johnc

Dang, I searched using "R180" and "HORSEPOWER" and found two threads on the first page that pretty much answer your question. This thread is closed.

I was kinda hoping the smart guys wouldn't reply right away... This from Mark Ortiz go me thinking that some other folks might have a misunderstanding regarding load transfer:

Let's keep it simple: purely lateral acceleration; no bumps; no banking; no geometric anti-roll or pro-roll; no aerodynamic downforce, no unusual roll centers, perfct CG, etc.

Assume the following: 1. 2,000 lb car with a 50/50 weight distribution (500 lbs. of static load on each corner). 2. 8" tall 250 lb. in. springs at all 4 corners. 3. No aero downforce or lift. 4. No anti-roll bars. What is the load on each tire and what is the height of each spring at 1G lateral acceleration? Can the car generate more then 1G lateral acceleration?

IMHO... The rear braces supporting the main hoop exist to keep the main hoop from racking forward or back. More horizontal rear braces improve that protection but they also give a greater area for bending. Long rear braces need to be reinforced in some way. Hans cage looks fine and I prefer a Halo bar up top to long roof/door bars, but the rear braces should be tied together with an X brace to spread the bending loads between them. FIA road race and rally rules specifically require this X brace for the reasons I mentioned above.

Nissan Type A 4 Speed Weight: 70 lbs. Length (bellhousing to end of tailshaft housing): 31" Shifter position (bellhousing to center pivot): 31" Nissan Type B 4 Speed Weight: 72 lbs. Length (bellhousing to end of tailshaft housing): 31" Shifter position (bellhousing to center pivot): 29" G-Force T5 5 speed Weight: 101 lbs. Length (bellhousing to end of tailshaft housing): 31.5" Shifter position (bellhousing to center pivot): 29" - aftermarket Long shifter

The spacer stuck on the bottom of the 3016 Tokicos almost always has to be shortened some amount. Being the simple guy that I am, for a stock strut length installation I've started just ordering the 3015s for front and rear and make my own spacer for the rear install.

I see this all the time too. Customer's car is handling like crap and he brings it in wanting me to install a coil over kit to fix it. I fix the broken anti-roll bar mounts, replace bushings, align the car, and then ask the customer to drive it. He is ecstatic and says the coil over kit was the best thing he ever had done to the car. He questions why the bill is so cheap and there are no coil over parts listed...

I don't think you can get any stiffer without going to coil overs. You might want to try changing the shocks to Tokico Illuminas.

Cool! I want to replace the seats in my '71. Where did you get a pair of 350Z seats for $350?

Hourly and do some research on what consulting engineers in your area charge for their time. Also, you need to realize that since you are being paid for the engineering of this bed you'll be on the hook if it hurts someone. You might want to look into some kind of liability coverage or have your customer sign an indemnification saying he will assume all liabilities, court, judgement, and other costs.

You're not coming off that way. In my example above I figured that the additional 100lbs. was behind the front axle not directly above it. Basically I assumed that the 24" engine was up against the firewall and an additional 12" was added forward of that. You BB/SB Corvette example is interesting. I wonder about engine position, transmission differences, and other itmes. But its probably a good example for this discussion.

Are you sure you can import it? I had a couple boys from Oz here looking at the Rusty Old Datsun and after some research they were convinced that they would not be able to get the car out of customs once it landed in Australia. That was a 1970 240Z...

I know there's a lot of emotion and ego tied up with everyone's builds and, as said in a post above, I'm not knocking what people are doing (this is HybridZ for God's sake). I'm not implying anyone is ignorant, stupid, mistaken, etc., I'm just trying to let people know what I've learned from building and racing 240Zs since 1998. Ya know, I try, and sometimes I wonder why I bother.

No. When talking about weight distribution we are really talking about the longitudinal location of the CG. Also, putting heavier axles on a car is not a good analogy for this discussion because we are talking about spring weight (the chassis). If you have a live axle car and make the live axle 100 lbs. heavier then yes, that end of the car just got 100 lbs. heavier. But, if you put 100 lbs. in the chassis directly over the axle then that end of the car will not get 100 lbs. heavier. Again, the sprung weight (the chassis) gets spread over all 4 wheels. I don't know how to state this any better.

For a street car I would recommend a welded in 4 point roll bar that is also attached to the roof C-piller where the hatch hinges connect, so technically it would be a 6 point roll bar. I do not recommend a roll cage for a car that's not always driven wearing a helmet. IMHO, those drag racing 6 point roll bars that have one door bar going forward to the rockers/floor are next to useless for side impact protection. The front mounting point has no lateral bracing other then the floor pan and that's going to crumple up in a good side hit. Some type of lateral floor pan reinforcement that connected both sides of the car through a reinforced transmission mount would help make the drag racing 6 point roll bars safer.

