Season opener race report - Siltech widetrack front suspension.

[Davemk1]

Well, spring has reluctantly sprung and my autocross season has finally opened.I made a number of changes over the long Montana winter and was excited (and a bit nervous) to see how they worked when put to the test. This first event of the season was hosted in Helena, Montana at a police and fire training facility where they learn to slide firetrucks around! The place is huge and there is absolutely nothing to hit so the speeds are high for autocross. This means that there are lots of high speed violent lane-change maneuvers where the car is moving at 80 mph and one needs to change lanes and back again as quickly as possible. Honestly this can be scary stuff and it takes full commitment and trust that the car will be with you when you flick it at 80+ mph.

 

This past winter I installed a new Siltech +35 sidetrack front suspension, changed the spring rates to suit the different spring angle, made a new front ARB to work with the Siltech parts and lastly I made a new ultralight rear spoiler to help keep the rear end from wanting to pass the front during high speed transitions.

 

Saturday was cold (50°F) but dry in the morning and the brand new Avons needed a few runs to get properly scrubbed in so I could tell what the car was doing. After a few runs the car was telling me it wanted a stiffer front bar and that helped with turn-in while still keeping the rear end in line. I made a small shock adjustment (one click softer) on the Nitrons and my last run of the morning felt very good and my confidence was growing. After a lunch break it got just a bit warmer and grip was improved and I felt even better in the car I was able to set the fastest time of day (FTD) over a supercharged Ariel Atom and a full-race 600hp Corvette on 14” wide (!) slicks. My winning margin was .6 seconds on an 80 second run. Not a huge margin but it proved to be a winning one.

 

Sunday was warmer (70°F) so the grip was much better and the course was faster (different courses for each day) and after adding a bit of toe out to the front to aide turn-in on the tighter parts of the course the car felt just right. It felt planted and supple and it could really work with the surface instead of against it. The turn-in was very crisp but the rear end stayed in line even at high speeds. With my old narrow track front it would turn in well but then you’d need to mind the tail - now I can stay on the gas without having to worry that the rear end will come around. Simply brilliant. I set FTD again this time with a 2 second margin on a 77 second run. 

 

The new widetrack front is no doubt mostly responsible for the change. The rear spoiler might aide a bit at high speed but the car felt awesome even during 60 mph full throttle, long radius sweeper turns. I’m sure I have more room as a driver to take advantage of the new set up and that will hopefully come as the season progresses and I gain more confidence.

 

I wish I had photos of the car in action but I had no one to take any so some static shots will have to do. The first is of the car loaded on the trailer to make the trip to Helena (100 miles), the next is the pits for the event with my car and a 500+ HP Nissan and the Supercharged Atom, and the last two are of my car safely back home with lots of pick up from pulling off the course and over dirty pavement with hot tires.

 

Thanks to Siltech for helping make me quicker. Dennis went above and beyond the call of duty to answer the countless emails to get everything sorted out for my car.

 

The next race is next weekend. Hoping for sun and warm pavement! Thanks for reading.

 

Dave

[Kit Car Electronics]

Excellent! Was that +35mm each side to get front and rear track equal?

[Richard (OldStager)]

great write up, hope the season goes to plan. you will need to try and get some on track footage at some point, be great to see the car in action - i used to get my pit crew - such as they were- to film me whilst on a stage or run, you can learn a lot about the car and you by doing that, and slowing the video down helps to see what the suspension and tyres are really doing during a corner.

 

good luck for 2022.👍

[Dave Eastwood (Gadgetman) - Club Chairman]

Fantastic.

 

Incidentally, given your other thread, Siltech do some beautifully engineered Wilwood big brake conversions for the Westfield. I would absolutely be speaking to them rather than Rally Design, (given your way more specialist Westfield than the average one RD will encounter)

[Davemk1]

1 hour ago, Kit Car Electronics said:

Excellent! Was that +35mm each side to get front and rear track equal?

Very close - it looks as if the front is now about 12 mm narrower than the rear.

 

dave

 

 

[IainCameron]

Great work, Dave: very interesting to read and I look forward to hearing more as your season continues.

 

I'm not really familiar with Autocross, but managed to dig this out of Youtube from a while ago; is this the sort of course you're running?  Not sure if we have an equivalent in the UK, but it looks great!

 

 

 

[Davemk1]

1 hour ago, IainCameron said:

Great work, Dave: very interesting to read and I look forward to hearing more as your season continues.

 

I'm not really familiar with Autocross, but managed to dig this out of Youtube from a while ago; is this the sort of course you're running?  Not sure if we have an equivalent in the UK, but it looks great!

 

 

 

Well isn't that fun - not only is that the type of racing I do but that is the exact location of the race I did this past weekend. Good ol' Helena, Montana.

 

The course we ran this past weekend was set up much differently and was a bit more open and quicker but the video gives you a good idea of what it's like.

