9:1 compression vs. 8.5:1 on a big 16G Pros/Cons?

[Spoolin4Ever]

So what's up shogun? What you gonna do?

 

[steel_3d]

Here's a little info to show that compression basically gains you power everywhere in the power band (assuming you're not knock limited). I ran a simulation on the same engine, first with 7.8:1 and then 11:1. Comparing 8.5 to 9 was the same trend, but the difference was less than 10lbft on the whole curve.

<a href="http://i6.tinypic.com/1zcmtmv.gif">Graph</a>

 

[Spoolin4Ever]

Here's a little info to show that compression basically gains you power everywhere in the power band (assuming you're not knock limited). I ran a simulation on the same engine, first with 7.8:1 and then 11:1. Comparing 8.5 to 9 was the same trend, but the difference was less than 10lbft on the whole curve.

<a href="http://i6.tinypic.com/1zcmtmv.gif">Graph</a>

I thought these engines are 1997 CC in size?

 

[steel_3d]

Sorry, I was using a 40-over setup in my earlier simulations (86mm bore, stock is 85mm), and I left it that way for this test. Doesn't matter in this case, the only thing I varied was the compression between the two graphs.

Btw you can only put so much faith in simulations, I just thought it was an interesting little tidbit to share. The absolute numbers mean nothing. Just wanted to show that raising the compression gives a constant torque gain across the range, which translates to a linearly increasing hp gain.

 

[Turbo Shogun]

So what's up shogun? What you gonna do?

Wow, I thought this thread had died. Once again, thanks for the helpful advice and insight.

Sorry guys, I've been working my yellow ass OFF, so I haven't been on here much ... There was a point in time a few weeks back where I actually put the car up for sale. WTF ... Basically I was tired of the car and was ready to step up to a used '03 Evo GS-R.

But, long story short, I couldn't afford it and now I'm back to getting my car running again. I test drove a brand new Evo IX GS-R, and I wasn't that impressed. Asuka (my car) and I can be faster around a road course/auto-x.

The head that munched up one of my valves was sent to the machine shop to be repaired. Getting that back tomorrow. Check my posts to see before pics barf of it. I was actually pleasantly surprised that they were able to fix it.

Well, anyway, I've been mulling over the idea in my head and I'm probably going to go with 9:1 on about 18-20 Psi, as stated earlier.

I was slated to get a set of Eagle H-Beam's for a seriously low price, but the US Postal Service decided to lose the package. Chalk another one up for my little bad luck spree with this car.

So now, onto another question.

Stock rods ... Does anyone think they can handle Wiseco 9:1's in +.020? I went onto JAM's website and their Wiseco 9:1 set states that they're designed to run 1G Big rods. I had spoken to Mitch at EnginTecs and he was confident they would hold up, considering my power goals.

 

[Turbo Shogun]

I know what you mean, trust me, my fears are there ...

I came across this thread, however ... Seems like the 1G rods are quite capable. Read the last post on the first page, then most of the second.

I suppose it all depends on the tuning ... But I, too, have had people tell me they're making 400++ on the stock 1G rods and 2G pistons.

But will it hold up to 9:1?

 

[Turbo Shogun]

Well, to tell you the truth, reconditioning, shotpeening and full-floating my set of rods costs $200 or so. Eagle's can be had for $300, so for $100 more, I can get peace of mind, but is it really worth it?

 

[steel_3d]

Depends who you trust more. The machinists in china, or your local machinist? They can both #### up, and out of spec rods will kill you faster than anything. The only way to be safe is to measure everything yourself. My eagle rods were right in spec, so in that case the $100 is worth it.

On the other hand I still paid a machine shop a bit to check the rods (big end diameter, roundness, taper, twist), since I didn't have the tools to measure that small. And the small ends needed to be honed out for the correct pin clearance (I think I specified ~.0007"), which also costs money. I think this needs to be done on all Eagles, some of mine were actually intereference fit with the Wiseco pins.

You'll need to factor these things into the total price, and the Eagles probably cost about 400 with machine work. But they're nice rods when it's all said and done. I wouldn't use stock rods. You could find out about the Scats. People trust their machining more, and if they don't need to be pin fit, you save money.

 

[Turbo Shogun]

That's what I've heard, too. I've read some of the grief that Eagles have caused.

I was never aware of the extra machining needed to fit them, however.

I know I'm being a bit indecisive, but I've changed my mind yet again. I'm probably just going to recondition my stock rods and bore them out to run brand new 2G pistons and rings.

The block? I guess we'll see what happens ... I've been taking enough s*it from my parents about my car sitting for too long.

Long story short, I guess we'll find out another day ... Thanks for the advice, though. Next time I will go with 9:1.

