4afe highcompression

[954afe]

what pistons should i use for this?

[Flashmn]

Wiseco, Arias, etc

[954afe]

what about 4age 16V pistons?

[94_Rolla_Guy]

plane the head or pistons I can tell you the 7A pistons have a 12cc dish and the 4A pistons have a 8cc dish

I was going to use 4A pistons in a 7A bottom end... that was gonna give me about 10.5:1 but moneys too tight and i need a reliable trouble free new engine so i had to go 100% oem

[retiredat44]

Originally Posted by 94_Rolla_Guy

plane the head or pistons I can tell you the 7A pistons have a 12cc dish and the 4A pistons have a 8cc dish

I was going to use 4A pistons in a 7A bottom end... that was gonna give me about 10.5:1 but moneys too tight and i need a reliable trouble free new engine so i had to go 100% oem

you would need a minimum of 98 % octane to keep from ruining an engine at 11:1 compression.

you would end up spending a fortune of gas. Probably eat up starters al the time too.

hard on the clutch, from dead starts...



plus, if you loaded old engine bearings it would be hard on those, it would be best to increase compression on new bearings..

[94_Rolla_Guy]

retiredat44: yeah these are the reasons i didn't do it the engine shop told me the 10.5 : 1 would run fine on 91 octane, but others told me theres no way, you need 98, 100....

but yes it would cost me a fortune on gas right now 91 octane is $1.25 a litre and is rumoured to go as high as $1.40 a litre this summer so .....

Also no way id bump the compression on old bearings it would be full rebuild time ....

[turbo4ag]

The 4AFE has an 18mm pin diameter. The only other OEM pistons that work are 5AFE (which should be the same) or early bluetop (84-88) 4AGE pistons which are 9.4:1. Im almost sure 4AFE pistons are 9.3:1 already. And the valve angle on 4AGE heads and 4AFE heads are different.

You'd need to go custom pistons or shave the head,

[Tommy]

Originally Posted by 94_Rolla_Guy

retiredat44: yeah these are the reasons i didn't do it the engine shop told me the 10.5 : 1 would run fine on 91 octane, but others told me theres no way, you need 98, 100....

but yes it would cost me a fortune on gas right now 91 octane is $1.25 a litre and is rumoured to go as high as $1.40 a litre this summer so .....

Also no way id bump the compression on old bearings it would be full rebuild time ....

haha, that shop lied to you. My GTI has stock compression of 10.5-1 and it runs great on plane jane 87.

and to the OP, whats the plan with a high compression 4AFE? whats there to gain with it - vs - swapping in a complete 4AGE? higher compression without the higher flowing head isnt going to gain you anything but a headache.

[aaron7]

Originally Posted by retiredat44

you would need a minimum of 98 % octane to keep from ruining an engine at 11:1 compression.

The silvertop 4age is 11:1 factory, I run 87 all the time with no issues.

[toyotaspeed90]

silvertop is 10.5:1.... if you're not knocking then your tuning isn't correct.... i can't run anything lower than mid-grade in my ae92 with a smallport w/o pinging......

blacktops are 11.0:1

[aaron7]

Ahh ok. I don't knock no, but I do run premium when I can (most the time!)

[retiredat44]

Originally Posted by Tommy

haha, that shop lied to you. My GTI has stock compression of 10.5-1 and it runs great on plane jane 87.

and to the OP, whats the plan with a high compression 4AFE? whats there to gain with it - vs - swapping in a complete 4AGE? higher compression without the higher flowing head isnt going to gain you anything but a headache.

My 89 Corolla run terrible on 87 octane. It's just too low, but we use it because gas is about $3.50 a gallon here. So for somone to tell me they can run 87 on any higher compression is full of BS. I grew up when most car had 10:1 from the factory. We had the choice of 100/98/96 octane - or super/ethyl/regular. Super was 18 cents a gallon

[aaron7]

If your car runs terrible on 87, then it's time to bring it to the repair shop.

[retiredat44]

Originally Posted by aaron7

If your car runs terrible on 87, then it's time to bring it to the repair shop.

I dont mean horrible, terrbile, I mean it's not nearly as good as running higher octane, even 89 shows a difference.. you took it wrong..


you must not understand how low octane fuel can cause kncking, and run-on pinging and deiseling, which happnes once in a while with the cheap gas. Not each tank of gas is the same, sometimes, one can get low octane gas that runs crappy,,,, and that is horrible...

if you move up to 89 octane it runs much better... but the price goes up.. especially here in San Diego County, where they rip us off with the highest gas prices in the USA. Dirty Bastards.

[TheOtherCarolla]

You can can always retard the timing, run it on 91 octance, and then when you want to race, bump up the timing and run some additive.