I got my hands on a complete set of forged pistons with pins & rings for about cheeseburger under $200. The problem is the spec sheet that is usually given with custom pistons wasn't available. It came from a reputable engine builder, and they appear completely new/uninstalled or ever fitted. The pistons were custom made to order by Diamond Racing Pistons. My guess is they were ordered for a build that never happened, and given that I don't know of many all-motor LE5s I'm hoping that these are stock or lower compression pistons as they might be part of my LE5 turbo engine build.
The only info I have right now is that the are stock 3.4645in (88mm) bore for a 2.4L LE5, and that the compression height is 1.082in (27.48mm). After a few hours research I keep finding a loop of conflicting information about what the stock compression height of a LE5 piston is. Some parts sites list it as 28mm or 1.102in and others list it as 1.092in (27.74mm).
So in effect the pistons I purchased are either 0.010 or 0.020 inches shorter from deck height at TDC. What I'm wondering is other than lowering the compression of the motor, what effect negative or positive would a 0.010 - 0.020in reduction in piston compression height cause. This is assuming that I use stock rod heights, since at the moment I'm planning on picking up K1 rods for the LE5.
Is this a significant enough change in tolerance to negatively impact quench and maybe fuel injector spray angle? (I'm stretching my understanding here, forgive me I'm still learning)
I thought that maybe I could have the head or block machined to bring it back into spec but I'm worried about the cam gears then being misaligned and messing with the VVT. I'm not yet sure if any retardation to the cams from moving the head closer to the block could be fixed in HP Tuners (I have my own HP tuners Pro setup, and a basic understanding of tuning my own vehicle) My other guess was maybe using a thinner headgasket, but again that might introduce VVT issues with the LE5. I think that ordering custom rod lengths would be cost prohibitive, in that it would just be cheaper for me to eat the price on these pistons and buy another set of known replacements from like Wiseco pistons + going with stock sized K1s.
Of course when I purchased these pistons it was on a impulse given how low the price was for the complete piston package, I figured at the time that I'd either have a good set of pistons for less than 50% of their retail value or I'll have some cool paper weights to play with as I buy a different set of pistons for my build.
If it becomes too much of a headache or I later find the compression ratio isn't favorable for my build, I'll just swallow the cost of these pistons and purchase another set to the proper specifications. As of yet I'm unable to figure out the compression ratio, but I'll get to there once I solve the compression height question. I did e-mail the manufacturer of these pistons with as much serial info I could give in the hopes that they will have a back-up copy of the original spec sheet. Hopefully they will get back to me and clear things up, but if not I'm still on step 1 of trying to figure out exactly what I have.
If anyone can advise me with my above issue, or provide me with good accurate details to the LE5 engine specs it would be a massive help.
what's the compression on these pistons?
and reducing the compression height that little won't have too much of a negative effect on compression.
you're talking 0.3mm
unless you're building a race engine, this will be irrelevant to whatever it is that you're doing.
Compression of the pistons are unknown at the moment, if I knew the combustion chamber size of the LE5 head I'd go get some clay and figure out what the pistons are then try to do some math and figure it all out. They look like flat tops to me, but I don't necessarily know if that means they're not lower compression pistons. I'll try to post a pic later.
Because the engine is still in my car and I'm wanting to research and buy up all the parts I need for a build before pulling the motor, I can't just go pull the head off my car right now. I am trying to get my hands on a used head in the very near future, so unless someone knows the cc size of a stock LE5 head I'll have to wait and see till then to figure out the compression. I haven't given a real hard look at compression ratio formulas yet to see if I can derive it given the specs I have now. But the main issue is that I don't have any reliable specs on the LE5 at the moment short of ripping apart my own motor and measuring. I've found a few posts on this forum as well as a couple other ecotec based forums that give the same bore & stroke, rod lengths, but things like total block height, chamber sizes, piston specs other than bore, etc are hard to come by.
I only e-mailed the piston manufacturer ~3pm yesterday so I'm still hopeful that they'll come through with some info for me within the next following days.
Sel wrote:Compression of the pistons are unknown at the moment, if I knew the combustion chamber size of the LE5 head I'd go get some clay and figure out what the pistons are then try to do some math and figure it all out. They look like flat tops to me, but I don't necessarily know if that means they're not lower compression pistons. I'll try to post a pic later.
Because the engine is still in my car and I'm wanting to research and buy up all the parts I need for a build before pulling the motor, I can't just go pull the head off my car right now. I am trying to get my hands on a used head in the very near future, so unless someone knows the cc size of a stock LE5 head I'll have to wait and see till then to figure out the compression. I haven't given a real hard look at compression ratio formulas yet to see if I can derive it given the specs I have now. But the main issue is that I don't have any reliable specs on the LE5 at the moment short of ripping apart my own motor and measuring. I've found a few posts on this forum as well as a couple other ecotec based forums that give the same bore & stroke, rod lengths, but things like total block height, chamber sizes, piston specs other than bore, etc are hard to come by.
