OK so i'm a little stuck on how I should do my inter-cooler piping. I am getting a large part of my turbo setup from FM and was thinking about their silicone IC piping. I have already sourced a IC (larger then FMs, its a Begi #3). I like their cold side a lot but I think I could make up the hot side myself to save $ and maybe go bigger then 2 as I may de power my steering rack as I have some piping and couplers. Now comes my issue, I don't want to sacrifice flow or efficiency for just saving $. If I am tight on space and or decide to not depower my rack + remove components then I would have to go with the 2in but it seems that most of the 2in aluminum couplers and piping are actually 1.8xx or whatever on the inside diameter so the silicone has a perfect 2in fit on the outside.

Does that .2xx or so have any real restriction on flow when using aluminum piping? How great of an effect do the bends and going from pipe-silicone (repeat however many time a connection is made) have on the flow and efficiency? I was always told that a system is only as good as its weakest link (which confuses me with regards to FM's 2.5in piping on one side and 2in on the other as wouldn't the 2in make the 2.5 a waste as the system was already restricted to 2in?) but i see different size piping throughout on different builds so does that ideal not really apply to IC piping because of pressure, cold vs hot side, ect?

Thank you!

 

Rule of thumb is don't decrement plumbing size between turbo outlet and TB inlet - ie. your bottleneck should be the size of the turbo outlet.
2" hotside is commonly used because the turbo outlet is 2" and it's easier to route the smaller-diameter pipes on the hotside.
Coldside must mate to the TB inlet which is typically 2.5" (or 2.75" foir Skunk2 TB) so 2.5" pipes are often used on coldside and there's a bit more space on that side to work with.

Try and minimise the length of plumbing and the angles needed.

 

what turbo are you using

Edit: just recalled you where going to use a GT2860R which runs about 37lb/min max (if reading the compressor map correctly)

That means 37(lbs/min)/.074= ~500CFM

Taken from another forum:
You should be fine with 2" piping, then just taper up gradually before the throttle body


With the EFR6758 (max flow 53 lb/min),I'm planning on running 2.25 piping for my intercooler setup. a gradual 2.0-2.25 taper from the compressor housing and a 2.25-2.5 to the throttle body. Keep in mind, more bends adds more flow losses so keep it as simple as possible. When we met, that's why I was trying to reduce the entire system to just two 90° bends with an over the radiator setup.

Switching to a fatter intercooler and larger piping reduced response noticeably. I think my car was quicker with the Begi, but the vibrant is temporary.

 

Yep, more bends adds losses, and 45º elbows are better than 90º elbows, hydraulically (if you need to zigzag around an obstruction).

 

did you get that from my thread? cause we discussed this in great detail in my ic piping thread and OP needs to learn how to search

the above numbers don't really account for bends and ic like huesmann said, but 2" should still be plenty for most setups

 

I was just referencing a DSM forum.

Also to back up the over the top setup, the FM piping has two 90° bends on the cold side alone angling up behind the radiator then into the throttle. The aim was to shorten the pipe length as much as possible and maintain a diameter for the laminar flow with enough headroom to account for some flow loss.

 

Yeah, I think that's where we got those numbers too.
TBH I didn't feel any difference at all between short over the rad 2.5 piping vs longer behind the headlight 2.5 piping vs "traditional" fm/begi 2 piping
each has it's ups and downs but neither looked like a clear winner to me

 

I'm in agreement. The intercooler itself played a bigger roll in spool difference for me switching from Begi#3 to Vibrant big. All piping remaining the same; mine is routed through the fender on the hot side, then the standard FM way on the cold side. NA is tight. I can't throw it in front of the AC compressor, and don't have much space for the filter. Looking forward to regaining real estate behind the fog vents.

 

I wanna start by saying I'm sorry it took so long to get back as I'm starting to realize how hard it is to balance school and work all while trying to build this turbo miata but I'm making it work lol. Ok, so I ended up finally ordering a large portion of the FM2 kit yesterday with the parts I wanted - the ones I wanted to and did source elsewhere (i.e your IC ). I decided to not go with the FM piping for $ saving purposes (its about to be an 8g winter project including turbo kit, exhaust, clutch + flywheel, rad+coolant RR and other supporting mods as well as maintenance parts to freshen things up while I'm in there) but I was able to save on piping thanks to you for that box of goodies and pipes you included with the IC so thank you very much for that. I did a very rough out of the car mock up with the pipes and couplers you provided and I should only need minimal additional pieces to get it on the car.

Ok now on to the piping size. I too believe that starting with 2in should be fine then going to 2.25 for the ic and then to 2.25 from the ic to 2.5 for TB. I have read and seen tables like the one you referenced on forms before but while reading forms with those tables other posters warned readers that those numbers are or may be for straight piping only and does not account for bends in the piping ect. After thinking hard and reading what you and others have had to say on this post I believe that especially for my current set up until I build motor and upgrade the turbo once I get some more $ down the road (2-3 years estimate) going with 2in on the hot side with a few but minimal bends in my piping will be fine. I may not be able to match the flow of the smooth one piece FM silicone but their are so many people who run a DIY piping setup that I'm sure ill be fine without bumping myself out of my desired power range or suffering response.

Now the one thing that still kinda bothers me is the fact that metal 2in IC piping is 2in outside diameter and like 1.8x diameter in the inside. Am I overthinking this or is that .1x of an inch going to affect flow that much from a full 2in inside diameter pipe (idk if it even exists) or 2in inside diameter silicone pipe? Everyone is probably going to read this and be astonished that anyone can be this particular but I'm kind of a neat freak and really pay attention to detail (2 years at the Military Academy certainty didn't help with this lol) and I just want to do it right the first time without second guessing my DIY piping job.

Thanks for your help,
Josh

 

You are over thinking this. 2" IC pipes will flow more air then a stock motor can handle with zero issues.

 

Dont forget, hot air/gas flows faster and easier. Again just to be repetitive, the bends will be the biggest concern in restriction.

 

2 bends , intercooler from a audi $35.00

 

That intercooler looks about as big as the token MSM intercooler (ie. not large enough)