Factory 4agze + 20v pistons

[Butters]

Hi all.
Has anyone out there fitted silver top 20v pistons into a 4agze block with SC12 supercharger.

We're concerned the higher compression might make for some problems, so won't be using the 14psi o/drive pulley, opting instead for the factory item.
We run 100 octane fuel, standard computer.
We're hoping for a bit more 'pull' in the higher revs.

We're looking at doing this to our racecar, as a temporary option while building the turbo motor up.


Many thanks!

[oldeskewltoy]

Hmmmmmmmm, so you are hoping to run 10.5 to 1 CR(silvertop CR, I believe....) and supercharge it...????

[Butters]

Yep, that's exactly right.

We have the gze (from an aw11) already, and have the pistons set aside from a 20v (which was purchased solely for the block, to build up a turbo motor).

We intend to repair the gze, using the higher comp pistons.

[RT40Corona4AGTE]

interesting.........hope it doesnt go BANG!

Good luck! Keep us posted!

[The Witzl]

hmmm... i would be more inclined to use the smallport 16V pistons, because they will still be non-interference fit, and properly suited to the 16V head.

THIS IS MY OPINION ONLY - I think the 20V pistons, being designed for the 20V head, will be more prone to detonation due to incorrect matching to the combustion chamber causing lack of control of the flame front.

The Witzl sez - bad idea.

[-GT-]

Yeah i'd agree you'd be playing with fire. The results would be interesting, but i doubt worth blowing your engine to bits. One tidbit of heresay though, *i think i remember someone claiming on the internet that* when using 8.9:1 gze pistons in a 20V the static comp ratio goes up to ~9.5; perhaps you could draw the conclusion that 20V pistons into 16v head would result in a lower comp than 10.5:1...? (Due to the comp raising inferring the 20V cc is smaller..?)

[oldeskewltoy]

Hmmmmmmmmmmm... there IS a guy in the Uk........ running a complete silvertop and a new Rotrex superchanger that is planting about 260 hp at the wheels.......

Here are the threads.......
http://forums.club4ag.com/zerothread?id=8112
http://forums.club4ag.com/zerothread?id=6543
http://forums.club4ag.com/zerothread?id=15084

[-GT-]

On what fuel and boost? Water/methanol injection?

[The Witzl]

yeah - silvertop pistons with a silvertop head wouldnt be quite so bad i rekon... but 20V pistons matched with a 16V head just doesnt seem like a good idea.

If it works.. then thats good
But i would be prepared for failure

[feral4mr2]

makes me laugh how people automatically think high c/r and boost means BANG!!!

tune it correctly with a good i/c etc. and it would be as relieble as a lower c/r boosted engine.

dont tune a low c/r boosted engine correctly etc. and it'll blow nearly as quick as people think a high c/r boosted engine will.

this IMO.

[The Witzl]

Feral - i totally agree with you on the high comp turbo engines.... but the point im making here is that he wants to use 20V pistons with a 16V head.

If you want high comp 16V - just use smallport 16V pistons. Thats what i did.

[-GT-]

That's not what we're thinking. I definately agree with you a high comp boosted engine is reliable if tuned and intercooled well, but that's not what we're talking about here.

...silver top 20v pistons into a 4agze block with SC12 supercharger...standard computer...racecar...

and Karl stated his concern was with (it's his opinion only )

the 20V pistons,... {ed: in the 16v head}, ...will be more prone to detonation due to incorrect matching to the combustion chamber causing lack of control of the flame front.

Hell, i even hinted it might not be so bad because the comp might be a decent wack lower than 10.5:1...

Edit: And there are guys running around feeding 6-7psi down the neck of internally stock 20V's too, the difference is, like you say, down to the tuning and intercooling. I would consider an aftermarket ecu a must. In this case though he's talking about taking a completely bog stock gze, slapping 20V pistons in it, keeping factory gze ecu (and i'd assume intercooling??) and everything else standard, then flogging round a race circuit to see how long it lasts.

[feral4mr2]

yes i agree with karl on the piston/head suiting for sure.


was getting carried away from many simular threads/topics on other forums etc. were as soon as someone mentions high c/r and boost people all say it'll blow up etc. straight up. haha.. sorry, bed time for me anyways!!

[Butters]

Hi all.

For anyone interested, we've gone ahead with the piston upgrade and have had the car on the dyno (see below).

The figures aren't too impressive, but the only difference to the engine (aw11 4agze) has been a pod filter, trd headgasket and the 20v pistons.

We're now making around 180hp at the flywheel.

Once the turbo motor is nearing completion we'll chuck the 14psi wheel back on and see what happens.

Was a fun little experiment. Cheers for the advice




The bottom aux lines are boost (bottom line) and fuel curve

[Butters]

In addition, we're apparently getting some detonation under 2500rpm.