5 replies to this topic

[123brez]

Hi im just in the process of stripping a BP4W engine down to rebuild for a turbo conversion.

 

Just wandering if anyone can recommend some rods and pistons for the build which i'm hoping to get to around 300-350bhp and want it to be reliable.

 

I'm also wandering which head gasket to use and oil pump. 

 

Sorry i'm new to mx5's. I have been reading up but unsure what CR etc I want to be going for.

 

Cheers

 

 

[boosted]

Id head to the Bofi website see what there selling or give them a ring.

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[Cliddoris]

https://bofiracing.c...x5-miata-alive/

For 300bhp I'd just replace the bearings, uprate the rods for something cheap and cheerful like max speeding rods, I'd keep stock pistons and use the money for a harmonic damper as they're a weak point.

But that article is worth a read.

I don't know which model mx5 you have, but realistically around 300+ bhp you should be looking at a 6 speed box also.

If it were me I'd be doing the following for 300bhp

Full gasket/seals
Max speeding rods
Acl bearings
Stock pistons
Arp head studs
Boundary oil pump
Harmonic damper
6 speed box

If you're looking the higher end of your goals then you should also be looking at pistons.
I imagine a stock head gasket is fine at those power levels, buy you could throw a comerica in there since it'll have to be changed anyway.

[jon]

You could probably pick one of the two between the Boundary oil pump and the Harmonic damper - the damper is to stop the standard oil pump from destroying itself, so if you change the pump it's less important.

 

Likewise the ARP head studs aren't needed until you are running a LOT of boost, the standard ones are fine. 

 

I'd probably take the savings from not needing those and put the money into an uprated fuel pump with better wiring, 6 speed box/diff to suit and an uprated clutch.. You are also likely need to budget for an oil cooler and a bigger rad if you want to drive it hard... 

[boosted]

Mines recently converted to turbo with a safe map off 226bhp.. the cars has supporting mods of thermostatic controlled oil cooler. Larger rad with coolant reroute and uprated fuel pump.
Tbh...at 226 bhp its rapid i dont really think i need any more. I thought it might just be quick in the lower gears but in all gears it pulls and pulls. Its running low psi on a little Garrett t2545r..
And if anything happens i can just drop another £100 engine in.
As your new to 5s...can i suggest trying a standard engine conversion first before big expense 300bhp 1?

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[jon]

Very true - a 300-350 BHP '5 is incredibly rapid to the point of requiring a whole lot of restraint to drive safely on the roads.

 

Probably the most 'fun' iteration of my car was a GT2554 with about 225BHP - very responsive, no lag and enough power to make you smile without feeling your car wants to kill you at any speed in any gear