KYWes

Wondering if anyone can give an explanation of how the stock fuel regulator works on an LT1 engine. If I recall correctly vacuum is highest at idle and drops, especially, under full throttle. So is the vacuum pulling back the diaphragm limiting the fuel flow at idle but allows full flow under hard acceleration? Got the thinking about it and got to wondering how it's doing its job.

DrewHMS97SS

This isn’t about the LT specifically, but I think it does the job:

https://www.vaporworx.com/resources/...re-regulators/

Injuneer

Figure 1 in that reference is identical in form and function to the LT1 FPR.

The spring is calibrated to maintain 43.5 PSI, without the vacuum reference. When you attach the vacuum reference, the vacuum pulls the diaphragm up proportional to vacuum, compressing the spring, opening the valve to allow more fuel to return to the tank. The key is to always maintain a 43.5 PSI DIFFERENTIAL pressure across the fuel injector (rail pressure on the inlet minus manifold pressures on the outlet of the injector). As vacuum builds in the intake manifold (negative pressure) the rail pressure must be dropped a similar amount,. so there is always a 43.5 PSI DIFFERENCE in pressure across the injector.

Where the article talks about a "4th generation Camaro regulator", it is referencing the LS1 FPR, which is not vacuum compensated, in effect, a dead end/bypass regulator back at the tank, not a return flow regulator.

KYWes

Thanks guys. Good information and helpful.