3.? Liter 16 Valve Turbo Thread
08-23-2006, 04:38 AM
#76
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Originally Posted by Chris White
How about a dual cam drive with independently adjustable cam timing instead of the variocam? That way you can decrease the amount of intake/exhaust lobe overlap – something the turbos don’t like.
Might look something like this -
Might look something like this -
For a street engine, do you think it would be worth the extra effort to deal with variocam?
VarioCam was designed primarily to increase torque and power through the rev range, a good side effect is that it also helps to reduce hydrocarbon emissions to a high degree in the 968's exhaust.
The VarioCam operates between 1500 and 5500rpm, and will vary the timing of the inlet camshaft in relation to the exhaust camshaft this has the effect of increasing the overlap and so increases torque.
At the appropriate time the engine management system will send a command to the VarioCam solenoid to move a control piston, oil pressure will then flood a cylindrical chamber and this applies pressure onto the cam chain tensioner, varying the timing.
This system can adjust the cam timing by as much as 15deg., which enhances the torque by up to an extra 6lb ft. When 5500rpm is reached and more bhp is needed rather than torque the system goes into reverse, this can then release an extra 5bhp.
The VarioCam operates between 1500 and 5500rpm, and will vary the timing of the inlet camshaft in relation to the exhaust camshaft this has the effect of increasing the overlap and so increases torque.
At the appropriate time the engine management system will send a command to the VarioCam solenoid to move a control piston, oil pressure will then flood a cylindrical chamber and this applies pressure onto the cam chain tensioner, varying the timing.
This system can adjust the cam timing by as much as 15deg., which enhances the torque by up to an extra 6lb ft. When 5500rpm is reached and more bhp is needed rather than torque the system goes into reverse, this can then release an extra 5bhp.
08-23-2006, 08:59 AM
#77
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[QUOTE=Weissach Vampire]Well, that could be good enough...
For a street engine, do you think it would be worth the extra effort to deal with variocam?
QUOTE]
I toyed with the idea of triggering the variocam with the tec3 but I still prefer dumping the chain drive system and gaining the independent adjustability of the cams. Keepign the stock drive system (including the variocam) is actually eaiser than the twin gear system….there is a lot of machining and detail work to set up the belt drive.
Yep, this is true even with the non variocam S2 16v set up. Higher revving NA set ups use more overlap to up the volumetric efficiency of the system – not good for turbo motors.
Either way the added half a liter will easily make the up difference on the low end and then really shine at mid and high rpms…
For a street engine, do you think it would be worth the extra effort to deal with variocam?
QUOTE]
I toyed with the idea of triggering the variocam with the tec3 but I still prefer dumping the chain drive system and gaining the independent adjustability of the cams. Keepign the stock drive system (including the variocam) is actually eaiser than the twin gear system….there is a lot of machining and detail work to set up the belt drive.
Originally Posted by Weissach Vampire
I guess that you would have to decrease the overlap earlier than 5500RPM on a boosted engine so that the pressure doesn't blow the mixture out into the exhaust?
Either way the added half a liter will easily make the up difference on the low end and then really shine at mid and high rpms…
08-23-2006, 12:36 PM
#78
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Looking at the powerhouse dyno chart, the differences in point of max torque rpm are quite impressive. I did not think it would be possible to see 700rpm difference when comparing STOCK cams. The S2/968 are for NA and I guess the 8V head uses turbo cams. Peak torque should come around the point of highest volumetric Eff of the engine. When driving a S2 (NA not turboed) my feeling, and the torque curve too, point to max torque at about 3500/min if I remember well and this shifts in a turbo application by more than 1400rpm, quite remarkable. On the other hand when comparing the turbo to the S2 the turbo does not seem to die going towaards higher revs whereas the S2 clearly runs out of steam above let´s say 5700-6000rpm.
I wonder if both cars differened in more than just the head. I find this quite likeley. After a look at the powerhouse side I noticed their 16V intake. Hard to judge just by looking at the picture but in my eyes it did not look like it favours low rpm (in fact it looks like it does not favour any rpm rage at all...).
