speeddemon7

Ok so Im contemplating running a midpipe if only for a little while to see how the car would perform with one on.The problem is that I dont want to go through the huge hassle of porting the wastegate.Which means I would have to remove the turbos and that just sounds like a big pain in the ***.Ive read somewhere that some people make restrictor plates that they install between the downpipe and midpipe.I would really appreciate some more insight on this technique.Heres a few questions.
First,what size hole does the restrictor plate need to have? 2 and a 1/4 inch maybe?
Do I need one restrictor plate on each end of the midpipe?
What kind of horsepower gains can I see with this modification if any?
I already have a midpipe as it came with my downpipe as a set from TSUDO.I figure I might as well put it to good use.
Thank you all for your help.

Montego

iTrader: (1)

Depending on your mods you may not get any creep at all. IMO adding a restrictor plate kinda defeats the whole purpose of the midpipe. Meaning that you don't get the most out of it.

I am running a midpipe, DP, and a stock muffler.
I do not get any boost creep.

ZeroBanger

I ran a midpipe, ported engine, apexi N1 Duals, downpipe, Rx7fashion intake and midpipe using a power FC to control boost and never had boost creep. Took it to the drag strip many times. Sometimes I ran my N1 Duals, other times my HKS Turbo exhaust.

also, I did this with 2 sets of turbos and 2 engines. Probably more than 80 runs at the dragstrip.

Boost spikes? YES, Creep? NO.

Mikey

i ran a midpipe and dp and didn't spike or creep ever

yzf-r1

iTrader: (1)

I run a full open exhaust because I'm a tree hugger environmental engineer

I do get some creep on WFO runs, especially on cold nights, so set your boost controller a little lower, no biggie....in the summer it is rarely a problem

Montego

iTrader: (1)

You mean for spikes right?

matty

no creep or spike....power fc baby baby.

tt2323

I would think just 1 restriction plate, not sure the size

Your Tsudo dp/mp combo may only work together (dp may not work with stock cat, some are like this)

35lb weight reduction

DamonB

I hope so. If you've got creep it doesn't matter what setting you have on your boost controller...

speeddemon7

tt2323.My tsudo downpipe is already installed without the midpipe.It fit perfectly.So theres no issue there.I guess a list of modification would help.
I have a blitz intake and catback and also a tsudo downpipe.Im also running a greddy profec b spec 2.Hope this helps.So you see I already have 3 mods and the midpipe will be the fourth.So I will need some kind of restrictor plate.Or at least I think so.A power fc is nice but its not an option that I have right now.Thats why im looking at the restrictor plate idea.Thanx everyone for your input thus far.I hope to hear from you again.

speeddemon7

given the curent info what size restrictor plate do I need? and will it be enough for my wastegate to function correctly?

FDNewbie

iTrader: (10)

bro, montego pretty much said it flat. I don't see WHY you'd put a midpipe on if you're going to use restrictor plates. Not trying to get on your case, but you replace the cat w/ a MP to *remove* the cat's restriction. Placing a restrictor plate will re-establish that *restriction.* So essentially, it would be a complete waste of a MP. Unless there's another reason on your mind, you should just go w/ a high-flow cat to ease your mind.

If you're willing to take the testimony of many of the people who have posted in this thread, including mine, then put on the MP, forget the restrictor plates, and drop your boost down a notch, and tune accordingly. You also said you're running a profec 2...so you're pretty much set.

I'm running a Power FC, M2 intake, Pettit DP & MP, and HKS Carbon-Ti Exhaust, so my exhaust is VERY free-flow. Stock wastegate, no boost controller (yea, not smart lol) but I'm getting no creep or spike. Just be careful when you're doing spirited runs on cold nights...

yzf-r1

iTrader: (1)

no boost controller (yea, not smart lol)

definitely not smart! at least get a manual boost controller you can adjust from inside the cockpit....

that's how I blew my first motor, I knew I was on the edge but I was in the middle of a good street race with a WS6 and didn't want to let off

I won, but it cost me $5500

TracyRX7

As FYI...

