74_5.0L_Z

What kind of primary lengths do they end up with on those 180 degree headers? They seem long compared to most tuned headers. I imagine that the equally spaced exhaust pulse outweighs wave tuning. I've always loved the bundle of snakes.

Yes, the frame rails extend rearward to the crossmember in front of the differential. My frame rails follow the path of the original floor support/frame rails. If I were to do it again, the SFC would be made of 2x3 tubing that sits tight against the rocker panels, and the rear main hoop would sit on top of it. As it is my frame rails are 2.5" square tubing that penetrates the floor such that 1" is inside the car and 1.5" is below the floor. By routing the SFC tight against the rocker panels, you can keep them even with the floor pan and not loose ground clearance. You can see in the last picture the frame rails hanging low below the car.

If I understand you correctly, you are planning to do something similar to what I did. The tubes that converge above the T/C pivot point tie into the cage. The lower tube ties into the lower door bar and rocker panel. The middle cluster ties into the upper door bar.

I am leaning a bit toward the rear weight bias as the major player, but that is just my gut feeling. Unfortunately, there is not much left that I can move toward the rear or remove from the front. In the mean time, I'll just plan on having a passenger along. Its not a bad thing. I like the company. I was thinking about charging admission. The price being the use of a video camera. My plans for the next year or so include wider wheels and tires and getting the new engine in the car. When the new engine goes in, I plan to offset it and the transmission ~3/4" to the right (currently they are centered). This should help even out the left to right balance. Jon- I could raise the front a bit, but I really like the way the car is sitting. I will probably explore some other options first. Some of them are to go a little stiffer on the sway bar, install stiffer front springs, or install softer rear springs. The easiest of these would be a stiffer front sway bar. Changing springs forces me to re-corner balance the car. Changing ride height forces me to re-corner balance and realign the car. A sway bar change stands alone. I've had my eye on one of those Speedway engineering tubular sway bars.... Cary- I also want to start playing with some aero downforce. There is currently no spoiler or wing on the rear, and I may be making a bit of downforce with my front end. A rear wing may help balance the car a bit during the faster sections. I would really be interested in what you are doing with a splitter. Do you plan to write it up in the aero section?

I installed the 20mm sway bar and ran autocrosses on Saturday and Sunday. Both events were at BCC: Saturday was practice, and Sunday was competition. I made the first two runs Saturday by myself. The first impressions of the new sway bar was that the car felt a little more stable, but was still a little loose in the rear. I felt that I had made some improvement, but I was thinking that I needed to do something more. For the next run on Saturday, I took a passenger. I strapped my friend Gary, who is approximately my same weight (185 lbs), into the passenger seat and away we went. The car felt incredible. All looseness in the rear end had disappeared, and I ran the course almost two seconds faster than my previous runs. For the fourth run on Saturday, I ran by myself again. The car felt extremely loose compared to the previous run when I had a passenger. I was so floored by the difference that I decided to run the entire event on Sunday with a passenger. So, how did I do on Sunday? I beat the other two guys in my class (EM)by almost four seconds on a 35 second course. I had the fourth fastest overall time out of 80 plus entrants. The only people who beat me were in two cars that will be at nationals and one in a F125 shifter cart. One of the cars that was faster than I was a Super Stock Corvette, and the other was a A Prepared S2000. The Corvette beat me by ~0.5 second, the S2000 beat me by 0.004 seconds, and the F125 beat me by 1.2 seconds. Here is the riddle: Why did adding 185 lbs to my car help so much? Before we can answer that, we must look at the effects of adding a 185 pound passenger to the car: First, The additional weight balances the car left to right and improves the rear weight distribution. With just me in the car the rear weight percentage is 51.6% and the left side percentage is also 51.6%. Adding the passenger increases the rear percentage to 52.6% and balances the car left to right. Second, The additional weight lowers the suspension natural frequencies all the way around especially in the rear (125 pounds of the passenger goes on the rear and 60 pounds in the front). Aside from lower the natural frquency, the additional weight also helps match the frequencies left to right. Third, the Magic Number (from the WTW) for the car with just me in it is 5.24. Adding the passenger increases the Magic Number number to 6.22. A higher number indicates a greater tendency toward understeer and less toward oversteer. My guess is that the improvement is a result of all of the above. It would be nice to determine which has the strongest influence, so that I can optimize the handling without the additional weight. So, what is giving me the most benefit? Is it the balanced weight left to right? Is it the increased rear weight percentage? Is it the higher Magic Number? Is it something that I have completely overlooked? Man, I really love this stuff.

