[Mk2] [Turbo] best compression/gasket size

[chrisf]

hi all,
after some advice from a respected member on here it got me thinking about compression etc-for when it comes to re fitting the head i guess i want to get the compression as useful as i can without being at a potentially dangerous level-under 1.5 bar of boost/running forged internals/ct26 hybrid etc....

i A) want to keep heat to a minimum, in the engine
B) am looking for reliable power
C) want to future proof the engine now, rather than pay more later

i went on http://www.csgnetwork.com/compcalc.html

and HOPEFULLY got all the details correct...wasnt sure about the combustion chamber stats at first....as the rev 2 runs at 8.8 standard larger forgies changed the compression to 8.2 (check the details below) using a 1mm cometic gasket

i wonder what you all think as far as this compression working for me when i raise boost to 1.5 bar?and whether there is any thing else i should take into account?

Cylinder Bore Size 86mm,
Piston Stroke Length 86mm,
Head Gasket Bore Diameter 87mm
Compressed Head Gasket Thickness 0.5334mm (approx)
combustion chamber volume 53cc
Piston Dome Volume In CCs Negative -13.00

chris

[RyanRs]

Tbh mate, you would be better spending that sort of cash on a slightly bigger turbo, such as a gt28 and keeping the stock block. You will make more power safer this way. The problem with a ct26 at 1.5 bar is the the intake temps will start to rise.

As for CR, 8.4:1 is a popular choice.

[chrisf]

hi ryan,
it was just when i read "the beast" thread by mark edwards who reached some ridiculous level of tune using a ct26 hybris that i decided to go down this route

for the next 4/5 monts at least i will have to run this turbo (skintness) and will just be looking to get the most out of it, i understand the turbo's are known to bottle neck with heat but 1.5 bar would not be the daily driving boost level and i wonder how a greddy emanage ultimate would control this set up?
chris

[Quigonjay]

good thread here for checking compression ratio

http://www.mr2oc.com/showthread.php?t=366753

but i doubt you would have enough fuel to run 1.5bar anyway

[chrisf]

hi mate,
i got sard injectors and a walbro fuel pump-i'm hoping that will help

[Quigonjay]

ah cool, you never mentioned that above
what pistons you got?

[chrisf]

got the wiseco 0.40 over pistons, 87mm....
so goin by that helpful link i would need to run apexi 1.8mm gasket to achieve 8.6.1 compression

do u all think that would be a good compression to run at 1.5 bar?
i have charge cooler,cooler plugs etc so hope that helps also

my bud bobhatton who has been fixing the head suggested the 1.8mm gasket,this seems good for decent compression eh

[chrisf]

hi,

as i mention the below link shows i can reach 8:6:1 compression by using apexi 1.8mm gasket............similar to normal compression


http://www.mr2oc.com/showthread.php?t=366753

i then i found this link,and stuck in 1.5 bar (21.75)psi along with the compression i mentioned above and the altitude of my area (1000 feet above sea level) the chart showed i will be running a boosted ratio of 19.64 : 1 at that level-man thats high

that sound right?

http://www.wallaceracing.com/boost-comp ... o-calc.php

chris

[Quigonjay]

no
i dont get that calculator but thats definately not the reading you want
EDIT: sure i have seen bob reccomend a lower compression of 8:1 for 1.5 bar

[RyanRs]

hi ryan,
it was just when i read "the beast" thread by mark edwards who reached some ridiculous level of tune using a ct26 hybris that i decided to go down this route

for the next 4/5 monts at least i will have to run this turbo (skintness) and will just be looking to get the most out of it, i understand the turbo's are known to bottle neck with heat but 1.5 bar would not be the daily driving boost level and i wonder how a greddy emanage ultimate would control this set up?
chris

Well weather its day to day or not really isnt an issue. Its weather its going to get risky in terms of causing det while you are running that pressure. When the intake temps rise, you will start losing power per psi and increase the chances of det.

A general guide would be... The larger the turbo, the safer the power produced, but the greater the lag. So therefore, it would be safer to get 500bhp from a GT4088r than it would a GT3071r, but the lag would be double.
An alternative would be to go BMIC or expensive CC setup. you could run 1.5 bar then as you will have good inter-cooling. Or you could use WI.
I dont know much about the Emanage ems, but from what i have heard, there is not anyone in the UK which has the software to map this ecu. Pfc / link would be the better choice.

Im running 8.4:1 and i will be running a GT3582r ,aiming at about 26 psi on v-power when mines completed.

[cantfindausername]

I've just done some calcs on mine, and although some of the things I couldn't get the info for its come out with a best guess of 8.5 which I'm pretty chuffed about.

The bits I'd like to know for certain are:
- The dish cc of CP pistons.
- Where the piston sits in relation to the deck on a stock block/build.
- Compressed thickness of a 1.4mm Cometic head gasket.
- Bore diameter of 1.4mm Cometic head gasket.

[chrisf]

RyanRs do u think high octane boost will aid the avoidance of det?
i do have a celica charge cooler but unsure how much that will help at those levels of tune...........

thor tune the greddy...........

finally,i really wasnt expecting these pistons to have such a dramatic effect on the compression-i had a feeling the compression would only have changed if the actual length of piston changed/not the bore etc

chris

[RyanRs]

RyanRs do u think high octane boost will aid the avoidance of det?
i do have a celica charge cooler but unsure how much that will help at those levels of tune...........

thor tune the greddy...........

finally,i really wasnt expecting these pistons to have such a dramatic effect on the compression-i had a feeling the compression would only have changed if the actual length of piston changed/not the bore etc

chris

Well when you are working out the CR, there are many things to take into consideration.. Ant mentioned a few above, in addition to this you will need to CC the combustion chambers of the head and account for any valve recesses in the piston crowns etc.

Higher octane fuel would help, but the cost and hassle of using a better grade than v-power ,for the sake of a ct26 setup, would just be pointless! This is why i also mentioned WI. water will cool the combustion chambers allowing to run more boost. you could also add meth to the WI kit to increase your octane. but personally i dont like the idea of WI as its dependable and if you run out without noticing, you could run into a crap load of problems!!

As for thor and there mapping magic.....hmm do a search on here

Whats your plans for the car? BHP, use, budget?

[chrisf]

lol yeah i rear on dale's experience with thor-not good,i just not sure if i wanna go to the expense of a full rev3 apexi conversion etc

my hopes are 350bhp and i intent on using the car as a daily driver so hope to have minimal spool up time etc

i wonder how long it would take to set up a water injection system,anyone?...

it may be the way forward for me at the moment and yeah i guess once i have an oil cooler and mapping in place i will look at the gt series turbo's-and the hope for 400bhp (no more)

chris