JGNERAEVO9

Working out my build compression with this setup

http://rbid.ru/cr/?action=CalculateC...35:0.125&print

Using the HD2 Stroker Pistons at 10:5:1 doesn't give you 10:5:1 compression on a 4G64 2.2L. The car will be dedicated E85. What needs to happen to bring the compression up? Deck the block and the head?

94AWDcoupe

iTrader: (125)

9.8 is very nice compression for e85. but if you must I would shave the piston tops to lower dish cc. then deck block to match lower height.

JGNERAEVO9

So what would be max boost on a 76mm turbo on 9:8:1 running E85? I don't want to have to run a crazy amount of boost to max the turbo out.

BogusSVO

iTrader: (1)

You can do what coupe says, and cut down the crown of the piston, then deck the block to the piston so you have a zero deck.

The draw back to that is, you move the top ring land closer to the top of the piston, and subject the ring to more heat.

The other is you change the center line of the cam to the center line of the crank

By the math you show, you are 9.813

To get to 10.5, you need to close the combustion chamber by appox 5cc

BTW did you factor the space above the top ring, between the block and piston? That adds about 1.5cc-2cc

I have a set of manley stroker pistons, 608005 C-4, they have a -12cc dish

The dish is .223 deep

I am going to assume the dish depth is similar in the Wiseco HD2 as it is in the Manley

.223 - 12 = .01858

To get a -7.5 cc dish, you need to mill away 5cc

.01858 x 5 = .0929

So now the pistons have been cut .093 to get the dish volume to -7.5cc so you can have 10.5:1cr

Now the block will have to be milled that much, if not a few more

Now the timing belt will seem to be too long

.0930 x 3.141 = .292113

Think the tenstioners have room to take up that much slack?

How stout will the block be after milling that much?

I think it would be a whole lot simpler to contact your supplier and just have a set of customs made with the -7.5 dish

Add maybe $100 to the piston price and about 3 weeks to get them.

sparky

iTrader: (1)

Also, shouldn't the overbore dimension be taken into account? Cylinder volume increases with overbore pistons. An overbore piston would increase CR, all else remaining equal, wouldn't it? Maybe I am not thinking straight though.

JGNERAEVO9

Yes sounds like the best way to go. How can I calculate maximum boost on a Precision Turbo 7675 on E85 for a given compression?

BogusSVO

iTrader: (1)

Sparky, No, most of the major aftermarket manufacturers will increase the dish volume as they increase the piston Diameter so the advertised CR will still be the same no mater the bore size.

JGNERAEVO9, That is something I do not know. What I do know is boost pressure is the measure of restriction.

There will be a number of variables that will have to be accounted for.

For example, Take an engine that makes turbo 300hp @20 psi of boost from a 40 lb/min turbo

Port the head, the only change

It now makes 300hp @ 15psi with the same turbo

Why the same HP with less boost, less restriction, and the engine can now flow air in a more efficient way.

I think the best way for you to go, is get the compressor map of your turbo, and find the sweet spot in it, and have the engine handle that.

sparky

iTrader: (1)

OK, thanks bogus. Is a 10.5:1 piston still a dished design? What CR does a flat-top piston

sparky

iTrader: (1)

OK, thanks bogus. Is a 10.5:1 piston still a dished design? What CR does a flat-top piston yield on a 4G63 then?

JGNERAEVO9

Sweet spot for the turbo is 55psi

94AWDcoupe

iTrader: (125)

I calculate with zero deck height compression will be 9.97 with 1.0mm head gasket. with factory .75mm gasket compression would be 10.20. shaving head .010in. would give 10.42.

the above calcs are with your 43.8cc chamber. dont know where you got that number? but factory size is 43cc. using 43cc the numbers go to 10.09, 10.31, and 10.55.

I dont add 1.5/2.0cc for area around top of ring land. that part of piston expands with heat. nearly touches cylinder wall under running conditions.

BogusSVO

iTrader: (1)

Sparky, there is more to piston design than if it is dish/flat/dome

A dish piston can make more compression than a flat top piston, depending on where wrist pin bore is. (compression height = the distance between the centerline of the wrist pin and top of the piston)

Yes the 10.5 CR pistons are a dish piston.

I have not seen a flat top 4g63 piston, but I have never looked for one.....

JGNERAEVO9... 55psi on what?

Remember the 55psi of boost pressure is the restriction.

Is that with a sheet metal intake and big valve fully ported head? Or stock head and intake?

sparky

iTrader: (1)

Given identical, stock wrist pin center lines and stroke, and deck height, etc.....keeping these and all other variables constant....I guess what I am asking is related to a stock motor with stock rods and crank and pistons with stock pin location if you had a stock piston and longblock but if only piston top were to be altered from the stock dish to a flat top design what would the static CR be.

Just curious. Not trying to derail the thread.

JGNERAEVO9

3 inch pipes, AMS F1 intake, 5" IC and Head Games head with 1mm oversize valves.

sparky

iTrader: (1)

ETS 5" intercooler?