Billj747

If you have good (virtually air-tight) ducting, then fans don't really do a whole lot at speeds above 40-50mph, where the airflow from the car moving will flow far more air than any fan. Most setups have massive gaps between the heat exchangers, front bumper, and framerails, so fans absolutely will help in most cases. Check out GC Cooling (they use to make the motors for SPAL and they're essentially the same thing for less):

https://gccooling.com/

Ideally you want the condenser tight against the radiator, and preferably with some foam between them on the outer surface. Your gap right now packs air between the heat exchangers and stalls the air going through the condenser. If you close the gap, then more air will flow through the condenser and make it work better.

I'm not sure I agree on the concern where the radiator fans will pull enough vacuum to suck air from the engine bay through the IC in a V-mounted setup that is not divided (on the inlet side between the IC and radiator). Without a fan on the IC, it will heat soak when stopped and traveling at low speeds -with or without a divider). Depending on your application and use, you could put a fan on the IC, if intake charge temps need to be as low as possible from low speeds like drag racing.

coolrotariesR1

iTrader: (2)

Not sure now. This will have to wait because I just put the car up to swap out bushings and other issues.

Montego

iTrader: (1)

Ah ok. I ask because it was never brought up, so we don't have point of reference.

To state the obvious: when using an air-to-air intercooler we are still at the mercy of the ambient temp. Meaning if its 120F outside the best we could ever hope for is 120F intake temps (unless we are physically introducing a cooling agent).

zli944

iTrader: (2)

Barring actually using AI in the intake (which personally didn't actually help with intake air temps for me when I was on the stock IC), you could repurpose something like the AEM kits to be boost controlled intercooler/radiator sprayers.
There's a tracked FD in the area that doesn't use AI but uses the AEM kit for this purpose and it worked well, though they use a lot of water during the process.

Billj747

I'm surprised AI didn't help even on the stock IC. How manybccs were you spraying and what AITs we're you seeing and what power level?

Have a link to that track car? Was it spraying onto the IC?

zli944

iTrader: (2)

I'm not exactly sure but it was the medium nozzle. The tuner's settings for the AEM kit only had it coming on at around 6/7 PSI and ramping up to half of the full output at full boost.
I was tuned for slightly higher than stock, I want to say around 265 whp?
AITs were crazy. During tuning they saw as high as 70C and I want to say I saw it jump up to 80C once on track. I'm using the Triumph AIT sensor.
I thought the sensor was out of spec when I saw these numbers but since I've moved to a V Mount, the temps have stayed in a range that makes sense, so I think my AITs were actually that high.

I do not have a link but he was running nozzles to spray ONTO the IC and radiator and I think also the oil coolers.

My personal solution has been to cut some vents into a spare hood, the Knight Sports V Mount + some ducting, RX8 fan blades and motors on the radiator. Still running just water AI but I think it only comes on after 8 PSI boost. Tuner also set the fans to come on at 81C. Car is tuned to 275 whp on the twins.

I'm in NorCal so ambient temps aren't crazy, I haven't taken it to track yet to see how it would perform there but so far on the street and in pretty heavy traffic under the sun, I've yet to see water temps come above 85C. Air temps after parking the car will read around 50-55C but once I start the car and get moving, I see these drop immediately. The AI's effect is also much more noticeable, where if I go into boost and AI is on, I will see temps drop a few degrees immediately.

Howard Coleman

iTrader: (6)

just posted this in the Single Turbo Section. a recent run to around 7800 (ran out of road)... 26 psi, approx 500/550. note how the IATs flatten with the arrival of approx 1000 cc of meth. max temp out of turbo 416.3 F

coolrotariesR1

iTrader: (2)

The car will be only Street driven. So when you say to put a fan on the IC, that would be on the front side correct?
Building some type of divider should help no?

Billj747

Gotta love data!

Are you running the S300 SXE or EFR9180? ..and are you running the Pettit Cool Charge III intercooler? What's your meth trigger and where do you have the nozzle?

Fans work a lot better in a puller configuration. Grab one of those GC Cooling fans and pick a deeper "paddle" fan if you have room. It will be quieter and move more air.

I'm not sure I buy into the radiator heat soaking the intercooler without a divider concept (in a V-mount). The radiator fans pull air through the radiator and out the back/bottom of it; so air in front of the radiator will not saturate to heat the intercooler. But the radiator touches the IC and the IC is exposed to ~175*+ engine bay temps which is probably the bigger effect on heat soaking an IC at low speeds or when stopped. So a fan on the IC will get some air flow through the core in these common street conditions to keep it from heat soaking.
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0.02

mikejokich

iTrader: (1)

I have addressed heat and airflow management with multiple modifications on my rebuild several years ago. I have many older posts (several years ago) you can look at for some ideas I used. I have a few recent posts also, with the link to the thread below, that was about intercooler spraying.
Air to water intercooler & intercooler sprayers - RX7Club.com - Mazda RX7 Forum
Mike

Howard Coleman

iTrader: (6)

"Are you running the S300 SXE or EFR9180?"

the log was generated by my EFR 9180. i have similar logs from a SXE 62 with two different hotsides. data is similar w re to IATs. the 1.0 hotside on the SXE 62 generated 60 F less EGT and 5 psi less EMP/EMAP v the .91.

