Compression/De-Compression

[FTO King]

Ok well, i have recently got'n very bored at home and i have decided to turbo a N/A FTO with a very high compression ratio 10:1.

Now i need to lower that compressio ratio to around 8:1 t odo this project safely.

However htis has to bea cheap and cost effective project.

I only want to run around 5-7psi boost,

My plan is to install a decompression head gasket 2.2mm thick (stock is .8 mm thick) and also put in a spacer of 1.2mm thick.

Question is how much do you think this owuld lower the compression in the engine and do you think it owuld be safe to turbo it.

I already have most hte parts, which i aquired from wrecks of other cars, and also havea n emanage ulti, im hoping that all this work including the turboing will be done by me and my 3rd year apprentice mechanic who works for mitsubishi.

I want the only costs to be the towing of the car to the tuners and the tuning..tight yes im lebo lol

FTO King

[Godzilla]

Firstly we need to know your bore/stroke or engine capacity and amount of cylinders and most importantly your combustion chamber quench area.

You can calculate it when the heads off, turn the head upside down, smear a ring of grease around a combustion chamber, place a piece of glass or perspex over it with a hole in it and pour some light oil into it from a measure beaker marked in cubic centimeters.

The amount of fluid to go in is your combustion chambers cc (cubic centimeters)

Then take into account your gasket and spacers volume and add that to your cc.

Then take into account how far below the block deck your pistons are sitting and calculate that volume too.

So its combustion chamber volume + gasket volume + spacer volume + piston below deck volume.

Once you know this volume and you know your engine capacity (divided by the amount of cylinders you have to get the volume of just one cylinder) you can work out your static compression ratio.

Its the ratio of your one cylinders capacity in cc to your volumes of all the spaces above the piston.

[tagg]

well you could use De-Compression plates that go between the head and block or get some low compression pistons ??

Tagg

[hillbilly]

head gasket would be the cheapest way of lowering your compression, and thats where I would stop if the projects on a budget.

I'm running standard compression on my 20v 4AGE silver top with a T25 turbo and I'm expecting roughly the same reliabilty as I would be getting stock, as long as you don't ring your motor out to red line and beyond I don't see a problem with running standard compression at low boost, its only when you start pushing your car beyond its capacity and red line is when you get problems...

I would suspect your head gasket alone (not including spacer) would lower your compression to about 9:1 or lower.

I don't like the spacer idea, IMHO it lowers the initial strength of the crush area between head and block...

on a side note high compression turbo will spool up quicker and reach max boost faster, and as long as you have a good engine to begin with and look after your motor I see no point to lower the compression at all, unless you want to go further than a street car should go.


but this all really based on my opinion, so your best bet would be to look up your specific motor and this conversion, find the results and what can go wrong and see if you can eliminate these unwanted possibility's.

[Godzilla]

Yes going dished pistons is the safe way to go about it.

Now the fun part about spacers.

Are you fitting 2 headgaskets to sandwich the spacer?

Or is the spacer a copper one that you cover in copper spray?

Spacers and gaskets are not as reliable as dished pistons, if you use spacers watch for detonation that may cause leaks.

On another note, what are you going to do about the fuel system, add another injector to the manifold, or just go bigger all around?

Dont forget when adding spacers that your heads will sit higher, make sure your timing belts can fit back on.

When you get stuck, let me know i have someone who custom makes one off copper headgaskets to any thickness. The last job he did for me was for a V8, $250 per head.

[FTO King]

hmm i see i see, well my car has done 140,000 kms. However oil has beenchanged every 5000kms.Timing belt always done on time.

I guess i could jsut go decompression head gasket without the spacer...
This is the spacer i was goign to buy:


This is the decompression head gasket iwas going to buy:


ok, in terms of fuel management injectors in the FTO only run at 60% however regardless i am planning to add another injector on the intake piping not on the manifold.

To control all this ill be having an emanage ultimate.

Anyone know any good tuners? Especially ones that have dealt with MIVEC etc

Oh and you talk about dished pistons.. Can my current pistons be dished?I dont know of anyone that makes dished pistons for the 6A12 engine.

[Godzilla]

The 2.2mm decompression gasket sounds about right, it drops 1.5, so if your running 10:1 with it your down to 8.5:1, good enough for low boost applications.

When buying the gasket id get the ARP head stud kit to go with it, most performance engines ive built i use their stud kits for head, main caps and rod bolts.

