Civic Sedan Build - JTCC Inspired

[Grant@Honed]

Cool man, I'm keen to check it out!

I'm going to try push through another round of suspension development in the next month so ill probably miss July and aim to enter an event sometime in August.

[felixR]

Great work with the DC2 so far Keep it up.

[Grant@Honed]

Thanks for the encouragement! There's more to come

Since the track day my brakes have been a little soft and lacking in bite. I did feel some pad fade during the track session but i'm not familiar with what long term effect that has on a car's brakes.

I've ordered some super blue brake fluid and will get that bleed through the car in the weekend. Hopefully that brings back my pedal feel otherwise ill have to sort out some new pads as well.

I've got an interesting update on the way, i'm just taking my time to get everything straight before i post it up. Here are some teaser pics!

[ChargeR]

I like it mate, getting serious. When's the K swap coming?

[Grant@Honed]

So last week I posted a couple of screen shots from Susprog3d a cost effective Suspension analysis program I have used to model the Dc2’s suspension.

I’d like to tell you I used a co-ordinate measurement machine to measure all the points, (I did briefly consider it) but in the end the measurements were taken with tape measure, steel rule, string line and steely eyeball.

I’m confident the dimensions are accurate enough for my purposes and that the model truthfully represents the dc2 suspension

The dc2 runs double wishbone suspension up front with a unique trailing arm set up in the rear that features a camber arm, lateral link and a forward toe arm.

You can see these features are represented in the suspension model.

Susprog doesn’t have a polished user interface and requires the user to do a bit of work to get the information presented in useful form.
The benefit of this is that you have the flexibly to plot the data anyway you like.
I’ve now got Camber, Toe and Roll Centre data for the front and rear suspension and this information will help reduce the confusion when ironing out handling issues.

My main motivation for measuring up the DC2 was to investigate roll centre placement and find out what the roll axis is up to with changes with bump and droop.

It was this photo of my car at Haunted Hills combined with my experience in the car at Winton that kept nagging at my inner Engineer to find out what the car is doing



I’ve put the next three images together to illustrate what I found

At near stock ride height the factory roll centre front and rear are both well above ground level and the roll axis slopes downward toward the front of the car. This is generally accepted as the desirable set up for predictable handling



I found that as ride height was reduced the roll centres moved downward with the rear actually having greater vertical movement (due to the arch of the shorter links) this results in an almost flat roll axis at ride height.

If you look at the pictures of my car you can see that it is not excessively low yet that car is what i based my "lowered" ride height on.



The problem occurs when the car goes into bump. The front RC plunges below ground level and leaves us with a long roll couple. Roll couple being the distance from the car's centre of gravity to its roll centre



White DC2 Pictures Originally from www.Fastcar.co.uk

In simple terms the greater the roll couple the lower the cars roll stiffness (geometrically).

If you’re having trouble following me, check out the link below.

https://www.youtube.com/watch?v=bLcDN-qCpYI#t=04m39s
Video of DC2 competing in Swiss Hillclimb 2013

In the video the dc2 is comes into the right hander heavy on the brakes, all the weight is transferred to the front and the front suspension is compressed in bump. As the driver turns in, the car pitches about its roll axis, overloading the front left. This contributes to the car understeering and delays the driver from getting back on the throttle. For the sake of this discussion let’s not argue over driver technique.

The relationship between the centre of gravity of the car, its roll centre and roll couple is shown in this handy diagram I have borrowed from elsewhere on the web.



Now what?

Well I can buy front roll centre adjusters from Hardrace or Mfactory or J’s which is great and i’ll be picking some of those up in the next week or so.

The problem is, if you just increase the front roll centre, you will end up with an inclined roll axis toward the front of the car.

I think maybe the reason roll centre correction parts get mixed reviews on the forums is because although they reduce the roll couple across the front axle the resultant car is unbalanced

I believe the common practice of running high rear spring rates on Dc2 is reflective of this.

My plan:

I can correct my rear roll centre by modifying where the rear LCA mounts to the rear upright

I brought myself a set of trailing arms and measured them up



I have designed a weld on bracket to drop the outer LCA mount



While I’ve got the welder out I figured I might as well gusset the inside of the trailing arms to increase their stiffness.



The removable plate is there to enable the handbrake cable to be fitted

Everything is ordered and I should have the trailing arms fitted sometime in the next few weeks.

