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VVIS Install Walkthrough – “Yitsbox”

In the dash Working

Interested in the famous VVIS install on your non-turbo 850? MVS super contributor Neil shows us how he did it back in 2012.

Availability of this VVIS mod is not certain, let’s start there. Another important fact is that it works on 1993 and 1994 N/A 20-valve 5-cylinder Volvos, unless you want to look at doing a manifold mod to install this VVIS mod.

Here is the original VVIS mod forum topic.

VVIS / Yitsbox Theory

Yitsbox inventor razorx:

The 20V non turbo models had a variable inlet manifold, to increase engine efficciency. Well this topic is all about the control of this manifold and how to improve the behaveour of the engine.

OK you will reach not more bhp’s but much better behaveour and performance in low revs.

Let me explain:

While reading the original design documents, I arrived at something interesting about VVIS (Volvo Variable Induction System). Please read carefully:

vvis theory

Ben850 (Neil):

I have only put about 20 miles on it since the installation, but it is a completely new experience. It runs through the gears effortlessly (automatic) whereas it bogged in mid powerband, and upshifted at inappropriate times before. For instance, while ascending a slight grade, it seems to pull right on up without upshift, and very little extra throttle.

The throttle comes on instantaneously, and remains consistent to the amount of “foot” you put into it. I can only imagine this being a positive with respect to mileage.

The only negative to mileage is the amount of “foot” that I find myself wanting to put into it. I have seriously never felt it launch off the line like it does now. I know that is also partially due to the throttle body modification.

In summary, I think it was the most pleasurable outcome to ask for. This was money well spent for the immediate return, and the project itself was not difficult. Actual time working, approximately 2 and a half hours. More time was spent thinking through the routing of the wire, but once it came to me it went fast. And I took Photos.

So if you are dealing with a VVIS equipped setup. I can highly recommend this little box.


Vacuum solenoid

Installed Yitsbox VVIS Modification

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