I only e-mailed the piston manufacturer ~3pm yesterday so I'm still hopeful that they'll come through with some info for me within the next following days.
the LE5 usually has a slight dome to it with valve reliefs. if your pistons lack this, then I would imagine compression will be a little less than stock.
if they're flat top, I'd be willing to guesstimate you're probably somewhere around 10:1 if not slightly below.
the stock L61 pistons have a tiny dish in them, and they're 10:1... so again, my guess is completely arbitrary.
are you building for boost? if so, I think flat tops will be ok for medium boost pressures (15psi and below) anything more, and I think you're going to run into detonation issues from heat
flat tops have no sharp edges that tend to become hotspots, so that's working in your favor.
This is one of the actual pistons from my set, and that's the only info I have to go by on identifying them so far. The pistons have that 15837 # on the bottom as well so I'm hoping that's some sort of order form # or job number that Diamond will be able to look up and e-mail me or mail me a new spec sheet. I've seen some other Diamond Racing custom pistons come with very detailed spec sheets and some installation guidelines before.
There is a slight dip in the top of the piston, I think you can make it out on the picture. It's very slight and then it starts to bubble back up towards the center but it never reaches the same height as the outer edges of the piston again. I don't have the proper measuring tools with me right now to give exact specs but I think you can see what I'm saying it in the picture.
Sorry about the double post I don't know how to edit posts yet.
But to answer your other question, yes I'm planning to build for boost. It's just a street car though, I'm probably going to end up over building it for whatever the end numbers turn out to be. Right now it's a 07 2.4L LE5 Solstice running a 16g turbo off a log manifold doing 8 psi with 60lb injections tuned with HP tuners by myself. I have a tubular manifold and a Garrett GT3076R ball bearing turbo and a Spec 3+ clutch & flywheel kit sitting on a shelf, along with with a few other miscellaneous mods waiting for me to drop them in the car.
My absolute end goal is anywhere from 400-500BHP, which I think the stock motor with some valve train upgrades and a spot on tune could do without internals. But because the car is run as a daily driver when it's not sitting waiting on parts, I want to overbuild it so it's reliable. The car also serves as a bit of a hobby and educational tool for me, I don't know anyone who owns a shop or anything like that so pretty much all my backyard mechanic-ing I learn from books, the web, and tooling around on my cars. Right now my goal is to build an engine for the car myself except for the balancing, honing, and any other machine work I'd have to outsource.
Right now what I'm thinking is, if I can get these pistons to fit into the equation. I'll get some K1 rods, Supertech valvesprings, and I have a line on some sleeves for the LE5 that I'd have put in as well.
I think those pistons will be fine.
you're prolly looking at anywhere between 9-9.5:1 compression in my guesstimate.
stock LE5 pistons do dome just a tiny tiny bit. these have a dish, so def gonna be less than 10:1
DaFlyinSkwirl (Pj) wrote:I think those pistons will be fine.
you're prolly looking at anywhere between 9-9.5:1 compression in my guesstimate.
stock LE5 pistons do dome just a tiny tiny bit. these have a dish, so def gonna be less than 10:1
Thanks for all the help and info
The more I research my possible build the more I see that the Gen2 block might not be able to handle the sort of power I want to make very reliably. I'm thinking about getting a filled in block (ZZP/FMSR) with the new upgraded sleeves or possibly the just the Gen III block if it's compatible with the LE5 head and e67 PCM. Of course I never intended on buying a whole new block originally. However, I guess if it's gonna get done I want to do it right. I've owned the car since new so waiting another 6 months - 1 year to learn about engine building and the intricacies of our Ecotecs before trying to assemble something is going to be worth the wait for me.
I think when I get my time off in August I'm going to upgrade the valvetrain on the existing engine. I already acquired a spare head which I'm going to give a mild port and polish, I got ARP bolts, and I'm going to be ordering Supertech springs soon. I'm not sure if I should get the valves as well or just stick with stock.
I'm also looking into optimizing the quench for my current boosted setup on the stock bottom end. I'm finding a lot of conflicting information out there about how thicker head gaskets effect quench on boosted motors, some people say it's critical to stay in the .040 or under zone and that 0.050-0.060+ will introduce more detonation even with the reduce CR compared to going higher CR with better quench. Then there are people claiming they run in the 0.070 zone no problems, and there are a few factory applications like the SRT-4 which has the pistons ~1/4 inch deep into the cylinder at TDC. Unless I can find any good documentation explaining if it's safe to drop say half a point in CR ~(10.4:1 to 10:1) with a mildly thicker gasket I'll probably stay stock sizes. Just feels like a lot of work for just doing ARP headstuds, considering I could do most if not all the valvetrain work with the head still in the car.
If you got any good engine building or boosting book recommendations let me know. I've checked out a couple of books but like 95% of the material I find out there is related to SBCs,while most if not all the technical info should translate over there's very little good literature (at least that I could find) about dealing with these smaller I4s. I'm trying to get my hands on a copy of "Forced Induction Performance Tuning A Practical Guide to Supercharging and Turbocharging" by A. Graham Bell but it's out of print and the few copies I can find online are in the $300+ range.
