DSmith

When I built my old engine I had forged pistons because I planned to spray but never did. When I was buying pistons for my current engine I told my parts guy I was just gonna go with Speed Pro hypereutectic pistons because it was a n/a engine and I wasn't gonna spray. He told me I could still use nitrous with hypereutectic pistons and he had racers hitting 200+ shots on 'em.

The first set of hyperteutectic pistons I bought (back in late 80's,early 90's) this same guy told me not to use nitrous with these pistons.

I realize the technology has changed but I would like to know if any of you guys use nitrous with hypereutectic pistons? If so, how big of a shot and how long have they held up?

Camarslow

As long as you don't let it lean out, a 100-150 shot kit like the one sold by NOS for TPI cars (http://www.jegs.com/i/NOS/741/05151/10002/-1) is, as i understand it, meant for a car with a stock bottom end. If you let it lean out you will melt some pistons.

3rd gen Will

iTrader: (8)

Just make damn sure you stay out of detonation, from what I understand the piston's tend to shatter.

EvilCartman

iTrader: (1)

Buddy of mine sprayed just a 125 shot using hypers, no problems.

jerryd87

iTrader: (2)

if you actually call and talk to the engineers at a company like keith black(like i did before i bought my pistons) they will tell you that hypereutectic pistons are actually stronger then forged, however they are more brittle, so if the engine is tuned correctly with no detonation you will be fine. personally i wouldnt try it unless running mpfi though becuase mpfi allows greater percision.

DSmith

Thanks guys. I'm gonna try it, just start out with a small shot and work my way up to make sure everything is set correctly.

The Man

i had a set of the speedpro hypereutectic pistons in my 92 z28. I was spraying a custom(NX and NOS BiGSHOT) set up with 197 RWHP. timing was stock 6 degress and i was running good unleaded race fuel. 2 steps colder on plugs and gap them tight. set the fuel psi with it flowing so u dont lean out.

LB9GTA

iTrader: (1)

hypers are only good for a 150shot at the most!

I have now blown 2 engines with hyperU pistons.

The first was a stock 305 with steel heads. I sprayed a 165hp shot and the tranny slipped and over-revved the engine and POP goes the piston.

2nd engine was my 383 stroker. I was using a mix of pump gas(94) and race fuel(110). Same senario, the tranny slipped and over revved the engine and BOOM.


Lesson= stay below the 150shot on hypers.
Anything more than that is a gamble.

Another lesson- ALWAYS use more octane in the fuel than needed, If they recommend 91octane, use 94 and so on.
Fuel is cheap compared to an engine !!

DSmith

150 is the most I would try without forged parts. I need to get a 6AL box cause all I have now is a 6A and use the rev limiter in the ECM. I'm sure it wouldn't be good for the ECM to cut off the fuel at 6500 with the button pushed on a 150 shot.


I just noticed you are running a dry shot, mine is a wet kit. I don't have the guts to try dry.

sailtexas186548

iTrader: (2)

you could just run a window switch to cut the spray at 6300 or 6400 so you never have to worry about over revving w/ the nitrous or having the ecm cut fuel while spraying. or better yet a window switch AND 6aL

The Man

its not the piston fault u over rev it. the pistons will hold if u set the fuel psi flowing, run good fuel, window switch 3000-5500(TPI), .020 gap on 2 step colder plugs. my timing was 6 BTDC. I ran this for 2-3 years and 30 bottles through it. I stepped it up to the 250 shot and tranny didnt want to shift out of low until i let out, made 3 passes. Last pass got a head gasket. Pistons were fine. Use a WOT Swith, fuel cut off switch, and a window switch and u will be fine.

3rd gen Will

iTrader: (8)

Window switch is a must on a manual and a good idea with an auto. In my opinion a rev limiter is a good idea on anything you plan on racing. If you rev limiter cuts fuel a window switch is mandatory unless you want to blow up your engine.

ziggy89

what about on moly coated rings. i was told they chip or flake or sumthing like that when they are sprayed?

89_RS

The 6AL will only cut spark, so no problem there.

jerryd87

iTrader: (2)

ive personally not heard of them chipping or flaking just from spraying, however i do know they take longer to break in then normal rings. if they where going to chip or flake with spray they would with turbo and supercharged engines too so im betting it was from something like detonation

articwhiteZ

iTrader: (56)

Lesson= use/get a rev limiter..
thats ok the only time my rev limtr kicked on 1 time also... was coming off the freeway..i slip it into N.. forgot i had the cruse on..lol
i know it works..LOL