I have those spacers (and grade 5 fasteners) on my car. I think I'll replace those fasteners now just to be on the safe side. Thanks for the info.

Mine is no longer street driven, so generally I'm not worried about hitting curbs. I do however have trouble getting the car on the alignment rack at the local Tire Kingdom. The sump on my oil pan and my sub-frame connectors are only 3" off the pavement.

I too really liked the wankel site and was inspired to track down a copy of "Aerodynamics of Propulsion". Unfortunately, I wasn't able to find a copy for purchase, so I borrowed one from the NASA library.

The main reason that the vette and Z31 angle their radiators is so that they can fit a larger radiator under the same hood line. If placing the radiator at at angle gives you the benefit of using a larger radiator, better fans, or more room, then go for it. You don't have to cut a hole in the hood just because you angled the radiator. The air will find its way out, but if the air exiting the radiator has an easy path to a low pressure area then you have an easier time keeping the engine cool. If you don't plan on some sort of hole in the hood, then perhaps angling the radiator rearward would be best. If you take that path, make sure that you seal the radiator core to the opening so that air will not spill around the edges. Air spilling around the radiator rather than going through the cooling fins absolutely ruins the cooling efficiency. Also make sure you have a good air dam with an under tray so that you create a good low pressure area behind the radiator. For an example of this, look at a new Corvette.

I angled my radiator forward as part of an overall philosophy for handling the air that enters the front of the car. I want every air molecule that enters an opening in the front of the car to have a purpose. That is, air entering the front of the car should either cool something or feed the engine. In my case, the forward angle of the radiator allows me to establish ducting before and after the radiator that should reduce the drag coefficient of the car, increase the cooling efficiency, and possibly create a little downforce. The angle of the radiator is only part of the package. For the angle of the radiator to have any meaning, several other things have to happen: The ducting ahead of the radiator must cleanly slow the air (expand) to the face of the radiator. The ducting ahead of the radiator must be sealed to the face of the radiator (I use a rubber gasket). The ducting behind the radiator must reaccelerate the air back into the free stream. It took a lot of effort to establish the radiator ducting on my car. To do so, I designed my front frame rails so that the radiator could sit low and be unobstructed. The frame section that normally crosses in front of the radiator has been moved back in line with the sway bar. The placement of every component on the front of the engine was performed with the intention of keeping the exit plane of the radiator open. The alternator was moved to the bottom, the belt tensioner was kept as low as possible, and the radiator hoses were routed to the sides. It takes a lot of planning to do this right. If you are not planning to attend to all of the details that make the forward angled radiator beneficial, then you would be better off spending the time to assure that the radiator is sealed to the radiator support. The angle of the radiator means nothing unless the other details are in place.

While I was finalizing the design of my front end, I did a little bit of research. One of the best references that I found was a web site about cooling wankel powered aircraft. The author of the web page (Paul Lamar ) has since removed the content from the web and published a book with the content. The web page that links to the author is here: http://www.rotaryeng.net/how-to-cool12.html The web page and the book that sprang from it are a great compilation of data that sprang from research on cooling piston engine powered fighter aircraft at the end of World War Two. This book does a great job of summarizing the information from Kucheman and Weber's "Aerodynamics of Propulsion", and from London and Kay's "Compact Heat Exchangers". The book explores (among other things) two different but equally effective philosophies of inlet and outlet ducting. Kucheman and Weber's research led to a long inlet with a small front inlet that expanded smoothly until it got to the face of the radiator, and an exit that contracted as the ductwork merged with the body. Kays and London's design had the radiator laying nearly flat with a wedge shaped inlet. Both designs sought to slow the incoming air to create a high pressure region across the entire face of the radiator. Additionally both design philosophies accelerate the air in the exit duct to minimize drag. If I were to do mine again, I would probabbly lay my radiator down even further to more fully approach the London and Kays design. In fact, I would arrange it such that the top of the radiator was even with the top of the bumper and just behind it. If you are serious about designing a cooling system, read Paul Lamar's book.

My radiator is installed as in example 1. It has been tilted forward 48 degrees, and the bottom has been moved back to just forward of the sway bar. The radiator is completely sealed to the opening in the air dam wit ha rubber gasket. All air that enters the radiator exits through the hood.

Cary, I looked at the effect of chassis rake. I can raise the magic number by about half a point by lowering the rear roll center ~.75 inch. Unfortunately, my rear tires get pretty darn close to the wheel housing as it is. Additionally, going lower also forces me to have more static negative camber in the rear (I am at the limit of adjustment of my camber plates). So I decided not to lower the rear any further and to make a new front sway bar. Additionally, I think the stiffer front sway bar will help keep the inside rear tire on the ground going into the corners.

