RX-Stephen


Welcome to my webpage.

Last updated 16th April 2006


Hey guys, this site has not been upated in a very very long time!
But, I still have the little red rocket after over 7 years. She now has a full roll cage and
I've been competing in some dual car sprinting just to cut my teeth
on some motorsport.
Success for my first year saw me come 1st equal for my catagory.

The motor is still the same stock porting, turbos and fuel system.
I've done all my own tuning with Datalogit using a Techedge wide band O2 sensor.






This page is dedicated to my RX-7 FD3S project (Japanese spec R1).
Above pic is with my new 17" Mazda RS wheels.

RX-Stephen's Favourate Links last updated 5th July 1999
 

I belong the the New Zealand FD Kai (Club), check it out....
Fd Kai
 

My RX-7 Project Goals are

To reduce the compromises that make the RX-7 a high performance street car into making it a true super car and track car, by improving power and handling, but limited to a budget.

To limit the engine modifications by the upper limits of the stock fuel and turbo systems. This will put a natural cap on money spent, but will produce super car performance capable of 0-100Km times in the 4's and ¼ mile times in the 12's.



Current mods are....
Click on each modification below to get a commentary

Carbon fibre intake with K&N filters

Trust 3" down pipe, HPC coated

APEXi PowerFC with Datalogit

RB cat back

3" mid pipe with 4" muffler

Front mount inter-cooler and Race Radiator

Race brake pads

Urethane left engine mount

Heavy duty clutch pressure plate

NGK 11.5 Race plugs

Dry cell battery

Tein RA adjustable shocks & springs

Much much stickier tyres!

Under drive Pulleys

Removed air pump

Full Chrome Moly Roll Cage

Water Injection

The story so far
Before taking my car off the road for more mods, (mods were RB cat back, RE intake and 13psi chip upgrade) I did a few Gtech-pro runs and got 0-100Km at 5.5 sec including a bad launch with spinning tires, I'm sure I can get low 5 sec with a bit of practice. An indicated 285HP at the wheels in second gear (very subjective, not to be mistaken as a true dyno run, but gives me a base line to see what further modifications will do).  

During
With the car still not running satisfactorily I am getting 0-100 in 5.2 (still need new tires) and indicated 335HP (50 more HP). The car is very hard to control when the secondary turbo cuts in, I always get wheel spin and it's hard to moderate the power.  

Tuning Problems
The car is backfiring on full boost (seen it peak to 17psi!) I still have a small inter-cooler, and am sucking hot air into the air cleaner. The chip mods are running rich, so I cannot really get the most out of the mods until I get some cold air into the whole system. I reckon there is an additional 50HP, once I get it running right. 

I suspect that the backfiring is a combination of too rich, and not enough spark. I will try new HT leads, but think that I will need a serious spark generator (back to the shopping list :-) the fact is that when you push up boost, you need to either close the gap on the plugs (hard to do on a surface discharge plug), or preferably put more energy into the spark!  

A solution
It looks like my theory was partly right. I replaced the stock leading plugs (heat range of 7) with some racing plugs (11.5's). This sounds drastic, but I have had no problem with them fouling up, and the real advantage is that the gap can be set closer, and the electrodes are more exposed than the stock plug.

Result is smooth running all the way to the red line!!! At 16+ psi the car kicks ass. I have not done any Gtech-pro runs yet (stay tuned), but the next problem is heat. After a few WOT runs the power delivery becomes less as the manifold temp goes up. 

After
I had been running some Yokohama AVS S1-Z tyres, that gave great handling and good grip. But when I put 17" wheels on I chose the Dunlop Formula FM901. In Australia and New Zealand these tyres are slightly different specification to the rest of the world. They are a Z rating that is higher than what you see else where. I'm absolutely blown away with their grip and wet weather traction.

By including water injection into the manifold I am able to get repeatable horse power runs without the power robbing heat soak that I had before.

Horse power as measured by the Gtech-pro using the same base lines as before is now 374. I'm guessing that that is a pretty good estimate at the flywheel horse power based on running 17 psi boost, but I plan on a proper dyno run to effectively calibrate my Gtech-pro tests.

After 7 years!
The FD has been a hobby over the years, I've managed to keep it on the road while slowly upgrading it. I now have a full Chrome Moly roll cage that has stiffened up the chassis substanitally. All engine tuning has been to smooth and lean the engine out. Thanks to the water injection I can run things a lot leaner. The car has run on the dyno with 251KW at the wheels, with fine tuning since then I'm now sitting well over that. That 251KW equates to around 400HP at the flywheel which is right up there for stock turbos and fuel system, the fuel injectors are running at 93% duty cycle. On the race track I lower the boost from 17psi to around 14psi to keep things cooler and help the engine last.

Most of my tunning has been around suspension setup. I've replaced the Tokico shocks with Tein RA and put urathane bushes on the front anti-sway bar. The Tein are a much more accurate shock, and the springs are a lot stiffer and suited to track racing. The last time I went to Taupo race track I trailered the car so I wouldn't have to suffer the stiff ride, even though I've kept the car road legal, any trip more than a couple of hours is pretty exhausting in such a stiffly sprung car, especially with the RaceTech race seat that transmits every bump to your back side.

Being a Japanese spec car,
you have to be careful about ordering parts over the internet.
Most vendors are US based. For example the down pipe needs to be specific to
the car as the steering shaft gets in the way on a right hand drive car!
 

Lessons learnt so far....
This is not an FAQ, but some useful tips based on my experience
doing the modifications to my car.

 

This Mazda Rotary Webring site is owned by
Stephen.

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E-mail me at stephenm (stop spam) clear net nz


 


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