Sams Polo 3.0

Ok so to finally sign off in the front suspension I needed to be certain that I was calculating spring coil bound height or more technically speaking spring solid height correctly. After muddling through all the spring design/spec sites it seems that for a coil over type spring the ends are 'squared and ground'. In a squared and ground spring you basically count the total number of coils, even if they are ground, so every single 360 degree turn in the wire and then times it by wire diameter. For squared and ground springs it seems that you can also count the number of active coils and then add 2 (which accounts for the right angled and ground ends). I hope I have that right!
So given that I was able to confidently enough set up the fronts to a 2/3rds bump/1/3rd droop factor. So under the bump stop I have 65mm bump travel, 35mm droop travel and the spring 10-12mm away from spring solid height (spring bind) when the stop is fully eaten up. Currently I'm still running strut to ARB drop links on the super stiff 24mm FARB as I havent gotten the wishbones modified yet.
Because the wishbones still carry stock ball joints in the stock locations, despite having the top adjusters set for max diagonally back/in caster I dont have enough neg camber for the track - just under 2 degrees. But on the street with the high front ride height its pretty damn sharp at the helm.
So the remianing things for the front end in the short term are to get the wishbones modded to take droplinks which will reduce my front end roll stiffness on the 24mm bar. Tgese also carry the audi TT RS ball joints which will roll centre correct and give me lots (probably too much) neg camber. I need to swap in my subframes that have the rear lower control arm bushes set in the max caster position for even more caster. Then I can get the track rims/tyres on there and check for clearances and control arm angles and decide on a final ride height.
Oh and the steering rack needs it Polo 6R superpro high duro bush added when I do the subframes too. Then she'll be tight as a drum. It does concern me that on the Audi S3 hubs I'm considering, that their steering arms are significantly longer than the Polo ones. I definitely dont want a taller effective steering ratio so it looks like those hubs will probably need a different rack to really take addvantge of them and at this point I have no idea - Polo 6R rack ratios anyone?

this years Goodwood 2020 horizontal hillclimb. Nuts! how do two 70's F1 cars get in the top 4 against all that more modern tech? And that GTR four wheel sliding. love it. I really need to get on a track soon

Full 2020 Goodwood SpeedWeek Timed Shootout final - YouTube

Coil bind height is on the Eibach spec sheet, so I mostly use that. Otherwise I simply grab the vernier's and measure the gaps between the coils and then add them up, subtract that from the free height of the spring = the available travel.

You can always subtract camber with the strut tops if you end up with too much after the lower control arms with the TT ball joints are installed.

Longer steering arms will make the steering lighter, less lock and slower response to steering wheel inputs. You could measure and compare to get an idea how much, from the centre of the drive shaft to the centre of the ball joint.

I used to add some neg with the strut tops while I had the car jacked up to change to the track tyres, do the reverse when changing back to drive home on the street tyres.


Cheers
Gary

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Originally Posted by sambb

this years Goodwood 2020 horizontal hillclimb. Nuts! how do two 70's F1 cars get in the top 4 against all that more modern tech? And that GTR four wheel sliding. love it. I really need to get on a track soon

Full 2020 Goodwood SpeedWeek Timed Shootout final - YouTube

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The Calsonic R32GTR is hectic, it's 1,000 bhp makes my 700 bhp look weak, but I only have 2WD so I have an excuse :cool:

Cheers
Gary

decided to properly vent the guard liner behind the oil cooler.
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there is the worry that if ever a hose comes off that I'll almost certainly crash with oil all over the front tyre but OEM's do it this way too so I'm cool with that.

