Ultima Group C

Author
Discussion

GTRCLIVE

4,186 posts

282 months

Tuesday 10th February 2015
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Love it bud.... only thing I would comment on is the rear diffuser. I started to build a very up swept unit like that and was told by a few people that I trust that 2 high a angle change will stall the air very quickly. Best to be as gradual as possible. My first unit had a effective angle of about 14deg (not a constant as it was swept up in a curve) but have revised it down to about 8.5 degs now. To keep that lovely depth at the back of the diffuser close to what I had, I ended up bringing the starting point forward to the bulkhead. Its length is now over 1.7 meters, straight and kind of boring but will work way better... I'll dig out a pick..


GTRCLIVE

4,186 posts

282 months

Tuesday 10th February 2015
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Nice slow angle now....


CJulian

Original Poster:

69 posts

188 months

Tuesday 10th February 2015
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Hello my friend, I was anticipating your input and recall the conversation. All I will say in response, and please pardon me if I am not going to try and reply with a long engineering answer.

SAUBER DID IT.

Somehow Sauber was able to create thousands of pounds of down force with their tunnel system on the c9 and c11. Their system has an angle of ~18-20 degrees. I'm sure a closed tunnel is an entirely different animal from a diffuser. Either way, that is why I choose to copy their design and not reinvent the wheel. The two cars are not that far apart and in the end I'd rather have to take out down force to balance the car then try to add more. the other thing to note is that Sauber had a very Wing-Like surface on the front of both the c9 and c11 which I could add to the GTR down the road. I am not too fond of the look so for now we'll leave the front clip alone.

Chris

http://www.mulsannescorner.com/aerodatabasesauberc...


CJulian

Original Poster:

69 posts

188 months

Tuesday 10th February 2015
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I like it! I think you should look into the old GTP cars. Those cars had huge tunnels of many shapes and sizes.......

I don't recall seeing these CADD models. What are you going to charge me for the LS engine model? -Mine is very basic. I also have a Bus transaxle if you are interested.

Chris


chuntington101

5,733 posts

235 months

Tuesday 10th February 2015
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I always thought it was best to have flat, constant angle diffusers as there is less change of losing the air attached to it? Once you loose the attached air dose it not just become turbulent?

GTRCLIVE

4,186 posts

282 months

Tuesday 10th February 2015
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Hi Chris sign up to Grab Cad bud...

Rough G50 Gearbox but better than nothing..
http://grabcad.com/library/porsche-g50-space-model...

Very Good Engine Model...
https://grabcad.com/library/chevy-ls3-6-2l-1


Enjoy....


ROWDYRENAULT

1,270 posts

213 months

Tuesday 10th February 2015
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3750 cubic inches is over 16 gallons same as a stock Ultima. The only track time that this car will see is track days 30 minutes at a time so even at 4 mpg you have plenty of fuel. The advantage of the center tank is way to big to give up on the idea Chris gp back and take a harder look at the space between the back of the stock seats and the existing fire wall. I know you can get 16 gallon without impeding on your space for the pulleys because I have already done the sums awhile back. Come on Chris get that brilliant engineers brain engaged. Lee

CJulian

Original Poster:

69 posts

188 months

Tuesday 10th February 2015
quotequote all
Clive, Thanks for the link to the drivetrain comps. I already have that exact Transaxle and when measured against my actual G50/52 Box, the Turbo box is supersized in many directions. The LS3 looks to be a great set of files. Thank you.

Chris

CJulian

Original Poster:

69 posts

188 months

Tuesday 10th February 2015
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Here's the LS3 file (w/tweaks) in situ. I will someday tackle modeling the 180 Exhaust.

Thanks Clive






356Speedster

2,293 posts

230 months

Tuesday 10th February 2015
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Dribble, drool, slobber! So much want! I'm looking forwards to seeing how this develops....

anonymous-user

53 months

Tuesday 10th February 2015
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If you can't avoid "steep" effects tunnels, then you can slot the leading area and use a small electric fan to "activate" the duct (ie, suck out the boundary layer at the transition, to help keep the flow)


However, if you do manage to get significant rear downforce, you will soon find that the front of the car becomes a significant issue. Of course, the modern way is to use lower surface effects to limit lift without having to fit a conventional high drag rear wing. But you probably still want a massive wing because it looks cool! ;-)

GTRCLIVE

4,186 posts

282 months

Wednesday 11th February 2015
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Now that looks better...... BTW YHM....

Storer

5,024 posts

214 months

Friday 13th February 2015
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Man this looks cheap when you consider how much it costs to build an Ultima for track use.

http://racecarsdirect.com/listing/58321/aquila_cr1...


Paul

CJulian

Original Poster:

69 posts

188 months

Saturday 14th February 2015
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Yes it does. And the car has all the nice pieces. They must have left a zero off the price. Maybe you are buying the build plans??

Chris


chuntington101

5,733 posts

235 months

Saturday 14th February 2015
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The rear top wishbone mounting point looks a little fragile dose it not?

CJulian

Original Poster:

69 posts

188 months

Monday 16th February 2015
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Yes the rear suspension pickup points seem very fragile but on the track maybe that's all you need?? The transaxle is also a great find. I presume with the HP so low that the torque is also low, hence the small sequential box.


V8Dom

3,546 posts

201 months

Sunday 22nd February 2015
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some the things you are doing are simular to the Steve smith time attack Ultima..... no what a car that is..

macgtech

997 posts

158 months

Sunday 22nd February 2015
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Storer said:
No. He has a single tank but it sits in the l/h side pod I think.

Paul
Correct - we couldn't get the capacity we required (~100l) behind the seats without lengthening the chassis. That's changing though...

Storer

5,024 posts

214 months

Sunday 22nd February 2015
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Ooooooh.

Looking forward to some pictures ASAP.



Paul

ultimass

67 posts

158 months

Monday 23rd February 2015
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hi,

Reading this thread with interest as my Ultima already has many of these mods including an active rear wing.

This is the 3rd Ultima I have owned and is by far the best handling and quickest due to the modified suspension, all the aero changes and a stiffer chassis etc. - it does make a big difference particularly at high speed.

As soon as the weather is suitable, I will be taking some photo's as I am selling her in the near future.

Martin.