calling v8 powered racers, looking for a little guidance Options

[returf]

I know there are a few of us with v8 powered 914 racers so I will put this to you for any info you may be able to help me with. With my first test sessions, I felt as if the rear of the car wanted to come around on light throttle through transition in corners. I have toe in on the rear and toe out (1mm total) on the front. Great turn in. My track was 90 mm wider at the front than the rear so thinking this was contributing, I modified the front suspension today to narrow the front track and are now sitting 30mm narrower at the front than the rear. I'd be interested to hear from others as to their set-ups. ( if its a real secret you can PM me haha. Any help from guys with a similar setup would be appreciated

[veekry9]

What have you done to stiffen the chassis?From new the car was noted by many testers as a flexiflyer.
The loads are now greater and the original floorpan allows the front and rear to flex relative to each other in a larger magnitude.
As a racer,no doubt you have installed a rollbar that may have firmed the torsional resistance to some degree.
The measurement of the torque needed to deflect the spring perches is a good first step.
Loosy-goosy will have the 914 squirming around the track and exhibiting the bad habits many here have experienced too.
How stiff?Enough to have control and no more.Then you can win.

http://avaxsearch.org/?q=Chassis%20enginee...%20Herb%20Adams
http://www.amazon.com/Herb-Adams/e/B001K8LH8U
http://blog.caranddriver.com/50-years-in-t...ssa-sports-car/
http://www.chevyhardcore.com/features/not-...cheverra-racer/
http://bringatrailer.com/2014/11/26/herb-a...-speed-project/
https://www.youtube.com/watch?v=V5xgglhqEWg

As a racer,you have no constraints as to how robust the longs are and how many crossmembers the floorpan has.
Have fun.Have a moment of inertia.
SouthernCross.

[Mike Bellis]

We need to know more about your setup. Wide body or narrow? Tire size? Spring rate? sway bars? engine type? has the car been balanced? stiffening kit or roll bar?

Oh and...

(IMG:style_emoticons/default/thisthreadisworthlesswithoutpics.gif)

[returf]

OK. the car is widebody, but will now be slightly narrower at the front after yesterdays modification.It runs a turbocharged LS1 /subaru 6 speed combo. 18x10.5 rears and 18x9.5 front with slicks



it has a full cage, front tower to rear tower and strengthened trailing arms ect. ARBs front and rear fully adjustable

[returf]

If you had the time , I have a build thread from when I first started the project over in club/paddock that would show more detail but let me know what else could be helpful for you guys to see that could shed some light on what I may have done to cause this. As I would really like to know if that track difference may have caused it.

[veekry9]

Neato.
Triangulated DOM tube cage that ties into the spring perches and trailing arm pivot.
The bottom of the cage is tied into the longs with rectangular feet to spread the load to the sheetmetal.
It appears that the inner longs have been doubled with braked sheetmetal angle to add stiffness.
Transverse tubes tie the front of the cage at the top and bottom windscreen height.
I assume the cage was tested for torsional stiffness prior to installation.
I am seeing a single tube running forward from the cage.
https://www.google.ca/search?q=full+race+ro...ved=0CAYQ_AUoAQ
A look at the trailing arms should reveal a heavily modified pivot tube and box section,tho the inner console appears to have no doublers.

What brand of LSD do you use in the Soobee6 TX and at what load does it lock up?
The turbomotor is an impressive V8.Inconel exhaust valves?What pressure is it limited to?I am liking it,have you drysumped it with a wide pan?
https://www.google.ca/search?q=drysump+oil+...ved=0CAYQ_AUoAQ

Have you mounted cams to study the chassis in race conditions?A good ytub of a few races would demonstrate the chassis's dynamics.
I'm laid up with a buggered knee and have all kinds of time to do things I like doing.Such as lurk on motoring boards and scribble in the sand.
I gotta ask tho,what class are you running,it looks all-in and making some big power.
http://www.tauporacetrack.co.nz/
Is there enough dough there to run a simulation of the tracks you run at.Do you have any hard data?
Your ecu is pumping out the engine streams,consider mapping the chassis.
Where is your centroid of mass?How does the racer balance.Roll centers front and back and the camber gains.
http://www.fiero.nl/forum/Forum3/HTML/000116-30.html
Some details of geometry.