No. Again, an additional 100 lbs. added forward of the vehicle CG does not equate to exactly 100 more pounds on the front axle. The mistake is that some people think of the vehicle CG are a pivot point in a see-saw. Its not. Adding weight forward or back of the CG moves the CG in that direction by some amount. That same amount is always less then you would think.

Roll cages and roll bars are generally installed for safety reasons. They can also significantly stiffen the chassis if designed and installed properly. The key to increasing chassis stiffness is to tie together all the points in the chassis where loads are introduced with the strongest points in the chassis. Without these connections a roll cage/bar basically just adds weight.

A live axle car can be made to handle well. Even some stock live axle cars handled well from the factory. But a live axle typically has these inherent problems (compared with an IRS): High total weight. High unsprung weight. Excessive packaging dimensions. Dependent wheel motion. Slow wheel reaction. Lateral location friction/geometry changes. Brake and engine torque reaction affecting suspension geometry and reaction. Pinion angle changes. A lot of work with shocks, suspension locating linkage, and springs is needed to get a live axle to behave, let alone work well.

Your car has to be classed somewhere, even if its a mostly open classes like ITE, SPU, SPO, U1, etc. You should buy a SCCA, NASA, POC, PCA, BMWCCA, Speedventures, TCRA, etc. rule book right now before you start building your car. Every race sanctioning body has a minimum rule set you must build to or you won't be allowed on track. If you plan on running racing slicks and are building a 240Z to the weight you mention your car will receive a lot of scrutiny during the technical inspection, especially if you show up with a car like that as a novice. I know with POC you won't be allowed on track without an instructor riding next to you for your first 4 events. Again, get a rule book because, even though you're not building to some restrictive class subset, you still have a lot of rules (mostly safety) that you must meet before you'll be let out on track. Road racing tech inspection is much more serious then anything you've seen at an autocross.

After reading this again, I think you have a small misunderstanding regarding weight distribution. When we talk about weight distribution we're talking about percentages of the total weight of the vehicle. If we have a 2,000 car that has a 50F/50R weight distribution then 1,000lbs are on the front axle and 1,000lbs are on the rear axle. In your above example the longer engine has some mass farther forward but that extra 12" of mass only moves the CG of that 36" long engine forward 6" (compared to the 24" long engine and assuming its a solid block of metal). And, because the weight is always being distributed through all 4 wheels the net affect on weight distribution is smaller then we think. So, let's do the math again: 2,000 lb vehicle (400lb. 24" long engine) - 50F/50R WD. 2,100 lb. vehicle (500lb 36" long engine) - 50.2F/49.8R WD. Both of the above were calculated with Longacre software assuming a few basic things. That addition 100lbs made a difference of 2/5 of 1% in the weight distribution, although overall weight went up by 5%. Is that difference significant? Would it require some changes in suspension tuning? Probably not because much bigger changes are compensated for when using up fuel in a fuel cell hung out behing the rear axle.

I wasn't really focusing on your statement or anyone else's in particular. There just seems to be this basic assumption that putting an SR20DET into a 240Z automatically results in some ideal weight distribution and a super lightweight car. That basic assumption is wrong because so much more is involved as evidenced by your statement below: Absolutely and I agree 100% but the difference won't be as great as expected. Remember, both the radiator and IC will still be in front of the wheel centerlines. My example above was meant to show that just moving the L6 engine back 4" and down 2" will get you right where a typical SR20DET install is as far as weight distribution is concerned. It also shows that chassis choice (1970 vs. 1974 260Z) has a big affect on overall weight and can even negate the supposed weight savings of an SR20DET install. I'm not knocking the SR20DET engine, not making fun of those doing the install, not saying the L6 is the best, etc. I'm just saying that the mythology that's sprung up around this engine swap in a 240Z is overblown. A perfect example is a customer that I'm working with now who is putting a SR20DET that makes a gajillion horsepower into a 240Z. He was convinced that just this swap into an ex-ITS 240Z would make his car a track killer, until I spent a hour on the phone explaining things like: handling, balance, traction, all those little subtle things that have nothing to do with the powerplant. A RBZ or a SRZ can be a very fast and track friendly car, but being fast and track friendly has much less to do with horsepower then most people think.

Actually, the Nigeria code is 419. Here's a web site that pretty much wrote the book on how to scam these losers back: http://www.419eater.com/ I am proud to say that I've played a very small part and you can see one of my efforts on this site, although I'll never tell which one.

I was driving a SRF at a Friday practice at Buttonwillow and SCCA put all the sports racers and open wheel cars in one practice group. I was OK with the S2000s, CSRs, DSRs, Formual Fords, but the Formula Atlantics just scared the crap out of me when they went by. I would check my rear view mirrors before each turn and maybe see a dot back at the start of the straight I was just completing. By the time I checked my mirrors for the next corner the FA was right on my ***, diving into the inside of the corner, and was gone...

About twice as stiff as stock.