Why did volvo remove the variable intake manifold?

[V50M66]

It doesn't flow very well compared to later NA non-VVIS manifolds, was expensive, and added failure points. The addition of VVT further got rid of any reason to have it.

[dikidera]

Are there any flow measurements?

[V50M66]

Are there any flow measurements?

No hard flow bench numbers, but the FCP guys were trying to utilize the VVIS intake on their NA 850 track build and were quickly running out of flow. Switching to a later NA manifold solved those issues and allowed them to tune further and make significantly more power.

[dikidera]

I just saw the video after googling a bit. Indeed very disappointing. Luckily it cost me only $15 and I already have a bunch of aluminum junk to sell to scrap yard. So I didn't lose anything.

The biggest thing I personally noticed when I got the VIS was indeed the very narrow channels. I did feel like some of it can be a restriction. Since now you have this thick(or thin?) separator of the channels taking out of the total port volume. And that is what they do mention.

Of course I can think of at least a dozen more issues which cannot really be verified, but yes the swap for the normal NA manifold did yield 8 more wheel hp at the top end. Which means it was a restriction and I believe the official docs did mention something about keeping the channels open at certain points to minimize flow losses, which means that Volvo knew it was a restriction even back then. It probably served its purpose back then for getting good torque between 1 and 3k or 4k rpm and to get the car at standard whp as advertised.

[MrAl]

For a while now I have studied why the P2 platform NA engines had this weird torque dip around 2000-3000rpm. I started to speculate it's either something related to emissions and is related to valve overlap between intake or exhaust(this cannot be cured without a different exhaust) OR it had to do with intake resonance.

Then after googling it became apparent that the 850 20v NA engines had a variable intake manifold, my god, and this eliminated that exact torque dip perhaps confirming it was indeed the problem of intake resonance.


I mean why would they remove this beautiful thing. And also, does the 850 intake manifold fit P2 cars(after 2000)?

Hi,

When I first looked at the graph I had to read the text in order to understand which plot was for which ordinate so I color coded them both. This happens in electrical stuff too such as data sheets where they get copied to black and white and then sometimes it is hard to figure out which plot goes to which ordinate. In this case it was not too difficult but I thought it would be a nice touch to see them in different colors so it would be immediately apparent which plot goes to which quantity. See how quick it is to tell when they are different colors.

Mainly though I wanted to point out that I thought it was interesting that they seem to have done some research on what kind of engine noise was more "appealing". I thought that was funny. I wonder how they would feel about the engine noise of an Electric Vehicle.
We have some cars around this neighborhood whose owners seem to think that louder is better. Some of the cars sound like racing cars not only when they drive down the street but even when they first start them up in the morning. I have to wonder if they didn't drill holes in their muffler on purpose just to be able to sound like a race car

[dikidera]

For a while now I have studied why the P2 platform NA engines had this weird torque dip around 2000-3000rpm. I started to speculate it's either something related to emissions and is related to valve overlap between intake or exhaust(this cannot be cured without a different exhaust) OR it had to do with intake resonance.

Then after googling it became apparent that the 850 20v NA engines had a variable intake manifold, my god, and this eliminated that exact torque dip perhaps confirming it was indeed the problem of intake resonance.


I mean why would they remove this beautiful thing. And also, does the 850 intake manifold fit P2 cars(after 2000)?

Hi,

When I first looked at the graph I had to read the text in order to understand which plot was for which ordinate so I color coded them both. This happens in electrical stuff too such as data sheets where they get copied to black and white and then sometimes it is hard to figure out which plot goes to which ordinate. In this case it was not too difficult but I thought it would be a nice touch to see them in different colors so it would be immediately apparent which plot goes to which quantity. See how quick it is to tell when they are different colors.

Mainly though I wanted to point out that I thought it was interesting that they seem to have done some research on what kind of engine noise was more "appealing". I thought that was funny. I wonder how they would feel about the engine noise of an Electric Vehicle.
We have some cars around this neighborhood whose owners seem to think that louder is better. Some of the cars sound like racing cars not only when they drive down the street but even when they first start them up in the morning. I have to wonder if they didn't drill holes in their muffler on purpose just to be able to sound like a race car

You have them mixed up. Your graph shows torque at 280nm which is very incorrect, torque is the flatter line, whereas hp is the long line pointing upwards.
I was also told by many people who tune cars on dynos that the torque graph for the 850 glt is bogus. It is not scaled. They said by definition torque and hp should cross at 5200-5400rpm and it isn't. As such they concluded that the graph is very very misleading, possibly for marketing purposes.

UPDATE: The colors have been fixed and the graph is now correctly showing proper torque and hp.

[MrAl]

You have them mixed up. Your graph shows torque at 280nm which is very incorrect, torque is the flatter line, whereas hp is the long line pointing upwards.
I was also told by many people who tune cars on dynos that the torque graph for the 850 glt is bogus. It is not scaled. They said by definition torque and hp should cross at 5200-5400rpm and it isn't. As such they concluded that the graph is very very misleading, possibly for marketing purposes.

Hi there,

No, they are correct (ha ha). Well, they are correct NOW

Ok yes, they were reversed, but hey, at least you could read them faster

Ok it's been corrected, thanks for noting that or else it would have remained incorrect for years probably.
See, that's what happens when two plots on the same graph are the same color and/or style
Typically in a lot of electronic stuff they use a dotted line for the 2nd plot, but that gets weird too once we get 3 or 4 plots on the same graph. That could be because they don't want to run into the same problem where the translation to black and white mixes all the plots up together like the original one. In some electronic stuff it gets so weird it may take several minutes to figure out which is which.
It also gets weird when the two plots cross each other and the two are relatively smooth. It's hard to tell which is which after the crossing because you don't know which one went up and which went down (after the crossing point).

You may want to edit your post too so that future readers do not think the two plots are still reversed.

[dikidera]

Well I dont really want to give up on this manifold just yet.

I messaged the FCP guys as well as their tuner asking for some more information on things. For instance, they claimed in the video while assembling the engine still, that they had sporty cams and a ported head, yet with the regular intake manifold they made stock power. I am wondering if they voice-overed the video on a later date and got the information wrong.

I do remember that in the video they opened the short runner at a much later RPM range, like 4850 RPM instead of much earlier at 4100 rpm like Volvo did originally. I am also wondering if their cone filter also didn't cause them to lose power. Intake air housings are not just for show, they do dampen sound yes, but also are constructed to take advantage of intake resonances and as such boost airflow.

Yes it is still possible that the vis manifold has too small of volume for high rpm applications. The VIS manifold intake runner lengths are 50cm for the long one and 25cm for the short one. If the long one's specifics caused it to get its torque peak at 3300 rpm, then the short runner should have had it's peak at 6600 rpm, but since there are some differences in both ports, the long one is normal, while the short runner has the flap in the way

Allow me to doodle again



We can see here that for the short runner the air actually falls into a small valley behind the flap which may cause turbulence and slow the air down. Next issue would be how the fuel is injected on the upper port, maybe the fuel is not mixing well at that point there.

Or maybe the manifold IS indeed not that optimized in the first place for more power, perhaps it was always optimized for more torque and less hp.

[abscate]

They said by definition torque and hp should cross at 5200-5400rpm and it isn't.

This isn’t right, both mechanically , and graphically. How you choose the axes will determine when plots cross, this is kind of math 101 fail. Put a turbo on the car, or VVT and all this stuff changes of course.

[dikidera]

This is the information though

https://www.motorauthority.com/news/111 ... t-5252-rpm