Louis M
|
| posted on 23/3/04 at 07:07 PM |
|
|
2nd Gen RX-7 as Donor
I would like to begin a project with a FC (2nd Generation RX-7) as a donor car. Now, I assume most of the information from the book is similar except
I believe the size of the chassis will be different. The problem is here: I would like to build my car with the chassis first, then buy the car and
put the engine in, etc. Anyway, is there a way that I can find out the specs of anyone who did an RX-7 build i.e. specs and updated sizes of the
chassis. Finally, how bad of an idea is it to start building without the car, because i would like to start without one, so if I lose interest,
I'm only down a couple hundred for materials and welder which I can resell.
|
|
|
|
|
JoelP
|
| posted on 23/3/04 at 07:55 PM |
|
|
pros and cons with that approach really, as you say it saves money if you abandon it, but its hard to know what size the gearbox is, for example.
some options may include going to a scrappy and taking measurements, or just buying a non runner if it was really cheap.
personally, id take the plunge and buy the car and just make sure you dont run out of motivation! or go the tried and tested bike route...
|
|
|
pbura
|
| posted on 23/3/04 at 08:56 PM |
|
|
I will be building with an '87 RX-7, and am at least familiar enough with it to tell you that you'll need two inches additional scuttle
height if you want to use stock EFI. Also, unless you want to use a rear axle from a 1st Gen, you'll be building IRS or de Dion rear end.
To see a nice build with a book-size frame and de Dion, see photo files of 'Odd Brit' at the Yahoo Locost NA mailing list:
http://autos.groups.yahoo.com/group/Locost_North_America
The builder (Jim Bolinger) is a nice guy and would probably be glad to answer any questions you may have.
I like the RX-7 as a single donor, but it's not really that Locost. Alternative fuel delivery can be expensive, as can the exhaust. Also, most
engines with 100,000 miles are in need of a rebuild.
I think if I were you I'd try to find a donor first, as ones with good engines are fairly scarce.
Good places to shop, besides your home town, are eBay and Parts Trader.
Best of luck,
Pete
Pete
|
|
|
Louis M
|
| posted on 23/3/04 at 09:51 PM |
|
|
quote:
am at least familiar enough with it to tell you that you'll need two inches additional scuttle height if you want to use stock EFI
That's the kind of information I was looking for  When people build their cars, they usually keep the specs of their chassis (i.e. where they
strayed) don't you think?
|
|
|
derf
|
| posted on 24/3/04 at 07:02 PM |
|
|
I'm going the build now, get car later route. My chasis is done, the rear half, behind the scuttle is fully welded, but the front 1/2 is not. I
also have not made the trans tunnel or the 3 engine bay rails (2 bottom 1 top), at least until I get the engine tranny. When those Items come I will
build the tunnel and properly brace the front end.
I did it that way because I did not have a donor. I lost out on a Supra because the guy was trying to sell me what he didnt own, I passed on a miata
because it was seized, and hopefully this weekend I will be picking up an rx7, 2nd gen.
Best I can tell if you get the whole car and are doing ALL the work yourself it shouldnt be too much more expensive than any other US rwd car. With
the 2nd gen I was planning on making a dedion rear suspension, but the car that I am getting comes with a real bad rear diff, so I might try to find a
solid rear from a 1st gen, or get one from another car
|
|
|
mranlet
|
| posted on 24/3/04 at 09:57 PM |
|
|
My advice is to get a good condition FC first before doing anything else. If you do lose interest, then at least you will have one of the funnest
cars ever made to toy around with!
-MR
|
|
|
Louis M
|
| posted on 24/3/04 at 11:28 PM |
|
|
quote:
Originally posted by derf
I'm going the build now, get car later route. My chasis is done, the rear half, behind the scuttle is fully welded, but the front 1/2 is not. I
also have not made the trans tunnel or the 3 engine bay rails (2 bottom 1 top), at least until I get the engine tranny. When those Items come I will
build the tunnel and properly brace the front end.
I did it that way because I did not have a donor. I lost out on a Supra because the guy was trying to sell me what he didnt own, I passed on a miata
because it was seized, and hopefully this weekend I will be picking up an rx7, 2nd gen.
