1145 replies to this topic

[CHILL Gone DUTCH]

Stage 2 zzp Cams dibilas valve springs

Edited by CHILL Gone DUTCH, 11 July 2015 - 05:31 PM.

[siztenboots]

presumably at 0° adjustment with standard cam pulley

[The Batman]

Should say which lb springs you are using aswell

[CHILL Gone DUTCH]

Think the dibilas is 77lb This is the same as the spec I now got from DBilas: - Closed seat pressure 35Kp (77lbs) @ 32.5mm. - 86Kp (190lbs) @ 11mm lift. - Coil bind/block length 20,5mm.

Edited by CHILL Gone DUTCH, 11 July 2015 - 05:38 PM.

[Tony H]

I still maintain it's valve overlap. Here's why:

 

At low RPM the valves close following the profile of the cam, as you go up in speed, the mass of the valve leads to a slight valve float. In other words, the closing of the valve doesn't follow the cam profile but instead is restricted by the speed the valve can accelerate at. This has been addressed somewhat by using stronger springs, but they add extra mass so really just delay the issue.

 

This dip appears to be at around the same RPM on engines with similar cams and springs. I would suggest that systems with original springs will see this dip lower down the rev range, however it would be very rare to find an engine with different cams but the same springs.

 

 

Why is it a dip? If the valves start getting floaty due to revs, then should more revs not exacerbate that and power die off? Why does the power recover?

[CHILL Gone DUTCH]

It's the way the gasses don't go in and out as they should of the valves

[fezzasus]

 

I still maintain it's valve overlap. Here's why:

 

At low RPM the valves close following the profile of the cam, as you go up in speed, the mass of the valve leads to a slight valve float. In other words, the closing of the valve doesn't follow the cam profile but instead is restricted by the speed the valve can accelerate at. This has been addressed somewhat by using stronger springs, but they add extra mass so really just delay the issue.

 

This dip appears to be at around the same RPM on engines with similar cams and springs. I would suggest that systems with original springs will see this dip lower down the rev range, however it would be very rare to find an engine with different cams but the same springs.

 

 

Why is it a dip? If the valves start getting floaty due to revs, then should more revs not exacerbate that and power die off? Why does the power recover?

 

 

Because the loss will be constant, increasing revs will put more air and fuel in which allow for more power. 

[NickB787]

Comp cams, supertech springs

[oakmere]

I would be very surprised if this is valve float at these rpms. This is happening below 7000rpm and the longer duration cams are probably less aggressive on the valve train. Comp cams don't have very much lift. The dip is still there on Chills stage 2 on std top end. The head was designed for low down torque not high rpm power and very few of these engines have much porting work done on the intake ports. Could this be a restriction?

[Bargi]

The head was designed for low down torque not high rpm power and very few of these engines have much porting work done on the intake ports. Could this be a restriction?

Ask Vocky, he's done them all Think theres a pic on Z22se.co.uk comparing the saab and vaux head and amount of porting possible. I was really suprised how much more you could open up the Saab. Does anyone know would our friends at CS be able to provide the raw dyno data of the SC runs so someone could graph them to scale of the more recent results for a better comparison? We might be just chasing something that's a trait of these engines. With the RPM what do these engines usually red line at? 6400 isn't it? Perhaps it's inherit in the engine and GM never really gave a toot as it was out of the spec of the engine and only showed up slightly at the power levels tested.

[The Batman]

I will find my dyno plot out. My head was ported LOADS so if I still have the dip then can rule that out

[The Batman]

This was when it was on the turbo ecu

[techieboy]

 

Does anyone know would our friends at CS be able to provide the raw dyno data of the SC runs so someone could graph them to scale of the more recent results for a better comparison?

 

 

Upload them to dynoplot.co.uk, as per my signature. Then you can compare anything/everything on the same scale.

[CHILL Gone DUTCH]

well im now on http://www.dyno-plot.../dyno/about.htm

 

not as easy as you think to get your plot up lol

Edited by CHILL Gone DUTCH, 12 July 2015 - 08:00 PM.

[CHILL Gone DUTCH]

Everyone should get there graph up on there it scales everything the same

[Bargi]

You just submit a scanned image?

[CHILL Gone DUTCH]

You just submit a scanned image?

Then trace it so dyno- plot rescale it

[CHILL Gone DUTCH]

Could the dip in power be caused by the coil pack breaking down ?

[Bargi]

 

 

Does anyone know would our friends at CS be able to provide the raw dyno data of the SC runs so someone could graph them to scale of the more recent results for a better comparison?

 

 

Upload them to dynoplot.co.uk, as per my signature. Then you can compare anything/everything on the same scale.

 

 

Cocked up the graph, how the hell do you delete it?

[CHILL Gone DUTCH]

just over ride it