9krpmrx8's Boost Build Thread
02-02-2015, 07:16 PM
#4001
Hybrid Greddy Boosted
Interesting idea on the radiator hot air ducting. I had a look last night while the undertray was off. There really isn't much room between back of radiator and the intake undertray. Most obvious methods I could see were:
1. Through a new outlet slot cut across the bottom of the under-tray immediately behind the radiator, so hot air flows out under the car.
2. Duct the hot air out the front left wheel well, where left engine mount sits.
Both of these would require a well designed/fitted shroud behind the radiator fans to catch all the hot air.
Team, do you know of working rx8 examples of this that gave noticeable improvements? Hard to justify the work without knowing that there would be some reasonable benefit.
1. Through a new outlet slot cut across the bottom of the under-tray immediately behind the radiator, so hot air flows out under the car.
2. Duct the hot air out the front left wheel well, where left engine mount sits.
Both of these would require a well designed/fitted shroud behind the radiator fans to catch all the hot air.
Team, do you know of working rx8 examples of this that gave noticeable improvements? Hard to justify the work without knowing that there would be some reasonable benefit.
02-02-2015, 10:16 PM
#4002
There are no rx8 examples of it, but there are a couple rx7 examples and plenty of mx5 examples. I can send you some links if you like.
Hood venting is supremely complicated to do without adding allot of drag on the Rx8, because of how everything is positioned. The air filter needs to be moved completely out of the engine bay, battery needs to be relocated, coolant bottle is in the way a little. The radiator is also deceivingly close to the front of the car and the engine.
There's really no reasonable benefit other than dramatically lower underhood temperatures, and faster reactions in temp to things like the thermostat or fans coming on.
I'm making the foam plug for mine now.
Hood venting is supremely complicated to do without adding allot of drag on the Rx8, because of how everything is positioned. The air filter needs to be moved completely out of the engine bay, battery needs to be relocated, coolant bottle is in the way a little. The radiator is also deceivingly close to the front of the car and the engine.
There's really no reasonable benefit other than dramatically lower underhood temperatures, and faster reactions in temp to things like the thermostat or fans coming on.
I'm making the foam plug for mine now.
Last edited by Legot; 02-02-2015 at 10:19 PM.
02-03-2015, 08:04 AM
#4004
Registered
iTrader: (2)
Join Date: Oct 2007
Location: Pacific Northwest
Posts: 16,684
Likes: 0
Received 240 Likes
on
110 Posts
Jimmy,
Both of your thoughts are very bad ideas for aerodynamic reasons. Think about how much air is being 'consumed' by the nose of the RX-8, even at normal legal speeds. Do you really want to shovel that much air under the car? Lift is bad. The wheel wells get pressurized at speed, trying to channel excess airflow into a high pressure area is very suboptimal.
Out of the hood is the most ideal scenario
A) you can leverage a natural low pressure zone there (forward half of the hood)
B) the radiator is already angled to flow air in that direction
C) You can easily design the venting opening to sharply drop the air pressure at that point futher, which further increases efficiently.
In fact, if you were to duct 100% of the 'mouth' air into the radiator and then 100% of the radiator exit out of the hood, you could get by with a much much smaller opening at each end. About 1/4th the surface area of the radiator on the mouth end, and probably as low as 1/2 at the exit (smaller increases pressure relative to the radaitor exit, larger reduces pressure)
None of this is ground breaking or even 'needing proof still'. It's common and leveraged air pressure differentials in everything from road cars to race cars, and plenty of non-car applications too.
It's actually something that can be leveraged more easily with the RX-7/8 than most cars that have a big engine forcing the airflow into more right angles than desireable.
Example from a BMW:
vs FD: (that's actually ducting the intercooler, but similar placement/concept)
Another example, shows most of the ducting:
Both of your thoughts are very bad ideas for aerodynamic reasons. Think about how much air is being 'consumed' by the nose of the RX-8, even at normal legal speeds. Do you really want to shovel that much air under the car? Lift is bad. The wheel wells get pressurized at speed, trying to channel excess airflow into a high pressure area is very suboptimal.
Out of the hood is the most ideal scenario
A) you can leverage a natural low pressure zone there (forward half of the hood)
B) the radiator is already angled to flow air in that direction
C) You can easily design the venting opening to sharply drop the air pressure at that point futher, which further increases efficiently.
In fact, if you were to duct 100% of the 'mouth' air into the radiator and then 100% of the radiator exit out of the hood, you could get by with a much much smaller opening at each end. About 1/4th the surface area of the radiator on the mouth end, and probably as low as 1/2 at the exit (smaller increases pressure relative to the radaitor exit, larger reduces pressure)
None of this is ground breaking or even 'needing proof still'. It's common and leveraged air pressure differentials in everything from road cars to race cars, and plenty of non-car applications too.
It's actually something that can be leveraged more easily with the RX-7/8 than most cars that have a big engine forcing the airflow into more right angles than desireable.
