Monsterbox

iTrader: (6)

I'm going to give the midpipe a try before buying a new cat or high flow....i bought a resonated mp and before it gets here i want to know what size restrictor plates..how many how big what to do where to put it if i do happen to experience insane boost creep that i cannot compensate w/ my ecu

setup:
PFS ECU (set fuel cut at 14lbs)
HKS intakes
Stock catback piping with chambered muffler
M2 DP


so what/where/how do i get restrictor plates? can i make them?

RotaryResurrection

iTrader: (8)

In reality you could probably use a stock metal gasket as the restricter, especially for a short term trial. IF you're not happy doing that, just take a stock gasket and cut a thin piece of metal out in the same inside diameter but a little larger outside diameter (same as the flange on your MP). The bolt holes will be different, I would just cut them as "U" slots at the ends to accomodate the wider bolt pattern.

I'd put this between the DP and MP.

HKStreetRaceRx7

iTrader: (3)

I had a restrictor plate made from stainless steel from a company I found on ebay for $20. I just sent them a design of a stock gasket and told them to make the inner diameter 2.25" instead of 3". With this size I have no boost creep. I think I could probably go with a little bit larger diameter without boost creep, I'm just using it now to be safe until I port the wastegate.



I know the user Jyro used to make restrictor plates and would sell them in a set of 3 in various sizes so you could tune it for your set up. I'm not sure of his design, sizes or cost though.

3GRX7

iTrader: (1)

Did you notice a good amount of performance increase when you added the midpipe? I'm curious if using a restrictor plate & midpipe will show a worthwile performance gain over the stock cat.

Thanks,

Ian

Mahjik

iTrader: (1)

Absolutely it will a benefit. The problem is making sure you can keep the boost under control. The stock piping is 2.5". A midpipe will be 3". Even with a resistror, the restrictor will only be about 1/8" width so you aren't restricting the flow nearly as much as a 3' long 2.5" pipe.

HKStreetRaceRx7

iTrader: (3)

Yea for the little money I spent for the midpipe and the restrictor plate it was definately worth it. I noticed that the turbos spooled up quicker and there was definately a lot more high end power compared to the stock cat. And by replacing the stock cat with a midpipe you'll drop a good bit of weight and not have to worry about it getting clogged. The only downside is that the exhaust is considerably louder though which just depends on your preference. The only time it really bothers me is on the interstate.

DigDug

I've seen a 2.25" restrictor work on a few FDs with varying configurations, all of them switching from cat to midpipe. I thought this "coincidence" was rather surprising, given that they all had different exhaust setups (DP and CB), until someone pointed out that there are 2.25" restrictors welded into the stock cat. Apparently Mazda went with 2.25" as well, presumably in case the catalyst blows out the exhaust.

That said, the catalyst itself is far more restrictive than the 2.25" restrictor. Going to a midpipe with a restrictor does seem counterintuitive (and is certainly less than ideal), but it does flow much better than the stock cat. Not to mention getting that heat out of there.

I tried 2.25", 2-3/8", and 2.5" restrictors myself. The 2.5" didn't do it - still had serious boost creep. Tried the 2.25", and got no creep whatsoever. Decided to try the 2-3/8" just to see what would happen, and that's the one I'm still running today. If it's close to freezing out, I can still get a pound or so of creep at the top end, but the rest of the year it works perfectly.

DigDug

Oh, and we're talking maybe 15-20HP, depending on your setup. That might even be generous. I have a PFC, so of course I went and got it tuned immediately after swapping out the cat. Volume increase wasn't bad at all, but I'm running an RB dual tip cat-back - if you have a canteloupe cannon out back, it will be considerably louder.

twin7r1

iTrader: (1)

the absolute chaepest way to go about this if youdont want to make anything your self is to just go to a muffler shop and pick up a 2.25" exhaust flange and an extra gasket. I picked up mine for $4. Works great!

Monsterbox

iTrader: (6)

thanks guys! im exited...i guess ill try 2 3/8 and 2.25

Monsterbox

iTrader: (6)

o & for kicks my midpipe will have a wideband bung already drilled and capped...thinking bout throwing an extra spark plug in it ...how can i run voltage to this plug?

JyRO

iTrader: (3)

HKS - My restrictor plates are stainless steel also. The reason I don't just blatently send 1 restrictor plate at 2.25" is that power WILL be robbed from an FD with smaller and smaller diameters. The power robbed is on an exponential scale. Dig Dug has a MUCH better situation than you do.

I don't know that he actually has more power than you, but he CERTAINLY has the potential to have more power than you due to his more precisely sized restrictor plates.

BTW, the picture looks a lot like my restrictor plate, except mine look a LOT cleaner than that. Meaning not just how messy that one looks, but my holes are cleaner cut ... and that hole looks entirely too small to me. Also, if the exhaust hole is not cut clean, there could be anywhere from some mild problems to big problems.

RotaryRessurection mentioned where he put his restrictor plate. I highly do not recommend his location.

So, you can go as cheap as $4 and choke your exhaust off real good. And have no boost creep, and a lot less power. Or you could go $20 like HKS did, and his process was much more reasonable.

Or you could buy a set of 3 developed plates, that are much higher quality. I sell them for $80. I'm not stealing, that's darn cheap for what you get compared to porting the wastegate.

Yeah, who cares about the quality, it's in the exhaust, you'll never see it. But, poor quality could lead to problems *you don't see*, and that can bite you in the ***. I've been a design engineer for an OEM for 8 years, 12 years of total design experience. I'm no genius, but I can see problems with some of these alternate ways to restrict the exhaust.

I'm not saying these other methods won't eliminate creep. But I am honestly telling you that my restrictor plates are better, and you will wind up with a better result.

I'm not trying to sell my plates, they're a PITA to make. I'm down to 2 sets right now and I'm not looking forward to making more. But I will, and they will be done right. I don't & won't sell crap.

Lastly, if my plates don't work for you, you can send me all 3 back and I fully refund. Of course, I haven't had to do that yet.

Check out the link below in my sig ... if you haven't already.

MILOS7

iTrader: (3)

Nice

jonnyrx7

iTrader: (9)

just port your wastegate yo