Uno Turbo blocks and possible displacement increase

TDeReggi

TDeReggi

Daily Driver
All the stock Fiat Uno Turbo MKII and Punto GT (turbo, sub 1997) engine blocks have 1372cc, 80mm piston and 67.4 stroke. Why did Fiat engineers do that? Was it only for emmissions and gas milage, since targeting street cars? Any particular reason that the Uno MKII cant be bored to 86.4mm like standard X 1500 block, to increase displacement? Also, the later euro UNO MKII is a Gen3 block and technically could be upgraded to a longer 78mm stroke. Is there any reason the Turbo version block cant be upgraded to the longer stroke? Im asking, to better understand the limits of the X1/9 block, and how far it can be pushed, to plan a custom build. Was the additional cylinder wall thickness required for strength? Was it just that if someone wanted more power/compression, a better approach would be to just increase the Turbo's ratio/size? Maybe they felt it was better to acheive higher RPM (less strain/resistance on cylinders) with the shorter stroke, and leave torque up to the turbo? Or was it that the engine could only take so much compressed air before it exceeded its capabilty to handle, and the 1372 + turbo already got you to that threshhold? Whether that limit be from perspective of when detination would start occurring with pump gas, or just the limits before pistons, gaskets, and main caps couldnt hold up? Theoretically, I could see the benefit of starting out with more displacement and/or stroke, to increase the low end and mid range torque and relying on modest turbo boost for the high rpm end. My point being, If rebuilding a Uno turbo engine from scratch, and can hand pick the internals, why not maximize the internal upgrades while at it? A uno Turbo MKII has very little HP in its stock form, potentially less than a suped up 1800cc stroked 1600 block. Why not just start with a Uno Turbo block, and increase stroke or displacement, apposed to starting with a 1600 non-turbo block? (provided one could be found). My question is more about the strength of the block and internals. I have a bit of experience with gastrous (water/meth) injection cooling on my other Vette supercharged cars. I was thinking about using gastrous cooling with a Fiat Turbo build, to assist with the detonation prevention. The only downside would be the need to switch to a third party specialized fuel injection management system, that likely would be a large expense. And of course availabilty of the donor engine, which is not as easy to come by, as say a K20 swap.
 
Uno / Punto GT turbo blocks are smaller bore as the cylinders are not siamesed. i.e. they have a water passage that goes all around the cylinder bore on all four cylinders. The 86mm bore blocks of all types have siamesed cylinder bores 1/2 and 3/4 so there is no water passage between these cylinder bores. The "turbo" blocks also have the addition of piston underside oil sprayers from the main bearing feed.

Yes the 1372 cc 67.4 stroke engines can have displacement increased by stroking them, same principle as with an 86mm bore block as the 80.5 open deck engine is the same crankcase architecture, so will take the later 78mm plus stroke cranks to get 1580cc displacement with 80.5mm bore.

Why, probably for good reason.

SteveC
 
Displacement of Italian petro engines are most common under 1600cc for very real reasons, TAXES..
This is why there are 2.0L turbo Ferrari 308s and others that are designed-made for the Italian market only.

Who else in the world back in the mid 1960's designed (Lampredi) and produced in mass an engine design that can easily run to
well past 7,000 RPM direct as delivered each and every time it is run for many, many many hours? And Lampredi was not the only one.

Could the folks at Fiat and other Italian brands design-produce larger displacement petro engines for passenger cars, absolutely.
Italians already do produce much larger petro engines for other industries.

What this has done to Italian petro engines, they have become very high performance petro engines for their displacement.
The Italian answer to achieving power is applying design excellence, Detroit and similar answer to achieving more power,
make the petro engine BIGGER, not better design (generally, yes there are exceptions but they are not common).


Bernice
 
Ya wanna go fast... From 2009, that red x1/9 is Fiat Uno powered.. Note the other cars in this field.

The greatest difficulty with going fast is not power from the power train, it is much if not all about traction and control.
Regardless of how much power is available from the power train, unless that power can be controlled and put to the
ground under fine control of the driver any amount of power available is totally and utterly irrelevant.

Likely the most important aspect of making any car go fast is the driver.


Bernice
 
Yes it is a fantastic little engine, and very strong. I thought about increasing the displacement on my Mk1 but didn't due to high costs. I got 205whp/267wNm @1.6 bar from a Mk1 engine with stock internals. The engine is not worrying me much but I expect the stock transmission won't handle much more torque than that. I've heard the MK1 block is more rigid and will not crack as easily as the Mk2 1.4l block and thereby better to use for increasing the displacement. Using a non turbo 1500 or 1600 block is a bad idea due to the reasons Steve C mentioned. However, you can have much more power with standard block with upgraded rods and pistons, but 400hp is probably as far you can go without adding water/meth.
The video is in Italian but you'll understand the important parts.
 
