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 4age piston dome calculationsFirst  1 2 3 >  Last
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ga_goosh




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here are my final calculations:
Quote, originally posted by ga_goosh »
ok so here is a new chart with updated specs that i have found on the internet and other members here. I also updated all the 16v engines with 36cc chamber volume

Advertised compression ratios
BP=9.4:1 (euro)BP=10.1:1 SP=10.3:1 ST=10.5 BT=11.1:1

advertised head CC
16v=36cc 20v ST=34.5 20v BT= 37.8cc

Engine-----------OEM CR-----headCC--------Piston heigth-------------piston dome:
4agze (BP)---------8:1---------36cc---------------30mm----------------------- -11.9
4agze (SP)-------8.9:1--------36cc----------------30mm---------------------- -5.45
4age (BP)--------9.4:1--------36cc----------------30mm----------------------- -2.5
4age (euro)----10.1:1--------36cc----------------30mm----------------------- 1.15
4age (SP)-------10.3:1--------36cc---------------30mm----------------------- 2.1
4age (ST)-------10.5:1--------34.5cc ------------30.5mm--------------------- -1.1
4age (BT)-------11.1:1--------37.8cc ------------30.5mm--------------------- 4.7

looking at old post i found that the ST has .2" taller comp heigth. so the compression heigth is 30mm for the 16v and 30.5 for the 20v (this info from dr.occa from a previous post) the previous chamber heigth number 1.171"(29.7mm) is from ares and is actually what ares uses as there chamber heigth.

the BT comp heigth is at 1.202 (30.5mm) provided by gaijin_rokurunner...thanks gaijin

thanks sam_Q for posting your bt20v chamber volumes and oldskewltoy for the 16v chamber volumes

I think these are as acurate as i can get with out actually measuring the pistons. now you can figure out what compression you want and chose the oem part that gets you there. You can test dynamic compression with a more accurate numbers to choose the right cam for your setup


i have been searching for the piston specs for a 4age like the dome cc and the compression heigth. i am wanting to play around wth compression numbers but i dont have the specs of the pistons. if some one has these LMK thanks.

looking for
bluetop big port, redtop small port silvertop and blacktop

Modified by ga_goosh at 3:07 PM 7/17/2012



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oldeskewltoy




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please share what you learn.



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ga_goosh




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 Re: (oldeskewltoy) » Reply  Edit


ill try but im not really finding anything



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ga_goosh




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ok i have found what the dome higth is for the high comp 10.3:1

dome higth is 1.171" and with knowing that i have estimated the dome cc at 6cc with the stock head gasket. that is also assuming that the head chamber is at 39cc so there is a bit of a guess there

going to do more investigating

Modified by ga_goosh at 5:01 PM 7/16/2009



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oldeskewltoy




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 Re: (ga_goosh) » Reply  Edit


Quote, originally posted by ga_goosh »
assuming that the head chamber is at 39cc so there is a bit of a guess there

going to do more investigating

When I measured my chambers they were all between 36 and 36.5 cc



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 Re: (oldeskewltoy) » Reply  Edit


yea i saw that in your build thread. ok then i will redo my calcs

ok if that is the case with the combustion chamber at 36.25 (in the middle of your measurements) and 1.2mm head gasket the dome cc is estimated at 3.68cc

i am still looking for bluetop and 20v specs but no one has any measurements listed



Modified by ga_goosh at 9:15 PM 7/16/2009



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oldeskewltoy




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well... bluetop will be a negative #, ever so slightly dished

and 20V has 2 different pistons....





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 Re: (oldeskewltoy) » Reply  Edit


thanks for posting that pic. i did know that they are slightly different since the combustion chamber is different between the black and silver top heads. i dont know if the chamber volume is different or not tho



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ga_goosh




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ok looking at some measurements that was specified by the compression calc i am using the compression hight is from the center of the wrist pin to the top of the piston not including the dome. so in that case i am assuming that the distance for the redtop is the same for the bluetop piston

if that is true then the blue top with a cr of 9.4 will have a dome cc of -.9 with oem 1.2mm head gasket and chamber volume of 36.25cc

now i will attack the 20v



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pb92-07A




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 Re: (ga_goosh) » Reply  Edit


I've read in one of the sites i've searched for in google that the ST CC is 34.5 and BT 36.8... that means fitting the gze 8.9/8.0 pistons on an ST would yield in a slightly higher compression as opposed to that of a 16V head... anyway looking forward for more details regarding 20v piston cc.
oldeskewltoy




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 Re: (pb92-07A) » Reply  Edit


Quote, originally posted by pb92-07A »
I've read in one of the sites i've searched for in google that the ST CC is 34.5 and BT 36.8... that means fitting the gze 8.9/8.0 pistons on an ST would yield in a slightly higher compression as opposed to that of a 16V head... anyway looking forward for more details regarding 20v piston cc.

I can't speak to volume... but they do say a picture is worth a thousand words...

I'm afraid specifications aren't part of the thousands words....




