sizes

[Jonas]

is 2 3/4 too big from the throttle body down to the end tank, and then use 2 1/4 for hot pipe???

[pressuredsol]

What size turbo? Engine? Boost pressure?

[Slash]

Stock T25. SR20DET. I'm guessing between stock and 10lbs boost..

[Just Dave]

It doesn't really matter. Use whatever size is easiest to route, buy, weld, fit whatever. There was an engineer that did all the calculations on different size piping and found the difference in "lag" was in the milliseconds over the average distance of I/C piping.

Just some basics though:

Compress air, it gets hot, let it expand, it cools off. My theory is to run bigger piping out of the turbo ASAP to expand the air and cool it that little bit more. But my main consideration was my I/C and TB were both 2.5" so thats what I used. :dunno:

[Cronic]

You may see more pressure drop using larger pipping as well.

[Just Dave]

Cronic, read what I said above, its all negligable. And also like I said, pressure drop means cooler. How much cooler? Not much, but then again, it works both ways. How much pressure drop will there be? Not much.

Plus, many turbo's include this nifty device called a wastegate. What this does is run 10psi no matter how big the piping is (within limits of course) so again, we're worrying about trivial shit.

Just use whatever is easiest and stop worrying about it. You'll have much more to worry about than the extra pressure drop a .25" bigger pipe will allow.

[flubyux2]

no, actually its not trivial. Boost is a relative term.

what you want to do is compare shaft speed at the boost that you are intending to run. cuz 70,000rpm @ 10 psi is giong to create less heat than 170,000rpm @ 10psi. its a matter of how much volume you are trying to push thru the pipe. you can have 20 lb/min of air at 10psi and 70000 rpm, and you can also have 32 lb/min of air at 10psi but be spinning at 170000 rpm.. boost is not the most important thing.

and the lag created by overly-large intercooler pipes and intercoolers does effect the operation of the engine...

for instance:

w/ stock intercooler and pipes, the engine expects the air counted by the MAF to reach the engine in, say, 4 seconds (for argument's sake). If you add a larger diameter pipes, longer pipes and/or a larger volume intercooler this will all add a delay in time from when the intake charge gets counted by the MAF and it actually passes thru the TB; this might take 5 seconds longer than the stock system did. now, the ECu thinks the influx of air is giong to be there in 4 seconds after being counted by the MAF, even though it Realy is still inside the intercooler... and now the ECU is going to add what it THINKS is the appropriate amount of fuel for that massive amount of air. all ths is going to do is cause the engine to load up and stumble and reduce the throttle response.

2.75" is going to be a little overkill for a litle T25, 2.25 would be a good size for it. but im sure you wont be keeping the little turbo. id go w/ 2.5" on both sides cuz its good all around size and will flow enough air for even a really mean ass setup... as long as you can live w/ the "negligible" amount lag.

i hope that helps :D

[Jonas]

ok i was thinking along the lines of....

turbo to end tank 2 1/4 and then towards the end weld on a little 2 inch piece for the silicone connectors because my end tanks are 2 inch

from throttle body to end tank... 2 3/4 about 1/4 of the way and then gradually make it to 2 inches...

2 3/4
2 1/2
2 1/4
ad then 2... because that is pretty much what the stock IC piping does so i would imagine doing so for a FMIC would make THAT much difference...

[Jonas]

bahh and actually along the lines of 11-12 psi...hopefully heh

[Just Dave]

Originally posted by flubyux2
no, actually its not trivial. Boost is a relative term.

what you want to do is compare shaft speed at the boost that you are intending to run. cuz 70,000rpm @ 10 psi is giong to create less heat than 170,000rpm @ 10psi. its a matter of how much volume you are trying to push thru the pipe. you can have 20 lb/min of air at 10psi and 70000 rpm, and you can also have 32 lb/min of air at 10psi but be spinning at 170000 rpm.. boost is not the most important thing.

and the lag created by overly-large intercooler pipes and intercoolers does effect the operation of the engine...

for instance:

w/ stock intercooler and pipes, the engine expects the air counted by the MAF to reach the engine in, say, 4 seconds (for argument's sake). If you add a larger diameter pipes, longer pipes and/or a larger volume intercooler this will all add a delay in time from when the intake charge gets counted by the MAF and it actually passes thru the TB; this might take 5 seconds longer than the stock system did. now, the ECu thinks the influx of air is giong to be there in 4 seconds after being counted by the MAF, even though it Realy is still inside the intercooler... and now the ECU is going to add what it THINKS is the appropriate amount of fuel for that massive amount of air. all ths is going to do is cause the engine to load up and stumble and reduce the throttle response.

