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BATOOH
Topic Author
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Joined: Fri 01 Apr, 2011 8:23 pm

Re: Rear subframe - Extreme Weight reduction

Tue 28 May, 2019 7:26 am

This Post is boring for everyone except either a mechanically engineering minded GTO/Stealth Lover, Magnit or any clever person out there who races cars and Thinks Alot about the entire process. For the rest of you - you will be switching off after the first Para. Why have I posted here, somebody on this planet might just offer me some extra advice/thought or previous "Experience", which may help me. AND if i'm making a bad mistake somebody might double check me.

Ok I been thinkin about this for a while. How to accomplish a weight similar to a tube frame alternative (BY SEVERELY REDUCING THE WEIGHT OF THE STOCK SUBFRAME) but without the cost AND the potential for stress fracturing of the Tubing because the (tubing) designer didn't quite understand the stress loading points etc. And true to Magnit's advice it doesn't cost aftermarket costs, and I have a second spare subframe(s) anyway and the angle grinders and Hitachi drill/holesaws are for all intents and purposes - Free.

So when Mitsi designed the subframe and rear end there were no computers or modelling. There were no calculations. they did it on Need (to get a diff in the middle with the wheels attached etc), and Experience. Like all car manufacturers had done for 80 years prior. Now I can use that same motivation - Need and Experience. What I don't need is a subframe designed for an 1800kg monster fully laden with 4 Pax, and all their gear in the boot and fully laden with 75L of fuel and potential for lateral cornering forces encountered by an unexpected vertical road height change whilst doing 200 KM/h during a sweeping bend.

What we know is that the weight of the GTO is borne by the telescopic struts directly onto the rear wheel hub assemblies. Only when you jack up your GTO under the diff does the subframe take the weight of the car, and it does! The subframe is basically a cross X shape, with four arms secured to the monocoque chassis by four big stud bolts. So there are two triangles being connected together in the middle, this is extremely strong, as long as the four studs on the chassis don't move. The only weight being supported by the subframe is that of itself, the diff and D/S attached, minor ancillaries and maybe some of the control arms, (top bottom and trailing). The rear wheels support themselves. The chassis is supported via the rear struts. On this basis then, using the XYZ axis analogy, and looking from the front of the subframe toward the rear, the Y axis bracing (vertical walls of the subframe box) need not be engineered to support the weight of the vehicle, which it does! So fill it full of holes- not yet.

The subframe Box section is basically square/rectangular and shaped to accommodate the various connections. I have only had the subframe off the car once or twice to delete 4WS, install better diff support bushes and weld the trailing arm 4WS rubber bushing (at the front of the arm) up, so that it can't move at all. Mitsi looks as though they made this box by pressing the top section into a U shape and Spot welded it to a flat bottom plate with quite large flanges on the X axis either side of the box. Those flanges provide  X axis rigidty. And that's where I think the subframe does most of it's work. Cornering forces translate from the chassis into the subframe and onto the wheel linkages. There is Alot of point loading/force from the wheel linkages, mainly on the x axis. So this is where those wide flanges each side of the box section come in, they give the guts to the triangulation of the box sections. So I'm thinking I can't remove them. If I were to reduce the strength of the X axis plates on the box section I could seam weld the X axis flanges, along the same lines that seam welding a chassis assists the rigidity of a chassis for racing purposes. By doing that I can then reduce a little weight on the X axis plating. Until I get the subframe off the car again and have a really good look and maybe chuck a bore hole or two into it I can't speculate the main weight reduction areas. Further triangulation of the control arm positions is possible, but as I consider the Subframe over engineered - probably not necessary.

In my experience with Mitsi's box sectioned Front lateral subframe braces which I have already lightened (the long tension and Control arm mounting bracing points that attach the Main front Subframe to the small front rollstopper crossframe thing), there is internal strength gusseting spot welded in, so I'm expecting that.

In a nutshell Logic is telling me to reduce weight mainly in the Y axis areas of the Box section and seam weld the whole item to accommodate holes bored into the X axis (horizontal) faces. Also remove all unused connection points for 4WS etc. Rust proof as much as possible and weigh before and after. I wonder what will happen. I'm going to find out.
 
BATOOH
Topic Author
Posts: 906
Joined: Fri 01 Apr, 2011 8:23 pm

Re: GTO Track Project-Here we go.

