Turbo BP1.8 - Couple questions
 

Looking to get into a NB(99 or 00) miata soon here and was researching about going turbo with it aswell. I have a couple questions I seem to not be able to find answers to.

1. Turbo selection - I currently have a GT2860RS with a .86 exhaust housing on my SR20, I know on SRs these turbos will top out around 360whp while using the internal gate. My power goals are 320whp-340whp, will my current turbo get me there on the BP?

2. This kinda stems from the above question but it seems that the BP motor really was never designed with FI in mind, I have done a bit of researching and seems I won't be able to break 300whp with my disco, what is the limiting factor on these motors, head? Intake manifold? Is there a 'wall' you hit with these motor regardless of turbo?

3. The HKS turbo manifold caught my eye for being best for your buck when you can find them, any other manifolds that you guys suggest for an internally gated T2 turbo? Rather not spend 500 bucks on a cast manifold if I don't have to.

4. Fuel - I know Nissan FPRs will die out after time when using a higher flowing pump such as a Walbro 255. Same way with the miata FPR? Also injector sizing for my power goals, I was thinking 600cc @ 3bar would be enough fuel with a walbro.

5. Seems that the best route would be getting the 3.636 ring and pinion to try and get the longest gears possible, anyone have any reasons against this?


I'm sure I'll have more questions for you guys as time goes on, coming from the SR, the BP seems like a hassle to make power on. Hope the weight of the miata makes up for it.

psst - don't tell Savington about this 300whp limitation, maybe you better save your moola and just go back to your nice-un

-2860 will top out at 300 or just a but over.
-yes it was, it has a very strong cast iron block and takes to decent levels of boost for long periods of time well, its when you try to make huge torque that things start breaking. rods mostly.
-absurdflow and artech. nuff said. best out there.
-get a wally and 600's and you'll hit your goal just fine on stock fpr.
-up to you. 3.6 is def nice tho

18psi, thanks for the reply.

What is the main cause of low whp compared to other motors?

I'm not sure what motors you are looking at, but typically on most 4 cylinders with a 2860 300whp would be considered good. Most honda's have to go to the gt30xx to get into 400+ range.

Less displacement/poor head flow.
The 99-00 have a better flowing head than the earlier and later years, but still nowhere near that of a honda or something like that.

I don't know why you're stuck on a power figure alone though. Its more about hp/lb and a miata is a good chunk lighter than any pos 240. A healthy 300whp miata is fun as shit, and will absolutely rape a 300whp 240.

If you want ungodly hp figures go pick up an s2000 and boost that. 500-600 is achievable on stock block

I put down 307whp @ 13psi with a 2860rs on my fwd SR, never did get a chance to dyno it at 18psi though.

It was curiosity is all, I didn't know if the BP had a wall you need to start replacing the intake manifold/porting the head to get past.

No wall.
You can get to 300-350 on a 99+ motor with just upgraded rods. A bunch here have done it. Past that you need to start upgrading a bunch of things, including pump gears, intake mani, coolant reroute, etc etc etc.

Depends on what you want.
A street car is 2x easier to make big numbers on. It sees nowhere near the amount of abuse and stress as a race car.

1. not sure
2. Incorrect. This motor was originally intended for turbo charging. 9.0 compression in the 1.6, goes down to 8.6 compression in the NA 1.8s, and then back up to 9.0/9.5? in the 99/00 NB. they also churbo'd the MSM.
3. 18psi covered this.
4. whatever you do, don't change the stock sock and make sure you put it in the correct orientation.
5. 3.6 gears are a good choice. At those power levels, you will need to plan for a 6-speed. As most people will tell you, the 1st gear is practically useless on the N/A BP, so you will pretty much be driving a 5 speed in anyway.

Plenty of people have over 300 whp, but it gets reallly expensive up there. budget yourself, but do A LOT of reading before then.

94-97 nas come with 9.1 not 8.6 iirc

:loser: you are probably right actually.

of course:
http://forum.miata.net/vb/showthread.php?t=205061