Hyperblade's KP61 Racecar "KP61R" Discussion

[Hyperblade]

31 minutes ago, mjrstar said:

With the engine and box combo did you consider uprighting the engine to to sit level which would maybe give more room for headers, or do you think the headache of getting the tilted over gearbox to work nicely isn't worth the headache?

My mate with the Datsun is keen on an upright k with the s2000 box and to me it looks like clocking the gearbox will result in the window for the starter being a no-go as well as some clashing of bolt holes.

No didn't really consider it, all the adapter plates I looked at had it tilted. Trying to use one of those would just not work, your better to make your own.

Also that means sump/pickup isn't level which would not be ideal.

If you upright it, I would have issues with the lower alternator position hitting frame rails. Also the intake side has way more stuff on it and you would rapidly run out of room.

On the flip side, you could just rotate the whole combo and my gearbox bracket could actually be designed to match the tilt if the engine was uprighted (with a lot more work), or design your own. As all you have is selector shaft coming out. However no idea on impact of that on the internal oil pump in the gearbox.

The biggest issue with the s2000 box is the rear flange, your mate needs to think carefully on the impact of it, that's been the tricky/expensive thing to solve for me.

[Rhyscar]

I'm no ford connoisseur, but I don't know if capri steering and suspension will be an upgrade.

Seems like there are a lot simpler, small mods you can make that would sort out the ackerman. For example - less roll centre would help, Shorter steering arm, different angle on steering arm, adjustable steering arm (I think what Markku suggested). The way I see it, you've only got 1 geometry problem to solve, while avoiding a large negative impact on the others - but I'm sure theres some room for others to be 'worse' without being 'bad'

Roll centre - OK?

Ackerman - Very Bad

Camber - OK? 

Bump Steer - OK? 

 

 

Interested in how you came to that conclusion, and willing to provide some intellectual challenge to avoid a ford-doom hole. 

 

[Hyperblade]

1 hour ago, Rhyscar said:

I'm no ford connoisseur, but I don't know if capri steering and suspension will be an upgrade.

Seems like there are a lot simpler, small mods you can make that would sort out the ackerman. For example - less roll centre would help, Shorter steering arm, different angle on steering arm, adjustable steering arm (I think what Markku suggested). The way I see it, you've only got 1 geometry problem to solve, while avoiding a large negative impact on the others - but I'm sure theres some room for others to be 'worse' without being 'bad'

Roll centre - OK?

Ackerman - Very Bad

Camber - OK? 

Bump Steer - OK? 

 

 

Interested in how you came to that conclusion, and willing to provide some intellectual challenge to avoid a ford-doom hole. 

 

Always happy to be challenged by people!

I need to get it all into a spreadsheet to confirm with numbers and visuals.

But pretty confident it's got bump steer issues (rack also looks like it's in at an angle right side lower then left...). Pretty sure rack is also to short for the setup.

While that is all fixable on it's own, 

There are a couple of other factors I'm considering

• Repairability, and easy replacement options.
• Support for wider 10" rims (to be able to get cheaper tyres long term again)
• Setup has already been put into a very quick starlet track car (1:32 with 1600cc, which if you know Ruapuna is very quick).
• The ability to sell my current setup as is, covers a fair amount of the costs to switch.

So it's not entirely an unknown.

But ultimately the thing I need to do is get all the measurements into a suspension spreadsheet and prove it. Then look at where I want to go to and confirm it will work.

[Truenotch]

Two questions:

How many sets of new tyres could you buy for the price of the upgrade?

How much racing will you miss by making such a big change?

[Rhyscar]

Yeah that's definitely the right approach, do the numbers and go from there. It's crazy that the setup is so wrong, being custom built. It's like they didn't consider the geometry at all during assembly. 

This is definately the point of club racing where it requires a lot of finese to put a car together well. It's not just a matter of A+B = fast. 

 

10" rims in the front is huge! What's that a 265 tyre? Geez!

 

Agree with Markku's comments ^^

[Hyperblade]

18 minutes ago, Truenotch said:

Two questions:

How many sets of new tyres could you buy for the price of the upgrade?

