Garret GT2871r MX5 engine conversion?


1999 MX5

This is my first post.
I used to own a 180rwkw Nissan 180sx, but this time I'm looking at getting a street legal mx5 that I can take to track days. The car I'm looking at is a stock 2003 Mazda mx5 and I'm wondering whether I could get an upgraded long block and put a Garret GT2871r turbo conversion on it for just under 300rwkw or whether it would be better to get an engine conversion to a Nissan sr20det, Mitsubishi evo 4G63 turbo or maybe upgrade to the Mazda mzr 2.5L 5L-VE motor and turbocharged that.

Queensland road rules limit turbo charged engine conversions to 3 times the weight of the car, so the maximum size engine I could put in the car is about 3000cc or 3L. This means I could try squeezing in an rb25det, rb30det or even a 2jzgte, but I think this would ruin the weight distribution with more weight over the front wheels and it would probably be more difficult to fit.

The car will not be my daily driver so it's OK if it's off the road for months at a time.

I'm definitely not the first person to go down this road so I'm hoping you guys have some advice for me. I'm really looking for a setup that has the same sort of response as the Garret GT2871r has on the SR20DET and that sort of power level. What would be the best option or is there other better options I haven't considered?
Hello and welcome :)

I live a bit down the road in the big smoke and have quite a bit of experience with 4g63's with 3 times the stock power.

I see you are quoting the road rules so it seems that you are not building a track only car so if it is registered then it needs to be mod / blue plated / engineered to be legal especially should it be involved in a crash.

I also strongly suggest that you contact your insurer with your total modification list as they have every right to be made fully aware of exactly what they are being asked to cover under the policy to see if they still want to continue doing business with you BEFORE you start and GET IT IN WRITING and file it away for future reference if needed. Been there done that.

I would forget any 6 cyl conversion as IMO that would upset the wonderful chassis balance UNLESS it will be a drag car.

I see you mention SR20 motor and unless it's a NEO version they have IMHO poorly designed OHC mechanicals that has caused many problems with the Y shaped rockers failing / jumping off if they exceed 7000 revs so it would not be on my short list of desirable motors.

I note that you haven't mentioned a BRAKE UPGRADE and that should be one of the FIRST things on any list considering your power goals.

I am a recent convert to Honda and IF you wanted to stay with NA power then you should consider installing an F20C out of an S2000 and 6 speed box that puts put 220 hp and has a factory 8700 red line and would not upset the front to rear balance of a great handling car.

PS If you want to chat message me with your contact details.

Thank you for taking the time to reply.

I'm really just fantasizing at this stage as I don't have all the money together, but a man has to have a hobby and there is just something about powerful cars that keeps me wanting more. It has been over 15 years since I had the last car built and it seems that the Japanese Nissan cars I love have gone up so much in value, which is why I am considering the light weight rear wheel drive mx5 as a build platform. I am also considering other rear wheel drive cars such as the Toyota 86 or the Nissan 370zx, but I want to keep the weight as low as possible and there's something a little off putting about the shape of the 370zx to me.

Last time I only got the 180sx onto the track at Morgan Park Raceway once before I sold it to continue my study overseas, but this time I'm hoping to make at least a few trips to the track each year.

I do want the car to be road registered to go for a drive when I need to take a break, so I will be getting it engineered and get a mod/ blue plate for it. I read somewhere that it might cost up to $3000 to get a blue plate for a heavily modified car in Qld.

The following are the approved modification codes in NCOP for use in Queensland:
Section LA – Engine (refer to the VSIs for variation to the national version)
LA1: Equivalent Engine Installation
LA2: Performance Engine Installation
LA3: Supercharger and Turbo Charger Installation
LA4: Engine Modifications Section

LB - Transmission
LB1: Transmission Substitution
LB2: Rear Axle Substitution Section

LG - Brakes
LG1: Brake System Conversion (Design)
LG2: Brake System Conversion Section
Section LK - Seating and Occupant Protection
LK1: Seat and Seatbelt Installation/Removal
LK2: Seat and Anchorage Certification
LK6: Child Restraint Anchorage Installation
LK8: Construction and Installation of One-Off Roll-bars and Roll-cages by Individuals
LK9: Design and Manufacture of Commercial Aftermarket Roll-bars, Roll-cages and Other Types of Roll Over Protection Systems (ROPS)
LK10: Installation of Aftermarket Roll-bars, Roll-cages and ROPS Section
Section LT - Test Procedures
LT1: Beam and Torsion Tests
LT2: Lane Change Manoeuvre Test
LT3: Exhaust Emissions – IM240 Test
LT4: Noise Test

I will be installing the modifications in the red text colour including a brake upgrade. I also noticed there is nothing about coil overs in the modifications codes or other suspension improvements. I have talked to an engineer about the coil overs and he said they should be approved though. I'm not sure how strict the emissions test and noise test is though, so I don't know whether a car with an increased engine size and a high flow exhaust will pass. Something like the varex muffler might help though.

I have spoken to a number of insurers and I have yet to find one that will insure the car. Who would you recommend for insurance for a heavily modified car in Queensland for full comprehensive insurance? and for track day insurance?
Well where do I start?

1 The engine must not be older than the car

2 Adding a turbo to a non turbo car may cause problems with it's max power but my old car had over 3 tomes the factory power and I never had to produce my dyno results BUT that was many years ago and things may have changed.

3 I had a RX7 box in my Mitsubishi and the speedo cable and rev light switch fitted in with no mods .

4 I had Nissan 4 piston calipers clamping larger Honda discs with a Willwood bias adjuster that was mounted in the engine bay as it would not have been approved if it was in the cabin where say a passenger might fiddle with it. I needed it so as to get the full benefit of the bigger front brakes by reducing pressure to the rear as they were locking and the upgraded fronts were working at say only at say 80% stopping power.

5 I had a 4 point harness and but had to keep the factory belts in place for road use to be road legal.

6 I had no cage but you can have a full cage IF the side intrusion bars are removable and not in place at inspection.

7 I never had an emissions or noise test and coilovers were ok.

8 May I suggest that you have a quiet rear muffler for street duties so as not to attract unwanted attention fitted using V band joint so it is easily removed and replaced with a straight pipe for race days.

9 Insurance have you tried a broker ?

I am was insured for many years up until I sold the car for an agreed sum but for limited road use only as it was not a daily car and had possession of the wreck BUT no track cover.
Thanks heaps TCJBOLDIE.

1. This makes sense
2. I have never heard of someone having to produce dyno sheets either.
3. What does rx7 box mean?
4. That sounds cool. I wondered how brake bias kits were setup. I had front Z32 four caliper pistons and slotted z32 rotors on the 180sx.
You can see the car here
engine bay
5. That's a good idea. I think I will do the same.
6. I asked an engineer about this a couple of weeks ago and he said:
Is a full roll cage street legal in Queensland? No - a cage cannot come forward of the driver
7. Cool thanks.
8. Yeah on the streets I would like to go unnoticed, so that's a good idea.
9. I have tried insurance brokers and the ones that I have talked to so far have said they don't specialize in race cars. One told me about I tried to contact them, but haven't heard back.
I used to be insured through "Just Cars" I think.

Thanks so much again for your help. It's nice to have a break to talk about cars.
RX7 gearbox fitted to a different make of car.

You need to have a more detailed chat with the engineer as to the best of my knowledge it is the side anti intrusion bars that make it difficult to get in and out is the reason they will say no but install one with the removable side not in place when it is inspected you may get a different result.

There are many registered rally cars with full cages.

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