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Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.
I'm working on a full forged 2jz with 86.5mm cp pistons for drift that will be running on e85. On the CP piston ring sheet ring gap recomendation says for top ring : bore x 0.0055" (3.406 bore x 0.0055" = 0.01873"(0,466mm) I'm doing it right?
Do you think I would have to use less ring gap due the car will be running on e85?
thanks to all!!
I'm not sure why E85 would require a looser ring gap. If anything, E85 gives you the opportunity to advance spark and increase boost, which would increase cylinder pressure. I would not run tighter than the 0.0055"
Generally with alcohol based fuels the rings are subjected to less temperature than on gasoline based fuels so yes, it's possible to set the ring gaps a little tighter. This all needs to be considered along with your boost/power targets though since as the power level increases your'e again going to be producing more heat in the combustion chamber.
What's your target power level, boost level, and what will the engine be used for?
We spect to see around 650-700hp on 1.7bar approx. on a garrett gtx35 genII for Drift championship.
In this application I'd be inclined to think that 0.018" is a little conservative but it's certainly not ridiculous and is guaranteed to be safe. You could potentially run around 0.016" but the reality is that the gains you're likely to see would also be minimal in this range. As an example, I'm typically in the region of 0.0045-0.0050 per inch of bore on the top ring for that sort of application.
Andre in the case of going too far, for example, top ring on a CP piston, was aiming at 0.020 on a 86.5mm bore. Sadly the end result was 0.022-0.024. Second ring is at 0.018 and i know it should be wider than the top ring gap.
This engine for example was supposed to be a drift machine, last tune had 450hp @ 25psi. Since these cars spend most of their time in high rpms, soaking in head for minutes. How bad would it be to go 0.022-0.024 and give the second rings a 0.026 gap?
I already got a new set of rings and a ring gap grinder but i wonder, since i do have those new rings there
What did you wind up doing?
@Lopin18 I'd personally be inclined to get another ring set and set the gaps correctly. It's often surprising what you can get away with in terms of ring gap, but it's certainly not going to improve your chances of having an engine that performs well with minimal blow by and low oil consumption. It's also a much cheaper proposition to change the rings before the engine gets assembled rather than pulling it back apart at a later point.
Hi hope you dont mind if i add to this as my question is relevant to the topic.
I have had all machine work done to an rb25 and machine shop set the rings on the loose side so ive decided to purchase a new set. Speaking with the guys from Nitto they recommend on an 86.5mm bore .014-.016 on the top ring and plus .004 extra on the second which would be suitable for street and 1/4 mile drag up to 500kw at the tyres. My application will be e85 and whatever boost the precision turbo will make (leaving this for my tuner to decide)
Do you have any thoughts on the total seal gapless ring set, i have a set on the way but second guessing the decision now.
I've used the total seal gapless rings in our drag engines and they worked pretty well. I'm not sure i really saw any advantage in terms of power but they did reduce blow by which was previously a problem since we were running upwards of 45 psi at that point. They don't however seem to last that well which would have me question their use in a street engine that's going to see a lot of use between tear downs.
Ahh ok they have quite a good sales pitch but failed to mention the rate of wear.
Is it best to monitor this with a leakdown test and at what point would you say its time to freshen up.
The gap chart is also something ill need to seek advise on as they show .0085" for top and .008" for the second ring for 30+ boost on e85 so its .029 top and .027 (roughly) for a 3.405" bore
As the rings wear you'll find that blow by past the rings increases. in our drag engines we monitored crankcase pressure to help baseline blow by. If you're regularly base line power testing you'll also see the power start to fall away slightly. Lastly this would also be coupled with an increase in oil consumption. Note that this is just my experience with the total seal gap less rings. I'd guess however that if there was a clear cut advantage of this sort of design then OE manufacturers would have been all over it.
Total Seal had problems with their gapless top ring, discontinued it using a gapless 2nd ring, and then reintroduced it using larger end gaps.
Did the engine that developed sealing problems have gas ports? Was the top or 2nd ring gapless? What procedure was used during assembly and was it broken in with a high ZDDP oil? Were the rings installed in new pistons?
The blow-by is a problem on many turbos. I'm thinking gas ported gapless top rings might significantly reduce that.
On NA engines Total Seal claims big improvements during the intake stroke.