You cannot beat good head clamping in boosted applications.

If your injectors are running at 60% you may not need the extra injector, turn up the duration first before adding larger or extra injectors to keep cost down.

A dyno will tell you how the fuel curve is, id say more fuel pressure will do the trick for the injectors. Go Bosch 040 (rated up to 500 hp or a little smaller) and a fuel pressure regulator to control it with stock injectors with the duration altered via emanage.

No do not fly cut dish the factory pistons, their most likely cast, not forged and you will weaken them, its best to fit forged dished ones that have a strong crown, built for turbo abuse.

What i meant by your cam belt was the higher the head sits the longer the belt, unless your adjuster has enough adjustment in it to compensate for the taller head/thicker head gasket combo.

Many people overlook this, sometimes its a unexpected surprise.

Edit; Dont worry about finding pistons, many are cross usable, a piston manufacturer may tell you a forged one they have for another make or model will fit. They know the gudgeon pin, skirt, deck, piston weight and ring land sizes

[FTO King]

The 2.2mm decompression gasket sounds about right, it drops 1.5, so if your running 10:1 with it your down to 8.5:1, good enough for low boost applications.

When buying the gasket id get the ARP head stud kit to go with it, most performance engines ive built i use their stud kits for head, main caps and rod bolts.

You cannot beat good head clamping in boosted applications.

If your injectors are running at 60% you may not need the extra injector, turn up the duration first before adding larger or extra injectors to keep cost down.

A dyno will tell you how the fuel curve is, id say more fuel pressure will do the trick for the injectors. Go Bosch 040 (rated up to 500 hp or a little smaller) and a fuel pressure regulator to control it with stock injectors with the duration altered via emanage.

No do not fly cut dish the factory pistons, their most likely cast, not forged and you will weaken them, its best to fit forged dished ones that have a strong crown, built for turbo abuse.

What i meant by your cam belt was the higher the head sits the longer the belt, unless your adjuster has enough adjustment in it to compensate for the taller head/thicker head gasket combo.

Many people overlook this, sometimes its a unexpected surprise.

Edit; dont worry about finding pistons, many are cross usable, a piston manufacturer may tell you a forged one they have for another make or model will fit.

would you go for the spacer as well godzilla?

i was thinking of just upgrading the injectors to 210cc.Instead of adding another one.

Ill pay you to help and teach me how to do my head gasket

Oh and i noticed you siad most performance engines youve built...do you havea garage or workshop mate?
would my V6 differ that much from the ford you did in the other thread?

Is it that hard?

[Godzilla]

would you go for the spacer as well godzilla?

Is it that hard?

If i was interested in running a little more boost or giving it a little, id get the thinner spacer and a thinner gasket, the thinner the gasket, the stronger as the steel spacer can take a lot more than the gasket can.
If you run the spacer, dont forget to spray Hylomar as recommended (yes you can buy it in spray cans its so much better in even finish), but only on the side that sits on the block.

For what your looking for id say just the thicker gasket is enough, unless your planning on cranking the boost up.

Is it that hard? Whats hard if yourve done it before? Its the first time that its hard.

After you learn.

What turbos are you planning?

Dont go too big, its better to have response than to go big and have heaps of power, lag and a blown engine.

Workshop? My garage....lots of engines built for performance work as a hobby for friends that are not in a hurry. Its more a case of they bother me till i do it. LOL But i have to say im starting to feel it, im not getting younger.

Im planning to start a RB30 with forged rods, CP pistons and my RB26 head later this year.

They call them torque monsters.

[FTO King]

If i was interested in running a little more boost or giving it a little, id get the thinner spacer and a thinner gasket, the thinner the gasket, the stronger as the steel spacer can take a lot more than the gasket can.
If you run the spacer, dont forget to spray Hylomar as recommended (yes you can buy it in spray cans its so much better in even finish), but only on the side that sits on the block.

Is it that hard? Whats hard if yourve done it before? Its the first time that its hard.

After you learn.

What turbos are you planning?

Dont go too big, its better to have response than to go big and have heaps of power, lag and a blown engine.

Oh well i jsut ofudn this page mate its the specs of the fto's engine: Mines the GPX



Oritey so what Thickness Head Gasket and what Thickness Spacer would you get Godzilla? Keep in mind the one in there atm is 0.8mm.

Well im after acceleration and low down torque dont care about up high, dont intend to go that fast anyway more like an evo,or a rally car something that spools nice and early, as i said dont want more than 5-7psi.

