V-12 Engine into 308 Build, over on Grassroots | Page 71 | FerrariChat

V-12 Engine into 308 Build, over on Grassroots

Discussion in '308/328' started by dave80gtsi, Jan 16, 2019.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Just looking at you graph a little closer.....from about 7k up we nearly have the same engines. I just googled k24 and K20 wondering how close we are bore/stroke wise. I'm 86/78 and you 87/99 or 86/86 depending which engine. Looks like your intake valves are at least 1mm bigger....but close. Then of course I have 12 at 1 atm, you have 4 at 30ish psi boost (?) which is like 3 atm and 4x3 is 12 and we have about the same engine...regardless of how different they may look :p

    I just googled bore spacing, same 94mm. I thought I heard of honda heads on ferrari blocks and never considered it but it does look possible.
     
  2. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    I was too slow editing the last post, but it also occurred to me that my usable curve is about 3x yours. Mine build to be streetable (ish) needing wider power vs yours built for the street and only making power where you need it. But then I pay a weight penalty, not 3x I don't thing but probably 2x. I weighted my eng/trans full dressed at just under 700lbs and I'm vaguely recalling you weighting in at 350 before the turbo?

    Which all brings me back to me being surprised the nose of your car isn't bouncing up and down like mine does and has since at least 2005(?) when it was caught on video. Just the idea makes me a tad jealously if I'm being honest,.

    Have you measured the GC height in you car by any chance? Mine has to be higher by an inch or 2. I'm estimating 17" but hope to get a real number soon.
     
  3. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    #1753 mk e, May 16, 2024
    Last edited: May 16, 2024
    Found a difference! The drawings show 14x7 wheels front and 14x8 rear which are not right for production. I'm pretty sure 1976 stock the options were 14x6.5 and 14x7.5. My QV was 11mm offset 16x7 and 16x8 so they were thinking about these widths some years before implementing them it looks like. Also, the drawing shows track width at 1470 and the QV book says 1460 as I believe do all the 308 spec sheets, so a slight difference. That could just be wheel offset . The drawings I found could EASILY be mislabeled and are just production, or maybe more likely preproduction when they were still playing with specs.

    My CAD models are revised and now match the drawings pretty well I think . Stock roll centers look like F25, R 103mm, low the car 30mm and you have F-33 and rear 53mm....so the roll centers drop about double the amount you lower the car
     
    M.Burroughs likes this.
  4. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    I made a picture

    Image Unavailable, Please Login



    And also dusted off my braking spread sheet and added an acceleration tab and then used those numbers with what the spring spreadsheet spits and got some numbers, assuming I'm buying sticky tires.

    At full acceleration at the axles

    Front lift - 0.6"

    Rear squat - 0.45"

    Full braking

    Front drive = 0.86"

    Rear lift = 0.65"

    So total movement at the axles is 2.56" and total at the bumpers is 4.6". It looks and feels like its moving a lot because it frikin is!
     
    Ferraripilot and The TIG like this.
  5. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Design wise I'm still thinking about what I want to do. On acceleration, anti-squat means the rear doesn't drop, it doesn't mean the front doesn't lift. Good tires should get me a .8 or maybe .9g acceleration and that will move about 500lbs from the front the the rear. perfect anti-squat will push up in the rear by that 500lbs and the rear is stable, but up front 500lbs has come off the axle and that is over 1/3 what was there, and the springs will react to that and lift it about 0.6". Anti-forces are extra forces and they move the CG up or down, in this case up. I'm not so sure I care on accel, I can't think of a good reason why I should?



    When the brakes go on, about 740lbs shifts rear to front. this time though, because both the front and rear are active in braking, to have anti-drive in the front and anti- lift in the rear. The problem is though that in the rear the the available anti-lift is already set as the opposite of the anti-squat and is what it is and yields about 250lbs anti-lift not 740. If I put the full 740 anti drive in the front, there is a 500lb mismatch and the GC goes up coming into a corner, assuming that is why I was braking. The rear is going to lift .42", nothing I can do about that. The front wants to drive 0.86", killing 1/3 of that holds the CG constant but I'm kind of leaning toward killing 2/3 of it to kind of split the difference. Not sure really..........and remember the numbers at the bumpers are nearly double.
     
  6. M.Burroughs

    M.Burroughs Karting

    Dec 11, 2010
    151
    That's remarkably similar, all in all! The dyno I posted was a "mid boost" pull at 16PSI (low was ~13 at 640, and the "high boost" pull we ran was 20PSi at 810whp, but we ran out of octane).
     
  7. M.Burroughs

    M.Burroughs Karting

    Dec 11, 2010
    151
    If it makes you feel any better, my front end foes have issues bouncing up and down, but it's not a pitch problem so much as it seems to be a spring rate/damper issue. But its one of the main things I need to solve right now.

    I have not measured my CG height. I'll do that next time it's on the scales.
     
  8. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    So I'm thinking that the rear doesn't really scare me all that much. The lower inner are near the bottom of the frame, if I just raise them to be near the top of the frame rail, I think the roll center is basically right where it started.

