Montego

iTrader: (1)

I know that you set your boost at 16 lbs and you don't have any creep issues at that boost level. But what happens when you are at 10 psi? Are you still rock solid?

Reson behind my question:

Back when I still had my twins and I had a FULL exhaust (DP, Resonated MP, CB) and if I ran low boost (10 psi), eventually on the long gears I'd creep to 12 psi (my turbos were ported btw). But whenever I ran high boost 12 psi+ my boost control was rock solid.

I'd like to point out that the creep never bothered me because I WAS TUNED for 17 psi...

Devlian

sorry if this is a dumn question but, if the exhast is looped back to the intercooler an into the turbo before the cat, how would increasing flow behind the loop afect the turbo? aside from a loss of pressure in the exhaust manifold thus causing your turbo to actually spin slower,

fendamonky before you make another sad attempt to flame me, please look up "Bernoulli's principle".
And yes english is my first langauge. and I'm sorry I use things such as grammer and punchuation.

Sgtblue

iTrader: (16)

*Exhaust is not connected to the intercooler in any way. The intercooler is on the intake side.

*Too little restriction/back-pressure in exhaust flow can overwhelm the stock wastegate. The surplus flow will then be forced to exit through the turbines, creating an unintended increase in boost pressure. That's called Boost Creep. Too much of that can cause a lean condition and detonation.
Porting the waste-gate to increase it's ability to handle the flow, or re-introducing back-pressure into the exhaust is traditionally the only way to control boost creep. On stock twins, the wastegate is internal and requires removing the turbos to access.

*I'm just a dumb civil-servant but as far as I can tell, Bernoulli's Principle really doesn't apply to the above.

Devlian

thanks I was totally wrong on the principles of a turbo setup. *blushes* I thought the intercooler was used to cool exhaust gasses that were fed back into the turbo to increase the avalible drawn air. The way Bernoulli's Principle applies is air travels under the same principles as fluid. If you restict room for flow then psi will increase if you increase the amount of flow then psi will drop. think of it as putting your thumb over the end of your garden hose, the water increasing in pressure an thus srays out rapidly as were if you remove your thumb it just pours out as normal.

okay not trying to nuke it but, with a more easily flowing exhaust it causes a build up of pressure on the intake side of the turbo thus forcing the waste gate to blow off more then intended? does boost creep cause a increase or decrease in psi to the intake manafold?

jplecas

iTrader: (1)

The wastegate doesnt vent pressurized air. It vents exhaust, to stop spooling the compressor. & Boost creep causes an increase in manifold pressure. Because the exhaust is more free flowing. causing the turbo to spool a couple psi higher than intended.

As for hi flow cat vs mp.. ive been running a mid pipe for the past month or so, but recently ive been thinking I should put on this hi flow cat ive had laying around.

Mid pipe pros.
-noticable power gains
-super lightweight
-sounds as fast as it really is ;]

MP cons.
-STINKs
-smokes
-boost creep
-not street legal..
-can be quite loud near redline



Hi flow cat pros..
-Legal
-no boost creep
-I know mine is for sure lighter than the stock cat.
-none of that "your car stinks!!, or.. "nice smokescreen on that last pull"
-Probably wouldnt set car alarms off like it does now

Hi flow cat cons
-performance loss over midpipe
... what else?

And this is why I am thinking about just putting mine on instead of the midpipe. I like it but maybe if the car was tuned properly or it didnt stink/smoke so bad..


It all depends on what you use the car for..

fendamonky

iTrader: (6)

Seriously? Dude, I'm trying to keep you from blowing your **** up. Instead of your response, how about this: Before you make another sad attempt to call me out, you do a little research so you know what you're talking about (loop the exhaust into the intake?!?! Sorry bro, before you ask, we're fresh out of blinker fluid too)..


Should I even bother pointing out the irony in these two sentences?

(Before you form a retort to this, please go sit in on a Middle School English class. You may pick up a few skills regarding spelling, grammar, and the correct usage of words in the English language. Your obviously weak grasp of these is what made me question your primary language to begin with, you'd have been better off saying English was your second language..)

staticguitar313

iTrader: (2)

Hmmm well I've got the same problem, I have a straight through mid-pipe and I'm trying to figure out if i should run it or not, my waste gate is already massively ported.