Does anybody have a propper comparrison of a 8V vs 16V ?
I wonder if both cars differened in more than just the head. I find this quite likeley. After a look at the powerhouse side I noticed their 16V intake. Hard to judge just by looking at the picture but in my eyes it did not look like it favours low rpm (in fact it looks like it does not favour any rpm rage at all...).
Does anybody have a propper comparrison of a 8V vs 16V ?
08-23-2006, 02:31 PM
#80
Three Wheelin'
In order to take advantage of the 16v heads good flow, stock (and poor design self made 
) intakes must be thrown away quickly.
it needs something like this, only in completed way. This is intake for my 931, I haven't installed the difuser yet and not welded it completely (I have to try it in my car before, just in case), but you get the idea.
) intakes must be thrown away quickly.it needs something like this, only in completed way. This is intake for my 931, I haven't installed the difuser yet and not welded it completely (I have to try it in my car before, just in case), but you get the idea.
08-23-2006, 03:52 PM
#82
Three Wheelin'
I tried it on my friends 944, it fits when i shorten the runners by 10mm and reduce the diameter of the main plenum by 10mm. The difuser mounts to the top obviously.
I'm talking this because I'm currently building a 2.5liter 16v (S2 head) engine and I'm fabricating similar manifold using stock S2 intake flanges.
I'm talking this because I'm currently building a 2.5liter 16v (S2 head) engine and I'm fabricating similar manifold using stock S2 intake flanges.
08-23-2006, 04:11 PM
#83
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Have you guys look at this latest Powerhaus Experiments.They got some intresting results.
copy from their webpage:
The results of our VarioCam testing are very pleasing. By optimizing the use of the VarioCam system, our latest 3.0L 16-valve PowerHaus 968 Turbo engine made more power and torque despite running less boost pressure. Additionally, the torque curve comes up to 470 ft.lbs. at only 3,600 rpm, hitting a peak of 476 at 3,800 rpm, and stays level until 4,600 rpm. At 4,400 rpm the horsepower exceeds the torque, and climbs to 542 hp at 7,000 rpm. These results of 542hp & 476tq were achieved at only 1.06 bar of boost!
Also the link to the dyno chart.
http://www.powerhaus.com/dyno.jpg
What do you guys think?
Regards,
AL
copy from their webpage:
The results of our VarioCam testing are very pleasing. By optimizing the use of the VarioCam system, our latest 3.0L 16-valve PowerHaus 968 Turbo engine made more power and torque despite running less boost pressure. Additionally, the torque curve comes up to 470 ft.lbs. at only 3,600 rpm, hitting a peak of 476 at 3,800 rpm, and stays level until 4,600 rpm. At 4,400 rpm the horsepower exceeds the torque, and climbs to 542 hp at 7,000 rpm. These results of 542hp & 476tq were achieved at only 1.06 bar of boost!
Also the link to the dyno chart.
http://www.powerhaus.com/dyno.jpg
What do you guys think?
Regards,
AL
08-23-2006, 04:33 PM
#85
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AHH, now I found it as well on the powerhause page. But I think you were misslead by some comments in that small report. The boost pressure at which they achived the numbers you quote was a more realistic 1.45 bar (on 100oct). You can find this by followint their "hot" button.
08-23-2006, 05:20 PM
#88
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Joe's engine should be based on a 944 S2 head, not 968 head like Miles' engine, I could be wrong though. I think Miles' engine was the 1st time they used variocam and EFI. The numbers were on an engine dyno.
Raj
Raj
08-23-2006, 05:43 PM
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You are right Raj, The engine Tedesco was reffering to is a S2 base engine whitch is Joe's engine. The link a posted is from a 968 base engine. Totally different animal.
Regards,
AL
Regards,
AL
08-24-2006, 11:53 AM
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So they made a step from 480RWHP at 1.45 bar on 100oct to 540 RWHP at 1.06bar with mechanicaly virtualy the same engine (S2 vs 968) ??? Whome do you want to make this belive?? Variocam can do something but I guess this a bit overestimated to say the least if it did not go up in the revs as well to lets say 9000ish...