998 Ti - Stage 2 - Now the Build - Jan 2012
Turbo Mini Forums

The 998 Ti engine is working very well, but I made the mistake of fitting the circlips in the pistons so is limited to 6000rpm. It was built as an "fuel economy" engine after all.

The last rolling road gave 112hp and 105 lbft at 5700 on 12psi. I later found out that the soft rev limiter was set at 5700 so there is more hp to come. It will probably make near to 120hp at 6000rpm if it can maintain that torque level.

However, I think that the standard 12G295 head may start to become restrictive, plus the T2 will be in the zone of inefficiency.

On the road, I'm always hitting the rev limiter so I need to do something about it. There is also a couple of oil leaks that need major engine surgery to cure.

So the plan is to build a new engine with a rev limit of 7500rpm, plus an improved head/cam/turbo combination.

In theory, it should give around 150hp at 7500rpm from 12 psi if I can maintain the 105 lb ft. This will allow the continued use of the helical box and verto clutch, that so far coped OK with that level of torque.

So, the spec is

998 block bored +0.080" (1062cc)
Hypatech pistons
Lightened and shot peaned rods
Wedged, hardened and balanced crank
Secret Cam Version 2
Ported 12G295 head
GT1752
New stainless manifold
Std box/drops but 4 pin diff

This will be fitted with the Megasquirt and Siamese Code fuel injection from the existing setup. It will need modifying for staged injection as the total installed injection capacity is unlikley to idle well.

Edited by Paul S on 6th Jan, 2012.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

what's the secret cam?

what was the phase 1 secret cam at least ?

Rusty by nature

great idea ,should be interesting .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I want a secret cam!

In the 13's at last!.. Just

Just fit a phase 2 and don't tell anyone

If something is worth doing, it's worth doing half of.

Actually, no one knows what cam I use...

In the 13's at last!.. Just

Come on guys, that is not helping !

Paul want us to ask him over and over

And after 3 or 4 pages, he'll give us a teaser to start the begging for a few more days

That is TM standart practice !
Just follow the procedure , will you ?

So Paul, about that secret cam of yours ...
Is it ground to your specs ?

Rusty by nature

um...

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=383175

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Ha ha.

There are some numb nuts on here

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I look forward to the results, I too have an FI 998 in the planning, but my cam choice is no secret!

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

www.twin-turbo.co.uk

Doesn't yours have more ports though Wil?

If something is worth doing, it's worth doing half of.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

dragging this of topic slightly... this is worth a watch, mostly stuff from the yellow book, but theres some other interesting stuff too.

http://www.youtube.com/watch?v=8NXl6dJBWaM

On 21st Sep, 2010 robert said:
um...

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=383175

Rusty by nature

Great, that's my dream project (it's the third in the waiting line).

Why stop at 7500 ? Std rods stand 8000 rpm with no mods.
If you are going to such a serious project way why not to do a good modern design: small turbine, well sized compressor and external WG ? You'd get lots of torque from 2500rpm and the power you want.

I would do something about water pump like having a pulley sized for high rpm and an additional electric pump for idle (after a hard drive). Otherwise I'm afraid cooling won't have enough capacity or efficiency (too many air pockets at high RPM).

Why overbore ? More bore means heavier pistons thus less reliable. It's so easy to add 0.1bar to get the extra HP.

Idle: mine idles more or less well with modern 65lb 4 jet Siemens injectors, AFR 14:1. So you have margin.

What oil are you going to use ?

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

OK, but you cannot have your gateau and eat it.

The reason for extending the rev range is to suit my driving style. If I need to accelerate from 2500rpm, then I change down a gear, so I'm quite happy for boost to come in at 3-4000rpm.

Besides, I very much doubt that there is a turbo out there that will make boost on a 998 from 2500rpm all the way up to 7500rpm. It's just not possible.

I'm overboring because I can get +0.080" pistons from Minisport Aus a lot cheaper than I can get +0.020" in the UK. For some reason Minisport Aus only do the performance pistons for a 998 at +0.080" and above

Oil with be Miller CVT - why use anything else?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I agree with you turbo size thoughts. I thin kthe biggest problem with the Sprint's engine is too much overlap[ on the cam and the 2.9 diff. If I used the 3.1 diff and the MG cam I think it would be a nicer drive, not that it's a pain, but could be better in 4th at 50mph.

Be interesting to have 4 different 998 turbos on the same rollers next weekend.

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

www.twin-turbo.co.uk

I'm using a 2.9 diff and a cam similar to the MG Metro on the current engine.

I can't say that I've noticed a problem at 50mph in 4th, but I think that the long inlet tracts on my EFi manifold help a lot.

Next weekend will be interesting.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

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

On 25th Sep, 2010 Paul S said:
I'm overboring because I can get +0.080" pistons from Minisport Aus a lot cheaper than I can get +0.020" in the UK. For some reason Minisport Aus only do the performance pistons for a 998 at +0.080" and above

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Just finalised the cam details with Kent and placed the order. The final spec is:

998 block bored +0.020" (1015cc)
Hypatech pistons with buttons
Lightened and shot peaned rods
Wedged, hardened and balanced crank
Secret Cam Version 2
Ported 12G295 head with 33/29 valves, bronze guides
GT1752
New stainless manifold
Std box/drops but 4 pin diff
Lightened verto flywheel with the MED HD Verto clutch

It will have staged injection and coil near plug ignition.

Picking up the block and crank from MED next week. Everything else either ordered or in hand except for the diff. Need to make the exhaust manifold though.

Entirely funded by getting rid of stuff like K heads, superchargers etc :)

I'm seriously thinking of going side mounted turbo with this one. What do you reckon?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Side mounted would be interesting, might make access to the different head ports easier for the widebands etc

Rusty by nature

The coils were discusssed here:

http://www.turbominis.co.uk/forums/index.p...tid=277161&fr=0

They are sat on the shelf, so I might as well use them.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."