SCCA Street Touring discussion/setup (Formerly Street Touring Hatchback STH)

[krs]

Someone still living with their parents, I assume. So a student or whatever.

Or the dorm. But that was my first thought. ¯\_(ツ)_/¯

 

[MonkeyMD]

Someone still living with their parents, I assume. So a student or whatever.

Yeah but then you take parents income into account. Household income

 

[mrmatto]

Yeah but then you take parents income into account. Household income

True point. THE POORS ARE NOT AUTOCROSSING.

 

[mkvii.717]

Has anyone had a low tire pressure light come on during a session? I was headed to start and it came on. I checked the tires visually before my run and they all looked good so I did my run. Then checked with a gauge after I got back to the grid and all are high if anything. I reset the light finished four more runs and a 2 hour ride home and now it is the next day all tires seem fine and the light has not come back. It just seemed odd.

 

[GTIfan99]

Has anyone had a low tire pressure light come on during a session? I was headed to start and it came on. I checked the tires visually before my run and they all looked good so I did my run. Then checked with a gauge after I got back to the grid and all are high if anything. I reset the light finished four more runs and a 2 hour ride home and now it is the next day all tires seem fine and the light has not come back. It just seemed odd.

Common. High or low seem to set it off. Also, setting when tires are hot will cause light when they cool.

 

[scrllock]

Has anyone had a low tire pressure light come on during a session? I was headed to start and it came on. I checked the tires visually before my run and they all looked good so I did my run. Then checked with a gauge after I got back to the grid and all are high if anything. I reset the light finished four more runs and a 2 hour ride home and now it is the next day all tires seem fine and the light has not come back. It just seemed odd.

very common, fronts get much hotter and the difference between corners is what flags it.

 

[mkvii.717]

Common. High or low seem to set it off. Also, setting when tires are hot will cause light when they cool.

fair enough just hadn't seen it before but it was my first time codriving with someone so it was getting pushed. I did reset it after getting the temps back down thanks

 

[odessa.filez]

The 034 bar I believe is one of the softest front sway bars sold for this chassis. It's the same diameter as the GTI stock bar (24mm)... and after having their ball joints I'm somewhat suspect of any measurements they publish (their RCO ball joints advertise 10mm of RC correction... they're 17-18mm taller than stock).

Taking a sway bar from hollow to solid has a practically non-existent effect on overall stiffness (as in less than a pound of force). Most of their added stiffness almost for sure comes from the "A" measurement being different than stock in the chart below.

I've actually taken my own measurements of an H&R 26mm front bar and it specs out as 80 or 120% stiffer than OEM. They sell a 28mm bar which MIGHT be better for autocross purposes.

View attachment 304037

More info here:
https://www.datadrivenmqb.com/suspension/swaybartheory
And here, while more track-focused, if you have a way to plot G forces might give you some ideas on how to determine if the bar is actually helping or not. Or adjusting between 2 different settings which is a lot more likely to be doable testing for autocross since the course is never the same.

With the 26mm bar on stiff when autocrossing, on 034 lowering springs there's some body roll, but with almost -4 deg of camber (I'm in XA, not STH) I'm not terribly worried about it. I prefer a softer setup overall on track.

View attachment 304038


I'm currently in the middle of "dynoing" a few different bump stops to try and improve things further. They're way overlooked when it comes to tuning the suspension except for a few little niche automotive circles (Miatas, BMWs).

View attachment 304040

View attachment 304041
I've talked to @mrmatto a bit about it... but I suspect one could probably get some bump stop packers (basically just delrin or plastic split washers) to slip over the shock shaft and play around with the engagement points of the bump stops. Start with something like 15mm in the rear and 10mm up front... will also help move the bias more towards oversteer. The bonus of this is they're easily removable so you can keep your comfort on the road, etc.

Off the topic of suspension setup:
There's some other really fun stuff I've been playing with on the ECU side of things. Basically commanding the throttle body shut (or nearly shut) and keeping the wastegate closed... the car essentially stores boost in the charge pipes so works like a weak form of anti-lag and makes it really responsive, especially in slaloms and coming out of a long sweeper where you're partly on the throttle. It's not enough to stay "spooled" but it takes a noticeable portion of lag/transient response out of the picture. Due to the logic of how the ECU regulates torque, still working through some part throttle driveability issues (sometimes the throttle plate will flutter open and closed), but that's moreso from a daily driving standpoint and hasn't been an issue on course or when driving in anger.

Yes you could run packers / shims. I do that with bump springs on the rear shocks.

Front, I run spring rubbers on stock GTI springs.

Setup is about 15 minutes to prep, 15 minutes to unprep.

Both swaybars disconnected. IMO all STH legal.

