engine calculated
Turbo Mini Forums

so i took the time to calculate my engine. (060 overbore)
so here it is.

*omega die cast pistons 060 overbore (72.12mm) (making 1330cc) 6.5 cc dish (not ideal i gues by the ofsett dish but no 10 cc versions in that size)
* longmann cilinderhead worked to turbo spec 26 cc
*piston to deck 1.5 mm
*gasket 1mm (compressed)

rest of the engine will be more or less standard. (except nodiz ignition and straight cut dropgears and 4pin diff and bp270 cam)

making a cr of 8.77.
planning to find the correct pulley to get the compressor spinning fast enough to make 10 to 12 psi. ( although i have a shit time calculating pulley sizes

3.11 final drive..

any corrections or remarks?

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

I dont like to see pistons a long way from the deck, mine are 5 thou down.

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

its possible to machine the pistons, ad quite easy to do,

you will need to check the thickess of the crown and keep to aroud 5mm thick

I have taken pistons from 10cc to 17.5cc

just need to find a good machine shop in belgium then. (not many you can trust here or want to do an effort for just 4 pistons) you risk that they put them in a lost corner and loose them or let them machine by a new person to see what he can do.... but it would indeed be better to make a bigger dish. did not know those pistons could have so mush taken of. learning allot on this forum. (and to say that i am seen as a mechanic on the Belgian forum... am good with na engines and twin carb setups though but always hi compressed much easier to raise it than to lower it i see now) nice mini by the way

Edited by Rammie2000 on 21st Jan, 2013.

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

easy enough to get another couple of cc's in the head

so if i set the pistons fluch ( 0.15 mm down) i have the option to kep 6.5 cc diched piston but then i have to make the head go to 33cc (what seems big but should be possible i thinck) making 8.61 cr.
or second i have the pistons made to a 10 cc dish and give the head 30 cc making a cr of 8.53.. what is the better thing to do then?

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

so if i set the pistons fluch ( 0.15 mm down) i have the option to kep 6.5 cc diched piston but then i have to make the head go to 33cc (what seems big but should be possible i thinck) making 8.61 cr.
or second i have the pistons made to a 10 cc dish and give the head 30 cc making a cr of 8.53.. what is the better thing to do then?

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

28cc seems to be the normal maximum you can get easily whilst leaving the beak in the chamber.

looked in to pulley and i am not a math scientist but here it is.
pulley mpi is 107.9mm pulley eaton is 65.5 mm making a 1.647 ratio
so engine rpm at 6000 *1.647= 9882 rpm of the charger.
charger flowing 750cfm at 15000 rpm
15000/9882=1.518...
750cfm/1.518=494cfm at 9882 rpm.
but now... how do i put that in to psi of boost.? and how much cr is save to use on that boost?

pfff getting obsesed by pulley size and boost calculation and turbo's...( had a nice dream last night about turbo charging my cafe race bike... while i was back home and sleeping next to my wife again for the first time in 3 weeks.......... WHAT THE HELL IS WRONG WITH ME!!! :- )

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

Rammie,
Don't get hung up on the theoretics.
I was calculating something like that and found that there seems to be quite a difference between theory and practice.

For one, bends in tubing and intercooler will take some psi off..
(I recall someone on here saying rule of thumb is 1 psi per bend?)

Search nuukuus cabrio in here, there is some numbers in his thread.

Edit:
The above sounds like I have my engine running; it's not (even close).

Edited by Yo-Han on 19th Feb, 2013.

Dazed and Confused....

19 years ago I just whacked 6mm off the top of the pistons to lower the CR. Not ideal by any means, but certainly never caused any problems. hat was factory pistons with a huge top ring land area.

In an ideal world yes you will keep squish area to a minimum....but dont worry too much about it if you cant. It isnt worth going nuts over.

I'd sooner keep a nice kidney shape in the head if possible than turn it into a bath tub.

Edited by stevieturbo on 19th Feb, 2013.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

You guys probably right about those to much calculating from my behave but it is a expensive build so do not want to build something that gos bang ore something that lacks power. but going to look at nuukuus threat to get more inspiration.

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018