Nubaroo battling to select gears...!

[Nubaroo]

OK so for the last 2 x months or so I have not had much luck at the races - I keep on missing 3rd gear on my speedshift and then get a bad 400m time or lose a 200m race. I went as far as to change the F18 gearbox I am running for a complete other one...still no luck. I reconditioned the selector bushes and linkages ....still no luck, still missing 3rd gear on a speedshift

Then earlier this week I find this...



This is the engine mount by the cambelt side of the motor. This mount was previously solid cast but obviously just gave in over time.

New one fitted - cant wait for the races this weekend

[exist3nce]

When I saw the topic, I thought that your F18 was finally giving out, but thats not the case! I'm not suprised that with a mount looking like that you would have trouble selecting gears, especially with the power and torque you have. Take some pics of how it looks when you fix it up

[Nubaroo]

Fitted the new mount but I still have trouble selecting 3rd gear when I shift at 7200RPM. However if I shift round 6900RPM I get 3rd gear OK???

Any ideas anybody????

[PrecisionBoost]

Perhaps a gas shock between the firewall and top of engine would help a little with respect to dampening the engine/gearbox movement.

Did you try realigning the gearbox linkage?

I'm not sure how it's done on the F18 but most of the other Getrag boxes have alignment holes

Realignment might not help if it's just 3rd gear, but it's hard to say.

[Nubaroo]

Perhaps a gas shock between the firewall and top of engine would help a little with respect to dampening the engine/gearbox movement.

Did you try realigning the gearbox linkage?

I'm not sure how it's done on the F18 but most of the other Getrag boxes have alignment holes

Realignment might not help if it's just 3rd gear, but it's hard to say.

Yip realigned the gear links - there is a pin at the back of the selector box and then you also alignthe 2 x holes on the gearshift. Gonna run the car on the dyno tomorrow and try and see what the engine movement is like. If there are no movement then I am really clueless

Only managed to run a 13.00 sec 400m today with this gearshift issue. My 60FT times came down from 2.3 secs to 2.0 secs using the full drag slicks and launch control, so I expected to see around 12.2 secs on the 400m but had to be satisfied with the 13.00

[Nubaroo]

OK so I found that the plastic tips on the 3rd gear selector was completely missing on the gearbox - anybody has any idea why this would affect the gearshifts at high RPM only???

Busy fitting a new(secondhand ) F18 box - should have the car running on the weekend, but I am sure all should be well. Also had the car on the Dyno on Monday just to check power and engine movement - with the car running with a slight missfire at 2.7bar boost we still managed a 369KW on the wheels reading, and the engine movement at this power is virtually nonexistint!!!. My tuner reckons if I can sort out the missfire I should see power in excess of 400KW. Also had the car weighed Monday - comes in at 1220KG`s without the driver ( me at 107KG`s) Gonna strip the doors of my spare daewoo, fit them with plexiglass, cut out the spare wheek well, replace the back window with plexiglass - my tuner reckons we could get the car at the 1000KG mark. This coupled with the 400KW on tap and the full drag slicks should see me in the low12`s high 11`s??

Chris - any ideas on what my times should be with a 400KW/1000KG car with half decent traction????

[PrecisionBoost]

Not sure why the F18 was acting the way it was, frankly I don't even know how it didn't blow up into a billion tiny pieces

As far as times, 1000Kg puts you in the same league as a completely stock Kadett so you could compare against them.

Honestly I think traction is going to be a hard thing to come by so it's really hard to say where your going to end up.

If your fitting a new F18 perhaps you should research various final drive ratios while you still have it out.

With all that power you could possibly put in a smaller final drive which would space the gears out slightly, decrease acceleration, increase top speed but it would reduce wheel spin.

I know that sounds crazy to say "decrease acceleration", but if you can't stop spinning that means your applying too much torque.

If lets say you have two cars identical in every way except the final drive ratio sitting on a drag strip.....

Car #1 has a 3.83 final drive ratio
Car #2 has a 4.11 final drive ratio

If both have perfect traction then Car #2 would most likely win because it accelerates faster.

However, if traction is not "perfect" it's possible that Car #2 will spin out where Car #1 does not.

So, in that case the car that does not spin out and just grabs and goes will win... which is to say Car #1 wins.

Also, Car #1 may require fewer shifts to get to the end of the track.

You might think 6 gears is better than 5 gears which is better than 4 gears but many high power drag cars only use 2 or 3 gears to get down the 1/4 mile.

Each time you shift you loose power for a fraction of a second.

If lets say it takes you 0.5 seconds to shift and you can do the 1/4 mile with one less shift because you have a wider gear ratio and a higher top end speed then quite simply your time will be a half second quicker.

If I can go the entire 1/4 mile in 2 gears due to massive power while you row through all 5 gears then I'm going to be way faster.... perhaps as much as 1.5s faster in the 1/4 mile.

