AMRAAM4

I recently got my car back from Ray at PFS where he installed a custom single turbo kit. I went with the Greddy 3-row FMIC and all that good jazz. Now that it is complete there is the fact that there is no undertray on the car and the stock does not work. I was curious if others could lend advice on the best course to take in order to make/get an undertray that will be acceptable, cost effective, and not an extreme hassle to make (if that is the road to take). More specifically, it would be great if some specific info could be given: what to use, where to get, good mounting points, etc.

Thanks

Scrub

iTrader: (25)

Is it the 99 spec front? If it is you could always buy the stock part for it from Japan...someone posted info on that not too long ago. If not you can always use a sheet of aluminum with some holes drilled through it for the stock mounting points. Thre's also two holes on each frame rail and two on the front subframe cross memeber. I doubt you'll be able to make anything but the stock undertray work with the two holes on each frame rail though, they're pretty high up.

I hope this helped Bob, Damian should be able to ad some sort of input to your question and probably answer better then I did.

-Dan

MR_Rick

iTrader: (7)

yeah I think Damina mihgt be able to help, I think he made one for his track car.

AMRAAM4

Oh yes, the front is the 99 spec Pettit. It also has a new front lip spoiler on it therefore there are no mounting holes currently in it (I believe that is where the undertray front side attaches).

ptrhahn

iTrader: (9)

Why won't the stock tray work? I've got a '99 nose and use it.

Scrub

iTrader: (25)

It will work..he will just have to drill through the fiberglass.

Edit: I thought you meant 99 spec stock one.

AMRAAM4

Dunno, it wasn't on when I took it in. And when I picked it up Ray said the stocker won't be able to work. My original plans were to buy a new one once the work was completed down there.

alberto_mg

AMRAAM,

I've actually been doing some research on that as well. I used DamonB's thread
https://www.rx7club.com/showthread.p...light=splitter as well as Damian's thread on the splitter/undertray combo and CCarlisi's experiences http://www.carlisiworld.com/ccarlisi/myweb3/photo1.htm as starting points

There are also a few good threads about ducting the radiator sides to ensure that the air coming in gets routed through the radiator as opposed to around the radiator.

I also have a Greddy 3 row FMIC running 99spec twins and a Koyo rad. Unlike you, I am able to use the stock undertray but I don't see a clean way of getting fresh air to the radiator in this combination. I find the car running hotter than I'd prefer this way on the street in this summer's heat. When I'm moving, it's not too bad but in traffic or slow speeds I think things could be improved.

My plan/idea is to create a undertray that will completely replace the stock one with a nice tight fit below and alongside the radiator and also replaces the R1 lip spoiler and will guide some air under the FMIC to the radiator. Kinda like a cross between DamonB's splitter and Ccarlisi's ducting under the FMIC.

Unlike Damian and DamonB's choice of material, I think this can be fabbed up using some plastic/acrylic/polycarbonate type of sheeting around 1/4" thick. This can be found pretty inexpensively from mcmaster carr. Go to mcmaster.com scroll all the way down to Raw Materials and Springs, select Plastics, select Sheets, Bars etc and check out their offerings.

My opinion is this thing is going to be exposed to all kinds of weather, and fluids such as oil, coolant, engine cleaner, scraped along steep driveways on occasion so there isn't much point to making it out of something that can bend (such as aluminum) or is expensive to replace.

I'll also be ducting the big gaping hole between the top of the radiator and the nose to keep air from going above and around the radiator.

Hopefully, I'll be done with that project in the next couple of months. Should be an interesting project.

David Beale

You just take the thread clips off the old front part and use them on the new front. If they are gone, buy more from a Mazda source. These slide on and have a threaded nut on them. Push them on so they align with the holes on the undertray and then drill a pilot hole in the new front. Remove the clip, and drill the hole to fit the bolt. I replaced the stock plastic clips at the rear (power plant frame) as they kept wearing out. I used "poprivit" style threaded inserts there. Drilled holes the correct dia. for the insert I chose, poped in the insert, and now just have two more bolts to remove to take off the undertray. It's very secure. My front chin spoiler is "C" shaped so the undertray sits inside it and doesn't really need the front bolts, but I fight and install a couple anyway (hard to get my fingers inside the "C" to insert and start the bolts).