Tue 28 May, 2019 8:18 am

magn1t wrote:
As I keep saying, it's not what you get told that's important, it's what you don't get told. I AGREE!
BTW your lift pump will be moving far too much fuel and would be more reliable running via a resistor.......volume, heat, noise , power consumption. IT'S JUST RECIRCULATING FUEL WITHOUT ANY REAL PRESSURE.


First of all, if you're racing it's pretty much compulsory to have a roll cage...another of those useless out of date rules which should really be revised. I LIKE THE ROLL CAGE!
Secondly, if you've seen a late model high performance car that's been rolled, crashed, T boned or otherwise, you'll understand my above statement. NO HAVEN'T SEEN ANY-WISH I HAD.
Thirdly, if you've examined the body construction of a 1960s pommy car like for example a Ford Escort, or maybe a Zephyr  you'd understand why roll cages are compulsory. They 're single skinned apart from the pillars and the sills and not much else. YES VERY FAMILIAR, DAD HAD A ZEPHYR AND I HAD AN ANGLIA.

So put all the above together, the reason these things are so heavy is the double and triple skin used for strength so they don't need a roll cage.
If you're fitting a roll cage anyway to comply with the BS rules you may as well go silly to the max and hack away as much of the second and third skins as you can, as well as the side intrusion bars in the doors....well you don't need any of that....do you?.....the roll cage is all you need. it'll hold it all together?...AND.....it'll fit in with the rules even if it's less safe than it was when it left the factory. So long as you're not planning on rolling down a mountainside you'll be OK ? I HAVE GAINED THAT 10KG WEIGHT REDUCTION OVER THE LAST 2 WEEKS BY REMOVING ALOT OF 2ND AND 3RD SKIN, ALTHOUGH I'VE BEEN CONSERVATIVE, NOT AGRESSIVE. I CAN ALWAYS HAVE A 2ND GO AT IT. CLOSE TO HOME MATE ROLLING DOWN MOUNTAINSIDES! I DON'T LIKE THAT LEFT BEND AT THE TOP OF THE LITTLE RIVER HILL CLIMB THAT OPENS THE ROAD ONTO A HIGH SPEED CURVING STRAIGHT WITH A NICE STEEP ROLL OFF OF ABOUT 300 METRES OFF TO THE RIGHT HAND SIDE!
The whole reason for all the rules is about safety?  yes?   no? YES, MOTORSPORT NZ ARE OBLIGATED TO PROTECT ME AND YOU. IAM NOW THANKFUL FOR THIS.

But why not?
No point in doing half a job..........if you want to loose weight, go all the way....go and out do everyone else? IT JUST SO HAPPENED THAT MY NEXT POST WAS ABOUT THIS SUBJECT, THANKS MATE!
 
magn1t
Posts: 2895
Joined: Mon 04 Feb, 2008 1:15 pm
Location: Upsetting the ricers on youtube 1magnit

Re: GTO Track Project-Here we go.

Tue 28 May, 2019 6:05 pm

Your above post about the subframe and the weight of the car held up by the springs.........it's not really about weight that the necessary strength is about...........it's all about torque. Drivetrain torque.

If your engine puts out say 500 ft lbs torque, you might have a 1st gear ratio of 4 to 1.
That will give 2000 ft lbs at the driveshaft.
Then once you go through the diff at 3.5 ish, that's 7000 fl lbs.

http://www.stealth316.com/2-gears.htm
OK so 1st gear overall is 12 and a bit....so 500 at the engine becomes 6000 at the wheels.
It's a bit hard to visualise 6000 ft lbs but we should all know what 80 on a torque wrench feels like?

edit......that's not quite right because a diff splits torque....55/45 front rear or something like that so the figures are really about half of what I said but still a lot..........and that's also WHY RWD conversions break......because you've doubled the torque to the rear end.
To ramble on a bit more.......Mr ricer comes along and says I'm going to do a RWD conversion.....no , it'll break. Ricer says........stop being negative.....no, the mathematics and the physics says you're doubling the torque to the rear end.........it's NOT being negative, it's being realistic. It's only negative if you've got no fecking idea what you're talking about. Wishful thinking.

Now think about a traditional front engine RWD car........the body twists to the point where you lift the left front wheel due to torque reaction ....equal and opposite forces etc.

