I'll most likely buy an engine and transmission from Ebay, where someone has decided to upgrade from a 1.6 to a 1.8, then lost the enthusiasm. I've seen a few of these go for about £250 in recent weeks. That's the engine, ancillaries and transmission. Bargain.

Regarding building the engine, I'm undecided whether or not I should fit forged rods and pistons, with a reduced CR. I'd like to avoid spending money, but I'd also like it to run without exploding!

Cheers

For less than 250HP, you can use stock bottom end.

So the little mazda engine will take a turbocharging to 250hp without any mods to CR, using standard rods and crank, not even changing out the big end bolts??
Forgive my scepticism, but I was expecting to have to at least skim the pistons.

cheers
Laurence

Why skepticism? That's what an awful lot of MX5 owners do.

Note you can't do this with cheap hacks, you need a full ECU and appropriately sized injectors.

But you don't have to touch the motor for 250bhp

Let it be said, however, that for track duty, many people upgrade the rods even in naturally aspirated cars, let alone turbo cars. I don't think you'll find a reliable turbo'd BP with stock rods. Overrev on downshifts into turns or other tomfoolery and you'll pop the stock rods.

I'd say if it's not too much of a stretch on the budget, throw some stronger rods in there. You don't need to mess with the pistons but you can if you like.

That's great news, so I can spend all my money on the management system, turbo, clutch and flywheel instead. Next question is which turbo to choose. If I want 200HP at the wheels, what's the best turbo to go for? I'm weighing up between a KKK K04 and a T25 from a 200sx. I want the fastest spooling turbo that is cheaply available second hand in the UK. From reading other posts, the KKKs are not considered to be as good as the Garrett, yet in the Volvo T5, switching from Garrett to KKK improved performance (at the cost of longevity).

Cheers

I laughed when i read super strong 5 speed but anyway. it's enough for your goals.

If you're racing you should get rods and stronger valve springs. the stock pistons should be fine as long as you do in fact stay around 200. keep an eye on what motor you choose if you have a compression ratio in mind. I'm too lazy to look it up but they are somewhere close to 9:1 early on and then go to 9.5:1 and then to 10:1.

The most popular turbo fitment for that range is the gt2554 or gt2560

A friend of mine made 200hp with a genuine Garrett GT2554R on an internally stock 95 1.8, so that's the earlier 1.8 with the lesser head. I believe Shuiend or Y8S is/was making 200+hp with a T25 and a stock block, they love posting the dyno plot in every turbo selection discussion thread. I'm sure it will show up here eventually.

If ALL you want is 200-225hp, I'd say used Nissan T25, or Garrett GT2554R or GT2560R for stock bottom end friendly power. The journal bearing Nissan SR20 T25 flanged turbos are plentiful, cheap, and rebuildable at home provided the housings don't eat the wheels. Journal bearing looses you ~300-ish rpm worth of spool, but that's not going to matter much with such a small turbo and a 7,000-7,200rpm redline. The T25 flange also gives you a lot of turbo options if you want to go bigger/ball bearing in the future.

Ok, so its a t25 turbo and and earlier, non vvt engine with a lower compression ratio (9:1) and forged rods and uprated valve springs. This all seems sensible and relatively low cost so far. Next is which clutch (ok I'm used to a sintered clutch so I'd consider anything as driveable...) . I assume I'll be onto new injectors at this point, but I can check which ones from the intro post sticky.
We're almost there with the spec. Any comments on camshafts?

Cheers

My write up is not up to date. Rx8 injectors or better

Yes, you'll need some. A pair would be best.

Serious answer: why bother with anything but stock? Plenty of builds around here with stock cams way over 200 WHP. Don't mess with success.

200hp = stock plus little boost

RX8 "yellow" = Denso 195500-4450

450cc/min @ 3 bar/43.5psi (According to 949Racing)
524cc/min @ 4 bar/58.8psi (According to 949Racing)

RX8 "blue" = Denso 195500-4460

528cc/min @ 2.25 bar/32.6psi (according to Injector Rehab)
610cc/min @ 3 bar/43.5psi (using the RC Injector Calculator)
709cc/min @ 4 bar/58.8psi (using the RC Injector Calculator)

Both are EV6 style injectors that are lightyears ahead of the old RX7 "red" 550cc EV1 injector technology, and can be found used very inexpensively. Watch out though, there are known to be Chinese knockoffs on eBay. Deatschwerks also sells drop-in EV6/Denso units, plus they are a forum sponsor.

If you want ultra-baller injectors, check out EV14 style units from somewhere like Injector Dynamics or Fuel Injector Clinic. With a proper ECU with enough resolution, a massive EV14 style injector is not an issue. We have guys on this forum running ID1000cc injectors on 1.8s with stellar idle control. Check out 949Racing or Trackspeed Engineering.

There are other companies such a FiveO Motorsport that also sell EV14s, but we have had members on here with less than positive results from this company. Hustler may be able to provide some details...

Leave the cams alone. I think you already get the more better factory BP5A-12-420 in your EU/UK spec non VVT engines, plus the unobtanium "square top" intake manifold that we (on this side of the pond) all lust over.

Do not waste money and time on rods and valvesprings for 200whp. Many people here track their cars for years with stock engines at over 200whp with no modifications to the block. There have been street cars with 280whp+ on stock blocks on this forum (Leatherface24, pdexta, etc.) that have run for years on the street with a good tune. Rods and valvesprings are only insurance in case you miss a shift and overrev the engine severely. And if you do overrev it and break it you are simply forged pistons, rods, and a billet oil pump away from turning the power up to 300whp+ if you desire.

Does anyone have list of engines, compression ratios and model number by year? Also can someone recommend an uprated oil pump with take off for a cooler?
Thanks for all the advice so far, it is extremely helpful.

Cheers.

only aftermarket oil pump is from boundry engineering (link is top right of this page). the stock one is good for your goals... just like six said they are for insurance. You can get by on stock everything most likely. It's almost easier and cheaper to buy motors and blow them up. Coolant reroute is a no brainer though. you definitely want to do that.

I agree with everything six said but would still do rods and springs in any race application. I wouldn't put it past myself to miss a shift and I don't really like pulling and disassembling motors. The motors really are good stock for ~200 all day long if they have a good tune and aren't over revved.

I'll have to weigh up the cost of rods, valve springs and pistons against the cost of trailing the car to the track. I'd prefer to build the motor strong from the start, otherwise knowing my luck it will blow up on the first outing in summer and not get repaired until it deep dark winter time.

Why are the costs of rods springs and pistons weighed against the cost of trailering? I'm not seeing the connection.

Up front cost of rods/pistons/springs -vs- cost of a tow home?

I <3 AAA Taxi :giggle: