" exhaust already than I'd honestly pass on it for now. A 3" DP with 3" midsection and high-flow cat will help nicely and be a good match for your current setup

 

Got it. You guys saved me a lot of headache and cleared up the questions i had.

 

Mid 2000s was the best time for a stock modded twin-turbo FD RX7, not much has changed.
The best single turbocharger is still a daily debate as turbo tech is rapidly changing.