FD Sports Sedan - Mazda RX7 with Honda K24 turbo

[MrBoost]

Hi All,

We are building a new car to run in the Kerrick national Sports Sedan series.
I used to run a Fiat sports sedan and then a Calibra with a v6 twin turbo but my dream had always been
to run a 4 cylinder turbo car and to try and win the title against the big 6L v8's.... so here i am spending
all my time and money!

Basic's

The car uses a series 6 Mazda Rx7 FD body shell. It is wider by 100mm both sides than standard. The shell
including doors, roof, sills, front and rear clips etc weighs in at only 65kgs. The top of the roof at its
finished sitting height is just over a metre off the ground.

car on jig.jpg
IMAG1126.jpg


The chassis is a tube frame chassis utilizing push rod suspension. We have designed the chassis in cad and
have put it through fea analysis. The results in cad are quite good, it will be interesting to see how they
compare to the real world tests we will perform. The chassis around the driver has been designed a little
heavy as i wanted to make sure im safe. The engine sits as far back as we could get it. I can reach out
from my seat and place my fingers in the back of the rocker cover.

1913243_659615077418308_959664752_o.jpg
wing on chassis.jpg

Now for the engine which is what i guess you guys will care most about
we decided to use is the Honda K24. We will be turbocharging the engine and power plans are
around 700 RELIABLE horsepower. The engine needs to be run hard for 25-30 mins at a time which is our
race lengths so there will be no 1000bhp time attack style turbo's going on it as it would blow up quite quickly
having to run those kinds of durations.
We are doing 2 engine's, the first is a little bit 'cheaper' option so that we can run it and test it and if we push the
limit too far it wont be such a bad cost to deal with. In saying that it is still a very strong engine

Honda K24 block with oil squirters
Sleeved and deck has been closed and o-rings
The K20 Head has been ported and machined to suit the k24 with supertech inconel valves, supertech springs, retainers
new bronze guides, machined valve locks and all new seals etc
Billet camshafts
Toda adjustable cam gear on exhaust
Cosworth head gasket
Mahle forged piston
Manley Rods
AC bearings
L19 head studs
Balanced and treated standard crank



The driveline consists of a Hewland SL 6 speed sequential transaxle. It is rated for 600ft/lbs of endurance racing
and allows us to quite quickly change ratio's at the track if need be.
1278180_584802194899597_645743444_n.jpg

Brakes are 375mm rotors at the front with 6 pot AP calipers, the rear is 343mm rotors with 4 pot performance friction
calipers. We are using a tilton pedal set.

We are currently in the process of machining the suspension pieces and also putting the engine together.... ALOT of work ahead

[butter]

Welcome to ClubITR. First off, WOW! This is absolutely huge!

I'm sure many of us are very intrigued with your build, especially some of the RX7 owners on here. Looking at the CAD picture, it's really interesting to see how the engine mounts up to the transmission.

Looking forward to the updates! Thanks for sharing this with us.

[dnapol]

This certainly looks like it could be the BEST build I've ever seen. Eager to see updates, keep up the good work!

[eskimo_firefighter]

Amazing build, thanks for sharing this with us. Will be following this one very closely!

[MrBoost]

Thanks guys appreciate the comments

butter there is about 500mm between the engine and the gearbox (we havent finalised engine position yet)
Off the front of the transmission there is a spline which has a flange that bolts to it that then has a cv type joint.
We then will have a shaft from the cv joint to anoher cv joint which is bolted to the crankshaft. Although we are
still contemplating uni joints etc depending on our end angle.
The flywheel and clutch is built inside that front housing on the transaxle so the tailshaft will spin at engine speed.

20140213_183600.jpg
20140213_183114.jpg

this picture was when we just had a dummy piece of steel in there to get an idea on how close i could move my seat
to the centre of the car before being too close.

the starter motor is also housed within the transaxle so i will be cutting the starter motor mounting point off the engine
as it currently hits my knee.

[ievaq8]

very nice work...
looking forward to following this...
me and my bro have done and use as a drift car on the track a K20a matched to a s2000 gear box, gt3076r in a s13 silvia...

[butter]

I can't picture how you guys intend on making this work, as this is so crazy. (crazy good!)

All I can see is an engine mounted next to your seat, and the intake manifold where the steering wheel would be. Then theres piping? intercooler? And and .. *my brain hurts* The amount of work put so far, and coming ahead is mind blogging.

I'm guessing you guys are at this full time as apart of a workshop?

Whats your ETA of this being completed?

[plAythiNG]

Coolbuild

[tinkerbell]

just reading the sports sedans website, your build embodies the:

"The Sports Sedans category is one where freedom of expression is regarded as a legitimate means to an end - and that end is performance, and lots of it."

philosphy

http://www.sportssedans.com.au/index.php?page=technical

[MrBoost]

Haha its not as bad as it seem's.....i think
Yes we do have a problem with inlet manifold. We are going to use a skunk2 ultra race to start with. We have it ported to suit
our cylinder head. It will be heading over here with the cylinder head from the usa in a few weeks.
We may have to lean the engine over a little to help with steering wheel clearance. The bigger problem is actually the gear lever
as the downshifts may see my hand getting very close to the engine cover. All things yet to be finalised but it WILL all work out
i am sure of that.

No def not a full time shop thing, my father ran a mechanical workshop for 30 years and then when he shut it down we moved all
his stuff into my shed so alot of work goes on in there. The car is currently at his old apprentices workshop which is a roll cage
manufacturing place AGI engineering. Perfect for us as he has all the right tools and equipment for bending bars etc. The jig the car
has been made on has made it so that all the bar work is within .5 of a mm of where it should be. The chassis was welded in special
sequences to make sure it didnt 'pull' or warp during welding. This is important to make sure all the suspension points are in the right
position to begin with.
The build time has been blown way out lately because our category sports sedans is under going rule changes. This means we have
had to stop progress for months now waiting on the new rules as they will largely change the direction of a few things in the car.
It is still moving along just very slowly at the moment. Like i didnt need the real engine for a while as a dummy engine would suffice
but we have just done it now while waiting for other things.

ievaq8 sounds like a fun little machine, i cant see how people go past the honda engine. I did ALOT of research before deciding on
the engine for this car. originally it was going to be the mitsu 4g63 but after talking to some heavy hitters like the lead engineer
at cosworth and all the top time attack teams we found that they will never work unless you have a billet head and block. They
are good for short stints but once heat gets in them they are useless. We then went onto using a bmw engine out of the old m3's
/ formula one cars and if the honda fails this is the engine we will revert to. Its just getting hard to get parts for them.

haha sports sedan philosphy is in my blood. no better category in oz that actually races door to door

[ChargeR]

Welcome, and thanks for sharing your build! Will be following closely.

The starter motor is also housed within the transaxle so i will be cutting the starter motor mounting point off the engine
as it currently hits my knee.

Probably the first time that's been an issue for someone with a K motor .