Sams Polo 3.0

[Sydneykid]

I think we talked about this in my previous Polo's thread but if the droplinks are moved onto the wishbone directly under the ends of the FARB rather than acting off the struts flanges, they'll be acting on the wishbone 1/2 way along its length. I would have thought that would make it easier for a set amount of wheel movement to twist the FARB because it has more leverage over it than previously. That would necessitate a thicker bar to create the same roll resistance as before wouldnt it? input please!!!

The same maths (leverage and movements ratios) applies to the swaybar as to the springs, if you are moving the link inboard then it will have an effect on the rate of the swaybar. You could try the measurements and maths, but I'd always recommend the practical route and measure the relative movements, how much does the wheel move compared to how much the swaybar moves. What I do is to remove the spring and reinstall the strut, then disconnect the other side of the swaybar and measure how much the connected side moves in comparison to the centre of the tyre (wheel studs). Swap over to the other link position and remeasure.

On the later BMW E36's the swaybar is connected to the strut leg and it preloads the swaybar when the steering is turned. So you get different amounts of antiroll depending on how much steering lock you have on, very undesirable. When we moved the links to the lower control arm (like the earlier E36's) we had to go up 2 mm (from 25 mm to 27 mm) in bar diameter to get the same amount of anti roll.

I think you will find that sticking with 7 kg/mm front springs was the right move with the larger swaybar.

FWIW, I think having the L&R links on the same side of the strut will make the pre loading worse.

Cheers
Gary

[sambb]

Thanks Gary. I'm at work staring at a spare wishbone trying to figure out how I can mount a rail across the top of it for droplinks to attach too. Ever seen anyone weld bracketry onto those pressed out wishbones without blowing holes in them?
And yeah I just cant get my head around those droplink flange positions on the MCA's. A bit baffled by that. Think i'll cut one of them off and get it re-welded to the other side if I cant sort a wishbone solution.

[sambb]

So I've been trying to figure out which of my two intercoolers is the one to stay with. The one off the old car is a SEAT sport - a large twin pass tube and fin with offset entry/exit of 52.50mm I.D seen in the last two pics.
The new cars one was a bit of a mystery till I found this old post:

https://www.vwwatercooled.com/forums/f127/meet-my-polo-25317-44.html?highlight=Guy_H+APR+intercooler+flow+comparison

I new it was from APR but have since found out that they were APR's Golf Mk4 GTI intercooler. They were modded to fit the Polo as Guy Harding used one in a Polo tarmac rally car and then made a few and sold them. In the pic its the long single pass with short vertical fins. You can see where its end tank was modded to help it fit.
The other intercooler in the pic is a Forge twin pass. They were always touted as the one that produced the best cooling but from what I can gather this came at the detriment of flow restriction - something the APR doesnt seem to suffer from.
Now the SEAT sport (final two pics) I've run in the past is a bit of an unknown as I've never seen flow tests for it, but being a pretty a pretty thin cored twin pass with small offset entry/exit of only 50mm, surely couldnt outflow the APR. I've been driving around monitoring ambient vs inlet air temps as the new car has a scan gauge fitted and being able to see iAT's in real time is great. Yes the APR heatsoaks in traffic but not in a dissimilar way to the SEAT so I dont think there's much to seperate them there. The APR also fills the bottom grill but doesnt obscure any part of the radiator north of the crash bar so might actually help RE water temps. And on that I have noticed that this car does run a tad cooler than the last car that had the SEAT despite also having an A/C core, still running the water to oil heat exchanger that should drag water up if anything when up to temps and not having any blanking to fill the voids around the radiator. So there may be something in that. But if it flows 432 cfm at 48 inches then its well above the Forge which is a similar design to SEAT so should be the go. I'll have to have a proper dig around under the car but the APR also looks to have a 2/1/4in entry and a 2 inch exit which should be pretty easy to take out to 2/1/4in space permitting. So I think APR intercooler it will be.