Best I can tell if you get the whole car and are doing ALL the work yourself it shouldnt be too much more expensive than any other US rwd car. With
the 2nd gen I was planning on making a dedion rear suspension, but the car that I am getting comes with a real bad rear diff, so I might try to find a
solid rear from a 1st gen, or get one from another car
now how did you build the chassis? did you go straight from the book? i.e. cm for cm identical? if not, what was changed?
|
|
|
imull
|
| posted on 25/3/04 at 12:22 AM |
|
|
if you want basic dimensions such as track have a look at www.carfolio.com
a mine of information on there...
|
|
|
derf
|
| posted on 25/3/04 at 04:00 PM |
|
|
I did the chassis using the mcsorley standard chassis plans, I found them alot easier to work with than the book. I am using the book for everything
else, suspension etc...
I beleive that to use the FD rx7 I will need to modify the front cross rail, the one in front of the scuttle to accomidate moving the engine/tranny
farter to the rear. I will have no problem doing this as that part of the car is only tacked together. Worst case I will just wind up making a frame
around the rear of the motor on the Q rail.
|
|
|
mranlet
|
| posted on 25/3/04 at 06:02 PM |
|
|
You ought to position the motor and trans to best accomodate your shifting position - the motor itself is small enough that it could fit between the
foot compartments if nescessary.
Are either of you guys going to shorten the car at all with such a small motor? Is either rotary turbocharged?
-MR
|
|
|
Louis M
|
| posted on 25/3/04 at 08:07 PM |
|
|
quote:
Originally posted by derf
I did the chassis using the mcsorley standard chassis plans
so just follow step by step from that and i should be good?
|
|
|
Louis M
|
| posted on 25/3/04 at 08:12 PM |
|
|
should i just do the McSorley 7+442 and i should be good? better big than small
|
|
|
derf
|
| posted on 26/3/04 at 01:56 PM |
|
|
I never said That. I am supposed to get the car tommorow, but I wont be able to get it until next weekend, then I still have to dissassemble it. I did
however borrow an extra rotary and tranny that a freind has and put it over the chassis, and there is definatly room for play in the position of the
chassis. The rotary I am getting is not turbo.
Take a look here, it is a turbo rotary:
http://www.mindspring.com/~robmk2/
With the engine this far forward this is where the shifter is.
This engine bay looks cluttered, but remember it is a turbo version, and that adds all the asociated intake tubes. The chassis looks like a standard
width chassis, but there is a picture of the unfinished nose and it looks like it was cut in halfand glassed wider so I cant tell you for sure.
I'm a short guy (5'6" so I would like the shifter kinda far back. I like the size of the standard chassis, it would fit me for what
I want, a small light car with RWD, that I can take autocrossing or to the drag strip if I want.
|
|
|
pbura
|
| posted on 26/3/04 at 03:04 PM |
|
|
The car pictured was built oversize, about 10% as the builder described it, so it's not exactly a +442, but close. I believe it was his own
design.
I think a +4 width is a little tight; with 205 tires you wind up with only an inch of space for the rear trailing arms. I'm going +3 myself,
but wheel spacers would be OK if you don't mind a wider track..
The fellow I mentioned earlier, Jim B., built with a book-size chassis, but used side-draft carbs to get the height down.
Length is no issue as the engine is very short, only about 20". Adding a turbo might make you want a bit more room, as in the picture. BTW,
that's a J-spec twin turbo setup.
The shifter can be lengthened. It's already a remote-type design, so all that's needed is to get an extra whaddayacallit, shift rod (?)
and splice it onto the end of the existing rod. I was going to ask Jim for particulars on that, and also shortening the steering rack, when the time
comes.
Hope this helps!
Pete
Pete
|
|
|
GO
|
| posted on 26/3/04 at 03:53 PM |
|
|
I'm only using engine (13b) and box, everything else is the usual ford combination.
One thing I will mention is the width of the bellhousing. I think you'll want to make the very front of the tranny tunnel an inch or 2 wider. If
you do that then you'll be able to sit the engine well back in the chassis and you almost certainly wont need a stick extension ( )
Initially I'm planning on getting it running with the stock EFI, but am planning to go with either carbs or preferably throttle bodies and
MegaSquirt. All depends how desperately I want to get the thing on the road once its running!
I'm also looking at shortening the sump, which is gonna be a nightmare (right hand engine mount bolts through the middle of the sump). One
option is to replace the front cover with one from a 12a which gives you an engine mount across the front. Thats the next stage I'm looking at -
not looking forward to it!
|
|
|
derf
|
| posted on 26/3/04 at 04:12 PM |
|
|
Another rotary
And another
And here's the greates rotary locost page Ive found yet...
