Custom Lower Compression Pistons

[Diesel JD]

That was Dave Spounagle. He claims to be able to hit 25+ PSI with an ATS turbo and having shaved 40 thou off of some hyperteutic pistons. The intake manifold blew up and he then used copper paste or hylomar and ARP intake studs to keep it on. No further issues the last time we got him on here. Seems like he still got OK fuel mileage for factory gearing, T19 and loaded to the gills every day for work 14mpg sounds alright. There's a thread here where he talks about it. Personally if I could get a set of custom slugs for under about 1200 or 1500 I would do it, instead of modifying pistons not intended for high boost. I think if you have the turbo to push enough air and the lower compression to handle more boost the high EGTs won't be an issue even if you use a Moose or DPS pump or your homebrew version of a HO pump. But hey, that's just theory at this point, maybe somebody will prove its fact or fiction.

 

[flatlander]

I cut .060 off mine. I'm trying to be a little conservative for a little bit. It'd be nice to make it a year without breaking anything.

 

[david85]

That was Dave Spounagle. He claims to be able to hit 25+ PSI with an ATS turbo and having shaved 40 thou off of some hyperteutic pistons. The intake manifold blew up and he then used copper paste or hylomar and ARP intake studs to keep it on. No further issues the last time we got him on here. Seems like he still got OK fuel mileage for factory gearing, T19 and loaded to the gills every day for work 14mpg sounds alright. There's a thread here where he talks about it. Personally if I could get a set of custom slugs for under about 1200 or 1500 I would do it, instead of modifying pistons not intended for high boost. I think if you have the turbo to push enough air and the lower compression to handle more boost the high EGTs won't be an issue even if you use a Moose or DPS pump or your homebrew version of a HO pump. But hey, that's just theory at this point, maybe somebody will prove its fact or fiction.

Thats him alright. But I don't think he used ARP studs on the manifold, just cut grade 8 ready rod. I did the same with mine on the intake and exhaust manifolds since it seemed like a good idea. Probably an overkill in my case, since I would be thrilled to see over 10 psi let alone 20+. Still mulling over the option of replacing the turbocharger compressor side with that nice 60-1 air squisher I found out about

Not a very expencive upgrade, but I keep talking myself out of it. Too many projects already.

 

[Diesel JD]

David I suppose I was wrong about his intake mods. Sounds like what you did was not as hard to do or expensive as ARP. Wonder if you could do something like that for the heads or not? I'm shocked you can't get better than 10 psi out of that non gated turbo. I can hit 6 with mine if I really stand on it now that I have no muffler and 4" from the downpipe back. I guess you still have a stock injection pump? I keep hearing these things can boost till it runs out of fuel or the engine blows up, however you probably have to be driving really fast or really hauling heavy to even spool it much at all with 3.08s. What would you say your CR is with the 20 thou you took off your pistons and any other mods you did?

 

[david85]

David I suppose I was wrong about his intake mods. Sounds like what you did was not as hard to do or expensive as ARP. Wonder if you could do something like that for the heads or not? I'm shocked you can't get better than 10 psi out of that non gated turbo. I can hit 6 with mine if I really stand on it now that I have no muffler and 4" from the downpipe back. I guess you still have a stock injection pump? I keep hearing these things can boost till it runs out of fuel or the engine blows up, however you probably have to be driving really fast or really hauling heavy to even spool it much at all with 3.08s. What would you say your CR is with the 20 thou you took off your pistons and any other mods you did?

Guessing around 21:1 with stock being 22.5:1. Dave S would know, he's always good with numbers above 10 (unlike me ). I think Dave mentioned that he had 20.25:1 with 40 thou off the top, but don't quote me on that. ARP studs are still stronger than grade 8 bolts though, so while grade 8s may be good enough for the manifolds I would be leery of using them for the heads.

The way this turbo is set up it can't really spool that much unless you are already on your way past 2500 RPM. I've seen as high as 14 psi before I rebuilt the engine and that was with the fuel screw maxed out (minus about 1/6th turn to keep from killing the pump) and turning the sky black. Not sure where the fuel setting is now, but its pretty mild. I don't want to turn it up any higher because its already pushing a little smoke at full power at anything below 2500. if I turn the fuel up any higher I want to make sure I can burn it all.

