johnc

I was jokingly referring to the MSA bumpsteer spacers as "kickback" spacers because they don't really fix bumpsteer, they just move the problem somewhere else. Some folks, when they install the spacers and feel a reduction in steering kickback, think the bumpsteer problem has been solved.

With people easily pulling over 300hp normally aspirated and over 500hp turbo with the existing supply of $2,500 fully modified L6 heads, does anyone think a $12,500 head would help as well as its price suggests?

Most of those bungs are 304. If its cast iron I would still recommend a stainless filler. Its ductile enough to work as long as the part is completely pre-heated to 600 degrees and then slowly cooled (overnight).

BTW... just becuase the suspension gains negative camber that doesn't mean you'll actually see an increase in negative camber on a race track. Body roll can negate any suspension camber gain at the tire itself. The trick is to balance static negative camber and the camber gain in bump against limiting body roll while retaining compliance.

Its not that complex Bob. If you lower the front ride height you gain negative camber until the lower control arm goes past level. Have a really fat person sit on the front of your 240 while you put camber guage on the front wheel. Also remember that the strut is attached to a ball joint at the bottom and either the stock, compliant rubber bushing or a spherical bearing up top. The strut not only compresses, it pivots at the top and bottom. Be like a Zen Master: accept! Or, take some poster board and cut out parts to make a 2D suspension. Play with at at your desk on some graph paper.

Mike, You're gonna need a rear spoiler. Turn 8 at Willow...

FYI... I seriously looked at moving the steering rack. Even had some drawings done up. It really involves a whole new crossmember and if you're going that far, there's a LOT of things you can do with a clean sheet crossmember design. It became this huge Pandora's box and I eventually put it away and got on with getting my car back together. Maybe later this year...

> but isn't the angle between the strut and > spindle fixed, with the ball joint below > attaching to the LCA Correct, but also see what Tim posted above. > Just to bend everybody's brains a bit farther, > we must also consider that the arc that the LCA > travels in is also constrained by the > compression rod. Good point. To expand on it further in this camber gain discussion: shortening the effective length of the TC rod can significantly reduce camber gain. Why (someone might ask if they are bored enough to read this far in the thread?) Well... positive caster has a lot to do with the camber gain a suspension might have. Even if your car has lots of static positive caster at ride height, a TC rod with a shorter effective length tightens its arc, which means the positive caster goes away quicker as the suspension compresses in bump. This significantly reduces the camber gain in bump that might have appeared to exist when everything was measured sitting still at ride height. So, you might measure 6 degrees of static positive caster at ride height, but because the pivot point of the TC rod has been move forward from its stock location (via different bushings, special heim jointed mounts, etc.), you might lose all of that positive caster after only 2" of bump travel. BTW... you're guaranteed to lose some no matter how long the TC rod's effective length is. > This is because the compression rod is at a > ~45 degree angle (probably more like 60 deg, > but you get the picture) to the body. So, > moving the inner pivot point out results in > moving the spindle both out and back, > decreasing the caster. Now we're getting to the real subtle stuff. Pushing the rod forward more to get back this lost caster back puts a lot of fore/aft load on the inner control arm bushing and the TC rod bushing. This increase friction (stiction) in the suspension and reduces compliance. One noticeable effect of this is that shock adjustments don't appear to work anymore. Anyone made changes like this to the front suspension and then think their Tokico Illumina adjusters were broke? My hand is in the air! Angle drilling a new set of solid bushings suddenly gave me back ALL of my shock adjustments.

30 psi. EDIT: Coffey you dummy, 30 CFH!

Bumpsteer is exactly what it says, the steering of the car is affected by changes in bump travel. When the suspension travels up and down, the wheel moves up and down in an arc or half circle around a pivot point. This pivot point is not a physical location or suspension part but is an imaginary point on the chassis, similar to a vehicle's center of gravity. The distance from the pivot point to the wheel and spindle is equal at all points in the wheel's range of vertical movement. The tie rod and steering rack must be positioned so that as the wheel moves up and down, the tie rod follows an arc which is parallel to the arc followed by the spindle. If the steering rack or tie rod is not positioned correctly, the distance between the steering rack and wheel may differ from the distance between the pivot point to the wheel at different suspension heights. When this occurs the steering rack will push or pull the spindle as the suspension moves up or down thereby turning the wheel and causing a change in toe angle. This change in toe angle causes a change in the direction of travel of the front wheels. As a driver you see and feel this change and a difference in where you told the car to go with the steering wheel and where its actually going. What you feel through the steering wheel is called "kickback" and is often confused with bumpsteer because they tend to go together. But, bumpsteer and kickback are two separate things. Now, from the explanation above it should be easy to understand that to correct bumpsteer the arcs of the the suspension and steering need to be in sync. This can be done on the early Z front suspension by modifying where the tie rod connects to the steering arm or by relocating the lower control arm innner pivot point. The MSA bumpsteer spacers should actually be called kickback reduction spacers. They reduce steering kickback and only indirectly reduce bumpsteer. In fact, the spacers generally make the front suspension worse from a performance standpoint because they reduce the built-in camber gain in bump. The bumpsteer that occurs in a lowered Z is not something that needs "fixing" from a performance standpoint until the car is lowered more then 3". If the steering kickback is bothersome then install the MSA "Kickback" spacers.

