Mazda Rotary Club

Cars by Model Type => 3rd generation RX-7's => Topic started by: Jono FD3 on September 24, 2008, 10:18:46 PM

Title: Undertrays.....??
Post by: Jono FD3 on September 24, 2008, 10:18:46 PM
Guys, I\'m looking at making some under trays (splitters or what ever you want to call them!!) Basicaly to reduce the flow of air through my rad (as I can\'t get the temps above 73 while driving!!) Has anyone got any images of front undertrayd on the FD\'s??

Also looking at making a rear defusor for the car as I\'m not realy keen on the ones that are on the market at the mo as they are eather not enough, or OTT for the styling on my car!!

Pics of both front & rear options would be apreciated!!

Found this on the front under trays & makes for some interesting reading.... what you guys think???

http://autospeed.com/cms/A_2456/article.html

Jono
Title: Undertrays.....??
Post by: Nik da Greek on September 24, 2008, 10:25:22 PM
Interestin link. I dunno if I\'m hopelessly wrong here (usually am) but I thought the undertray was an important aid to cooling on the FD :confused:? I thought it basically boxed in the front aperture to the radiator, creating a high pressure area in front of the radiator, and a low presure one behind, forcing more air in the front and sucking air out and away down the trans tunnel and under the car. If that\'s the case, wouldn\'t making an undertray make your car run even more cool than it does already? Can\'t help but be a good idea for aerodynamic efficiency, though :Thumbs-up
Title: Undertrays.....??
Post by: AtomicRex on September 24, 2008, 11:50:04 PM
Best thing you can do is to block part of the rad off
 
Are you sure your gauge is working fine?
Are you sure you havent got an air lock??  If you are using the standard pic up point they are crap....you need to put a sensor in the water as a lot of the time that is just in air.
Title: Undertrays.....??
Post by: Hayward North on September 25, 2008, 12:50:30 AM
Have a look at post 22 of mine on here http://www.mazdarotaryclub.com/forums/showthread.php?t=48807&highlight=undertray
This is what i did to mine
Title: Undertrays.....??
Post by: Steve-Q on September 25, 2008, 08:00:17 AM
I used to run a rotax max 125cc racing go kart and to get the rad temp right we used to used some extra special technical supa dupa duck tape and block a bit of it off, worked a treat. :rollinjust try that first, and its cheaper. if that makes nooooo difference then you know youve got a problem.  
 
Regards
 
Steve
Title: Undertrays.....??
Post by: SiH on September 25, 2008, 08:04:07 AM
Quote from: Nik da Greek;540001Interestin link. I dunno if I\'m hopelessly wrong here (usually am) but I thought the undertray was an important aid to cooling on the FD :confused:? I thought it basically boxed in the front aperture to the radiator, creating a high pressure area in front of the radiator, and a low presure one behind, forcing more air in the front and sucking air out and away down the trans tunnel and under the car. If that\'s the case, wouldn\'t making an undertray make your car run even more cool than it does already? Can\'t help but be a good idea for aerodynamic efficiency, though :Thumbs-up

My understanding too :)

Low pressure under bonnet = good, air drawn into bay through path of least resistance. Make that the front bumper aperture, duct it all through th eIC and rad, and you\'re laughing :)

I\'ve got a MazdaSpeed Undertray and diffuser, I\'ll try to get piccies up at the weekend.
It runs noticeable cooler with the undertray on, and is also more stable at speed.
Title: Undertrays.....??
Post by: RemarkLima on September 25, 2008, 08:26:05 AM
I Jono, I take it you\'ve also replaced your thermostat? Or as said the sensor isn\'t out of voltage?

As with the correct thermostat even if you had Hurricane Ike coming through your radiator it wouldn\'t reduce the temps any further than the thermostat temp as it\'s not allowing any coolant to pass to the rad IYSWIM.

So seems a bit crazy to deflect air away from the rad, as you MAY need that air if it\'s a hot day and you\'re giving it some welly!
Title: Undertrays.....??
Post by: Kevin on September 25, 2008, 09:49:31 AM
I\'d just like to echo the fact that i\'d start looking into the fact of why your running at such a low temp before you do anything regarding airflow.

These cars run so hot that your temps dont really add up.  It almost sounds like you\'ve got a drilled thermostat, obviously you havent but definately check all the cooling system first.

