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In general, I agree that the "old school" of jdm tuning didn't produce a properly vented, ducted, sealed etc system. For modern jdm build, I came across Rock Suzuki's FD (Under's younger brother) and his 3-rotor setup seems quite efficient. Cold air for charge pipe, large IC core, pretty straight plumbing, etc. The inlet / outlet orientation on the end tanks looks really nice as well imo. Of course there are limitations to any build (typically talent, resources and / or support) but you don't seem to lack any of those. My personal taste prefers to see short piping with minimal bends, etc. Just curious why you didn't go for something closer to what Rock did?
The intercooler plumbing is very well laid out and I don't think I've seen an FD with a straighter path than that. While straighter and shorter the plumbing with fewer bends is better, but the realistic difference in pressure loss or transient response in practice probably isn't that significant. V-mounted FDs in general already have relatively fewer bends and short plumbing compared to most cars.
To answer your question directly: I didn't go with that routing because of packaging. I wanted to simplify the ducting in my design by using the frame rails as part of the mounting surface of the intercooler core, and had to run the charge pipes to clear the fuse boxes and where I mounted my CDI box. Maybe once I redo the wiring harness, relocate or replace the fuse boxes with a PDM, and if I can clear the CDI box, I will have the room to make a straighter-shot to the throttle body and I can use a thicker intercooler to have a similar layout to the Rock 3-rotor.
Project FD RX7 Restomod: Part 31 – Re-designing the Oil Cooling System
The FD RX-7’s factory oil cooler(s) are barely adequate for stock horsepower. To handle our increased power and track use, we completely redesigned the entire oil cooling system with Hayden HD Cool oil coolers, Earl’s UltraPro stainless steel lines, Radium Engineering fittings and catch can, Raceonly oil fill neck and power steering reservoir, and we relocated the oil filter and thermostat with Improved Racing.
In the article:
-Analyzing the Stock Oil Cooler
-Hayden HD Cool "778" Oil Coolers
-Oil Cooler Ducting
-Improved Racing Remote Engine Oil Filter Mount & Thermostat
-How to Make Earl's Performance Stainless Steel Hose
-Oil Plumbing in Series vs Parallel
-Radium Low Profile Swivel Fittings
-Raceonly Billet Remote Oil Filter Pedestal & Front Iron Oiling
-Raceonly Billet Oil Filler Neck
-Improved Racing Catch Can
-Crank Venting from Gutted OMP Port
-Custom Turbo Drain Fittings
-Raceonly Billet Power Steering Reservior
I disagree with the premise that the stock twin oil coolers are insufficient for track use.
I think as long as you have a v-mount (and ideally a vented hood), it's sufficient for 300+ whp on the track (although everyone I know vents them into the wheel wells rather than the stock fender vent).
You start to get in trouble closer to the 400 whp mark.
Oil cooling is just part of the system. You can GET AWAY with less if you maximize other parts, but oil temps and water temps are interconnected, so one helps the other and vice versa. The addition of aftermarket coolers made my water temps more stable. And of course power levels influence it, but so does how you're driving, i.e.: if you're going fast, temperatures and breakages increase exponentially. At one point I lowered my times by 4 seconds at VIR on largely the same power level, and that massively increased the strain on the system. With a V-mount being $3k, and a hood being $.5k, $1k worth of oil coolers is def worth the effort. You almost can't have too much.
The ducting, though, is the key. Don't bother unless you've got a plan for it. Billy, I owe you some specs if you're still game to make me a set.
I disagree with the premise that the stock twin oil coolers are insufficient for track use.
I think as long as you have a v-mount (and ideally a vented hood), it's sufficient for 300+ whp on the track (although everyone I know vents them into the wheel wells rather than the stock fender vent).
You start to get in trouble closer to the 400 whp mark.
Transmission temperatures, though...
its all relative also in the sense that different tracks and ambient temperatures have different requirements.
and how many sessions can you actually run before you are cooking that oil ?
