EP 914-6 How low can I go? Options

[neilca]

Chris,

You are correct, my car is way beyond EP prep. I used EP in the title because it could be recognized. I will be running a special regional class in the SE called Special Production Under 2.4 liters (SPU). Basically, the only rules are it has to be under 2.4 liter and not fit another class.

I have not heard of raising the pivot point of the trailing arms. I would guess that would have been a good thing to do when the car was on the rotesserie. Could you elaborate on what you have done? I have followed, with great interest, your work with horizontal fans. I originally set up my chassis for a 4 cylinder. I found a deal on a 6. That is why my engine mount plates have spacers in them. If I could run a horizontal fan I could loose the spacers and move the weight forward.

Terry,

Thanks for the kind words. I think I enjoy building cars more than driving them. When I retire that is my plan is to tinker on race cars.

The burn marks are from tires I used last year that where 3 inches too tall. At least they were free! They gave me something to ride on while I sorted out the car. This year we use free slicks from some friends in the National circuit.

I hadn't heard of lengthening the arms to get more negative camber, but that is a great idea. If you run radials that would really pay off.

Our local SCCA region is planning on having more Time Trials this year associated with Nationals and Regionals. I will take advantage of this to get some track time, tire temps and travel data.

Based on what I have read so far I should set my ride height in the front such that my lower control arm is parallel to the ground and the rear I am thinking should be about 3.5 inches off the ground.

[ChrisFoley]

In the northeast most of the SPU cars are 7/8ths pro-stocks or Baby Grands.

Raising the rear pickups can be done several ways. Starting with a chassis jig is nearly essential when doing it from scratch. Some people have moved the stock mounts but the amount one can raise them is limited. Others have developed complex spherical bearing mounting arrangements that are expensive and time consuming to implement. I developed an economical kit that makes it a pretty straightforward procedure to go up as much as 3", retaining the stock trailing arms. It can be done with the chassis set level up on jackstands. The instructions are on my website and are linked on the chassis page.

As I mentioned, there are many benefits to rasing the rear pickups. In conjunction with altered trailing arms it is possible to lower the car drastically and obtain very good rear suspension geometry. On thing I didn't mention earlier is the benefit to the toe curve.
With your current setup the toe changes pretty quickly in both bump (toe-in) and droop (toe-out). On my car the toe hardly changes through a 6" range of 3" up and 3" down.

I keep saying I will finish development of the horizontal fan, then putting it off again. All that is holding me back is that I don't like the shroud design that was provided to me. So I just need to create a shroud I like and the rest will be cake.
I actually have all the primary parts to build one more just like the two I have on my race engines.

[neilca]

I have set the ride height. I decided the rules dictate how low to set the car. I put a rim on the LF corner with no tire, simulating a flat tire condition. Lowered the car to the ground and set the ride height such that the lowest point was 1/2" off the ground. Put the regular tire back on and measured 2 3/4" from the jack nub ( this is the boss on the bottom of the tub in the four corners). I then set the rear to 3 3/4" in the rear to give the car some wedge for down force.

Now on to corner balancing, see post on the subject.

[stownsen914]

Raising the rear pickups would solve multiple problems:
Shock travel would increase;
Trailing arm would have more clearance to the underside of the chassis;
Less spacers needed to get desired camber;
Lower rear roll center.

Chris - from some playing I've done using the susprog suspension design tool, raising the rear pickup points raises rear roll center. You have found differently? Of course, you get other benefits by raising pickup points by bringing the arm closer to its intended range of motion ...

CG vs. Roll Center: THE GREAT QUESTION, from what I have experienced, the Roll Center is the more important issue and the LOW roll center will continue to give you handling problems.....

Usually a low roll center is considered desirable. You still have to balance it with other parameters of course. Have you had positive experience in aiming for high roll centers?


Neil - great looking car. I remember seeing the spread over on Pelican a while back.

Scott