Or as above check the sensors that they are giving the correct reading.  Would hate for you to block airflow off and result in cooking your car.
Title: Undertrays.....??
Post by: Jono FD3 on September 25, 2008, 11:52:10 AM
LOL... There is a logical reason for it running so cool ;) The car has a Vmount & a std bonnet lifted at the rear, also a deflector shield behind the rad, so the rad is going to be getting 80 - 90% of the air flow! My thought was by putting a front defusor on her and making a sliding pannel so I can ajust the amount of air flow through the rad, that would solve my problems.
The temps are taken from the PFC commander & not an aux gauge!! infact when I had a second gauge in, it read lower than it should!!

Jono
Title: Undertrays.....??
Post by: ttpower on September 25, 2008, 11:53:37 AM
Hi Mate,

Im currently at late prototype stages of both undertrays and rear diffusers and other bits and bobs! Just waiting for the final wind tunnel results from Japan before we can go ahead in full production. Will keep you all posted :Thumbs-up
Title: Undertrays.....??
Post by: RemarkLima on September 25, 2008, 12:03:55 PM
Quote from: Jono FD3;540100LOL... There is a logical reason for it running so cool ;) The car has a Vmount & a std bonnet lifted at the rear, also a deflector shield behind the rad, so the rad is going to be getting 80 - 90% of the air flow! My thought was by putting a front defusor on her and making a sliding pannel so I can ajust the amount of air flow through the rad, that would solve my problems.
The temps are taken from the PFC commander & not an aux gauge!! infact when I had a second gauge in, it read lower than it should!!

Jono

I hear what your saying dude, but as said, if the thermostat is in good order (you may have a lower temp one, or as said it\'s been drilled out) then no matter how much air is going through the rad the temps will remain at the thermostat temp.

If the water in the engine block is 70C and the thermostat doesn\'t open until 80C then no water at all is going to the rad so it wouldn\'t make any odds how much or little air is passing through it, if that makes sense?
Title: Undertrays.....??
Post by: nikp on September 25, 2008, 02:01:29 PM
Quote from: RemarkLima;540104I hear what your saying dude, but as said, if the thermostat is in good order (you may have a lower temp one, or as said it\'s been drilled out) then no matter how much air is going through the rad the temps will remain at the thermostat temp.

If the water in the engine block is 70C and the thermostat doesn\'t open until 80C then no water at all is going to the rad so it wouldn\'t make any odds how much or little air is passing through it, if that makes sense?

Agreed. Doesn\'t matter (in theory) if it is in a blizzard in -20: the thermostat will just shut to allow the coolant to warm up, then open when warm, and shut to warm it back up again: it\'s a regulater. It doesn\'t start to open till about 81 degrees.
Title: Undertrays.....??
Post by: Kevin on September 25, 2008, 03:11:03 PM
Quote from: Jono FD3;540100LOL... There is a logical reason for it running so cool ;) The car has a Vmount & a std bonnet lifted at the rear, also a deflector shield behind the rad, so the rad is going to be getting 80 - 90% of the air flow! My thought was by putting a front defusor on her and making a sliding pannel so I can ajust the amount of air flow through the rad, that would solve my problems.
The temps are taken from the PFC commander & not an aux gauge!! infact when I had a second gauge in, it read lower than it should!!

Jono


On one of my FD\'s I have an RE-amemiya D1 spec vmount with 3 core rad and intercooler, sheet metal ducting and a mazdaspeed vented bonnet.  I can never get my temps lower than 81 when doing general driving.

There\'s definately something not quite right for you to be getting those readings.

Just as a matter of interest when your stuck in traffic what are the temps?  Or if you leave it idling for a minute or two after driving?  Are they in the 80/90\'s or still at the 70 mark?  Or does the temps drop as soon as you start driving?
Title: Undertrays.....??
Post by: nikp on September 25, 2008, 03:46:50 PM
Quote from: Kevin;540163Just as a matter of interest when your stuck in traffic what are the temps?  Or if you leave it idling for a minute or two after driving?  Are they in the 80/90\'s or still at the 70 mark?  Or does the temps drop as soon as you start driving?

Some good Q\'s there.
Title: Undertrays.....??
Post by: Jono FD3 on September 25, 2008, 09:58:33 PM
Sat in traffic the water temps get up to late 80\'s (don\'t get much traffic down here to be honest...... 4 cars is a traffic jam :) ) but then with in half a mile to a mile the temps are right down again!! water is up to the mark on both the filler neck & expansion bottle!! what temp do the cold thermostats run at?? just wondering as when I was driving it at 6am the other day, it didn\'t drop below 69c but didn\'t go above 72c on a 40 mile run ???

I\'m confused!!