Bjorn Nilson said:
I've heard the MK1 block is more rigid and will not crack as easily as the Mk2 1.4l block and thereby better to use for increasing the displacement.
Click to expand...

The Mk1 block is a "closed deck" 14 bolt, so pretty much identical in most dimensions to a 1500 X19 block. It's crank case dimensions internally will not allow for fitment of the longer than 68mm stroke crank.

The Mk2/ Punto GT block is "open deck" . It has a slightly dfferent crankcase configuration, and the oil feed gallery is "higher" in the block. This allows fitment of cranks with strokes up to 88mm I believe, though I have never done it myself.

The open deck block configuration is known to have more issues with cracking than the closed deck block configuration.

All Uno T and Punto GT cylinder heads tend to have issues around the areas of 2/3 cylinders, where the exhaust passages are "siamesed" in the head, and both exhaust valves of the adjacent cylinders are closest together. This is the area the cylinder heads crack and seats / guides have issues with holes in the head no longer being round, and the alloy goes soft when they get overheated a few times.

SteveC
 
Closed deck blocks are a LOT stronger with a LOT more rigidity than open deck blocks. They are more difficult and costly to produce. Fiat was one of the first to use thin wall cast iron techniques that produced lower weight blocks with MUCH higher strength. This came from their casting expertise that goes back a LOT more centuries than other nations that had to learn how to do this from the Italians.

Not a fan of open deck blocks. These are much easier and lower cost to produce and why they are the default block production method of today. They tend to have cylinder wobble and no where near as stable as a closed deck block. This is why there are after market cylinder aids for Honda and other blocks with an open deck. These folks force more power from these blocks than they were ever designed to produce which results in all sorts of problems like this. Another example of horrid open deck blocks is the Porsche M96, M97 (another example of design for cost reduction). These suffer from cylinder movement under loading causing the cylinder seals to fail where it meets the bottom of the casting. Open deck blocks are more prone to head gasket failure due to movement between the cylinders and cylinder head. Given the forces involved, the open deck structure will dance around under load, this is a given due to design.

It is so easy to say the Lampredi SOHC engine is weak and crappy, produced so little power, yet few realize the potential is has and the design-engineering excellent it has for a mass production engine. It is a race motor in every aspect that few ever realize, in the same way the x1/9 has an excellent chassis-suspension.


Bernice
 
One of many aftermarket cylinder support systems for open deck Honda blocks..

CNC Werx Cylinder Support System Honda B, K, D, F Series – High Performance Parts Suppliers, Dyno Tuning & ECU Calibration Mapping Service, Race Engine Builders

futuremotorsports.com futuremotorsports.com

If the Honda block was any good as delivered oem, none of this would be needed.
Honda motors produce lots of power due to cylinder head technology, does not mean the remainder
of the design was intended to be power uprated LOTs in the ways folks do to them.


Bernice
 
Example of a GOOD closed deck block, SAAB's B204/B234.
These are good to ~500Bhp / ~500lb/ft on stock oem internals as delivered running about 35+ psi boost.
Nothing fancy or ... just good design and engineering.

Not my pix, from the web.
Saab B204 block.jpg



Bernice
 
@Rupunzell Thanks for info. Seems to be the right thing to go for the Mk1 engine and you confirm what I heard. Do you know if the Abarth 1.4l 180hp 595 engines has the closed deck block as well? People are getting serious power from these here and they seem be very durable.
 
Perhaps this was already mentioned, but aside from open or closed decks and/or different stroke lengths, isn't there also a difference in the spacing of the cylinders with the UT Mk1 block? I believe there is a lot more separation between them than the 1500 and other SOHC blocks? That would also play into the strength of the block when it comes to higher boost applications. But it also could limit the bore size when the block was designed; a larger bore (i.e. bigger displacement engine) would not allow for as much distance between the cylinders without the entire engine dimensions being larger. So going back to the original question being asked, this might have been a factor in the lower displacement of the Mk1 UT? I'm asking because this is only a speculation.
 
Dr.Jeff said:
I believe there is a lot more separation between them than the 1500 and other SOHC blocks
Click to expand...

There is - however, this is due to the smaller bore of course. The crank is essentially the same between the 1500 and Mk1 Turbo (they are interchangeable - but I'm not 100% sure they function exactly the same way. They have a different part number, I know either the con or main bearings are different from the X/19.
 
myronx19 said:
There is - however, this is due to the smaller bore of course. The crank is essentially the same between the 1500 and Mk1 Turbo (they are interchangeable - but I'm not 100% sure they function exactly the same way. They have a different part number, I know either the con or main bearings are different from the X/19.
Click to expand...
Thanks, that supports my speculation possibly why the Mk1 UT is a smaller displacement, to allow for more material in between the cylinders (for greater strength under boost).

Did the UT have a different oil squirter arrangement? That might require a difference in the crank design, if the internal passages needed to be different. I have no idea.
 
Why?
Thinking about how much ya can over-bore the cylinders under the belief more displacement = more power?

