7m pistons

[Bomberillo]

Ok so I have searched but have not really found what I am looking for.
I dont know what piston gasket combo to buy. I am going forged pistons but i am worried about what compression to buy them. I was thinking of 9 to 1 wisecos with a 3mm headgasket but I am worried about quench area. Or 8.4 to 1 Je's with a smaller head gasket. I plan on running about 500 hp with a safc afm and 550's. However I want to keep the octane level at 91 and not have to pump race fuel to prevent detonation.

 

[quake]

Ok so I have searched but have not really found what I am looking for.
I dont know what piston gasket combo to buy. I am going forged pistons but i am worried about what compression to buy them. I was thinking of 9 to 1 wisecos with a 3mm headgasket but I am worried about quench area. Or 8.4 to 1 Je's with a smaller head gasket. I plan on running about 500 hp with a safc afm and 550's. However I want to keep the octane level at 91 and not have to pump race fuel to prevent detonation.

i ran the 3mm and wiseco for 12k miles and all was well but you need to calculate how thick the gasket needs to be based on how much has been removed. Second i did not do much part throttle boosting after the piggy backs as i had no timing control.

 

[grimreaper]

ptb shouldnt be an issue with a piggy back as you should not be able to affect the af ratios and subsequently timing when its in closed loop (Assuming the throttle percentages are setup correctly and any low throttle map is zeroed).

 

[Bomberillo]

i ran the 3mm and wiseco for 12k miles and all was well but you need to calculate how thick the gasket needs to be based on how much has been removed. Second i did not do much part throttle boosting after the piggy backs as i had no timing control.

What do you mean by this part throttle boosting? Does that mean you had to floor it anytime you went under boost

 

[Doward]

Timing is not based on AFRs

 

[quake]

What do you mean by this part throttle boosting? Does that mean you had to floor it anytime you went under boost

didn't have to just did not part throttle boost it for very long. You have no control over timing nor know how much the car is running

 

[quake]

ptb shouldnt be an issue with a piggy back as you should not be able to affect the af ratios and subsequently timing when its in closed loop (Assuming the throttle percentages are setup correctly and any low throttle map is zeroed).

it is an issue and lots of people don't realize this when setting up their car thus we have lots of rod knock posts mean while the mk4 guys post dyno vids

 

[Bomberillo]

So how do we get rid of this ptb issue. Is a standalone the solution or is it uncureable.

 

[maac0953]

go with HKS 1.2mm head gasket ok.

 

[quake]

So how do we get rid of this ptb issue. Is a standalone the solution or is it uncureable.

standalone would be ideal but depends on your budget also don't just pick a size for the gasket calculate it so you can control your compression

 

[grimreaper]

i understand that timing maps are selected on predetermined loads, temps etc. If your not making adjustments there is no change in the maps used other then what a stock ecu would use. Since you shouldnt be adjusting anything under 70-75% throttle (safc) how is a ptb situation affected by the piggyback when there are no adjustments made in that throttle % range? is there something im overlooking?

 

[jdub]

i ran the 3mm and wiseco for 12k miles and all was well but you need to calculate how thick the gasket needs to be based on how much has been removed. Second i did not do much part throttle boosting after the piggy backs as i had no timing control.

didn't have to just did not part throttle boost it for very long. You have no control over timing nor know how much the car is running

it is an issue and lots of people don't realize this when setting up their car thus we have lots of rod knock posts mean while the mk4 guys post dyno vids

standalone would be ideal but depends on your budget also don't just pick a size for the gasket calculate it so you can control your compression

Grim - I don't think you are missing anything...I'm confused too...the above does not make sense. Especially the part about causing rod knock. Care to explain (in detail vs general statements) how/why boosting under part throttle conditions is an issue with piggyback fuel control?

 

[quake]

Grim - I don't think you are missing anything...I'm confused too...the above does not make sense. Especially the part about causing rod knock. Care to explain (in detail vs general statements) how/why boosting under part throttle conditions is an issue with piggyback fuel control?

under the assumption that you are running more boost or have a larger turbo than stock you are already behind the 8 ball, as you have more air flow and the same timing. Maybe you need more maybe you need less? who knows. The stock ecu piggy back or not will over time change your tune now you have pulled fuel and advanced the timing that is not very good. As for the rod knock you can pound the rod bearings with detonation and not know it next thing you know rod knock... it don't have to be just an oil problem.

