Little off the topic but what about from a 2" to 2.5" for small turbo like T25? I'm a newbie here and I'm planning to go FMIC with 2.5" for my T25. Is it overkill?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">Turncoat, i feel your frustration. lol

Listen to this guy, he knows what he's talking about!

Just cause your friend makes 700whp on 2" piping, doesn't mean it's optimal...</TD></TR></TABLE>

I think the reason a lot of people are hesistant to start a 3" IC piping bandwagon is because there has been no back to back comparisons done. It would be nice to see a 2"/2.25" vs 2.5" vs 3" IC piping setup to see what spool characteristics and power differences there are.

EDIT: also can either you or turncoat tell us if going with a 3" IC piping can effect the compressor surge threshold? I was thinking that with bigger piping you would be closer to the surge line or maybe even past the surge line when you are cruising around. This might not be a concern to track only cars but for people that DD their 500-600 HP cars it might be something to worry about.


Modified by BlueShadow at 6:34 AM 11/9/2005

 

Less pressure drop in your charge pipes (bigger) and intercooler will drop you down the compressor map, since at the same flow you will now be at a lower pressure ratio. So this will move you away (downwards) from the surge line.



At low flows/rpms, the pressure drop will be a lot lower, probably low even with 2" pipes. The benefits will really only be seen near the maximum air flow...high rpms and at full boost.

 

i'll be using 2.5 from turbo to intercooler ( i think, maybe 3) and 3" from ic to throttle body merely because i have a 75mm mustang tb

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">Less pressure drop in your charge pipes (bigger) and intercooler will drop you down the compressor map, since at the same flow you will now be at a lower pressure ratio. So this will move you away (downwards) from the surge line.

At low flows/rpms, the pressure drop will be a lot lower, probably low even with 2" pipes. The benefits will really only be seen near the maximum air flow...high rpms and at full boost.
</TD></TR></TABLE>

The reason I asked the question above was because I was afraid a 3" system might cause an imbalance in the system. For 15-20 PSI on something like an SC61 or GT35R we are talking about a flow rate of about 50-60 lb/min or about 650-800 cfm. I believe at those flow rates we are looking at roughly 475-625 HP. 650-800 cfm is still well within the limits if a 2.5" system. But of course that's based on my old calculations in the other IC pipe size thread, so take it with a grain of salt. And even though 3" is pretty good for the OP's psi/HP goal, but based on my calculations so is 2.5". But if this car/turbo setup is also gonna be doing a fair share of daily driving, I'd also be worried about low to mid range driveability. At low-mid range the 2.5" still does ok, and there are a lot of actual setups to prove that it is ok. However 3" IC setups are still pretty rare so not a lot of real world info on day to day driving is available. Like I said what it would take is probably a back to back comparison with some sort of proof from somebody reputable.

I never got the chance to more in depth on that thread. I may have mentioned it, but those numbers in the other thread weren't corrected for temperature. Since I posted that thread I've done a little bit of reading up on turbobygarrett.com about mass flow rates. I posted a long time ago on a how to read a compressor map the different temperature correction factors for converting cfm to lb/min. Maybe when I have some more free time i'll do that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by project dc2 &raquo;</TD></TR><TR><TD CLASS="quote">

i personally prefer

2 inch frolm turbo to intercooler
and 2.25 from intercooler to TB.

however people want 2.5 so i just serve what people want. </TD></TR></TABLE>

why do you prefer 2 inch from the turbo to intercooler? just curious to know because that is how i have my i/c pipes but we made it that size so they would fit with the traction bars..