2.75" is going to be a little overkill for a litle T25, 2.25 would be a good size for it. but im sure you wont be keeping the little turbo. id go w/ 2.5" on both sides cuz its good all around size and will flow enough air for even a really mean ass setup... as long as you can live w/ the "negligible" amount lag.

i hope that helps :D

Thats a touching story but why don't you show us some hard numbers on this? Like I said in my first post, a Doctor in the area of thermodynamics (which I'm sure still isn't as smart as you on this subject :roll: ) made very specific calculations and found differences in pipe diameter to affect spool in milliseconds. Can you count milliseconds? RUN WHATEVER IS EASIEST

[flubyux2]

Thats a touching story but why don't you show us some hard numbers on this? Like I said in my first post, a Doctor in the area of thermodynamics (which I'm sure still isn't as smart as you on this subject ) made very specific calculations and found differences in pipe diameter to affect spool in milliseconds. Can you count milliseconds? RUN WHATEVER IS EASIEST

Dude, dont be a dick. Im just tellin it how i see it. If you want, go Talk to BoostinEJ20 on AIM and ask him for a ride in his car: he just installed some new, longer, larger diameter intercooler pipes and a big front mount on his WRX and now has a stumbling problem and his car loads up on fuel... he has that exact problem right now. the amount of time DOES count, even if its "only" milliseconds. the amount of on-time for an injector is only a few miliseconds, but if it comes on TOO soon, and the air isnt in the engine to accompany that amount of fuel, itll stumble. its like having an Accelerator pump of too big a volume on too small an engine: itll stumble when you step on the gas and load up... so, pardon my language, but piss off. Im not trying to one up anyone here, im just telling you from my "Extensive" First hand experience w/ factory turbocharged vehicles... like DSM's. I dont need a doctorate :nerd: or even a BS in thermodynamics to know what goes wrong on a car after certain mods.. Im not a freakin idiot :tard: ... so lets cut the shit and how bout you stop being condecending. ;) ok bud?

theres no reason for you to be rude. Im just callling the shots like i see it... please dont get upset w/ me if i bring up points and facts that contradict your input... :deal:

oh, and i wasnt quoting time periods like they were precisely measured... i was making up numbers for Argument's Sake... i guess you missed that part. i dnot need to count in miliseconds to prove my point.

now, lets all get off our pedestals and thrones and get some beer and put all this bullshit behind us. :beer:

[Just Dave]

Werd. I'm just tired of not being right because I don't own an SR swap or work at SS. I guess I'm getting defensive. Either way. I've got some friends looking for the paper he wrote and I'll post it when I get it.

[flubyux2]

Nah dude, its cool. i know what you are saying... every body and their brother has an S13 w/ a swap... and we are freaks if we go our own way... well, i guess moreso you than me... w/ the 2.3 motor.. Im still considered mainstream w/ my supra and Rx7 and the old lady's DSM.

Im still impressed by the 2.3 selection

anywho, very few peiople realize how big of a window in time that a Milisecond is... like for instance "Tune your NOS timer, lengthen your injector pulse a milisecond or two" ... WHAT THE FUCK? a whole milisecond???? even fractions of a milisecond can make a world of difference in functionality and driving characteristics... but at least theres some peeps who know that too big of an intercooler and pipes will adversely affect the operation of a motor and its driveability...

my other friend had that problem in his 180sx... he had a HUGE GReddy front mount and like 2.75" intercooler pipes... that thing stumbled so bad down low and during initial throttle tip in and didnt even want to idle... then a split second after teh throttle was tipped in, it would pull... definitly intake lag. so, this does happen in real life.

[722ish]

Originally posted by flubyux2
. If you want, go Talk to BoostinEJ20 on AIM and ask him for a ride in his car: he just installed some new, longer, larger diameter intercooler pipes and a big front mount on his WRX and now has a stumbling problem and his car loads up on fuel... he has that exact problem right now. the amount of time DOES count, even if its "only" milliseconds.


:testimonial: i always thought this could be directly involved with the mass air flow sensor, but this stumbling problem NEVER occurs with the car cruising in gear albeit say at 1700 rpm.. but if i stab the throttle @ idle and even past 1700, it loads up on fuel, backfires, and sends the rpm straight to the bottom, all the while showing some crazy readings on the boost gauge... :( if i remember correctly, you are the guy i met at dave's (merkur) house Force Fed... if so, next time you are over there, have dave get ahold of me...Im the guy with the RFL BOV by the way... its an easy to recreate situation :) im not trying to play sides here, but the idea seems logical..... the more total volume to fill, of course lag changes... at least you would think... i have more lag, but my turbo got bigger as well, so im not sure how much each thing changed any car characteristics...
now my next question would be...can i make the MASS AIR a blow through rather than draw through? it sounds like a cherry idea, but i dont know if it would work or not...