I could be totally wrong about everything, after all thousands of people have been campaigning dc2s in all forms of motorsport all over the world with no issues. This is just something that I find interesting and it will be satisfying if it works.

Thanks!

[Grant@Honed]

In the past week i've tidy'd up a few interior items that had been bugging me.

I removed the factory clock for the last track day. I figured that with a time read out on the headunit, GPS and my phone I can live without a dash clock. I want to keep the car presentable so I fitted a ITR clock delete panel.



I removed the rear seats for the track day as well, i've decided to leave them out permanently and will probably get a filler panel made up to level out the boot shelf and protect the top of the fuel pump. I will then get a new piece of carpet made to cover the whole lot.



I laid this heat reflective/sound deadening product over top of the seat base panel to try and keep the noise of the fuel pump to a minimum



I've changed the rear section of the console to the type R version in preparation for new seats



I brought a Type R boot bar under the impression that the Vtir chassis had the provision to mount one. It turns out they don't. With a small modification I mounted it slightly further forward onto the rear "chassis rails"

[Lonewolf]

good idea on the filler panel, might do that with my EG

[Grant@Honed]

Gusset plates have arrived, I should have the LCA plate in the next day or so. Hopefully i'll have pictures of the finished trailing arms this weekend

[ChargeR]

Great work mate, but as I said in person you should be cutting stuff off your rear trailing arms not adding it on . Here's the SS Works car I mentioned:

[Grant@Honed]

Wow look at that brake rotor!

Don't get me wrong I'm all for weight saving, just in the right areas.

Suspension components need to be stiff, it's difficult enough to tune toe and camber with suspension geometry, we don't want to be chasing ghosts because things are flexing.

[Grant@Honed]

I found a picture of my twisted upper control arm, a parting gift from the Haunted Hills track.

[Grant@Honed]

Here's a teaser shot of the RTA with the fabrication complete!

[Grant@Honed]

Over the weekend I completed the modifications to the trailing arms.

Here you can see how we stitched the trailing arm gusset to the inside of the OEM RTA.



I mocked up a trailing arm with the hub and brake installed to check the routing of the handbrake cable. I found that i could squeeze the handbrake cable into place even with the "bolt on gusset" installed, to keep it easy i decided to change the design to one piece and just weld the secondary plate on for my trailing arms. I've refined the profile and plan to get a few extra sets made up.



The relocation of the LCA mounting point worked out really well.

I've got the RTA's masked up ready for sandblasting on Monday. I'll be getting them powder coated gloss black and should be pressing the new bushes in at the end of next week!

I've ordered a set of the Mfactory extended balljoints for the front knuckles

I'm well on the way to having my suspension geometry sorted out, i'm starting to get pretty excited about testing the new set up!

[ChargeR]

The relocated lower pickup point looks great mate, set aside a set for me . Looking forward to seeing how you go with all your revisions to the suspension geometry, if nothing else a fresh set of RTA bushes will make a massive difference.

[Grant@Honed]

A bit of a tame update today,


I got the RTA's sandblasted and powdercoated during the week. Today I replaced the RTA bushes with OEM rubber items.

I'm really happy with how the RTA's have turned out. I'll take some clear photos when I get the chance.

I took the opportunity to measure the RTA with the co-ordinate measurement machine, i love this thing!



The CMM allows the operator to measure anything within it's working volume to 0.1mm.

I have imported the points to SW and will update my geometry in Susprog with the more accurate dimensions for the RTA. I super imposed the new points over what I measured with the tape measure and was happy to see most points lined up.



The Mfactory front ball joints haven't arrived yet, this has given me time to arrange a few other jobs while I have the front suspension apart

I've made the decision to replace my front wheel studs and wheel bearings while I have the knuckles off.

The impact that bent the left side upper control arm also bent the top of the knuckle so i'll be replacing that entire upright.

I've acquired a set of stainless cv boot clips and plan to strip the front axles down, clean everything, then rebuild them with Redline CV-2 high temp CV grease.

Here's the plot of Toe vs Wheel travel for the front wheel, with the standard suspension geometry lowered to my current ride height (ie not super slammed). Toe in is to the right hand side of the vertical axis.



You can see the wheels toe in as soon as the front suspension goes into bump. Generally FWD cars like a bit of toe out on the front as it reduces understeer and makes the car more sensitive to driver input.

We can align the car with static toe out but going too far can cause the car to be twitchy under brakes and darty on the straights at high speed.

I'm going to try find a set up where I can get the car to toe out in bump so I can run minimal static toe out.