boost and mpg (998s)
Turbo Mini Forums

im going to build a 998 turbo the aim is to not have to mess around with the internals of a standard 998 too much to retain its decent mpg but add the turbo for a bit more 'giggle'

however what am i likely to get from a standard 998 with a gt1548 (straight swap for a t2 right?)
at about 8-10 psi, from trawling the forum this should give about 80-90 bhp well set up? (could i break 100bhp with this setup?) however will tht magic 998 mpg suffer.
the engine in question is a 1990 spec 998 from a city e
im currently getting 25 mpg from a partial hillclimb 1310 engine (i wont explain the 'partial' bit ill only bore you) so if you reckon i can top that tht would be great.

Well set up up to 40mpg could be possible. Although boost is addictive so it would be easy to slip into the 20s.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

40 seems encouraging.. i am aware boost is very addictive but it is a town daily so boost wont have much of a choice but to take a back seat i just want the option there.

what about 100bhp? or would i have to delve into the 295 and more boost and more fuel for that?

The big problem as i see it is you have to lower compression to fit a turbo, so off boost torque suffers meaning to acheive the same go youll end up in boost, the more time you spend there the more time you'll spend there. Mpg will suffer, and you will turn the boost up.

I suggest you plan for the worst (15psi) and hope for the best (8psi).

When I ran 9.3:1 CR and 8psi with the MG cam, I easily got 40 to 45mpg.

My current engine running 8.7:1 CR and a 266 (with boost switchable from 5 to 12) I get around 35mpg.

You can see the differance that cam profile and CR make.

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

www.twin-turbo.co.uk

seems good wil_h out of interest what power were those two engines producing?
and was that fuel economy whilst trying for it or just driving about..
i know i wont get sod all under decent boost but decent mpg whilst just poodling around would be good.

First engine 90-100.

Second one up to 120.

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

www.twin-turbo.co.uk

sounds promising power figures look good and as you have already said good (or what i consider good) mpg ill get collecting for this i think..

Well 40 seems too optimistic.
I'm doing 31-33 with about 110hp but I drive a lot on motorway at 120-130km/h so RPM is around 4000, very bad for consumption.
Actually low compression (let's say above 7.5:1) is good for town consumption because there are less pumping losses at idle and low loads (that's probably why old US regulations were requiring 9:1 CR). Good sealing and good motor oil (for better sealing) will improve efficiency as well.
The main problem is a poor exhaust design on turbo Mini because of lack of space.

Edited by alpa on 6th Apr, 2012.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm