EJ22 Turbo pistons - Page 9

cdigerlando · #**121** 12-19-2005, 08:09 PM

From my Chilton

Turbo Piston and Ring Specificatons the only differences are

ring gap

Top compression 3.3L (0.0079-0.0118) 2.2L (00079-0.0098)

Bottom compression same (0.0146-0.0205)

Oil Control 3.3L (0.0079-0.0236) 2.2L (0.0079-0.0276)

Ring side clearance

Top compression 3.3L (0.0016-0.0035) 2.2L (0.0016-0.0031)

Bottom compression same (0.0012-0.0028)

Oil Control same (0)

I don't know if this helps much other than knowing that the SVX rings seem to have generally less tolerance. Probably should use SVX rings on 2.2T pistons, if possible.

cdigerlando · #**122** 12-19-2005, 08:16 PM

Quote:

Originally Posted by longassname

It's not the depth of the cutout they were talking about although the svx valve reliefs are quite deep. They were talking about the diameter of the cut outs. Now that you mention it the cut outs on the 2.2 pistons may not be deep enough either. You could use them though......so long as you don't break your timing belt. It wouldn't be the first high performance engine build to give up zero interference.

My concern would be the shape of the squish area. The squish area with the 2.2 na piston wouldn't be as good as the factory svx piston. 2.2 na pistons would both increase the height of the squish area from .036 to .054 and eliminate a good part of the squish area behind the valves which isn't matched on the pistons. The degredation of the squish area might cause more tendancy to detonate than the decrease in compression ratio would get rid of.

I would agree that the NAs would be difficult to work with. When you said 8.3:1 were you refering to NAs or Turbos?

I think this discussion has really solidified the need for custom machined pistons for our applicatons!

LAN: What compression are you planning for your stage 3 kit? I was thinking 8.5:1 for my turbo. My wife has a turbo fxt with an automatic trans

It has an awesome streetable feel to it. These engines run about 8.4:1.

longassname · #**123** 12-19-2005, 08:32 PM

8.3 is what it would be with the na pistons. The turbo pistons would make it an unworkable 7.2.

I'm planning on having them made for 9:1. That decision hasn't been finalized yet. I'm having Gary at Gary's Automotive in CA design the pistons and will take his opinions seriously in making the final decisions. He does a lot of engine work for professional rally subys and is a JE wholesaler with a lot of experience designing suby pistons. I've had Phil send him a spare piston already and I'm mailing him the rubbing i made of the combustion chamber and specs I measured today. After he has them we rediscuss things and come to the final decisions and piston design. You may want to look at the thread I started with my specs on the EG33.
http://www.subaru-svx.net/forum/showthread.php?t=30361

Quote:

Originally Posted by cdigerlando

I would agree that the NAs would be difficult to work with. When you said 8.3:1 were you refering to NAs or Turbos?

I think this discussion has really solidified the need for custom machined pistons for our applicatons!

LAN: What compression are you planning for your stage 3 kit? I was thinking 8.5:1 for my turbo. My wife has a turbo fxt with an automatic trans

It has an awesome streetable feel to it. These engines run about 8.4:1.

longassname · #**124** 12-20-2005, 12:31 AM

by the way obI nice job estimating the volume of the svx piston. That was awfully acurate for only having an exposed piston to work with.

drivemusicnow · #**125** 12-20-2005, 10:19 AM

How much strength/temperature resistance would you lose if you took the stock SVX pistons and ground the raised area down a couple mms?

I'm just wondering if it would be possible to take a set of new stock SVX pistons, remove the "domed" area to get an overal piston volume from 4 to maybe 12 or even 15.

Is this possible? wouldn't the machine work be FAR cheaper than custom JE pistons? The added benefit would be lighter pistons.

TomsSVX · #**126** 12-20-2005, 11:24 AM

still, I don't think our pistons are forged... You would probobly want a very strong piston if you want to decrease compression, because that means you really are looking to make more power...

