Fox / SN95 SBF engine setback

[tulowd]

An SLA with 10" wheels n 275's up front would make it a monster.

Grrrrrrrrrrr lol

Spoke to MM about their SLA plans:

S197 version is in development/track usage now - app 1 yr until on market
SN95/Fox SLA may follow depending how much carryover they can use from above and the integration with their existing K members and feeling about return on investment.

Reading between the lines, I would expect a S550 SLA to be made available shortly after the S197. (my intuition, they said nothing and I didn't ask).


Having said that; lots of fast cars use strut suspensions - M3's Porsche 911/Cayman etc.

The $9000 USD price tag for a Griggs Fox SLA road race setup is enough to make me dream of an all alum 427 engine set back 15 "

http://www.griggsracing.com/article_...?articles_id=8

http://www.griggsracing.com/index.ph...08c5ad6a49273f

[RedSN]

sort of but its a different number and calculation based on centre of gravity as the basis; not the direct weight on the wheels. Aircraft calculations are done via wheel weights but the differentials are calculated using moment arms and mass.

Moving the engine/tranmsission back 1" changes the weight distribution 0.2% on your car. I've used your cars mass of 3,741lbs and assumed that the engine/trans weighs 600lbs. The formula that you linked isn't the correct one. The correct math can be found at the link below in chapter 2.

A 0.2% weight distribution change on a 3,741 lb car = 7.5 lbs

I was off by 1.5 lbs
....assuming Jack didn't round up his results

[tulowd]

A 0.2% weight distribution change on a 3,741 lb car = 7.5 lbs

I was off by 1.5 lbs
....assuming Jack didn't round up his results

I want to watch you two argue engineering calculations about my overweight, underperforming, underpowered old shitbox!

I thought a weight distribution change is different than a distribution percentage change. I was wrong.

Current
3741# TTL
1011+957 = 1968# Front = 52.6%
910+863 = 1773# Rear = 47.4%


Change by 0.2%
F52.4%/ R47.6%
F = 1960# (less 8#)
R = 1781# (plus 8#)

Hmmm - ok - good to know 2 smarter guys than me agree on this.
1) Now what happens when I lose 50# off the front/top of the engine, knock 50# off the rear (no ballast) stock engine location.
2) Then move the engine back while saving 30 lbs with the k member, same wheelbase
3) Then extend wheelbase and widen front track by 1.5" respectively, ttl weight remains the same.
4) Lastly knock off 40 lbs for lighter wheels

Have at er !


PS: This also magnifies any small changes that can be made like losing anything in front of or behind the wheelbase in order to reduce the polar moment(s) of inertia. Need that alum rear crash bar!!

[RedSN]

Now what happens when I ....

too many variables, not enough information.
my initial calc was based on some assumptions and using a simple beam reaction formula to illustrate the effect of moving a 600 lb iron slug back 1"

[HyperGT]

Grrrrrrrrrrr lol

Spoke to MM about their SLA plans:

S197 version is in development/track usage now - app 1 yr until on market
SN95/Fox SLA may follow depending how much carryover they can use from above and the integration with their existing K members and feeling about return on investment.

Reading between the lines, I would expect a S550 SLA to be made available shortly after the S197. (my intuition, they said nothing and I didn't ask).


Having said that; lots of fast cars use strut suspensions - M3's Porsche 911/Cayman etc.

The $9000 USD price tag for a Griggs Fox SLA road race setup is enough to make me dream of an all alum 427 engine set back 15 "

http://www.griggsracing.com/article_...?articles_id=8

http://www.griggsracing.com/index.ph...08c5ad6a49273f

I would just do the heads and Kmember personally. Until you get to a point where you are wanting that last 10th or three of lap times its is not worth it. Unless of course you just want to have a unique car and fun project, then go at it.
Not sure what 911 has struts, 1999 forward at least was coilover design (over a strut if that is what you mean) but they were not separate strut and spring suspensions thats for sure.

[tulowd]

too many variables, not enough information.
my initial calc was based on some assumptions and using a simple beam reaction formula to illustrate the effect of moving a 600 lb iron slug back 1"

lol...what else do you need to know mon ami?

110 lbs of ballast were in the trunk, this will be reduced by 50 lbs to 50 lbs of audio equipment only

new cyl heads will knock 50 lbs off front of engine/trans assembly; lets say 550 lb ttl mass for engine, flywheel clutch, scattershield and trans

new k member and arms will knock off 30 lbs from existing front weight


this will keep ya busy in between thinking/planning about your garage; lol

I just hung a pair of 16" high bay 84W compact fluorescent fixtures in my car shelter - looks like the entrance to hell at night from the street now

[HyperGT]

Dont forget bigger tires and rims will add back alot of weight to the front. I just put speedline 17 inch with 275/245 on my car and the difference was huge compared to my 225/16 setup. I mean I can really feel the weight, car feels sluggish. Rotating mass is 3-4x that of regular static weight.

[tulowd]

Dont forget bigger tires and rims will add back alot of weight to the front. I just put speedline 17 inch with 275/245 on my car and the difference was huge compared to my 225/16 setup. I mean I can really feel the weight, car feels sluggish. Rotating mass is 3-4x that of regular static weight.

current setup is 50 lbs / corner with 255/40/17 on 17x9 Cobra R's
10.5's with 275/40 adds app 2 lbs per corner to 52 lbs

switching to Enkei 10" wide wheels will reduce weight by 9 lbs per corner back down to app 43 lbs per corner with 275/285 tires

[1BAD92LX]

I agree with HyperGT. But I know your not a person to settle.
I've done the MM k member and it feels so much stiffer. I went with reverse offset arms to not have to mess with fender clearance. Delrin bushings also.
I can't wait to put aluminum cylinder heads on and cut off some more weight. Just which ones is the question now.

[tulowd]

From Jack Hiddley at Maximum Motorsports:

1) Moving the engine/tranmsission back 1" changes the weight distribution 0.2% on your car. I've used your cars mass of 3,741lbs and assumed that the engine/trans weighs 600lbs. The formula that you linked isn't the correct one. The correct math can be found at the link below in chapter 2.

http://www.faa.gov/regulations_polic...-h-8083-1a.pdf

Conversely moving the wheels forward 0.75" will shift the front weight distribution 0.39% towards the rear. Moving the front wheels forward has more affect on the weight change and has other benefits.

With the MM k-member and either FCA, you will be able to get a little bit more camber. With the MM k-member and nonoffset FCAs, you will be able to get several more degrees of caster and a little bit more camber.

The MM k-member adds Ackermann steering when used with the nonoffset FCAs. When used with the reverse offset FCAs it removes Ackermann. In either case, the k-member raises the FCA pivots so this raises the roll center height back up which is good on a car that is lowered so much.