The mk4 has a more advanced ecu than we do also u can see better what is going on with your motor. So if you must run your piggy back you do the best you can with what you got to keep the car out of closed loop

 

[jdub]

under the assumption that you are running more boost or have a larger turbo than stock you are already behind the 8 ball, as you have more air flow and the same timing. Maybe you need more maybe you need less? who knows. The stock ecu piggy back or not will over time change your tune now you have pulled fuel and advanced the timing that is not very good. As for the rod knock you can pound the rod bearings with detonation and not know it next thing you know rod knock... it don't have to be just an oil problem.

The mk4 has a more advanced ecu than we do also u can see better what is going on with your motor. So if you must run your piggy back you do the best you can with what you got to keep the car out of closed loop

Well...those are pretty much all bad assumptions.

1) Where in this thread does the OP say he's running a larger turbo? Off we go on a vector that has nothing to do with thread topic.

2) Grim is correct - The 7M ECU selects basic engine timing from values stored in memory. It then adds/subtracts based on corrective values...warm-up (adv), over-temp (ret), AFR feedback (adv), idle load (adv & ret), and knock sensor (ret). Max advance is 35 to 45 deg, min advance is -10 to 0 deg.

3) More boost = need for more fuel. At WOT where acceleration enrichment (up to a 20% volume increase) occurs...you may need to pull fuel to keep from from running pig rich.

4) So you think that the rods are going to take a hit from detonation? Is that before or after your pistons self destruct? The knock sensors will pull a huge amount of timing before that happens. You may still torch a piston though depending on how lean AFR's got.

5) And, what does a Mk IV ECU have to do with any of this when we are talking about a 7M ECU?

6) Closed loop is when AFR feedback is functioning....it will always try to achieve stoichiometric AFR. It does cause problems attempting to add/sub fuel with a piggyback when functioning. AFR feedback does not occur (open loop) when: engine start, after start enrichment, power enrichment, coolant temp is low, and during fuel cut-off. The SAFC is most useful for controlling fuel during acceleration....during open loop when the ECU commands power enrichment.

If you are going to post in the tech sections, get your facts straight...all you posted was a bunch of hearsay or what you think you "know".

To the OP: To calculate HG thickness you take material removed from block + material removed from head + 1.37mm = required MHG thickness to stay with stock compression.
The pistons you choose will need to be in the 8.4:1 range to stay stock as well.

You can pretty much ignore anything concerning "part throttle boost" that was previously posted.

 

[quake]

Well...those are pretty much all bad assumptions.

1) Where in this thread does the OP say he's running a larger turbo? Off we go on a vector that has nothing to do with thread topic.

2) Grim is correct - The 7M ECU selects basic engine timing from values stored in memory. It then adds/subtracts based on corrective values...warm-up (adv), over-temp (ret), AFR feedback (adv), idle load (adv & ret), and knock sensor (ret). Max advance is 35 to 45 deg, min advance is -10 to 0 deg.

3) More boost = need for more fuel. At WOT where acceleration enrichment (up to a 20% volume increase) occurs...you may need to pull fuel to keep from from running pig rich.

4) So you think that the rods are going to take a hit from detonation? Is that before or after your pistons self destruct? The knock sensors will pull a huge amount of timing before that happens. You may still torch a piston though depending on how lean AFR's got.

5) And, what does a Mk IV ECU have to do with any of this when we are talking about a 7M ECU?

6) Closed loop is when AFR feedback is functioning....it will always try to achieve stoichiometric AFR. It does cause problems attempting to add/sub fuel with a piggyback when functioning. AFR feedback does not occur (open loop) when: engine start, after start enrichment, power enrichment, coolant temp is low, and during fuel cut-off. The SAFC is most useful for controlling fuel during acceleration....during open loop when the ECU commands power enrichment.

If you are going to post in the tech sections, get your facts straight...all you posted was a bunch of hearsay or what you think you "know".

