Turbo Choice?
 

Hi All,

I was hopeful that I maybe able to get some advice regarding turbocharger selection for my car?

Over the last 12 months I have built and installed a forged VVT engine into my 96 NA with the aim of turbocharging it - I have built engines before but am a complete novice with forced induction! The engine has already done 2k miles and is fully fit and ready for abuse, I have put as much of the spec of the engine/car at the bottom of this post as I can remember.

I'm in based in the UK so only have access to regular 98 RON we get over here - according to Google that's 94 octane in the US. Power wise I'm aiming to be limited by the 6 Speed gearbox - so low to mid 300's seems to be the numbers according to the masses. The default choice seems to be an EFR 6258 but I was hoping for some alternative suggestions, I would love the EFR but financially its a stretch for me, what alternatives would you guys recommend/are there any worth considering?

Kraken seems to be the best manifold bet but which, low mount vs side mount - is the performance benefit worth the extra fitment grief of a low mount?

What would you guys recommend? Many thanks and sorry for a first post question!

2001 1.8 VVT Engine
Manley rods
Supertech 83.5mm pistons, 8.8 CR
ARP main and head studs
Fluidampr
Boundary Stage 2 Oil pump
ACL race bearings, 0.0020" clearances
Catcams Valve Springs
Mild porting & Flat Top Manifold
Stock Cams + Valves
Coolant reroute + Ali Rad
OEM Head Gasket
Innovative Engine Mounts
ME442 ECU + R8 Cops
BOFI Racing Clutch
Ultra leightweight flywheel
6 Speed Transmission
3.6 Torsen Type 2 Diff - Casing Reinforced

Look into Pulsar GTX2867 gen2 turbos, if youre tight on money. Those will hit 300whp on pump gas without being at the absolute limit because of the bigger turbine. You will be spooling a bit later, but nothing crazy and with head room in the future.
These are good for 400whp.

Kraken top mount is very good, wouldn't pay the extra $$$ for low mount.

If you have the money go EFR, no question.
I also think 300whp is enough for the street. 4th gear I could put some power down today, 6°c, dry

Hey,
from what you're describing, a Pulsar gtx2860r would be perfect for your needs. It's half the cost of a genuine garrett and performs amazingly close if not the same as.
I am a dealer so can get you competitive prices.

Your build list looks very nice; should support your goals with excellent reliability

I bought a Kraken full kit low mount with the Pulsar GTX2860.
Turbo Kit - Miata Turbo Forum - Boost cars, acquire cats.
Low mount has the best flow (most gentle radius) and is worth the mild cost increase IMO.
The manifold is the nicest cast manifold I've ever seen (40 years of experience).

The low mount has some draw backs. If you're running AC and PS the entrance into the compressor is difficult and requires a sharp 90-degree bend.
Without AC and PS it's not bad at all.
This interference is enough that I'm seriously considering the KPower electric PS to get rid of the PS pump.

I'm putting it on a MSM and with a proper shield (has to be custom made, Kraken does not offer this) it could be easily mistaken as "stock" by an inspection station.
It also keeps the heat generated by the system very low in the engine compartment and with the shield and a dedicated airflow path into it should reduce under-hood temps which can be a significant issue above 300hp.

The 3K plus kit I purchased came with a full 3" exhaust, all the connection tubes, intercooler, and blow off valve.
The hot side (manifold, exhaust) looks like it will support 500hp, absolutely beautiful!
IMO the intercooler is very nice but bit on the small side and the inexpensive blow off valve and the "airfilter" are not of the same quality as the rest of the kit.

If I had to do it again, I'd order the manifold, the Pulsar turbo, and the full exhaust then source the other stuff myself.

The Pulsar turbo looks nice, at the price point I got it for I'm happy.
The price difference between a real Garret GTX2860 and the EFR was small enough that I'd have gone EFR over Garret.
If the Pulsar doesn't work out I will replace it with the EFR.
Had money not been a factor I'd have gone EFR from the start.
I'd still be using the Kraken hot side bits with the EFR however...

Hi Guys, thanks for taking the time to respond, it is really appreciated.
I'm pleased you all take the pulsar turbos seriously, I keep seeing them and wondering. The car is mainly a street car and with my lack of ambition to stick a BMW gearbox in/change 6 speeds as a service item it sounds like a pulsar GTX2860R would be my best bet vs the GTX2867R, lower spool times and a better torque curve presumably as well. I'm really keen to maximise the potential of the engine to justify the money I already have spent but don't have unlimited funds so this sounds like a good compromise.
Thanks Fergus

Remember your 98 octane fuel. I have a GTX2860 myself, but I run 102 octane all the time and have no det problems. I wouldn't run 23psi on 98 octane with the 60. Bigger turbo -> less detonation.

I've got a similar setup to you - forged VVT engine with a Garrett GTX2860 gen 1, based in the UK.

I made 300whp on a fairly safe tune on 97RON petrol (UK Super Unleaded - BP Ultimate) at 17.5PSI. I'm sure there is more in it if I mapped it for VPower / Tesco 99 and changed a few supporting things round, but like you I was a bit concerned over the strength of the 6 speed.

If you've not experienced 300whp in a '5, they are incredibly rapid and can be a bit of a handful - if it's cold and damp mine will go sideways at 70mph if you aren't careful.

I would go even further:
Tune on 97 and run 99 all the time

Thanks again for the advice gents, very good point about the fuel.

Jonboy I presume that you are using a 0.64 A/R housing?

I haven't had any experience of a 5 that powerful but I imagine its pretty wild!

Go .64, we all use it ;) think spool!

I've got a slightly different setup to most - 0.52 A/R TiAL v-band housing with an external wastegate, rather than the more common T25 fitment.

@der_vierte - that was the idea fuel wise. 97 RON is reasonably easy to get, but only a couple of chains offer anything higher, so make sure it's safe on 97 and then any extra is added insurance.

What are your power goals?

Hey, Could you share with me how you managed to route your charge pipe out of the turbo? I am on a 1990 chassis and have swapped a VVT into it with the lowmount + pulsar 2860. The subframe is right below the turbo so I am just curious how you routed everything and what you bought if you still have access to it?

If not, any info can be helpful!

Thank you!

Also fyi, I am thinking I need to adjust my turbo more towards the engine (it is pointing straight down right now.)

This is what I think needs to happen but I just wanted reconfirmation.
https://cimg4.ibsrv.net/gimg/www.mia...63a677ac0b.png

To clarify -- do you mean the cartridge or the compressor outlet? Basically, your drain should be near vertical, but the compressor outlet you can adjust to fit your charge pipes and to clear the frame rails

Not sure what the cartridge is but the compressor outlet. The place where pressurized air will travel from the turbo to the intercooler.

Thanks for the response!

I keep forgetting to post the picture with my message but this is the current angle. (Engine is in the car now but I have no good pictures of it and I am in the office.)


https://cimg5.ibsrv.net/gimg/www.mia...480ec7c976.png