Got a garrette gt1548 turbo, on which engine will it work the best, and which of these engines are the most reliable with a turbo conversion.
will I be able to run 0.8 bar boost with an intercooler on stock internals and 3mm copper head gasket?
here are some specs and compressor maps of turbo
http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT15/GT1548_466755_3.htm

and pic of my turbo


thanx.

0.8bar? On stock pistons? No way - they'll either need machining or bespoke ones made up.
The 1108 and 1242 are more or less equal in terms of reliability.

1242 has much less meat on the pistons so would be harder to drop the CR to run decent boost.
i spoke to VAD and they confirmed spacers on the head lead to shorter gasket life.
originally VAD skimmed the OE pistons so i would be looking ot turbo the 1108 with skimmed pistons or custom if budget permits

Thanx for replies.
Don't want to put spacer bet gasket, can get a 3mm copper gasket made, as standart gasket is 1.9 mm. thus this will drop the cr to roundabout 8 - 8.5:1.
what boost can I run on standart pistons?.
want to put mpi on the 1108 or 1242 with standalone management for fuel and ignition.

have you read the turbo FAQ?
has VAD details in there

M@nticore said:

Thanx for replies.
Don't want to put spacer bet gasket, can get a 3mm copper gasket made, as standart gasket is 1.9 mm. thus this will drop the cr to roundabout 8 - 8.5:1.
what boost can I run on standart pistons?.
want to put mpi on the 1108 or 1242 with standalone management for fuel and ignition.

Click to expand...

Mine is running something similar to this and no problems so far

Mine boosts to about 12psi at the moment but will be upping that very soon :devil:

All Im gonna say is learn to read the compressor map, understand it fully and you will know what engine it'll work on best.

Going off vAD, It should be ok on either though...although I personally dont like the way theyve done things, and as a result, there is part of me that questions their turbo choice.

I run on two stock (1.9mm) headgaskets plus hollowed head chamber (about 4-5cc taken off). Can anyone estimate my CR ?

Could try http://www.csgnetwork.com/compcalc.html

or if you feel like doing it US style http://www.smokemup.com/auto_math/compression_ratio.php

Thanks.

And what would the estimated head chamber and piston dome volume be, on a FIRE 8V engine?

Asteris said:

I run on two stock (1.9mm) headgaskets plus hollowed head chamber (about 4-5cc taken off). Can anyone estimate my CR ?

Click to expand...

To get a sensible answer you need to measure the combustion chambers.

However we know the bore is 70mm and the stroke is 72mm therefore the swept volume is 277.09cc

We know the compression ratio was quoted as 9.6:1 so that implies an original total combustion chamber size of 28.86cc including the original gasket.

If we assume the gasket in the orginal application has a hole diameter of 70mm and a thickness of 1.9mm, the volume of the hole is 7.31 cc

Minus the gasket therefore the combustion chamber is 21.55cc.

If that is increased by 5cc that makes 26.55cc, plus two gaskets @ 7.31 cc makes 41.17cc new total combustion chamber volume. The swept volume remains the same at 277.09 so to that implies you have a new compression ratio of 6.73:1

I've assume Pi to be 3.14159

Ok, after caclulations on the 1.1 engine and 9.6:1 CR, estimated that the head champer is 22cc and the piston is 2cc dished. Dropping a second head gasket there, it leaves a 8.1:1 CR, quite nice for a turbo setup.

Mine is a 1242, so (assuming that the head chamber volume is still the same), in order to achieve a 9.8:1 CR with the stock 1.5mm gasket, the piston has to be dished at about 6cc volume. Dropping a second gasket there delivers a 8.3:1 CR and hollowing about 4cc of the head chamber gives the final 7.9:1 CR. Just fine for my intented 10psi of safe overboost.

All calculated with the help of the first site that J333EVO listed. In proximity...

That can't be right, if the combustion chamber was 22cc, your 1.5 mm thick gasket is 5.9cc and the swept volume we know to be 310.62cc. If that is dished by 2cc the standard engine would have a compression ratio of 11.2:1, reality is only 9.8:1 so the combustion chamber must be larger.

