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Discussion Starter #1 (Edited)
Dual throttle bodies versus 8 Throttle bodies.

If you are used to looking at chevy's or Holdens, when you first see the S62, you could be forgiven thinking it is a Dual Throttle Body setup.

But the fact is, there are no Butterfly's at the entrance to the Plenum. It is just two holes.

The beast has 8 butterflys below the 8 Velocity stacks.

When I first saw the Dinan CAI, I saw the thicker/wider external diameter hosing that joins to the Plenum.

Added to this they have the larger MAFS.

In saying this, the entrance holes to the plenum, could be considered a bottle neck. As it has remained unchanged. :biggrin:

I was taking a close look at it whilst playing around with the Velocity stacks. The two holes really are quite Thick!

What do you think would happen if one were to remove the Plenum chamber and HONE out these two holes a LITTLE? :hihi:

In otherwords, if one were to increase the inner diameter of these two holes say even just 1 to 2mm ?

Is anyone smiling yet?

MJ.
 

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I dont see the harm in it. especially if you open up everything infornt of the plenum intake. i would certainly radius the tailing edge of the two holes. I would also radius the leading edge if it is narrower than the pipe just before it. This will help to speed up the air through the hole and effectively increase flow. Post matching is quite common and usually provides a positive respoonse, even if it not measurable. The same holds true for the throttle bodies / intakes / head and headers. after the fuel is introduced things can get tricky. Turbulence is required to atomize the fuel and keep it from sticking to the sides. Since we dont have a big intake manafold full of fuel it is less relevant.

I have also thought about cutting the stock velocity stacks so that they at 1/3 shorter. All the aftermarket stacks are about 1/4 of the length of stock. By reducing this length you should raise the power curve and effectively increase horsepower.
 

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Discussion Starter #4 (Edited)
Roy said:
Doesn't the M5 have two Mass air flow Meters? If so I would think that would be the major Restriction area.
When I first saw the Dinan CAI, I saw the thicker/wider external diameter hosing that joins to the Plenum. Added to this they have the larger MAFS.
Hey Roy, Yes Dinan Have taken care of everything upstream of the Plenum, including the LARGER mafs.


Hey Falb,
I dont see the harm in it. especially if you open up everything infornt of the plenum intake. i would certainly radius the tailing edge of the two holes. I would also radius the leading edge if it is narrower than the pipe just before it. This will help to speed up the air through the hole and effectively increase flow. Post matching is quite common and usually provides a positive respoonse, even if it not measurable.
My thoughts exatcly. Dinan have done everything before and aft that point.

I just thought there may be some benefit in getting all the Dinan Gear to reach a higher potential, by removing the last Bottle neck.

I have the Technic velocity stacks. They moved the power curve Up the rev range which is good.

Powerchip have developed software for Velocity Stacks. mmmmmm
 

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Discussion Starter #5
These are the Two Holes from the inside.

 

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Discussion Starter #7
RennSportSC'dKellenersM5 said:
MArk,

Im sure it can be done but you would only want to port that out a little tiny bit....very small. Even my SC pkg doesnt have larger inlets there.
Hey Rob,

I don't think you would need to do it much. A small difference in Diameter makes a significant difference in Volume.

Dinan didn't increase the Cai by much, but they did increase it. I was just thinking about keeping that increase constant accross the board.

Say to match the diameter of the Dinan C/F CAI should be sweet. (If Possible, I haven' checked yet.)

Just thinking about the AA CAI. If it truely does have a ram flow effect, than a slight change in Diameter should yeild a nice result.

It would only be about $200 to get this done, and I am thinking it could be good for 5hp. But who knows. Perhaps this could unlock the collective benefit of all the Dinan Mods, If this was a Bottleneck point?

I guess there is only one way to find out. ;)
 

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Discussion Starter #8 (Edited)
Example Rough.

If the radius is 50 mm (about 2 inches). And I increase it by just 1 mm.

Call pie 3.14.

Example 3.14 x 50 x 50 = 7,850

Bored 1mm 3.14 x 51 x 51 = 8,167

Bored 2mm 3.14 x 52 x 52 = 8,490

8,490 - 7850 = 640 I guess thats mm2.

It seems significant. :blabla:
 

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MIB said:
Dual throttle bodies versus 8 Throttle bodies.

If you are used to looking at chevy's or Holdens, when you first see the S62, you could be forgiven thinking it is a Dual Throttle Body setup.

But the fact is, there are no Butterfly's at the entrance to the Plenum. It is just two holes.

The beast has 8 butterflys below the 8 Velocity stacks.