Also which high flow cats are worth buying?

fendamonky

iTrader: (6)

I feel that the difference between newbs and idiots is that newbies don't know right from wrong, and therefore they rely on the more experienced members to educate them and point them in the right direction. If you initially learn something, and what you're taught is incorrect or incomplete then you will start off well behind the power curve. If the correct, detailed, information is put out the first time (under the assumption that the recipient knows little to nothing) then the person learning will be MUCH better off, because even if they don't know much what they do know is undeniably correct.

I'd rather assume the person asking the question knows nothing, so when we give an answer we cover all bases, negating the possibility that they learn the wrong thing the first time.


Idiots have been taught better, but do the wrong **** anyway.

There is not a direct push/pull effect between the exhaust gasses and intake air like it seems you're guessing. At no point will the exhaust gas come into direct physical contact with the intake air. The connection between the two happens inside the the turbo by means of the fins on the exhaust side and the compressor side which are connected by the shaft.

To answer your question, as I understand it free flowing exhaust reduces backpressure, which will in turn allow the exhaust gasses exiting the engine to flow faster, resulting in a faster, more responsive spool up time on the compressor side.

(Read the book "Maximum Boost" by Corky Bell, it will break down just about anything you'll ever want to know about turbo chargers, and how the systems work)

Boost creep is where max boost is attained, then the max psi continues to "creep" higher through the rev range until you let off the gas, or shift gears.

Earlier this year when I swapped my MP (non resonated, just a three inch tube of steel) for my High Flow Cat in order to pass MOT (inspection in the UK) I noticed that my turbo's spool time seemed more sluggish then with the MP on.

fwiw I'm running a completely free flow system, DP/MP/Apexi N1 Duals... It's loud as hell, but I like it =P

fendamonky

iTrader: (6)

My personal preference is for a MP, but then again, I'm tuned for it and I've (intelligently) thrown enough aftermarket/supporting mods into my car that I can reliably DD my FD at 400whp, on twins. I added my MP the second time I took my car in for a re-tune. That was about a year and a half ago.

staticguitar313

iTrader: (2)

Yeah i'm just not sure if the stink will be worth it, i have all the supporting mods already in place.

jplecas

iTrader: (1)

From your second post I am assuming that, to make this much power you were running the twins non sequentially? That would explain the lag you were getting with the cat on. with my sequential twins i cant really tell a difference in lag, even from a stock cat.

Sgtblue

iTrader: (16)

I don't have anything to compare it to, but my Bonez hi-flow is over 7 years old. Materials and construction are great. Good thick flanges, stainless and much more compact than OEM. Because I've been running without an airpump for about a year and a half, I took it off recently to do a visual. As far as I can tell, it's been unaffected.

fendamonky

iTrader: (6)

I'm running my twins fully sequential. The reason why I say the spool up is slower is rather particular and my specific circumstances allowed me to notice it.

Basically my stock solenoids are fucked (and getting slowly worse), or so I've determined based on the information available to me. Initially it stared where my primary turbo would only boost to 7-8psi, then when my secondary came online the boost pressure would shoot up to 12-13psi. This was on my stock twins. The initial assessment said that my primary turbo was "knackered and lazy" aka fuxored. So I ordered BNR's, and a whole other slew of goodies to support the upgrade in all regards (about $8-$9k worth thanks to a deployment to Afghanistan). Prior to having everything installed and re-tuned I took my car to one of the top rotary specialists in England and had them look her over, just to make sure nothing was wrong except the turbo's.. Everything checked out (my compression was from 8.6 to 9.1 on all faces even!) aside from the lack of peak boost on the primary. Initial tuning was also done at this time, so I'd have a baseline to measure progress insofar as power.

I then took my car, and all my goodies, down to have the install done. At the end of it all I had the car tuned to 1.16 bar and went from 280whp to 325whp (before you comment on the low power figure, the dyno this was done on shows an average of 15-18% lower numbers then is common and accepted in America), however I still had the lower primary boost. Now I hit 12-13psi almost immediately, but didn't see the 16psi until the secondary came on line.


Unfortunately I've not had time to fix my own solenoid problem yet (I'm in the middle east, again) and it is becoming progressively worse regarding the primary turbo's response.

However one thing has remained constant, the transition from primary turbo, to secondary turbo. As soon as I hit 4k my needle jumps from 12psi to 18psi (the addition of Water/Meth injection, then later a huge VMIC took me from 16psi to 17.5-18psi) in a snap. When I switched the High Flow Cat into position that "snap" slowed by about half...



The amount of backpressure an exhaust system creates isn't the only contributing factor to lag or boost response, however I feel that does play a, not so significant, role. Other things to keep in mind are IC pressure loss, length of IC piping between turbo and intake manifold, amount of 90 degree bends in piping, etc. *should* also effect pressure loss and boost response.


