mx5cartalk.com

I really enjoy driving my track car at NSW club track days and supersprints, and find it a great car to drive with stable and predictable handling leading to reasonable lap times with a mostly stock engine.

However, at the track day last Sunday I caught Keith Monaghan in the 6th run, and struggled to overtake his stock NB on the straight. Later he had the hide to accuse me of sledging! I was flat out, really I was Keith! :-)

The car has adjustable coilovers & swaybars, and aero from a front bar and a wing, so for now, the handling is sorted.
The driver can always improve of course, but that takes time, lots of time.

So, the time has come to add some horsepower.

The car is a 1998 JDM Roadster RS (same as our 10AE), with just over 100k kms, a pod air intake, a Mazspeed muffler (that came on the car), and the cat has been removed. It is a dedicated track car and can never be registered.

My preference is to improve the power gradually,with a step each year or so, while leaving the option open to go turbo later (I said LATER Dann :-). For now I want to keep the car eligible for CAMS 2B and for NSW Supersprint 4B or 3B (with the wing removed).

So here is the plan:

Step 1. Front to back race exhaust + ECU + dyno tune
Do this immediately, ideally before the FOSC meeting at SMP in 4ish weeks.

4-1 headers seem to be preferred over 4-2-1 for track use, for better potential top end.
More noise is ok, but it still needs to pass the 94db (?) limit at places like Marulan.
Cost seems to be around $1000 for a full system

The 2 ECU options seem to be Adaptronic or Megasquirt.
Adaptronic is supported by my local MX-5 specialist, and will cost $1500ish, including a wide band sensor.
Megasquirt appears to have more potential, and should cost a bit less, say $1000ish, but I don't know of anyone in Sydney that can do dyno tuning with a Megasquirt. Any suggestions?
In both cases a plug-and-play solution is desirable so that it is possible to switch back to the original ECU in case of teething problems.
It is also desirable to get data for logging, and to have an easy way to switch maps to reduce power, for example if other less-experienced members of the family drive the car. I can't have them beating my times!

Step 2. Cams + head cleanup + dyno re-tune
Probably do this late 2014
No solid ideas yet

Step 3. Probably turbo
Probably late 2015, if ever
Will probably do bottom end rebuild for strength/reliability, plus looking at brakes, gearbox strength.
Too far away to worry about the details yet.

This plan is based on reading threads in this forum and talking to a few people.

Please offer any constructive criticism of my plan, or suggestions, eg Megasquirt tuning

Thanks
David

I'd be inclined to do the cams at the same time as the Dyno tune with the ECU. You can always sell the cams later to upgrade to more suitable turbo cams.

ohh yeah David, one other piece of advice in addition to my pm - crawl into the bunker, you are about to get bombarded with ideas I would imagine ;)

I should have my car done by FOSC which is pretty much exactly along the lines of your ideas, you can check it out there.

You missed step 1

Change the diff ratio to 4.3 : 1 unless i missed it and the limited edition got the 4.3 diff?

Have a look here http://mx5cartalk.com/forum/viewtopic.php?p=762093#p762093 it has only just started to go off topic so it is still fresh...

2B will allow you to go to 85.5mm pistons and other aero mods as well as ITB's and you will more than likley need to do this be be competetive.

His is a road car though, no? Different builds.

mazmad wrote:His is a road car though, no? Different builds.

True, but the logic is the same for the engine etc build. The OP gets to send the car on an extreme diet and does not have to worry about emissions laws.

David, have you absolutely reduced as much weight on the car as possible? Your two Sparco Sprint Vs (and BOTH on sliding rails) do weigh quite a bit. All the sound proofing out? I'd also go for lighter wheels and carbon hardtop. These mods should still keep you in the same class without subjecting yourself to class penalties, correct?

One thing I've realised tinkering with my cars in the past...a 25bhp gain on an equivalent car isn't necessarily going to give you the ability to trot past the other car on the straight.

That said, having seen how poorly constructed the stock headers are, I'm sure you'd get some top end gains with a good set of headers.

I'd also go for a 4.1 or 4.3 final drive...can't remember but you're on a 6 speed box correct?

Re Magpie:............ True. But torque needs for a road car are different, and you wouldn't necessarily need to beef the bottom end in the same way or add acu-sump etc.

4.3

Windows and carpet and HVAC out. (if I need to mention pass seat or stereo you will never get it )

13:1 comp.

Medievil weapon looking cams.

Built head.

E85.

I would just copy the crusher build if it were my car, basically.

Dann

sailaholic wrote:You missed step 1

Change the diff ratio to 4.3 : 1 unless i missed it and the limited edition got the 4.3 diff?

It has a 3.9 + 6-speed
The 4.3 + 6-speed is an interesting idea, although I would have to research how it works at Wakefield and the SMP tracks.
I know someone who went from a 5-speed + 3.9 to a 6-speed + 4.1, and that did not work as at some points on those tracks, so I am cautious.

I hope you had a good look at Beavis's car on the weekend. JDM NB8B with coilovers, 225/45R15 Nittos, good alignment, pretty stock engine and running gear except for exhaust and pod, enthusiastic weight reduction and a lot of seat time.

1:10.1 and 162kmh Vmax on the main straight. Getting out of the corners faster is as good as power and much more fun.

Pass seat has to stay for 2f race regs. and also for supersprints 2b David I think?

Apu wrote:David, have you absolutely reduced as much weight on the car as possible? Your two Sparco Sprint Vs (and BOTH on sliding rails) do weigh quite a bit. All the sound proofing out? I'd also go for lighter wheels and carbon hardtop. These mods should still keep you
in the same class without subjecting yourself to class penalties, correct?

The interior and insulation is gone.
The 2 seats and runners have to stay to make the car usable by other members of the family and for driver training, although the passenger seat could come out for sprint events.
My wheels are already quite good, and the carbon hardtop is just too much money.
Yes, those changes would not affect my supersprint class.

Apu wrote:I'd also go for a 4.1 or 4.3 final drive...can't remember but you're on a 6 speed box correct?

6-speed and 3.9 diff.
4.3 could be a possibility, although I need to research how well it works at the local tracks.

mazmad wrote:Pass seat has to stay for 2f race regs. and also for supersprints 2b David I think?

Correct, as supersprint 2B is for registered cars.