Fiat Tempra 16v Twin Cams - Rods/Pistons

[tempra16v]

Hi,

I have a Fiat Tempra 2.0 16v Twin Cams(same as Lancia Delta Integrale 16v).

My motor is new(bought from Fiat, now it´s with 5.000km) and all parts are standart.

I would like to know with i change the original rods/pistons:

Original Rod: 144mm
Original Piston: 84mm, compression height 40mm
Course: 90mm

Project: Forged TFC Eng Rods: 145mm
Forged Iapel Piston: 84mm, compression height 29,3mm(I don´t know if I´ll use I-Beam or H-Beam)

The new capacity will increase to something like 2090cc.

I would like to know if this setup can make i up the max rpm of the motor with more security.

Obs: sorry for the bad english.

[Guy Croft]

"Original Rod: 144mm
Original Piston: 84mm, compression height 40mm
Course: 90mm

Project: Forged TFC Eng Rods: 145mm
Forged Iapel Piston: 84mm, compression height 29,3mm(I don´t know if I´ll use I-Beam or H-Beam)

The new capacity will increase to something like 2090cc"

OK!
The OE rod centre-center length is 145mm not 144mm in the Integrale and every other 8V/16v 2 liter Fiat I know of. I assume yours is too.
To increase the cubic capacity you have to increase the stroke of the crank or the bore size and you would go to 86mm bore on the 2 liter, which you can do if you tolerate a bit of overlap of the strong OE head gasket over the bore and dont' run the piston crown too close to that bit.

GC

[tempra16v]

I will assume that it´s 145mm too.
My project doesn´t aim the increase of the cubic capacity, it will happen cause the parts (rod/piston) avaliable here will make it. Here is too hard to find some place to make rods/piston with special size.

I only want to decrease de r/l and try to get more security in higher rpms.

[Guy Croft]

OK, there is definitely no need to lengthen the rod just to get - as you say - more security at high rpm.

A good quality race rod (beware of low-cost counterfeit ones from China that look like US race rods) will easily take the stress on that motor even to 9500 and over - with forged pistons.

If you want real security you need to think about the oil system - most rods fail due to overheating/aerated oil or oil starvation. There is plenty of info on this site (in the GC Virtual Workshop and forum too) about crank mods, sump mods, accumulators, coolers, oil etc etc, use the search to start with.

GC

[tempra16v]

GC,

Thank you for helping me. As you can see I´m not a professional in this area.

I have read some text that say that a motor with a r/l(radius/lenght) bigger than 0,30 let the motor more rough to climb the rpm.

This motor have a r/l = 0,310
With different rods I can get a r/l = 0,292

I don´t really know if its true if it´s make difference and if it´s work in this motor cause this I insisting about this. Here in Brazil no one like to prepare this motor so I don´t wanna take any view here.

Do you know something about TFC Engineering rods? They say that it´s from France.

Thanks for your hint I´m reading all the posts in virtual workshop.

[Guy Croft]

I'd forget the ratios, they are many and varied, we talked about them on this site but only to get an idea of what various engines use.

The main thing about longer rods is that you reduce the advance ie: delay the ignition timing (start it later in the compression stroke) because the piston dwells at TDC longer. This is good because the combustoin pressure is built up later and not 'fighting' the piston on the 'up stroke'.

There are all sorts of effects associated with longer rod, weight, piston velocity and acceleration, but the principal thing to remember is that the longer rod can foul the crankcase. Most people who use longer rods just add on 'a bit' and hope it doesn't do that. I don't know ho much you can lengthen the rods in the TC (not yet anyhow) but often the problem is finding someone with a current forging that can cover the increased size. Because if the don't have a forging you'll have to have them made from billet which can cost a lot more.

My preference for rods is Cunningham in California although I know rods by respected firms like Arrows (UK), Carillo (now owned by CP Pistons in Calif), Pauter, Crower (USA) and others are perfectly good race rods. My preference of Cunningham (given that our UK £ is plunging against the US dollar and shoving up the imported price) is based on years of using their perfect product on the limit and the customer support/response they give me.

Apart from Arrows, I don't know any other European mfrs so would not want to comment on other makes escept to say you have to be careful in your choice and those respected names won't let you down. There is a lot of money changin hands on the internet with VERY cheap rods of Chinese origin and a long queue of very unprofessional people waiting to sell them to you. With rods 'provenance' (competition heritage & traceability) is everything.

GC

[tempra16v]

GC,

Thank you one more time.

I´ll give some info about my motor.

Compression ratio: 9,5:1
Rod: 145mm
Piston: 83,960-83,970 - compression height 40mm
Cilinder diameter: 84mm
Piston course: 90mm
CC: 1995cc
r/l = 45(half of piston course)/145(rod size) = 0,310


The kit avaliable here is:
Rod: 154mm
Piston: 83,960mm - 84,6mm(must see the availability. I prefer the standart size) - compression height 29,3 mm
Compression ratio: ??? (I don´t know how to calculate it)
Piston course: 90mm (I think that it doesn´t change)
CC: 2091cc
r/l = 45/154 = 0,292

With this I will have the head of the piston 1,7mm down the top of the block.

What should I see to know if I can use this size of rods?

Do u have and idea os prices to make this kit in Cunningham?

[Guy Croft]

CR - Have a look at:

http://guy-croft.com/viewtopic.php?f=3&t=129

You need to look at the space between the standard rods and the crankcase as they rotate with pistons fitted and make a judgement as to whether a longer rod will fit! Not easy.

The stroke will not change.

In view of your inexperience I think you are unwise to change the rod length! No idea what Cunningham would charge, sorry.

GC

[tempra16v]

I won't do it alone I will leave my car in a professional workshop to prepare it. But before I´m trying to collect the maximum info about this motor. Unfortunately here in Brazil there isn't anyone that knows even half than you about preparing this motor.

I won't do anything unadvised, I'm not rich and here our currency is devalued compared to dollar. I ca't buy parts without knowing if it will serve.

You talked about rods and pistons? Which firms have good products?