RACECAR PROJECT 

 

We spent quite some time looking for the perfect project car. We originally had an '83-'85 GSL in mind because of the rear-disc and limited slip options. However, we got lucky and ran across an '84 GSL-SE (minus the engine and transmission) for $450. Here are a few pics of the car just after we picked it up. You can click on the images to see the full size pics:

 



 

The first thing we did was to strip out most of the interior. We pulled out the carpet, spare tire, lots of trash, and most of the interior panels. We ended up with several bags of junk totaling around 200 pounds. [Note: We have since reinstalled the interior panels and new carpet back into the car so we could run in C Street Prepared at autocrosses].

 



 

The next thing on the agenda was the engine. We purchased an extremely injured car (for $200) and yanked the engine out of it. We used a transmission out of a wrecked (a moment of silence, please) GSL-SE. We had to decide whether to use the GSL-SE transmission or an '87 Sport tranny. We finally decided that the lower gearing of the SE tranny would serve us better on the autocross course.

 



 

We tested the compression on the engine (110psi) and then set about cleaning it up. It got an oil pan baffle plate, all new seals and gaskets, new water pump, etc. Oh yeah, it got a spiffy paint job too. We've taken to referring to it as the 'fire ant'.

 



 

Installing the engine and transmission was a snap. The Mikuni carburator and RB exhaust system also went on with minimal fuss. We opted for a Mallory Comp 140 fuel pump. The pump was an easy install, but it's a little loud for a $200 fuel pump. The worst part of it all was cleaning the engine compartment. It looks ok now, but there is still some work to be done.

  



 

Before installing the engine, we pulled all of the front sheet metal off of the car. The right-front fender needed to be replaced (someone went crazy with the filler), but everything else was in nearly perfect condition. I repaired a few little dings in the front header, sanded all of the components, sealed them, and shot three coats of 'Tender Blue Metallic' (the original color) onto the front-end components. It turned out pretty well:

 



 

Thats all of the pictures (and progress) that I have for now. I will be continually updating this page as we get more done to the car.

I'm sure some of you are wondering what kind of times this car is turning out. We don't have any official numbers yet. We are planning on taking it to the drag strip when we can. We will also have it weighed, just because we're curious about how much it actually weighs. At any rate, we do have some _unofficial_ numbers via a stopwatch and a nice straight, deserted piece of local road. It's getting 13.5 to 13.8 second 1/4 miles and is getting to 60 in around 5.5 seconds. We think the car probably weighs in around 2200 pounds and the engine should be putting out around 210 hp. Oh yeah, we're currently running on Bridgestone RE71-Rs.

Ok, here are some updates on the car. We had the car weighed and it tipped the scales at exactly 2200 pounds. We also did some runs with a G-Tech Pro and found that the 0-60 time was right at 6 seconds. Quarter mile runs came up at 14.5 seconds. Obviously our initial numbers (from the previous paragraph) were not accurate. I blame in on a spastic stopwatch finger. The area we were running our 1/4 mile times could also have been marked incorrectly (shorter).

Have you been wondering who 'we' are?

We are David Disney, Steve Small, and James Cruze. Dennis Edmonds and David Smith also lent a hand. I'll have some pics sometime soon.


I finished painting the entire car. For anyone interested, I painted the car with the original factory color (tender blue metallic) which has the Mazda paint code V3 (1984).

I also installed a set of 15x7 wheels with Kumho V700 autocross tires.

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I have also relocated the battery behind the passenger's seat and done a small amount of other interior work (gauges, toolbox tray, etc.). I'll have pictures of that up soon.


Ok, here are some pictures of the battery relocation... click the images for larger pics:

 

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The aluminum battery box (SUM-E890100) and wiring kit (SUM-G1206) are from Summit Racing Equipment. The battery disconnect switch is made by Flaming River and is also available from Summit.

I built a small mounting tray (which you cannot see very well in these pics) and welded it to the floor of the car. The battery box is mounted on that tray. The battery is grounded to the seatbelt lug. The positive cable runs along the passenger's door sill and out through a grommet in the firewall. From there it runs across the outside of the firewall and down to the starter. A second wire comes back up from the starter and connects to the factory wiring where the old positive cable used to tie in. I had a local battery shop make most of the cables from scratch (the short ones in the battery box and the one that ties into the factory wiring). I also had them shorten the positive cable that came in the Summit kit.

