Did I make a mistake

[Aproductions]

So for my engine build most people told me to go with 9:1 pistons over 8.5:1
It will see only street, as it is a summer car.

I went along with it and now suddenly I'm thinking maybe it was the wrong move.

I'm getting a Holset H1C and I heard they don't get aggressive until like 25psi.

with the 9:1 pistons I should only run like 20psi on 93oct, correct?

Someone talk me through this and make me believe I did the right thing.


would I want 9:1 with 20psi or 8.5:1 with 25?

 

[kidtsi]

So for my engine build most people told me to go with 9:1 pistons over 8.5:1
It will see only street, as it is a summer car.

I went along with it and now suddenly I'm thinking maybe it was the wrong move.

I'm getting a Holset H1C and I heard they don't get aggressive until like 25psi.

with the 9:1 pistons I should only run like 20psi on 93oct, correct?

Someone talk me through this and make me believe I did the right thing.


would I want 9:1 with 20psi or 8.5:1 with 25?

i dont think you live in a place that is hot like where i live. if u cant reach 25psi on 9:1 without knock use meth injection but i think 8.5:1 is better but if it is a street car 9:1 is more torqui so yeah.

 

[Calan]

I went along with it and now suddenly I'm thinking maybe it was the wrong move.

Is the engine already built?

 

[Aproductions]

no but i bought 9:1 already

 

[1997_GSX]

I am running 10:1 in my dd on pump 93 and meth injection. With the nozzle for the meth put in bass akwards not flowing what it should, I ran 34 psi and 8 degrees of timing.


I added a second nozzle and speed density still gotta get the car tuned but I am hoping for some way higher numbers.

You can look at my mods in my profile.

 

[Calan]

Well if you can't get e85 or don't want to go with meth, it will be a little harder to run higher boost levels...but not impossible. You may have to drop the timing though.

The main difference is going to be the torque produced during off-boost. Once you start adding boost, cylinder pressure is cylinder pressure... for the most part. If it's too high or too hot for whatever reason, you're going to knock and have to tune it out.

If you can return the pistons and swap them out without losing money, go for it. Otherwise, I wouldn't over-analyze it and sweat it too much. There are plenty of people running high CR motors with good results.

FWIW, I can hit 28 psi on 91 frog piss with 8.8:1 slugs in a stroker and an e3 16g that is way cooked at that point...but I have to use some WAI and pull a lot of timing (which is normal for a stroker).

 

[Aproductions]

so I can run I good amount of boost and also get meth to help?

after that it will be like 8.5:1 but with better low end?

 

[1997_GSX]

Right. My car with 280 cams, Ported head, 1mm Oversized Valves, JMF Race SMIM, pulls just as well as a stock 8.5:1 with stock cams, head and IM if not better before spool of course.