I have read threads describing the elimination of air intake tubes & top air box cover, allowing increased intake air flow into K&N resulting in performance improvements. Since the L-Jetronic, as all Bosch, incorporates FI control, I assume there would be no fuel leaning/ mixture issues as long as O2 sensor is operation normally ?

Thanks,
Ed
Valencia, Ca

 

You will be sucking hot air into your engine. This results in LESS power.

 

Ed for all practical purposes the stock air intake system is a very good system,
use the factory filter and change it every 25K miles more if you use the car in dusty conditions, this will keep your 928 operating at peak efficiency .
Removal of the lower air cleaner will disrupt the airflow into the throttle opening and usually result in a decrease of power

 

Ed, my car in back-to-back runs with the airbox lid on, vs no lid, resulted in 6 hp loss, not counting for hot air as well. (Hood open on the dyno.)
Mr Merlin is right- leave the stock air inlet system alone, unless you want to spring for DR's Blackbird, or try and make something like it yourself....

Steve

 

+ 1
The only improvement if your intake tubes are damaged or just looking for a change is to replace them with insolated flex tubing, something like the GTS had (although it was said to be for noise and not temp reduction).
Also PorKen has a rubber cover for top of the Rad.

 

Ed
Clearly you are looking for way to improve performance....look at it this way....EVERY 928 ever made has the same intake air box (with minor changes)...and even the 959 uses a 928 air filter!!

The best way to improve performance of your 81 is by freeing up the exhaust!! A new exhaust with high flow cats (still smog legal) + 85-6 headers (since real headers will fail smog) Should get you over 200whp easy....

 

Thanks to all for your "air tube elimination" insights.

Ed

 

I take the best of both worlds. (928 stock, and the 928 modified airbox) I use the stock air tubes and I also vent the rear of the air box, to the windshield base. both sets of inlets, provide ram air pressure and it all helps with HP, with no down side. we will never know, unless we test it, if the Blackbird system, which seems to be an improvement, can actually outperform the stock air box, but with rear vents. Kind of an unfair comparison, as the base windshield vent, really only works on a race car with no AC,heater stuff.

 

I did the same thing and posted a 4 HP loss.

It might not be that bad with the car in motion.

One thing is for sure, it sounds cool as you can clearly hear the intake action.