Max boost is different in different gears?

[Brantley]

After figuring out some problems and getting more fuel (see update in talk), I turned the boost up. 2nd gear builds boost to 22psi and stays there rock solid for the whole duration of the gear. No boost creep or spikes. So, then I shift to 3rd. It holds rock solid at only 20psi, no creep or surge. What causes one gear to be 2psi higher boost than another?

 

[jman_b13]

you have enough time to look at the boost guage and notice it staying put in 2nd gear? 2nd gear takes like 2-3 seconds in my car. Put it in 4th and see what it stays at there.

 

[Brantley]

you have enough time to look at the boost guage and notice it staying put in 2nd gear? 2nd gear takes like 2-3 seconds in my car. Put it in 4th and see what it stays at there.

Yes, I have probably 3 to 4 seconds which is enough time for me to make a visual pass on the gauges. The time in 2nd should drop a fair amount after I go back to a 3.73 ring and pinion. I will see what it says in 4th tomorrow at full boost.. Even if 3rd, 4th, and 5th all see the same boost, that doesn't effect 2nd. I am wondering if I am maybe starting to experience the limitations of the X to 21psi spring that comes with the Gillis valve. That's about all I can think of at this moment.

 

[Bearded Forever]

Probably. Call him up and order both of us a higher psi spring!

 

[Brantley]

Probably. Call him up and order both of us a higher psi spring!

I might just order one so I'll know.. then I'll have it around when I need it later on. I think they are $5 plus shipping, so that's not too bad.

 

[Cougar]

Think about that. 20psi in 2nd and 3rd will exert the same pressure on the spring, so it can't be that.

 

[Brantley]

Think about that. 20psi in 2nd and 3rd will exert the same pressure on the spring, so it can't be that.

I don't think the spring is strong enough to control it. Today before I left, I got to drive the stang around and noticed a few new things. 2nd gear builds to 22psi and stays for the duration of the gear. 3rd build up to 22psi but quickly drops down to 20. 4th does the same as 3rd. So why would it hold 22 in 2nd and only 20 in 3rd and 4th?

 

[Stinger]

If you take a straw and cut it so it's as long as the spring when "compressed fully" and then slide the spring inside it and install the assembly in the gillis valve you will be able to get ~25psi out of it.

Stinger