To the OP: To calculate HG thickness you take material removed from block + material removed from head + 1.37mm = required MHG thickness to stay with stock compression.
The pistons you choose will need to be in the 8.4:1 range to stay stock as well.

You can pretty much ignore anything concerning "part throttle boost" that was previously posted.

thanks i did not know

 

[quake]

so what happens if you get a bad batch of gas? and what makes you think if you detonate you have to damage a piston.

 

[jdub]

Bad gas?...as in lower octane that shown on the pump? When the knock sensors detect a 7 kHz frequency, the ECU retards timing...that's why they are there. The stronger the frequency, the more the ECU retards timing. You get a tank of "bad gas", the performance is consistent....when engine ping starts, the ECU pulls timing. It will never get severe enough to damage the rods, but you can damage the piston tops and the HG. If you keep pushing the power with engine ping, you are a fool

Are you trying to tell me the piston lands/rings are stronger than the rods? Even mild detonation will cause pitting on the piston top. Detonation is explosive combustion vs a normal air/fuel burn and is at a much higher temp. It can burn a hole in the piston top, expand the piston to the point where it breaks the rings, or cause the skirts to scuff the cylinder walls. The rods will be put under additional load, but not near the amount of stress the piston will be...the piston top is in direct contact with the detonation event and subject to the huge temp increases that result. Rod damage to the point of rod knock is the least of your worries if the motor is experiencing detonation or pre-ignition.

A far more common reason for rod knock is a BHG...coolant in the oil trashes the bearings.

What is really your nightmare is if an injector goes bad and suddenly cuts flow. Instant lean turns the combustion chamber into a plasma cutter. I will promise you when you see the result (there's a recent thread on it), you will see why the piston is what takes the main hit.

Edit: Found it...classic injector failure:
http://www.supramania.com/forums/showthread.php?t=87854

 

[quake]

Bad gas?...as in lower octane that shown on the pump? When the knock sensors detect a 7 kHz frequency, the ECU retards timing...that's why they are there. The stronger the frequency, the more the ECU retards timing. You get a tank of "bad gas", the performance is consistent....when engine ping starts, the ECU pulls timing. It will never get severe enough to damage the rods, but you can damage the piston tops and the HG. If you keep pushing the power with engine ping, you are a fool

Are you trying to tell me the piston lands/rings are stronger than the rods? Even mild detonation will cause pitting on the piston top. Detonation is explosive combustion vs a normal air/fuel burn and is at a much higher temp. It can burn a hole in the piston top, expand the piston to the point where it breaks the rings, or cause the skirts to scuff the cylinder walls. The rods will be put under additional load, but not near the amount of stress the piston will be...the piston top is in direct contact with the detonation event and subject to the huge temp increases that result. Rod damage to the point of rod knock is the least of your worries if the motor is experiencing detonation or pre-ignition.

A far more common reason for rod knock is a BHG...coolant in the oil trashes the bearings.

What is really your nightmare is if an injector goes bad and suddenly cuts flow. Instant lean turns the combustion chamber into a plasma cutter. I will promise you when you see the result (there's a recent thread on it), you will see why the piston is what takes the main hit.

Edit: Found it...classic injector failure:
http://www.supramania.com/forums/showthread.php?t=87854

the last thing you will do is explain to me how the system operates with your bench racing. I leave it at that as i am not here to try to show everyone how smart i am.. by the way he is using a 60trim turbo but for now i am done when i get home i'll be sure to toss out the books that i got from toyota school :nono:

 

[jdub]

the last thing you will do is explain to me how the system operates with your bench racing.

I'm no bench racer...I don't have to explain crap to you (I see it does a lot of good). And, I am done with you and your insults.

I leave it at that as i am not here to try to show everyone how smart i am..

I'm not here to prove anything...sorry it intimidates you.

by the way he is using a 60trim turbo but for now i am done when i get home i'll be sure to toss out the books that i got from toyota school :nono:

Got the same books sport...and, a couple others you obviously don't. Not my fault you seem to have a hard time grasping the info in those books.
What you need to toss out is the attitude and the residual teenage ego.


Since you decided to turn this into a personal insult pissing contest...this thread is done.