I have seen stock coolers going 105-110C oil temp in only a few laps whereas a system with much larger coolers can do a lot more without going over 85C...
and since you mentioned the transmission cooler. i think after a certain point the transmission cooler is inevitable
its all relative also in the sense that different tracks and ambient temperatures have different requirements.
and how many sessions can you actually run before you are cooking that oil ?
I have seen stock coolers going 105-110C oil temp in only a few laps whereas a system with much larger coolers can do a lot more without going over 85C...
and since you mentioned the transmission cooler. i think after a certain point the transmission cooler is inevitable
Yeah, I agree that everyone's situation is different. I don't ever see temperatures above 90/90 pretty much regardless how hard I run the car, but I run very conservative boost.
My transmission is on it's last legs, since it was a freebie from a friend with well over 100,000 km... He's surprised it still hasn't broken.
Oil cooling is just part of the system. You can GET AWAY with less if you maximize other parts, but oil temps and water temps are interconnected, so one helps the other and vice versa. The addition of aftermarket coolers made my water temps more stable. And of course power levels influence it, but so does how you're driving, i.e.: if you're going fast, temperatures and breakages increase exponentially. At one point I lowered my times by 4 seconds at VIR on largely the same power level, and that massively increased the strain on the system. With a V-mount being $3k, and a hood being $.5k, $1k worth of oil coolers is def worth the effort. You almost can't have too much.
The ducting, though, is the key. Don't bother unless you've got a plan for it.
I don't dispute that it's a good mod to do. I think my problem was with the statement that they're insufficient at near-stock power levels.
I don't actually have ducting, but oil temps aren't a problem, so I haven't got around to making any.
I disagree with the premise that the stock twin oil coolers are insufficient for track use.
I think as long as you have a v-mount (and ideally a vented hood), it's sufficient for 300+ whp on the track (although everyone I know vents them into the wheel wells rather than the stock fender vent).
You start to get in trouble closer to the 400 whp mark.
Transmission temperatures, though...
mdpalmer made ~270whp on stock twin turbos and saw 240*F oil temps when running dual R1 oil coolers. He couldn't last a complete 25-minute session without water temps climbing above 230*F.
As ptrhahn and R-R-RX7 said: Running cooler oil temps will help bring down water temps and vice versa. Different tracks, weather conditions, power, cooling system, and driver experience can all vary greatly in the demands and cooling ability of an FD on track.
240*F isnt great and with a better driver that drives the car harder, and/or adding 30whp will add a lot more energy and heat into the cooling system, making the oil temps significantly higher.
There is documented proof by multiple people that stock dual R1 oil coolers are NOT adequate "for much beyond stock power levels on track". There are a lot of experienced track guys in SoCal who constantly struggle in the 350-375whp range to keep charge temps, oil, and water under control for a full session. A less experienced driver than these guys might be fine at 400whp+, but when an experienced driver pushes a car, it becomes much more difficult.
mdpalmer made ~270whp on stock twin turbos and saw 240*F oil temps when running dual R1 oil coolers. He couldn't last a complete 25-minute session without water temps climbing above 230*F.
My contention is that the stock coolers would have been fine with other track-oriented cooling mods in place. Apparently, they were good enough for the Bathurst 12h cars (or at least I can't find any mention of the oil coolers being upgraded) making similar levels of power.
As ptrhahn and R-R-RX7 said: Running cooler oil temps will help bring down water temps and vice versa. Different tracks, weather conditions, power, cooling system, and driver experience can all vary greatly in the demands and cooling ability of an FD on track.
240*F isnt great and with a better driver that drives the car harder, and/or adding 30whp will add a lot more energy and heat into the cooling system, making the oil temps significantly higher.
Sure. I'm not arguing they're going to be sufficient in all cases.
There is documented proof by multiple people that stock dual R1 oil coolers are NOT adequate "for much beyond stock power levels on track". There are a lot of experienced track guys in SoCal who constantly struggle in the 350-375whp range to keep charge temps, oil, and water under control for a full session. A less experienced driver than these guys might be fine at 400whp+, but when an experienced driver pushes a car, it becomes much more difficult.