Sorting out the new cars APR stg 3 tune (K04-001) with the upsized exhaust hasnt gone well. It basically is going lean eg 0.95 lambda during the spool up and boost peak. I'm not sure if this is a failing in the tune because I never logged it with the smaller exhaust it was intended for. But I suspect that the bigger exhaust allows the boost to rise much more rapidly than the 2.5inch dump and so the fuelling is lagging as load rises. Despite lowering the peak boost there's not much I can do to temper the steepness of the boost rise. I got stuck into Lemmiwinks and played with fuelling, but even with lots of primary fuel added and extra 'increasing loads' fuelling, it still is miles too lean in that area despite the rest of the rev range sitting at 0.82 lambda. So last roll of the dice in an attempt to jag it with the generic tune was to fit up my GFB OEM replacement fuel pressure reg. I had this on hand for in case I needed to do a custom tune anyway and for if I ever get around to fitting the TFSI turbo. It all slots in nicely, direct fit even with the gauge in place. I set it for 4bar base pressure while the vacuum line to it was removed ( I think thats the correct way) and once the vacuum line was refitted it dropped to about 3/1/3 bar with the car idling at -20 in Hg. I'm pretty sure thats how you do it and that you dont set it for 4 bar with the vacuum line attached.
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I'm hoping that the slicker FPR might respond to boost signals a bit quicker than the 4 bar that was in there and miraculously the fuelling will fall into place. Logging to come! Failing that I'll have to weigh up whether I want to throw money at it with a stop gap custom tune, or just pull the turbo out and get the TFSI one in there. I do hope it works though because theres a twilight tarmac rallysprint on at Eastern CK on Feb 11 that I'd love to do, but not if I'm going to grenade the motor.

Sam, have you thought about the fuel pump not being able to keep up. Plus the stock injectors are used by APR on that set up IIRC.

yep its still stock injectors. Did a back calc off the injector open times in milliseconds from the nefmoto logs and they aren't actually maxed at 6000rpm. They are at about 85% duty. I did think it could be the pump but at WOT at the top end its getting as rich 0.80 lambda so there's no issue with fuel flow when the injectors are at max duty. It was just that area between 2300-3300rpm on the boost ramp, after that the mixtures are ok. But that lean area was kicking off timing pull that would just never clean up throughout the pull.
Just now I checked the test log that I did on the way to work with the GFB fuel pressure reg and lo and behold the afr's are consistent all the way through. 0.83-0.84 lambdas but still going really rich at the very top above 5700rpm for some reason. The OEM 4 bar that APR specc'd with their K04-001 tune must have been on the blink. I'll just give it a squeak more fuel pressure rather than muddle around with Lemmiwinks and I'd say I'll be able to get it to sit on 0.82's the whole way through and then hopefully it'll take some more timing. Imperfect I know, but it'll do temporarily until I can get this turbo properly tuned by Dave with the good bits (EV14 550's, bigger maf) OR pull my finger out and get the TFSI turbo in there.

No vacuum line connected is the proper process for setting fuel pressure.

Leaness at the early stages of boost build is not uncommon, where the airflow increases rapidly, the fuel demand follows as the torque builds. The low (comparative) rpm is also a factor, the combustion time is longer (than at higher rpm) so the burn has more time to complete. Which the lambda sensor sees as leaner than at higher rpm where any unburnt fuel is exhausted. Increasing fuel pressure is a common method of addressing the low (comparative) rpm leaness problem, but it does require some trimming at higher rpm to compensate. You are at the lessor of 2 evils currently, the engine is under the most load at high torque low rpm, so better not to be lean there even if it means being rich at higher rpm.

Cheers
Gary

Ok thats good to know. Logging is taking a while to do without a dyno but I'm zero'ing in on nice safe mixtures now. Because the injectors are stock and getting close to maxxed, I've left their pulse widths alone and have just climbed the fuel pressure to get more fuel in. Its at 4.2 bar ( a squidge over 60psi) so I think i'll stop there for fear of working the fuel pump too hard. The idle and partial load fuelling was resultingly richer but I was able to pretty easily pull fuel out of those spots and now the fuel trims are at nice low percentage levels. With that nearly done I can look at getting a bit more timing back into it and we'll see how it ends up. I think it'll tide me over like this for a while though until I get the suspension sorted.

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Originally Posted by sambb

Ok thats good to know. Logging is taking a while to do without a dyno but I'm zero'ing in on nice safe mixtures now. Because the injectors are stock and getting close to maxxed, I've left their pulse widths alone and have just climbed the fuel pressure to get more fuel in. Its at 4.2 bar ( a squidge over 60psi) so I think i'll stop there for fear of working the fuel pump too hard. The idle and partial load fuelling was resultingly richer but I was able to pretty easily pull fuel out of those spots and now the fuel trims are at nice low percentage levels. With that nearly done I can look at getting a bit more timing back into it and we'll see how it ends up. I think it'll tide me over like this for a while though until I get the suspension sorted.

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Keep in mind that the base fuel pressure is 60 psi then you have to add boost to determine what the fuel pump is pushing against. eg; 60 psi base + 20 psi boost = 80 psi.Cheers Gary