Tom

svxfiles · #**127** 12-20-2005, 12:13 PM

Our pistons are vacuum cast.
It's supposed to be the next best thing to forged pistons.

TomsSVX · #**128** 12-20-2005, 12:20 PM

Tom, Call me asap i lost ur number (new phone

)

Wouldn't the strenght of the piston be comprimised if you were to shave off the middle "lump"?

Tom

SilverSpear · #**129** 12-20-2005, 12:32 PM

Quote:

Originally Posted by TomsSVX

Wouldn't the strenght of the piston be comprimised if you were to shave off the middle "lump"?

Tom

Of course they will.

oab_au · #**130** 12-20-2005, 03:33 PM

The options that we have, as I see it.
As the Turbo pistons are not forged, and are pressure cast, the same as the eg33 pistons. We have a choice of useing the NA 2.2 pistons, that would have to have the valve cutouts machined to accomadate the bigger eg33 valves. The comp would be about 8.5:1.

The other option is to machine a bit of the lump, off the crown of the eg33 piston, to achive what ever comp you need. The lump looks like it is about 78mm X 25mm ( Tom can measure it for us

), If we machined 0.5mm/0.020" off it, the comp would be around 8.7:1. 1mm/0.040" off the top, would give a ratio of about 8:1. The lump looks like it is at least 1.25mm/0.060" high.

The piston could be machined in a lathe, or mill. The amount removed won't affect the strength of the piston as it does not contribute to the main structure.

This would be suitable for a higher boost engine that was not going to spend a lot of time on full boost, normal road work, with the occasional 1/4 run, would be OK. The advantage of forged pistons, is they are a bit stronger at high temps, that occure from sustained boost. The EJ2.2T pistons are pressure cast, and they seem to take all the turbo can deliver, without failure. The eg33 combustion chamber is not designed for forced induction, so it won't run the same pressures, but for boost pressures under 14psi, the modified pistons would be quite adequate.

This would be the easist and cheapist way to drop the ratio, as you can use your own pistons.

Harvey.

TomsSVX · #**131** 12-20-2005, 06:13 PM

79mm wide at it's widest
73.5mm at the two thinnest
28.2mm thickness

Hope this helps...

Tom

oab_au · #**132** 12-21-2005, 02:29 AM

Thanks Tom, thats fine.

If we avarage the length to 76.25, the area is 21.5*cm.
So if the following was machined off the top of the lump, it would give these comp ratios.

0.008"/0.2mm = 4.3cc = 9.48:1
0.015"/0.37mm = 7.95cc = 9:1
0.025"/0.6mm = 12,9cc = 8.4:1
0.032"/0.8mm = 17.2cc = 8:1

Harvey.

drivemusicnow · #**133** 12-23-2005, 11:40 AM

Just thought I'd let you all know that I'm talking to Mike Huml at Slowboy. He's contacting Wiseco about the possibility of creating pistons for the SVX. Since they already have the 2.2T pistons, I wouldn't think it would be too difficult to raise the compression, and make the valve reliefs larger, but we'll see.

Contact at wiseco is a guy by the name of Brian Nutter. I said we could have potentially 5 buyers for 6 pistons each.

Although, I was thinking... How sweet would it be to run like 30 lbs of boost on that 7.3:1 compression ratio

TomsSVX · #**134** 12-23-2005, 12:07 PM

Yeah you would only need like a 100 of nitrous to get out of 1st gear

Tom

SilverSpear · #**135** 12-24-2005, 08:37 AM

Quote:

Originally Posted by drivemusicnow

Just thought I'd let you all know that I'm talking to Mike Huml at Slowboy. He's contacting Wiseco about the possibility of creating pistons for the SVX. Since they already have the 2.2T pistons, I wouldn't think it would be too difficult to raise the compression, and make the valve reliefs larger, but we'll see.

Contact at wiseco is a guy by the name of Brian Nutter. I said we could have potentially 5 buyers for 6 pistons each.

Although, I was thinking... How sweet would it be to run like 30 lbs of boost on that 7.3:1 compression ratio

Keep us updated Greg