Example from a BMW:
vs FD: (that's actually ducting the intercooler, but similar placement/concept)
Another example, shows most of the ducting:
Last edited by RIWWP; 02-03-2015 at 08:12 AM.
02-03-2015, 08:28 AM
#4005
If you want air to go through the radiator there are ways to accomplish it without blocking everything off. Afterall, some cool air entering the engine bay is blasphemy, sacrilege and heresy all rolled up in one right? Does all the air get forced through or do you end up with a huge backed-up pressure wake out in front of the nose trying to blow your undertray out?
Try to think airflow management instead. Here's my idea of the ultimate RX8 competition turbo setup.
V-mount
Radiator on bottom V, discharge ducted towards rear/underneath
IC on top V, discharge ducted out the hood GT40 style
Center inlet duct from bumper inlet (not full width) with horizontal divider splitting and routing air to both the IC and 2-pass radiator. captures a large portion of air from bumper inlet to the IC & radiator, but also allows some cool air to pass by each side into the engine bay.
Turbo inlet routes fairly straight forward towards front RH side of engine bay into that side stream of cool air. Requires rerouting OE coolant hose snakes nest from upper RH engine, electric water pump.
Eliminate OE UIM. New plenum on top of LIM with TB facing forward.
IC in top v-mount position is fitted with top and bottom headers with both inlet/outlet on RH side - flows bottom to top.
Turbo discharge to bottom RH side on IC, short piping
IC discharge out top RH side 90 into new TB/plenum position, short piping
Zoom-zoom ..... let the criticizing begin
Its a total redesign and a lot of work. Mazda designed it for their purpose. You can kluge your way around that or rework it for your own ...
Last edited by TeamRX8; 02-03-2015 at 11:00 PM.
02-03-2015, 08:38 AM
#4006
Registered
iTrader: (2)
Join Date: Oct 2007
Location: Pacific Northwest
Posts: 16,684
Likes: 0
Received 240 Likes
on
110 Posts
The only disagreement i have to that is the radiator ducting out the bottom. I'd probably object less for a road car, but there are ways to split the ducted flow to ensure both the radiator and intercooler get their needed separate airflow streams that can then both go out the hood. The simpler option would still mean losing a bit of radiator efficiency for the overlapped section of the stream, though you can get creative to solve that too.
You would want the flows divided through ducting anyway, otherwise the resistance to flow each of them will have could result in one seeing more flow than it needs and one not seeing enough.
For example, this Miata has the flow split in the mouth via ducting, one to the radiator and one to the oil cooler.
You would want the flows divided through ducting anyway, otherwise the resistance to flow each of them will have could result in one seeing more flow than it needs and one not seeing enough.
For example, this Miata has the flow split in the mouth via ducting, one to the radiator and one to the oil cooler.
02-03-2015, 09:18 AM
#4008
SARX Legend
Thread Starter
iTrader: (46)
Yes you don't want to force air thru by having the duct work sealed up tight, there needs to be a way for excess pressure to escape. Which is one of the reasons the front under tray has vents in it.
I have some ideas already but I will have to read up and give it some thought but yes a lot of stuff will need to be reworked and relocated. One thing I know for sure is that you need a tray under the intake, if you log intake temps with and without in Texas during the summer you will see why.
I have some ideas already but I will have to read up and give it some thought but yes a lot of stuff will need to be reworked and relocated. One thing I know for sure is that you need a tray under the intake, if you log intake temps with and without in Texas during the summer you will see why.
02-03-2015, 10:47 AM
#4009
Driving my unreliable rx8
Add a small lip across the front of your hood vent. To reduce pressure behind it while providing downforce on the front of the car.
It wouldn't need to be big. 1/2" would make a significant difference. It would kill top end speed but a turbo car would still have plenty.
It wouldn't need to be big. 1/2" would make a significant difference. It would kill top end speed but a turbo car would still have plenty.
02-03-2015, 11:56 AM
#4011
Registered
My current setup is with;
racing beat intake duct going into the re-amemiya intake box,
Saw a 2 degree Celsius drop in temperature and the measured temperature cools much faster than stock (as seen from my ODBII reader & Torque)
The spring set-up will be with the re-amemiya D1 hood I've purchased. I'll log some temperature numbers to share with you guys.
A local rx7 owner has his re-amemiya hood installed last spring and saw a 5 degree Celsius drop in temperature with the rain ducts removed.
racing beat intake duct going into the re-amemiya intake box,
Saw a 2 degree Celsius drop in temperature and the measured temperature cools much faster than stock (as seen from my ODBII reader & Torque)
The spring set-up will be with the re-amemiya D1 hood I've purchased. I'll log some temperature numbers to share with you guys.
A local rx7 owner has his re-amemiya hood installed last spring and saw a 5 degree Celsius drop in temperature with the rain ducts removed.
It's a good thing he has a pretty car 
02-10-2015, 09:27 AM
#4022
FULLY SEMI AUTOMATIC
iTrader: (9)
damn you 9k. that post need a dislike button