That's an Optima battery in the box. Vibration will not damage them, they usually won't vent at all, they won't leak acid even if they break open, and they will last much, much longer than a regular battery.


I am currently in the process of removing the Mikuni carb setup. I am installing programmable fuel injection on the car. I will use a 2nd gen (1987) throttle body, intake manifold, fuel rails, and injectors. I will control the injectors with a Simple Digital Systems controller. I will have pictures and details soon. I hope to be finished with the FI project within a week (1-18-2000).


I got the fuel injection installed... and I love it! The job was very, very easy. The only difficult part was fabricating a throttle position sensor bracket. I had to think about that one for a few minutes, but came up with a solution that is working well.

I removed the Mikuni carb and installed the intake from an '87 RX-7. This included the throttle body, dynamic chamber, upper intake manifold, fuel injectors, and fuel rails. The stock fuel rail has a fuel pressure regulator built into it and it works great in this application. There were many advantages to using the stock intake. It was cheap ($50 at a junkyard for everything). It already had provision for the oil metering pump rod. The stock 2nd gen fuel injectors are more than enough for a normally aspirated engine (about 50% duty is the most I saw during dyno testing). The throttle body opening is big enough to make decent power. You might make more power with an aftermarket throttle body and intake manifold... but it will cost you $.

I used the fuel pump from a GSL-SE and replaced all of the fuel lines with new, high-pressure line. I also used new injector o-rings and grommets (they will usually leak if you don't replace them anytime the injectors are removed).

I stripped the '87 intake down, removing just about everything that could be removed. I removed the choke butterfly valves and had the holes where the shaft was welded up.

I used a Simple Digital Systems system to control the injectors. It consists of a fuel computer, programming keypad, and a few sensors:

The stock TPS cannot be used because it is not a linear device. The SDS system (and all other aftermarket FI systems that I am aware of) use a common variable resistor (GM or Ford type) TPS. I ended up using a common TH11 TPS. I couldn't come up with a way of mounting it on the front side of the throttle body. I ended up removing the cruise control cable attachment from the throttle shaft and fabricating a bracket to make it work there. The pictures will do a better job of explaining this than I can. Also, I couldn't find a TPS with a D shaped hole in it, so I had to make an adapter to make it work on the Mazda TB shaft. You might be better off buying the TPS from SDS and adapting a bracket for it.

Here are some pictures and additional details... in no particular order:

 

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Digital Fuel Pressure Gauge and Air/Fuel Ratio Gauge, both are by Intellitronix and available from Summit.

The fuel pressure gauge is needed to make sure you are getting consistent fuel pressure throughout the operating rpm range. The A/F gauge is needed during tuning to make sure you aren't running lean.

They are mounted in a simple aluminum panel that I made.

 

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Some shots of the TPS bracket as I was making it. It is made out of square tubing and flat plate steel, welded together.

 

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Shot of the engine just after I installed the primary fuel rail and injectors.

 

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The finished TPS bracket. It bolts on to original holes in the throttle body.

 

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Closeup of the TPS. Inside the TPS you can see the little metal adapter that I had to make.

 

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GSL-SE fuel pump (and nice red tray ;)

 

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Finished installation.

 

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Air filter assembly. I used a stock 2nd gen air snorkel and a generic K&N filter with a 3" ID connector. I used a piece of PVC pipe to connect the filter to the snorkel. I was going to make a bracket to hold the filter in place... but it seems very happy sitting on top of the coolant overflow tank.

 

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Wide shot. You can see the TPS bracket here also.

 

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Here you can see the air temp sensor and the MAP sensor & bracket.

 

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Shot of the fuel computer (mounted in the glove box) and the LCD programmer.

 

After getting everything hooked up it was time to start it up. I turned on the ignition and immediately found a fuel leak. I knew it was stupid to use the Mazda hose clamps. I replaced the clamp on the leaky line (and all the others) with 5/16" fuel injection hose clamps from PepBoys.