I've run a couple of events since Sebring. At Sebring, the surface was concrete and the traction was amazing. The traction was so good that the car was easy to catch if it started to oversteer or understeer. The other surfaces that I have to run on are not nearly as good. BCC in Palm Bay is smooth asphalt and has probably 80% of the grip as Sebring. The surface at the Deland airport is old deteriorated asphalt and the traction is probably 50% of Sebring. The car as I had it set-up in Sebring and most recently at Deland had a Magic Number of 2.92 per the Weight Transfer Worksheet. The car set up with a number this low should be very prone to oversteer when the power is applied coming out of the corners. At Sebring, the traction was so good that it was easy to compensate, and the car wiggled through the slalom sections amazingly well. At Deland, the car was nearly undrivable. The car was always on the hairy edge of wanting to spin, and forget accelerating out of the corners. It was not fun at all. To try and make the car more drivable on the surfaces with less traction, I am putting together a new front sway bar. The current bar is a modified stock sway bar from a coupe (18mm). I am replacing it with a modified bar from a 2+2 (20mm). According to the WTW, the magic number with the new bar should be about 4.95. The higher number should give the car a little more understeer tendency and allow me to get out of the corners a little better. In addition to the two sway bars that I've mentioned, I have a 25mm front sway bar at my disposal. The problem with a bar that big is that my Magic number would be 12.44%. A number this big would mean that the car has a strong tendency towards understeer. Anyways, with three sway bars at my disposal, I need to do some testing at the next practice day. The next practice day is coming up August 16. I plan to arrive with the 20mm bar installed, and then based on the car's performance switch to either the 18mm bar or the 25mm bar.

Most importantly, you need a clear understanding of how you intend to use the car. Will it be strictly a street car? Will it be strictly a drag car? Are autocross and track days in your future? If the car is going to be used for anything but strictly drag racing then you probably want to get rid of the C4 transmission. The C4 has no overdrive and will make the car unpleasant to drive on the highway (unless you like 3200 rpms at 70 mph). You need to have a realistic understanding of the limits of your budget and time. Building a HybridZ requires a fair amount of money and lots of time. Most builds (assuming sufficient funds) require about 1 to 2 years to complete. During the course of the build, you will reach points where the amount of work left to be completed is overwhelming. It will be tempting to give up. At the same time, there will be other demands on your time and money. You will never finish a building a project like this if the Z is not VERY high on your priority list. It sounds like your brother is a fellow gear head. If so, this may be an opportunity for some serious brotherly bonding. If you have friends that are willing to spend time with you on this project, then everything will be easier. As I've stated above, there are a lot of hurdles to clear when undertaking a project like this, but the end result is worth it. If you take your time and do it right, the completed car will be an enormous source of pride and accomplishment (and fun). Good luck and remember that there is a lot of information on this website. Most of the questions have been asked and answered. If you search and can't find the answer, then feel free to post a question.

My car has 6 degrees of caster. To achieve that, my lower ball joint is about 1" in front of the pivot for the lower control arm (in the side view). Looking down on the car from above, the control arm is angled forward ~ 5 degrees. If I were using the delrin aluminum bushings at the inner pivot, then I would not be able to push the control arm forward in that manner without applying a heck of a lot of force to the control arm, T/C rod, and the aluminum bushing. Additionally, the T/C rod is attached to the control arm with two bolts. As designed, the T/C is angled (~37 degrees) so that it is aligned with the holes in the frame and the holes in the control arm within a small range of suspension adjustment. As you push the control arm forward, the bolts at the control arm end will not line up properly. With a little effort, you would probably be able to force everything into alignment, but this creates strain on the control arm, T/C rod, and the attaching hardware. My solution was to install spherical bearings at the lower control arm pivots, and to reengineer the T/C rod to allow angle change between the control arm and T/C rod. When you get finished with that and can crank in some caster, the tire will be pushed forward in the wheelwell like this.

Unless you have spherical bearings installed at the inner pivot of the lower control arm, you should not attempt to lengthen the T/C rod. If you still have rubber at the inner pivot, you can get away with it (sort of), but if you have the common aluminum delrin adjuster the DON'T DO IT.

