I just read a very interesting post on the use of aluminum alloys in pistons; it was by an engineer type on our ZR1 letter list. I thought that since it was a slow news day, I would give you a little synopsis of what was said with a comment or two (Hope of course this is not all old news) 1. Claim is made that the primary alloying agent for AL pistons is Silicon. (Copper or other things can be and are usually there in small trace amounts). 2. Claim is made the the Silicon actually weakens the piston, does NOT make it stronger. Further claim is made that it really increases the brittle nature of the piston and therefore makes it MORE vulnerable to failure on detonation (like in a turbo engine). 3. The amount of silicon in early aluminum piston engines was very low; maybe less then 6%. Current pistons may go upwards of 17-18% but never higher than about 23% (or much more than what they call eutectic) because that would make the alloy VERY BRITTLE AND WEAK. 4. Further Claim is made that the reason for the increased silicon is to make the piston expand less under thermal pressure. This allows the piston to be machined to tighter tolerances and potentially can reduce oil & hot gas blowby. This is considered a key element in getting the engine to meet increasing less tolerant emissions standards. 5. Further, it is Claimed that the engine EGT is about 1200, which is very dangerously close to the melting point of the allow and that only a lot of excess air going through the cylinder keeps the piston from doing a meltdown. Hence these new engines are running just about on the limit of lean (high) combustion temperatures and pressures. Which brings up some questions: a) - what would this tell us about just bolting on a turbo or supercharger on a normally aspirated engine without looking into the piston characteristics or the compression ratio? (It would make me think twice about it!) b) - does anybody have an idea on current Ferrari practice in this area (say in todays 360/430 engines) versus something like my 86 Testarossa? How about versus the really old time engines, like a 250 series V12? Just wondering, James
You can get some confirmation about Silicon content and its affects near the bottom of this link: http://www.bmeltd.com/pistons.htm . The page lists some typical alloy types such as 4032 or MS75. There should be sites where you can find the composition of those alloys. Gerrit
Bill Miller has, or at least had, a Testarossa and had scuderia decals on the end plates of his top fueler's rear wing. I don't know if he did any piston work for his TR.
The aluminum pistons with silica content is also known as a "hypereutectic" piston. This piston, as used by Ford, is preferred as it's more thermally stable (i.e. expands/contracts less) than a similar cast or forged aluminum piston. That allows tighter piston clearances and looser ring clearances to allow thinner oils to be run in the engines (5w-30) and lower drag/friction in the cylinder bores allowing more fuel efficiency and power. Downside? They're fragile. Don't even think about supercharging or turbocharging one of these. A good example was Ford's 2V 4.6 liter engines in the Mustangs. Any forced induction about 6 psi boost was asking for problems. When Ford built the 2003/2004 SVT Cobra motor, those were built with forged crank, connecting rods and forged pistons. Here's a good explanation of hypereutectic pistons: http://en.wikipedia.org/wiki/Hypereutectic_piston For my Mustang SVO, I used forged pistons because I need a reliable piston that can withstand high temperatures and 20+ psi of boost. As for Ferrari 3.0 liter motors (2v or QV), I'm unsure if they're forged or cast, but I'm reasonably certain that they're not hypereutectic.
Thanks, that was exactly what I was trying to tell a certain couple of young men who just bolted up a supercharger on a non-turbo engine. And not a particularly designed-for-high-performance engine either... BTW, I brought up the subject because their mechanic showed me what they had him do; his comment was that he was just following customer orders. You completely confirmed what the other experienced guy on the ZR1 site had said. James
I am not sure of the make-up of the older V-12 pistons but I have been told by old timers that if you drop one it will shatter like a coffee cup.