Creep = wastegate not large enough to keep the boost down when fully open

Spike = boost goes up faster than the wastegate can open to control it

And running DP/MP with the stock exhaust (which is 2.5" and very restrictive) is the same or more restrictive than running DP/2.5" restrictor plate/MP/3" cat-back.

If you are going to do the MP at least do the Home Depot Boost Controller if you don't have a different one.

yzf-r1

iTrader: (1)

what I mean is I set it conservatively (about 13) to allow for some creep, especially in fourth gear....for whatever reason I always get an extra 1/2 psi in 4th

CCarlisi

My friend had creep and solved the problem by putting a flange with a 2.5in inlet between the midpipe and downpipe. This is the same size as the inlet on the stock cat. However, it still flows better because the air does not have to pass through the cat brick.

FDNewbie

iTrader: (10)

yzf-r1, yea I know...but I'm on the verge of getting a new engine (mine's starting to lose compression), so I'm not too worried lol

Oh and that's definetly a VERY expensive race man...

CCarlisi, that's why I worded what I said carefully. I didn't say that it's the SAME as running the cat...but you'd be re-establishing restriction nonetheless. I bet your friend would have had very similar results had he replaced the MP + flange w/ a high flow cat.

That, and for the most part, when you're running wide open exhaust, you're doing just that...running it *wide open.* You wanna lessen the restriction as much as possible, to sqeeze every last hp outta that baby hehe. So all I'm saying (again) is that if you're gonna use a MP, get everything you can out of it, and use a boost controller (porting the wastegate may also be necessary in certain situations). Otherwise, if you can deal w/ a reasonable amount of restriction, but def. less than the stock cat, and don't want to worry about boost creep and spike, just use a high-flow cat.

SPOautos

Who cares....creep is your friend haha

just get a PFC and tune for that **** lol

If you cant keep it under 16psi then dont worry, just turn the boost up to 16psi and tune for it

You'll like it I promise haha

STEPHEN

yzf-r1

iTrader: (1)

just not with the stock turbos or the stock injectors

Bucrx7

I have a ported motor, non-sequential and ALL bolt ons, I have my EVC4 set at 10psi, no creep here.

speeddemon7

thanx for the input guys.As I stated earlier.I already received a midpipe when I got my TSUDO downpipe.It came as a set.So there would be very little expense in running a midpipe with a restrictor plate and I was also thinking that although it may not flow like a true midpipe it should increase flow.Since the exhaust gases wont have to flow through the cat bricks.In theory it should flow considerably better.

cruiser

I ran restrictor plate for some time, thinking I need it. I removed it recently and no side effects (apart from some free HP). I have stock (or something very similar to stock) catback with crushed pipes though. I'm getting full 3" exhaust (now have 2.5" midpipe) and will see if I need to port my wastegate... I'm worried about cold days, so I need to take it with care.

MichaelFregoe

iTrader: (1)

Creep is a result of flow between the turbo compressor, intercooler,engine, turbo's and the exhaust. I had creep badly after the installation of my custom y-pipe and intercooler. I had all the other stuff: Intake, DP,MP, Cat back. If some of you are not getting creep then I may suggest that your intercooler and y-pipe may not be the most free flowing.

I have been told by several RX-7 shops that severe boost creep like I had would bever be cured by porting the wastegate or getting a different boost controller. I had to go back to a catalytic converter. BUT a MP with a restrictor plate is better flowing than a converter, even a "high flow" converter. So a MP with restrictor plate will give you more HP than any converter but slightly less than a 3 inch midpipe.

SoloKK

Me Too, except I have a manual boost Controller. Runs fine.

speeddemon7, just spend the money and/or time before you regret it.

speeddemon7

wow.old thread.I havent put on the midpipe just yet as im scared for my 110,000 mile motor.Im also experiencing some kind of boost leak or exhaust leak.Because the car with the boost controller off is only boosting to about 6 psi.It should be boosting somewhere closer to 7 to 7.5 psi.
I have to fix this first before even attempting anything else.Otherwise I may regret it.