I'm sold on the limiters. Since finishing the suspension mods and getting new tires, I have run two autocross events. The first was at Gainesville on an asphalt track with no limiters, and the second was at sebring on concrete with the droop limiters installed. The transient response at Sebring seemed faster. I meant to disconnect the droop limiters at Sebring to get a more apples to apples comparison, but I was having so much fun that I forgot. I still haven't taken the time to fully understand why they work (at least not formally). Subjectively, I like the way the car handles with the limiters installed. Objectively, I plan to do back to back runs with and without them installed at the next practice event.

Thanks Jon, I am really happy with it. I love the way the car now wiggles through the slalom sections. I noticed the front tire coming up but not the rear. I'll have to look a little closer at the video. The concrete looks so washed out because the temperature was 97*F that day. I'll borrow a camera soon and get some pictures of the limiters.

A little update: I ended up replacing my tires with the same size (245/45/16) Hoosier A6. I wanted to go up a size, but my old tires became corded before I could acquire some larger wheels. Even though I couldn't go to the next larger size, I have to say this: New Hoosiers are MAGIC! My old tires had died from age and heat cycling, so I had enough time to forget what they should feel like. The car does what I tell it to, when I tell it to almost without exception. I just wish the driver was a little better. Additionally, I have installed the front droop limiters. They are simply cables that prevent the strut from drooping past the point where the spring comes loose. In my case they stop about 1" of droop travel. I have not installed them on the rear because my rear springs do not unload at full droop. The front droop limiters do reduce body roll. Here is some video of the car from an autocross at sebring two weeks ago: I am extremely happy with the way the car is handling, but I still plan to get some bigger wheels before the next set of tires.

I checked my numbers with DG's calculator and came up with LF = 665.31 Lb RF = 621.69 Lb LR = 707.69 Lb RR = 661.31 Lb. These are pretty darn close to my final numbers of LF = 662 Lb RF = 623 Lb LR = 708 Lb RR = 661 Lb.

I corner balanced the car again yesterday. I try to do this whenever I make significant changes. For those of you following along, I completely changed my suspension set-up. I went from 250 rear/ 200 front springs with a 1" front sway bar to 425 rear/450 front springs and an 18 mm front sway bar. The car has also been lowered 1" all around, the stock seats have been replaced with lightweight MOMO Start2007 seats, the rear struts have been sectioned, and rear camber plates installed (all since October). So I thought it was time to rebalance the car. Here are the starting numbers with driver (me) and fuel: LF = 683 Lb RF = 604 Lb LR = 690 Lb RR = 679 Lb. Total = 2656 Lb These were my percentages: (LF + RF)/ Total = (683 + 604)/2656 X 100%= 48.5 percent on the front 51.5 % on the rear. (RF + RR)/ Total = (604 + 679)/2656 X 100% = 51.7 % on left and 48.3% on right. my diagonals were a little off: (LF + RR) = (683 + 679)= 1362 (RF + LR) = (604 +690) = 1294. To fix this, I raised the RF spring perch 1 turn (1/8"), and the LR 1 turn. After this minor adjustment, these were the results: LF = 662 Lb RF = 623 Lb LR = 708 Lb RR = 661 Lb. (LF + RR) = (662 + 661)= 1323 (RF + LR) = (708 +623) = 1331:mrgreen: Here is the thread that discusses all of the suspension stuff that has been performed since October: http://forums.hybridz.org/showthread.php?t=130005 Here are the final numbers with fuel but no driver: LF = 603 Lb RF = 622 Lb LR = 627 Lb RR = 617 Lb. Total = 2469 Lb These were my percentages: (LF + RF)/ Total = (603 + 622)/2469 X 100%= 49.6 percent on the front 50.4 % on the rear. (LF + LR)/ Total = (622 + 617)/2469 X 100% = 49.8 % on left and 50.2% on right.

Those look great! When I get around to making my next set, they will be similarly constructed. The only thing that I plan to do differently is make the rear heim the solid point, and let the front heim be the toe adjuster. What wall tubing did you end up with? My current control arms are made using 1.125 x 0.058 4130 tubing, but they use a lot of extra triangulation for redundancy. With your new control arms you have converted the rear suspension from an H-arm to an A-arm toe link type strut. By doing so, you have given youself more freedom regarding toe and caster. The H-arm type strut suspension demands that the strut is perpendicular to the control arm. If the strut isn't perpendicular, the control arm and strut must flex or bind as the suspension goes through its range of motion. Because of the requirement for an H-arm strut to be always perpendicular to the control arm, caster and toe are limited. The A-arm type gives you more options. You can now move the top of the strut forward or aft. As the suspension moves through its range of motion, the toe link rotate to prevent the suspension from binding. Moving the top of the strut forward or aft will allow you to play with anti-squat and roll steer of the rear suspension.