Im looking at buying a Gt-28 turbo

Now if i go aheadw ith this, first thing will be to do the head gasket and upgrade injectors to 210cc. Will the car run fine with 210cc injectors?(stock is 160-170cc i think) as in will the stock ecu cope with this change without the emanage installed yet?

Oh and Godzilla..Do you own a garage or shed mate or a private business?since you said in the many high performance negines you have built. Cus i would be the first one knoking at your door lol

im just so nervous to start pulling apart things
Thanks

FTO King

[Godzilla]

Id recommend Rajab.

Gt-28 sounds a little too big. Gt-25R? Probably come in quicker with more low down linear grunt.



Just calculate the thickness of the thicker head gasket (2.2mm) and work out a spacer + gasket that equals a little more than that to give you a little more than a 1.5 compression ratio drop.

Id just upgrade the fuel pump, install a pressure reg and emanage with the stock injectors for a start. If problems after turning up the fuel pressure then go bigger injector to keep costs down.

Edit; in the links you posted they mention that its best to use a multilayer steel which was standard by Mitsu on 1997 onwards and was 0.3mm thick. Combine this with the 2.00mm thick shim brings you to 2.3mm, a little thicker than the 2.2 thick decompression gasket.
Make sure you use the stud kit for clamping.

[best4less]

I love it when you guys talk shop, i need to go look up every 2nd word you guys say so i can understand what the hell you are on about

[Godzilla]

I love it when you guys talk shop, i need to go look up every 2nd word you guys say so i can understand what the hell you are on about

Now you know how i feel when i ask you an electronics question.

Its always, he said what????and then a lot of google so i dont look stupid. LOL

@ Fto king, what are your plans for oil drain back for the turbos?

You know the sumps gotta come off to weld a fitting dont you?

Its not as simple as it looks, engine out, piping, intercooler, exhausts etc etc.

Why dont you just get that Supra you always wanted?

My son pointed out one on line last night, the guy needs the money to go overseas, 100,000 Km, non turbo, RWC with a little rego left, $5000 and negotiable.

Just go down and do some Leb negotiations with your cousins mate.

Im sure the guy would just hand over the keys to get rid of you. LOL

Cheaper than devaluing your FTO.

[FTO King]

Id recommend Rajab.

Gt-28 sounds a little too big. Gt-25R? Probably come in quicker with more low down linear grunt.



Just calculate the thickness of the thicker head gasket (2.2mm) and work out a spacer + gasket that equals a little more than that to give you a little more than a 1.5 compression ratio drop.

Id just upgrade the fuel pump, install a pressure reg and emanage with the stock injectors for a start. If problems after turning up the fuel pressure then go bigger injector to keep costs down.

Edit; in the links you posted they mention that its best to use a multilayer steel which was standard by Mitsu on 1997 onwards and was 0.3mm thick. Combine this with the 2.00mm thick shim brings you to 2.3mm, a little thicker than the 2.2 thick decompression gasket.
Make sure you use the stud kit for clamping.

yeah i could go for the Gt-25R spools quicker and i need much hp..
Mine is a 95 so i dont think its the multilayer steel, so what i could do is go the 2mm shim and grab the .3mm MLS from mitsu even better its genuine...

Yep ill grab the ARP stud kit.

Here is my engine lol doesnt look to complicated Boy am i going to have fun lol, yo uthink i can do it jsut off axel stands with no hoist lol?

[Godzilla]

Call a priest first to bless the car. (Or whatever religious denomination you prefer.)

Good luck with the rear head mate.

Id be pulling the engine out and doing it all on an engine stand, nice and easy to work and you can take the sump off to weld a oil drain back fitting and mock up the turbo setup while its all on the stand.

Pm me when you need an engine stand, ive got a spare one here you can take for a couple of months if you pull the engine out and need it.

[FTO King]

Now you know how i feel when i ask you an electronics question.

Its always, he said what????and then a lot of google so i dont look stupid. LOL

@ Fto king, what are your plans for oil drain back for the turbos?

You know the sumps gotta come off to weld a fitting dont you?

Its not as simple as it looks, engine out, piping, intercooler, exhausts etc etc.

Why dont you just get that Supra you always wanted?

My son pointed out one on line last night, the guy needs the money to go overseas, 100,000 Km, non turbo, RWC with a little rego left, $5000 and negotiable.

