[wogboy]

Hey Guys,
This is my first post on the new look website... flash haha! Anyways Im building myself up a DDP as we speak but ive come to a fork in the road. Can't decide if i want it FULL 3" or FULL 3.5" from the turbo back. I really want to go 3.5" for the DDP because it will be easier for me to build... but it does cost a significant much more for the piping. Im mainly looking for opinions here but it would be great if anyone has any experience running between 3" DDP and 3.5" DDP's?!?! Any help would be usefull. Thanks in advance :bigthumb:
Oh P.S. its for my CT with 60-1 trim upgrade.

 

[supraboy77]

turbo back, bigger is always better.

save a bit more and go with the 3.5".

 

[toyota_supra_1988]

bigger is usually better. but a 3inch will do just fine

 

[wogboy]

Made a decision... me thinks!

Thanks to all that replied or even took the time to have a look. I woulda liked more feedback but i think ive got it figured out. Im going to come to a comprimise between power/cost/ease of build/and maybe loudness too...
My exhaust will have 3.5" with DDP straight off the back of the turbo but just before(or after, havent decided) the lower bend in the DP ill reduce it to 3" and that will flow through to the back.
This way ive figured out ive got a nice high volume area for the exhaust coming straight out the back of the turbo so i will have little back pressure there, and converting to 3" further down will save me on cost without losing very much "free power". Any further comments/ideas/questions are indeed welcome.

 

[IdealSupra]

turbo back, bigger is always better.

save a bit more and go with the 3.5".

negatory...

HOWEVER...if it wil be cheaper for you to run the 3.5 then do that...as it wont hurt anything...

BUT with just a 60-1 3.5 inch piping is useless....when 3inch is readily available...

 

[flubyux2]

do 3" from the turbine outlet to the first bend. getting a 3.5" elbow and mating it to the CT26 flange is going to be difficult do the the tight radius required to clear the "bulkhead" and also the fact that the CT26 flange only accomodates a pipe that is 2.5" wide. you simply cannot weld a 3" or even 3.5" to the flange and expect to have clearance for the studs/nuts and socket over the nuts for installation.

 

[supraboy77]

negatory...

HOWEVER...if it wil be cheaper for you to run the 3.5 then do that...as it wont hurt anything...

BUT with just a 60-1 3.5 inch piping is useless....when 3inch is readily available...

negatory? i'm curious what possibly is wrong with what was said. are you trying to say that you want more headloss in a exhaust system?

the only possible drawback is clearance.

 

[IdealSupra]

negatory? i'm curious what possibly is wrong with what was said. are you trying to say that you want more headloss in a exhaust system?

the only possible drawback is clearance.

no im saying you still need exhaust gas velocity... as long as it flows nicely the bigger the better is not necessarily true...if that were the case everyone would run open turbo... and be done with it...

its been dyno proven that 3.5inch on a 300hp car is not better at all (read: worthless) then a 3inch pipe.

3.5inch benefits in the upper 400ish+ range...and 4inch benefits in the 700+ range...

do some searches especially in the mk4 section and you should find everything...

physics are physics are physics

i do understand what you are are saying though...but it doesnt hold water for a lot of smaller turbos...especially a stock upgraded one...

 

[wogboy]

Can't fit? Haha your right the 3.5" wont just slap on the back of the flange ...BUT it will fit if is shaped into an oblong where it connects to the flange... Almost! Almost is where the DDP comes into play :bigthumb:
Im not a ricer looking to get some loud noise with my exhaust, ive thought this through, designed it on paper and even knocked up a proto type thing in the shed! Although i admit i havent been as thorough when it came to clearance it does not look like ill have problems... Pretty sure... better look into it a bit more now... you guys have me paranoid now! lol
Thanks for the input especially Ideal and Fluby, love your cars and the work youve done... big respect!

