MX5 build tip wanted.

Cook_NA_Turbo

Cook_NA_Turbo

Member
Im in the process of building a turbo'd mx5 which I hope to take to driftcup/retroDC next season and Im wanting some tips from people that skid them about what mods helped and didnt help them. Power should be about 300bhp, fingers crossed everything goes ok at the mappers, so dont need power mods.

Hubs are going to be chopped and a 1.8 open diff welded and cage to bdc spec. So far thats all my thoughts.

Fire away please.

Ben
 
300bhp breaks a lot of shit on a turbo mx5. Off the top of my head you will need.

Forged con rods (or preferable a built engine).
Uprated gearbox internals. Or a six speed might handle it at a push for a few sessions.

Look at reinforcing the diff area (seen some break at higher power levels as the diff/cradle is ally)

Seats
Harness
Cage
Coilovers
4mm lock washers helped, never bothered with hubs on mine.

Strongly recommended an ally rad with a regularly rad fan + a/c fan wired to come on together.

Frame rails with a butterfly brace make a huge difference to the chassis, although not sure if it will along side the cage.

Check your ratios for the 1.8 diff as some of the open ones are bloody gay and make the gearing shit. I had to swap a couple in my mk1 due to not realising this.
 
Yeh engine is fully forged, mk2.5 lump and head with billet oil pump with all the rest to keep it cool and sorted etc.

Frame rails i have, its going to get a cage anyway
.
6speed box i have. And hoping it should be ok for a good few rounds if im not kicking it 24/7.

Diff area is a good shout!!! First ive heard of this and i will do some research on it!! Maybe some kind of support linked to the cage.

Also didn't know the 1.8 diffs had different ratios?
 
Diff problems as stated, I think Tom from Flatout Factory has broken a few diff casings with a welder, always one side in particular (I think?).

My 6 speed box can be a pain to select 3rd accurately. Might be worth blocking 5th & 6th off with a removable bar to prevent mis-shifting on tracks when you won't need them.

Ian. :)
 
IMO cooling on an MX5 once big power and drifting sucks ass. Fine on the road, wank when driving.

Look at the frontal area of an MX5, next to no inlets, and it's the lack of places for air to go out is the bigger issue.

My old MX5, roughly 270bhp/270lbft, 100% fine on the road even at 160mph, but drifting, until I vastly modified the cooling, it overheated quick as fuck.

More holes for the air to get in, ducting to make the air go thru the coolers not around it, and holes in the bonnet behind the coolers (but before the engine) for the air to get back out again.

I ran a Cosworth rear diff so I had no problems, so dunno about them. From what I've seen solidly mounted MX5 diffs/boxes/engines are the biggest reason the diff mounts snap a lot.

Modified hubs from Mintfab or somewhere are a must, will need fairly low offset wheels and possibly longer brake lines (s14 ones fit) due to the new mega lock (lines get mega stretched).
I'd not add lock washer spacers once you got the hubs, the hubs give 99% of the extra lock, and don't fuck up the PAS like washers did on all of mine.

Apart from that, learn to drive it, that's the key with MX5s.
 
I'm 90% sure there are a couple ratios, as mine sucked ass on my first mk1, gears were stupidly spaced out. Think it's 4.1 and 4.3 are the two but don't quote me on that.

I'd just recommend bracing the hell out of it and seeing how it goes, maybe just turn the boost down to a lower setting for long sessions?

As stated for cooling a big ass rad, 2x OEM leccy fans, not the shite off eBay people run, my 90 year old nan could blow more air than them things.

Cut some holes in the front bumper, and the bumper bar (as it blocks airflow too) should do the job.

Driveshafts can snap too, not sure on uprated items, think it's possible to use rx7 gear on the back if need be
 
Thanks people, getting some good info.

Cooling wise car is running a big ally rad, coolant re-route and a large oil cooler. Could always go bigger on the cooler if needs be as ive left space above the intercooler for a deeper one.


I have manual rack, is there any ratio difference between manual and pas ones?

It looks like diffs and shafts are going to be a ballache.

stav how did you run the cosworth diff, is it a big job fitting?
 
Pas rack is a quicker ratio, Google the proper way to depower a pas rack
 
Don't run a manual rack. Run a PAS one depowered if you like, but not a manual.

Cosworth diff is a big job, yes. Thankfully I didn't do it. And they fitted the Cosworth engine and gearbox too, so it was all good.
 
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