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I am wondering how much aerodynamic advantage a deep “is” type airdam makes, compared to an “i” chin spoiler for an aluminum-bumpered car.
The factory '87 airdam is NLA, and is not too cheap even on eBay. Even then, the brackets are usually broken. And on the street, in a lowered car, it becomes a nice scraper.
At the speeds E30 runs, what am I giving up if I use a '87 i chin spoiler?
TIA,
Alex
A lot of cars run a custom lower chin spoiler made of ABS or other plastics. One of our 87s has an M-tecnik and the other a hard plastic (actually the stuff used at go-kart tracks as guard rails). Not sure there is much advantange of one vs. the other, aerodynamically. I do have an original 87 is spoiler as a spare and will use it if we need it in the future. I think Mike Osborne in the Ohio region runs one without any problems.
Ed
All three BeerTech cars run the 87’is airdam (cow catcher) if for no other reason than they look badass.
I wouldn’t worry too much about the factory mounting brackets, none of us use them.
JP
155MPH wrote:
[quote]All three BeerTech cars run the 87’is airdam (cow catcher) if for no other reason than they look badass.
I wouldn’t worry too much about the factory mounting brackets, none of us use them.
JP[/quote]
Zip ties and BTR Bumper Clips™ :whistle:
BeerTech Racing powered by awesome
scottmc wrote:
BeerTech Racing powered by awesome[/quote]
“powered by awesome”. Lol. Good one.
i have the IS “cow catcher” as well… for a cheaper route you can get the “e” cow catcher instead… they are identical with the exception of 2 slits in the front middle for “air flow”
for aero i doubt there is a huge difference…
I was going to install the “is” one on mine, but while mocking it up to fit found that it really isn’t significantly lower than the stock valance with the lip spoiler! Other than having provisions to install some brake ducts, I didn’t feel it was worth the hassle to install or keep installed.
But - isn’t that “air flow” allowing air into the oil cooler that is on the i that is not on the e? From an aerodynamics standpoint I wouldn’t care - from an oil cooling standpoint, I might break out the dremmel…
Can anyone post some pics of how the iS airdam attaches? I have an 87i and just picked up a used iS dam and want to put it on. Do i have to remove any pieces of the originial setup? Just bolt right to the bottom of the bumper or what?
I don’t have any pictures, and it would be way too much trouble to jack up the car to get some… But from memory the 87is air dam mounts to the metal valance under the bumper and to the front fenders. If your car has any of the air dam in place it has to come off.
I rather doubt that there’s any aero benefit from the chin spoiler at the speeds a SpecE30 is going to reach. I do know that I could not detect any difference running w/wo the spoiler at Road Atlanta. But I will say that an 87 with diving boards does look a lot better with the IS front air dam.
RacerDan, I should be able to get you some pics this week. I have 2 airdams off the car and all the broken mounting points to go with it
You need a total of 4 items to mount the front spoiler: A curved metal bar (which I’m currently selling 
) and 3 plastic brackets. The brackets help support the curved metal bar across its center, which nests below the metal bumper. Then, the cow catcher spoiler has two fasteners, one on each end near the wheel wells. These brackets bolt to the car, a tab on the spoiler tucks up under the black boot that goes over the bumper, and the rest of the air dam gets sandwiched between the curved bar and the bumper. I had a PDF that shows the installation, but I cannot find it. Perhaps it’s at work and I could attach it on Monday. Anyway, the three plastic brackets are very difficult to come by, because they get old and hard and then fracture.
Sasha
P.S. I’ve attached a picture of the curved metal bar. 
I wanted to bring this thread back because I will be attempting to remount my 87 is airdam this weekend. I have all the pieces, but all the plastic brackets that go between the curved metal bar and the sheet metal are busted or twisted. I am debating remaking them out of metal or going with a simpler rigged setup. Any pictures or advice would be appreciated.
I’ll see if I have some photos of when I mounted mine.
My car was missing the air dam when I bought it. I bought an '87 IS airdam from Al Taylor.
The mounting points are generally as follows: There is a piece of flat steel that runs along the bottom side of the bumper and mounts to the valence. The lip on the top of the air dam fits over this and the air dam hangs off it. There are three plastic brackets that mount to the front metal valence. The bottom edge of the air dam fits under these brackets and the dam bolts to them from the bottom side. Then there are some tabs on the ends of dam that fasten to the front fender.