After correcting the fuel leak, I tried to start the car. It started the first time the engine turned over!

I took the car out and tinkered with the settings until I got a smooth idle and a decent power band. The SDS system is very easy to program. I highly recommend the system. The people at SDS are very helpful and really seem to enjoy what they do. I called to ask a few questions about wiring hookups and they were quite nice. The SDS manual is very detailed and covers everything you need to know... read it a few times before you start the install/tuning process and you will be in great shape. The questions I called about involved an unlabeled injector harness that came from my vendor (I didn't know which was primary or secondary) and some vagueness about whether the tach pickup should be on the leading or trailing coil (it goes on the trailing).

Note: If you plan on doing this to a 2nd gen car, you will currently have to ditch the stock ignition setup and install an electronic distributor and coils from a 1st gen. However, SDS tells me they are about to release an ignition setup that will let their computer control ignition using the stock crank angle sensor and coils. This would be great, as the ignition system on the 2nd gen cars is very good.

The next step was to take the car to the local chassis dyno and see how much power I could get from it.

Here are the results:

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Rear Wheel Horsepower - (BLUE) Mikuni Max: 131.8, (RED) FI Max: 140.2

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Rear Wheel Torque - (BLUE) Mikuni Max: 120.4, (RED) FI Max: 119.5

 

So, it doesn't look like I gained much for all that work, does it? I was disappointed in the dyno results until I went out and drove the car after the dyno session. The car is much, much faster that it was before! In 1st and 2nd gear it almost feels like my 3rd gen!

On closer examination of the dyno sheets, it looks like I actually had the carb tuned pretty well from 2000 to 5000 rpm. From there the carb pretty much takes a nose dive. The FI makes more power and torque from 5000 rpm up to redline. If you consider that the normal operating range is from 3000 to 7000 rpm, you'll see that the FI is making a big difference over the upper half of that range. So, even though max power is only up by about 10hp, and max torque is actually down by a few tenths, I have a much wider power band than before (my average hp and torque went way up, even though the peak numbers didn't change much).

The carb worked well on the street, aside from some sputtering and general grouchiness below 3000 rpm. However, I was having some trouble on the autocross course with it flooding out during sustained, high G, right hand turns.   It would also bog down if you tried to use wide open throttle below 3000 rpm (which is necessary in some autox situations when downshifting would waste time).

The FI system has eliminated all of these problems. The car behaves almost exactly like a stock FI system with a few exceptions. It is a little grouchy until it warms up (it will die unless you keep the rpms up for a couple of minutes while the car heats up). Also, it is a little jerky on the transition from no throttle to light throttle (cruising conditions). I have a fast idle valve from SDS that will correct the first problem, but I don't know that I'll put it on anytime soon as it doesn't bother me that much. The second problem should be taken care of by an adjustment to the fuel computer, which I plan to do soon.

I have been told that someone who knows carbs could have corrected most of the problems I was having with the Mikuni. However, I'm a FI person and an electronics person, so I wanted to give the injection a try.

To sum things up: The car feels (and is) a great deal faster than it was with the carb. It drives very smoothly and takes off anytime you put the pedal down. I am very glad I made the change and am looking forward to the first autocross of the year.

Here are the fuel maps I settled on: FUEL MAPS

I'd like to say thanks to a couple of people for their help. I stole this idea from Bruce Crawford and he has been nice enough to let me annoy him with questions about it. A big thank you to Lee Graser who kept me supplied with used parts. Finally, thanks to Ed Reynolds at Mazda Gallery (1-800-339-5767) has been very patient and helpful when I needed new parts (they give a 20% discount on stock parts).


I'm firing the leading spark plugs directly from a set of coils, controlled by a MSD-6A ingition box. This improved power and smoothness. I'll have info on that up soon. Until then, here are some pictures:

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The next project is to install a Torsen limited slip differential in the car... hopefully before the autox season starts. The old clutch type LSD that came in the GSL-SE is worn out, and the newfound power from the FI setup is really making that apparent.


I'm also planning on breaking this page up into sub-pages so that it loads faster.

 

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