Building a circuit spec MR2
The reasoning for the thread is to help other people and discuss with people who are looking or dreaming about going down this path.
As I have spent the last five years wasting a lot of time building (then rebuilding, changing, falling over and hopefully learning) a circuit MR2 I have some idea's idea's on how I would go about it if I was crazy enough to do it again.
There are plenty of ways to approach a build with a number of examples on this site. I have highlighted a few to give people an idea.
Highlander: Bought a existing SW20 circuit car (CAMS logged) for a reasonable sum. He then paid someone to fit a 3.5ltr V6, upgraded the brakes, fixed some of the worn out components and is now ready to enjoy 1000's of race km's with relative low maintenance costs.
Stuka: Bought a SW20 Tarmac Rally car CAMS logged) for a reasonable sum. He then upgraded the suspension, brakes, roll centre adjusted, bump steer and steering ratios. The car still retains a standard 3SGTE with excellent reliability and drive-ability.
Both packages are low labour input from a pre prepared car. Highly recommended way to go about it.
Then there is the street cars upgraded to Rally/Circuit spec cars.
Eckers: Has a tuner car imported from Japan, performs some minor upgrades then fits a full CAMS/Rally spec roll cage.
Again there is a degree of work which is more than Highlander and Stuka, but quite manageable.
Sweetpete: Another imported car but a MR2 Spyder. Excellent starting package which had a engine conversion to a stock 1.8ltr turbo, then fitted a cage. 1019kg with a heap of reliablity. simple and effective.
There are a few out there who have been building their cars to the edge of street car limit but without a cage ( Knightrous and Matsuda). Both excellent packages and very competitive.
EVO65 built a SW20 from a import. He is quite experienced in building a decent car and this one is a great example. The car received a basic cage, fitted bolt on braces for the guards, underbody and where ever else, no seam welding. Next was to purchase cheapish big brake and suspension upgrade (all D2 spec). This along with suspension/RCA mod and settings were prepared by a qualified suspension specialist. This was followed by cooling and fuel management, ecu engine management and engine fail safes. He then had the engine/turbo/gearbox built to his spec.
After this he organised a high quality driver to test and prepare his car over a series of days. The final result was the quickest MR2 ever scene at Eastern Creek.
My car is similar to EVO65 but have followed a different route in a few area's. Looking for low weight, low COG, maximum chassis rigidity are the key points.
WideMR is the highest step we have on the forums with a complete package for a MR2 with everything done to the highest spec he can manage.
So there are a few ways to go about it with all having a similar outcome with performance and reliability. The standout being EVO65 who focused a lot on the suspension geometry and power delivery.
So if I was to build another car or someone asked me how to build one, this would be the answer.
Choose what you wish to run the car in and what your goals are. In this day and age, you can run just about anything anywhere aside from Rally.
I find that less weight provides less of everything else so its what I would recommend weight reduction of everything possible. Modified engines are the last on the list not the first. They are the most expensive so leave it till last.
As a figure for minimum final weights : AW-950kg, SW20-1000kg, Spyder-930kg.
For a more reasonable figure: AW-1000, SW20-1050kg, Spyder-980kg
So here is a breakdown (from what I feel is the way to go).
1: Completely strip the car to a bare shell (including glass, sound deadener etc). Why? It will save a lot of time and effort.
2: Bead blast all points to seam weld and roll cage location points.
3: Remove all unnecessary brackets both under and in the chassis, remove second firewall (SW20), trim all spot welded seams by 4-5mm.
3: Hire a welder then seam weld the chassis both under and above the body. Then clean up all the welds of required.
4: Decide the right cage to suit then have a professional install it.Also install solid mounting points for the race seat and seatbelt. Pricing varies.
5: Gusset your suspension mounting points.
6: Prepare the rear wheel arches for bigger wheels and lower ride heights. Same for the front.
At this stage I would add paint to all the welded ready for the next stage. The cost of time to do this is close to 80-100hrs so it does require a fair amount of commitment but you will have an excellent base to start with.
Next would be the suspension.
My personal goal is for double A link all round with a lightened tubular rear sub frame but for most applications this would not be an option.
Having new bearing, ball joints, bushes is cheap and required.
Lighten then hubs as much as possible by removing any unnecessary meat. Check and adjust the weight of the hubs so both the front and rear pairs are of the same weight. Picky but not a bad little job. You can also upgrade to S14 after market alloy units if you are keen. Light, strong and improved adjust-ability.
Same prep for the LCA's unless you wish to upgrade to Chrome Moly units with rose joints. There are a few places who can make these for a fair cost. To have a full set front and rear is about $1000. This allows for complete adjust ability for camber/caster/wheel track front and rear.
The coilover package would be up to the individual but would recommend two way adjustment to maximise the tighter chassis.
Also upgrade the wheel studs.
The time would be 30hrs at a guess and cost can be from $1000-$5000 depending on requirements.
Brakes:
You can use the standard brakes but if you are looking for an upgrade:
Install a Willwood twin pedal, overhead mounted assembly with twin master cylinders. Use the remote canisters so the fluid is in the front of the car, not in the cabin. The power assisted unit is not required and is a weight penalty.
Two piece rotors are a must as are alloy calipers front and rear. The one piece are just too heavy as are the steel calipers. The pedal box can be fitted once the seat has been installed to improve your driving position.
Steering:
I used a Toyota Echo steering column which was modified a little then a bracket made to attach to the bar between the A pillars. Reason being the weight saving. This along with the removal of the power steering system saved over 10 kg. It also has two compression points in case of an accident. This was fitted with the seat and pedals in the car to improve on the steering wheel location. If its possible, fit the AW11 quick rack into any of the three models as they are easy to find and have good ratios. If you are keen enough try a speedway steering rack. Plenty of options and very cheap. Just need to make brackets to suit.
The cost of the Echo steering column was under $50.
At this stage the car would be a rolling chassis with operating brakes and steering and nothing else fitted. A great base for a circuit car.
Fluid management:
One of the most important aspects of the build.
Fuel is first with the tank cleaned, fuel foam installed,fuel pump replaced with a new high flow unit and upgraded wiring for the pump. A surge tank and external pump installed in the front of the car with new steel fuel lines fitted where the old heater lines were located, finishing at the firewall.
Coolant: running a standard water pump with a Davis Craig for improved control is recommended. New hoses and radiator if possible.
Add ducting around the radiator.
Oils: Fit a oil cooler to both the engine and gearbox. Fitting these under the car is best with stone guards for protection. Ahead of the engine is also wise move improve how effective they are.
Wiring/Electronics: I would recommend a rewire of the car as it saves a lot of weight and it also allows you to simplify the whole system. If you are keen it can be done yourself or you can pay someone to do it. Cost is $1500 and up.
Even if you are using the OEM dash/ecu you should look at re hashing the system with new connectors,plugs, clips and installing new wiring to these points. Also look at replacing your sensors.
If you are going with a new ECU do not get a cheap option but get something decent which allows for easy work for your tuner, plenty of fail safes and logging options. Haltec is a good option.
Fitting mechanical window winders and mirrors will also eliminate a bunch of wiring you can do without.
A small light weight battery is an option but you will manage fine with the standard size one. Fitting the battery to the front of the car is a good option for the AW.
Engines and gearboxes: this is up to the individual. I think the 2zz in any three of the MR2's would be a treat and the 2-AR/2-AZ or 3MZ vvti is also another good option for a light weight power plant for any of the cars. This is a debate in itself but the thread is more about the prep outside the power-plant.
Fuels: Just stick with 98 RON. Its easy to find, required no maintenance.
There are a bunch more things to add but will leave it with this for the moment.