Jump to content
HybridZ
Dat73z

Varying Intercooler Piping Size

Recommended Posts

Hello, 

 

Are there any benefits (or drawbacks) to varying intercooler piping size between the hot side and cold side? 

 

I am considering running 2.25" from the turbo (T3/TO4E 50 trim 2" outlet) to intercooler (2.5" inlet/outlet) and 2.5" from intercooler to intake manifold (2.5" inlet). 

 

This is for packaging reasons to give more clearance for electric fans. Does it make more sense to just go 2.5" for all piping instead? Any thoughts on boost response for the 2.25 versus 2.5 (or hybrid 2.25/2.5) or is this negligible? 

 

I'm shooting for ~300whp L-series so I don't think the setup would be choked but in the future may consider going for more power. 

 

Thank you! 

Share this post


Link to post
Share on other sites

In theory you want the post IC piping to be smaller and obviously, the pre intercooler piping would be larger.  The air from the turbo to the intercooler will be less dense as it is significantly hotter and thereby requires more volume due to the decreased density.  Once the charge goes through the intercooler it is cooler and therefore more dense requiring less piping size for a given mass of air.  On the GTR we see the turbo to intercooler piping is 2.75" and intercooler to TB piping is mostly 2.50".  With that said, I run 2.75" on my GTR for all piping, largely because I run a blow through MAF setup and I needed the larger piping on the post IC due to flow limitations.

 

You don't want to go too big or you lose velocity in the pipe, which decreases throttle response and turbo response.  If we assume you will want to support [email protected] then you need to flow ~600cfm.  If you look at Corky Bell's book Maximum Boost, he says to keep charge velocity below 450fps to avoid excessive drag.  A 2.5" pipe flowing 600cfm has a charge velocity of 293fps so well below the limit.  A 2.25" pipe has a charge velocity of 362fps and 2.00" pipe has a charge velocity of 458fps.

 

I would personally probably run 2.25" or 2.50" the whole way or you can mix and match based on the above density theory.  Beyond 2.50" serves no purpose.

Edited by 240Z Turbo

Share this post


Link to post
Share on other sites

I just researched this for pretty much the last 5 days because I was also wondering about piping size with the goal of having low levels of turbo lag, easy routing, and horsepower. I also have a long-term goal of ~300hp.

 

The consensus is that for that level of horsepower (and even slightly more) then 2.25" piping is more than sufficient. I ended up getting this pre-fabbed welded kit from Simtec here so that I didn't have to worry about piping lengths/bends/routing: http://simtecmotorsports.com/product/front-mount-intercooler-kit/

 

On that note, do you have any pics of your electric fan setup with intercooler piping? I need to add an electric fan to mine and am curious as to how it will fit with piping in there.

Share this post


Link to post
Share on other sites

Just be careful as the holes in the front radiator support where you run the IC piping vary from year to year.  Specifically, their location slightly changes depending on the year of your car.  I learned this the hard way when I used to fabricate intercoolers for the Z.

Share this post


Link to post
Share on other sites

240z Turbo- interesting points on charge air density and piping diameters. I had not considered that. If at all possible I'd like to go 2.5" and be done with it but I'm thinking packaging will be the issue. Do you think the 2.25" piping on the hot side would make a noticeable difference in boost/turbo response at these power levels ~300whp? 

 

Albatross Cafe- I have yet to mount my electric fans. I have been running a Mishimoto radiator with the mechanical fan/clutch for years which has been working great in my weather and recently picked up the ZCarDepot 12" dual fan shroud. I have yet to purchase my electric fans but I'm looking at running the following SPAL models: 

 

Spal 30101522 Puller Fan (12" Medium Profile) ~1300 CFM ~2.5" thick

Spal 30100467 Puller Fan (12" Low Profile) ~ 900CFM ~2" thick

 

So far as I can tell I'll need the twin 12" medium profile fans for >2000 CFM to match the factory mechanical fan (or a combination of one medium, 1 low profile). Really the main constraint for me will be running the hot side pipe across the front of the engine with the fan shroud and electric fans. I could probably just mount the fans directly to the radiator and save an inch or so that way but would prefer to run the shroud as it gets over 100*F over here on summer days. Also I've been in contact with Craig @ Simtec (really nice and knowledgeable guy). He'll be fabricating the piping for me but I'll need to get him the measurements of my setup once I have it all mocked up. 

Share this post


Link to post
Share on other sites
2 hours ago, Dat73z said:

Albatross Cafe- I have yet to mount my electric fans. I have been running a Mishimoto radiator with the mechanical fan/clutch for years which has been working great in my weather and recently picked up the ZCarDepot 12" dual fan shroud. I have yet to purchase my electric fans but I'm looking at running the following SPAL models: 

 

Spal 30101522 Puller Fan (12" Medium Profile) ~1300 CFM ~2.5" thick

Spal 30100467 Puller Fan (12" Low Profile) ~ 900CFM ~2" thick

 

So far as I can tell I'll need the twin 12" medium profile fans for >2000 CFM to match the factory mechanical fan (or a combination of one medium, 1 low profile). Really the main constraint for me will be running the hot side pipe across the front of the engine with the fan shroud and electric fans. I could probably just mount the fans directly to the radiator and save an inch or so that way but would prefer to run the shroud as it gets over 100*F over here on summer days. Also I've been in contact with Craig @ Simtec (really nice and knowledgeable guy). He'll be fabricating the piping for me but I'll need to get him the measurements of my setup once I have it all mocked up. 

