998 turbo choice in relation to boost.
Turbo Mini Forums

Hi guys,
Iv been looking at compressor maps to make a choice for my 998 +40 (1030?)
The shortlist was the gt1544v and the kkk KP3, I was planning to run 10psi of boost but in both compressor maps the pressure ratio combined with the engines air flow doesn't reach what appears to be efficient spooling of the turbo.
(I hope that makes sense)
So....

Do I up the boost?

Or down size the turbo?

My comp ratio is 8.9-1

It's my first engine build so I dont want to blow it to pieces on start up!! And I don't want a laggy lump of an engine.

Any advice would be appreciated!!

What's it being used for

I believe the gt15 is a great turbo for a 998 others have used it to good success

It's mostly going to be used for a bit of fun in the summer. I don't want to go crazy with it because I would like it to be as reliable as possible. I'll take a look at the gt15 compressor map, I don't imagine it will be too difrent from the 1544.

I think I might need more boost!! Ha

The GT1548 is the same as the T2 as fitted to the R5 turbo. The GT1544 is quite a lot smaller.

From memory, the 44 would be getting inefficient around 10psi, the 48 is good for 12psi, maybe a little more.

I know nothing of the KKK turbo. I have used a IHI RHF3 (or RHF4, I can't remember), which was pretty decent for mid-range performance.

I liked the look of the turbo fitted to the 500 abarth which was an IHI RHF4

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

The turbo fitted to Shaunas 998T is a r5 t2 exhaust housing with a gt15 compressor, not sure on the exact details but on the rollers with a faulty bleed valve it was going up tob14psi without trouble and climbing, it's currently sat at 10psi and it's great for a daily.

The T2 I used on my 998 would make the boost, but IATs were getting high above 12.

the comp maps for the gt15 abd the T2 are identical.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Thanks guys, I'll have a look it to those suggestions.
This is getting complicated!

I'm starting to think 10psi is too low to make proper use of the turbo...

o a 998 you'll make about 10bhp per psi as a rough guide.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Shauna's is around the mid 80s in horsepower at 10psi with no intercooler, but makes 117ftlb of torque, so the hp figure really doesn't matter to us!

10psi is more than enough for a fun reliable daily! I found there's a massive difference just turning it up two psi. We need to stick mine back on the rolling road really, the head gasket was on the way out rhe the last time haha. But as Carl said, the figures don't matter to us because it is a nice daily driver! What sort of power are you hoping for out of it?

They don't die, they just get faster!

I think I'm going to go with the RHF3, just cause its something a bit difrent to what's usually used by guys on here and they look good for up to 100bhp

With regards to bhp.. I want reliability over max torque but Iv got a feeling this might just be the beginning of my adventure!

boost is a drug...

I'm sorry guys, I'm new to this. I'm starting to think about turbocharging my stock 998cc and I have been reading in other threads on TM that the GT1752 is one of the best choices for low end boost applications, however I am now reading in this thread about the GT1548, T2 and GT1544. What is the difference please ?

1752 is great on a 1275, but a bit big f0r a 998, go with the 1544 or similar.

On what where the 1544 fitted originally ?