Air injection pump removal

[Jay-@]

Hi All.
Pulled the engine of my motor to replace the clutch in my '87 930. While it is out I was going to do several other things to it. I was wondering if any of you have removed the air injection system? If so what need to be done? I have taken the air injection system off of a '73 MG but that was a much simpler system.
Thanks

[Noah930]

I haven't done it because I live in California. But there are holes left by removed hoses that have to be plugged. Be sure to save whatever you remove, as even if you have no need for it, there's someone in California (or someone who wants to restore their car to stock before selling it) who needs it.

[RarlyL8]

Yes it is common to remove the air injection system from a 930 engine if you reside outside of areas requiring its retention. Unbolt everything and pack it in a box for the next owner. As Noah stated the injector holes need to be plugged, our host sells them. Be careful when removing the spider and the injectors as they may be very rusty. I have pulled injectors out of an engine that had the entire tips gone, they had rusted away and been spit out through the turbo over time.

[991gts6s]

I took off mine yrs ago.. only a few plugs needed.. I think it lost power doing it tho

[Mocker]

Originally Posted by 991gts6s

I took off mine yrs ago.. only a few plugs needed.. I think it lost power doing it tho

How do you figure that?

[dannobee]

Hans Mezger wrote an SAE paper on the secondary air injection system helping eliminate turbo lag. Adding air to the exhaust raised the EGT by 80-90C degrees, helping the turbo spool up faster.

[flightlead404]

Originally Posted by dannobee

Hans Mezger wrote an SAE paper on the secondary air injection system helping eliminate turbo lag. Adding air to the exhaust raised the EGT by 80-90C degrees, helping the turbo spool up faster.

Interesting. Is this a general paper, or specific to the 3LDZ setup with the 930.

Based on the graph peak HP isn't changed, just reached a few hundred rpm earlier. I wonder what the effect would be with the modern earlier-spooling turbos many of us have.

[RarlyL8]

Pretty sad when you need an air pump to make your turbo perform better. I'd remove the air injection and install a better turbo. Headers will also reduce 3LDZ lag by ~500rpm.

[dannobee]

Ferrari used air injection on their FI turbocharged cars. And it's been used for years in World Rally Championship cars.

https://en.wikipedia.org/wiki/Antilag_system#Secondary_air_injection,_or_inlet_b ypass

My first experience with it was when I was working at the dealership. Had a customer noticing that "something didn't feel right" and "the power seems down." After inspecting the usual suspects, noticed a broken air injection pump belt, and guess what, problem fixed.

[RarlyL8]

Turbos operate off of heat and exhaust gas velocity. I'd rather increase the exhaust gas velocity via a properly designed exhaust system than add heat. Heat shortens the engine's life span which isn't a concern for race cars or OE smog engines that are out of warranty when they die. If longevity is not a concern you can do both plus add a quick spool turbo for an optimal kick. Keeping the intake temps down also lowers boost threshold.