IC core is a M2 large which was made by Spearco and remains the best i have tested w re to pressure drop and temps. my setup is similar to the current Pettit but has an airtight seal between the duct and core as well as two puller fans.

"What's your meth trigger and where do you have the nozzle?"

since meth is a fuel i have a serious AI system designed w that in mind. i have run it since 2003. Alkycontrol. no plastic lines etc. the system starts delivery progressively around 13 psi. things happen very fast as to boost. nozzle placement is a bit different w 100% meth. meth atomises above 70 F. optimised nozzle placement locates a bit closer to the IC so the meth has time to fully atomise. water can be closer to the TB as it does most of it's work in the motor. i have recently switched nozzles to ProMeth. i have yet to run them so the log you see is with the usual lower tech brass M10/M15.

check out the tech on the ProMeth offering... lots of swirl and no plastic anywhere. the AEM nozzles are not stainless steel but have adopted Pro Meth's swirl concept.






you vary delivery by swapping the lower piece that has differing slots. i have spent a bunch of time talking w the key guy (Rodney) and he is the real deal. they have vast lengthy experiece w AI-meth and have a wide (widest) array of options. some of which i may be testing. the nozzles, for what they are, are not expensive and are close to a swap in. as mentioned i have yet to run them but they are installed and ready as soon as i am back up and running in a couple of weeks.

mr2peak

Cheapest option, cut some holes in your stock hood. Use a little plastic edging to cover up the cuts and add some mesh over the holes if desired. Vents in the hood will give you the biggest advantage, and you can always do the other stuff later on as well.

Billj747

Interesting. Right at 4:56 your boost is ~16psi and the AITs immediately flatline at 140* before creeping slowly to 160* at the end of the pull. Your AITs are rocketing up before the meth kicks in and it's still nowhere near ambient.

Is that M2 core the 17x12x3.5"? That's ~577cfm core. I'm reaching out to my Motorsports contacts for core recommendations but Id like to see the IC drop the temps a little better than that.

Thanks for the info!

j9fd3s

iTrader: (3)

TLDR: don't go drill holes in the car just yet....

for the Miatas there are kits to add vents, and results are kind of mixed. it didn't not work, but nothing dramatic happened either. this was in a race car BTW, so its WOT for ~15 minutes or more at a time in up to 100f heat
we think the placement of the vents is pretty important.

the one thing it did do, one rainy weekend was when the driver went off, it scooped some mud off the track and put it in his lap...

Howard Coleman

iTrader: (6)

"at 4:56 your boost is ~16psi and the AITs immediately flatline at 140* before creeping slowly to 160* at the end of the pull. Your AITs are rocketing up before the meth kicks in and it's still nowhere near ambient."

"Id like to see the IC drop the temps a little better than that."

i looked at my log and found 15.9 psi...

compressor air temp was 232.2
IAT was 127.6
ambient was 70

232.2 - 127.6 = 104.9
232.2 - 70 = 162.5

104.9/162.5 = 64.5% Intercooler Efficiency

approximately in line with the Spearco data. my bet is you will probably not find a more efficient core than Spearco.



a few years ago i took my windsurfing anemometer (windspeed) and placed it on the rear of my IC core. at 60 mph the windspeed out of my core was just under 5 mph. as most know the primary drawback of the M2 Pettit setup is the small duct. the log posted did not have the fan running nor was the duct anywhere near sealed... so pretty much no windspeed into the core. my new setup has a airtight sealed duct to core and two Spal puller fans so things should improve a bit. notice from the graph that windspeed does help a bunch.

while you can get lost in core depth V frontal area etc keeping it simple... my core has 746 cubic inches and the Greddy V mount has 647. bigger is better. more through flow is better. i have a chart on a Spearco core that is the same displacement as the Greddy and it shows less efficiency since it is less displacement. if you are wondering why i used the 2.85 liters... the BW Matchbot generates the correct pounds per minute charge air flow at that displacement.

for those looking for better efficiency from their ICs, look for a larger volume and a better air through-flow. also, be extremely careful as to the core quality. numerous cores suck.

the big deal about sucking is that as restrictiveness increases the turbo has to work harder. for instance if you have a 1 pound restriction at 20 psi your turbo needs to be making 21. if you have 5 pounds restriction the turbo has to be making 25. the problem is at 25 psi the air exiting the turbo is probably as much as FIFTY degrees hotter.

it still is all about IATs.

