my new hi performance turbo engine build

sprx3 · Postby **sprx3** » Wed Sep 09, 2009 9:38 pm

Hey Guys & girls,

Its been ages since i did any posting on the forum & as I have a bit of news I thought i'd jump in again & say g'day....

As some may know i have an NB8A with an avo kit on it & a few weeks ago the tired motor decided that it didnt like the crank pulley anymore & the crank & pulley had a fight..... this was noticed by timing issues & missing and generally running like a pig (no offence to people). When i popped the bonnet i noticed a harmonic balancer that wanted to do oval work instead of circle work.

I inspected both & after taking off a loose crank pulley bolt realised that this had been a good fight, the keyway was stretched on the crank & the crank pulley was a mess, as for the woodruff key.... it looked like it had been in a plane crash. As the motor was low in compression I looked at replacement engines & for an NB8A they are far & few & even high km engines fetch big money. almost 2 weeks went by as i spoke to people all over the country looking for an engine that was within the amount that i wanted to pay & found nothing.

I decided to do some homework to see just how much inter-change-ability there was between the BP engine & after speaking to many so called experts was told that mx5's have different cranks & that i would have to buy an mx5 one, I was also told the same thing about the crank pulley and like everything else mx5 the prices for the two parts even made bill gates stand up & ask WTF.

the turbo forum in the states provided some really useful info which made me call mazda up & compare 2 vehicles engines in particular. One was a front wheel drive variant of the BP engine & the other the mx5. Speaking to a very helpful chap at City Mazda in Melbourne, we compared engine part numbers with the 323 & the mx5, we found that the part numbers for the crank are the same but the pulleys where different. We also looked at the line drawings of the parts & they looked identical. This was a great start.

I knew of a 323 bottom end that had 150k on it & was $100. I went & put the money down & had it the next morning. Inspecting both pulleys there is very little or no difference at all. I pulled both mine & the new one apart & fitted my striker plate on the new unit & put it aside...

I then started pulling the new bottom end apart & found that it had spun its bearings, it looked like it had been rebuilt at some stage as the bearings were not original parts. The crank did have marks in it BUT nothing that wouldn’t machine out & the key way was still intact & mated with the woodruff key perfectly.

I sent all the good bits to get machined up & the head to get reco’d & cleaned up. I also searched high & low for a clutch that would hold the power i was thinking the engine would now make, previously we got 145rwkw at 11psi & with the bits i am putting into the engine I knew it should make more. Again after searching hi & low I came across a place in Cambellfield called Highway clutch. I would Highly recommend them as their service, patience & knowledge was unbeatable. We were able to put together a clutch that “should” be fantastic to drive everyday in traffic & will pull the foreskin off a ..... anyway. The price for this package including flywheel machining was $310, & im talking well known brands that others wanted $650 for, better still mine was a custom package with mixed parts that we clamp force tested before saying yes, we went through 4 different pressure plates before we found what we thought would work best with the clutch plate & clutch system. Great end result & am glad i didn’t go the Flyin Miata clutch which was over double the price & thought was my only real option.

After much debating (with myself mostly) i decided on belfab H-beam rods & supertech 9.5:1 .20 thou over pistons, Although many have said that 9.5 is to high I never had any issues with pinging & we had not played with timing too much when tuning. Also if your planning on buying Supertechs or most forged pistons make sure you read the fine print. Supertech & wiseco both set their compression ratio’s with a .60 thou decking. Decking the block that much will effect your timing & you will need adjustable cam gears to compensate. Without decking by 9.5’s will end up as 9.2’s which will be a fantastic compromise between off boost power & on boost power.

Im still waiting on the pistons & rods to arrive from the states as that is by far the cheapest place to get them from. But most of the other work has been done & once we see the pistons we can bore & hone the block & start putting it together.

Im hoping to see you all at garage in 2-3 weeks with the new setup, just a shame i need to do 3000km to run it all in. If your wondering about the power it should make, all going well we should see 180-190rwkw on 15psi & i think most will tell me thats being conservative, Time will tell........ oh & cost wise including the new clutch it should come in at just over 1k from what the average 2nd hand NB8A engines were quoted at.

93_Clubman · Postby **93_Clubman** » Fri Sep 11, 2009 2:55 pm

hey great post - tks for sharing - like quite a few forumites that have done some reading, I suspected there weren't quite as many differences as has been thought, but evidence was only anecdotal.

sprx3 · Postby **sprx3** » Wed Sep 23, 2009 3:47 pm

well its been a few weeks now & parts are starting to roll in, most of the machine work is done & we were waiting on pistons to bore & hone the block correctly.

well this morning the package came in from Belfab, although a little later then expected as someone forgot to send it.

here are some pics of the parts.

sprx3 · Postby **sprx3** » Wed Sep 23, 2009 4:33 pm

hmmmm.... not very happy with Belfab at the momment, just checked the part numbers of the pistons & they sent me 11:1 comp & not the 9.5:1's i asked for........

back to the waiting game

16bit · Postby **16bit** » Thu Sep 24, 2009 11:06 am

just run avgas :lol:

adamjp · Postby **adamjp** » Mon Sep 28, 2009 9:38 pm

sprx3 wrote:hmmmm.... not very happy with Belfab at the momment, just checked the part numbers of the pistons & they sent me 11:1 comp & not the 9.5:1's i asked for........

back to the waiting game

I was going to say...for 9.5:1 pistons those puppies have some serious lumps on them!

Good luck with the service from Belfab....their products are very good, but the service was not so flash when I dealt with them. Hopefully it has changed.

Szemen · Postby **Szemen** » Wed Sep 30, 2009 12:06 pm

Might as well just go n/a with ITBs now since you have the pistons

sprx3 · Postby **sprx3** » Thu Oct 01, 2009 6:08 pm

Szemen wrote:Might as well just go n/a with ITBs now since you have the pistons

so what do i do with my avo turbo set up then........... :shock:

i think i'll say with the 9.5's

i just realised that i dont have pics of the clutch up so here is one.

I also bit the bullet & bought redline shockproof lightweight. Although there is a lot of good & bad talk about it & i personally think that spending that much on gearbox & diff oil is silly BUT im hoping im proved wrong. Time will tell.

Belfab have finally posted the pistons a week after the order & im now tracking it home. At this stage i should have them by Monday or Tuesday I HOPE.

sprx3 · Postby **sprx3** » Fri Oct 02, 2009 6:41 pm

Been looking at ARP head studs & mains studs over the past day or two. Tracked some down today & will have them in my hands shortly, Much better price then anyone in the states & aus can do so if you need some in the future let me know.

pics to come shortly

Im also debating getting some better valve springs since im still waiting around for parts. If i get the valve springs the motor will be good for a higher redline which i dont really need but at the same time would be good insurance.

Im not sure on which valve springs to go for though so any thoughts would be great. supertechs seem to be the direction im looking at though.