Also, about the theory to increase pipe diameter directly out of the turbocharger..... given, the idea of cooler air works, but at what point does lag come into it... not only that, but say you have larger piping... doesnt the charge air velocity change? this in other words could either be a pressure drop, or lag time... i cant decipher which as i am too tired... the main thing im getting at is... the bigger the piping might generally = more lag regardless of pipe diameter, unless a given range is used.. i doubt the gain/loss would be noticed in a system that changed a quarter inch.. but, it might. fortunately for all you, im no physicist, so my word isnt taken all to seriously.

[Enthalpy]

Jonas:

turbo outlet is 2"

TB inlet is 2.75"

finding 2.75" piping is difficult. my suggestion for your power needs would be 2" to the IC (since you have a 2" turbo out and IC in). then run 2.5 to the TB, and put a 2.5-2.75 increaser on the TB.

most aftermarket IC kits for S13 run 2.75 (70mm acutally) from IC to TB. and 2.5 or 2.75 from hot side fender to IC. upper hot pipes are either 2" or 2.5 depending on manuf.

as for the lag issue with large piping.

here are some hard numbers: assuming a 1998 cc motor. operating at 100%v.e @ 3000 RPM. next we ahve to assume that IC volume does not change, and lastly that there are negligible additional losses from reducing or increasing couplers. also we can say that our IC piping is 9 feet long. 4 down, 2 across (not including core), and 3 up.

motor ingests - 106 cubic feet per minute of air
or - 1.766 cubic feet per second

- 2" inside diameter pipe has a cross sectional area of .022 ft^2
- 2.75" i.d. pipe has cross sectional area of .041 ft^2

at 106 cfm velocity through the pipes is
2" - 4818 feet / min
2.75" - 2585 feet / min

so the time for a complete traverse of a 9'-0" long IC plumbing system is:
2" - 0.11 seconds
2.75 - 0.21 seconds

so in theory the compressor flowing 106 cfm could completely replace all the air in the pipes in 0.1 seconds sooner with 2" piping. gosh i hate that pesky 0.1 second lag.

another example:

we already agreed that our engine is ingesting 106 cfm. that is 1.766 cubic feet per second. with a 9 ft long IC piping system our internal volume for the pipes is as follows..

2" - 0.198 cubic feet
2.75" - 0.369 cubic feet

difference of 0.171 cubic feet. at a compressor flow rate of 1.766 cubic feet per second thats 0.096 seconds difference!!!

so when it all comes down to it...it looks to be about a tenth of lag time difference at 3000 rpm on a 2.0 liter motor...i wouldnt get my panties all in a bunch over that.

Jonas...size the pipes however you see fit, you'll never notice the difference!!

[Enthalpy]

oh and by the way...the stock IC piping in an s-13 with SMIC is around 9' long, and is 2" to 2.5 throughout. the only appreciable difference when going FMIC is core size.

[722ish]

Wow... perfectly clear... but the cars came with 9 ft of pipe as is... my car had that dumb top mount, must be the reason the whole thing "accelerates" its presence

[Just Dave]

722. I thought that was you. I'm not really getting mad about all of this, its just the internet, no big deal. Its all good.

But like Scott was able to show, the difference is neglibible. I don't know if its an issue with the drawthru MAF, but it doesn't seem like everyone is experiencing issues. On the turbo Fords, like Dave's, they don't even come with an intercooler from the factory. He's added an IC with no ill affects so I'm not sure what exactly was going on. :dunno:

[Just Dave]

Here's some more math in regards to IC piping. Lemme know when you've applied this logic to your piping and I'll find some more ;)

http://ta.twi.tudelft.nl/isnas/report94-24/node10.html

[722ish]

Originally posted by Force Fed 23
722. I thought that was you. I'm not really getting mad about all of this, its just the internet, no big deal. Its all good.


glad i remembered that... did you pick up that RFL?

as for my currrent situation, i ask to move the MAF simply because it might make easier use, in "blow through" setup... i realize the 2.3 turbos had no intercooler stock now thanks, but.... his piping is all of a few feet total... similar to my stock stuff... now ive got a lot more piping, as well as a HUGE ass core... i say huge just in comparison to the stupid ass stock top mount. its something along the lines of a 33x10x3.5 ... i cant remember the exact dimensions any longer, but this is relatively close ..


now, i read the page you posted, i think im grasping the idea.... a little notchy...

herein lies the problem.. not so much the piping diameter as the relative "distance" the MAF is from the throttle body... it seems like the additiion of the front mount, as well as all the piping as opposed to the factory 6 inches.. but i think im going to try a few things as far as that goes...

whatever else you have, lets see it ;) this is getting better yet :)