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Quote, originally posted by pb92-07A »
I've read in one of the sites i've searched for in google that the ST CC is 34.5 and BT 36.8... that means fitting the gze 8.9/8.0 pistons on an ST would yield in a slightly higher compression as opposed to that of a 16V head... anyway looking forward for more details regarding 20v piston cc.

that i have found out too but like most things on the internet you never really know if it is true. according to arias the 16v combust chamb is 39cc. when oldeskewltoy ccd his heads his results yielded 36 to 36.5cc. i tend to believe him more than arias numbers. i have also read that 16v comb chamb are any where from 35 - 39cc

for the 20v ST i have no choice but to use the 34.5cc number since i cant find anything other then that. for the 20v BT i did find on another site (toymod) sam_q cced his BT head and got 37.8cc but then again it is unknown if the head was ever milled http://www.toymods.net/forums/...25429

if i cant find a piston height for a 20v then i will just use the number i got for the 16v since all 4age motors have the same block deck height. i will also post the gze numbers as well.

i wish i had a set of pistons i could physicaly measure for the most accurate specs but oh well

more to come



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ok i just cant find the info i need so i will assume that the piston compression height is the same on all 4ag motors (1.171"). i also used oldskewltoy's 16v measurement for all the 16v heads at 36.25cc

this is using a bore of 81mm deck height of 191mm stroke of 77mm and a head gasket of 1.2mm and a rod length of 122mm

motor---------oem CR---------head cc------------------------------------------dome cc

4agze (BP)--------8:1-------35-39cc-------------------------------------------- -10.39
4agze (SP)------8.9:1-------35-39cc-------------------------------------------- -3.87
4age (BP)-------9.4:1-------35-39cc--------------------------------------------- -.9
4age (euro)-----10:1--------35-39cc-------------------------------------------- 2.25
4age (SP)------10.3:1-------35-39cc-------------------------------------------- 3.65
4age (ST)------10.5:1-------34.5cc (according to arias)--------------------- 2.8
4age (BT)--------11:1--------37.8cc (measured by Sam_Q)----------------- 8.19

if any one wants to contribute a more accurate measurement or if i find something new then i can and will recalculate this info thanks

i have noticed that arias pistons adds .018" in piston height to the 20v pistons.


Modified by ga_goosh at 3:37 PM 7/22/2009



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oldeskewltoy




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hmmmm you forgot one......

10 to 1 bluetop piston

Piston on left is 9.4 to 1, slug on right is 10 to 1



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lol i did forget ok ill update the previous thread thanks



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oldeskewltoy




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stickied.......



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dr.occa




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awesome thread goosh



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ga_goosh




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thanks occa.

i am not sure but i need to know the 20v head gasket thickness. does any one know? are they the same thickness as the 16v. i thought that the 20v where thinner but im not sure.

thanks



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krushh
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Does anyone know how i can safely run 12:1

I have started a thread here http://forums.club4ag.com/zerothread?id=61110

hellbillylarry gave me some reasonable advice for a 12.25:1

1) BT pistons
2) .8mm HG

and this should carry me there can u say if this sounds true?

I am currently runnin ST with SC pistons


Do you have any advice to get me 12:1 or > ???

ga_goosh




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it is all about your cam. you can run 12:1 if you get a cam that drops your dynamic compression down to about 9:1. you can maybe go a little higher. that is how the blacktop has so much compression and still runs on pump gas. you might have a hard time finding a cam with that type of specs for a 16v so you might want to use a thicker head gasket and lower the compression a bit to match a specific cam. that way your engine parts are working together. you can get an aftermarket ecu and tune it for e85if you are dead set on that CR.



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 Re: (ga_goosh) » Reply  Edit


I apologize for hijacking ur thread. The dynamic ratio tip was very helpful. I think I will do other mods before I consider this one.
Sam_Q
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yes 37.8cc for my blacktop head, and I have had a good look now and have come to the conclusion that it hasn't been milled. Arias quote 35cc for a silvertop head.



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Quote, originally posted by Sam_Q »
yes 37.8cc for my blacktop head, and I have had a good look now and have come to the conclusion that it hasn't been milled. Arias quote 35cc for a silvertop head.

thanks Sam. your measurements where very helpfull in all of these calculations.



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Sam_Q
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sure thing, if you don't mind me asking what are you trying to achieve exactly?



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well i was actually going to build a motor out of a 20v bt with a 16v small port head. but i was trying to use the 20v bt pistons since i wanted more compression then the high comp pistons. then found out that i cant get a 16v cams that will work with the high compression of the pistons. i also wanted to help the 4ag comunity with my findings since this info is unknown to a LOT of people. if i do build this motor then i might use a thicker head gasket to lower the compression or i might use some st pistons or high comp pistons with a thinner head gasket.im not too sure any more since funds are getting pretty thin right now.



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Cali-Bolt-Tron
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 Re: (ga_goosh) » Reply  Edit


Just stumbled on to this thread. Ga_Goosh thanks for your findings. What did you end up doing with your build?
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unfortunately it has been put on hold since finances have been short lately. This was more for the reaearch part of it so i would know exactly what i wanted before i bought anything. I was also doing this to find a way to avoid buying a black top engine then having to turn around and buy silver top pistons. I wanted to use the bt pistons. but it is looking more like the small port pistons are going to be the best choice if i ever get this build going.



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Cali-Bolt-Tron
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 Re: (ga_goosh) » Reply  Edit


I totally know what you mean. I'm in the same boat as you. I've been piecing my stuff for awhile now. Everytime I make a purchase on parts for my car then something out of no where comes up that needs my attention financially (Birthdays, Weddings, Xmas, Vacation, Car Insurance, DMV Renewals and so on).

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 Re: (Cali-Bolt-Tron) » Reply  Edit


wow havnt been on the forums in ages. Ive built many 4ages. Countless. The one I personally had in my Ae86 & this is just the basic stuff:

Bluetop Head
HiComp block
HiComp pistons
Silvertop crank n rods.

Im actually toying around with some things again. Thats one of the reason I came on the forum right now. Im machining a couple sets of bluetop rods with HiComp pistons. Machining the rods to accept 20mm pins. If you ever get back to your build, lmk. Ive done many setups.

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 Re: (oldeskewltoy) » Reply  Edit


Ok I measured my unshaved/stock smallport head yesterday... my results are 38.3 +/- 0.1 on all cylinders. Measured these with spark plugs in place. Just wanted to add more data..
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