I don't define 350-375 whp as "not much beyond stock power." I define it as far beyond stock power." So, maybe this is simply a difference of interpretation.
I know a handful of people for whom the stock coolers are sufficient, and at least one for whom they are not. That's why I said you get into trouble closer to 400 than 300.
My contention is that the stock coolers would have been fine with other track-oriented cooling mods in place. Apparently, they were good enough for the Bathurst 12h cars (or at least I can't find any mention of the oil coolers being upgraded) making similar levels of power.
Unfortunately, this does not seem to be a reality with a good driver on factory twin turbos. One of the fast SoCal FD track guys makes 280whp on factory twin turbos and had similar experiences to mdpalmer (in the link above) and would see oil temps rise to 260*Fwithin a few laps with the stock R1 dual oil coolers AND a V-mount setup!
These two examples show consistent results of 240-260*F+ oil temps within a session with stock R1 dual oil coolers, factory twin turbos and 270-280whp which is NOT adequate "for much beyond stock power levels on track".
Another major variable is the turbo. Once he swapped to a single turbo, he is making 302whp with 190*F coolant and 220*F oil with the same setup.
In regards to the Bathurst 12-hour FDs, it appears they are making 273bhp at 10psi on sequential turbos. That is 18hp more than stock with upgraded intercoolers, radiators, and ECU tuning designed for endurance racing. I'm sure they weren't using an off the shelf Koyo radiator and were able to improve the water cooling quite a bit better than what 99% of people buy online.
Stock FDs seem to make around 210-230whp. Here's a dyno of a stock FD with a downpipe and cat-back exhaust:
I would guess the Bathurst cars are in the 230-250whp range with motorsport-level ECU calibrations and radiators.
Originally Posted by Valkyrie
I don't define 350-375 whp as "not much beyond stock power." I define it as far beyond stock power." So, maybe this is simply a difference of interpretation.
I didn't either. I was agreeing with your statement of "You start to get in trouble closer to the 400 whp mark." and added that everything becomes extremely difficult to keep cool at an even lower power level than you said.
Originally Posted by Valkyrie
I know a handful of people for whom the stock coolers are sufficient, and at least one for whom they are not. That's why I said you get into trouble closer to 400 than 300.
Whether the factory R1 dual oil coolers is 'sufficient' depends on a ton of factors, the biggest one being driver experience and ability. I'm sure there are examples of novice drivers who make 500whp and would not overheat their oil with R1 coolers because they spend very little time at full throttle.
Overall, the cooling system encompasses many aspects which makes it difficult to single out any one component without considering the entire system as a whole. However, it appears that consumer-grade V-mounts and tuning at 260-280whp, it does not seem that the factory oil coolers are sufficient if a good driver is behind the wheel. If you aren't running into oil temp problems on track.... first off, congrats on tracking the FD! Secondly, there's nothing wrong with that, but as you get more experience and turn faster laps, it's likely the oil coolers will eventually hold you back and reliability can be improved by upgrading them.
Disclaimer:
**YOU NEED TO BE MEASURING OIL TEMPS BEFORE THE OIL COOLER AND IDEALLY IN THE OIL PAN. NOT POST-COOLER AT THE PEDESTAL! Measuring at the pedestal will give you artificially low numbers and a 20-40*F unrealistic 'cushion'. Every factory car on earth measures the engine temp or cylinder head temp at or after the engine, never after the radiator. If you're only going to measure one oil temp, measure pre-cooler.
That is 18hp more than stock with upgraded intercoolers, radiators, and ECU tuning designed for endurance racing. I'm sure they weren't using an off the shelf Koyo radiator and were able to improve the water cooling quite a bit better than what 99% of people buy online.
The 12hr cars were production based, the ones running at Bathurst in particular, would have been pinged without stock rads in parc ferme, really the only changes permitted for those were safety related.
