LS Coupe on the scales

[STLMARSHALL]

I finally found the time to set up our club's Intercomp scales to find out what all my work did for me. I still had my R-comps on from the last race so the numbers are a little skewed as the race tires are 11.5 lbs each lighter than my street tires.

Here are the new numbers vs old:
Total weight: 2260 vs 2427
F/R % 48.9F/51.1R vs 45.8F/54.2R
L/R % 49.6L/50.4R vs 49.7L/50.3R

New numbers were taken with no driver, no gas (trying to ensure I can't bust my minimum weight limit for XP), and race tires. This simulates a worst case senario of rolling into the pits and onto the scales at a national event low on gas. With the 5.7L LS1 my minimum weight limit for XP is 2226 lbs. This means I have a 30 lb buffer as I roll into impound even with no fuel.

It appears my efforts were sucessful in shifting weight towards to 50/50 goal and the weight loss is right on target. I plan to lose a little more weight and use a reasonable fuel load to "make weight". While the 3% weight shift did not totally cure my oversteer issues, the car does feel much better balanced and will be faster once I adapt to the new feel.


I got the cross weights all set now. I ended up at 50/50.

LF/RR 1221 lbs
RF/LR 1216 lbs

I went 1/2 turn on all 4 corners to get it set. I calculated that on Konis 1/2 turn on each shock changes the cross weights by about .4%. I 1st did the RF/LR (1/2 turn each tighter) and the cross weights changed by .8% in the right direction. I then did the LF/RR 1/2 turn looser and it changed by another .8%. Just a good rule of thumb we can use in the future!

Comparing the weights to the scaling we did last year I took 150 lbs off the car which nearly all of it was off the rear. The front weight is nearly identical.

Front weight old/new - 1161/1158
Rear weight old/new - 1431/1280

[LDave]

Very Cool! This can help give me a rough idea of what mine weigh's :-)

[jkrueger]

how far did you move the engine forward?

JC

[STLMARSHALL]

Depending where you measure it, 1.5 - 2.0". Because it is a different engine it appears on the motor mounts like it moved 2", but the driveshaft was lengthened 1.5". A friend let me borrow a bare aluminum LS block which really helped in mocking up the new placement.

[Chris C.]

Is there a build thread on doing LS motor installs in coupes?

[jkrueger]

Is there a build thread on doing LS motor installs in coupes?

Here is some information on my LM7 installation in my coupe. I used the engine mounts that Fortes sells.

http://thefactoryfiveforum.com/showthread.php?6954-Engine-test-fit-on-coupe-567

JC

[STLMARSHALL]

Here is my thread when I rolled out my conversion to the LS engine. Post #2 has the part #'s of what I used. Good luck Chris.
http://www.ffcars.com/forums/21-ffr-type-65-coupe/287666-new-engine-my-coupe.html

Mike

[CHOTIS BILL]

Mike,

How is the oversteer now that you have more front weight? Another thing you might check into is raising the rear roll center. From FFR the IRS rear roll center is actually lower that the front and it should be higher. Changing it on my DSR made a big difference.

Bill Lomenick

[STLMARSHALL]

Bill the oversteer is better with the 49/51 balance. It now comes on more slowly and gives you a chance to slow or countersteer some where before it just broke suddenly. I am going to run a test and tune sunday to see how far I can push in certain elements before it spins.

How do I change the roll centers on the FFR 3-link??? I am willing to give it a try but unsure how to make the changes.

[Mike N]

Mike.

The roll center with the FFR 3 link style rear end is in line with the panhard bar pick up point on the axle. I have a watts linkage on mine not a panhard bar and have found that having the roll center either in line with the center line of the axle or perhaps 1 inch below it works very well for my set up. The FFR set up puts the roll center 4 or 5 inches below the axle center line. Being able to move the roll center easily is another good tuning tool.

[CHOTIS BILL]

Mike,

I don’t know why but I was under the impression you had IRS. To change the roll center it is a matter of changing the pickup point heights. I don’t have any information on the 3-link but if you send me the X, Y, and Z location of your pickup points I will see what I can do. From other posts the Gordon Levy 5 link system seems to make for the best handling solid axle setup and is well worth the money

Bill Lomenick.

[STLMARSHALL]

Thanks Bill and Mike for all the info. The 3-link has very little adjustment so I am not sure there is much reason to spend too much time on it. I have a friend that just built his own 5-link. I may grab his plans and build my own for a winter project.