If you deduce by calculation a 70.8mm Bore and 78.9mm stroke gives 310.62c. If you reckon piston is dished by 2cc that makes 312.62cc divided by 9.8 implies chamber of 31.9cc including the gasket.

1.5mm gasket thickness by 70.8mm bore is volume of 5.9cc

1.9mm gasket thickness gives 7.5cc

22cc is the head chamber without the gasket volume, as used at the first site J333EVO posted.

1242 has longer stroke than 1108, so bigger swept volume.

I (read Emma's dad) measured my compression ratio to be approx 8.1:1 as my pistons had about an extra 1.5mm off them than Emma's cars original VAD pistons did, which makes it much lower than the quoted 8.6:1 VAD quoted. I know that Emma's car with special machined deep dish Mahle pistons runs 8.5:1 all this was measured by her Dad using what looked like witch craft, but in reality was some equipment he has from building race engines that I do not know how to use..

I run safely 1bar of boost, or in other words 14.4PSi, no detonation, no lean fuel, absolutely on the button. If i get the waste gate to stop creeping and tailing off the boost I could get approx 135bhp as it makes 140lbs ft torque at 3200rpm when boost comes on before it tails off giving only 118bhp at 5600rpm, and as we know the 1108 unlike the 1242 will rev to 7200rpm happily and there is more power to come from it as it now has capabilities to do it as fueling is sorted.

As an example, an integrale EVO runs 8.5:1, Renault 5GTT 8:1, Uno turbo 7.9:1, more modern turbo cars normally run higher compression as it makes car run better off boost, VAG 1.8L 20V 180bhp turbo as found in Ibiza Cupra R, TT, Golf etc runs 9.5:1 but the 225bhp models run 8.5:1.

Aaron.

Asteris said:

22cc is the head chamber without the gasket volume, as used at the first site J333EVO posted.

Click to expand...

Not arguing, but the site Aaron posted comes up with 27.39 for the combustion chamber less gasket if you plug in the 1242 measurements. It has to, compression ratio is simply the volume of the cylinder with the piston at the bottom of its stroke divided into the combustion chamber volume .

1242 / 4 gives 310.5 for each cylinder

Fiat lists the compression ratio at 9.8:1

Therefore the combustion chamber MUST be around 31.68cc all in.

CR is initial volume/final volume = (piston volume+chamber volume)/chamber volume, so in 1242 the equation (310.5+chamber)/chamber=9.8, gives a result of chamber= 35.3cc

That is, including gasket and piston dished volume.

Asteris said:

CR is initial volume/final volume = (piston volume+chamber volume)/chamber volume, so in 1242 the equation (310.5+chamber)/chamber=9.8, gives a result of chamber= 35.3cc

Click to expand...

I divided swept volume by published compression ratio to give the volume of the chamber, but your example above also shows that 22cc for a 1242 combustion chamber can't be right.

I'm not convinced your example above is right, you take swept volume+chamber, but the air that was in the chamber doesn't get fully compressed, the combustion chamber always remains. Mathematically the variation won't be that big though either way.

Volume of the hole in the gasket is simply pi x radius squared x thichness of the gasket.

Ratio is a non unitary value, which results from dividing two quantities. In this case, compression ratio is the division of cylinder volume while piston at BDC by cylinder volume while piston at TDC.

The volume of the air inside the cylinder while piston is at the BDC, is not equal with the swept volume as you say, it's the bore x stroke volume, plus dished piston face area volume, plus gasket volume, plus head chamber volume. All this volume gets compressed till the piston reaches TDC, so the end volume is all of the above minus the bore x stroke volume (volume that the piston occupies).

Example: Piston is 100cc, head champer is 50cc. Starting volume is 100+50cc, end volume 50cc. CR is 100+50/50 = 3:1

Reverse example: An engine with 100cc piston and 3:1 CR, has (100+x)/x = 3, 100+x = 3x, 100 = 2x, x=50. Your theory of dividing swept volume (100cc) by CR (3:1), would give a chamber volume of 33.3cc, which is wrong, as (100cc+33.3cc)/33cc, gives a CR of 4:1