hey guys im doing a custom turbo kit to my car..im wondering wats a good size piping to use???would 2.5 poiping be good???/

 

I'd say min 2.5"... 3" is more desireable.

 

Charge piping = 2.5
exhaust= full 3 inch if you can, if not 2.5 downpipe into a 3 inch exhaust

 

just no bigger than your throttle body for charge pipes...........

 

just a fyi......the calculations on flow rates of different size intercooler piping is actually a sticky or in the FAQ section.

Read up first newbies!!

 

you should match the size of your intercooler piping to the outlet size of your turbo outlet diameter. Some engineers spent some serious time designing the turbo... if they put a 2 inch diameter then a 2 inch pipe will flow enough to accomidate the turbo. and not to mention you will slow down the velocity of the charged air if you expand the pipe from a 2 inch outlet to a 2.5inch pipe. so match the turbo outlet and you will be good.

This charge pipe is matched to the turbo outlet flange and then expanded to match the iintercooler size which isnt much bigger... this would be the best way to do it

 

I run 2.5"

 

yeah i've seen ppl make some really good power
on ghetto rigged 14b/hf mani setups,
using super skinny ic piping..

In my mind, as long as it's the diameter of the turbo outlet, going to the intercooler ur fine.

after the intercooler you can run it thicker however.

 

from what i have found searching for the right intercooler piping many people and post say that the intercooler piping should be no bigger than the throttle bodie. but just throwing that out there but many people have been successful of bigger intercooler pipes and smaller.

 

Slightly larger than the turbo compressor outlet would be ideal. This will compensate for flow restrictions from bends and still be within the diameter which the turbo was meant to work with.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">Slightly larger than the turbo compressor outlet would be ideal. This will compensate for flow restrictions from bends and still be within the diameter which the turbo was meant to work with.</TD></TR></TABLE>

I defantly agree... i guess the only message i am trying to get across is that if you have a turbo with a one and a half inch outlet... then dont use 3 inch intercooler pipe.....
Dont jump on the band wagon that says bigger intercooler piping is better.....

Unless you have a monster turbo I would use 2 inch hot side of the IC piping and then go to 2.5 inch on the side after the intercooler...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Electron_LS-Vtec &raquo;</TD></TR><TR><TD CLASS="quote">

I defantly agree... i guess the only message i am trying to get across is that if you have a turbo with a one and a half inch outlet... then dont use 3 inch intercooler pipe.....
Dont jump on the band wagon that says bigger intercooler piping is better.....
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Any particular reasons...? Just curious why you say that. We already went through a thread on IC piping size and pressure drop, but nobody seemed to comment much when I started calculating the pressure drops and fill times when comparing 2, 2.5 and 3" piping.

https://honda-tech.com/zerothread?id=1424673

It seems to me that if your goals are to flow 400+hp worth of air through small diameter IC pipe, you can lose a couple psig between the intercooler and the throttle body, when compared to 3". If you can drop downwards on your compressor map (away from the surge line) by increasing IC size, your turbo will work a little less hard, be a little less hot, and lower your EM pressure that much more. This is all good.

The diference in pressure drop is real, so I will have to assume the gains are real. And the difference in spool time seems really minimal. I already did some (relatively) simple math. I was hoping someone with more knowledge on the subject could chime in, especially with some ideas about the benefits of dropping downwards on your compressor map at the same flow.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">

Any particular reasons...? Just curious why you say that. We already went through a thread on IC piping size and pressure drop, but nobody seemed to comment much when I started calculating the pressure drops and fill times when comparing 2, 2.5 and 3" piping.

https://honda-tech.com/zerothread?id=1424673

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The tech you posted in the above link was very useful... I am always wondering how much of a lag difference there would be to up size the IC pipes to 3" though, but I couldn't find an exact answer. Peak power-wise, your posts confirmed that larger IC pipes would definitely be the way to go.

Now I do understand that lag time would be negligable when the turbo is running at full tilt and WOT after reading your posts. How about everyday driving and building partial boost? I used to run steel 2.25" charge pipes from the IC to the TB, but then I switched over to 2.5" (mainly because I had 2.5" aluminum pipes sitting around and wanted to switch over). I noticed it took the turbo a lot more effort to build the initial 1-5 psi, and also the car felt more sluggish in the DD zones. Between gear changes, it also took the turbo more time to rebuild the boost; such as revving to 5000RPM and granny shifting like what you would do during regular driving.

I would say that IC charge pipe sizes wouldn't increase too much lag during high air pressures and velocity, but at low RPM's, low boost and during daily driving, it takes a greater hit with lag.

 

I figure the difference in going up to the next 1/2" in the typical IC pipe setup is about 0.1 cubic foot extra.

So as a simple example, at 120 CFM (approaching 4000 rpm), the time to fill the extra 0.1 cubic feet to 15 psig is 0.05 sec extra than with the smaller diameter pipe. Not much.


p.s. I know I could calculate this properly, for different boost levels and airflows and volumes, but just wanted people to understand, I don't want to scare people with "ln(x)*..." etc...

 

2.5" is probably the best up to about 800hp. I've tested 2" 2.5" and 3" intercooler piping on my 350bhp mazda. All 3 of them were within 12 horsepower with only a difference of 2hp on the 2.5 to 3".

For the exhaust 3" is a waste of time. 2.5" has no problems supporting 600hp. Look at how much room there is when an exhaust valve is 1/4 of the way closed. How will that cause flow issues in a 3" pipe? You're literally blowing a garden hose into a sewer pipe.