Just go down and do some Leb negotiations with your cousins mate.

Im sure the guy would just hand over the keys to get rid of you. LOL

Cheaper than devaluing your FTO.

id sell my fto in a second to get a supraaa no matter what they are sitll my faviorite car was this 5k supra thrashed and ready to flal apart lol?if not il take it, however one thing about me hence the corse im doing is i love to build, break and repair things so doing this is like a project to me even though ill fuk up most of it ill havea lot of fun doing it along the way.

There is a mate of mine in queenslnad who turbod his non mivec fto and his was a manual with abs, and he has all his piping out of his car atm so i got him to blueprint all the piping and he is sending it down to me. I have a mate of mien that works for a steel engineering company so im going to get him to make the piping for me for next to nothing.

The turboing bit and ifitting eveyrthing will be not to bad for me iv seen it done first hand on an fto before, I have a welder at home so yep i know the sump needs to be removed and the return line from the turbo needs to be pretty much vertical to avoid oil starvation to my engine.

The only thing im worried about is doing this head gasket, with all the battery relocation to the boot alternator nything electrical im fine iwth just taking apart the motor im shitting myself. Also i cant afford to have the car off the road for more than a week due to work so if i want to tdo the head gasket i have to be able to do it in under 7 days, is this possible do you think?

Yep i think your right engine shoudl come out and work on it like that.

I take it i have to get the heads machined then..where do i get this done and is this an expensive and timely process?

Yep our preist has been ringing recently to bless the house ill get him to do the car to, hell probably charge double woops i meant accept a donation of double the original amount

[Godzilla]

http://www.carsales.com.au/used-cars/private/TOYOTA/SUPRA/details.aspx?R=6640256&keywords=manual&trecs=172&M odel=SUPRA&sort_type=2&__Ntx=mode%20matchallpartia l&State=All%20States&__Nne=20&__Dx=mode%20matchany &Make=TOYOTA&__D=manual&silo=1003&seot=0&__sid=11E 6455AB917&state_id=0&__N=4294962861%200%201216%208 34%20285%20257%204294962110&__Ns=pCar_Price_Decima l|0||pCar_PrivateSpecialFlag_Int32|1||pCar_ImageCo unt_Int32|1&__Ntk=CarAll&Cr=3&__Ntt=manual&distanc e=25

My son just told me it just got sold....no shit for $5K ....you gotta be quick.

The turbo oil drain back must be fitted to the right hand side of the sump as you look at the engine from its front. As the crank turns the drain should be on the side where the crank heads downwards when spinning. Otherwise if you get the side wrong you run the risk of driving oil spinning off the crank into the drain and restricting it.

You should get your heads skimmed, in other words get the least amount of metal removed to make sure their straight. A straight 6 is around $80 to $100, yours are cheaper each as their smaller.

Reflex engines in Cambelfield (very good for accuracy) or even closer to you are "the head job head shop", Newlands rd Coburg (cheaper and good enough but i wouldnt trust them with a race block or head) just after the drive-in on the first bend behind a car yard. I send all my machining between the 2 of them.

Same day service on machining, just check with them before you drop things off to make sure.

Dont plan on welding your pipes with your home arc welder mate. LOL

[hillbilly]

after looking at this a bit more in depth you would be much better off buying a car that already has what you want...

if your gonna go forward with it do it right!!! if you're going to get the head skimmed as GZ said, I would be getting the block done as well, as the head would most likely be machines to the block from factory so it you do the head and not the block you might be creating more problems.

put aside about $4k+ to get everything you want done, because thats about what I worked it out to be.

if/when you get it done go to Trent at Satus Tuning in Dandenong, he is the E-Manage GOD!!! their is not one person in this country that knows more about them, he used to be the only Australian Tech support for them.

as for Turbo I would be going the GT-25R, T28 are a little uncivilised on small capacity engines.

the thicker gasket would be enough to do the job, I would not use the spacer their a bad idea unless done right! (decked head, block, ARP everything ect ect)

if you have the dosh you would be better off buying the parts you need to mod, like the sump, see if you can find a second hand one for cheap, before you go pulling yours off to weld, this allows a bit of leeway as well (if you f**k up you still have another sump to use)

Head Fix in Boronia do good work cheap! they don't f**k around as long as you don't f**k them around

and my last bit of advise if you decide to go ahead with this, buy a $800 shitter to get you around, my Corolla is over 12 months and still not finished