Hopefully you get what I'm saying, most people will say to move the gear ratio the other way to accelerate quicker, but if you can't get traction then you have to move the other way.

The "best" ratio is the one that accelerates you forward without significant wheel spin

Cars that spin out will always be slower than the ones that "dig in" an fly out of the gate


In the end, there is no perfect magic ratio, it's a matter of just fooling around until you get the perfect combination for the weight/power/gearing of your car.

[Nubaroo]

Hi there Chris.

The final drive on the F18 box I am using is 3.94 - which allows me to cross the traps near the end of 4th gear around 6800 rpm. I am hoping that with the better traction I will be "using more " of the 400m for acceleration with the reduced wheel-spin, allowing me to get better times and a higher trap speed - does this make sense???

I am looking at upgrading the gearbox to an F23 cable shift one with a Quiaffe diff - although I have not broken a F18 box so far it should be giving me a better piece of mind

PS - the "new" F18 gearbox is selecting gears perfectly so I am eager to see the car run on the 2nd of May - will keep u guys posted

Thanks for the input - kind regards

hannes

[Nubaroo]

Had the car at the 200m drags last night - gears worked like a charm everytime Launch control sounds and works awesome Roll on 2 May 2010

[Nubaroo]

OK so I have stripped the doors of my spare daewoo - doors weighed around 30KG`s each before, and after stripping them and cutting them they are down to around 12KG`s each. Still have to fit the Polycarbonate windows on the doors and lightweight door covers, but I an sure they should not exceed 15KG`s each. Getting them resprayed this week to match the car. So that would be a weight saving of around 60KG`s in total - my tuner says I should actually FEEL the difference on acceleration?? Also cut out the spare wheel well - actually a waste of time as far as weight is concerned but apparently this will help with aerodynamics???

Chris have you any feedback/suggestions on the above???

[PrecisionBoost]

Yes, 60Kg should be noticeable and as far as the spare wheel area I'm not sure if it will help much but it certainly can't hurt.

One place you might want to consider if you haven't already is the stock radiator, aluminum aftermarket ones are way lighter.

How about the rear window, have you done anything with that?

[Nubaroo]

Yes, 60Kg should be noticeable and as far as the spare wheel area I'm not sure if it will help much but it certainly can't hurt.

One place you might want to consider if you haven't already is the stock radiator, aluminum aftermarket ones are way lighter.

How about the rear window, have you done anything with that?

Hi Chris.

Still running the stock radiator, but on the Daewoo it is a THIN flat one - very light in my opinion. will weigh the one in my spare car and let u know.

The windows in the car - all of them including the ones in the door - are normal glass. I weighed the one from the passenger door today - 2.4 kg`s, so if I just replace the ones in the doors I should save around 8kg`s?? Maybe not worth the trouble and expense??. I know Polycarbonate ones are lighter but I don't know - I just trust the popper glass ones better?????

[Nubaroo]

OK so 1 x F18 gearbox FUBAR......launched the car off the launch control at the drags today (boost guage showing around 2bar), Micky Tompsons dug in nicely, shifted to 2nd and again traction was good with very little wheelspin, shifted to 3rd gear and it was all over....car just revs and not accellerating - 3rd gear stripped

Gonna put in a F23 box from a Astra Turbo Coupe - -apparently as strong as the older F28 boxes, only it is cable shift and spares are readily available. can get a f23 boxd for R2700, then the cable shifter thingy is round R1500. Only problem is the TS-LSDiff wont fit in the F23, so I will have to get a Quiaffe which is R 8000 here in SA.

Anyway will get the F23 so long and run it with the MT drag slicks without a LS Diff - should be OK for now I guess????

[MMamdouh]

hey nubaroo....

i am having similar issues with second gear... slamming it in would induce a grind... some times this happens in third as well

driving gently will not show any of the above problems... my tranny oil is newly replaced and at the correct level (problem existed before oil change)

my clutch set is new as well as the slave cylinder... also tranny did that before the new parts

only issue that i remember was a leak from the gasket underneath the gear selector linkage on top of the tranny... i don't know how much oil i lost but i recon it is some 1 liter... can this be a problem were syncro gears are worn or damaged??

i also wanna add that mu pedal starts engaging relatively early than standard settings... can this be an issue as well???

sorry to hijack but it seems you got good experience with trannies and this is where i need help

MMamdouh

[Nubaroo]

Hi bud.

It seems as you say that the 2nd and 3rd gear sincros could be on their way out - the sincros cannot stop the gears in time on the high RPM shifts

The clutch engaging at a lower level could be a clutch slave cylinder that is on its way out, or it could also just be because of the new clutch setup - the goodies have to "wear in" and should come back to normal engage position.

Keep us updated

Kind regards

Hannes