How much power from the stock pistons and rods

**AlfaJack** · 26-03-10, 10:28

Hi guys,

How far can you go with power from the original pistons and rods. I am considering upgrades this year and want to have a good safety zone. I would like to have somewhere between 300-330bhp.

Also, when upgrading the pistons and rods, what does an after market piston allow that the stock wont? Is it less weight or more strength?

Thanks.

**mindus** · 26-03-10, 17:35

OEM conrods - I know engines with standard conrods which have over 500 hp (with forged pistons), one of these was used in the competition. Can not provide the torque figure though.

Forged pistons/conrods are lighter and have more strength. There is however diferent treatment of the word "forged" on the net.
Type of metal matters in forging also. Some expand more than others, therefore you need to take that into consideration while boring the block/ordering the pistons/rings, and ultimately then driving the car.

**Varypodaros** · 26-03-10, 17:36

I think that it's a little bit risky to have 300 bhp with normal pistons. I think that a nice and safe horsepower to have is 260 bhp.
If you like to have 300bhp or more I think that it's better to use forged pistons. the normal rods are Ok even at 450 bhp or even more!!!
the forged pistons allow less weight and they are more resistant at the high temperatures...

I have to say that here in Greece is a Delta Integrale with normal pistons and 350 bhp but it has:

-stock cams

-stock head gasket and head.
-stock rods
-stock pistons

-holtzer type exhaust manifold with 42mm diameter and not 38mm
(http://www.hfintegrale.gr/smf/index.php?topic=20.0)

-metalic exhaust gasket

-Εxternal Waste gate Turbonetics Evolution.

-exhaust 84mm Down Pipe to the end with one cilenser

-stock Turbo Τ35 with 360 Thrust.

-Ιntercooler custom PMC 640χ340χ70.*

-Σωληνώσεις αέρα αλουμηνίου και κολάρα σιλικόνης.

-aluminium pulleys custom made.

- Samco pipes.

-oil radiator Setrab,

-custom made maps for the ecu

-stock fuel injectors 384cc.

-Walbro 255lt fuel pump.

-air filter BMC.

-blow off valve Greddy Type-R

321 hp and 42kg at 1,8 bar
352 hp and 44,7 kg at 1,9 bar
:icon_cool:

**Evodelta** · 26-03-10, 20:48

It is how you look after something which makes it last, if you want to go for high power on stock rods and pistons then do so carefully and in an intelligent manner - cool intake charge, proper map (ditch your chips) and cap the RPM.
Would I recommend it? No, but I have made it work, I did it 'cause I had nothing to lose and had other things to prove.

Cast alloy is lighter than forged. Traditionally cast pistons fit the bore better (less expansion to worry about) so can make more power, just more unreliably.

That isn't to say that forged pistons are heavier, quite the opposite. Because it is a much stronger material you can make a stronger piston using less of it.

**arjunior45** · 27-03-10, 15:24

The very first FIAT Uno Turbo had oem forget pistons. Those after the first generation had 'normal' one.

I would go for
- forget piston of a well known brand and balanced them at +-0,10 gramms {not the 5 gramms for the oem pistons}. It's a 'job' that noone but you can do that!!!
- balance the oem rods {with the 'new' pistons installed} and polished them like glass/mirror. But first check them if they are ok or if there are any signs of worn or distortion. Replace any faulty one.
and
- polish the oil drain channels.

It will be nice to polish and balance the crankshaft too.

**SteveNZ** · 29-03-10, 13:37

Power is not the issue, you could blow pistons at stock power. Tuning, and mainly RPM is the major consideration.

**SteveNZ** · 29-03-10, 13:40

Originally Posted by arjunior45

The very first FIAT Uno Turbo had oem forget pistons. Those after the first generation had 'normal' one.
.

What do you call "the very first Uno turbo"? Ive pulled many engines apart and never seen a forged piston.

**SteveNZ** · 29-03-10, 13:45

Originally Posted by Evodelta

OE cast pistons are lighter than forged and fit the bore better (less expansion to worry about) so will make more power, just more unreliably.

Are you sure that's not a typo? Forged pistons are generally designed to be lighter than OE. Your comment would suggest there is only a single option (that is heavier).

**arjunior45** · 29-03-10, 19:10

Originally Posted by SteveNZ

What do you call "the very first Uno turbo"? Ive pulled many engines apart and never seen a forged piston.

The first exemplars of the Uno Turbo that came to Greece had forget pistons. I know that because I saw them.

**Evodelta** · 30-03-10, 21:32

Originally Posted by SteveNZ

Are you sure that's not a typo? Forged pistons are generally designed to be lighter than OE. Your comment would suggest there is only a single option (that is heavier).

