260Z Project - 260Z GT-R

[ryn004]

She looks fantastic!

 

[STEVE BURNS]

Wow, all that for minor details, looks like its worth it though.


bmw service

????? above is this relevant or just bloody taking the urine

 

[morbias]

It's spam Steve

 

[STEVE BURNS]

it is not now bye bye

 

[Ian]

Made 475hp @ 1.5 bar, she had more left but we were having problems with the tyres starting to spin up on the dyno, should be enough power anyhow, at least for a while. Interestingly enough traction isn't an issue on the road, she just grips and goes, yet to try full boost in first gear though but in low boost first gear it just goes.

Made around 485lb/ft as well although I need to check the numbers when I'm back on Thursday for some minor tweaks on the road and setting up fail safes and knock control.

Main thing is the engine and turbo are unstressed and its very smooth. There were many headaches to sort but I'll mention these some other day.



Getting a problem with vibration through the steering wheel, all arms and joints seem rock solid and I just had my wheels rebalanced today to no avail, anybody got some ideas? Not looking forward to driving 400miles with it like that.

 

[Wyn]

Well done, now the fun begins

I take it you are using spigot rings on them wheels as that would be favourite ?

 

[Ian]

Well done, now the fun begins

And fun it is Would be more fun without the wobble though.

I take it you are using spigot rings on them wheels as that would be favourite?

No Wyn I'm not, I thought the Z wheels didn't rely on the hubs for centreing thought it was just the nuts that served that purpose, or is that just the rears?

I have 10mm spacers on the front, I'll take these off and see if that's the cause.

 

[SKiddell]

Stunning install Ian, cudos sir

Nice power and torque figures as well, should make a very enjoyable car to drive.

Out of interest what rear tyres (and size) are you using, plus braking setup

 

[Ian]

Thanks,

It is indeed very enjoyable to drive, first few times trying out some full power runs I was smiling and laughing to myself like a mad man.

All the setup is in this thread somewhere, but to save you looking:

Tyres are R1R's all round, 225/45/16. Brakes are 12.2" wilwoods front, custom 12" mustang GT setup rear. Braking is very good so no worries there.

 

[Alphabettispaghetti]

Lots of numbers again!

Have you got a pic of the power and torque curve? Sounds like its nice and progressive.

 

[Ian]

I will get a power and torque graph on Wednesday, it is indeed an nice smoothe power delivery with no big traction breaking spikes.

 

[Wyn]

And fun it is Would be more fun without the wobble though.


No Wyn I'm not, I thought the Z wheels didn't rely on the hubs for centreing thought it was just the nuts that served that purpose, or is that just the rears?

I have 10mm spacers on the front, I'll take these off and see if that's the cause.

My bet is on that setup. As you say remove them spacers and let the hub nose centre the wheel true.
Or if that fails try spigot rings if the wheel centres are too large
Think that's your answer

 

[johnymd]

The 240/260 front hubs have a tapered rough cast surface that the wheel cannot accurately centre on. It was never designed to do so. You can have a aflat machined on the standard hub to allow the use of spigot rings and this would be the ideal approach. I had to remove material from the inside of my rota's just to get them to go on the hub. It's always worth checking that the wheels are touching the hub mounting face and not held away by the hub tapper. This is a very common problem but not that well documented. If you run a 5 mm spacer then you won't have this problem. On my wheels, because I've ground away a small amount of material from the inside of the wheel and its not a perfect machined surface so I have to make sure the wheel balancer knows this and centres the wheel by clamping on the face and not the back. If I don't then I get terrible vibration through the stearing wheel.

Just something to consider.

 

[Ian]

I've removed my spacers and I think it may be better but didn't drive enough at faster speeds today to confirm 100%, will find out tomorrow. Hope its gone because driving another 450 miles with it like that won't be fun.


I think my wheels fit my hubs without problems but I'll double check just to make sure theres not a tiny gap somewhere which isn't obvious without close inspection.

 

[zNathan]

Posted on your wheel wobble thread but thought I'd +1 John's comment above - had this same issue with my Rota's on my Z, the hub center doesn't allow the rim to sit perfectly flat on the hub. Chamfer the inside edge of the front rims and you'll most likely be sorted!!

 

[Wyn]

I think it may be better but didn't drive enough at faster speeds today to confirm 100%

I think that's your problem right there

As the boost comes in your rs lets go and you just cant hold on

 

[Ian]

Nathan - Did it look like your wheels were seating correctly? Was it only a very small offset that you wouldn't notice without a very close look? If so, this could still be my problem.


Wyn - That could be the problem - If she was FWD! Actually under power load I don't notice the wobble, only under steady speed. I can use full power in first gear without the tyres even smoking up (they spin a bit but not so much they smoke, just a bit of slip), even Greg (who has been in thousands of fast cas) was surprised at the amount of grip she has, as am I. Advantage of smallish twin turbos and a smoothe linear power curve I guess. (I'll post the power curve later)


Dyno sheet I have has 472HP and slightly over 485lb/ft, but on the road today we actually added more timing and she definitely has more now. Seems BP ultimate is **** but Vpower is good, as we have no shell in NI I'll probably run her on octane booster, you really notice the extra power so I think its worth the expense.

Need to design a better downpipe and then with some cam timing along with perhaps some tweaks to my intakes (smoother entry to the turbo and v stacks in the filters) and I can get over 500hp easy. No rush for this though, shes a beast as it is. But I know I'm a bit power crazy so this won't last.

 

[zNathan]

Hi Ian - it happened when my car was over at Duncan's having some bits and pieces done. You wouldn't notice they're not seating properly by eye as it's just the tiny lip at the bottom of the hub center that hits. Bit odd though if it was happening when running spacers, unless they themselves were also being affected?

 

[Ian]

Well, the spacers are slightly bigger than the centre hub so will only locate on the wheels studs, however as the spacers are also no hub centric this should not affect the wheels. However the spacers are 10mm and if these are not centred on the hub and the wheels also not that means its only the studs centring the wheels and holding the weight plus an extra 10mm out from the hub which increases the leverage effect on the studs even more the I guess it quite possible that this is what is causing the issues.

The joys of older cars and engineering I guess.

 

[Ian]

Power Curve before we added slightly more timing, won't be much more than this though, perhaps 480HP now and just under 500Ftlb, reason its quite torquey is because the downpipe seems to be restricting flow a bit, If I can re design it better I should get over 500hp but will loose a bit of torque, the power should also not tail off quite as early.



You can see its quite a smooth curve, no sudden power spikes, that's why I get such good traction.