High spring rates for ax and daily ride doesn't suck.

 

[GTIfan99]

Yes you could run packers / shims. I do that with bump springs on the rear shocks.

Front, I run spring rubbers on stock GTI springs.

Setup is about 15 minutes to prep, 15 minutes to unprep.

Both swaybars disconnected. IMO all STH legal.

High spring rates and daily ride doesn't suck.

Where did you find spring rubber that fit the stock springs? That's awesome. Do you use for the rear too?

 

[odessa.filez]

Where did you find spring rubber that fit the stock springs? That's awesome. Do you use for the rear too?

I bought my spring rubbers from Acrotech. Haven't done biz with them for a couple years, but back then you could buy 5.5 diameter rubbers, any thickness you want, and a choice of durometer.

https://www.acrotechinc.com/automotive-applications/

I run two spring rubbers up front on each side. One is 90 durometer, one is 60. Thickness is 1.25". The 90 is so stiff I had to cut grooves in it so it could flex enough to install.

On the rear shocks I have bump springs instead of bump stops, with packers / shims. The benefit(?) of springs is linearity.

One could run spring rubbers in the back. I tried it but found the bump spring approach to be more cost effective and easier to manage.

Up front you could shim a bump stop / bump spring instead of using spring rubbers. One would have to fab the shims as the strut shaft is thicker than what's available of the shelf. Also, the amount of travel for daily driving would need to be managed: getting enough travel for street may lead to a shorter bump stop and much more progressive compression.Might work, but more trial and error might be needed.

 

[Jmitchell4873]

I bought my spring rubbers from Acrotech. Haven't done biz with them for a couple years, but back then you could buy 5.5 diameter rubbers, any thickness you want, and a choice of durometer.

https://www.acrotechinc.com/automotive-applications/

I run two spring rubbers up front on each side. One is 90 durometer, one is 60. Thickness is 1.25". The 90 is so stiff I had to cut grooves in it so it could flex enough to install.

On the rear shocks I have bump springs instead of bump stops, with packers / shims. The benefit(?) of springs is linearity.

One could run spring rubbers in the back. I tried it but found the bump spring approach to be more cost effective and easier to manage.

Up front you could shim a bump stop / bump spring instead of using spring rubbers. One would have to fab the shims as the strut shaft is thicker than what's available of the shelf. Also, the amount of travel for daily driving would need to be managed: getting enough travel for street may lead to a shorter bump stop and much more progressive compression.Might work, but more trial and error might be needed.

I might have to try some stuff from acrotech if I end up trying to run GS or DS. I still haven't decided on GTI or R to replace my current Mk8.

Thanks for the link!

Have any video of AutoX runs with both bars disconnected?

 

[odessa.filez]

I might have to try some stuff from acrotech if I end up trying to run GS or DS. I still haven't decided on GTI or R to replace my current Mk8.

Thanks for the link!

Have any video of AutoX runs with both bars disconnected?

I don't think you can use spring rubbers in DS or GS.

I was interested in spring rubbers after reading about their use in NASCAR, changing them in pit stops. My install is not as quick but it sounded like it would be easy for ax.

No videos but a couple pics that shows the droop. Second pic, I'm driving out of a hole in the course and both insides are nearly off the ground.

I was motivated to try no-bars as I don't have VAQ and I've blemished inside tires from wheelspin. The bars on the car are now for street only.

 

[Jmitchell4873]

I might have to try some stuff from acrotech if I end up trying to run GS or DS. I still haven't decided on GTI or R to replace my current Mk8.

Thanks for the link!

I don't think you can use spring rubbers in DS or GS.

I was interested in spring rubbers after reading about their use in NASCAR, changing them in pit stops. My install is not as quick but it sounded like it would be easy for ax.

No videos but I may have a pic that shows the front drop.

Gotcha. Just a STH or STU trick?

 

[odessa.filez]

Gotcha. Just a STH or STU trick?

Yes and I presume with more modified classes. Spring rubbers are explicitly permitted in STH.

 

[GTIfan99]

Autocrossed the car for the first time yesterday.

Car was in GS trim, except for the shift knob and R wing, so ran STH, so I could hang with my homies @mrmatto

The good. Completely stock with 17 x 7.5 and two year old 245 40 17 RE71R , the car was very neutral for the first two runs. I ran both my mk7.5's new and stock and they massively understeered. So the mk8 is awesome in that respect.

The bad. The VAQ quit working by the third run. I mean massive inside tire spin, then car cut power. It'll be interesting having to deal with the dealer and trying to explain it the service department.

So as long as the dealer can get the VAQ working correctly, I think this car is going to be amazing as the mods start getting added.