How much racing will you miss by making such a big change?

• 1.5 to 2 (by the time i sell my old setup)
  • At the last prices I had for the tyres, pretty sure they will be higher these days.
  • I have enough of the current tyres for a while (although getting really old now), so not something i'm panicking about.
  • It's not the driving factor for the switch, but worth considering with any change in the area.
• Probably Less then me making steering arms, new rack and rack mounts as I can outsource some of the work.
  • I'm also at the stage where I want things done right, and while I would prefer not to miss the start of another season, I'm ok with it as I help out enough organising them so involved either way.

Good questions though!

16 minutes ago, Rhyscar said:

Yeah that's definitely the right approach, do the numbers and go from there. It's crazy that the setup is so wrong, being custom built. It's like they didn't consider the geometry at all during assembly. 

This is definately the point of club racing where it requires a lot of finese to put a car together well. It's not just a matter of A+B = fast. 

 

10" rims in the front is huge! What's that a 265 tyre? Geez!

 

Agree with Markku's comments ^^

Well to be fair the focus was putting the engine in (and significant changes to the rear end) and things flowed from there rapidly, we didn't initially plan to swap the cross member but had to to fit the engine in (so that's on me for not verifying clearances), we just never took the time to double check things, we just switched the struts and lower cross member around (and rewelded rack brackets) and moved on to the next issue so wasn't actually much custom stuff going on there.

The car sat for 2 years afterwards being worked on, so It's also on me for not thinking through the ramifications. Also some of the issues would still apply with the rack in the original behind position, and that's because I just bolted on T3 parts and winged it (as was dealing with stubb axle/bearing issues which triggered the switch to AE86).

Tyre is a 24/57 - 13
Tread width: 241mm, (but across all the brands ranges from 245 to 260mm)
Section width 289mm it's a F3/F4 tyre.

If you look at all the brands offering slick tyres, the F3/F4 is a common size across them all. Otherwise everything has pretty much shifted to 17"+ tyres, there are 15" options, but actually more limited then 13".

 

[mjrstar]

I don't know if this is viable or not but I'll chuck it out there just in case..

If you were able to bring the font cross member forward say 40-50mm to fit the rack back in its original home this could give some advantages from a car setup perspective. 

-Longer wheelbase so more stable.

-Added castor

-Improved front/rear weight distribution.

Yes you'd have to shorten the front swaybar arms, and modify the engine mounts, and probably make up a couple of new brake lines.. but you wouldn't need to buy much additional hardware. 

[Hyperblade]

1 hour ago, mjrstar said:

I don't know if this is viable or not but I'll chuck it out there just in case..

If you were able to bring the font cross member forward say 40-50mm to fit the rack back in its original home this could give some advantages from a car setup perspective. 

-Longer wheelbase so more stable.

-Added castor

-Improved front/rear weight distribution.

Yes you'd have to shorten the front swaybar arms, and modify the engine mounts, and probably make up a couple of new brake lines.. but you wouldn't need to buy much additional hardware. 

So definitely good thinking. And something we considered.

Unfortunately we have already done all those changes! 🙃

Current wheel base is AE86 in length, which we did for all the reasons you stated.

Bottom arms would have to go a long way forward now to put the rack behind.

Number 1 spark plug hole is inline with the top of the struts and the rack needs to sit in front of sump/pulley so not a lot of room to move it further back, could go dry sump, but that then needs the rack move a long way back to get it to fit in the middle of it. 

 

[Truenotch]

Hey, I have a dumb idea for you to consider.... 

MX5 front knuckles and double wishbone setup.

Benefits: cheap and off the shelf, well proven, lots of aftermarket support, already front rack, doesn't require 1970s British Ford parts. 

[Hyperblade]

1 hour ago, Truenotch said:

Hey, I have a dumb idea for you to consider.... 

MX5 front knuckles and double wishbone setup.

Benefits: cheap and off the shelf, well proven, lots of aftermarket support, already front rack, doesn't require 1970s British Ford parts. 

All dumb ideas considered!