I tested a turbo H22 with a stock, 2.5" and then 3" exhaust. Stock -&gt; 2.5" was 25whp gained. 2.5" to 3" was 4whp and removing the cat was an additional 2whp. Barely noticeable with a 380whp car.

-Michael

 

Are you kidding?

 

2.5"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">p.s. I know I could calculate this properly, for different boost levels and airflows and volumes, but just wanted people to understand, I don't want to scare people with "ln(x)*..." etc...</TD></TR></TABLE>

Oh, no!!! Not the natural log!!

&lt;----runs away screaming

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hackish &raquo;</TD></TR><TR><TD CLASS="quote">2.5" is probably the best up to about 800hp. I've tested 2" 2.5" and 3" intercooler piping on my 350bhp mazda. All 3 of them were within 12 horsepower with only a difference of 2hp on the 2.5 to 3".

For the exhaust 3" is a waste of time. 2.5" has no problems supporting 600hp. Look at how much room there is when an exhaust valve is 1/4 of the way closed. How will that cause flow issues in a 3" pipe? You're literally blowing a garden hose into a sewer pipe.

I tested a turbo H22 with a stock, 2.5" and then 3" exhaust. Stock -&gt; 2.5" was 25whp gained. 2.5" to 3" was 4whp and removing the cat was an additional 2whp. Barely noticeable with a 380whp car.

-Michael

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Umm, kinda curious about this. According to the ic piping sizing post (where I will assume that BlueShadow has his math done correctly, he seems to b on the ball), the max cfm for 2.5" ic piping is 913cfm. This =~64lb/min. Now that means that with NO restriction on the end of the ic pipes ~64lb/min is the max flow for the piping. So how will an engine push 800hp (~75lb/min to 85lb/min according to the generic analogy of 1lb/min = 10hp, not completely accurate, but ballpark) with 2.5" id ic piping bottlenecking it??? Just curious.

Also, the exhaust.......it seems that the exhuast on turbo cars aren't changed merely to accept the extra exhaust gas flow from the engine using more air, but also to create less back pressure for the turbine and thus place it more in it's efficiency. Right? So you may not see a direct hp correlation for increased exhuast size, but you will have more efficient hp (same hp with less boost, because the turbine is being more efficient) and slightly better spool. ?

Just some thoughts, prolly dumb ones.

 

On the H22 comparison the boost was run at the same level. Stock versus 2.5" the boost came on a little quicker but there was realistically no differene between the 2.5" and the 3". Maybe the car is quicker in the 1/4 because the owner's pockets were lighter from buying the 3". For the intercooler piping I did see a car make 800bhp on an engine dyno through some 2.5" pipe and a simiar sized throttle body. The rest of my stuff comes from experience.

-Michael

 

Let me ask you this, because you saw 800hp on 2.5" piping, does that make it optimal?

It sounds like your test data was on a 350hp car, and the amount of airflow difference between 350hp and 800hp is quite large.

On the exhaust, it's been proven time and time again that bigger is better to a point of dimishing returns on a turbo engine. It's possible that the a/r and turbine wheel was very undersized on the application you tested, and that's why the differences didn't seem worth the time.

 

i'll be running 2.5 from turbo to intercooler and 3" from ic to throttle body (75mm mustang tb) 500whp on pump no nitrous, around 800 on c16 and n2o

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">I figure the difference in going up to the next 1/2" in the typical IC pipe setup is about 0.1 cubic foot extra.

So as a simple example, at 120 CFM (approaching 4000 rpm), the time to fill the extra 0.1 cubic feet to 15 psig is 0.05 sec extra than with the smaller diameter pipe. Not much.


p.s. I know I could calculate this properly, for different boost levels and airflows and volumes, but just wanted people to understand, I don't want to scare people with "ln(x)*..." etc...</TD></TR></TABLE>

I guess engines in general are very sensitve to pressure changes and air velocity... I used to do a lot of reading on all motor setups, and just by changing the intake pipe diameter, or too large of a TB, etc.. would kill air velocity and completely change the VE of the engine at certain RPM's. From you calculations, it is completely legit, but there must be something involved which resulted in the lag difference I have felt from upsizing the charge piping. The larger pipe must have slowed down the air velocity to the extent that at lower RPM's, the engine felt noticeable laggier. As VE decreases, the turbo requires more time to build the initial 1-4 psi of boost and therefore, weakens the daily driving RPM zones. I mean afterall, boosted motors are like NA motors, it is what gets in the engine which produces power; although the pipes could be pressurized in fraction of a second, but somehow it's not entering the engine as efficient as smaller pipes which promotes much faster air velocity.

I currently have 2.5" charge piping on my other car which is a turbocharged Camry V6. I am planning on switching over to aluminum piping anyways, so I might consider upsizing to 3" and feel the difference. It has a high stall auto trans so low RPM driving zones is not a concern at all. I should be able to get some results with nothing else changed except for charge piping, but of course, I won't be able to do both runs on the same day. Still something good to test out IMO

 

on a stock b16 with a drag3 turbo kit, we picked up 75hp going from a stock exh to a 3 inch. picked up 25hp going from 2.5 to 3 inch on a drag kit on a prelude. not to mention the turbo spooled MUCH quicker.

on a 600hp car we picked up about 20hp and 35 ft/lbs going from a 3 inch dp to a 5 inch dp.

2.5 charge pipe is good to probably 600hp, at 700hp just changing the cold side from 2.5 to 3 inch resulted in the same power, but at 4psi less boost.

 

hes talkin about 600-800hp motors and look at the turbo he has in his avatar....odd isn't it?