 

Blueshadow...let's try it. See if how much pressure drop you have at max power in your setup. I'll walk everyone here through what I am doing, maybe some people have different arrangements of piping, or would rather try a combination of size to at least get a starting point to what to expect...

http://www.freecalc.com/gasfram.htm

If you can find turbocalc.xls (do a search, it's here somewhere) and understand enough to input your setup, it will tell you how much ACFM you are flowing. The "A" in ACFM is "Actual", as opposed to SCFM, or "Standard". ACFM is the actual volumetric flow at the pressure you are running (i.e. in your charge pipes), wheras SCFM is translated to standard temp and pressure, 70F and 0 psig (gauge, = 14.7 psia, "a"for absolute).

So, your 650-800 SCFM at 0 psig will be 350-400 ACFM at 15 psig. Use ACFM and input the following on the link above:

FLUID AND PIPING
None of these fields can be left blank, enter 0 if necessary
Nominal Pipe Size: 2.5
Pipe Schedule: Sanitary OD Tubing
Piping Material: DRAWN TUBING
Flow Rate: 350 ACFM
Viscosity (cP): 0.018
Temperature (F): 100F
Gas Molecular Weight: 29
Specific Heat Ratio: 1.4
Compressibility Factor: 1
Inlet Pressure (PSIG): 15
Piping Length (ft): 8
VALVES AND FITTINGS
Long Radius Elbows 6

I get 1.22 psig, which isn't all that bad. If you bump to 3" tubing, you drop to 0.53 psig, not worth the switch maybe, but if you were starting from scratch you may want to spend the extra here instead of a 4" downpipe...

But, if you go up to 25 psig and 400 ACFM, this turns into 2.14 psig for 2.5" pipes and 0.92 psig for 3" pipes. If you are approaching surge on your turbo, you might consider the switch...

Anyway, it would be neat if some people tried it with their own setups to see if it's worth looking at...

 

heres a read..... http://forums.evans-tuning.com...+size

 

I think alot of that is wrong. You will have less pressure drop with a bigger pipe. That's also a common misconception with intercoolers, that you have a big pressure drop with a big core, when in reality it's the other way. Too small of an intercooler will not flow enough, and cause the air at the inlet to back up, causing higher pressure at the inlet than at the outlet, hence "pressure drop".

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">I think alot of that is wrong. You will have less pressure drop with a bigger pipe. That's also a common misconception with intercoolers, that you have a big pressure drop with a big core, when in reality it's the other way. Too small of an intercooler will not flow enough, and cause the air at the inlet to back up, causing higher pressure at the inlet than at the outlet, hence "pressure drop".</TD></TR></TABLE>

Agreed. I was really horrified when I read that link about how the concept of pressure drop was so wrongly described by Jeff, esp considering some of the excellent other stuff I've read of his. No disrespect... but the equation for calculating it is Bernoulli - it's not that difficult. I usually use the on-line link I provided (it also uses bernoulli), even at work, except that you'll have to use some other method of calculating the pressure drop across a heat exchanger (intercooler). If people are really interested, I can work out bar-and-plate intercooler (core only - the endtanks would be a nightmare to calculate and probably wouldn't amount to much) pressure drops given certain parameters.

A little off-topic...but...
The only thing I might add, is that you (theoretically) can have too big an intercooler, but not because of no pressure drop - rather, it's because of a lack of turbulence. If the velocity across the tubes/bars/whatever is too slow, the flow becomes more laminar. In an intercooler, this means the air closest to the outside of the tubes/bars/chambers (and thus closer to the cold metal) will cool down more than the hotter air in the middle of the chambers, leading to poor heat transfer. With increased velocity comes increased turbulence, and thus better mixing within the tubes/bars, getting more of the hotter air closer to the colder matel where it will transfer more heat. Infinitely, if you use a heat exchanger so big that your velocity slows to a crawl, you will have basically no heat transfer and your intercooler will be useles. BUT...., with the internal fins in most intercoolers increasing turbulence greatly, I doubt that this "limit" of size would ever be realized.

 

I'm really interested as to what the Garrett engineer on honda tech (The Shodan..?) would have to say about the scenario we're talking about.