Here is what he had to say after a year of racing with a standard chassis:
ya that's it. Clearly the car was just too darn big. Really if 2 pieces are good then 4 pieces must be better.OK so let's take stock. I
went in for a little off the top and they cut the sides as well. That's 8" shorter and 4" narrower. For those of you paying
attention, the chassis is now book width, well starting half way back anyway and 4" shorter than a standard chassis. To do this with a 4"
wider chassis starting at the front of the scuttle I cut at an angle, to make it a straight shot to the back of the chassis from the front of the
scuttle back, instead of the rear of the scuttle back.
His page is here
|
|
|
derf
|
| posted on 26/3/04 at 04:18 PM |
|
|
Like i said I am waiting to get the engine before I do the trans tunnel. At this point I have done everything I think I can do to the car without a
donor. Last weekend I started to make a mold for the nose/hood (I want a 1 piece flip forward), but I cant even glass that until I have the final
height of the engine. I think I might wind up doing it anyway, and if I have a clearance problem I will just cut a hole and glass a bulge in the
hood.
This is my chassis as of 2 weeks ago. I have since welded the rear and added those 2 bent flat bar pieces on the side of the chassis.
[Edited on 26/3/04 by derf]
|
|
|
pbura
|
| posted on 26/3/04 at 04:53 PM |
|
|
That sweetvenom page is nice, hadn't seen it before
Here's another yet
Agreed that if you want to be competitive for autocross (something I don't care about), smaller is best.
Should mention also that the tranny tunnel can be narrower if you build with a de Dion rear. It can be even narrower if you form the tunnel from
sheet steel and eliminate the upper tubes (though I haven't seen anyone do this yet).
Edit: Removed unnecessary comments about holding off building tranny tunnel.
[Edited on 26/3/04 by pbura]
Pete
|
|
|
derf
|
| posted on 26/3/04 at 07:30 PM |
|
|
Sorry you cant see my chassis pic unless you sign up for imagestation (free picture hosting).
I am holding off on the tunnel because I want to make it as small as possible, and I wont be able todo that until I have the engine and tranny in
there.
|
|
|
pbura
|
| posted on 26/3/04 at 09:51 PM |
|
|
I signed up a while ago and peeked. Nice job!
Fast starters like you make slowpokes like me look sick
If you want to put a pic in a post: download it to your computer, then attach it to your post with the 'Attachment' field at the bottom of
the 'Post Reply' page. You can then delete the picture from your computer if you want.
Pete
|
|
|
Louis M
|
| posted on 23/6/04 at 05:12 AM |
|
|
quote:
Originally posted by derf
ya that's it. Clearly the car was just too darn big. Really if 2 pieces are good then 4 pieces must be better.OK so let's take stock. I
went in for a little off the top and they cut the sides as well. That's 8" shorter and 4" narrower. For those of you paying
attention, the chassis is now book width, well starting half way back anyway and 4" shorter than a standard chassis. To do this with a 4"
wider chassis starting at the front of the scuttle I cut at an angle, to make it a straight shot to the back of the chassis from the front of the
scuttle back, instead of the rear of the scuttle back.
His page is here
sorry for ressurecting a thread from the dead, but I may be back to a rotary instead of a 5.0 (a mustang would bastardize everything this car is
about)... anyway, if anyone could help me decifer what he said:
front half:
8" shorter
4" narrower
book height
back half
4" shorter (for a total of 12" shorter)
4" wider
book height
do i have that right? i am really confused about the shortness and also the width...
does anyone have the e-mail address of the guy who made the site?
|
|
|
pbura
|
| posted on 23/6/04 at 11:52 AM |
|
|
Ron P's original car was 4" wider and 4" longer than book, and is now book width and 4" shorter. Sorry, haven't got the
e-mail.
Pete
|
|
|
Louis M
|
| posted on 23/6/04 at 01:37 PM |
|
|
I assume that's 4" shorter from front to middle... right?
|
|
|
pbura
|
| posted on 23/6/04 at 02:16 PM |
|
|
I'm sure that he took at least some of the space out of the cockpit, if not all.
As I recall, he is less than average height, so you'll want to be careful with this. Strongly recommend that anyone building a car mock up the
seating area and dash, unless they're using a chassis design from a car that they've sat in.
Shortening the wheelbase will make the car more nimble in close quarters, but you lose some stability in the straights. Mr. P's car was
purpose-built for autocross, so this was a good trade-off for him.
Hope this helps!
Pete
Pete
|
|
|
Louis M
|
| posted on 23/6/04 at 05:02 PM |
|
|
so building a book chassis would be perfect if you're reletively tall... btw, what is the max height that the car allows right now?
|
|
|