Hello everyone....I was pleased to find your site today and as a car lover ( I don't own a Ferrari nor ever ridden in one) I simply enjoy sharing in everyone's views. My son and I have 6 Corvettes between us and have been playing with boost for several years now. It certainly is wise to have forged pistons when supercharging or turbocharging but it isn't absolutely necessary. I don't know what type pistons and compression ratios are standard in Ferrari cars but can reasonably assume that they are stout and of high quality. Most important is the tuning. This is best done on a chassis dyno while air/fuel ratio and knock is closely monitored. My 95 Corvette has Hyper pistons with 10.5 -1 compression ratio. As an after thought we installed a ProCharger w intercooler which boosts up to 12 psi. Car was dynoed to 5800 rpm producing 473 horsepower. Car easily goes to 6500 r but A/F ratio started to get lean. Desired is 11.7- 1 while under boost. We plan to retune it on dyno within next 2 weeks and expect 500 + at the wheels. My son also fabricated a turbo system for his 96 Corvette with 18 lbs of boost. Tuning the engine is fairly easy with computer controlled cars and not too difficult with the older ones. We next plan to install a pair of gt35 turbos on a 91 ZR1. We wont exceed 6 lbs of boost. Basically the piston strength determines the amount of boost and timing advance one can safely go to. I found that my MPG got better when cruising at 70 mph at 2100 rpm in 6th gear. We run an AF ratio of 14.6 - 1 until boost gauge shows 0 atmospheres. Whether your car is EFI or an older standard model I highly recommend an LM1 kit w wide band oxygen sensor. This will let you know your AFR while you drive in all ranges. We have used this for advanced tuning when testing the car at a dragstrip on test and tune days. Thanx for allowing me to share in your forum.
I can tell you with a QV the pistons are quite strong. I ran 10 psi for a few years before adding an intercooler and going up to 22 psi and about 520 hp for a couple more years and all was fine. One day at the drag strip I had a trigger bugger up the timing badly causing it to detonate severally enough to shatter 4 of the spark plug insulators, no problem with the pistons though. Ferrari uses good parts.
Welcome to the Forum, Chris...I didn't even notice that it was your first post. (seldom do we see somebody pick a backwater tech thread to post in the first time!!!) If you ever get by Dallas I will give you a ride in the Testarossa for sure. BTW, I was with either Corvette or Porsche for years, and currently have a 1995 ZR1 and a 2004 Z06. Don't let anybody call you a Corvette Neanderthal around here either - we occasionally have a thread like that, but everybody is secretly scared of the new ZR1 in their hearts. James
Here's a decent primer on pistons. http://forums.nasioc.com/forums/showthread.php?t=907570 Brian Nutter of Wiseco posts over at ls1tech.com and has posts discussing materials, clearances, etc. Wiseco is one of the very few that has thier own forging plant. Most of the makers of custom pistons sold in the aftermarket purchase blanks for machining from outside vendors. Wiseco does all thiers inhouse from ingot to final machining from this thread http://ls1tech.com/forums/showthread.php?t=458776 "As for 4032, I guess I'll just say that 4032 is a step up from Hypereutectic, but not what most manufacturers use for Turbo or nitrous applications. If you don't detonate, it will live ok. Even in some high end applications, 4032 can be a "ok" choice. NHRA Prostock is one exception in "pro level" racing where 4032 is preferred over 2618...but this is usually because of the perfect tuning and a "weight reduction at all costs" mentality....try a set of pistons every 60 runs. Guys that were the "first 3rd gen in the 6's at over 200" were running 2618 alloy when they did it.. 4032 is 3% lighter, has better wear "appearance" when pulled out of a run engine due to it's high silicon content. 2618 gets shiny and gets vertical scratches if the oil isn't kept clean, but for the most part maintains it's "shape". Installed clearance on each can be the same if the 2618 piston is engineered correctly. Things like offset pins can overcome the generalization that forged pistons (especially low silicon 2618) are noisy. If you've ever seen an engine, with a dropped valve for instance, and the forged piston is a bunch of nickle sized fragments in the oilpan....that's 4032. If you've seen the piston wrapped around the valve head like taffy, that's 2618." ------------------ "4032 is good for street and mild racing applications. I personally don't think that 700 horsepower "street engines" should run "street" quality pistons. A wise LS1 engine builder told me...If a LS1 guy isn't running nitrous or supercharging when they first drop a new engine in, they will be soon enough, so just build it right the first time. Many Many Many people with over 100K miles with 2618 alloy have had no ill effects. As long as the ring grooves are flat to begin with and the rings are good quality (flat themselves), vertical clearance in the land is not an issue. I've run between .0005 clearance up to .0025 vertical clearance with no changes in power...In fact, some of the latest o.e. race engines have begun to specifically open up the top groove clearance to allow the ring to twist more for better seal. The ring doesn't seal on the flat surface of the land anyway, it seals on the outer lower lip. As long as that stays "round", you're in good