Pre-build discussion (7MGTE)

M

MRSUPRA

New Member
Apr 11, 2005
838
0
0
Maryland
"We micced up my JE's and found they were perfect, I guess it depends on the operator on the day."

Yeah, they told me all the big name pistons come form the same forging process and are all built very well, but there machinest has had more issues with J/E's compared to the Arias.
 
starscream5000

starscream5000

Senior VIP Member
Aug 23, 2006
6,359
0
36
Hot and Humid, KY
I don't know if this is true or not, but I remember reading in one post (could have been BS) that Ross pistons are a nice choice becuase they are more compatible with the oil squirters versus JE pistons which don't have some type of provision for them. Can anyone confirm that? I think that would also be something to look into when choosing your piston Doward ;).
 
D

Doward

Banned
Jan 11, 2006
4,245
0
36
Alachua, FL
The weight of the Ross pistons is a negative for me. I'm looking more into the Wisecos and Arias right now - MRSUPRA, any chance of having the piston weights of the Arias handy? :)
 
jdub

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
Arias pistons - 8.9:1 CR - 300 grams
Arias pistons - 9.0:1 CR - 312 grams

How you going to handle the increased CR for the Arias or Wiscos (9.1:1 CR)?
 
D

Doward

Banned
Jan 11, 2006
4,245
0
36
Alachua, FL
jdub said:
Arias pistons - 8.9:1 CR - 300 grams
Arias pistons - 9.0:1 CR - 312 grams

How you going to handle the increased CR for the Arias or Wiscos (9.1:1 CR)?
Click to expand...

By making sure my quench is nice and tight, and with some good tuning :) I'll also most likely polish the combustion chambers, which will give me a little more room in the head (nothing major, but the lack of rises in the chamber will help keep detonation at bay)

Besides, I'll only be running 16psi for now. I don't think I'll ever see the high side of 20psi on any motor I build (simply no need - instead of running 25psi, I'll enhance the flow through the system and make the same power, at less boost)

I'm really liking these Arias pistons - I'm trying to find a good pic of them, to see how long the skirts are.
 
jdub

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
Ok...just checking ;)
What thickness MHG you going to use? You might want to check with Cometic for a custom MHG...they produce the ones for Titan.

Also valve timing has a fair size impact on dynamic compression...this is where adjustable cam gears are actually useful.
Here's a dynamic compression calculator that takes in account valve timing and boost:
http://www.rbracing-rsr.com/comprAdvHD.htm
 
D

Doward

Banned
Jan 11, 2006
4,245
0
36
Alachua, FL
That... is awesome :) Thanks for the link - and anyone that sees this, please read what they have to say at that link - good information!

I'll be running a 1.37mm Cometic, 84mm bore, most likely. Depends on how much the block/head get cut - I may have to go to a 1.5mm Greddy.
 
jdub

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
Further explanation ;)
http://www.kennedysdynotune.com/Dynamic Compression Tech.htm

Here's a calculator for static CR:
http://www.rbracing-rsr.com/compstaticcalc.html


Dow - The 7M cylinder heads are designed with as much quench area as possible with the valves determining the size and shape. The combination of the relatively large quench area of the head and a circular piston dish creates a nearly circular quench ring around most of the chamber. The difference between the NA and turbo pistons illustrates this point. Since boost/valve timing will affect dynamic compression and you are going to use pistons that have a smaller dish area, you may want to consider increasing the quench area ~0.30mm to optimize turbulence/combustion at the boost levels/flow you are planning to use.

Here's a calculator for quench area:
http://www.rbracing-rsr.com/squishcalc1.html

IMO, one of the most important things to do when building a high performance motor (as you plan to do), is make sure there is minimum gap in the combustion chamber between the block deck, MHG, and head deck. You don't want carbon build-up here...it will create hot spots in the combustion chamber, partially negating the effect of the quench area. Like I said, Cometic can make an MHG exactly to your specs...bore size, thickness, etc. You can make the quench area exactly what you want with min gap.
 
D

Doward

Banned
Jan 11, 2006
4,245
0
36
Alachua, FL
I did not know that Cometic could make a MHG to my specs - I had actually thought of talking to SCE about an ICS Titan ;) We will see, as really - a head gasket is the easiest thing for me to switch out once the motor is back in the car :)

I'm mainly concerning myself with a stronger than stock bottom end.

Definitely good links for those that don't understand dynamic compression ratios - also more of why cams are important ;)
 
jdub

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
Figured you knew about all this Dow...the calculators are a handy thing to do the math ;)

I'd like to clarify one thing on quench...generally, a tight quench area is good, but only to the point where it does not impede the flame front across the combustion chamber. Increasing static compression will give you better lower end...at the same time you do not want detonation as a result. This is where the quench area comes in...it's like walking a tight rope. You're increasing static CR with either the Wisco or Arias pistons...when I said to increase the quench area slightly, it was relative to the static CR associated with these pistons. Your quench area will actually be smaller than stock if you use a slightly thicker MHG, considering the material removed from the block/head decks of course. As you said, the tune + valve timing will have a huge impact.

You're smart to focus on the bottom end...that's where the power goes ;)
I never have understood why guys skimp on this part...sounds like to me you're going to cover that base quite well. If the MHG you choose doesn't meet expectations...you're right...changing it out is easy compared to having to tear down the bottom end again!
 
turbogate

turbogate

Life is Boost
May 18, 2005
425
0
16
South, FL
Doward said:
Are there any other piston manufacturers I'm missing? Also, anyone have the weight of a stock rod, by itself?
Click to expand...
You might want to look into CP pistons. I walking talking to this guys in miami who has build countless ultra high 2jzs (1000+ hp) and he recommended the CPs (I hope to have him do my rebuilt this summer) He wasnt to found of the wisecos cast and Hypereutectic process saying that when they get really hot, they tend to fail. However I think he might be talking about extreme engines/tuning etc, he is used to 1000+ hp that he build for the NHRA Import competitions etc. I would think wisecos are good for 600+- applications, so are the arp2000s of the eagle rods. I dont have much info yet on CPs, but it might be worth looking into. The price is not too far from wisecos.

Also summit sells the ATI dampner model that we need for $399.00 if you cant find it cheaper.
http://store.summitracing.com/egnse...sults=false&Ntk=KeywordSearch&DDS=1&N=700+115
 
bwest

bwest

Drafting, not tailgating
May 18, 2005
502
0
0
HippieTown, CA
Doward said:
Are there any other piston manufacturers I'm missing?
Click to expand...

Yeah, check out Probe (you should know of them since you played in the domestic world). If I didn't already have a set of JE's, I would have tried a set of their pistons and some of their 9310 tool steel wrist pins. I had plans to use their stuff on a turbo 2300 motor years ago but never finished that project...

Here is the link.
http://probeindustries.com/Pistons/Pistons_SRS/Toyota/Toyota.htm
Last I recall, the prices were better than any other off the shelf forged, I just can't remember where I saw the listing at...
 
You must log in or register to reply here.
Top Bottom