Looks good Mike. Is the dip at 4,000 when you got foot-to-the-floor for the dyno run or is there some more tuning needed right there?

Stainless wire - 309L is the best for dissimilar materials.

That comp ratio shouldn't be an issue - you don't need a gear reduction starter. You have cable, battery, or starter problems.

FYI... some of the brake light switches under the master cylinder also have a prop valve in them. They work in combination with the second prop valve in the system and should be kept together as a pair. I have not been able to discern a pattern in Nissan's use of the dual prop valve brake plumbing. I do know that some combinations of prop valves are cherished by ITS racers; probably more for superstitious reasons then anything else.

> No it is not needed and should be removed > from system! Well... as always the answer isn't that simple. Is the car running rear drums or disks? Have the front calipers and disks been changed from stock? What master cylinder? What year is the brake plumbing (brake light switch and prop valve?) If the car is using rear drums, leave the stock prop valve in AND install the adjustable prop valve. The stock prop valve gets you very close to optimal front/rear balance and the adjustble valve lets you adjust for rear brake shoe wear during a race. If the car has disks all around, then the questions move to: 1) the type of master cyliner including piston diameters. 2) the type of calipers and the number and size of the pistons. ... but, in most cases when changing to disks all around (and you know how to properly adjust and balance a brake system) you should remove the rear prop valve and add an adjustable prop valve for the rear brakes. Buy the Tilton knob adjustable one and install it in the engine compartment. Use it to get the balance correct. For racing, add the lever adjustable one next to the driver's seat and use it to balance braking for racing conditions.

Always replace the ground cable when you replace the power cable. And be sure there's a good ground strap from the engine/tranny to the chassis.

I don't remember if I ever posted this here. Great resource for information and real examples of race car aerodynamics. Mulsanne's Corner

I'm running the Bosche LSM 11 4 wire and it gives a Lamda range of 0.68 to 1.32. How much wider range is needed? It does cost about $220 though.

Well... since the SU's tend to run lean at high rpm on a stock 240Z, I'm not sure where you're going to get the extra fuel that NO2 needs.

It depends a lot on your cam. I'm running 13.6-1 and I have detonation problems with anything less then 108. Normally I run 110 leaded. Here's some information about high compression: http://www.motortecmag.com/archives/2001/jun/JUN01-01/JUN010101.html - John

I think you see a problem where none really exists. The Z holds it own on the racetrack with 2nd generation RX7s, Preludes, Integras GSRs, E30/E36 BMWs, etc. in SCCA ITS. The 240Z suspension can be made very compliant and close to geometrically correct as most anything it runs against. Yes, there are some design limitations you have to work around with a strut suspension, but that's true with any suspension. Remember, the E36 BMW M3's front suspension is a strut design and its probably one of the best handling cars evey made.

They were called "Y" blocks because the skirt extended below the crank centerline. Looking at the block from the front it looks more like a "Y" then a "V." Had a 292 4 barrel in "Mazola", my old 1958 Ford 1 ton truck.

Like most wheel manufacturers they have a "street" product line and a "track" product line. If they are true multi-piece wheels then they are from the track line and might be worth a little bit to an ITS racer (if they are 14" x 7") depending on the weight (under 12 lbs) and condition.

The firing order of the L6 is setup as if the motor is two 3 cylinder engines. Every cylinder gets one of the dual SUs all to itself every 240 degrees of crankshaft rotation. This results in a very even mixture distribution, high velocity, and low reversion across all 6 cylinders. With a triple SU setup pairing cylinders with each carb you get an uneven mixture distribution and uneven power production. Look at the table below. The first number is the firing order and the second is degree of crankshaft rotation. 1 - 0 5 - 120 3 - 240 6 - 360 2 - 480 4 - 600 1 - 720 (0) 5 - 840 (120) 3 - 960 (240) 6 - 1080 (360) 2 - 1200 (480) 4 - 1320 (600) 1 - 1440 (720) Using the table above you'll see below how cylinders 3 and 4 have an even distribution of intake charge but the other cylinders have uneven intake charge distributions. This causes reversion in the intake track and a very uneven mixture across both cylinders through 1440 degrees of crankshaft rotation. 3-4 Intake charge every 360 degrees. 1-2 Intake charge 480 degress, then 240 degrees. 5-6 Intake charge 240 degress, then 480 degress. Triple SUs have been tried many, many times and they do not work as well as dual SUs. If you need more fuel/air then go to the 50mm SUs. BTW... Triple SUs will probably work if they open onto a plenum before the intake runners. The larger the plenum the better. But, you might have problems with fuel metering.

Weight is not really the issue; caster is the big determiner of steering effort.