Zick

iTrader: (18)

Ok, I'm a little confused here because everything I've read and been told was this combo should not be able to run on reg 87*.

Here is my engine setup;
05' LQ9 (ARP mains & Katech Rods)
Patriot lvl 1 243's (64CC)
Cometic .040" gaskets
TR230/224
Exhaust system is completly stock

I ran all the numbers and it came out to about 11.5 CR and about 8.5 DCR. For the longest time I've been running on 93* without a problem but wanted to see how bad 87* was and to my surprise it ran just fine, maybe even a little smoother.

The most I could pull from 93* was about 25* timing. Right now I'm at 22* running 87* with no detonation.

Billdog350

iTrader: (3)

I'm far from an expert but I thought the 64cc heads only gave you 10.8-11.0 SCR on an LS1 motor...not sure how different the LQ9's are but I think they're the same. That would explain your ability to run 87, since you'd be closer to 8:1 DCR.

Zick

iTrader: (18)

With the 64cc heads that will bump it up to 11:1 roughly using stock head gaskets, but I'm using .040". This is what I got running a CR calculator.

Also the DCR is changed now do to the cam, which running a DCR calculator I got 8.5.
This is possible where I made a mistake. I was told the deck height on a LQ9 should be -.007-.008 which put the DCR at 8.5. But if I put in a positive .007 it will come out to 8.1 DCR.

prplhaz

Does the LQ9 have flat top pistons (not dished or have valve reliefs)?

Zick

iTrader: (18)

Flat top, no dish and no valve reliefs.

Nate_Taufer

iTrader: (1)

LQ9 has flat tops...the LQ4 has dished pistons.

Nate

Zick

iTrader: (18)

bump.

GuitsBoy

iTrader: (4)

bigger cubes tend to be able to handle higher compression. Partially this is due to the lower DCR of a bigger cam, but i feel it goes further than that. More cubes just take more compression.

PREDATOR-Z

Try to bump up the timing to what it was on 93 Octane and see what happens

You lowered octane and lowered advance, so why wouldn't it work?

N4cer

iTrader: (11)

My thoughts exactly.

Zick

iTrader: (18)

I understand that I lowered the octane and lowered the timing(only by 3*). What I'd like to know is whether or not my figures are wrong or why is everyone saying that you have to run at least 93 octane if your DCR is 8.5+?

N4cer

iTrader: (11)

We mean to get maximum performance. You can run more timing at higher compression with more octane.

allngn_c5

iTrader: (3)

Did you do this so you wouldn't have to pay for premium fuel?? Anyways as long as you are happy that's all that matters.

Zick

iTrader: (18)

Not really, it was just a test. I read, searched and read more before building this engine to this level to make sure I could manage running on premium fuel and basically everything and everyone said that 8.5DCR was the limit on pump gas. But now that doesn't seem to be the case unless like I said maybe my figures are wrong but nobody has corrected them yet.