[Sydneykid]

Thanks Gary. I'm at work staring at a spare wishbone trying to figure out how I can mount a rail across the top of it for droplinks to attach too. Ever seen anyone weld bracketry onto those pressed out wishbones without blowing holes in them?
And yeah I just cant get my head around those droplink flange positions on the MCA's. A bit baffled by that. Think i'll cut one of them off and get it re-welded to the other side if I cant sort a wishbone solution.

The lower control arm link is the superior solution. Is the inner most bolt on the ball joint too far outboard to use for the swaybar link? It doesn't have to be perfectly vertical with sphericals both ends.

If not tig would be OK on the lower control arm, easier to be gentle than a mig.

Cheers
Gary

[Sydneykid]

Intercoolers, arguably the most circular of references. Personally I'm not a fan of dual pass, the additional restriction always outways the extra cooling for me. You end up having to run more boost at the compressor for the same boost at the inlet valve. Which inevitably means higher airflow temperatures out of the compressor, so more cooling is needed. Whereas the single pass has less restriction which means we can run less boost at the compressor for the same boost at the inlet valve. Which inevitably means lower airflow temperatures out of the compressor, so less cooling is needed. And around we go in the circle.

Distilling it down, if you are running E85 with a boost (airflow) limited compressor then the single pass would be my choice. If you are Pump98 with a compressor with spare boost (airflow) then dual pass would be my choice.


Cheers
Gary

[simon k]

The lower control arm link is the superior solution. Is the inner most bolt on the ball joint too far outboard to use for the swaybar link? It doesn't have to be perfectly vertical with sphericals both ends.

If not tig would be OK on the lower control arm, easier to be gentle than a mig.

Cheers
Gary

here's a Subaru LCA with the swaybar link bracket...

[sambb]

RE the intercooler, I was hoping you'd say that. The existing turbo, a K04-001 is basically just what I've already had but with a slightly bigger exhaust wheel. So its a bit more midrange-ey but still undeniably small and boost limited. I'm going to swap in my ported exhaust mani to free things up a tad more and help cyl 3 which is really choked down on the stock mani, swap over my turbosmart wastegate and then i'll probably leave it that way for a while till I can get the Golf 6 Gti turbo in there. But even that is pretty small so I think the single pass is the way to go.

[sambb]

RE using the inner most ball joint bolt.....its a no go. Even with the Audi TT ball joints in there which put the inner most bolt further up the arm, its still too far outboard and at full lock the caliper would get in the way of a drop link running out to there.

the bar sits directly above here on the wishbone and the drop link would have to attach to the arm in a similar position as the driveshaft runs across the middle of the wishbone.
It'd be nice to just take a piece of squared channel and slide it over the front edge of the wishbone and bolt it up with crush tubes, but the surface of the wishbone is all contoured and it doesnt present any flat surfaces. I think it'd look like a dogs breakfast.
I like the pic that Simon put up of the Subi arm in the next post. Can you weld a tab on like that and the arm is strong enough to take the forces in that one position? What worries me is that the natural pick up point is half way along the arm.....on a 22mm bar it wouldnt be able to fold the arm in half would it?

[sambb]

and looking at it again, the only place you'd think you get a crush tube in, would be at the big hole in the wishbone. But that been sort of dimple die'd and there's not really any way that you could feed a crush tube in that could be used at the two holes just back from where the flange needs to be. I think it needs to be welded.

[sambb]

In other suspension news, I'm going to press out the super pro rear lower control arm (caster bushes) and press them back in in a different position. I'd previously run them in the outer most 9 O'clock max caster position because at the time the only way I could get max caster was at the subframes (bush position + subframe eccentric bolts). But now that I've got strut tops its not super important to get it all at the bottom and I need to be mindful that I need 225/45/16's to fit so cant run the tyre as far forward at the bottom as I had.

What I want to do is either press those bushes back in at the 6 o'clock position to reduce anti-dive/pro-lift or choose a 7/1/2 O'clock position that is a middle ground between the min anti-dive and max caster position. thoughts pleeease........

[sambb]

best pic I could get with the car on the ground. The convoluted tube of the brake ducting in the foreground sort of obscures the wishbone a bit but the bar end sits roughly half way along the wishbones span and actually is over the front edge of the wishbone too. Should be easy to get one of the horse shoe shaped droplinks around the driveshaft though.

