Vehicle dynamics

[Sam@TDi]

This sub-forum has been added as a place for us to explore the big picture of vehicle dynamics and it’s many considerations.

[Janey]

Excellent idea Sam

[Sam@TDi]

Excellent idea Sam

 

I think so so if anyones got any broad questions to start us off, fire away!

[Tony]

This sub-forum has been added as a place for us to explore the big picture of vehicle dynamics and it’s many considerations.

Fantastic evolution for wim Thank You Scarface, tdiplc and obviously Sam for supporting this area.

 

wim is like any classroom, a collaboration of people with different levels of understanding and knowledge, a good forum is an extension of this classroom with attentive wide eyed students willing to learn myself included.

 

Sam your TypeR we know you use the car for track days, what area of the dynamics did you find most challenging?

[Bazza]

maybe a little off topic

 

this type R of yours Sam

what have you done to it ?

 

interested to know what a man in the game does to his own car

 

 

not that interested in Marks corsa though

[TDIPLC]

not that interested in Marks corsa though

 

Are you dissin my chariot Barrie?

[Sam@TDi]

Ah my long suffering civic

 

Ok well I’ll give you the full story, I've owned the car from new for almost 4yrs and as you might imagine given my field of work it's had all manner of different parts bolted on to it and taken off again in that time.

 

Although the engine was previously quite modified the only power related modifications now are an enlarged throttle body, an after market and much bigger exhaust B'pipe and a completely re-designed intake manifold separated from the cylinder head by nylon spacer (I was trying out a pressure wave tuning calculation based around the Helmholtz tuning method, it worked!) the last time I checked the car measured just under 190bhp at the hubs on our Rototest chassis dyno.

 

The chassis it’s self is fitted with stiff engine and gearbox mountings, uprated brakes, a Tein type Flex coilover suspension system and a very experimental front trackrod end solution.

 

With regards to the chassis dynamics, it was immediately apparent to me that Honda had compromised heavily in the suspension design on the UK EP3 Civic Type-R choosing to run with almost no static geometry at all and using softer linear rate springs than they had chosen for the Jap model. They had tried to address the cars intrusive natural under steer departure with the anti-roll bar rates. Whilst this meant the car was very capable at the grip limit in a steady state turn condition on a dry surface, the transient movements (before the anti roll bars loaded) were seriously unnerving and in the wet when you're almost totally unable to load the anti-roll bars the under steer was horrible.

 

The Tein type Flex kit has much stiffer spring rates which appear to be pretty well developed straight out of the box. Taking a portion of the tyre load control away from the anti-roll bars means that the difference in balance from dry to wet weather is reduced and the car feels much more predictable and linear in response through all transient situations.

 

After fitting the type Flex and lowering the ride height considerably over that of the standard civic, the car developed an annoying bump steer habit, obviously Honda had built in a “tow out on bump” characteristic to the front suspension which is by design “rising rate” in nature and I was now operating in the top end of that scale. The answer seemed simple, change the height of the TRE in relation to the rack, in reality deciding exactly what height I’d like that “new” height to be has been fairly tricky but I think I’m pretty close now.

 

I’m by no means finished playing with it yet, at present the car feels very balanced at full throttle but actually quite loose at steady throttle. I want to balance out this aspect next

[Tony]

Ah my long suffering civic

After fitting the type Flex and lowering the ride height considerably over that of the standard civic, the car developed an annoying bump steer habit, obviously Honda had built in a “tow out on bump” characteristic to the front suspension which is by design “rising rate” in nature and I was now operating in the top end of that scale. The answer seemed simple, change the height of the TRE in relation to the rack, in reality deciding exactly what height I’d like that “new” height to be has been fairly tricky but I think I’m pretty close now.

 

I have read this post about ten times 'IT'S' fascinating! .... But i will always have questions Sam that's how we learn... The under-steer characteristics derived from a FWD car you have addressed by lowering the COG and limited the roll centre to enhance the corner 'ON' arb loading. Would you not also consider a means to adjust the castor so the the inner wheel during the camber/castor transition has a longer trail? We both know the R naturally has near to no front camber (this you have addressed) and near to no castor, so in my mind the corner values must be incorrect.

Also I'm confused the steering arm on the R is mounted on the cars upper parallelogram, so it's radius is not governed by the radius of the lower control arm (within reason) I am surprised the problem is such an issue that you need to find a means to resolve the 'bump-steer-on', could the lack of castor trail during the weight transfer and obvious suspension loading be the problem?

 

Please don't reply and just say 'NO'

[Sam@TDi]

I agree on adding some caster angle, as it happens that is exactly what Honda themselves did when they face lifted the EP3 Civic after almost every motoring journo slated the Type-R's lack of steering feel, i've had a look at doing it in the past but unfortunately it's not going to be straight forward with my current set-up.

 

Regarding the TRE's, the track control arms were running close to 45degrees at normal static ride height. It was purely that the arm was effectively shortening alot during a bump event that was causing the problem. The arm's are now operating at a much more shallow angle now and the problem is all but solved, better than the standard car i'd say

[Tony]

I agree on adding some caster angle, as it happens that is exactly what Honda themselves did when they face lifted the EP3 Civic after almost every motoring journo slated the Type-R's lack of steering feel, i've had a look at doing it in the past but unfortunately it's not going to be straight forward with my current set-up.

 

Regarding the TRE's, the track control arms were running close to 45degrees at normal static ride height. It was purely that the arm was effectively shortening alot during a bump event that was causing the problem. The arm's are now operating at a much more shallow angle now and the problem is all but solved, better than the standard car i'd say

Maybe we can work on that castor issue? I am struggling with steering arm position 45d supports quite a suspension compressive curve without alteration, how low is your car now from stock?

 

Also (i said i would ask questions) If you could display the front camber positions then we can work out the camber/castor values for corner (on) by degrees.

[Sam@TDi]

Yeah definately now you've mentioned it i'll take a good look at the front of the Civic and see how much movement I can find us.

 

My car is alot lower than stock, the rack is way way too low even in the standard type-r I think it's a legacy of the cars shopping trolley roots

 

I don't know if you'll agree but just reading back over this thread I think it'll be easier for some people to follow if we try to resist the temptation to use abbreviations like COG, ARB, TRE, (on) etc... even if it does make things a little longer

[Mark H.]

Centre of gravity, anti roll bar, track rod ends, ((oh no), where'd all my money go)?

[Tony]

Yeah definately now you've mentioned it i'll take a good look at the front of the Civic and see how much movement I can find us.

 

My car is alot lower than stock, the rack is way way too low even in the standard type-r I think it's a legacy of the cars shopping trolley roots

 

I don't know if you'll agree but just reading back over this thread I think it'll be easier for some people to follow if we try to resist the temptation to use abbreviations like COG, ARB, TRE, (on) etc... even if it does make things a little longer

I know wot u mean Only kidding...... Indeed i was a little carried away knowing you are receptive to the abbreviations, and as you rightly say this is not professional to the observer.