After Bathurst became cost prohibitive for the promoter, and they raced at Eastern Creek, the new 25-off locally produced SPs were again production based and the Mazda Australia ones were actually repurposed earlier Bathurst cars. There was lots of testing to ensure components would work for the purpose and last, I could be wrong after last looking 10+ years ago, I don't remember ever seeing the water radiator listed in the published spec sheet as changed. With the SP nosecone, undertray bridge and the cf pieces under the oil coolers and ducting, heat exchangers were probably up to the task. The major difference here, which won't apply in most of the northern hemisphere, even though you still get the odd high 30 to mid 40C day to bookcase the year, racing season is generally conducted in winter.
Do know the ECU had to be factory, but was tweaked to accomodate the performance changes.
It's funny, admittedly professional drivers and somewhat better "treaded" tyres in use, on a 1 or 2 second slower track configuration back then, I see some of these time attack types spending thousands on aero and hp and are only marginally quicker than 30 years ago....investment in seat/sim time might pay more dividends for a lot of them.
@Billj747 curious why you didnt go with bigger coolers. There is room for bigger coolers . What is the ultimate purpose of the car? Street or track? Something in between?
The 12hr cars were production based, the ones running at Bathurst in particular, would have been pinged without stock rads in parc ferme, really the only changes permitted for those were safety related.
After Bathurst became cost prohibitive for the promoter, and they raced at Eastern Creek, the new 25-off locally produced SPs were again production based and the Mazda Australia ones were actually repurposed earlier Bathurst cars. There was lots of testing to ensure components would work for the purpose and last, I could be wrong after last looking 10+ years ago, I don't remember ever seeing the water radiator listed in the published spec sheet as changed. With the SP nosecone, undertray bridge and the cf pieces under the oil coolers and ducting, heat exchangers were probably up to the task. The major difference here, which won't apply in most of the northern hemisphere, even though you still get the odd high 30 to mid 40C day to bookcase the year, racing season is generally conducted in winter.
Do know the ECU had to be factory, but was tweaked to accomodate the performance changes.
It's funny, admittedly professional drivers and somewhat better "treaded" tyres in use, on a 1 or 2 second slower track configuration back then, I see some of these time attack types spending thousands on aero and hp and are only marginally quicker than 30 years ago....investment in seat/sim time might pay more dividends for a lot of them.
Thank you for the information. I was intrigued and did a little research myself and apparently the 1994 Bathurst 12-hour-winning Crompton/Hansford RX-7 was taken out of the Bathurst museum back in 2014-2016 and a few journalists got to drive it and then in 2024, Mark Williamson (who won the Bathurst 3-hour) drove it around the streets in a YouTube video. The car seems to have an upgraded intercooler at some point, but there are photos from 2016 where the car has a virtually stock engine bay.
Nevertheless, it's pretty impressive that the FD won a 12-hour race 3 times in a row at Bathurst in relatively showroom stock form. It's a bit hard to say if any part of the cooling system was modified but there seems to be more likelihood that they were (or mostly were) stock or close to stock. In such case, keeping stock levels of 10psi of boost and a ballpark of 210-250whp might be reliable with stock or near stock cooling, but if you start to bump the power even a little at 260-270whp, people start running into serious cooling trouble, especially with 30-year old coolers.
Originally Posted by R-R-Rx7
@Billj747 curious why you didnt go with bigger coolers. There is room for bigger coolers . What is the ultimate purpose of the car? Street or track? Something in between?
The 21-row Hayden HD Cool "778" oil cooler is 8.78" tall and very similar in cooling ability to the more common 5.75" tall 19-row Setrab. This cooler is already pretty tight fitment when retaining the stock popup headlight buckets. The Hayden "779" is over 2" taller and would be more difficult to fit.
This car is built to be heavily tracked, make a lot of power, and have "OEM+" street car refinement. Achieving 2 of these isn't too difficult, but all 3 is a huge challenge. We will be testing our custom radiator and oil cooling setup in the near future and will report the results and if needed, we will continue to tackle and improve the systems.