Want more power out of a turbo motor, turn UP the boost. If traction is broken at the rear tires at any moment,
there is insufficient traction.

Tale to share, back in the Can-Am BIG power car days, these BIG displacement engines and Strong transaxles
had enough torque and traction to instantly snap a rear axle at launch. Drivers had to be careful not to try a "burn-out"
as that would very likely leave them at the star with a broken axle going no were fast.


Bernice

Simon Oaten said:
has anyone measured the wall thickness on a Uno T block ?
Click to expand...
 
Bernice has some good points. Increasing the displacement is probably not the best route to gain more power from the UT engine. This engine was equipped with a tiny turbo and could produce 140-150hp at the best. A quick and easy way to more power is a modern and bigger turbo. A modern turbo deliver so much more power without significant lag, and more torque than the transmission can handle.
So the Mk1 engine is stronger(?) than Mk2 and can handle more boost. But the Mk1 transmission is weaker than the Mk2 (C510 gearbox).
It seems like the transmission is the limit when tuning the UT Mk1 engine. To me the Mk1 engine and the C510 is the best combination.

@Dr.Jeff I found a diagram for the UT Mk1 lubrication system. As far as I know the piston cooling (14) does not exist on the1500 N/A engine.
1608382644855.png
 
Dr.Jeff said:
Thanks, that supports my speculation possibly why the Mk1 UT is a smaller displacement, to allow for more material in between the cylinders (for greater strength under boost).
Click to expand...

How do you figure that?

The bore size is the same between closed and open deck, the displacement increase from 1301 to 1372 was from a stroke change - 63.9 to 67.4.

The turbo blocks have more distance between cylinders due to their smaller bore size, the actual piston spacing and the rest of the engine architecture is identical to the similar production year NA engines.

The smaller bore SIZING with identical SPACING is to allow the bores to be NOT siamesed and have water flow all around the bore, unlike the NA 86mm blocks that have siamesed cylinders on 1/2 and 3/4. The turbocharged engine being subject to much higher heat stresses (as it is making more power) benefits (obviously - otherwise WHY would it be engineered IN) from the additional water flow and more even cylinder temps.

It's not like the turbo block began life as an 86 casting but only had the holes bored 80.5 and the wall thickness is 2.5mm thicker all around, ithere is no (significant) difference in weight between an Uno T 63.9 stroke Mk 1 block closed deck and an X19 1500 block.

The 1116 cc -80 x 55.5 - variant, it has non siamesed bores the same as the unoT block, that is how Mr Lampredi designed it in the first place, the 86mm bore engine was a "redesign" and the second version of the engine.

You could make a 1301 mk 1 Turbo engine into a 1372cc displacement, by fitting a 67.4 stroke crank and different compression height pistons.... exactly the same as making a 1600 from a 1500.

SteveC
 
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Another difference between small and large bore blocks is the UT/PGT blocks have an oil gallery running across the block between the middle bores to provide an oil feed to the turbo. This is not possible in the big bore blocks.
 
IMO, ignorance of the demands of an engine specifically designed to be turbocharged and the value of displacement.

Having been around Saab-Scania engines that are specifically designed to be turbocharged since their day one,
there are very specific needs an engine specifically designed to be turbocharged MUST have. Heat stress from turbocharging
puts a LOT of thermal (heat) stress on all parts of the engine. To deal with this demands best possible cooling. In the case of
the Fiat Uno turbo block, this means giving up the Siamesed cylinder that once increased strength and rigidity as a non-turbo engine
for smaller bores allowing much needed adding cooling around the cylinders. Oiling is the other critical aspect of a turbo engine.
Oil jets that spray oil direct to the pistons are common as this aids cooling of the pistons and oiling of the highly stressed parts.
Then crank, con rods, pistons and all else involved must support the increase TORQUE (not hp) of a turbocharged engine. The Uno Turbo engine has a proven record of strength and reliability in these areas... The folks at Fiat know precisely what they are doing, respect this and accept the design choices they have made.

Turbocharging is effectively a variable displacement engine. As "boost" or air-fuel mixture is forced into a given volume of the
cylinder, that fixed volume cylinder has a higher effective volume. Want more power, increase the boost. Keep in mind during the absurd Formula One Turbo era, they were achieving nee_2000+ Bhp and near equal torque with 1500cc displacement running 90+ psi. Fantasy to believe any of that power could be close to being useful without Aero converting that absurd amount of power into down force to PUSH the tires into the ground resulting in more grip. Anything less than this is gear head fantasy of what is needed to "go faster".

~Why hack up the Uno-Turbo block to gain a tiny increase in cylinder volume causing a great reduction in cylinder and block strength that was designed in, as produced?~

The most critical aspect of any turbocharged engine is engine management. This is what makes or bust any turbocharged engine, it is also why SO many early turbocharged engines were a total and utter failure.


Bernice
 
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