5knives

I've been thinking about adding a small nitrous kit to my H/C LS2. I was thinking something in the 50-75hp range, nothing crazy. My car has ported stock heads, ported FAST 90mm, and a small cam (don't know the specs off hand). My tuner flycut the pistons because of the milled heads with higher CR. Someone had made the following statement and it had me wondering what my concerns should be.

Also, a recommendation for an easy install kit would help too. Dry? Wet? I'm almost completely ignorant when it comes to nitrous kits for our cars and the majority of the info in this sections has to do with FI.

Any insight would be appreciated.

Thanks

BOO666

The only person that can answer that would be the tuner that did the work .

5knives

But what would happen if the edges aren't rounded? I'm curious what the issue would be. Hot spots on the pistons?

dennis50nj

yes the sharp edges create a hot spot and burn threw, if tapered and rounded no problem, I have the 243 heads milled and serdi valve job with pistons fly cut. no problems. I run a 100 shot with a safe fuel cell and c16 with the NA tune, and no KR

LSOHOLIC

Op......I run massaged 243's with a small shot on a flycut SBE also. And have yet to hurt a piston, its all about fuel and time management.....and staying humble..lol.

Not sure how much "tech/detail" your looking for but . The larger the cutter used on the intake side, the closer to the edge of the piston the valve relief becomes. Thus weakening the already thin ring land. And as most know, ring land size plays a big role in power adder piston strength.
A factory LS1-6 piston typically has a 0.250" thick crown, some guys have worried about the depth of the flycut but I have yet to see anyone hurt the piston via lack of "crown thickness".

Like Dennis was saying, the sharp edges of a flycut piston that where not blended can lead to trouble. The sharp edges can hold heat, thus helping a condition called per-ignition.
Pre-ignition happens when fuel begins to burn before spark ignition. Interestingly this often correlates to relative cylinder pressure. Just as an increase in octane improves the RESISTANCE of combustion so does cylinder pressure prior to ignition. IOW, just after the intake valve(s) close and the piston is relatively near BDC the in cylinder pressure is relatively low and EASIEST to ignite by say a hot spot on a piston or spark plug electrode. Once a burn has begun the pressure rises quickly, coupled to the crankshaft compressing things further the temperature rise is huge and piston melting/breaking can occur.

IMO, a wet shot is easier and safer than a dry shot for a beginner for multiple reasons. We can go into those if wanted.

Also keep in mind a tight quench combined with a large radius flycut adds "pressure" to the ringland and narrows your tune window.



Here is a shallow flycut with NO blending or radiusing.


Here is a flycut blended.


Here is a typical sized intake flycut blended, notice (on the intake side) how the distance from the edge of the piston to the end of the arc of the flycut is thin.


Here is a flycut piston that was sprayed and the thin ringland combined with the large flycut finally cost it. Hyper pistons will typically break up like this versus melt. But you can see how thin the factory ringland is in this picture real well. See (in the broke area) how thin it is from the exposed top ring to the top of the piston, very crappy ringland for a power adder piston but it is what it is.



Good luck on you combo.....

5knives

Ok that makes sense. Who flycut your pistons and did your nitrous install/tune, Cartek? That is who will be using (and they flycut the pistons) so I'm going to contact them and discuss my options.

All excellent info thanks. I'm not looking to push a big shot through this build. I'm at 485/430 right now and I figure a 50-75 shot should put me into the low-mid 500shp/tq, and hopefully safely. The car has ran flawlessly for years and I'd hate to suddenly break now because I had the itch for a little more power. But, that's the game.

dennis50nj

If Cartek did it I can bet they are blended, I did the NX kit, I did the tuning the old fashion way with plugs C16 jets and fuel pressure, I didnt need to change the ecm pcm, I data logged and checked afr KR and coolant temps during the passes on the street back road in the pinelands, It really made a big difference and seemed to really like it, never tried it at the track as I always remove for record runs and positive I would need the taller 305 35 18 mt dr tire on to finish in third

LSOHOLIC

LOL Dennis.........the old fashioned way, you mean the correct way. Plugs are the only way to know whats happening in the chamber !! Never been a fan of trusting afr's as the benchmark....but only as a reference to what the plug tells me. TR6 on motor and B8EFS on spray.

Mine is similar to yours, my NA tune is set. And I have a timing twister to "manually" pull time out, without messing with the NA tune.

I use to run a stand alone with C16 but I have now switched to E85 on the motor and now use E85 in the stand alone.

dennis50nj

Lol Caleb, e85 isn't that available around here, I didn't need to pull any timing the ground strap looked good and we don't run it that high NA, I tuned it with tr6s and really checked closely for signs of flecking then switched to the bre7 if I will spray it, but I dont like that plug NA for everyday driving, I guess I would have to change the fueling or something as it acts like loading up when idling and coming to a stop, I'm no expert on that, but have ran 600 on a stock bottom end 50lx
to 106,000 miles before cracking a cylinder wall