 

Haha cool, seems like we are in the exact same predicament... I was looking at that same ZCarDepot shroud and SPAL models as well. I hesitate to run without a shroud after everything I've read. Seems like even the nicest/best fans don't operate well without one. Too bad you aren't a little further along in your process, I'd like to see how everything fits before I take the $300 plunge on fans/shroud combo.

Edited by AlbatrossCafe

Share this post


Link to post
Share on other sites
15 minutes ago, AlbatrossCafe said:

 

Haha cool, seems like we are in the exact same predicament... I was looking at that same ZCarDepot shroud and SPAL models as well. I hesitate to run without a shroud after everything I've read. Seems like even the nicest/best fans don't operate well without one. Too bad you aren't a little further along in your process, I'd like to see how everything fits before I take the $300 plunge on fans/shroud combo.

 

Another way to look at this is you need fans either way and you already have the intercooler piping kit. You could always get a larger single or the dual 12's and decide after mocking and measuring up if you want to fabricate or purchase a shroud. Best of luck on your install. 

 

Edit: Just purchased the 2x Spal 30101522 Puller Fan (12" Medium Profile) ~1300 CFM ~2.5" thick so I guess I'll know in a week or so. 

Edited by Dat73z

Share this post


Link to post
Share on other sites
5 hours ago, Dat73z said:

240z Turbo- interesting points on charge air density and piping diameters. I had not considered that. If at all possible I'd like to go 2.5" and be done with it but I'm thinking packaging will be the issue. Do you think the 2.25" piping on the hot side would make a noticeable difference in boost/turbo response at these power levels ~300whp?

 

I think you will be fine either way, but if packaging is an issue you at least have piece of mind that 2.25" will support the necessary flow without excessive drag based on the guidelines provided by Corky Bell. 

Share this post


Link to post
Share on other sites

For the curious, here is what twin SPAL 30101522 12" fans look like on a ZCarDepot shroud. The fans are slightly over 1" thick at the edges and taper to slightly over 2" thick at the motor. This matches the drawings from the SPAL website of course. The shroud is a bit undersized for these particular fans and feature a step at the edges. I'm not sure of the functional purpose of the step, but it adds roughly 3/4" to the assembly height or as I'd mentioned before ~1" if I consider the 1/4" step inwards on the Mishimoto radiator. Likely I'll fabricate my own flat AL shroud to better fit the radiator and fans. 

20180913_130514.jpg

20180913_130615.jpg

Share this post


Link to post
Share on other sites

If you don't have a step you will completely stop all flow through the radiator other than the circular areas where the fans are. You need some amount of space behind the radiator for there to be airflow. 

Share this post


Link to post
Share on other sites

Thanks, yeah realized that yesterday as well when researching if there was an optimal air gap between the fans and cooling fins for a shroud. I was looking around and it looks like most aftermarket radiators have the cooling fins coming out to almost flush with the endtanks. The Mishimoto which is what I've been running has the cooling fins ~1/4" inset behind the endtanks I think because it's a 2 core so may be able to net another 3/4" clearance there. Going to measure and see this weekend/week or next when I get everything on. 

 

Found this pic of a Mishimoto radiator from their site where they welded on a shroud for the s30z radiator. 

MMSHOW-38_10.png

Share this post


Link to post
Share on other sites
21 hours ago, Dat73z said:

For the curious, here is what twin SPAL 30101522 12" fans look like on a ZCarDepot shroud. The fans are slightly over 1" thick at the edges and taper to slightly over 2" thick at the motor. This matches the drawings from the SPAL website of course. The shroud is a bit undersized for these particular fans and feature a step at the edges. I'm not sure of the functional purpose of the step, but it adds roughly 3/4" to the assembly height or as I'd mentioned before ~1" if I consider the 1/4" step inwards on the Mishimoto radiator. Likely I'll fabricate my own flat AL shroud to better fit the radiator and fans. 

 

 

 

Awesome, thanks for this. This prevented me from dumping my money on it. The shroud seems awkwardly small for 12" fans. I bet I can buy some aluminum sheeting and hack something up that works just fine.

Share this post


Link to post
Share on other sites

No problem- to be clear, this shroud looks like to would work great with slightly smaller diameter fans and on those 3 core radiators where the cooling fins are flush with the endtanks to direct all of the cooling air into the fans. If you want to run the twin 12 spals it would be better to fab your own shroud. I'm talking to some folks now to get this cut on a waterjet to hopefully get a better finish than I can with tin snips. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×