Intercooler Piping

[nizmonut]

your piping only need be the same size as the smallest restriction after the turbo charger....ie why go 3 inch when your throttle body is 2.75....it ain't gonna fit thru there any faster by using 3 inch..... not only that the hotter the air the more it expands so in theory you would want to compress it a little the cooler it got....in theory

so say 3 inch from turbo to cooler means one reducer off the turbo.. then go from 2.75 off the cool side of the intercooler to the throttle body , so two reducers one on the turbo and one after the intercooler will keep the air flowing at its optimum rate given what you have descibed....sorry. i studied all this bs for a science exam...never thought id need it.

may i add you may have trouble gettin the 3 inch pipe up, overbetween the radiator fan and the cam cover....having to trim the fan blades a little.

Edited May 20, 2008 by nizmonut

[GeeTR]

your piping only need be the same size as the smallest restriction after the turbo charger....ie why go 3 inch when your throttle body is 2.75....it ain't gonna fit thru there any faster by using 3 inch..... not only that the hotter the air the more it expands so in theory you would want to compress it a little the cooler it got....in theory

so say 3 inch from turbo to cooler means one reducer off the turbo.. then go from 2.75 off the cool side of the intercooler to the throttle body , so two reducers one on the turbo and one after the intercooler will keep the air flowing at its optimum rate given what you have descibed....sorry. i studied all this bs for a science exam...never thought id need it.

I'll assume your addressing your post to me

I didn't mean to flare the post IC pipe to larger then TB size just for viscosity's sake...

Most TB's are larger then the comp cover outlet, as are most IC inlet / outlet. This is why most ppl fit smaller pipework from turbo -> IC inlet (with a flare) and then use larger pipework from IC outlet -> TB.

Again, I'm not suggesting using bigger pipes then your TB. My above thoughts are simply trying to legitimize the already "normal practice" of having IC -> TB pipes, the same width as the TB, and the turbo -> IC pipe, the same width as the turbo outlet OD (which as mentioned, is invariably a smaller OD then the TB)

...may i add you may have trouble gettin the 3 inch pipe up, overbetween the radiator fan and the cam cover....having to trim the fan blades a little.

You may, but just like a few other ppl posting in this thread, I've a GTR with stock ~3.25 inch piping.

Edited May 20, 2008 by GeeTR

[nizmonut]

I'll assume your addressing your post to me

I didn't mean to flare the post IC pipe to larger then TB size just for viscosity's sake. Most TB's are larger then the comp cover outlet, as are most IC inlet / outlet. This is why most ppl fit smaller pipework from turbo -> IC inlet (with a flare) and then use larger pipework from IC outlet -> TB.

Again, I'm not suggesting using bigger pipes then your TB. My above thoughts are simply trying to legitimize the already "normal practice" of having IC -> TB pipes, the same width as the TB, and the turbo -> IC pipe, the same width as the turbo outlet OD (which as mentioned, is invariably a smaller OD then the TB)

You may, as just like a few other ppl posting in this thread, I've a GTR with stock ~3.25 inch piping.

just to clarify as it is late here and i have been working on my gtr powered gts4 most of the day.....

aforementioned post was for turboedsloth, it was he that asked for idea's parameter's to best suit his rb20det not his dream car powered by a rb26dett.

stating the obvious. yes i would hope all tb's are larger than comp cover outlet.....i'm sure i said .....

"smallest restriction AFTER the turbo charger"

when i said ''reducer from the turbo to the IC'", common sense would dictate one turn's it around to create a flare.

however when i said "hot side of the intercooler" common sense would apply again...to reduce his 3 inch intercooler outlet down to the tb's 2.75 inch diameter.

....viscosity is fluid.....velocity is speed....

Edited May 20, 2008 by nizmonut

[drgnball34]

im ready to order my ARE type 71 cooler. I just need to know what size in/out pipes to get. I have to4z which is 2.5 inch i belive and Q45 TB which is 90mm. So im assuming inlet is 2.5 and outlet is 3.5 or maybe even 3.75?? Please help

[Kinks]

There is no point going to a larger diameter than your widest point otherwise (ie, throttle body). All you do with big piping is increase the volume (and hence mass) of air in the pipe. What happens when you suddenly crack the the throttle wide open? All that air has to go from stopped, to moving. The more air you have the more it weighs and the longer it takes to get moving.

I would say maintain turbo outlet diameter to IC, and maybe go up to TB size after the IC.. either that or do your diameter switch just before the crossover pipe. The limiting factor is going to be how much air you can get through the turbo's compressor elbow and whether your intercooler is restrictive.. not the piping itself.

[drgnball34]

ok so 90mm TB works out to be 3.6 inch. So either i go 3.5 or 3.75? Im incline to go with 3.5... .25 wont make a difference?

[psi]

Caution.. this may require some thinking!

there is not a real 'correct' size! Like everything, its a compromise. I have a formula somewhere in my books about pipe size.

It is all based about airflow though the engine. then u add factors like psi drop across cooler and turbo effeceintcy.

ehh? you say..

ok, the bigger pipes will flow more air, small pipes will make boost faster(less pipe size to fill), medium pipes try and make the best of both, some run big sizes to the intercooler and the same size as the throttle as a return..

Then I read an aircon journal about pipe flow restrictions and bends. it said that a manderal bend of a small constant radius (like most cooler pipe bends) has about the same flow restriction as 6m of straight pipe.. hmm. so now we know bends are evil, but needed.

Then there is the argument about less dense hot air needing more space, and the argument about denser cooled air flows slower so it is good to have a big pipe to aid the 'thicker' air..

