ran into an issue on the dyno yesterday. the boost solenoid im using (gm) wasnt making consistant boost. i have it all set up in my neptune rtp with duty cycle for corresponding boost psi. 20% duty for 10 psi all the way up to 50% for 21 psi.


i was using the set duty cycle with the same high/low duty to run just one boost level.
anyway, occasionally i will increase the duty cycle to attain a certain boost and it will not increase the psi. most other times it works just fine.


exact situation: car made 474 at 16 psi (think it was 36% duty). i wanted to get my 500hp mark, so i upped the duty to 45% duty which from testing nets me about 18 psi. sure enough i hit the boost cut at 18.5 psi around 8000rpm. it was also a little rich, so i leaned it out and brought the boost cut up to 19.5 psi without changing the duty cycle. the next pull was down to 16 psi again. by then i was just about out of time and money in my wallet, so i had to bag it up.


do these things overheat or am i missing something else? it works fine 95% of the time, just apparently not when im on the dyno paying 100 dollars an hour to tune my car.

 

When you get a chance, change over to a Mac style solenoid valve. Those gm valves
give problems.

 

just like their map sensors i guess...