Jono
Title: Undertrays.....??
Post by: Kevin on September 25, 2008, 10:11:50 PM
Quote from: Jono FD3;540314(don\'t get much traffic down here to be honest...... 4 cars is a traffic jam :) )

Lucky you! lol.

QuoteSat in traffic the water temps get up to late 80\'s

QuoteI was driving it at 6am the other day, it didn\'t drop below 69c but didn\'t go above 72c on a 40 mile run ???

It definately sounds like a thermostat problem.  Your temps appear to be phased by about 10 degrees if you get what I mean.  Normal temps should be around 82-85 whereas your getting 72, then stuck in traffic can be anything upto late 90\'s depending on when your fans kick in so yours are late 80\'s.

Therefore if they drop that drastically the water temp is not being regulated, again pointing to a thermostat problem.

Cold thermostats dont run that cold as standard operating temps on the FD should be around 81+ degrees.
Title: Undertrays.....??
Post by: Jono FD3 on September 25, 2008, 10:21:48 PM
cool (no pun intended), The other thing is... I have got metal water pipes from the rad to the block (both to and from) so that would drop the temp a little too, would it not???
I\'ll get a new thermostat and try that first then!! would make my econamy a little better too I\'d of thought!! what sort of price are they & do I need any gasgets / O rings to do the job?

Jono
Title: Undertrays.....??
Post by: Kevin on September 25, 2008, 10:28:24 PM
There only cheapish, I dont think i\'ve ever paid more than a tenner for one (on any car), but it\'s been a while since i\'ve ordered one.

If you wana order a performance one, SARD do one for about 60 quid, but in this case I think your better off getting a genuine mazda one, seeing though your running a v-mount anyway.

I really dont think the metal water pipes will make that much of a difference to be honest.  But I maybe wrong (has been know in the past...... quite alot!! lol).
Title: Undertrays.....??
Post by: RemarkLima on September 25, 2008, 10:43:44 PM
I\'d agree that the metal water pipes wouldn\'t matter really, not enough to notice.

But if you have a PFC then you can change the map so it doesn\'t enrich the mixture t colder temps (I think there\'s a 50C - 80C band and then above), it\'ll make it a bit rough while it\'s warming up but would certainly help the economy!

But also I\'d agree, just get a standard thermostat, the cooler ones are a bit of a bodge IMHO, unless you can map for the cooler temps it\'s not going to help. And ~85C is absolutely fine.
Title: Undertrays.....??
Post by: nikp on September 26, 2008, 12:19:20 AM
Quote from: RemarkLima;540370But also I\'d agree, just get a standard thermostat, the cooler ones are a bit of a bodge IMHO, unless you can map for the cooler temps it\'s not going to help. And ~85C is absolutely fine.

85 is cooler than my vauxhall calibra used to run!! :p They run at 95, so Fds actually run quite cool.
Title: Undertrays.....??
Post by: Dr-Rotor on September 26, 2008, 05:34:39 AM
Very interesting....I have an FMIC setup and my water temps go to 77 on the motor way and come back up to 85 in slower traffic.
 
I have a 65c thermostat. Its only just done this since I have changed the rad cap to a better Apexi one and I have no AST at all.
Title: Undertrays.....??
Post by: RemarkLima on September 26, 2008, 09:34:22 AM
Quote from: Dr-Rotor;540431Very interesting....I have an FMIC setup and my water temps go to 77 on the motor way and come back up to 85 in slower traffic.
 
I have a 65c thermostat. Its only just done this since I have changed the rad cap to a better Apexi one and I have no AST at all.

If you want to run the engine that cool (IIRC it\'s just add a bit more NOx to the exhaust), just make sure the cold start enrichment is setup to be lower than that otherwise you\'re just sticking in extra fuel for no real reason if you see what I mean?
Title: Undertrays.....??
Post by: Jono FD3 on September 26, 2008, 11:41:56 AM
Just orderd a new thermostat.... £6.50 deliverd from my local factors ;)
Any pics of where the stat is & how to remove??

Jono
Title: Undertrays.....??
Post by: nikp on September 26, 2008, 11:47:50 AM
Where the filler neck is: that assembly is the thermostat housing. Bolts to the water pump housing using 3 10mm bolts. Be careful with those, if they haven\'t come off for a while they might sieze. (One of mine had siezed first time i took it off.)
Title: Undertrays.....??
Post by: Jono FD3 on September 26, 2008, 02:47:00 PM
It had a new water pump just before I bought it in 05 so we should be OK I hope!!

Jono