I came across a freshly rebuilt B18B shortblock (still in the plastic bag)
with Eagle rods, SRP forged pistons, TypeR oil pump and STR block guard -9.75 to 1 comp(81.5mm bore) I was curious as to whether or not this was too high of compression for a daily driver? I was planning on buying on just rebuilding my motor with 9.5:1 pistons but I like the Idea of having a spare shortblock and not having to have the downtime of sending mine out to get bored and assembled. Also I think its a good deal though for 900 bucks. Any help would be appreciated.

 

srp arent good over about 14psi safely, they are made with more silicon content. JE will even tell you this. as far as compression, it just makes the tuning a little trickier i guess. i was thinking of running 9.5:1 ls vtec turbo, which i prolly still am.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SP00LIN &raquo;</TD></TR><TR><TD CLASS="quote">srp arent good over about 14psi safely, they are made with more silicon content. </TD></TR></TABLE>

First I have heard of this. More info please. I don't see how a "XXpsi." safety window could be put on them.


Drew,

You may actually be happier w/ the higher compression. IMO, "safety" is put in the tuners hands.

Phil

 

Thanks for the help. I have heard things bad things about srp pistons. But when I came across this I thought it might not be such a bad set-up.

 

I am not doubting him or you. I am have just not heard any bad things before so, I am curious.

Phil

 

cool thanks, yeah Im still tempted to buy it because it might be a good set up. 900 seems like a pretty fair price.

 

9:5:1
I am running that comp on my gsr turbo, I think that 9.75 should be okay, as for the pistons, thats something I dont know about.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kevino002 &raquo;</TD></TR><TR><TD CLASS="quote">9:5:1
I am running that comp on my gsr turbo, I think that 9.75 should be okay, as for the pistons, thats something I dont know about.</TD></TR></TABLE>

9.5:1 on a VTEC head is a far cry from 9.75:1 on an LS head. Your head flows much better, so you make more power at less boost. What you make at 8 psi it might take him 14 psi. I don't know about you, but with a completely built motor I personally would be looking for more than around 300 WHP on pump gas, which is what I feel you'll (realisticly) be limited to on that high of compression with an LS head.

And FWIW, I don't buy any of the stuff about SRP's being bad for a moderate boost setup. Turbo Buick's run a hypereutectic piston stock, which is weaker than any forging, and they run 14 pounds of boost from the factory, and many people push them a lot harder than that. For a full out 30+ psi race motor I would look into something else, but I would be totally comfortable running them in nearly any street motor.

 

thats what I was thinking. They have to be better than stock LS pistons and people boost that. Im not trying to make serious power, 12-14 pounds would probably be the most I would ever run.

 

I had a set of srp's that were 9:8:1 compression in my ls/vtec , and they were fine above 14 pounds.I ended up selling the block to my buddy and he ran 18 psi on it with stock sleeves and it held up good.I would say your compression will be fine and it will help the turbo spool up a little faster

 

thanks for the info, so far it looks like I might go ahead and pick it up.

 

So You guys think it's a good buy?

 

the srp's are designed more for all motor/light turbo setup. i called JE which makes SRP, like 5 times trying to decide on a piston...i told him ill be running 20 psi...he said i should definatly go with the JE. im sure they will handle a fair amount of force being forged...but its not their main purpose.

 

What is your octane available?

 

should be ok i run 10:1 on my ls and the actual compression of the motor (tested at te machine shop) is 10.28:1

 

93 octane

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by per4mance &raquo;</TD></TR><TR><TD CLASS="quote">I would say your compression will be fine and it will help the turbo spool up a little faster </TD></TR></TABLE>

Too bad it doesn't.

http://www.boosted-hybrid.com/viewtopic.php?t=1612

Spool up = exactly the same between 9:1 and 10:1

 

I would go with lower compression. Like 8.5:1. With a turbo motor you see hardly any benefit from moving up a point or two in compression. But you'll probably detonate before mbtt on a higher compression motor, where as you probably wouldnt with a low compression

 

man, 8.5 is grandmother compression.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boltz &raquo;</TD></TR><TR><TD CLASS="quote">I would go with lower compression. Like 8.5:1. With a turbo motor you see hardly any benefit from moving up a point or two in compression. But you'll probably detonate before mbtt on a higher compression motor, where as you probably wouldnt with a low compression</TD></TR></TABLE>


Less efficient, the drop from 10:1 loss 15 whp.

 

Now Im not sure what I'm gonna do. It sounds like the brand of piston is more of an issue than the compression.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DrewDown &raquo;</TD></TR><TR><TD CLASS="quote">Now Im not sure what I'm gonna do. It sounds like the brand of piston is more of an issue than the compression.</TD></TR></TABLE>

No!. There are lots of good pistons around. You shouldnt be so worried about finding a quality piston that you completely disregard CR.

I reccomend Wiseco or CP.

You will be able to push more power on pump gas with lower compression. You wont be able to tell the difference in spool if you lower/bump the compression a point or so, so pick a good sized turbo for the motor and you're set. High CR is for N/A motors, Low CR is for boosted applications so you can boost a lot on pump

Go with 9:1 at the highest. I would go closer to 8-8.5 to boost the **** out of it.

If you listen to this, you wont be dissapointed by CR later, I promise.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MidShipCivic &raquo;</TD></TR><TR><TD CLASS="quote">


Less efficient, the drop from 10:1 loss 15 whp.</TD></TR></TABLE>

You might see a 15whp drop from going from 10:1 &gt; 8.5:1, but there are so many variables involved you cannot just claim 15whp lost, sure its ballpark, but its not official.

Again, you might see a 15 whp drop from the compression loss, BUT that is at the same boost level. Instead of say boosting 14psi on the 10:1 motor, you push 18psi on the same motor at 8.5:1 and say goodbye to your 15whp loss

 

Let's not get into a compression argument here. A built LS motor for $900, heck yes that's a good deal.

 

I meant that with this setup I was looking to buy, because it already has the SRP pistons installed in the shortblock.

 

no its good but i wouldnt run high boost on srp's the higher the compression the faster it will spool the turbo but a less margin for error on tuning. lower compression will let you use less octance gas.