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Anyone ever miss a shift?

Discussion in 'Ferrari Discussion (not model specific)' started by Bart, Nov 13, 2003.

  1. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    So what was your reason for asking Aircon??

    I hope you're not going to come in and see me with a "since you serviced my car....." complaint....!

    Love this internet spying game!

    The most likely thing to let go on a buzz is the valve train on a simple engine with only 2 large valves per cylinder, but with moden trends using multi (lightweight) valves, the springs now do less and less work. Valve float on multivalve Ferrari's is, I think, extinct. I recently did the second refresh on a 360 Challenge engine, which had had the inner spring missed out of one of the exhaust valves at the first refresh....with no ill effects after 5000km of hard racing and limiter abuse (Aussie celebrity Sam Newman).

    With the titanium conrods now used, the metallurgist always seem very vague as to how to life them. I simply crack test them at the first refresh, and if ok I'll replace them next time...

    I've seen two 360 engines that have had the small end of the rod open up at it's highest point. The N-GT car has lighter pistons, but rev's higher so loads are similar. The piston speeds are astronomical and the titanium simply cannot cope beyond a "still to be ascertained" limit.

    When the small end breaks...the remains of the rod are still connected to the crank and turn into a "helicopter axe" to the rest of the block......

    By the way, the Porsche Carrera cup out here is in a right pickle, with up to 15 clutches popping every meeting due to over revving or missed shifts. The springs in the pressure plates simply collapse and distort, causing huge vibrations at best, or complete failure at worst.
     
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  3. abarre

    abarre Formula Junior

    Jul 9, 2003
    295
    If you think about it, the two things in an engine that move "back and forth" (or reciprocate) are the pistons/rods and valves/tappets. Everything else rotates (crank/cams/etc...).

    If you overrev, the inertia of the valves can overcome the force of the valvesprings, causing them to float off the cam and "crash" back on the seats. Too much of this will break the valve off at the stem - quite quickly actually. If the piston doesn't catch it first, causing metal on metal impact - which usually bends and/or breaksvalves.

    Overrevving also causes the piston to move back and forth in the cylinder more quickly, causing it to experience higher acceleration at the ends. This can overstress a connecting rod, causing it to stretch and break. Pick up a 1-2 lb. object in your hand and swing it back and forth. See how much harder it is to do this quickly as your muscles have work harder to overcome the inertia.

    Interestingly, we used to dyno test Winston Cup motors and make cams for some of the teams. (Roush, Childress and a few others). We'd try to make as aggressive a cam lobe as we could (for better intake and exhaust flow) without "launching" the lifter off the lobe at the redline (around 8000). You could always make the valvesprings stronger, but this caused more friction between the lobe and the lifter, accelerating the wear - no roller lifters in Winston Cup back then (not sure now). We even broke a few cams near the gear end because the torsional friction was more than the brittle iron cam could withstand. If that wasn't bad enough, the stronger springs would work harden, causing them to break. Trick was to get a mix that would last just over 500 miles on Sunday.
     
  4. Aircon

    Aircon Eight Time F1 World Champ

    Jun 23, 2003
    87,383
    Melbourne, Australia
    Full Name:
    Peter
    I'm being accused of putting a rod through the block of a F2 car by doing a compression lock up. I didn't, but I was wondering if doing it would cause that damage. They use a golf engine.
     
  5. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    Aircon

    I'd ask to look over the teams engine history with regard to recent fluid changes, overhaul, hours, km and crack test results....if they can't produce them, they have no leg to stand on...apart from the one hanging out the side of the block.

    Warranty expires at pitlane exit on pretty much all cars. Any serious team/responsible owner should never go on to the track if they can't afford a total loss...anything less than total loss is a bonus.
     
  6. shmark

    shmark F1 Rookie

    Oct 31, 2003
    2,967
    Atlanta
    Full Name:
    Mark
    On my track car (brand that shall remain nameless) I have removed the detent springs in the interests of quicker shifting. It uses the same pattern as 5sp Ferraris with the 2-3 in the center plane. On my first outing at Road Atlanta after a complete rebuild including a new engine, I was coming into turn 10 flat out in 5th. I needed to get down to 3rd for the corner and I always go through all the gears, 5-4-3.

    Unfortunately I went 5-2-SH*T!

    The engine survived somehow and I will be installing a Robotek shifter in the near future.

    Slower shifts and running engine > fast shifts and a paperweight.

    Mark
     
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  8. RDS

    RDS Karting

    Nov 1, 2003
    66
    Elmwood Park, Il
    Check out the shift gate from Hill Engineering. The tines (the things between the slots) are tapered to cut down on the angle you have to move the gear selector horizontality for each shift. I haven't tried it but it looks interesting.
     
  9. PSk

    PSk F1 World Champ

    Nov 20, 2002
    17,673
    Tauranga, NZ
    Full Name:
    Pete
    Missing a gear ended my motorracing.

    Many of you guys have mentioned that overrevving a motor does not necessarily damage anything, and well you might be right, BUT I bet there are a few components that have been highly stressed if NOT cracked because of this.

    About 6 years ago I was testing my club racing sportscar thing that won the championship the season before ... we had made a few expensive suspension changes, etc. and were seeing a consistent 2 seconds a lap improvement :).

    Anyway, I was using a particular corner to set the camber, etc. and thus was only driving at around 80% for the rest of the track (which is a dangerous situation because while you are not trying, you are actually still carrying very similar to full race speeds) ... AND I MISSED A GEAR.

    Actually I missed the 3rd to 4th change. Did not put it in to 4th properly and thus nailed the throttle with her still in neutral ... now I was real quick, but a full race motor at 8500 rpm with the throttle buried revs really, really fast and it went right off the end of the rev counter (10000 rpm) and the motor sounded like an F1 motor for probably half a second. Now this motor sounded great anyway ... but well you get the picture.

    My father who was watching from the pit lane, even heard it. I lifted off and coasted and gave her a few little blips to see if she was alive, and then drove slowly around to the pits. She appeared to be 100% right and pulled just as hard, etc. Came into the pits and found all looked correct and then went on with the testing. Later on once home we checked valve clearances, etc. and all were spot on ...

    Well a month later and the first round of the that years series started. First race = win, second race = win with great lap times and everybody saying 'heh you are flying this year', etc.

    Third race started on pole and the motor did not feel right when I pulled up to the line ... but I was on pole, but I could feel a new minor vibration ... but I was on pole!. Anyway the racer in me pushed on and I was leading by a huge margin when BANG and the rear of the car locked up and I dumped the clutch and coasted off the track. Looked at the front of the engine and all the cam belts had come off and the front of the crank was pointing slight off. Once the engine had cooled you could grap the nose crank and wiggle it around. One broken crank.

    Pulled the motor down and you could see that the over rev, thanks to that missed gear, had cracked the crank and it was waiting to break.

    Estimate to fix was over $8000 as everything was broken, even the front main bearing cap!. I was still working hard to pay off the cost of last season and a very costly (3 motors in one year) season before that. I'm not a rich man like many of you Ferrari guys, but had been racing hard for 9 years and I loved it and every penny I earned went into racing :)

    I'd had enough and have never raced since ... thus make each gearshift stick when it counts, and I would suggest a full strip down if you ever have a big over rev like I did.

    Pete
     

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