200mph Sigma

[Scorpma82]

Hey guys,

I've toyed with the idea of building a (budget) purpose built track car
Having said that, i wanted to try and achieve a feat that (at least i'm aware of) has never been done before...

I'd like to build a purpose built salt racer out of a GJ,K or N Sigma sedan....and run it to a speed of 200mph!!

And to make it more difficult....i'm planning to do it with the original engine (obviously highly modified) AND, still have that engine Naturally Aspirated!!!!

The two things i'm concentrating on now are these....weight reduction, and "regaining" or "gaining back lost HP" (as opposed to just producing more)

To regain the lost HP I was thinking having the engine (most likely an A2) balanced (as well as bored out but making more HP),balance shaft removed, electric water pump, electric H2O pump, thicker wiring, running a Starion clutch with a lightened flywheel and a ballanced tailshaft.

Then to make the extra HP, I was thinking having the motor bored out, higher compression, ported and polished head, bigger valved with a 3 angle valve seat, MASSIVE cam, bigger carbies (if the costs stretch out that far...would go F/I)

for weight reduction, i was planning on this.....remove:
headlights (replaced with plastic covers)
horn
washer bottles, its motors and it hoses
charcoal canister and it's hoses
front wipers and it motor
O/S aerial
ALL of the interior..including, roof lining, A,B and C pillar trims, all lights, door skins (again..if funds stretch that far, i'll seal up fibreglass doors), all seats and seatbelts, dashboard and all it's components all guages (just have aftermarket water temp and oil pressure guages), carpets, sound deadener, glass all around the car, fibreglass panelling, rear lights (just have the outer skins glued on) rear bumper bar fibreglassed in, even all the wiring associated with all the removed components and (if permitted) even have the rear brakes removed..and all the brake lines associated with it and just run front brakes with a parachute. then for aerodynamics i was planning on running the skinniest tyre i could find with a high enough speed rating, run covers over the wheel arches, remove the mirrors and have the car running on its bump stops.....having its springs and shockers removed. and have the bottom of the car completely flat


Has this been done before?? If so, what was the result??? (If allowed in this setup) would the car reach 200mph??


Let me know what you think of it

[C_Fernance]

Weight isn't really the big issue when looking at going the fast across the salt. It only really effects acceleration. I'd be more worried about drag and aerodynamic efficiency. At those sort of speeds every exposed nut or even panel gaps on the front end can make a difference.

[Scorpma82]

well i've thought about having the front guards and bonnet all one piece.....but remember.....i still gotta "budget concious" fibreglassing i've heard is quite expensive.......i dont know anyone who can do it cheaply.....or if there is a DIY kit for fibreglassing panels...i'd do it myself........or if persex can be used....i've heard its lighter than fibreglass (dunno how true that is tho)

[amgis_obrut]

thats one big ask, 200mph in a car with an NA 4 cyl engine

a modern street bike needs 220hp to do 200mph the average car will need 500-650whp to go 200mph depending on the frontal area of the car

@ 200mph you'll need about 350hp just to overcome wind pressure and then theres rolling resistance that requires more power

[Scorpma82]

so with a car making close to 200hp atw (with fuel and driver im guessing it will weigh about 800kg'd or so).....what sort of speed would i expect to see......mind u....i havent actually mentioned all my tricks yet

[mstrrab1992]

add a v8 muahaha

[Cottees]

Another thing you have to consider when trying to get a top speed that just upping the power is not going to do it. Stock Sigmas can get to >112mph(180kmph), and would max out at around 124mph (200kmph) revving a 4G54 @ 6krpm and in 5th gear which is around 0.80:1. What I am trying to say is you'd have to be looking at changing the drive train to be able to do that kind of speeds. You could have a 650rwkW+ engine, but it still wont go above 200kmph with the wrong ratios.

Edit: I have done the math also that a low ratio diff of around 3.2:1 or so would allow the Sigmas to get to 150mph(250kmph) or so.

As an example, this is a KM132 with the top gear ratio of 0.856:1, diff ratio of 3.42:1 and 175/75 r14 wheels.

[C_Fernance]

I've been in a Sigma at 220kph. That was scary enough for me. They aren't really designed for those speeds. They wander around from side to side if there is even the slightest amount of play anywhere in the steering, the slightest bump unsettles the car, and so on. You would be wanting to rebuild the car from the ground up with the steering, suspension and so on designed especially for it.

[A112H]

I don't think I would like to be on the bump stops at 300kph. I don't think the stock steering or even geometry would be up to the task to be honest.
As C_Fernace said, the slightest bump will upset a Siggy over 200, I think running over an ant whilst on the bump stops at 300 would see you on ya lid.