I'm assuming that we can drop 1 or 2 psi in a "big motor" setup by going to 3" or bigger charge piping, so at the same airflow, we would have a lower pressure ratio on the compressor map. So, how much benefit are we realizing in:

1.) the reduced temperature rise across the compressor, especially if the drop in pressure ratio drops you into a better efficiency range on the compressor map (and what if it drops you into a worse efficiency range..?)

2.) the reduced work the compressor has to do due to the drop in pressure ratio, an thus the less shaft hp the turbine has to make and thus ultimately...

3.) the reduced EM pressure, and thus less losses in the motor in trying to spin the turbine (although I realize a lot of work coming from the turbine is from heat as well, not all due to pressure)

Again, while I'm pretty sure my assumptions are right, I have only some idea as to how much some of it is worth in gains (without access to Garrett's files...!)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">Agreed. I was really horrified when I read that link about how the concept of pressure drop was so wrongly described by Jeff, esp considering some of the excellent other stuff I've read of his.</TD></TR></TABLE>

Please look at the date of the thread. I've learned A LOT since then. Also, I screwed up calculations in that thread, which threw off what I was trying to explain. I realized this not too long after posting it that it was wrong, and I never went back to change it (it was too long of a post!). Who knew people actually used the search button?

 

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

Who knew people actually used the search button?

</TD></TR></TABLE>


Cmon Jeff........you know nothing gets by...haha

 

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

Please look at the date of the thread. I've learned A LOT since then. Also, I screwed up calculations in that thread, which threw off what I was trying to explain. I realized this not too long after posting it that it was wrong, and I never went back to change it (it was too long of a post!). Who knew people actually used the search button?

</TD></TR></TABLE>

Like I said no disrespect meant...maybe I worded it a little strong. I've learned many things myself from a lot of people here, and I really like the engine buildup thread you're hosting on your site. I have a lot to learn about fuel and ignition tuning and turbo/turbines in general, at least to get to where I'd feel comfortable giving advice about it. But piping is something I know.

I included the link since it's pretty simple for anyone who learned pV =nRT in high school, and I always calculate my pressure drops at least to check. I find in some buildups, some pipes are way too small, whereas other pipes may be so big they're wayyy past the point of diminishing returns.

Maybe for fun, I can do some estimations on the pressure drop of the 4" downpipe (the most interesting "bandwagon"), just to see if it really makes sense in terms of gains. It's a bit trickier since there is a large temeprature gradient from the start to the finish of the pipe...

J

 

short question at the very bottom

I have a question in regards to the speed of air flow and the diameter of the piping ... at what point is the volumetric capacity of the piping such that the air doesn't need to be compressed to flow in it? Reason I ask is this, if the 3" piping will flow the amount of air that a T3/T4 GT28 GT30R etc without the air being compressed, then the compressed air coming out of the compressor outlet into the charge piping will decompress... unless the larger piping retains the compression of the air being pumped into it...

Also the idea was suggested that if there is less of a pressure loss in the charge piping then the pressure ratio would be allowed to be lower, and I agree with that. Problem is once the piping is charged and the air in it is compressed to the same PR that the turbocharger has (ie same PR across the turbo inlet/outlet vs same PR to ambiant air and the compression of the air in the pipe) does it make any difference? What I think you may be considering is either flow only in relation to the piping itself without anything on the other side of it. In this case there's a restrictive hole that will only allow so much air into it during the intake stroke. So at what point is the PR more a comparison of the air going into the intake of the compressor and the amount of compression of the air that is in the intake manifold, in the runners, and being shoved against the closed valve until it opens?

Taking that into consideration it may be necessary to use a slightly smaller diameter piping so as to ensure that there will no transient loses in the piping system before the air reaches the cylinder head.

Understandibly&lt;sp&gt;, all this may be completely useless if the 3" diameter piping must have the air compressed to be able to flow the amounts you guys are talking about.

short question How much air will a 2", 2.5", 3" pipe flow without any compression?