    Image Unavailable, Please Login

    The anti squat....I could just rotate the hole assembly the 10.5 deg and call it done. It does mean the wheel base changes slightly with suspension travel...but not a lot. I may lay it out and see what it looks like before making more aggressive plans.
     
  9. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    I had it in my head you were running more boost than that, those are quite good numbers at those boost levels. I have a neighbor with mk4 supra making similar numbers, but that is 3.0 and I cold of sworn he was talking higher boost, I'll need to ask next time I see him. A stock is 308 engine need about 30psi for 650whp, good cams and head work maybe 20?

    My (simulator) numbers are pump gas but I don't have a dial to get more on race gas days, it just is what it is....stupid naturally aspirate :(.
     
  10. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    A lot of line so a little hard to see but the rear is twisted the 10.5deg for 100% anti-squat, which is about 33% anti-lift on braking. Also the lower mounts are moved to correct the roll center

    Up front the upper control arm stays put and the lower rotates almost 7 degrees and that puts the instant center on the 66% anti-drive line....but I've not yet sorted the front roll center. My basic plan is move the inner low mounts up to sort, fix my anti-dive angle accordingly and then just kind of hope I can get the rack moved to a happy place. Normally hope is not a plan, but I think I'm willing to make an exception just this once.

    Image Unavailable, Please Login
     
  11. M.Burroughs

    M.Burroughs Karting

    Dec 11, 2010
    151
    I designed and can send you weld-on brackets that go on the chassis that replicate the original control arm mounting position, but have a notch above and below that position for adjustment, if you'd like.
     
  12. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    I love the idea of adjustable, Can you send me a picture so I can figure out if its something that will help before I trouble you to sent a set? Post or
    [email protected]

    Playing around it looks like moving the lower A-arm mount up about 1/2 the drop amount returns the roll center to the original position, so I need about 15mm but then I want to add angle so need to lay that out and see where that puts the mounts.
     
  13. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Public service announcement.

    Over the past week I have seen quite a few articles, (to be fair old) books and videos showing the anti-dive point lines drawn to the CG, and it could be the CG, but that is a special case. In my mid-engine car its about where max braking is producing a 1g deceleration, I didn't play around to see if its the 1g point for all setups but it probably is I guess. 40-50 years ago 1g was all you could get from slicks so you see it in old race books and today good street tire are 1g so its a useful point.....but 200tw DOTs are generally more, maybe 1.2g? and slicks maybe 1.5g?. The point to use is the % total braking force X the wheelbase, on a line parallel to the ground at CG height.

    In my case I used 1.2g and got 66% on the front axle (from the spread sheet I made to set the brakes up), 0.66 x 2340 =1544 and that point is marked on the diagram I posted earlier. The anti-squat line connects to a point directly above the front axle because 100% of the torque is from the rear axle, and that is always true for rear drive, tires don't matter. If its awd then the torque split % times the wheel base just line for braking.

    Basically nobody uses 100% anti-dive, they set up for some lesser % so they don't actually get a nose that lifts when they use the CG instead of the correct point but I'm pretty sure they don't have the % anti-dive they maybe thought they did.
     
    Ferraripilot and JL350 like this.
  14. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    One additional question trying this adjustable mounts back to the question you hade about breaking stud axles.....what are you running for rear wheel carriers and are you still using double A-arms? My reason for asking is really about how ferrari attaches the A-arm to the wheel carrier, they use 4 bearings which means in the side view the A-arms MUST be parallel. I could modify, but that would reduce its ability to maintain toe....and toe is actually what I'm on about right now. Because the A-arm MUST outer pivots at parallel the inner also must or things will bind, bend, or break. Setting camber is shims, in/out not issue, but setting toe is done shimming to twist the lower A-arm which twists the carrier, which twists the upper, and it only works because the bushings are are flexible. If I install bearing it will break stuff unless I make at least 1 upper mount also adjustable or go to a different design at the wheel carrier. Sooooo...what did you do?
     
  15. M.Burroughs

    M.Burroughs Karting

    Dec 11, 2010
    151
    Let me hop on my other computer and I'll share the drawings of my mounts.

    To answer the above, I am still using double A-arms with factory pickup points on the chassis. The chassis-side geometry on my car is original (minus moving the forward upper RCA mount back a touch for engine clearance, but the effective geometry remains the same).

    My uprights are fabricated steel units that utilize C6 Corvette rear hubs on all four corners. I chose this because of the availability of very high quality SKF Race hubs with integrated wheelspeed sensors, and to have only one replacement "SKU" for all four hubs. I attach my A arms to this upright with an upper and lower ball joint, so the upright can steer. Then I just use a track rod from the upright to the chassis to control toe.
     
    mk e likes this.
  16. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Thanks. Ball joints fix the issue I'm worried about. I have another buddy using I can't recall which vette hub /bearing, I need to ask, but there was an available stub axle for the 911 (which is the 308) CV joint and he built steel carriers for them, but he kept the out bearings instead of your ball joint solution. Either way, both solutions are pretty bullet proof berating/hub I guess. And ball joints would mean I just need to angle the lower A-arm to get the anti-squat I'm after which is WAY easier.