Then you have air speed, small turbo's pump lots of air down low and dont require a large pipe, but require a bigger pipe higher in the revs due to the massive compressor speed needed to make enough boost to feed the engine due to its small size.,

because of the speed of air needed, carefull consideration is paramount.

then big turbos change it all again.. the big pipes will help make big HP, but have a spongy throttle coming onto boost. the compressor spins heaps slower, and pumps air best above 10ish PSI boost. too small a pipe will choke the poor thing!

Now that i have opened a huge can of worms.. i'm goin to leave u!

In a couple of days, I will try and find my books! i will summerise it and post it up!

[GeeTR]

In a couple of days, I will try and find my books! i will summerise it and post it up!

If you could!!! Iv done my crash course in fluid dynamics, but still believe without quantitative testing, its all gibberish and "what my best mates GF's baby sister did'ed full seek" Im still waiting for some bored mech eng student to produce some FAE models. This crap see,s like its up GTRGeoff's ally actually

Edited May 26, 2008 by GeeTR

[toddlls]

Get on the phone to the guys at ARC and have a chat, they may have some good info for what you need

[juggernaut1]

Maybe give Richard at A.R.E. a call..........after all he built the intercoolers setups for the top 3 hp cars at Summernats 2008.

He also supplied me with a 530 hp rated intercooler with 2.5 inch inlet and outlet end tanks with associated 2.5 inch piping. Interestingly, these pipe sizes are also in line with Buschar Racing's optimum pipe sizes in their back to back dyno testing on an EVO with around 600 hp.

[GTRgeoff]

Just adding some info as I was asked to. This is more than a fluid flow problem as it involves some thermodynamics as well.

Ignore the effects of hot piping as the air flow is so fast that it has almost no time for heat to exchange.

As the air exits the compressor housing it also usually runs into a larger pipe. This has good implications as the air when it expands gets cooler, just like refrigeration uses a capillary tube into an expansion pipe to create the cooling effect in a fridge. Also when the air enters the larger pipe it increases static pressure head with a drop in velocity, so pressure increases a small amount. Simply put P1xV1=P2xV2

So the effect of the air expanding both increases the pressure/density and reduces temperature with increase in density.

The same again happens through the intercooler which also pulls more heat out of the air making it more dense again.

So we have an air charge that has expanded a couple of times and had a cooling process or 2 thrown in, hopefully with minimal pressure drop across the intercooler (efficiency of design) with maximum cooling.

So, does the size of the piping need to be larger/smaller exiting the intercooler? What size is about right? Every bend in the piping attracts a pressure drop due to restriction depending on the sharpness of the angle. Also every inch of straight piping exhibits a phenomena called turbulent wall growth which means the pipe appears to become smaller along its length. Even with the increased density the smaller volume of the charge means the entry and exit should be about the same without causing pressure drop due to increased viscosity.

About 3 inches (75mm) is considered a good size up to 800hp. The standard radiuses for 3" piping are of a gentle enough radius that they have minimal effect for the diameter of the pipe and the diameter itself can deliver sufficient flow even with losses due to length.

Space is a problem if you continue to use the over engine routing so 2.5" (60mm) will do if your power expectation is not massive...say below 500hp or about 300rwkw for a system without too many bends.

[Sydneykid]

Geoff covered it pretty well, I would add that I saw a Honda drag car make 750 bhp using 2" intercooler pipework last year when I was in the US. It had a long run with an ice box in the passenger footwell, so they kept the pipe volume down as much possible without affecting the power output.

Cheers

Gary

[psi]

yep. Geoff got it right.

He said what I was tring to say(he is a massive bunch smarter with this). It just goes to show that with some strong understanding of what happens, well it does wonders... My book has a whole page of numbers and fomula's to get to a base point which needs to then be understood.. The problem is that you cannot get all the correct info to produce the 'most' correct answer. Because the engine revs across such a wide range, the perfect size pipe is at best a bad compromise.

and because a car ran XXX hp with a set-up doesn't mean it cant be better, or be chocking, or be right on the money.

thanks Geoff!

[GeeTR]

Fantastic!! thanks Geoff

[GTRgeoff]

Pleased to be of assistance. I'm off back to a nerve damage, based drug coma guys.

[psi]

Aaargghh, I cant find my book,. Its on old pump book from 1950ish by a german author. it covers fluids, solids and air.

anyhow, I did find some scribbles that I made, they were in my 'Maxium boost' book,and He makes reference to cooler pipes, but its only a quick skim over it. He doesn't make much hooharr about it.. perhaps there is a point to that! Perhaps it just isn't that critical like i thought..

The german dude was saying that the difference between a 2.5" and 3" pipe made minimal gain unless all components flowed well with a very low pressure drop. Bends, cooler and throttle! The scribles that i got on my paper make reference to a 2" pipe good for 550ish cranck HP and 3" good for 900ish. both with very little prssure drop.

Which is exactly what Geoff said! On ya mate!

[Raysboostin]

So, does the size of the piping need to be larger/smaller exiting the intercooler? What size is about right? Every bend in the piping attracts a pressure drop due to restriction depending on the sharpness of the angle. Also every inch of straight piping exhibits a phenomena called turbulent wall growth which means the pipe appears to become smaller along its length. Even with the increased density the smaller volume of the charge means the entry and exit should be about the same without causing pressure drop due to increased viscosity.

wow this is alot more technical than i thought. let me just make sure my retarded mind got around this ok. so the increase in pipe diameter is to counteract the overall length of the pipe, number and severity of the bends??

the only question i have, which is the point ive been curious on since the start of this thread. does the larger pipe diameter have a noticeable affect on throttle response?? im not thinking of 800hp race motors, rather the basic upgrades streeter as most ppl would have. pretty much the sort of setup that inspired turboedsloth to start the thread.

PS nice write up there GTRgeoff. its a little technical to noobs like me but definelty cleared up things