[ChrisFoley]

Add 30mm more rear tire to the outside to fix the track width problem.
(IMG:style_emoticons/default/smile.gif)

[r_towle]

Arbs fully adjustable? What is that?
Have you corner balanced the car?
Anti sway bars?

Spring weights?

Shocks adjustable valving?

[Mike Bellis]

Based on the offset of the front wheels, you have spacers thus increased scrub radius. This will affect handling quite a bit. Try to remove or reduce the spacers in the front and hit the track again.

[Chris Pincetich]

most of the best race car tips get shared in the forum called The Paddock (IMG:style_emoticons/default/beerchug.gif)
Cool pics (IMG:style_emoticons/default/aktion035.gif)
too much oversteer accelerating (V8!), always, or just decelerating?

[drive-ability]

Nice Car !
Nice to see the club members helping out. I will need this type of assistance in the future. (IMG:style_emoticons/default/drunk.gif)

[messix]

less rear bar.

or less rebound dampening in rear shocks. check this http://www.bimmerhaus.com/tech/shocktuningTN.html

or softer rear spring.

you need some weight transfer to the outside tire.

you might try adjusting rear ride height a bit.

only try one thing at a time

[returf]

Veekry9;The inner console does have doublers as well as the outer console and the shock towers.
It is running a Suretrac Helical diff. these are a tourqe biasing diff( not sure of the load required to lock up though. The engine is an LS1, pretty much standard except for fuel system upgrade, running stand alone computer, 7lbs boost, 520hp at the wheels, using an accusump to protect the engine. I have done the youtube thing but not on the chassis as yet.

Racer Chris; haha. the good thing about narrowing the front is that now it will fit on my trailer easier

Rich, ARB = anti roll bar. I have a blade adjustable bar at the front and a hole adjustable bar at the rear. spring rates are 6kg/mm and 8kg/mm

Mike; I'm not running spacers, I installed mcphearson struts from a Nissan sylvia. Anyway the front turned in well, Everything I've done to the front end will have altered the scrub radius, but this would'nt affect the rear to any degree.

Chris P.; problem only on trailing throttle midway through the corner.

Drivability; with your setup you can at least get info straight from the spec boxter crowd or the cup car teams (IMG:style_emoticons/default/w00t.gif)

[returf]

less rear bar.

or less rebound dampening in rear shocks. check this http://www.bimmerhaus.com/tech/shocktuningTN.html

or softer rear spring.

you need some weight transfer to the outside tire.

you might try adjusting rear ride height a bit.

only try one thing at a time

Darn I should have posted this before I went and altered the front to try and fix the rear problem (IMG:style_emoticons/default/hissyfit.gif)

[Downunderman]

Its all in the diff. That's where I would be looking.

[ChrisFoley]

...
spring rates are 6kg/mm and 8kg/mm
...

That's roughly 325 lb/in and 440 lb/in.
Have you calculated the wheel rates?

McPherson strut wheel rate is lower than the spring rate; trailing arm wheel rate is higher than the spring rate.
Therefore, on a 914, the higher rate spring is at the front.

[veekry9]

Its all in the diff. That's where I would be looking.

(IMG:style_emoticons/default/agree.gif)

AWD/FWD vs RWD track 914 why it steps out.

http://www.trak-life.com/basic-introductio...ferentials-lsd/

https://www.google.ca/search?client=ubuntu&...HNcnz8wfD2YCQCQ

A solution may be found by drifting the corners,letting it all hang out,full tilt.
Do not go gently ....smoke em.
(IMG:style_emoticons/default/happy11.gif)

[returf]

...
spring rates are 6kg/mm and 8kg/mm
...

That's roughly 325 lb/in and 440 lb/in.
Have you calculated the wheel rates?

McPherson strut wheel rate is lower than the spring rate; trailing arm wheel rate is higher than the spring rate.
Therefore, on a 914, the higher rate spring is at the front.

Sorry, i should clarify that. 235lb for the rear and 440lb in the front. It had no problem hooking up and getting traction under power

[Mike Bellis]

Did you have the car corner balanced?

[returf]

Did you have the car corner balanced?

Just roughly Mike