No different from a FWD car where the engine rolls back (or fwds depending on orientation) on a launch and when the mounts are broken in the case of a GTO it breaks the transfer case because you're putting side loading on it.
Rubber mounts are used not just for noise and vibration but to absorb peak forces and it's the peak forces that break parts. Polyurethane mounts are stronger but still flexible.
Solid engine mounts as an example.......they're just for ricers....you're going to break more parts, not IF but WHEN.


So have another think on the rear subframe and think on how much torque it needs to handle without getting twisted and putting everything out of alignment and breaking parts.
The diff head, the transfer case and the driveshaft need to be straight at all times which means no side loading.
The torque reaction from the driveshaft will be lifting the body on one side and pushing it down on the other side.
The torque reaction from the driveshafts from the rear diff to the rear wheels will be lifting the front of the rear subframe and pushing the back of it down.
That's WHY it's X shaped.


In my own case I swapped a Falcon LSD into my Zephyr, got the pinion angle a bit wrong , it went OK for a few years but broke in the end (lasted about 12 years as a DD),it was inevitable really that it broke at the rear universal......which is WHY driveshaft safety loops are now compulsory for modded cars.

OK so the total weight of the rear subframe, diff etc?
Try comparing it to say the weight of a Ford 9 inch diff....it's not a lot different....if you were doing a 9 inch seriously you'd use a 4 link, not leaf springs.


Oh and if you're interested in seeing a high performance japper that's been crashed, rolled T boned or whatever.......I used to be a regular at Turners damaged car auctions.....that's where you get to have a look at them. I never went to buy crashed ones, just ones with blown engines but you get to see whatever you want to.
quote from barryboys.
Yes, yes, yes, that might be so, but you're clearly missing the bigger picture.....
4 intercoolers!!!!!!!!
Beat that!!!!
 
BATOOH
Topic Author
Posts: 906
Joined: Fri 01 Apr, 2011 8:23 pm

Re: Above...

Wed 29 May, 2019 6:20 pm

Mmmm Some good points. That fella in the USA that put a single turbo on his stealth and made 1000hp+ atw (1200 hp Crank they reckoned) said he had Air con and full interior so he was thick end of 1800kgs. He had about 850 ft lb Tq.

Then I was thinking F =M.a and if F stays same and Mass decreases then Acceleration increases. Only if Mass increases to the point where it inhibits movement does a large amount of Torque become a problem to the delivery mechanism. So for me Mass is the issue. It's becoming more obvious that the Top 5 I'm going for are really lightweight race cars. I know I can get the power issue sorted and I know I can pilot it.

So thats it I have a spare rear subframe and  I'm going to swiss cheese it. It will be interesting. The question I'm asking myself is this. Do I throw caution to the wind and do it to what I consider maximum weight reduction/can't live with any more holes, or do I do it the same as I have done the Chassis so far, Conservatively, therefore retaining the option of a second bite at it. I am erring to the Former as I think I can guess it right.
 
magn1t
Posts: 2895
Joined: Mon 04 Feb, 2008 1:15 pm
Location: Upsetting the ricers on youtube 1magnit

Re: GTO Track Project-Here we go.

Wed 29 May, 2019 10:26 pm

Do you have a link to that single turbo one?
It would have either blown up by now or caught fire...........a single turbo car will always be slower due to the narrower powerband....(been there, done that).
Because a bigger turbo hits boost later....it's the placebo effect when it finally hits.

More boost means more torque but you're NOT going to do it on pump fuel because it'll knock.
500 ft lbs at 1 bar would be about 250 at zero boost and about 750 at 2 bar...ignore BS dyno corrections.
A bigger engine gives more torque at zero boost as it also does WITH boost.....a 30% bigger engine will give 30% more torque if everything else is built to make it.
The formula F = MA only applies to a linear type problem but the general idea is exactly the same.
For an engine and / or car its torque = MA where torque = force times distance as it's a rotary motion.
Power is a totally irrelevant number as it's torque times RPM....like c*** size....for bragging rights only.
It's always torque that breaks parts or rather peak torque.......and average torque that wins races.

Reducing weight doesn't reduce the stresses caused by torque, it just makes the car faster.

