HYBRID_H@TCH

well Iam at a point where my 3 inch downpipe/exhaust has become a restriction but I cant afford to go 4 inch for another 3 weeks..and in the mean time I want to go to the track and have some fun..so my question is..

would a 3 inch open downpipe be about the same as a full 4 inch downpipe and full 4 inch exhaust? I think it would be close to the same but before I hack away at most of my downpipe and pull the exhaust off I just want to make sure Iam not wasting my time..

EKB18BPR3

no no 4 inch and open pipe isnt the same. u may think 4 inch exhaust system has no restriction but it does. the characteristics of spent gas moving out into the open pipe has an outward motion in all directions, yet the spent gas going through a 4 inch system has only one way to go, thru the pipe from front of the car all the way to the back. open gas out let out lot more than a 4 inch system. but if ur at a point where u gotta upgrade from 3 inch to 4 inch, u may as well just run open pipe and get it tuned...unless this is ur daily driven vehicle.

HYBRID_H@TCH

Thank you for the reply.

I was thinking the open DP would be better but thought maybe because of all the pressure trying to escape at once thru a smaller pipe it might restrict it..so..Iam going to hack my exhaust off tomorrow and run a side exit downpipe for now..and yes its a street car..just driven to and from my shop and to the track and back.

wolfsburg2

I think a more realistic question is would a 3" downpipe with no exhaust flow better than a full 3" system. My answer would be yes

Arturbo

I personaly think you'll be fine with the 3". I think joe simpson runs a 3" exuahst on his 10.0 coupe. I say run it..

art

HYBRID_H@TCH

well see thats the thing..I cant get it to boost right with my 3 inch exhaust on. I called Precision and they said I need bigger exhaust, 81 a/r hot side (have a .68 right now) and to go from a 3an feedline to a 4an feed line..also Iam not getting full boost till 7000 rpm!!!

so Iam going to go 4 inch dp and exhaust..but want to just remove my 3 inch exhaust for right now and was thinking of just leaving a 3 inch downpipe and screw the 4 inch stuff.I dunno..to many choices..hehe

tony1

What size turbo are you using? For a 3" downpipe to be too small, it must be huge! You sure they weren't just saying you need a bigger exhaust side to the turbo?

HYBRID_H@TCH

PT71GTQ turbo..

the guy I talked to told me I needed all of that..I had told him about cortney green with the .68 a/r and 3.5 inch exhaust and they said they did not know how he was doing it..

tony1

Chuck ran 8.53 at over 170mph with that turbo (.81 ar) and a 3" downpipe.

He started with a .68 ar and it worked fine too, just wanted more power. The difference is he was running that turbo on methanol. I don't understand why everyone is trying to run that big *** turbo on a 1.9L motor on gas. Of course it's going to lag pretty bad. Full boost, assuming it's around 25-30psi, by 7k probably isn't to far off at all.

tony1

Just a note, if there is a flexpipe in your downpipe or exhaust system now, check it, i've seen a few of them collapse now. If it is collapsed, then you're going to pick up a good 100hp or so when you fix it!

HYBRID_H@TCH

well I had some fun today..I took the car down to my shop and pulled the exhaust off and cut the downpipe right before the flex pipe (looked like it was brand new still) and took the car for a drive..I ended up having to add about 8% fuel from vtec on and it has full boost (41 psi) at 5800 rpm now..car also feels like it got a new lease on life!!!

Thanks for the help guys..

DaveF

when you going back to the track??

tony1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 99Hybrid_Hatch &raquo;</TD></TR><TR><TD CLASS="quote">well I had some fun today..I took the car down to my shop and pulled the exhaust off and cut the downpipe right before the flex pipe (looked like it was brand new still) and took the car for a drive..I ended up having to add about 8% fuel from vtec on and it has full boost (41 psi) at 5800 rpm now..car also feels like it got a new lease on life!!!

Thanks for the help guys..</TD></TR></TABLE>

How big is your motor? I'd like to see a datalog of 41psi by 5800rpm!

HYBRID_H@TCH

1.8L with a 100 shot to spool the turbo.

edit.

nitrous is set to come on at 4500 rpm.

Turbocivic94

Tony, what do u recommend for the streets and SFWD. Currently I have T4/T67 w/.58 a/r which I was thinking about upgrading next year. I also run 4" downpipe and 4" exhaust.

4" is where its at

tony1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 99Hybrid_Hatch &raquo;</TD></TR><TR><TD CLASS="quote">1.8L with a 100 shot to spool the turbo.

edit.

nitrous is set to come on at 4500 rpm.</TD></TR></TABLE>

Haha, that explains it, a minute detail you left out! lol

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbocivic94 &raquo;</TD></TR><TR><TD CLASS="quote">Tony, what do u recommend for the streets and SFWD. Currently I have T4/T67 w/.58 a/r which I was thinking about upgrading next year. I also run 4" downpipe and 4" exhaust.

4" is where its at </TD></TR></TABLE>

How much power are you currently making? Do you really need to upgrade?

Turbocivic94

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">
How much power are you currently making? Do you really need to upgrade?</TD></TR></TABLE>

I'm getting my car tuned on july 9th by jeff evans. I'm shooting for around 700. Hopefully my turbo is not my limiting factor.
This is on 2 liter motor, external pump and 1000cc injectors

HYBRID_H@TCH

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">Haha, that explains it, a minute detail you left out! lol</TD></TR></TABLE>

didnt want to post it..but if Iam without exhaust anyways Iam out of nhra so screw it..lol

tony1

You should be able to make very close to if not more than 700 on that turbo. If anything i'd go to a bigger exhaust housing. I wouldn't start planning a new turbo out until that one has proven itself too small. Remember, Gardella and Lummus are running 7's on a 70mm turbo! lol

HYBRID_H@TCH

tonys advice is true..my turbo only takes a week and a half to spool..but when it does I make semi truck drivers look at me funny..lol.. a PT67 is a good turbo my buddy jesse is running the same turbo and he kicks my *** at lower rpms..

Turbocivic94

cool, I'l be holding on to the turbo. I get hyped seeing everyone running PT71GTQ

Turbocivic94

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">You should be able to make very close to if not more than 700 on that turbo. If anything i'd go to a bigger exhaust housing. </TD></TR></TABLE>

What a/r exhaust housing should I go for?

tony1

depends on how responsive you need the turbo. You should run it like that and check the boost response between shifts on your datalogs from a run. 1-2 sizes bigger has proven to work pretty good...

Turbocivic94

I'm running Neptune and I cant figure out how to datalog. Well when I go see jeff I'l ask him to show me how to use it. I already have the 4 prong and usb cable. maybe I need to get software for the cable and I already have Neptune datalogging software.

june

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">depends on how responsive you need the turbo. You should run it like that and check the boost response between shifts on your datalogs from a run. 1-2 sizes bigger has proven to work pretty good...</TD></TR></TABLE>

Ok since we are in the pt-71 topic. Tell me what you think I should do because I know I won't be happy with my t4-sc61 with s housing. I just want a turbo that I know I won't be able to max but still be happy at the same time.