 

Good find!

 

 

dave

 

 

[IainCameron]

9 hours ago, Davemk1 said:

The course we ran this past weekend was set up much differently and was a bit more open and quicker but the video gives you a good idea of what it's like.

Hope you can get someone to video you and the course you run; 'a bit more open and quicker' sounds excellent!

[Andrzej]

Congratulations! time gap over supercharged Atom is significant ! (it was R4 2,4 honda supercharged ? I was on few trackdays with such equiped Atom and it was really quick)

 

Can You tell what ride height front and rear You set the car (weighted with driver)  ? and I am sure I have asked You but cant remember and find the exact post - front tyres on Your car are 240/580/13 the same as rear? Thanks! 

 

Would like to see pictures/ video of Your Westfield in action, maybe there will be photo-video stuff on next tackday/autocross! 

 

[Davemk1]

4 hours ago, Andrzej said:

Congratulations! time gap over supercharged Atom is significant ! (it was R4 2,4 honda supercharged ? I was on few trackdays with such equiped Atom and it was really quick)

 

Can You tell what ride height front and rear You set the car (weighted with driver)  ? and I am sure I have asked You but cant remember and find the exact post - front tyres on Your car are 240/580/13 the same as rear? Thanks! 

 

Would like to see pictures/ video of Your Westfield in action, maybe there will be photo-video stuff on next tackday/autocross! 

 

Good morning -

 

Yes the Atom is a supercharged 2.4L and it's tuned to run high octane race gas. I'm pretty sure it makes double the torque that my Honda 2.0L makes. It pulls so hard out of corners that it scrambles your mind.

 

I don't know the ride height with the race tires - ride height was set with the 206/60-13 street tires. The Avon slicks are 21 x 9 x 13 in Avon's nomenclature. I use the same size tires all around.

 

Does that make sense?

 

dave

[Andrzej]

Yes those k24 supercharged are over 400hp and lot of torque as this one I was competiting with.  

 

As for the grip - wonder how adding grip on the frond caused rear to be more grippy? -  if I understand right, by adding morte grip on front (Siltech widetrack ) , You was able to stiffen front ARB without loosing front grip too much ( which is normally the effect od stiffening arb on axle we are operating ) so the body of the car rolls less, and this less roll mean  rear more predictable, rear dynamic camber less change, and You was more confident with rear, so car is better balanced now ? or there is other explanation of how more front grip cause less tail-happy car behaviour ?, more confidence of the rear . 

 

[Davemk1]

1 hour ago, Andrzej said:

Yes those k24 supercharged are over 400hp and lot of torque as this one I was competiting with.  

 

As for the grip - wonder how adding grip on the frond caused rear to be more grippy? -  if I understand right, by adding morte grip on front (Siltech widetrack ) , You was able to stiffen front ARB without loosing front grip too much ( which is normally the effect od stiffening arb on axle we are operating ) so the body of the car rolls less, and this less roll mean  rear more predictable, rear dynamic camber less change, and You was more confident with rear, so car is better balanced now ? or there is other explanation of how more front grip cause less tail-happy car behaviour ?, more confidence of the rear . 

 

Here's my take and it could very well be wrong - I think that the wider front reduced front roll and therefore reduced the lifting of the inside rear tire.....which results in better grip in the rear.

 

The wide track front helps reduce roll so there is less need for the ARB to do. With this in mind the ARB I made is softer than the bar that was used with the narrow track front.

 

Does that make sense?

 

dave

[Richard (OldStager)]

23 minutes ago, Davemk1 said:

Here's my take and it could very well be wrong - I think that the wider front reduced front roll and therefore reduced the lifting of the inside rear tire.....which results in better grip in the rear.

 

The wide track front helps reduce roll so there is less need for the ARB to do. With this in mind the ARB I made is softer than the bar that was used with the narrow track front.

 

Does that make sense?

 

dave

sent you a pm.

[SootySport]

What you call Autocross in the States is Sprinting over here in UK. Here's our Pete in his Formular Ford. They use race circuits and airfields.

[Andrzej]

Autocross is rather different. Sprinting like this above is every time, every event on the same track-line, no cones, not tyre-made chicanes etc. Onre can nail to milimeters, know every disturbance on track, practice scenarions in turn-sequences, which turn is prioritete , begining of braking, apexes  etc. 

In Autocross every time is different. 

I drive on similar like @Davemk1 events, so interested in his experience. Especially how to stabilize rear, as there are many exists from tight corners where car is not settled down like on long fast turns onm real tracks. 

 

(on some events I attempt, there are often a photo-video crev and every driver gets his full record from all probes , good thing to see how tyres are contacting tamrac and how suspension work on bumps etc, example below. Would be great to see how is Your @Davemk1 Westfield behaving is similar conditions !