I'm gunna stop ranting, lol.


Bottom line is that if you are properly set up then a free flow exhaust system is superior to any kind of cat when it comes to power and performance. If you are not properly set up then a free flow exhaust system is one of the quickest ways to have an opportunity to port your engine

purerx7

iTrader: (61)

1. Read this
2. Understand it
3. Re-read it

That is the most important thing to know and fully grasp before ascertaining a midpipe. An aftermarket ECU, such as the PFC will NOT stop boost creep. In a really, easy to understand flow chart:
1. Full Exhaust + PFC
2. Boost Creep to 16psi with what I am assuming is on a base map for the PFC
3. BOOM! Blown motor.

People can run their mouth all day long, I have seen it over the past 5 years how people run full exhaust with no problems on the stock ecu. That is rubbish, and people are either living in fantasy land or are talking out of their ***. Unfortunately, this clutters the forum with incorrect information and causes others to believe that is correct.

Look at all the veteran members here, they all say the same thing. If you are getting a midpipe you NEED to port the wastegate on the stock twins, NEED boost controller and you NEED to get the car tuned. Don't cheap out on parts that will cost less then $800 when a new motor will cost you $3,000 at the minimum.

My suggestion would be for a metallic cat, expensive but well worth it IMO, you can get these from SARD, Re-Amemiya SMB etc. I will be running a full titanium mid-pipe in the near future,however I have an extremely well muffled titanium exhaust that won't make it quite as loud.

Your best bet is to search the forums, this topic has been discussed at least 50 times, if not more.

blizzaga

iTrader: (2)

^ Agreed. At first I just said yes put on a MP and set it and forget it. I didn't mean that you didn't have to port the wastegate, get a boost controller and get a good tune. I just merely answered your question based on what I felt. My bad. Consider what everyone says about it being loud & stinky and figure out if this is what you want. In my opinion...and my opinion alone, the noise may be a bit of a problem but the smell doesn't bother me.

BTW Purerx7, where are you getting your titanium midpipe? I'd really like to get one.




~Shar

DeeSan

iTrader: (2)

hey I'm interested in this one too

purerx7

iTrader: (61)

If I told you two, I have to kill you....

Getting it either from R-magic or having it custom made it Japan. Should sound nice going into my ARC full ti exhaust. R-magic offers it in two versions
1. a straight pipe
2. with cat
MSRP on those is $500 and $1300 respectively. The straight pipe probably weighs about 2.5lbs. Never came across a used one so can't really get pricing on them.


Their are also full titanium systems from the downpipe back from fujitsubo and Feed made a very rare ti-94 full ti exhaust a long time ago, believe the whole system weighed less then 9lbs.


Sometimes I amaze myself with how many useless things I know.

Ceylon

iTrader: (3)

I ran a midpipe with stock DP (jap DP) and held 1bar solid. I also know 2 people who have ran full exhausts w/o issues or ported wastegates. Maybe its just the fact we were running 1 bar?
Or something else?

gracer7-rx7

iTrader: (16)

Yeah that helps. Trying to control boost to more reasonable levels like 10-12 PSI becomes a challenge. Not having enough fuel and larger injectors and higher flowing fuel pump at higher than 10-12 PSI = blown motor.

I always got boost creep in higher gears with a midpipe / resonated midpipe. Especially in the fall and winter when ambient temps were cooler (denser air) and the turbos spool easier.

matty

well to be completely factual the answer is i dont know. i havent ran that boost in yrs but when i did it was ROCK solid at whatever boost i set it to. i am running her on the track in a couple weeks and only plan to run 12 psi so i will let u know if it still works and keeps boost in control.

there was a theory many yrs ago that stated only 93s got creep and mid 94 and up didnt. there was a thread on it yrs ago. alot of guys chimed in with no creep and they had newer cars. but then of course some did with creep. so the thoery failed ultimately i think. the thing is the mechanics are the same..so.....

matty

fair enough

matty

what is the benefit of a titanium mp?

weight savings would be nill.

Montego

iTrader: (1)

thanks for answering matty

purerx7

iTrader: (61)

1. Minimal weight savings
2. Look at me I have a titanium midpipe (aka baller status)
3. IMO you can hear a difference between a titanium exhaust and a SS exhaust, not sure how that theory holds when it comes to midpipes, I will find out soon. This is coming from someone who has tested over 8 different full titanium exhausts on his car.

Julian

iTrader: (14)

hi flow cat. save some air