Last edited by Billj747; Jan 10, 2026 at 12:31 AM.
That makes perfect sense. I dont know the Hayden models . Didnt realize that they were bigger. Thanks for clarifying.
thats actually one of my issues with my coolers…. I cant fit the pop up headlights anymore. I wish I kept that option but that ship has sailed a long time ago
That makes perfect sense. I dont know the Hayden models . Didnt realize that they were bigger. Thanks for clarifying.
thats actually one of my issues with my coolers…. I cant fit the pop up headlights anymore. I wish I kept that option but that ship has sailed a long time ago
I just looked up your build and see that you have the 25-row setrab coolers and a 3rd, central oil cooler:
Originally Posted by R-R-Rx7
Impressive work. I commented on your build page. Do you really live on the island of Limassol Cyprus? You're probably the only FD there! I couldn't find any race tracks on the island, what did you build your car for? (street/track).
If you have tracked it, what are your oil temps and where are you measuring your oil temps?
I just looked up your build and see that you have the 25-row setrab coolers and a 3rd, central oil cooler:
Impressive work. I commented on your build page. Do you really live on the island of Limassol Cyprus? You're probably the only FD there! I couldn't find any race tracks on the island, what did you build your car for? (street/track).
If you have tracked it, what are your oil temps and where are you measuring your oil temps?
I am from Cyprus, I dont live there anymore but my folks are there. My car is there. i have been living in the States for almost 20 years now. and a few years in the UK before that
I do spend most of the time at the track when i visit. with the 34 row coolers and the disgustingly hot climate of July/August (reaching around 43-45C ambient temperature) at the pedestal i am measuring ~80-82C and coolant up to 86C.
I used to measure pre cooler and post cooler in my previous setup (for oil and coolant) but with my new setup i have simplified the system. I used to do the same for the EGT pre turbo and post turbo temps but i think its overkill.
There is 1 race track over there, Achna Speedway.
There are a few go-kart tracks. One of the Go-Kart tracks is big enough for cars but just barely..
There were plenty of rx7s in cyprus. not so much anymore. a few good examples were exported, and the rest are at the mercy of the local "craftsmen" . The nice thing about Cyprus is that we use the right hand drive system because we were a british colony. Importing a car from japan to cyprus is incredibly easy. i have had many late models rx7s and other jdm cars over the years
as for the purpose, i wanted it to be a true dual purpose. to be real fun at the track, and be civilized enough to be used on the streets without getting a migraine when i am done.
i am planning a eurotrip with my Rx7 probably later this year. so i dont want to draw anyone's attention, with an annoying exhaust and drive for thousands of miles without being overly tiresome . I am planning to visit multiple racetracks during this journey.
So 43-45C in July/August (109-113*F) is pretty darn hot! Are you measuring oil at 80-82*C (176-180*F) and coolant at 86*C (187*F) with your current cooler setup? (you clarified on your build thread that the center thin oil cooler is for the transmission).
Where did you use to measure oil temps pre-cooler? What temperature difference did you see before and after the cooler?
I would imagine your actual engine oil temps (at the pan, pre-cooler) are around 30*F hotter than that so: 206-210*F (96.6-98.9*C) which isnt' bad at all. I would also venture to say that you might be able to get 80-82*C (176-180*F) PRE cooler with some good ducting.
So 43-45C in July/August (109-113*F) is pretty darn hot! Are you measuring oil at 80-82*C (176-180*F) and coolant at 86*C (187*F) with your current cooler setup? (you clarified on your build thread that the center thin oil cooler is for the transmission).
Where did you use to measure oil temps pre-cooler? What temperature difference did you see before and after the cooler?
I would imagine your actual engine oil temps (at the pan, pre-cooler) are around 30*F hotter than that so: 206-210*F (96.6-98.9*C) which isnt' bad at all. I would also venture to say that you might be able to get 80-82*C (176-180*F) PRE cooler with some good ducting.
