Wiseco Vs. J.E. Piston

[frenimy]

What are the main differences between these 2 pistons. I have heard people say that the J.E. is better but I see more people using the wiseco piston. I am ready to order my piston but need to know which to buy and need to know if the differences in the pistons make up for the vast difference in price. Also what gaskets sets are the ones to look for?

[ATVMX905]

They will both give you the same exact performance. Je is overpriced. I would go with wiseco, because that i swhat i always ran.

[frenimy]

Thanks ATVMX905 but I know there are a few small differences between them like one is lighter just can't remember which one. Are they both forged or is one cast?

[drew416ex]

They are both forged pistons. I have had both JE and Wiseco. The JE has a little closer tolerances than the wiseco but if you arent a big time racer or anything the wiseco is fine. It will last just as long. Stock gaskets are fine to use. If you want a little thinner base gasket to up the compression a few points, cometic and moose racing gaskets are thinner than stock.

[frenimy]

Thank Drew416ex that weas the exact info I was looking for I am going to order the wiseco set today.

I know Wiseco are much lighter than stock so you get a quicker rev than if it were heavier. Too bad they didnt have the weight compared to stock on them. I have experience with Wiseco and I am curious to try JE. I just like how JE has a 10.5:1 because its inbetween. For myself I refuse to go to or past 11:1

[drew416ex]

Originally posted by FoxHondaRider
I know Wiseco are much lighter than stock so you get a quicker rev than if it were heavier. Too bad they didnt have the weight compared to stock on them. I have experience with Wiseco and I am curious to try JE. I just like how JE has a 10.5:1 because its inbetween. For myself I refuse to go to or past 11:1

Why do you refuse to go to 11:1

Originally posted by drew416ex
Why do you refuse to go to 11:1

Because I ride a lot of trails in high heat all year round. 11:1 I have more of a chance for it to start pinging. Also for the gain you get going to 11:1 isnt worth the risk IMO. If I'm not mistaken higher compression puts more stress on your crank bearings and it causes more heat.

[zrpilot]

Originally posted by FoxHondaRider
Because I ride a lot of trails in high heat all year round. 11:1 I have more of a chance for it to start pinging. Also for the gain you get going to 11:1 isnt worth the risk IMO. If I'm not mistaken higher compression puts more stress on your crank bearings and it causes more heat.

There certainly is some truth is your statement. However even a 10.5:1 motor could ping, because remember there are many factors that contribute to detonation. Any time a 400EX owner is considering raising the compression, they must realize that THEIR motor may require race gas.

Heres 1 other thing if someone could clear up. The OEM piston is supposed to be 9:1 compression. Now a Wiseco piston that is 10:1 compression is said to be measured at 0 deck height so in reality its much lower than 10:1. Same goes with 11:1 Wiseco. Is the stock measure with 0 deck height too? or is that the real compression witht he OEM gaskets and all. Another to consider is... does JE measure with 0 deck height making the compression you thought you were getting much lower?

[drew416ex]

Originally posted by zrpilot
There certainly is some truth is your statement. However even a 10.5:1 motor could ping, because remember there are many factors that contribute to detonation. Any time a 400EX owner is considering raising the compression, they must realize that THEIR motor may require race gas.

X2. 10.5:1 Isnt a huge difference. I had mine wiht 11:1 running on 93 octane in close trails with no problems. I also had a stage 2 cam, so that lowered compression a little due to the longer duration.

[07trx400ex]

The number they advertise is the static compression ratio. (CR)

Dynamic compression ratio is affected mostly by the size of the cam and type of fuel used. (DCR)

The first thing to understand is that "compression ratio" (CR) as it is usually talked about is best termed "static compression ratio". This is a simple concept and represents the ratio of the swept volume of the cylinder (displacement) to the volume above the piston at top dead center (TDC). For example, if a hypothetical cylinder had a displacement of 450cc and a 50cc combustion chamber (plus volume over the piston crown to the head) the CR would be 500/50, or 10:1. If head size was decreased so that the volume above the piston crown was decreased to 40cc, the CR would now be 490/40, or 12.25:1. Conversely, if the chamber increased its size to 60cc, the CR would now be 510/60, or 8.5:1.


Hope this helps!!!

[07trx400ex]

To answer the question better, the CR would be as advertised, but what really counts is the DCR. This is really more dependent on cam specifications. I will explain.