I'm still not sure if a bigger compressor would spool much better at low RPM and thats the other reason I'm hesitant to try it. I don't really care about turbo lag as long as I could get it to spool more pressure below 2000 RPM. I tend to run the RPMs as consistent as possible and throttle up gradually even when I floor it. Dunno, still have some reading to do.

What you have to remember about the ATS turbos is that they were not really intended to boost more than 8 psi even though they can. The idea being that a stock 6.9 can't reliably take much more, at least not in ATS's opinion. The 088 that I have seems to loose efficiency after abour 5 psi. 5 psi comes almost instantly, and then its like pushing through a wall to get the boost any higher. And then the smoke starts to roll on.

 

[Diesel JD]

Dave I think you need a wastegated turbo as you yourself have been saying. Will be interesting to see what REklund's results will be like when he drops the Aurora 2000 in place of the 088. I just don't think the 088 will push boost less than around 2000, mine never has except a little when I have really stomped it or very heavily loaded.

 

[tradergem]

Stud info

Here is some material info for studs from A1 Technologies and ARP.

http://www.a1technologies.com/site3.php?id=271

http://autospeed.com/cms/A_110592/article.html

http://www.arp-bolts.com/Tech/TechMetals.html
Look under quick reference guide.

Hope this is helpful.

Jim

 

[riotwarrior]

One of us needs to do some research. Here's what I'd like done to mine: lowered compression around 18 or 19:1, have the piston pin boss set up to bolt to the factory turbo rods. Hard top or anodized...maybe, maybe not.

In conjunction with the above custom piston design, I would really like to see at least a 3rd compression ring, perhaps a "Total Seal" Zero gap design to help keep that thar boost above the rings where it does the most good!

Maybe not hard top anodized but Ceramic coated top, teflon skirt and there is a under dome coating that helps too, just cannot recall what that was, too many years and too many beers ago.

"O" ringed Teflon Pin buttons would also be great to be absolutely certain that pin stays centered and have no chance for um catastrophe

I dunno bout ya'll but these are some key features that should be explored, I cannot see that "Gas Porting" the piston would be good as it would lead to premature ring / bore wear.

Custom pin oiling could be a benefit by having a small hole from the oil ring that goes to the pin journal in the piston.

One thing I do not know if the connecting rods have a squirter hole in them as in some form of oil jets to lube the thrust side of the piston bore for lube and bottom of the crown to help cool it.

 

[subway]

i think the most important part would be how thick a material do you need to withstand the combustion chamber. if the head of the piston has to be .2 or .3 thick(example number) to be structurally strong enough not to cave wouldn't that dictate how much you can take off?

i am sure there is a way to calculate that according to cylinder pressure, temp, material properties etc..... but i wouldn't know how off hand.

if you are just taking it off you could be skinning your safety factor for survival.

editors not: i haven't built any performance motors so this is just thinking out
loud.

 

[david85]

Dave I think you need a wastegated turbo as you yourself have been saying. Will be interesting to see what REklund's results will be like when he drops the Aurora 2000 in place of the 088. I just don't think the 088 will push boost less than around 2000, mine never has except a little when I have really stomped it or very heavily loaded.

I think you might be right. I have similar results. Cruising in overdrive at 1600 RPM I only can make 2 psi before smoke, lugging and EGTs become a problem. Only paid $200 for the kit nearly complete, so I can't really complain. I'm not sure but I think the 093 kit has the same or at least a similar compressor to the older 088 turbocharger, but the turbine side is from the smaller T3 family on the 093 since its a T3/4 hybrid. The sizing difference forces the compressor to spin faster but also makes for higher EGTs as there is more restriction in that smaller turbine (probably an oversimplification as I'm sure theres more to it than that). My logic is that if I get a larger compressor it wouldn't be much of an investment compared to a new turbo kit and increasing the sizing difference between the turbine and compressor should hopefully force more air into the engine. Being larger overall should also flow better and allow more CFM relative to the amount of EGTs. Thats one thing thats great about the 088 EGTs rarely go above 700 under normal use. Even if I floor it the most I see is around 1000.

But alas, I'm not a turbo guru, so this might all be crap and I have no idea what the results would be. I'm probably going to try it eventually once I get the courage up .

But I am waiting to hear some numbers from the new ATS aurora turbo kits for our engines. Should be interesting to see what improvement there is over older ones, if any.