If you really want to make your own from aluminum, you can still use the side mounting points (frame rails), you just have a bit of bending and fitting to do. Or you can just make and attatch some angles of aluminum to the new undertray in line with the direction the car travels to ridgidize it a bit so you don't need to bolt it to the frame rails.

If you do make a new one, you need to pay attention to the old design - re placement of the foam and vent routing.

7racer

here is one from Japan auction site...

maybe it will give u an idea..

AMRAAM4

Uhhhh boy....I think this is going to be more work than expected..LOL

damian

iTrader: (2)

mine will be for sale soon, here is the thread where you can follow the entire proccess that i already went through on this for my track car.

https://www.rx7club.com/showthread.p...amian+splitter

i suggest going through the entire thread as the progression of pictures is spread through out the thread. just pm me and i can help ya out or get you one of my design.

HedgeHog

Mine's not as slick as Damian's but I used a corrugated board to trace out the undetray and mounted it inside the bumper. That way, i'm not using the Dzus to hold up the tray as it's resting on the bumper. Additionally, I added a vent to allow the IC air to escape since I put a splitter in the v-mount. Hopefully, it won't create too much lift to screw up the handling.

damian

iTrader: (2)

Hedgehog, nice work looks really nice. but there is one major flaw in the design (and for what im trying to do its a MAJOR no no)

>>Additionally, I added a vent to allow the IC air to escape since I put a splitter in the v-mount. Hopefully, it won't create too much lift to screw up the handling.

with the vent you are doing 2 things that destroy the very function of the undertray:

1. introduce MORE air under the car
2. add turbulant air under the car

this will only decrease your total downforce to the front of the car and add more turbulent air under the entire car, decreasing downforce on the total car (front and rear)

I had a chance to take a close look at ALMS cars this week at RoadAmerica and they are try to do the exact opposite, they duct the air to the top of the car and the bootoms are totally sealed.

let me qualify my statement by adding that I am talking track only purpose like what I am doing for my track car, for a street car I think its very cool.

DamonB

So where do you think the air from the radiator normally goes in a v-mount setup? Same place it goes with a stock nose: Under the car...

For purpose designed and built racecars that's the way to go but you can't make something to even resemble that when the starting point is an FD. Aero on a true racecar is built as a package and you can't just pick and choose features as " that works", it's a complex system where many components rely on eachother in order to function correctly. If you have a flat bottom car you can make downforce just by controlling the rake of the chassis. The FD isn't going to see such gains; it's a completely different animal.

I bet an FD would make the most front downforce with nothing more than the lowest airdam on the nose you could possibly run and not worry at all about the underbody other than proper ducting for the heat exchangers.

GooRoo

iTrader: (4)

I want to second Damian's opinion. All track cars have splitters 1-2" off the ground and they have no openings underneath that add air. The point of the panels underneath is to smooth and speed air going under the car to create low pressure, and thus suck the car down to the road. The point of the sideskirts is to prevent as much air as possible from entering from the sides.

Introducing lots of nose air from the IC immediately underneath the car is going to create a significant amount of lift in the front at speed. (100+ mph) In my car (also with the GTC nose) the pressure from (well ducted) air in the nose at 80 is enough to lift my stock hood by 1/4-3/8ths of an inch. Since I don't have any undertray etc most of that air is then going under the car where I don't want it to go. I need to get a vented hood to prevent some of this asap. At least right now the air is getting dumped behind the wheels, so the lift is closer to the center of gravity. Lift in front of the wheels would be much worse.

On the street at normal speeds ( < 75 mph ) it probably won't be horrible. But I bet at 40-50mph+ you would be able to tell if it were possible to go back to back with and without the air going under the car.

