Grande Punto Abarth - Full engine preparation

[hammersword]

Hello Mr Croft,

I am building the engine of my Grande Punto Abarth and I have some question for you to help me figure out.

The engine is the classic 1.4 F.I.R.E but the T-Jet one!

So we have done
Full cylinder head preparation on Sevdalis flowbench
CPS pistons
rods with ARP bolts
the stock head bolts are 8.5mm and we add 12.5mm ARP
C&B Road Max cam 272deg 8.7mm lift
we plan to add a Garrett turbo, or GT2860R or GT2860RS

Cause of the engine structure 72x84 it cannot rev too high. I think 7500 will be the limit and the target power is about 280 - 300hp

So, my question for you is about lightning crank and flywheel
stock cranks weight is 9800Kg
stock flywheels weight is 9200Kg and is double mass

You think that I must light them? Some one told me that I will loose high reving and top speed if I do it, but I will gain acceleration.
What is your opinion?

Best regards
Fotis Lekatsas

[Guy Croft]

Lighter is always better - provided you balance the rotating parts effectively. That said if you go extremely light (eg using a disc from an auto model with virtually no mass at all) the engine won't run in a stable manner at normal low speed.You need a bit of inertia to keep the thing turning over between firing strokes. I think Denise Burchette* (USA member) tried that and I'd be interested to hear from her on that again here.

F1 engines, with lots of cylinders - will run with no FW at all albeit that there is a measureable mass in the clutch pack(assuming they still use them, they did when I worked in F1 in the late 90s).

There is no gain whatever (NONE!) to running heavy rotating parts, unless it's, say, a single cylinder diesel...

Hope that helps,

G

BTW DB - if you're reading this - just for the record, your air filters, yes, do make me wince!

[hammersword]

a little searching on companies that make FW for T-Jet engines told me that I have that choices:

as you remember stock fw is 9.2Kg

aluminum singe mass 6Kg, 7kg or 8Kg

Fiat weights their FIRE parts (crank FW) alone, so can I add a lighter FW aluminum and weighted alone on my engine without touching crank or
lightened and weighted alone and not together?

thank you
Fotis

[Guy Croft]

Sorry, I don't personally consider aluminium a safe material for a FW because of it's fatigue properties.

G

[hammersword]

now you made me a question of aluminum flywheels....

I have found one with 4.8Kg totally aluminum.....
you think that it will be tired fast?

can you suggest me anything?

we plan for 310 - 330hp not for everyday use, but the base point is an everyday car with 240hp and with one button of boost control will raise to 310+

thank you
Fotis

[Guy Croft]

http://www.sv.vt.edu/classes/MSE2094_No ... l#S_Ncurve

[pastaroni34]

Moment of inertia (MOI) is much more important than weight alone. MOI relates to how much energy it takes to spin the part on an axis, in other words, how much energy is not being used immediately to turn the wheels. The further away from the axis material is, the more energy it takes to spin it. You can have a very light flywheel but still have a high MOI because the bulk of the material is out by the ring gear.

Using a moderately high strength steel such as ANSI 4140 or EN40b you can make a steel flywheel with a MOI at or below that of an aluminum (6061) flywheel. Remember the aluminum part will require a steel friction surface and the bolts to hold it on. A large part of it's MOI is the ring gear, which you can't do much about unless you cut your own.

Personally I don't trust the way they've affixed the ring gear on the flexplates... I DID have a failure because of this. I subsequently made flywheels with a lower MOI than that of the flexplate solution. They seem to tick over just fine but you definitely have to give it some revs before you go anywhere. Of course it didn't help running a 5.5" clutch which is basically binary in use.

[Guy Croft]

Good post Jason!

G

[hammersword]

very nice posts.

I told that to my dealer and he told me that can support me with a steel flywheel....

Do you think is better steel than aluminum?

thank you Fotis