I had added a sensor on the inlet of the thermostat. it was a fitting similar to that
I had some issues with the coolant after I had simplified the system and its been a few years but if i recall i had approximately 10-12C difference on the coolant and 15-18C on the Oil. its been 4-5 years and i am going purely on memory, I could be wrong .
This is where i had made the thermostat delete part but i may go back to an actual thermostat or finally install the electric waterpump that has been sitting on my shelf for years .
what i have done to improve my system now is that i have the both the TC-4 and the TC-8 hooked on the haltech. so I can add a thermocouple pretty much on the fly to easily reference stuff at the track. it came handy once
Project FD RX7 Restomod: Part 32 – Deatschwerks DW400 Fuel Pump and Fixing Fuel Starvation
We upgrade the fuel pump to a Deatschwerks DW400 and fix the FD RX-7’s notorious fuel starvation issue by making a surge tank and using a DW100 lift pump paired to a Holley HydraMat mounted in the tank.
FD RX-7s are notorious for fuel starvation issues on road courses when the fuel level drops below ¾ of a tank, and especially when the fuel is below ½ a tank. To solve this problem, we created a surge tank out of the stock plastic fuel pump baffle by using the GarageAlpha Hyper Fuel Baffle/Surge Tank Cover, a Holley HydraMat, Deatschwerks DW100 lift pump, and a few CV100 fuel cell surge tank check valves.
In the article:
-Holley HydraMat
-Deatschwerks DW400 Fuel Pump (with flow a chart vs Walbro 525 "Hellcat" pump)
-Deatschwerks DW100 Lift Pump
-Surge Tank Check Valves
-GarageAlpha Hyper Fuel Baffle/Surge Tank Cover
-Radium Engineering Electrical Bulkhead Stud Kit
-Holley 4-Wire Horse Shoe Bulkhead Kit
-Stock Fuel Hat Disassembly and Modification
-Stock Fuel Tank Analysis
This gives me some ideas. I wonder if HydraMat and a lift pump to keep my FEED baffle box full would allow me to run with less fuel at a significantly lower cost than the Radium surge tank kit.
On another note, I would love to see the car in action. For the longest time I had assumed it wasn't being driven.
This gives me some ideas. I wonder if HydraMat and a lift pump to keep my FEED baffle box full would allow me to run with less fuel at a significantly lower cost than the Radium surge tank kit.
On another note, I would love to see the car in action. For the longest time I had assumed it wasn't being driven.
That's essentially what I did with the GarageAlpha baffle.
The car runs and has been to the dyno w couple times. I'm swapping ECUs again (the car will be going on its 5th ECU) and then will start testing more parts. I'm a bit behind on the articles, this fuel system was done well over a year ago when the car wasn't running.
That's essentially what I did with the GarageAlpha baffle.
The car runs and has been to the dyno w couple times. I'm swapping ECUs again (the car will be going on its 5th ECU) and then will start testing more parts. I'm a bit behind on the articles, this fuel system was done well over a year ago when the car wasn't running.
Can you describe how you wired the six-wire connector into the car? Or is that an upcoming article?
Can you describe how you wired the six-wire connector into the car? Or is that an upcoming article?
2 wires go to the factory connector for fuel level. 2 grounds to the chassis (for main and lift pumps), and 2 power that go to a relay for direct power from the battery triggered by the ECU.
Originally Posted by cloud9
Cliff notes version for why the continued trial and change of ECUs?
Like which have you used, why did you think they worth trying, and what capability or value were you not getting that motivated you to switch?
1 - OEM
2 - power fc (previous owner installed)
3 - adaptronic (which was bought out by Haltech and pretty much killed off)
4 & 5 - will be discussed in a future article.
1 - OEM
2 - power fc (previous owner installed)
3 - adaptronic (which was bought out by Haltech and pretty much killed off)
4 & 5 - will be discussed in a future article.
Ok thanks. 1, 2, & 3 are self explanatory. Will be curious to see impressions shared about mystery ECUs in said article.