Two of three brackets were broken on my car, so I got some aluminum angle and bent us some new ones myself. It took some trial and error to get them right, but now the air dam mounts solidly (at least until I hit something).
I FINALLY got my is airdam mounted this weekend. I was missing one of the metal brackets that it adhesived onto the inside used to connect to the fender. So I ripped the other one off and just drilled a hole in the bumper where the bracket was and used a couple bolts to mount each side of the airdam to the fender area. Then I drilled a couple holes in the bottom of the metal bumper and the top of the air dam near the center and used another couple bolts to hold it up. It seems really solid, and hopefully will stay on with a little contact as the bumper plastic is pretty thick and shouldn’t tear too easily.
I got some advice somewhere that worked out well. I drilled 4 holes in the bumper like you did and bolted it on. I drilled one hole on each side in front of the wheel well into the remaining metal valance also.
I was told to drill the same holes through the top of the bumper and use extra long (6-1/2"?)bolts. It is a lot easier to install this way (i take mine off to get it on the trailer). The long bolts drop in from the top of the bumper then your washers and lock washer and nuts go on the bottom. Easy to install by yourself without having to fiddle around through the bottom of the bumper and reaching your hand around and underneath. You need to buy an extra long drill bit to come up from the bottom and stay true to your lower bolts. Standard drill bits won’t reach up to the top of the bumper. I can send a pic if you need it.
dan
Randy87is wrote:
[quote]The mounting points are generally as follows: There is a piece of flat steel that runs along the bottom side of the bumper and mounts to the valence. The lip on the top of the air dam fits over this and the air dam hangs off it. There are three plastic brackets that mount to the front metal valence. The bottom edge of the air dam fits under these brackets and the dam bolts to them from the bottom side. Then there are some tabs on the ends of dam that fasten to the front fender.
Two of three brackets were broken on my car, so I got some aluminum angle and bent us some new ones myself. It took some trial and error to get them right, but now the air dam mounts solidly (at least until I hit something).[/quote]
This is a good approach. Once the air dam top lip is sitting on/in the little under-bumper shelf, fasten the air dam in place with some zipties in front and on the sides near the wheel wells. Then if the bumper takes a hard hit, the zip ties will break and the bumper is likely to come off intact.
I bought an early air dam but I didn’t have any mounting hardware. Unaware that the OEM mount is a little shelf, I fabbed a little aluminum shelf and fastened it to the underside of the bumper. The air dam is held in place by 6 zip ties.
The problem with bolting the air dam to the bumper is that when the air dam takes a big hit, it’s going to shred. Sooner or later you’re going to go into the grass and hit some rut that you never really noticed before. And the air dam will take a big whack.
Ranger wrote:
[quote]Randy87is wrote:
[quote]The mounting points are generally as follows: There is a piece of flat steel that runs along the bottom side of the bumper and mounts to the valence. The lip on the top of the air dam fits over this and the air dam hangs off it. There are three plastic brackets that mount to the front metal valence. The bottom edge of the air dam fits under these brackets and the dam bolts to them from the bottom side. Then there are some tabs on the ends of dam that fasten to the front fender.
Two of three brackets were broken on my car, so I got some aluminum angle and bent us some new ones myself. It took some trial and error to get them right, but now the air dam mounts solidly (at least until I hit something).[/quote]
This is a good approach. Once the bumper top lip is sitting in the little shelf, fasten it in place with some zipties. Then if the bumper takes a hard hit, the zip ties will break and the bumper is likely to come off intact.
I bought an early air dam but I didn’t have any mounting hardware. Unaware that the OEM mount is a little shelf, I fabbed a little aluminum shelf and fastened it to the underside of the bumper. The air dam is held in place by 6 zip ties.
The problem with bolting the air dam to the bumper is that when the air dam takes a big hit, it’s going to shred. Sooner or later you’re going to go into the grass and hit some rut that you never really noticed before. And the air dam will take a big whack.[/quote]
Oh so true… I’ve been thru some spoilers. I’m on my 4th. If I had been using the zip-tie method, I’d more than likely be on spoiler #2
RacerDan wrote:
The way I did the bolts are easily removable. I might also have to pull it each time I put it on the trailer. I will see how the bolts work, and if I destroy it then I will buy another one and maybe try the zip ties.
I bought this before I bought my late model…pretty sure it’s for an early model. Have the airdam and bracket if anyone is interested?