Best compression ratio for my goals?

[Talyn]

I am currently doing a rebuild, and was planning to reuse my ross pistons with a CR of 8.3:1, however I noticed after pulling them that at some point they kissed the valves(Didn't happen when I owned the car), while they appear to be ok, and didn't give me any problems, I have also discovered that ross no longer has rings for these, and I would have to special order them for $180 and change.

Leaving me to contemplate if I should just get new pistons, especially when I consider that with my plans to switch to e85, I might be better off with a higher compression ratio. I'm not looking for opinions on whether or not to junk my pistons, I'll decide that for myself.

I would like to know peoples thoughts on what compression ratio would be ideal for a goal of 450-600 WHP on e85 street build, basically going for a hardcore street build. And how much difference does CR really make? I know a higher CR will make more power off boost, respond better, and spool the turbocharger quicker, as well as put me closer to detonation, but how much difference is there really between the available CRs of: 8.3, 8.5, 9.0 or 10.0 CR?

 

[BogusSVO]

Funny thing, seems I have that same Ross pistons in my shop, I just had to order the custom rings for them.

Ross had used rings made by ACL rings, and ACL rings have closed down. Now they have to sorce rings from another supplier and have them modified to fit the older Ross rings, running the price of the ring set up.

Now about your question about compression and E85. Read this thread

http://www.dsmtuners.com/forums/cyl...some-more-knowledge-building-short-block.html

I think you will find the info you want.

 

[Talyn]

From what the guy on the phone said, I think ACL got bought out by Mahle or something, and now I think they are sourcing them from Sealed power, and none of the other piston companies that make pistons for our cars seem to use 1.5, 1.5 and 3mm rings. As I looked into just buying a set of off the shelf rings from a different company.

I read through that thread you linked, seems pretty clear that higher CR is the way to go with corn, although I do find myself questioning this:
"With the higher compression we always recommend an billet rod. The h-beams just aren't up to the task. Piston wise it's Wiseco HD, Venolia or Manley Platinum Series" The pistons are ok, because the set I had in mind was the 10.0:1 Manley platinums, but are billet rods really necessary? I currently have eagle H-beams and they are rated for 1k horsepower if I remember-Well above my goal of 450-600 whp, which is probably about 550-700 crank.

 

[JacksonAuto]

I read through that thread you linked, seems pretty clear that higher CR is the way to go with corn, although I do find myself questioning this:
"With the higher compression we always recommend an billet rod. The h-beams just aren't up to the task. Piston wise it's Wiseco HD, Venolia or Manley Platinum Series" The pistons are ok, because the set I had in mind was the 10.0:1 Manley platinums, but are billet rods really necessary? I currently have eagle H-beams and they are rated for 1k horsepower if I remember-Well above my goal of 450-600 whp, which is probably about 550-700 crank.

It was me that said that. Billet rods handle the higher cylinder pressures much better over time. An engine with higher CR will run with H-beams but they will reach their fatigue point much faster. The h-beams are rated for between 600 and 650WHP not 1000. HP limits of components are very generalized and there are a lot more factors that have to be taken into consideration. In this case, cylinder pressure is going to be the limiting factor of the rods and not necessarily WHP.

 

[Cdc1221]

Why not just get the ring grooves recut on the Ross' for a different style of ring and save your dinero for a bigger set of injectors?

 

[rhamlinii]

Why not just get the ring grooves recut on the Ross' for a different style of ring and save your dinero for a bigger set of injectors?

Ive ran 10.5 to one motor to 7.5 to one motors. I will tell you to stay where you are and make power with boost and fuel.

 

[Talyn]

It was me that said that. Billet rods handle the higher cylinder pressures much better over time. An engine with higher CR will run with H-beams but they will reach their fatigue point much faster. The h-beams are rated for between 600 and 650WHP not 1000. HP limits of components are very generalized and there are a lot more factors that have to be taken into consideration. In this case, cylinder pressure is going to be the limiting factor of the rods and not necessarily WHP.

Duly noted, I was discussing it a little bit with a colleague at work, and correct me if I am wrong, but cylinder pressure would be the CR multiplied by the absolute pressure of the intake air, ie. atmospheric of 14.7+boost, in which case with 20 psi(about what my 20g will be running for now) it would be 347 psi cylinder pressure with 10.0:1 pistons, which he didn't think the engine would hold for long.

In any case, I've decided to stick with what I have for now at least, its not like I couldn't still switch to e85 on 8.3 pistons, just might not be quite as ideal, though I imagine really high boost #s would be attainable. I would consider spending an extra ~$300 for pistons, but I am afraid to even check how much billet rods would cost.
Also, I know other sites list them as rated for 600+ or 650 or so, but straight off of Eagle's website they claim a rating of 1000hp.
Eagle Specialty Products, Inc.

 

[LandSpeed-DSM]

Duly noted, I was discussing it a little bit with a colleague at work, and correct me if I am wrong, but cylinder pressure would be the CR multiplied by the absolute pressure of the intake air, ie. atmospheric of 14.7+boost, in which case with 20 psi(about what my 20g will be running for now) it would be 347 psi cylinder pressure with 10.0:1 pistons, which he didn't think the engine would hold for long.

In any case, I've decided to stick with what I have for now at least, its not like I couldn't still switch to e85 on 8.3 pistons, just might not be quite as ideal, though I imagine really high boost #s would be attainable. I would consider spending an extra ~$300 for pistons, but I am afraid to even check how much billet rods would cost.
Also, I know other sites list them as rated for 600+ or 650 or so, but straight off of Eagle's website they claim a rating of 1000hp.
Eagle Specialty Products, Inc.

Your colleague is forgetting about the "explosion" part of the cylinder pressure equation he has invented.

 

[lowell]

We don't have E85 here, but I run a 10.3:1 2.0 on 94oct and meth injection. Hands down winner everywhere, and I've run 7.8, 8.5 and 9:1 before.