When I first saw the Dinan CAI, I saw the thicker/wider external diameter hosing that joins to the Plenum.

Added to this they have the larger MAFS.

In saying this, the entrance holes to the plenum, could be considered a bottle neck. As it has remained unchanged. :biggrin:

I was taking a close look at it whilst playing around with the Velocity stacks. The two holes really are quite Thick!

What do you think would happen if one were to remove the Plenum chamber and HONE out these two holes a LITTLE? :hihi:

In otherwords, if one were to increase the inner diameter of these two holes say even just 1 to 2mm ?

Is anyone smiling yet?

MJ.
Mark,

Glad to see you back and in action :15:
Always thinking about more power!

Najeeb
 

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Interesting idea, MIB. Go for it and let us know how it goes! Remember, dinan originally added a plenum spacer, to increase the volume of the plenum, so more air is ready and waiting. In a roundel (bmwcca mag) article, steve dinan is quoted as saying it was 'worth an easy 10hp' but these things never appeared on customer cars. I asked my guy at dinan, who said the cost to mill that spacer out of a billet was just too high to justify the power increase, plus you couldn't use the strut tower brace, so handling could suffer, very slightly. Just more food for thought. There is a bit left untapped in the S62... Now what happened to that guy on the board with the 'plenum spacer project.'
Mike
 

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mottati said:
Interesting idea, MIB. Go for it and let us know how it goes! Remember, dinan originally added a plenum spacer, to increase the volume of the plenum, so more air is ready and waiting. In a roundel (bmwcca mag) article, steve dinan is quoted as saying it was 'worth an easy 10hp' but these things never appeared on customer cars. I asked my guy at dinan, who said the cost to mill that spacer out of a billet was just too high to justify the power increase, plus you couldn't use the strut tower brace, so handling could suffer, very slightly. Just more food for thought. There is a bit left untapped in the S62... Now what happened to that guy on the board with the 'plenum spacer project.'
Mike
Increasing plenum volume almost always increases HP at the top end, usually without mid-range penalty. This is particularly true when "velocity" stacks inside the plenum are positioned close to the top cover as in the S62 engine. It would be entirely possible to make a raised plenum cover (not a spacer) out of carbon fiber that had a recess for the Dinan strut bar (so that the bar could sit below the top surface of the plenum). The plenum effect is due to the increase in internal volume - not the shape of the cover.

You would think Dinan would tool up for something like this, as they collect big money for parts that produce smaller gains. On the other hand, they still haven't released a clutch for the M5. Go figure.

Regards, Dick Roberts
 

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Mark,

You know that eurobahn sells a CF upper plenum that will still allow you to use your Dinan strut brace?

Also i spent a good part of friday at a buddy of mines shop in Houston (Bavarian Hyper Sports) and he had just gotten done doing a full tune of velocity stacks and the upper plenum.

He said to use the stock velocity stacks but to go with the larger plenum as when combined with his other parts, it was good for about 20hp.

Ill talk to joel and get him to forward me that guys dyno sheets...
 

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Increase plenum volume?

How about using multiple gaskets. Take 3 or 4 or 5 stock gaskets and glue them together with silicone. Has anyone tried this?

I think I will. :M5thumbs:
 

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Discussion Starter #15 (Edited)
Hey Najeeb,

I'm back in the saddle after that T.V. run. :M5launch:

Hey Mike,

Its the whole Spacer, larger plenum , that got me to thinking. I saw some articles on Low pressures effecting performance. So the job of a Good CAI is to remove some of these, and make positive pressure (ie Ram Flow).

I have removed my Maf Screens, many months ago. Which should have removed a low pressure. (Caution, I have an OZ spec car, we only have two 02 sensors, so we are not plagued by SES lights).

I figured there is no use increasing the Plenum, if you cannot fill it fast enough. You want positive pressure in the plenum, not a Low pressure.

So to complete the package, the idea is to remove all low pressures forward of the Plenum.

Dinan went a long way by putting larger tubing and the larger Mafs. But I like the AA CAI in front of the Dinan Mafs.

Bore the to entry holes to match, and add the larger volume Plenum and the right Stacks, and Powerchip tuned Software.

If all that goes well, then we are ready for larger Throttle bodies, and of course then extractors/Headers, race cats, and I already have the Tubi cat back.

Hey Dick,

I have the clutch covered buddy. :hihi:

Hey Rob,


The eurobarn one doesn't look pretty. Its all got to look good. Maybe the photo's don't do it justice.

But I have always liked the idea of a recessed Dinan Strut brace through a C/F Plenum. :M5thumbs:

MJ
 

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Roy said:
Doesn't the M5 have two Mass air flow Meters? If so I would think that would be the major Restriction area.