First consider the Otto cycle and the compression cycles of a four stroke. Lets separate this into steps.

1) The power stoke is completed when the piston is heading up in the bore.

2) Exhaust valves wide open/Intake valves closed

3)Piston reaches top of cylinder, TDC

4)Piston starts downward motion

5)Exhaust Valves Closed/ Intake Valves Open

6)Fresh fuel and air drawn into cylinder

7)Piston reaches Bottom BDC/ Starts back up/Intake valve still open

(even though the the piston is rising, there is no compression occurring because of the open intake valves)

8)Compression begins when the intake valve closes IVC

9) Fuel/Air mixture starts to compress


Now we can talk about how to calculate DCR.

The ratio of the cylinder volume at IVC over the volume above the piston at TDC represents the dynamic compression ratio. The DCR is what the air fuel mixture actually "sees" and is what "counts", not the static CR.
Because DCR is dependent upon IVC, cam specs have as much effect on DCR as does the mechanical specifications of the motor.

This should hopefully clear everything up for you.

http://en.wikipedia.org/wiki/Image:4-Stroke-Engine.gif

This is a great way to visualize it. You can see the valves opening and closing. Remember compression primarily happens the "intake valve closes" IVC.

[07trx400ex]

There certainly is some truth is your statement. However even a 10.5:1 motor could ping, because remember there are many factors that contribute to detonation. Any time a 400EX owner is considering raising the compression, they must realize that THEIR motor may require race gas.

THANK YOU!!!!

Everyone wants more power, and along with improved throttle response and efficiency this is exactly what an increased CR does UNLESS

Detonation occurs. Detonation kills power and engines.

The concept to understand is the amount of CR an engine can handle.

This includes combustion chamber design, head material, use of combustion chamber coatings, etc. Once these mechanical aspects of the engine have been fixed, the main variable is fuel octane. Higher octane = more resistance to detonation and the ability to tolerate more compression.

This is about the most info I can offer because I need to go study chemistry, but wanted to explain this.

[GPracer2500]

Originally posted by 07trx400ex
....This is about the most info I can offer because I need to go study chemistry....

That statement jumped out at me. I like your attitude and applaud your interest in combustion chemistry (assuming you where serious). In my experience, it is an interest rare enough to be worthy of recognition. In other words, I'd like to encourage you to learn more. Personally, I enjoy delving into the rarely discussed and often misunderstood (at least among motorsport folks) subject of combustion chemistry. A few papers come to mind that you might be interested in reading. I'm not a chemist but read every credible source on the subject that I can find.

1) To help get a handle on some fundamentals and perhaps fill in some gaps, this one is pretty good:

Combustion
C.K.Westbrook
Prepared for submittal to the Encyclopedia of Applied Physics, April 1992.


2) This next one is a veritable gold mine for understanding how (at a chemical level) gasoline can produce engine knock (i.e. detonation).

The Chemical Kinetics of Engine Knock.
C.K.Westbrook, W.J. Pitz.
Energy and Technology Review, Feb/Mar 1991.

That paper, especially, is worth reading as many times as it takes before it starts to sink in. Westbrook and Pitz have been real pioneers in combustion modeling and the chemical kinetics of combustion. For example, we've known for many many decades that adding lead to gasoline substantially increases its knock resistance (i.e. octane rating). That fact was discovered experimentally a long time ago (everything under the sun was tested--lead worked better than just about anything else). But no one could really explain why it worked. We just knew it worked so we continued to use it. Westbrook and Pitz were able to explain the "why". If you read nothing else, read The Chemical Kinetics of Engine Knock.


3) Also, Detonation!, written by Keven Cameron and originally published in the now defuct Cycle Magazine is an excellent read. A reprint can be found HERE (http://www.factorypipe.com/t_deto.php).

I have PDF copies of the first two if you want them (or I can tell you where I originally found them). There is a tremendous amount of misinformation about deto and its related chemistry so use caution in evaluating sources of information. I've read more junk about the subject than I care to remember from people who appear to be credible and/or in a position of authority. I've learned the hard way that if its not published and peer reviewed its probably not worth even looking at. There are exceptions to that though (such as most anything written by Cameron).

[07trx400ex]

Hey Gp,

Yes, I was serious, but I was studying for an exam. I'm studying to be a ME and am very interested in those reads. Shoot me a pm or just reply back.