Like you'll read on yank forums that carbon fibre driveshafts actually increase power.........they don't.....they reduce rotating mass (inertia) which increases acceleration.........but that's just sales and marketing tactics aimed at dumb cnuts that don't know anything.

So there's another option for you?

https://www.3si.org/forum/f35/cfds-184766/

25HP for free....well NOT free but still 25HP?


Got to love those 15+ year old posts from moronic americans...now that they've grown up a bit their opinions will have changed apart from the compulsive liar salesmen......the IPOs Ninjas and snakeskinners.

Quote:

[table][tr][td]Originally Posted by Imp Pwr Online
HP difference is 25HP to the wheels. That has been proven.
[/td]
[/tr]
[/table]
Quote:

[table][tr][td]Originally Posted by SnakeSkinner
With stock turbos you can do every mod you can think of ,spend $10K+ on bolt on's and a stock ZO-6 will still run away and hide from you from a roll (from a stop it's a different story). (like spending nearly $1000 on a CF drive shaft to pick up 8hp at the wheels)

Or you can up grade your turbos and wave byby

[/td]
[/tr]
[/table]
quote from barryboys.
Yes, yes, yes, that might be so, but you're clearly missing the bigger picture.....
4 intercoolers!!!!!!!!
Beat that!!!!
 
BATOOH
Topic Author
Posts: 906
Joined: Fri 01 Apr, 2011 8:23 pm

Re: Above.

Thu 30 May, 2019 12:07 pm

Here is a link.https://www.facebook.com/ThatRacingChannel/videos/baddest-3000gt-vr4-on-the-planet-1200hp-self-built-monster/402823820277086/

I am sure there are a couple of different vids of this guy. One is where just his car get featured, mainly at night by some motoring writer and the other is where he races some real powerful V8's from rolling starts. The nice thing is that he has done it all himself he says.

CFDS, No way. I like Box's suggestion I go NA DS as it's lighter than the TT one apparently. And my race car is now lighter so maybe it might stand the Tq. Speaking of lightening, I will post up a couple of pics of my 12kg bonnet. It's hoary and I did it myself in the absence of help from my nephew who said he was going to use the English Wheel but became to busy to do so. But it's half the weight of stock. I will also put in a shot of some core drilling! I've got to empty some storage out of my camera for this weekend so it's opportune to mess around and do this.

Hah Ha I was laughing about the posts of those yanks on the CFDS. I came across a yank post a few weeks ago where they said paint weighs alot and it's worth stripping it out to reduce weight, they said you know how much a pot of paint weighs eh! And then only days ago I saw another similar post from america saying more or less the same. OK Guys, the reason that paint is heavy in a can is that it's mostly solvent. If you don't think i'm right, take the lid off any can of paint and check the weight when it's dry.. ahhahha hahhah hahaha Awesome. Jesus wept.
 
BATOOH
Topic Author
Posts: 906
Joined: Fri 01 Apr, 2011 8:23 pm

Re: Racecar pics.

Thu 30 May, 2019 12:34 pm

Ok Bonnet is terrible but it's function over form! Cars a little dirty as I haven't washed it. AND I haven't cleaned up the core holes and painted them as yet. It's work in progress!
DSC02996.JPG
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DSC02999.JPG
DSC03000.JPG
You do not have the required permissions to view the files attached to this post.
 
BATOOH
Topic Author
Posts: 906
Joined: Fri 01 Apr, 2011 8:23 pm

Re: GTO Track Project-Engine mount s and weight reduction

Fri 05 Jul, 2019 9:17 am

Alloy Engine Mount - Searching for Information. Im working on the car and noticed just how heavy the passenger side engine mount is, the piece that bolts to the block. I have changed the upper part of that mount to the later gen alloy type for weight reduction, so that proves that alloy can take the forces involved but has anyone ever seen an alloy lower mount for the 6G72? In fact I will widen this to all 4 engine mounts on the Turbo 6G72. I have noticed alloy rollstopper mounts on some Mitsis, anyone know a direct bolt on alloy rollstopper front and rear? And I know the yanks make lower Trans mounts out of alloy.

It's turning into a bit of a mission this little winter upgrade job. I noticed the PS tensioner arm bearing was noisy and the same for the Alt idler pulley. You can easily change the bearing in the tensioner arm but it's not so easy to do the alt/aircon idler. The angular contact bearing is not easy to find at a good price. quoted $55 and $56 by NZ bearing outfits but was cheaper and a little more sane to buy an Alt idler from aussie for $42 freepost. And the tensioner arm. Why didn't they make that out of alloy??? Any alternatives out there??

