Texas Speed Stage 3 VVT Camshaft C7 GS does not make power before 4600 rpm

[cmitchell17]

Making sure that hp tuners has the right parked cam position value for a new aftermarket cam would only be techincally necessary if you still had VVT enabled right?

[pmoore4321]

If I understand it correctly, "zero" in the HPT cam tables is parked. Any positive number entered is retarding the cam. You can enter negative numbers, but they don't apply to these engines. Negatives do work in other engines with dual camshafts.

I don't know if the number in the tables represent cam or crank degrees. I read some other posts where the same question was asked. If you look at the notes for the tables, they reference "720 degrees" in some of the fields. Some of the trucks have "24" in the tables and that would be equal to three cam sprocket teeth if it's cam degrees. That seems crazy to me, but maybe not.

[HeavyChevy305]

0 on the cam table is still advanced what ever is ground into the cam from the factory. When the WOT table retards by say 9 degrees, in reality it's only like -3 degrees.

[mbray01]

You can see it has +5 degrees of advance ground into it (Specs: 23x/24x .64x"/.63x 114+5). So, with the cam phaser in the parked position, the cam would have 5 degrees advance. If you commanded 3 degrees on the phaser, this cam would be running at +2 advance. I don't know if they recommend locking the phaser for this cam, just giving an example.

the 114+5 has nothing to do with the cam being ground at zero at lock, or +7 at lock or +5 as you stated.
that spec means the cam, has an lsa of 114, however the intake lobe is cut on a 109 center, and the exhaust is cut on a 119. look at any cam card, vvt or non, and it will verify this

[g26er]

the 114+5 has nothing to do with the cam being ground at zero at lock, or +7 at lock or +5 as you stated.
that spec means the cam, has an lsa of 114, however the intake lobe is cut on a 109 center, and the exhaust is cut on a 119. look at any cam card, vvt or non, and it will verify this

eh?

You are correct on the 109/119 center lines (never said otherwise) but, that cam DOES have +5 degrees ground into it. If it were ground with no advance (0 degrees), then the center lines would be equal though exhaust would be BTDC and intake would be ATDC but, the numbers would be equal none the less. Verify with any cam event calculator.

If you knew the center lines, you could even subtract the intake ATDC from exhuast BTDC and divide by 2 and it'd tell you how much advance was ground into the cam.

The whole point of my comment was to say that whatever the cam specs say is what they are with the phaser in the parked position. Adding anything the the cam tables will move back from that advance.

0.JPG

p5.JPG

[g26er]

If I understand it correctly, "zero" in the HPT cam tables is parked.

Exactly! 0 in HPT just means you're not moving the phaser from the parked position.

[Sachs]

Guys, an update from me...

I installed the Texas Speed 360 CFM heads this week end... Car pulls even more like a bear after 4800 rpm... But... Still the same issue between 3300-3400 to 4100...

It has to be harmonics in the intake, I don't see how it could be otherwise...

Here are the MAF curves and Cylinder Airmass







Here is the calculated theorical volumetric efficiency vs actual volumetric efficiency



And compared it to stock cam :



If someone here thinks this is a tuning issue, I would be willing to pay, but today I tried everything again to no avail.

Postive side is that really the car pulls great from 4600-4800 to 7000....Also pulls great from 2800-3400 ... This flat spot is really weird. I really think that if it was an retard issue on the cam I would see it at lower rpms, which I don't. I even have more cylinder airmass than stock cam at 3200 rpm... Can't be that..

And this is my timing, with the cam phaser also perfectly aligned on the camshaft itself



And the lock on the old phaser, only one way possible. I replaced it by a new one to be sure when I checked my timing

[Ben Charles]

Email me the file and I?ll check it out.
[email protected]

[Sachs]

Email me the file and I?ll check it out.
[email protected]

Thanks I appreciate the help. Done.

[HeavyChevy305]

What's your kPa at key on engine off?

[Sachs]

What's your kPa at key on engine off?

At my altitude (2700-2800FT) my kpa is 92 kpa.

[Sachs]

I did an estimation out of my new airmass of the new power curve with the solers 95mm TB and 360CFM TSP heads



There is a significant improvement for sure, especially on the top end, but down low it is weak...

See the graph from a Camaro SS with almost exactly the same config (Jorge Loves Speed on Youtube)



He has way more torque from 3000 to 4600 rpm, but I make more power...

[Sachs]

By the way it is normal my MAF fluctuates like that ??? My Camaro SS 1LE does not do that...

[ShaneB]

Heres a screenshot of a log I took yesterday, my MAF always looks like this. 18 2SS 1LE...
MAF.png

[Sachs]

Still no fu*** luck solving this issue so far...

[HeavyChevy305]

Still no fu*** luck solving this issue so far...

Start from scratch with your stock tune. Sometimes we make so many changes that some tables get butchered without us even knowing it.

[Sachs]

I tried a completely different tune from a similar configuration and it's the same... I'll start to believe Texas Speed fucked up my cam when they grinded it...

[mbray01]

have you degree'd the cam to verify the cam events are where they are supposed to be

[Sachs]

have you degree'd the cam to verify the cam events are where they are supposed to be

I did not. I do not have a degreeing wheel, and even if I had doing it with the engine in the car seemed difficult...I took the option of doing it by dropping the cradle...

Also TSP are giving a degreeing report for each of their cams as they all go through testing... I don't believe one shop out of ten is degreeing tsp cams...

I recall my test card being good...

[Ben Charles]

I worked with Sachs a little bit and checked some stuff out... throttle looks good, fuel is right and spark is solid.