Billj747

Compressor air temp - 400*400-70 = 370*64.5% efficiency
370x0.65 = 240.5*

Does this math check out and show that without your meth injection, your AITs would be 240* when the charge air temps are 400*?

You already know the importance of ducting, and since air takes the path of least resistance, poor ducting meant there was virtually no airflow through your previous IC setup, which probably acted more like a heat sink than a heat exchanger.

Your new setups ducting and fans creating low pressure behind the core should greatly increase the pressure differential and flow across the core, and it's effectiveness.

If intercoolers rarely have more than 65% efficiency, would there not be a point where (hypothetically) a thin IC with more volume and a massive surface area would not have more than 65% efficiency?

On that note, would you not get better cooling performance from more airflow through a thinner cooler even if the volume is smaller?
​​​​​​​​​​

Howard Coleman

iTrader: (6)

"Does this math check out and show that without your meth injection, your AITs would be 240* when the charge air temps are 400*?" yes

"You already know the importance of ducting, and since air takes the path of least resistance, poor ducting meant there was virtually no airflow through your previous IC setup, which probably acted more like a heat sink than a heat exchanger." yes.

i know of a specific instance re an NSX that lost 50 rwhp on the dyno purely due to the IC warming from numerous runs.

"Your new setups ducting and fans creating low pressure behind the core should greatly increase the pressure differential and flow across the core, and it's effectiveness." hope so...

"If intercoolers rarely have more than 65% efficiency, would there not be a point where (hypothetically) a thin IC with more volume and a massive surface area would not have more than 65% efficiency?" it gets really complicated

scotty305

iTrader: (2)

For the OP's original question, I agree that ducting (and aluminum tape and/or foam to seal everything) should help force air through the intercooler. If you add a fan, remember that should be ducted also or it won't pull air across most of the core.

When I think big-power turbo cars, I look to the 2JZ and Honda communities more than the RX7 community. The Supra guys building streetable cars tend to run front-mounted intercoolers, do they know something the RX7 community doesn't? IMHO the air temps need to be cooler than coolant temps, so it makes sense for the intercooler to get first priority for fresh air. People building pure race cars use air-to-water intercoolers so they can add ice to the water tank on race day, and locate the heavy water tank near the rear wheels for better traction.

Billj747

For *Drag/Roll Race*

Road course racing does not add ice to A2W intercoolers.

BLUE TII

iTrader: (9)

Adding a fan without 100% sealed ducting (including back of core around the fan) can easily make IC temps worse too.

The fan will pull from the path of least resistance.

On My M2 Large IC with the hood closed the path of least resistance is pulling hot engine bay air through the IC from the back at the edges of the fan heating the IC.

I only use the IC fan (and my water sprayer per rules) between runs with the hood open.

I could put the fan on pusher mode sealed to IC duct within tje duct or I could shroud the back of the IC to the fan like a radiator shroud if I wanted it to work with hood closed.

Narfle

iTrader: (16)

Could probably fab a nice fan shroud for the back, with not too much effort! A couple bends, some snips, and some rubber flaps for 1-way air flow.

Billj747

I'm not sure I agree that a fan needs a shroud on the back of the IC but I agree the front of the IC should have air tight ducting.

mr2peak

Are you actually arguing against a vented hood? A Miata with ~120hp makes a small fraction of the heat of a twin turbo rotary

Sure the placement of vents is important. That said, there's plenty of quantitative evidence that a vented hood on an FD helps with getting rid of heat. Look at the SP vent placement if you need a guide. Blocking the IC from the engine bay heat should make a large difference, just giving the air a place to escape will definitely help. Your IC is either sitting in a hot room next to hot turbos and the windows closed, or a room with the roof open... Put your hands on the hood next time you run the car hard, heat rises, give it a place to rise to... Opening up the hood above the intercooler would be a good start, just make sure it isn't acting like a scoop at speed.

You say a proper vented hood isn't in the cards now. Then you probably don't want to spend $150 on a decent fan, wiring, a relay, and a way to turn it on and off, for some "maybe" improvement, and that's only an improvement when the car is sitting still. A decent vent will work all the time, and will work well at speed when it really matters.

BLUE TII

iTrader: (9)

Trust me, I wanted it to work.

BLUE TII

iTrader: (9)

I think its more that hes saying price out an FD hood and research peoples vented hood results before you start cutting up your FD.

Good option-
There are a bunch of cheap aftermarket vented hoods out there in many configurations.

Or buy a knackered hood to cut up for the vent and then if it works do the bodywork to make it look good.