[sambb]

Rear brakes

I believe the new car has Audi TT quattro vented (22mm wide) 256mm discs and 2WD 125Kw Bora V5 calipers. Standard is solid 9mm wide and 232mm diameter. Both Bora and Polo calipers are single piston.
I'd like to find out if their piston displacement is the same.

The stock Polo F:R weight bias is 66:34. The Audi TT quattro which had the 256mm vented rears is 60:40. (https://www.audiworld.com/model/tt/04/04tt.pdf)

Clay who did this rear stock --> vented conversion weighed the difference and it adds 1Kg per corner.

So is the 2kg unsprung weight saving off the rear beam justifiable enough to go back to standard brakes, considering that the Polo is far far lighter in the rear in relative terms compared to the TT quattro, and was never rear brake limited to begin with??

[Sydneykid]

In other suspension news, I'm going to press out the super pro rear lower control arm (caster bushes) and press them back in in a different position. I'd previously run them in the outer most 9 O'clock max caster position because at the time the only way I could get max caster was at the subframes (bush position + subframe eccentric bolts). But now that I've got strut tops its not super important to get it all at the bottom and I need to be mindful that I need 225/45/16's to fit so cant run the tyre as far forward at the bottom as I had.

What I want to do is either press those bushes back in at the 6 o'clock position to reduce anti-dive/pro-lift or choose a 7/1/2 O'clock position that is a middle ground between the min anti-dive and max caster position. thoughts pleeease........

I always go with the maximum caster I can get, particularly on a FWD car as it reduces the need for excessive camber, which helps with the straight line traction (more tyre contact patch). Try the strut top adjuster at max caster and see if the tyres clear then.

Cheers
Gary

[Sydneykid]

Rear brakes

I believe the new car has Audi TT quattro vented (22mm wide) 256mm discs and 2WD 125Kw Bora V5 calipers. Standard is solid 9mm wide and 232mm diameter. Both Bora and Polo calipers are single piston.
I'd like to find out if their piston displacement is the same.

The stock Polo F:R weight bias is 66:34. The Audi TT quattro which had the 256mm vented rears is 60:40. (https://www.audiworld.com/model/tt/04/04tt.pdf)

Clay who did this rear stock --> vented conversion weighed the difference and it adds 1Kg per corner.

So is the 2kg unsprung weight saving off the rear beam justifiable enough to go back to standard brakes, considering that the Polo is far far lighter in the rear in relative terms compared to the TT quattro, and was never rear brake limited to begin with??

If you go with a 2 piece rotor/hat sometime in the future you will easily save the 1 kg.

I assume the front brakes have had a substantial upgrade as well, which has relevance to the balance question?


Cheers
Gary

[Sydneykid]

RE using the inner most ball joint bolt.....its a no go. Even with the Audi TT ball joints in there which put the inner most bolt further up the arm, its still too far outboard and at full lock the caliper would get in the way of a drop link running out to there.
[ATTACH=CONFIG]52292[/ATTACH]
the bar sits directly above here on the wishbone and the drop link would have to attach to the arm in a similar position as the driveshaft runs across the middle of the wishbone.
It'd be nice to just take a piece of squared channel and slide it over the front edge of the wishbone and bolt it up with crush tubes, but the surface of the wishbone is all contoured and it doesnt present any flat surfaces. I think it'd look like a dogs breakfast.
I like the pic that Simon put up of the Subi arm in the next post. Can you weld a tab on like that and the arm is strong enough to take the forces in that one position? What worries me is that the natural pick up point is half way along the arm.....on a 22mm bar it wouldnt be able to fold the arm in half would it?

I have used the Subaru "C" links on other cars to get around the drive shaft. I always prefer to load the centre of the lower control arm, rather than apply a twisting motion to it from the swaybar. Loads up the bushes, wears them out and adds noticeable amount of friction to the up and down motion of the lower control arm.


The further outboard you can go the less anti roll you lose due to motion and leverage ratios. Mounted ~half way along the lower control arm you are going to lose ~75% of the anti roll.

Cheers
Gary