So it's speced to be 11 CR with the gasket then.
I had the builder spec everything off of the reported CR based off of the stock head gaskets compressed height of .039/.040.
Yes, for sure. Another rule of thumb is each compression number changes borderline by 4 deg, so dropping from 12 to 10.5 would allow approximately 6 deg more timing at the threshold of knock.
Lower CR can reduce low-end torque with a centrif setup and off-boost torque with a turbo, but with a PD blower it's a myth. However, you need to offset the loss in torque with an increase in boost, but the end result is safer and more powerful.
I thought this as well but later learned that all of the knock variation I was seeing was actually due to changes in ambient humidity. Humidity can change knock-limited spark advance by 2-3 deg. GM and Mercury Marine actually measure and account for it. I've done similar on my own setup and almost never see knock on true 93, while running up to 19 deg timing on the 3.25" whipple pulley.
Lower CR does increase EGT, but also consider the EGT effects of overly retarded spark timing. A 12/1 engine running 14 deg timing vs a 9.5/1 engine running 24 deg timing might break even or worse.
Upgraded from the stock Predator pistons? I really like OEM-quality forged pistons and those have proven to be insanely tough. I do think the CR was a bit low, but I don't see any good options for raising it a tad. I used to have a stock Gen3 short block that I would have kept and upgraded to 10.4/1 and just never built the Predator if I could do-over.
Yes, basically 100% stock gen3 heads and valvetrain on a stock Predator short block with slightly opened up ring gaps, Predator oil pan and pump ass'y.
The MAF only has the capability to measure mass flow but not humidity. Ford tinkered with measuring ambient humidity using the UEGO during DFCO, but I don't think they ever implemented it. I am told that there is code there to account for humidity but it's turned off. I did find a university research project that appeared to be sponsored by Ford where they ultimately concluded that the octane-adaptive strategy can also account for humidity. But there's a lot more to that story once you start adding boost to a stock 12/1 engine.
I hear ya' and I'm not going to argue. But I have over 800 logs, the vast majority of which are on 93. The only time I had knock that I couldn't otherwise account for wound up being caused by low humidity.
Manual car? I didn't know if it (pred oil panf) would interfere with any manual or the 10R80 we left it out of the parts bin and just did gears for the pump and a normal gen 3 pan
@engineermike
Probably get that 10.4:1 CR piston in M142PHere is a reply from Mahle. I asked Iād like to know the limits of the 3 alloys and when would you recommend 2618 over 4032 or M142p.
Yes for sure. Pcmtec actually has the table defined that relates egt to timing and lambda.
Most people don't, it is on the start up that you will hear it the most. The DI on the Gen 3 is extremely loud especially when those little foam isolators are removed.
Ive been looking more into this and from what I can see all mahle 12:1 pistons for the 5.0 appear to be 2618, cant find anything saying the gen 3 aluminator has 4032 pistons