 

[QWIKSTRIKE]

You guys make me laugh with the rediculous things you say and ask! You all mostly think to just slap something big on the car, and then you are the speed freak incarnate! :wtflol: Why don't you, and mostly everyone serach to find out how a car really works, and then come back, and ask enrichening questions that you need to know. A lesson 101 in basic car operations is a must! :eek2:

 

[t51rjohn]

youve gotta match up the whole exhaust system intake turbo etc to the kind of power you want/need!!

 

[Robbman]

physics are physics are physics

Feel free to explain with equations at any time.

 

[Johnny Dangerously]

Feel free to explain with equations at any time.

physics=physics=physics....duh :bigthumb:

 

[supraboy77]

no im saying you still need exhaust gas velocity... as long as it flows nicely the bigger the better is not necessarily true...if that were the case everyone would run open turbo... and be done with it...

its been dyno proven that 3.5inch on a 300hp car is not better at all (read: worthless) then a 3inch pipe.

3.5inch benefits in the upper 400ish+ range...and 4inch benefits in the 700+ range...

do some searches especially in the mk4 section and you should find everything...

physics are physics are physics

i do understand what you are are saying though...but it doesnt hold water for a lot of smaller turbos...especially a stock upgraded one...

it's pretty common knowledge that running an open downpipe will result in more power, thus the bigger exhaust will prove beneficial. especially since he is running an upgraded ct26, a 450hp turbo.
gains may be marginal on a stock turbo, but there would still be gains.

and yes physics is physics. larger pipe = less headloss = more power.

 

[IdealSupra]

it's pretty common knowledge that running an open downpipe will result in more power, thus the bigger exhaust will prove beneficial. especially since he is running an upgraded ct26, a 450hp turbo.
gains may be marginal on a stock turbo, but there would still be gains.

and yes physics is physics. larger pipe = less headloss = more power.

relatively wrong...

yes open downpipe will result in slight gains..however thats STOCK downpipe.... if the downpipe flows correctly...a full exhaust will gain more hp...

dont believe me? ask becauseican about his dyno tests...he lost like i think 5-15hp i dont remember the exact number...when he pulled the catback off of his downpipe....

you need EXHAUST GAS VELOCITY!

i completely stand by what i said before...

 

[OneJoeZee]

relatively wrong...

yes open downpipe will result in slight gains..however thats STOCK downpipe.... if the downpipe flows correctly...a full exhaust will gain more hp...

dont believe me? ask becauseican about his dyno tests...he lost like i think 5-15hp i dont remember the exact number...when he pulled the catback off of his downpipe....

you need EXHAUST GAS VELOCITY!

i completely stand by what i said before...

-_-




taken directly from the MK3 FAQ about turbo exhaust....

and i quote

"Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure. "



-joe :run:

 

[IdealSupra]

-_-




taken directly from the MK3 FAQ about turbo exhaust....

and i quote

"Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure. "



-joe :run:

what is your point here? they are speaking of back pressure IMO thats how i translate the use of pressure....with n cats and smooth flow you have VERY LITTLE back pressure...

you still need that exhaust gas to stay in the turbine LONG ENOUGH to actually turn it...if you ran open turbo...it just kick out with nothing staying in spooling the turbo...it NEEDS something there...

how come all the drag turbo cars dont run open exhaust side on the turbo? for this exact reason...the run a nice big pipe and have it come out there side further down or the back like normal....

why is it NO ONE understands the concept of exhuast gas velocity...im not gonna KEEP teaching the concept over and over again...i feel like im making this arguement at least once a week.

but just like i said in the 3inch exhaust on the NA tthread...you guys do whatever the fuck you want...i do what i want and we can all be happy...i could care less if you dont maximize your performance....

 

[OneJoeZee]

thanks mom



-joe :run:

 

[toyota_supra_1988]

you guys both make good points. right now im confused lol. I dont know whos right. But i would just say get a 3inch dp, i dont think your going to be making enough power for it to make a big difference right?

 

[IdealSupra]

i just wanted to make another point....

keeping the exhaust in the turbine will create the heat necessary to speed up the gas velocity even more....