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

Not a great deal different from the last one, but puts the plenum as close to the scuttle as possible.



The simulation shows that the total runner length brings peak torque down to around 5000rpm.

Injectors are the pencil type. Starting with 600cc/min each, with an option to go to 800cc/min if we want to try for a headline output.

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 does the runner length come out at? looks like about 15" from the pic,

I take it thats tuning to the 1st wave.

It's about 400mm in total from bellmouth to valve.

The simulation sotware does not use standard harmonics, so it is not wave specific, but at a guess I would say that it is equivalent to the 1st wave. The software works simular to FEA, 2 degrees at a time.

It's the shortest runner length that will bring peak torque down to 5000rpm but still give the target hp at 7k.

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."

Good stuff,

I'm going to be redoing my intake at some point, this time round I'm going to use a set of bike TB's to make the whole thing easier and more compact, the idea is to have a sliding fit silicon hose over the manifold so I can adjust the runner lengths by about 5" and see what it does to power. It will mean having the fornt looking a bit like Hastons though!



I havent forgot about the TIP measuing BTW,

Great minds :)



When and if the opportunity arises.

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."

5000 rpm peak torque !!!??? Ho my !

Rusty by nature

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."

Are they ?

Just thinking about modern big turbo cars with peak power at 5500 (Megane RS for instance) but then they are low-ish on hp per litre compared to your target ...

Anyway, if the torque curve is flat enough, you'll probably get 80% of that torque from 3000 rpm and up ?

(And by the way, I do admire your fabrications, skills and knowledge)

Rusty by nature

I'm not expecting this engine to start boosting much before 4000rpm due to the Gt17, so torque curve will not be flat.

This is the simulation for the engine that I first posted nearly a year ago now. As it is based on a "calibrated" simulation with quantifiable changes, I have some confidence in the numbers.

Edited by Paul S on 13th 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."

You really ought to get the siamese kits together you mentioned a couple of years ago Paul.

I'd be interested and I know of someone else who probably would be.

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

Maybe, John, but I would want everything fully tested and verified first.

I might have some time in the summer to sort something out.

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."

Yeah I understand what you are saying.

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

Basic block prep now complete.

Piston buttons, cms and caps milled for earlier bearings, same as the budget build.



Now on to the RTS :)

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."

Earlier bearings being better ?

Rusty by nature

No, later bearings in VP2 being no longer available.

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."

As you are using the VP2 bearings in both builds are there any issues with using them with a non-nitrided crankshaft? Just wondering if they would have any effect on the life of the crank or am I talking rubbish again!

Did you make the buttons yourself or are you able to buy them - I'm thinking of ditching the circlips as well.

I'm not aware of any issues with VP2 bearings on a non-nitrided crank. I've certianly not had any problems on the 998Ti engine.

I made the buttons, tricky bit of machining to get them the right thickness.

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."

Your Exhaust manifold looks spot on. How do you go about designing one? The one in the Miglia looks top notch too.

Do the piston caps just reduce the weight by not having the circlips?

Matt W

Both the exhaust manifolds are detailed in this thread:

http://www.turbominis.co.uk/forums/index.p...tid=288004&fr=0

The piston buttons are used instead of circlips which have a tendency to jump out and damage the bore at high rpm.

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."

Have I got enough pistons?

Edited by Paul S on 26th 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."

So you've decided to build a twin engine? :)

http://www.jbperf.com/

So you're converting this to be a V8 ?

Rusty by nature

There's actually another 3 pistons at the back and one we did not know what to do with.

V12 anyone?

Just Sturgeo developing his snapping skills. I though that it made a good shot.

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."

Have you got some spare in case you melt them

Did you have to do any modifications to the gudgeon pins to use the buttons or is there enough depth there to have a reasonable depth to the button itself?

I have some early A+ 998 flat top pistons, so these should be similar (at gudgeon pin) to the ones you are using on the budget build.

Just wanted to check before I get some made up - don't fancy the pin sliding out!