Street Touring Hatchback (STH) discussion/setup

[JackRabbitSLIM]

rear shocks on the same bump feels about in in 0.5-0.7 critical damped range

Can someone explain why this should be considered important? Serious question.

I can't find a shock dyno for the MK7 Ohlins, but everything I see for other platforms shows DFV Ohlins plots as very digressive. So that means you would be trading more damping in the handling range for a little bit of damping in the bump range all based on your butt dyno. The reason digressive shocks exist is so the handling is tune-able and the bump performance stays relatively the same.

I think you'll find that it makes more sense for you to tune your handling with the adjustments you have and deal with bump compliance if/when it becomes an issue for you. If you had a bump issue you could probably hear your diff/engine doing something weird during the recovery period. But as always whatever's cool with me, give it a try if you want.

The only time I've worked on, or heard of people working on, bump compliance was in STS where the Hondas run so low that the front upper control arms can actually hit the body if they hit a bump while turning and also the rear ends do something strange (bouncing/skipping) when ride height is super low and bumps are getting hit. It's pretty easy to see from outside the car and feel from inside the car when you have an issue with bumps.

 

[xXDavidCXx]

I’m working on bump compliance as a second order effect of my primary goal of reaching 2.0/2.2hz suspension frequencies, and the appropriate damping as depicted by Dennis Grant’s “Autoctoss To Win” e-book and website www.farnorthracing.com/autocross_secrets19.html

 

[marka]

Howdy,

For you guys with upgraded intercoolers in STH... What kinda IATs are you seeing?

I'm on the stock intercooler, stock downpipe, and stage 1 EGT. I'm seeing 150 to 165 IAT sitting on the start line. It drops a little during the run (presumably with air flow). This is in Pittsburgh, PA summer, IIRC ambient temp was around 80 to 85 deg?

Only interested in STH legal options at this point.

Mark

 

[replicate]

Yup, you need to be careful with that much camber. Try increasing the toe in small steps- no more than 1/8" at a time. I can send you a conversion chart that addresses tire diameter, toe in fractions of an inch and angular measurements if that would be helpful. Once you have your alignment set, you can use my string line technique to quickly adjust toe at the event in a few minutes.

I’m running toe out front and rear (can’t remember how much). -3deg front camber and -2.5 in the back. Front is a little loose for street driving but not too bad. I’m still chasing more rotation in the rear. Going to try a stiffer rear bar.

 

[bfury5]

I’m running toe out front and rear (can’t remember how much). -3deg front camber and -2.5 in the back. Front is a little loose for street driving but not too bad. I’m still chasing more rotation in the rear. Going to try a stiffer rear bar.

What's the rest of your setup like? I might have missed it, went back a few pages but didn't see anything

 

[replicate]

What's the rest of your setup like? I might have missed it, went back a few pages but didn't see anything

Up front
140tw 255/35/18
Stock DCC struts with MSS track springs
Aluminium subframe
CSS hub carriers
Whiteline strut tops and LCA - achieves 9deg caster from memory

In the back
140tw 235/40/18
Whiteline RSB
Superpro trailing arm bushes

 

[bfury5]

Up front
140tw 255/35/18
Stock DCC struts with MSS track springs
Aluminium subframe
CSS hub carriers
Whiteline strut tops and LCA - achieves 9deg caster from memory

In the back
140tw 235/40/18
Whiteline RSB
Superpro trailing arm bushes

You mention MSS track in the front, are you stock springs in the back?

 

[replicate]

You mention MSS track in the front, are you stock springs in the back?

Sorry, should have been more specific. MSS front and back. Rear has their track springs. Fronts are actually all the same rate.

 

[bfury5]

Sorry, should have been more specific. MSS front and back. Rear has their track springs. Fronts are actually all the same rate.

Not sure what their track rate is, but I bet it's not nearly enough to handle a 140tw tire. The rear is probably rolling through corners and as the rear suspension compresses it dynamically gains camber, so that 2.5 could be higher. A stiffer bar will certainly help, but it will only get you so far. Stiffer springs is probably what you need

 

[bfury5]

One thing I've been toying with is getting a hatch brace for the trunk area. I'm not sure it'll offer any real handling improvements, but with the stiffer suspension I'm hoping it might stop some of the rattles and creaks on the inside.

The SCCA rules section 14.2.G.1 state: "A 2-point strut bar may be added, removed, modified, or substituted, but only with another 2-point strut bar."

It also states: "Additional holes may be drilled for mounting bolts. Only “bolt-on” attachment is permitted. Interior trim panels may be modified to allow installation of strut bars. Holes or slots may be no larger than necessary and may serve no other purpose. This does not permit any modifications to the frame or unibody beyond the allowed mounting holes."

My primary question here is what qualifies as a rear strut brace? The one I was looking at from Eurosport is the only 2-point bar I could find. It appears to mount pretty high in the back, in the relative area of where the two rear strut mounts are. I'm just not sure it mounts close enough to be considered a rear strut brace. For $99 I figured it was worth a shot if it fell within the rules. Thoughts?

 

[xXDavidCXx]

I don't know why people with street cars and relatively soft suspension would even consider strut bars for autocrossing. It won't contribute to faster times.

Save the money for tires.

On the other hand, what are these rattles and creaks do you speak of?

 

[bfury5]

I don't know why people with street cars and relatively soft suspension would even consider strut bars for autocrossing. It won't contribute to faster times.

Save the money for tires.

On the other hand, what are these rattles and creaks do you speak of?

Yeah like I said, I know it won't make me faster. I get creaks in the back doors and B-pillar areas over bumps when the chassis flexes. The question above was to check the legality of the strut bar and not its performance merits.

 

[xXDavidCXx]

Yeah like I said, I know it won't make me faster. I get creaks in the back doors and B-pillar areas over bumps when the chassis flexes. The question above was to check the legality of the strut bar and not its performance merits.

I think what you linked is legal, but I doubt a strut bar will help much. Maybe take it to the dealer and have them find and massage the panels that are the problem.

 

[jmblur]

I don't know why people with street cars and relatively soft suspension would even consider strut bars for autocrossing. It won't contribute to faster times.

Save the money for tires.

On the other hand, what are these rattles and creaks do you speak of?

I've heard really good things about the front strut bar improving turn in feel. I have the eurocode one sitting in a box... If I unpack enough boxes this weekend I might just have time to install next week. I do have the rear bar installed, since it was a stupid easy install, but did it with winter tires on so no clue if it actually did anything. Will do some A/B testing when I can actually do another autocross sometime this fall.

Will better feel improve times? Probably not. But the extra confidence might.

Sorry, should have been more specific. MSS front and back. Rear has their track springs. Fronts are actually all the same rate.

I've been toying with putting on the MSS springs if I find a good deal. Thoughts for a dual purpose street/autocross car? I'd love if they share more info on spring rates but doubt they will. Might contact them to see...

 

[replicate]

I've been toying with putting on the MSS springs if I find a good deal. Thoughts for a dual purpose street/autocross car? I'd love if they share more info on spring rates but doubt they will. Might contact them to see...

They are actually pretty impressive. Ride like stock on the street and perform really well on the track.