A few potential initial issues i see (from a quick google) that would require more investigation

• Stud pattern is different (4x100 vs 4x114.3), hub can't be redrilled.
• 13" wheel fitment (sounds like it's close)
• 13x10" fitment, not sure how easy it is to clear the bottom arm when they turn.
• No off the shelf brackets for my brakes calipers
• May have to replace shocks?
• Fitting the top A arm in might be tricky.
• Mounting of the rear lower arm pivot point would be tricky

 

RE the 1970's ford parts, none of what i would be putting on the car would be second hand, all would be brand new reproductions... So I'm not to worried about that aspect of it.

[Truenotch]

1 hour ago, Hyperblade said:

• 13" wheel fitment (sounds like it's close)
• 13x10" fitment, not sure how easy it is to clear the bottom arm when they turn.

There's a bunch of MX5s running wide 13s, so I'm sure it won't be too hard. 

1 hour ago, Hyperblade said:

• Fitting the top A arm in might be tricky.
• Mounting of the rear lower arm pivot point would be tricky

There's a selection of tubuar front subframes on the market because people use them for exocet / locost sports cars. It'd be interesting to see how a subframe might interfere with the Starlet body.

Someone half converted Simon's old AE86 to FD RX7 front suspension using the factory RX7 subframe, arms and rack. I reckon a better planned version of this could be amazing. 

 

[mjrstar]

Fd rx7 runs a pretty long steering arm on the knuckle, so I assume thy run a pretty fast ratio rack, which may or may not be a problem to run without power assist. This won't help packaging under a 13" wheel.

One of the plans I looked at was the fd knuckle into mx5 but the height of the knuckle was a limiting factor as well.

Also is the current Ackerman causing a specific problem (maybe understeer in slow speed corners) because depending on how much work the inside tyre is actually doing then the anti-ackerman could be not really a problem? Or could be tweaked slightly with a bit of a toe adjustment?

Kevin's orange starlet is pushing some significant lateral g's which does mean the inside wheels are sometimes along for the ride. maybe the motorbike engine prefers it that way.

[Hyperblade]

1 hour ago, Truenotch said:

There's a bunch of MX5s running wide 13s, so I'm sure it won't be too hard. 

Famous last words for someone who doesn't have to do the work... 🙃

Just to give some background on the options, the Ford setup I'm looking at is based on a genuine Zacspeed setup, in a starlet, with 13x10" rims proven on the track. So it's the easiest option as basically copy/paste.

Will do some more detailed googling and see if your suggestion is viable as an option.

12 minutes ago, mjrstar said:

Fd rx7 runs a pretty long steering arm on the knuckle, so I assume thy run a pretty fast ratio rack, which may or may not be a problem to run without power assist. This won't help packaging under a 13" wheel.

One of the plans I looked at was the fd knuckle into mx5 but the height of the knuckle was a limiting factor as well.

Also is the current Ackerman causing a specific problem (maybe understeer in slow speed corners) because depending on how much work the inside tyre is actually doing then the anti-ackerman could be not really a problem? Or could be tweaked slightly with a bit of a toe adjustment?

Kevin's orange starlet is pushing some significant lateral g's which does mean the inside wheels are sometimes along for the ride. maybe the motorbike engine prefers it that way.

Yeah, car doesn't like to turn in, scrubbing of tyre, my car used to lift inside tyre a lot on the 15"s but not anymore after 13"s and sway bars.

This is current setup, I still need to work out the wheel hub to outer tie rod positions, but that doesn't appear impact current roll center/instant centers *

 

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* I've brought the HPA suspension course, so I just have to sit down and find some time to watch it and understand what it all means, just been working on plumbing for now.

[Rhyscar]

That looks pretty good from a RC and bump perspective in the front. Can't ask for much more than that I reckon.

It would be interesting to review compare front to rear squat/anti dive and roll centres since you've got so much adjustability at both ends. This will tell you if some weird pitching is happening during weight FR transfer. 

 

Only suggestion would be to try slightly less camber/spring for more turn-in since the addition of swaybars.