 

[JOEY A]

That's what I've heard, too. I've read some of the grief that Eagles have caused.

I was never aware of the extra machining needed to fit them, however.

I know I'm being a bit indecisive, but I've changed my mind yet again. I'm probably just going to recondition my stock rods and bore them out to run brand new 2G pistons and rings.

The block? I guess we'll see what happens ... I've been taking enough s*it from my parents about my car sitting for too long.

Long story short, I guess we'll find out another day ... Thanks for the advice, though. Next time I will go with 9:1.

You could go with EVO8 pistons they are high compresion and better than 2G pistons, 1g big rods with evo8s would be the best budget build.

 

[Turbo Shogun]

Aren't those 8.8:1? I haven't seen them for sale anywhere. Maybe I just haven't been looking hard enough.

 

[steel_3d]

word from the wise, keep the timing up on those rods, 16* is probably the lowest I'd ever go on cast ever again.

Why?

 

[andymoraitis]

Less timing creates more heat in the motor. I would think that around 14 degrees is the limit on cast/stock rods, but I currently run my forged rods at 12 degrees all day every day.

 

[Turbo Shogun]

Oho, it seems I have changed my mind once again.

I recently scored a set of JE 9:1s in +020 and a set of Crower rods for DIRT cheap. So it seems like I will be going high-comp after all.

Motor comes out tomorrow (finally). Hopefully I can bring it over to the machine shop to punch the bores out for the pistons.

When I had my car running I was seeing around 16-17-18* of timing advance at WOT around 5k~limiter.

So I'm going to have to retard timing a few degrees to run 9:1?

I really plan on taking the car to AMS to get tuned as soon as it's broken in (or not?), so I guess I can let them handle it, but more light shed into this would be greatly appreciated.

 

[nightspeed87]

Im doing a 6bolt swap, with stock 6bolt long rods, and Im going to use used 2g pistons I bought, and I currently still have a 14b and plan on running about 16lbs... Does anyone see any danger in this set up with stock timing and etc. ( doubtful but just to be sure )
I have a afpr and a 190lph hp and base fuel pressure raised slightly but never touched the 450s yet.

 

[steel_3d]

Nightspeed, as long as you watch your knock on a logger, and are able to tune it out, you'll be fine.

Shogun, from what I've heard JE's are prone to piston slap. I'd research them well and go with the piston to wall clearance that best suits your application. Too tight and the pistons might scuff or seize from heat expansion at high power levels (if that's your goal). Too loose and they'll slap.

 

[Turbo Shogun]

You know what, I was just thinking about piston-to-wall clearancing.

Sounds like something the manufacturer would know best. Maybe I should give them a call/e-mail.

And no, I still plan on making 350 AWHP max. I know it's overkill, but hell, reconditioned/peened/fullfloated stock rods and a set of Wisecos would have run me $660.

 

[nightspeed87]

Nightspeed, as long as you watch your knock on a logger, and are able to tune it out, you'll be fine.

Shogun, from what I've heard JE's are prone to piston slap. I'd research them well and go with the piston to wall clearance that best suits your application. Too tight and the pistons might scuff or seize from heat expansion at high power levels (if that's your goal). Too loose and they'll slap.

may sound like a basic question but
if I put used 2g pistons in my car do I have to have the engine rebored
for them, or will they fit snug since theyre used pistons going in a used engine?
And I doubt 2g pistons are different circumference than 1g pistons, but Just curious.

 

[Turbo Shogun]

2G pistons fit the same bore as 1G six-bolt blocks.

I don't think you'll have to bore them, as such. You will however, have to have 1G big rods machined on the pin end to fit them, but I'm sure you already knew that, and/or you're going with different rods.

I hope your pistons are in good condition. I got ripped off on a set of used 2Gs from a large online used parts store.

Anywho.

What's this I hear about JE pistons being prone to slapping ... ? I've read a few threads and it seems to be a recurring occurence. Does anyone know the cause? I read one thread that simply placed the blame on the lack of competency of the machinist boring the cylinders out. Makes sense to me, unless there's something in JE's design that makes them that much more prone to piston slap than say, Wisecos or Arias. I hear that if everything's done right, there's no slap on forged pistons even when cold/startup.

Well, that seems like another thread subject in itself. Hopefully someone can debunk this ...

 

[nightspeed87]

2G pistons fit the same bore as 1G six-bolt blocks.

I don't think you'll have to bore them, as such. You will however, have to have 1G big rods machined on the pin end to fit them, but I'm sure you already knew that, and/or you're going with different rods.

I hope your pistons are in good condition. I got ripped off on a set of used 2Gs from a large online used parts store.

Anywho.

