Quote:
Originally Posted by Blown353
While I'm not Mark, GM does use an auxiliary electric vacuum pump on the ATS-V to supplement vacuum for the brake booster when the engine is under boost... it works great. There's a vacuum sensor right at the inlet of the brake booster and the ECM will cycle the auxiliary electric pump as needed if the brake booster vacuum drops while the engine is under boost, something which can happen if you're a heavy left foot braker.
The factory electric vacuum pump on the ATS-V is made by Hella, and they're obviously OEM quality and reliable. Hella makes several vacuum pumps with different volumes and duty cycles; many hybrid cars use them as well as the sole source of brake booster vacuum when the car is running in straight EV mode.
The ones I've had very good luck with is Hella # 8TG-012-377-701, it's one of the heavier duty, higher volume, higher duty cycle pumps for hybrids and the like. The one GM used on the ATS-V is a much lower volume, lower duty cycle unit only meant to supplant engine vacuum very occasionally, and the OEM ECM has some logic to limit the vacuum pump duty cycle to prevent overheating it. I've used the larger, higher duty cycle 8TG-012-377-701 on both turbo cars and cars with big cams and poor idle vacuum and also on a couple of rock crawlers where guys didn't want to use a hydroboost but also where losing vacuum to their power brakes would be a real problem if the engine died while all crossed up on some rocks. They pull vacuum very quickly, are quiet while doing so, and are very reliable.
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Great info. I don't want to hijack Mark's LT5 thread which I kinda did. It might be worth its own thread under brakes on how it works, wired, what to use, etc. Sounds like an excellent option for us boosted guys.