[Scorpma82]

hmmmmmm, fair point....never actually thought of that

none the less, be great to see a Sigma do those sorts of speeds........at the very least....i could always use it a fun drag car at the friday night street drags (in melbourne)



i think in the end i'll stick with the hot street look...but its always nice to dream.....i still gotta get my break business off the ground yet

[geezer101]

I can see some custom LCA's, coil overs and rack and pinion being a must have. The crossmember will need to dropped to lower the car's centre of gravity. To get to this point will take a full tube space frame front end (at least!). What you'll end up with will be a Nascar in a sigma's pyjamas... It would be wild but you'll be giving the keys to it to your bank manager on weekends!

[A112H]

What you'll end up with will be a Nascar in a sigma's pyjamas...

Bit like how they call the V8 Supercars Holden and Ford, really the exact same car wearing different clothes

[Billsy]

youd want to have a good funeral plan if you attempt this. but i see it as an impossibility at you describe it

and without some SERIOUS custom gear ratios. youll need to get around 10,600 rpm to get to that speed in 5th with a conventional manual setup

ive wound my old sig out to the 6500 limiter in 5th and clocked it on a perfect 'private' road, and its not something youd want to take further.
the aerodynamics of the cars arent built for this. it was starting to float. so i dont want to think what would happen if you added another 3rd onto it without some serious aero attention and pre testing.
and NA wont even come close to it without some good shots of NOS as the power required is far from near what your talking about.

/2c

[cheaterparts]

Hey guys,

I've toyed with the idea of building a (budget) purpose built track car

I'd like to build a purpose built salt racer out of a GJ,K or N Sigma sedan....and run it to a speed of 200mph!!

To regain the lost HP I was thinking having the engine (most likely an A2) balanced (as well as bored out but making more HP),balance shaft removed, electric water pump, electric H2O pump, thicker wiring, running a Starion clutch with a lightened flywheel and a ballanced tailshaft.

Then to make the extra HP, I was thinking having the motor bored out, higher compression, ported and polished head, bigger valved with a 3 angle valve seat, MASSIVE cam, bigger carbies (if the costs stretch out that far...would go F/I)

Let me know what you think of it

budget and track car arn't 2 words that go together well

run it to a speed of 200mph!! - aim for a bit over 130 mph as a NA car and you will be closer to the money

beleve it or not the FI will work out cheaper than carbs or have you priced big webers you will need 55 mm webers

having played with 4g54s for a while in a track car I can tell you there is good power to be made NA just nowhere near enough to run 200 mph as I said about 130 mph will see you out the next 70 mph will take 3 times the hp it took to get to 130

so to let you Know what I think - keep dreaming




I'll try to list it as its last and most up to date configuration

astron 1 4G54 block up 0.060" flat top piston zero decked with the pistons releaved on the inlet side for valve clearance
std rods polished and shot peaned and balanced fitted with ARP bolts ( resized of cause )
crank reduced in weight and polished - balanced of cause
custom made crank scraper - balance shaft removed
custom made sump with trap door baffles , larger volume and modifide so the engine could be moved back in the engine bay
the engine sits 65 mm back in the engine bay
it also runs a very light custom made billet flywheel

the head is astron 2 and started its life on a magna it had 3.5 mm machined off the face to lift the comp - there has been some port work ,the guides were bulleted ( tapered where they go into the port ) the valve seats were opened up to the outer edge of the valve - the seats were 3 angle cut and the valve were back cut
double valve springs and the cam run about 300 degs on the inlet and 310 degs on exhuast
to dail the cam in I fitted a redrilled cam gear



the custom header is a 4 into 1 system using 1 3/4 tube with mandel bends and straight sections tig welded up and all pipes are with in 3 mm in lenth of each other and run into a 2.5" system



induction twin DCOE 13 webers with custom made 41 mm chokes and no air cleaners
the ignition curve was modifide for less advance in the curve and runs 30 deg total timing

this configuration got 119.5 Kw atw @ 6100 rpm with a very wide spead of power on the track it pulls out of slpw corners from around 2000 rpm with the cam coming on at 3000 to max at 6100 but I run the engine to 7200 at times to save a gear change



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the engine needs a rebuild now and the future mods will be a lighter knife edged crank with a new crank scaper
a light billet flywheel and a much lighter clutch
a M9 magna head with OS SS valves and more compression
50 mm quad TBs
maybe a larger set of headers with 1 7/8 "tube
and a larger cam grind