What's this I hear about JE pistons being prone to slapping ... ? I've read a few threads and it seems to be a recurring occurence. Does anyone know the cause? I read one thread that simply placed the blame on the lack of competency of the machinist boring the cylinders out. Makes sense to me, unless there's something in JE's design that makes them that much more prone to piston slap than say, Wisecos or Arias. I hear that if everything's done right, there's no slap on forged pistons even when cold/startup.

Well, that seems like another thread subject in itself. Hopefully someone can debunk this ...

( Im buying the 2g pistons off of someone in the classifies on this site and they seem like there ok, at least I hope so... How can I tell the condition other than the obvious, is there anything I should look for once I get them that will help state the condition .. )

And I hear with those aftermarket pistons, they expand more under high heat ( high hp ) engines and thats why they slap, because they fit snug before they expand and then afterwards they get expand and scuff the walls or whatever.... Look into that because I think im on the right track, with that, read it in a performance book somewhere. ( so make sure you get the right material/ strength piston if your going to spend all the money on aftermarkets.)

 

[steel_3d]

The difference between JE's and Wisecos for example is the aluminum alloy they use. JE uses the higher strength 2618 alloy, that also happens to have higher heat expansion characteristics.

http://www.dsmtuners.com/forums/showthread.php?t=218905

I know Wiseco uses an offset pin to combat piston slap, I don't know if JE designs anything like that into their pistons.

Since you're not going for crazy hp you should be ok with tigher clearances that will avoid slap. But if you ever get happy and give it a good shot of NOS or really high boost, it might seize up on you. As I said, keep reading. I don't know the magic number for JE's, but somebody might.

And ultimately it all depends on whether your machinist actually gives you the clearace you ask for. I would do the measuring myself, or at least have him measure it in front of me. Especially for something as finicky as JE's.

 

[Turbo Shogun]

I've read and digested about 5 threads' worth of dirt on the JE's. And it doesn't look good. Seems like they're pretty much a race-only piston. I have read of one instance where they worked (and I honestly don't remember where I found it)

My question is ... How can such a renowned piston manufacturer f'up on pistons for our cars? It seems mind boggling that they'd half-ass their R&D for something as popular as DSMs, yet have a very good reputation among the domestic crowd.

I don't know if I will run these or not. I might end up selling them for hella cheap so I can recoup some money for a set of Wisecos.

I really want to hear from the people who've used these successfully in a fully street-tuned DSM.

As I stated before, I'm not going nuts with this setup. I'm really only going to go with what I can handle, so I figure 350 AWHP will be good.

 

[groundPork]

The difference between JE's and Wisecos for example is the aluminum alloy they use. JE uses the higher strength 2618 alloy, that also happens to have higher heat expansion characteristics.

http://www.dsmtuners.com/forums/showthread.php?t=218905

I know Wiseco uses an offset pin to combat piston slap, I don't know if JE designs anything like that into their pistons.

Since you're not going for crazy hp you should be ok with tigher clearances that will avoid slap. But if you ever get happy and give it a good shot of NOS or really high boost, it might seize up on you. As I said, keep reading. I don't know the magic number for JE's, but somebody might.

And ultimately it all depends on whether your machinist actually gives you the clearace you ask for. I would do the measuring myself, or at least have him measure it in front of me. Especially for something as finicky as JE's.

To my knowledge all 4g63 pistons from competing companiies are made of teh same material alloy. Would not make much sence to sell a piston to a bunch of boost crazy DSM guys that could potentially shatter at the onset of detonation (ie... 4032 high silicone). I know wiseco used to offer only 4032 for their sport compact line, but quickly switched to 2618 early in thier game ( I think for both ease of productioon and for it's stregth). Two things that can prevent the audible piston slap are offset pins and smaller skirt contact patches (for lack of better terms). Other than that... The engine desing itslef has more to do with that minor inconvenience than anythiing esle. Thiin wall cylinder V8's with large vallies under the intake manifolds are especially noisy at piston to wall clearances any largeeeer than .003" and that on a heavily boosted engine! Thing is they have alumin. blocks, with very little iroon, and they expand with the pistons. Cast iron blocks don't. So the pistonnn want to grow, but the hole doesn't want to increase in diameter, thus the piston siezes.

Let's not be a bunch of EVO owners guys... Let's measure, lets, ask questions, lets, think before assembly! Let's try not to jump to conclusions.... We gernally don't have tons of money to throw around, so lets make the most of it.

Yes JE should be contacted for recomended bore clearance, ring end gap, and bore finish...

 

[groundPork]

insidently, I still think 9:1 kicks ass oriface...

 

[WRX19]

insidently, I still think 9:1 kicks ass oriface...

I agree...It's an awesome setup!!