Probe piston ring Gap with Nitrous (power adder)

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SRT_DSTRHOLC

SRT_DSTRHOLC

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I have a set of probe pistons I am looking at and would be using Hastings plasma moly rings. This is their info on their site:

Top Ring: Multiply the bore size by .004 (ex. 4.000 x 0.004 = 0.016)
Second Ring: Add .003" to top ring calculation (ex. (4.000 x 0.004) + 0.003 = 0.019)
For power adders, increase gap by 0.005"



If I have 4.040 bore size and multiply 4.040 x .004= I get .01616, so I would add .005 and get = .02116 correct? For a gap of .021 or .022?

Then for the second ring it says add .003 to the top ring so that would be .024 or .025?

Thanks
 
Fst73_360 said:
I have a set of probe pistons I am looking at and would be using Hastings plasma moly rings. This is their info on their site:

Top Ring: Multiply the bore size by .004 (ex. 4.000 x 0.004 = 0.016)
Second Ring: Add .003" to top ring calculation (ex. (4.000 x 0.004) + 0.003 = 0.019)
For power adders, increase gap by 0.005"



If I have 4.040 bore size and multiply 4.040 x .004= I get .01616, so I would add .005 and get = .02116 correct? For a gap of .021 or .022?

Then for the second ring it says add .003 to the top ring so that would be .024 or .025?

Thanks
Click to expand...


I would run .026 top and .024 second if it were mine....
 
ou812 said:
I would run .026 top and .024 second if it were mine....
Click to expand...
Thank you Brian. I see that a majority of the time that the second ring gap is bigger in most cases, why is that and why is that not the case with your suggestion? Just trying to learn.
 
Always play it safe with ring gaps on NO2 motors. No power will be lost by adding a little extra gap. I agree with Brian .026 top and .024 sec.
 
Those are hastings or probes specs? What material pistons?There are unanswered variables here.Hypereutectics need more clearance than cast.I would go by piston specs. Edit,sorry did some research and see you are using probes specs and that their pistons are forged.
 
Fst73_360 said:
Why this over the .026 and .024 suggestion?
Click to expand...

Like Brian and Skrews - just a matter of opinion based on individual experience.
IMO most forged pistons do not transfer the heat to the top ring as much as some hypereutectics do so unless you are planning to run it hard on a plate (meaning tuning the NO2 for max power) I don't feel there's that much of a risk of rings butting. The normal N/A gap would be .016-.018 on them. The ".004 per inch of bore" is a good fall back if you don't have a spec from the piston and/or ring manufacturer. So with Hastings adding another .004-.005" you've already got what you need. IMO, any "extra" gap on the top is detrimental to power.
On the larger 2nd ring gap - The top ring seals against the cylinder wall and the lower surface of the piston's ring land. The 2nd ring is not a compression sealing ring by design. It's an oil scraper. The theory is at higher rpms is the 2nd ring can trap gas pressure between it and the top ring, that pushes the top ring off the land and again, some ring seal is lost. So the thought is more gap on the 2nd means less possibility of the top ring being unseated.
 
daredevil said:
Those are hastings or probes specs? What material pistons?There are unanswered variables here.Hypereutectics need more clearance than cast.I would go by piston specs. Edit,sorry did some research and see you are using probes specs and that their pistons are forged.
Click to expand...

Probe is Forged.
 
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