I do like the front ducting design. The only thing I would add is that it might be useful to have a way to adjust the split between rad air and ic air. So for the track you might crank a little more into the rad, and the street you could get more to the IC. I plan on doing something similar with ducting for my ASP large style SMIC.

damian

iTrader: (2)

>>So where do you think the air from the radiator normally goes in a v-mount setup? Same place it goes with a stock nose: Under the car...

yeah, ur right, but that dosnt make it a good thing, and in fact it is not a good thing. im trying to make it better based on simple concepts, like get the air on top, not bottom, and get the air smooth not turbulent.

>>Aero on a true racecar is built as a package and you can't just pick and choose features as " that works", it's a complex system where many components rely on eachother in order to function correctly.

yes and no.... yes, its ture that on the racecars at the level of ALMS have huge amounts of R&D money spent on making a complete aero package that and undertray is just one component of.

but I disagree with you when you say that 'you cant pick and choose' certain elements of that entire aero package, especially when money is the biggest contraitn, I may not be able to afford a full under body mold that has been wind tunnel tested, but I sure can afford a wing and a splitter :-) and although they may not work at the level of the full package, they do help as seperate elements if designed/used properly.


>>The FD isn't going to see such gains; it's a completely different animal.

take an FD, no wing and no undertray/splitter, go through BIR turn one as fast as you can go, take the same FD and add a functional rear wing and functional undertray/splitter and then run BIR turn one again as fast as you can go....then you come and tell me the FD wont see much gains. I'll bet you will be minimum 5-10 mph faster in turn 1 with the wing/splitter combo from the added downforce.

>> bet an FD would make the most front downforce with nothing more than the lowest airdam on the nose you could possibly run and not worry at all about the underbody other than proper ducting for the heat exchangers.

usually im with ya on most stuff, but I disagree again, yes, you do want to do the best you can to minimize the air gettin under the car, one thing you can do that is effective is lower the bottom of the nose (airdam, plsitter, whatever) as far as you can, but from what I have learned its more important what you do with the air that ends up going under the car. ... in other words, I think you will get more benefit from a higher airdam (lets more air under) with properly tunneled/smoother airflow, than a lower airdam (lets less air under) but has a turbulent/non-directed airflow.

fritts

iTrader: (5)

[QUOTE=7racer]here is one from Japan auction site...

maybe it will give u an idea..





Now that's a duct. Any idea who sells them and how much they cost? Would mind having a single duct cover the entire bottom.

damian

iTrader: (2)

>>Now that's a duct.

its not a duct...its an undertray ;-p

fritts

iTrader: (5)

Bottom side of a radiator duct..

damian

iTrader: (2)

i was playin with ya fritts....

but just to clarify, the radiator ducting and the undertray should not be 'lumped' together. they are seperate needs, as the undertray would not duct a radiator properly on its own, and radiator ducting would not act as an undertray either. you could possibly mold them together into one part, but they are seperate needs if ya know what im sayin.

FromSilvia2seven

so damian would you build the same type spilter for a stock nose car with a r1 lip? i was thinking about making something along those lines for cooling the rad. but not the whole under side on the car. i take my car to 100+ speeds often and don't want to add lift.

damian

iTrader: (2)

umm, im confused FromSilvia2seven, did you not read my last post above yours? you are combining the things I just said you should not lump together?

are you saying you need radiator ducting (somthign I am also going to start selling) or you want an undertray? or both?

I have an entire thread on my radiator ducting project, but I dont want to steal this guys thread, so if you guys have more questions on my stuff then just pm me or post in my undertray.splitter thread or my rad ducting thread :-)

AMRAAM4

Alright, maybe someone can clarify things for me here. I was told an undertray was critical for cooling purposes. Now, I can see where an undertray would be critical for stability and aerodynamic purposes due to the giant hole in the engine bay now with a single turbo and FMIC. I also see where the stock undertray is critical for cooling in the stock location of the slanted down radiator.

My question is: with the radiator bent up now, and the FMIC in the nose, how is an undertray going to increase cooling effects? Isn't that solid tray across the bottom going to limit even more the air that has a chance to get up into the radiator?

GooRoo

iTrader: (4)

The stock 'undertray' has the lower radiator ducting built in, so you do not want to run without that. Maybe someone can post a picture.

When you go custom, often the rad ducting and the undertray/splitter are separate pieces. That's what Damian is saying.