The surprise package from this little venture was finding the rear turbo hanging on by one threaded stud - a bolt had dropped out completely and the nut off the other threaded stud had vanished. Oh and another wee surprise was that it looked like my nice rear Poly rollstopper was being toasted, ah so thats what those studs are on top of the rear exh manifold. No Heatshield... nil... so that was easy to fix. I had always wondered what those studs were, It was like that from when I bought the wreck. Haven't tackled the Brake master reposition yet gotta get this engine cleaned up. once thats done I will pull the Box off and check the clutch, then thats it power unit good to go.
 
magn1t
Posts: 2895
Joined: Mon 04 Feb, 2008 1:15 pm
Location: Upsetting the ricers on youtube 1magnit

Re: GTO Track Project-Here we go.

Fri 05 Jul, 2019 8:28 pm

The idlers for the alternator and aircon, they get dry and squeak. Apart from that, they're OK. The easy fix is to remove and soak in oil. Better still heat up and soak in melted grease, get rid of the excess afterwards. That used to be a good trick with bike chains.
The mount on the cambelt end of the engine..........it's the way it is for a reason. That same answer applies to lots of other things. Aluminium is often  too weak, too soft, different expansion rate from iron, you don't want bolts coming loose over time. Don't want threads stripping either.
On the other hand if you WERE to use aluminium, you'd need to redesign the part....like Mitsubishi did for the Diamante where it's mounted the other way round.

Likewise solid mounts whether aluminium or anything else is a stupid idea. Mounts are flexible to reduce the peak stresses. It's these peak loads and stresses which break parts when you launch or rather lunch it.
Think of a rubber hammer?
Low profile tyres....smash the rims in a pothole.
But they look pretty and you always get what you pay for?

Polyurethane is what gets used, it's still flexible but stronger than rubber.


Next you'll be wanting aluminium cam gears.....stock ones are cast iron....WHY?........Aluminium is unsuitable, it wears out too quick, the bolts come loose too.


Why are modified cars always broken?
quote from barryboys.
Yes, yes, yes, that might be so, but you're clearly missing the bigger picture.....
4 intercoolers!!!!!!!!
Beat that!!!!
 
User avatar
Chronos_c4
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Re: GTO Track Project-Here we go.

Tue 09 Jul, 2019 8:13 pm

I suppose that, given the application of your vehicle (not exactly going on public roads), the frequency of maintenance/inspection might warrant the risks that Steve mentioned.
Granted he hasn't exactly said NOT to use them, but I feel the fault lies in the youngens who thing aluminium-everything is going to make their car better.
E.g im sure the likes of F1/Nascar take theses stresses into consideration and hence the car is redesigned after 1 season

The pursuit of weight savings is a harsh game! hopefully it pays off for you
Image
Follow the progress: My rides thread HERE
 
BATOOH
Topic Author
Posts: 906
Joined: Fri 01 Apr, 2011 8:23 pm

Re: GTO Track Project-Here we go.

Thu 11 Jul, 2019 7:15 am

Chronos_c4 wrote:
The pursuit of weight savings is a harsh game! hopefully it pays off for you

It's critical. It is paying off. I'm less of an embarrassment to the GTO community if I can compete well. And I'm nearly there..
Anyway I swiss cheesed the Alternator bracket. It is really soft cast iron, easy to drill but not a flat surface in hell to drill against. The amazing thing is that I reckon I reduced that by at least a 1/3 in weight which is considerable. (I didn't weigh it before and after - who cares!). I also cheesed the cast iron engine mount on cambelt end. couldn't remove alot of weight but got some out of it, use the cut off wheel to cut corners off etc. It was slightly less carbon and slightly harder to drill. Also took to the transmission mount at other end as well. Repaint all items too so I'm not that half A'sd. Must be low 1300's now I'm really looking forward to going into the 12's. Goal weight is 1200kg ready to race. No real cost associated to weight reduc. I'm not going to replace Fuel tank, front and rear subframes or doors/bonnet/hatch etc with glass/carbon. paying for weight reduc is a mugs game.

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