shape. The original post is this...the engine may be run up to 20 lbs at some point. We ARE talking about an engine with 700 to 800hp potential EASILY. There is limited room for lands and .235 tops are well under the .300 that ANY piston maker would prefer for a boosted application given enough room. ONE tank of bad gas is enough to pop a thin .235 top land even with 2618 alloy, so why take the chance. I guess my main point is at least 5 of the biggest and most respected players in aftermarket LS engine buildups ALWAYS use 2618. I'm taking the high road here and leaving the names of those companies out of this post. That's not what this post is about. You don't hear people whining about noisy engines from these respected engine builders. Every piston company in the U.S. (except one) uses 2618 alloy for boosted and nitrous applications. If you don't hear a lot of pissing and moaning over 2618 alloy pistons making noise (especially the offset wrist pin ones), why WOULDN'T a guy use 2618 alloy." ------------------ "Yep..I sell a lot of 4032 alloy pistons. I'll even give a guy a .235 top land 4032 LS1 Turbo piston if he really wants it, but it wasn't my idea and I'll tell him as much before I let him order it. I'd regard 4032 to be the same "quality" as 2618 for specific applications (Nhra Pro stocker's like it, 2 of the 4 fastest guys this last weekend we're running our 4032 pistons), but I'd never recommend it for what is going on here. There's no reason to. Not to bash one specific manufacturer here, but what works for a MG or Porsche Scca racer doesn't apply to a drag racer or circle track guy. Believe me, the reason for that particular piston to be made from 4032 is not for any scientific reason I can think of. As for my personal experience, I've seen so many examples of 4032 (every manufacturer) breaking and shattering into tiny pieces (total engine rebuild) that I will say again that I'd never recommend 4032 for a boosted application. There just isn't a good reason to. 2618 will ALWAYS put up a better fight and it lasts a long time if designed right. As dyno experience, We've got 2 dyno's that do nothing but piston testing all day. (I won't get into my own personal experience).. There isn't an engine made that makes as much power after 24 hours as it does in the first few minutes. Pistons loose 25% of the heat-treat relatively quickly. The only way to recover power is to re-cut the ring grooves and install new rings...then make BETTER power than originally....a little known secret. The one big issue here is most people(with their own budgets) don't often get a 2nd chance to make the right decision." -------------------- "recutting ring grooves. The technology is there to cut a ring grooves with flatness in the millionths, but very little run time is needed before they're all "out of wack". The heat treat on new pistons is hopefully in the high 60's or low 70's, but it doesn't take a lot of run time to bring that down into the low 50's. Ones that are run lean can be in the 20's or single digits (you'll also see the bottom of the piston with a carmel color on these). Basically, the pistons stress relieve themselves. It's actually the recutting of the top ring groove that gets the power back. You won't even find to many NHRA prostockers that are willing to do it because it's a pain in the butt. We initially use a cutter that's built for one of the "ground" rings that's available (the ones that are REALLY flat and have a nice finish). When the pistons come back, we use a "slightly" thicker cutter and ring. This ensures that there is "fresh" material when we re-machine. -Brian"
To both 350HpMondial, and most certainly also thanks to JCR for the detail - I can only say that I am amazed!!!
James, I did a google search on the Testarossa and found some intriguing information. Do you know of a site that I may be able to see a drawing of the engine and undercarriage? Also would like some info on the fuel and ignition system. From what I gathered so far there are engine management systems available at a reasonable price where you can recurve your timing and fuel delivery...if you are considering boost. I'd really like to see some detailed pictures of the engine and the exhaust system as it's laid out. It was fairly difficult to fabricate a neat turbo set up for the 96 LT4 ,,, but the finished product looks great and works even better. I don't think the Testarossa would be much more difficult than a Zr1. 4-6 psi would make it a screamer. Chris
One of our sponsors here, Norwood Performance, has done many turbo TR cars in the past. He is also a general Ferrari hand and does my Testarossa work. If you hunt through the TR section there are some engine shots (exterior) but I don't know of an internal drawing other than service manuals. One thing you should know is that there have been at least two and maybe three iterations of the upper manifolding between regular Testarossa, 512TR, and the 512M...and of course that us early car owners are already so scared of our transaxles that we will barely use what little 380hp we already have. Even the newer upgraded diffs and gears are known to have broken under high stress. BTW, I know we are off topic everybody; maybe Chris & I should start this part of it over in the TR section? On the other hand, it was MY THREAD in the first place and Chris is the new guy! Just kidding of course - James
I can save you a *lot* of heartache. Don't push that 1995 LT-1 Corvette to 6200 RPM: http://vette.ohioracing.com/majmods.html