    I've already gotten the "if you spend 1 more cent...." talk for the year and the head gaskets won't be cheap so building new wheel carries wasn't on my list. Replacing the bushings seemed cheap and is a safety issue....and it just doesn't make sense to buy new bushings and then install them in the wrong place, that would be a waste of good bushings and money.......
     
  17. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    And I just want to remind everyone....in the burnout video where the car is very clearly out of control, that is literally the very first time I opened the throttle for anything but a throttle blip so I had absolutely no idea what would happen. Its not that I'm a (always) horrible driver, its more that I kind of expect it it would just sort of pop or bog because ALL the tuning other than idle and free reving to 5 or 6k was a total guess. Nowhere on my list of possible outcomes was uncontrolled wheel spin, Now I feel better :p
     
  18. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
  19. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    I went out the the shop and picked up a little, I need to get the engine set together and set into the car to get weights but I just wasn't feeling it

    Mentally I've decided I'm making new stub axles so I need to rear A-arm mounts. I need a rotation, the bottom is easy but up top its welded. The needs to move up/back, the rear down/back....or looking at it maybe just move the rear back and let the front come up a bit more so I don't need to raise the rear as much and maybe also use a bolt-on fork like the lower for the toe adjust.

    Image Unavailable, Please Login

    Image Unavailable, Please Login



    Also I'm thinking about the rear roll high and how high it is compared to the front in the factory setup...F25, R103 is a huge difference and and cause the front outer corner to drip quite a bit. Also I remember really struggling with rear grip coming out of the corners, the height roll center doesn't help that either. So my new plan is leave the rear roll center right where it is down around 53mm, at least for now.
     
  20. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
  21. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Got an email for head gasket guy, they are in production! I guess the issue was he wasn't sure how to do the sealant silk screening but he came up with something and gaskets are a go!



    I've been playing around a little with and online program, Vsusp....the best I can tell the 308 suspension was always a hot mess. Up front looks fine at rest

    Image Unavailable, Please Login

    But it got super soft spring so hard brake and you have this

    Image Unavailable, Please Login

    Then try to throw it into a corner and WFT

    Image Unavailable, Please Login

    This basically says its going to want to plow like a mother because the rear roll center is up near 4" so basically all the corning load is on the outer front tire.....and I recall my first autoX with the car total stock there was no braking into the corner allowed.

    The car at its current ride height I have this

    Image Unavailable, Please Login

    the same as stock with brakes, hot mess

    Adjusting the bolt-on lower A-arm mounts frame mounts up about 16mm (there is a kit available from super performance) gets it here

    Image Unavailable, Please Login

    then brakes with about 60% anti-dive also baked into the lower A-arm mounts and roll controlled with stiffer springs and swat bar gets it here.

    Image Unavailable, Please Login

    not great but okish.



    In the rear it starts with a roll center up at 103mm, so when its lowered that actually makes the roll center much more rational

    Image Unavailable, Please Login

    then when you brake (with anti-squat/lift) and corner nothing very bad happens

    Image Unavailable, Please Login

    I want to play around a little more before I start cutting, particularly to see what can be done about the front roll center migration (moving right/left in corners) but I think its workable as is and I could very skip the rear anti squat and not be too bad.

    I did get the engine kind of slapped together so I can set it in for a weight....hopefully this week.
     
    Ferraripilot and The TIG like this.
  22. Newman

    Newman F1 World Champ
    Consultant Owner Professional Ferrari Technician

    Dec 26, 2001
    14,214
    Canada
    Full Name:
    Newman
    Like all car companies they're trying to save you from yourself and legal battles against the car company. If it plows you'll back off otherwise you'll be over-confident and quickly find yourself beyond your skill level and end up spinning. I lowered the upper control arm mounting points by 1" on our 67 Mustang to take out some of the built-in understeer, its called the Shelby drop and it made a huge difference.
     
    Rifledriver likes this.
  23. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Yes. The way the factory set it up you could remover the sway bars and car would still understeer....badly. Lowering the upper A-arm inner mounts is general right direction. It raises the front roll center, which then requires dropping the lower a-arm mount to get it be to reasonable....but it would make it match the stock rear better and with the ridiculously soft factory spring help pull out a ton of body roll.
    stock
    Image Unavailable, Please Login


    lowered
    Image Unavailable, Please Login Image Unavailable, Please Login
     
    Ferraripilot likes this.
  24. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,045
    The twilight zone
    Full Name:
    The Butcher
    Plutonium likes this.
  25. Newman

    Newman F1 World Champ
    Consultant Owner Professional Ferrari Technician

    Dec 26, 2001
    14,214
    Canada
    Full Name:
    Newman
    flyngti, The TIG and Ferraripilot like this.

Share This Page