Duly edited (I think I must have posted that up while I was half asleep and would have been better using my time in bed)

**AlfaJack** · 30-03-10, 22:06

Thanks very much guys. Really appreciate the advice. Think I should put a good RPM cap on it then and keep things cool until the day comes to split engine and block for a rebuild - not cheap these forged pistons!

**Xti** · 31-03-10, 05:50

Hi, guys.
Could you please enlight me a bit about the rpm "cap"?
I'm not sure what that means, just think it should be about engine's safety limits...

Thanks a lot.

Cheers,
C.

**Evodelta** · 01-04-10, 19:49

Originally Posted by Xti

Hi, guys.
Could you please enlight me a bit about the rpm "cap"?
I'm not sure what that means, just think it should be about engine's safety limits...

Thanks a lot.

Cheers,
C.

I was just refering to not going over 6500rpm, I did it by just watching the rev counter, but I guess you could fit a rev limiter if you were worried about getting carried away.nn

Difficult with OE cams as it's all over by then anyhow.

**arjunior45** · 02-04-10, 07:11

a rev limiter is "fitted" inside the ecu {I.A.W.} and you can program just 4 hex values for the rev limits you want!!!

**Xti** · 02-04-10, 17:49

Thanks, guys.

**SteveNZ** · 03-04-10, 04:33

Cams don't matter as much as the turbo.

7200 is the limit CG put on the stock 2L engine to maintain reliability. I've stuck to that for a long time and never had a failure, even with a 20 year old engine.

**axaQ42** · 03-04-10, 12:18

With stock pistons and conrods you can see 300bhp with no problem BUT i would definitly fit a spesso head gasket,very good oil(motul v300) and wrap the manifold or ceramic coat it, so you keep the heat of it away from the head(camshaft).

The stock fuel injectors go to around 330 bhp thats the peak...tested with no problem whatsoever. But be sure you have a healthy oil pressure. We just recently find out that the stock oil gauge lies quite a bit. We measured it with a industrial mechanic gauge which is very precise.
The figures were like that(left side original one,right side industrial):
5bar -7bar
4bar -4bar
1bar -1,5bar

We checked this on two cars and both lied quite a lot.

Which mods do you have in mind?

**AlfaJack** · 03-04-10, 16:11

Cheers. I already have the group N spesso head gasket - it has been in it for 6 years and I hope it lasts a good while longer as it is not cheap. I also run Silkolene Pro-S 10/60.

I am planning a GT28RS or similar, tubular manifold, bigger injectors if need be, full metal IC (same size and shape as the original as I don't want to modify the piping too much), Walbro fuel pump and a proper mapping session on a rolling road. I would love to pull the engine out and do this as a long term project that is not too feasible.

**mindus** · 03-04-10, 18:47

And head bolts should be changed to 12 mm diameter if you will go for high boost. Group A spesso head gasket would be a better choise

**AlfaJack** · 03-04-10, 21:17

Originally Posted by mindus

And head bolts should be changed to 12 mm diameter if you will go for high boost. Group A spesso head gasket would be a better choise

Unfortunately the previous owner who fitted the gasket just before selling it to me can not remember if it was A or N. He said it definitely did not have separate fire rings so as far as I can tell that rules out the A.

http://www.nyssaracing.com/shop/spes...cing_05_01.pdf

Would of been good to know the thickness too. Well, if I don't run more than 1.2 bar then I should be ok....he hopes!

Do head bolts need replacing each time they are removed on the Lampredi engine? As I am not planning to split the head and block until a time that it is needed I will live with the OEM head bolts which I assume are 10mm.

Is drilling and tapping the block to 12mm something the home mechanic can do or is it best taken to the engineers? Have the tools but not the experience.

**SteveNZ** · 04-04-10, 01:30

12mm head bolts are a total overkill at this level. An engineer is required for the modifications.

**AlfaJack** · 04-04-10, 10:16

That's good to know. Cheers

**axaQ42** · 05-04-10, 12:33

If you gor for 300bhp you won't need those 12mm bolts and bigger injectors. If you go for the bigger injectors the fuel map will need to be fully adjusted(which is a lot of work

).

I can get you a complete map from my ex Q4 with the these mods:
-tubular manifold
-bigger IC
-siemens deka 630cc injectors
-walbro fuel pump
-ported head
-integrale manifold
-big integrale turbo(TB0385)

The car works just fine, the AFR is spot on it puts out around 330-350 bhp. With few minor adjustement it would work for your possibly future setup.