Roy

Do you have the H&R coilovers on your car? If so could you make a seperate post telling us your thoughts on them?

thank you.
 

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Mark,

Might i also suggest that you do the upper plenum reflective coating... i know a while back some people experimented with this. Since you do not like the CF plenum look, i would suggest to attain the same airflow and decrease in air temp due to the higher airflow, you might want to do that as well.

Thus you would not only be decreasing restriction by increasing Area (A) yo also would be increasing velocity (V) thus intake charge should decrease some but it is known that the whole intake tract on the m5 suffers from heat soak. I would suggest coating the bottom side of the upper plenum.

You could also switch over to CF velocity stacks, like i was thinking about doing as they are less prone to heat soak.
 

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Mark,

My buddy emailed me the info on that guys M5 that he just got done working on... and our discussion on the velocity stacks and plenum

I ran the different velocity stacks and found that (even with software) they give a decrease in mid band torque which is not acceptable. The max power was down a bit as well but not as dramatic as the torque loss. I ended up going with the stock air horns with the larger plenum cover and software. We managed a 10ft/lb gain through the mid range (above the pre-install and 20ft/lb above the velocity stack best run) and a 11whp peak gain at redline. From what I've seen this seems to work very well with the other mods on the car... now of course things can be different for a stock car.

Now the gentlemans car that he is speaking about has the dinan CAI's the eurobahn upper plenum and the oem stacks with SS headers/xpipe/SS exhaust.
 

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Further on the topic of increasing plenum volume, there are two photos of interest. One on the eurobahn.us/com website and the other on the dinancars.com website. The Eurobahn cover does not seem to raise the plenum lid very much, but perhaps in strategically important places relative to the two airhorns that face backwards. One of the photos on the Dinan website (M5 section) shows the plenum spacer ring. It looks like about 1/2 inch. The Dinan spacer, to my eye, would produce a much larger increase in plenum volume than the eurobahn part. However the test report described above would make the performance gain with the Eurobahn part very similar to the Dinan anecdotal claim. I don't care how it looks if it works.

As Mark has observed, I also would like the look of an overall raised plenum lid with a channel to take the Dinan strut bar. I will talk to the guy that make CF parts for the race shop to see how big a deal it is to make one. Maybe there is an issue with a sharp "ledge" on the inside of the cover transverse to the air flow direction.

I don't buy the Dinan story that a plenum spacer costs too much to make it worthwhile for 10 HP. First, Dinan is not shy when it comes to pricing. And second, any realistic production cost for a spacer would be cheap compared to the forthcoming camshaft kit, which will cost at least $3K, will take 40 hours to install, and produces only 11 HP in the 5-7300 RPM band while losing the same amount below this RPM (the area under the curve is the same, meaning the car could be slower under street driving conditions).

Maybe what we should glean from this is that the spacer volume increase works well for a stock or near-stock engine, but doesn't add much when one goes to the full S2 package with the bored-out throttle bodies and larger air horns. Examination of the Dinan sales-literature power & torque figures shows a very large (20-35 HP) gain with the throttle bodies & horns over the combination of all the preceding mods (including headers) - equal to fully half of the advertised gain with the S2 package. If the plenum spacer is still capable of producing 10 more HP on top of the other mods, I'm guessing it would be part of the S2 package.

On the other hand, it is hard to see how more plenum volume would hurt.

Regards, Dick Roberts
 

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Mottati, hey I'm the guy that made the spacer. :byee55amg
Guys it still sits on the garage shelf from the day I got it back and placed photos on the board.
In the last plenum spacer thread (many months ago)I asked if anyone wanted to test it, I'd ship it out to have someone with more time than I to test it out and see if it produces the claimed Dinan 10 hp. .
My time is still very short still, as the new baby is 5 months old and still aquireing most of my time aside from than work. I don't even get to drive my M5. It's taken about 5 months to break in the clutch....

As for the spacer to build it doesn't have to be billet, it is made out of a sheet of aluminum stock from Alcon ,cnc the whole sheet similar to business cards.
Like 4 or 6 up , I can't remember off hand since this was done quite some months ago.

Attached is a pic of a members motor, S2 I think, it shows the spacer..

here's the old link with pics ( from April) http://www.m5board.com/vbulletin/showthread.php?t=41200

Falb, you can't run multiple gaskets, they are not flat gaskets.
IF you could get enough height you'd need a stud remover and get longer studs on the topside of the stud base or just use longer 10mm bolts. Keith
 

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