LingLing Posted May 15, 2012 Share Posted May 15, 2012 No speedo. Calculations say 190-200kph - I run a 4.55 diff ratio and 6th gear is overdriven by .869 (similar to most car's 5th gears). so when you rev is freed to 8000, you can get 220-230kph? Quote Link to comment Share on other sites More sharing options...
kpr Posted May 15, 2012 Share Posted May 15, 2012 what drive shaft are you running? single, 2 peice or some fancy custom shaft? i was having drama's with drive shaft vibration, last time i took the kp to puke. thought it was just a bad balance job. but further research says it might be spinning too fast for what it is. sounds like yours will be going roughly same speed once you get full rpm. i was getting to around 8000rpm in 5th, (t50 0.861) from memory it started getting its shake on at about 7000rpm nice mid race d1 btw Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 15, 2012 Author Share Posted May 15, 2012 It's a single piece driveshaft that I had made up - all balanced etc. It does get a vibration at high speed, but I' ho[ed that was either the dying axle wobbling around or the exhaust (which touches the gearbox crossmember). Is yours a single too? I used to have a similar vibration with a 2-piece that had a rough hanger bearing. Quote Link to comment Share on other sites More sharing options...
kpr Posted May 16, 2012 Share Posted May 16, 2012 using single piece also. will try dig up the site i was looking at the other day. had different sizes and materials and at what rpm harmonic vibration started Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 16, 2012 Author Share Posted May 16, 2012 Very interested in this. What dia is your tube and how long? Mine is just under 1m long and I think it's 3" dia. A quick bit of research says that 2-piece might be a better idea. Quote Link to comment Share on other sites More sharing options...
kpr Posted May 16, 2012 Share Posted May 16, 2012 mine is a bit over a meter from memory & is 3" dia. going by the chart below its probably getting up to the "critical" speed. yours being under a meter maybe ok? 2 piece sounds like a good way around it. since length looks to make a big difference. http://www.markwilliams.com/driveshafttech.aspx mine seems to be pretty heavy also, so probably isn't helping the cause. Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 16, 2012 Author Share Posted May 16, 2012 My driveshaft material is 992mm, so add in the extra for uni joints and it work out to just over a metre. I'm guessing those measurements are in inches? My late night maths brain says to work out driveshaft RPM in 5th gear you divide the engine RPM by the ratio (?). i.e. 8500 engine rpm / .869 = 9781 driveshaft rpm which is something like 240kph in my car. So the "critical" 8905 driveshaft rpm would be at 7750 engine rpm in 6th gear which is 222ish k on my current tyres and 215 on the smaller slicks. Hmm... Could be an issue there. I was doing 190ish over the weekend (revving to 6500-7kish) and I don't see it going too far over 200k's at Manfeild, but driveshafts make a big mess when they let go. What's your driveshaft whirr like? Different to what you can hear in the background of my vid? Quote Link to comment Share on other sites More sharing options...
kpr Posted May 16, 2012 Share Posted May 16, 2012 wasn't very loud,(well that i could hear over car) more a humming light vibration. would only happen towards end of back straight at puke. has been ages since had it on the track, but from memory it would come on fairly quickly when it started to happen. not like a switch. but i definitely remember staying under 7k in 5th for awhile so the noise didn't happen. till i gave up caring. yeh same deal here, not keen to have drive shaft exit at 200k! after reading up on it. thinking i'll rip it out and take to my balancing dude before next track attempt Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 16, 2012 Author Share Posted May 16, 2012 Just had a chat to my driveshaft man and he had some interesting points. The first was that it shouldn't be an issue with a 1m-ish shaft and he had a few theories to do with weight and balance. He's made smaller dia shafts with a thicker wall before to minimise the rotating mass and keep the strength - this should make it less likely to vibrate, but the sheet above says otherwise. He also said that UJ's with bigger crosses are more likely to stay true at high rpm, which I believe, and also wasn't a fan of me going to a 2-piece which is interesting. I'll take the shaft back to him this week and see what can be done with the UJ's - apparently there are nice ones that come from Auckland that are more likely to be a perfect fit. He said that repco ones often have play or flex from new. I'm a fan of listening to people locally who help me out, so will give the new UJ's a go and report back. Quote Link to comment Share on other sites More sharing options...
Archetype Posted May 22, 2012 Share Posted May 22, 2012 Just had a quick look at your project thread for the first time in a few weeks. You've been busy! Well done for getting it to this stage. Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 22, 2012 Author Share Posted May 22, 2012 Cheers man, it's been a lot of hard work . Have Howat engineering making me new axles and they're going to modify the diff so it'll take 28mm or 30mm splines, then re-harden the side gears. Hopefully that will be the last you'll hear about axle trouble from me. I'd like to put the housing on a bench and dial it up for straightness too - something tells me it might have a bend/warp in it. Quote Link to comment Share on other sites More sharing options...
Spencer Posted May 22, 2012 Share Posted May 22, 2012 So got a tune on that engine yet dude? gunna be awesome once you can dail some extra revs into it Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 23, 2012 Author Share Posted May 23, 2012 Not yet. Working on axle solutions and getting the driveshaft re-made with better uni's at the moment. Should be back on the dyno soon. Will be getting the side gears from the diff re-cut to 28mm, so will have the same size/spline axles as an F series from now on... I hope this solves my issues. Quote Link to comment Share on other sites More sharing options...
Boxtype Posted May 24, 2012 Share Posted May 24, 2012 Wow Quote Link to comment Share on other sites More sharing options...
LingLing Posted May 25, 2012 Share Posted May 25, 2012 What's your beams engine redline? 8500rpm is insane!! F20C is only 9000! Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 25, 2012 Author Share Posted May 25, 2012 Standard is something like 7800rpm redline. We'll see what mine will be after the next run on the dyno. 8500 is what I'd like to see, but it depends where the peak power ends up. Quote Link to comment Share on other sites More sharing options...
xsspeed Posted May 25, 2012 Share Posted May 25, 2012 Can you write up your shopping list of things done with engine? (I may have asked this previously but couldn't find it so apologies if I have) Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 25, 2012 Author Share Posted May 25, 2012 Nothing apart from a refresh, quads, ekengineering extractors and link G4 storm. Quote Link to comment Share on other sites More sharing options...
Spencer Posted May 25, 2012 Share Posted May 25, 2012 Surely it will be out of puff under 8000rpm, piston speeds are reaching pretty silly numbers at 8500 Quote Link to comment Share on other sites More sharing options...
Truenotch Posted May 25, 2012 Author Share Posted May 25, 2012 Like I said spence, we'll see what happens. I've seen dyno graphs that say otherwise but you never know. I want to rev to a minimum of 8k - which is what I always revved the gen3 and single beams to. Quote Link to comment Share on other sites More sharing options...
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