Lock has nothing to do with instability. It just prevents to advance too much (when it's a partial lock). The cam phaser is hydraulic, works with your oil pressure through the solenoid valve (they call it like that) which bolts the cam phaser on the camshaft. This bolt is like an hydraulic distributor. Issue is with big lift and angle load is too big for the camphaser and it cannot maintain anymore the desired position. You can see that in vcm scanner there is a log parameter which is cam position error in degrees (perhaps not the exact name). In stock form you already have few tenth of following error.
Yeah I knew how it all worked but I didn't know the large cams made them too unstable. I thought people just mostly chose to lock the cams to zero but I've seen quite a few tunes where the aftermarket cam is only moved a little bit and typically only above peal torque. I suppose the only way to go is larger TB and ported heads as you've already suggested.
So here is the raw MAF Hz reading compared:
Capture.JPG
Looking at this data it basically looks like the Rotofab doesn't do as much, although it still seems like it helps a little at higher rpms, so are you saying that the airflow correction models are messing the data up? And another thing I forgot to mention is I've put a lot of miles on the Rotofab and I know it dosent have much filtering area, I wonder if its possible its just clogged? I've tried to blow it out but I don't have a compressed air source. Their instructions basically say if the wire mesh is still visable you are good and don't need to replace the filter, which mine is very visible and clean looking.
And I did use the same tune, so the same MAF calibration between the runs.
And TSP told me the same thing, they just found the extra power from the VVT wasn't worth the hassle and liability since with stiffer springs and higher lifts they were seeing too much movement to be comfortable with. They said they were going to "redesign" their LT lineup after they finished with the Hemi cams, so I guess that means we put in a unoptimized and obsolete cam haha. I am still thinking that the gains are basically negligible with single/non-independent phasing and is mainly for the EGR effect.
Last edited by cmitchell17; 04-02-2020 at 09:14 PM.
I believe you have 7.5 degrees of total advance with the VVT completely locked out. 4 degrees of advance in the cam + 3.5 degrees of advance by locking the VVT. That's almost a jump in cam sprocket tooth.
If I understand it correctly, locking the phaser out is really locking in an additional 3.5 degrees of cam advance. It's being locked to the "parked" position, not zero or neutral.
https://www.underhoodservice.com/gm-...flow-pressure/
most aftermarket cams, to my knowledge are ground with the lock position being zero, not +7. The cams i order anyways, have always been on zero, this is verified with a degree wheel. You are using a degree wheel when installing cams to verify correct cam timing, right?
Also going back to the dyno graphs posted, if you look at the dyno info, it appears like possibly the first run was non loaded, sweep test, while the second run was loaded, road simulation. These differences in loading will absolutely give you different graphs(assuming i am reading the information correctly)
Michael Bray
Rusty Knuckle Garage
Slidell, Louisiana
20yr Master Tech.
Advanced Level Specialist
Custom Car Fabrication, Customization, High Performance.
GM World Class Technician
Shop Owner
That's interesting. If you verified timing at what is listed as "zero" according to that article/diagram, where does the +3.5 degrees of cam timing come into play? The aftermarket block locks the cam in the fully advanced position which the diagram shows is beyond the zero mark.
That's just it. The park position on the LT engines, according to the article, is not zero. It's +3.5 cam degrees advanced. Maybe it doesn't matter mechanically, but I was thinking maybe it is confusing the ECM.
I think I know why this setting exists.
IMG_20200404_103918.jpg
I did my test with the Ported Soler 95mm TB. No changes at all ...
Guys one question.
When I zeroed the VVT, I put also under Variable Camshaft : Intake Min at 0deg.
Believe it was 4? stock
Could this parameter mess sup something ? I'm assuming it is the default advance of the cam
Thanks
Nope It was 2? and I did a test with it at 2? and as expected nothing changed
Last edited by Sachs; 04-04-2020 at 07:40 PM.
I hope the ported heads will solve my flow issue because I start to worry a little bit. This is really weird I have more torque at 3300 rpm than at 4000 rpm.
Recap of current mods :
Soler 95MM LT5 Ported TB installed today
No change at all in the problem area
This ported TB drives great though, very good response. I calculated max area at 5600mm2 seems to work fine
I really hope the heads are the issue and the ported ones I bought will solve my issues. If it not that, I am lost
Recap of current mods :
- AFE CAI
- Soler 95mm Ported TB
- MSD Intake Manifold (home ported)
- TSP Stage 3 VVT cam with all supporting mods (Morel hydraulic Lifters/PAC Dual valve springs/Titanium retainers/Chromoly 7.850 pushrods/C5R timing chain/Trunion upgrade/DOD delete/32% fuel lobe with lash cap)
- ARH LT headers
- Catted X pipe
Waiting on Ported TSP Heads. What is crazy is that stock IM/Stock TB moved the RPM band 500 rpm lower (4500+ instead of 5000+) but still has the gap between 3500-4100.[/B]
Last edited by Sachs; 04-04-2020 at 07:54 PM.
We have already built many C7 LT1 engines
Before we do a job, I talk to my customer:
What is your expectation
How are you driving?
Racetrack or more power for the street
For the racetrack, if you want the engine to work between 4500-7000RPM, then large camshafts are interesting
You can gain a lot more performance
But, you always have a loss in torque at lower revs
If you are looking for more torque and a little more power for the road.
I have had the best experience with this
Stock engine LT1
Floor exhaust system
AFE air filter with original throttle valve
MSD Intake, transitions cleaned very well
lightweight flywheel from Katech
The AFR air gasoline setting rather a bit fat I go with a maximum of 0.86 Lamda
Very deep water temperures are also very important
Maximum 85-90 ?
If you have these points, you can go forward with the ignition without getting knocked
Roadcourse/AutoX/Mountain Hill climbs
This cam should work for this application, seeing all the other dynos. It makes great torque from 3500-7000.
The only difference in my configuration is that I have stock heads vs ported heads on all the other dynos I see
I assume and hope my issue comes from there. My cam makes great torque at 3300 then fall off. Stock IM or MSD IM. Only thing which makes sense is a flow turbulence/disturbance/stall at some rpm ranges
Michael Bray
Rusty Knuckle Garage
Slidell, Louisiana
20yr Master Tech.
Advanced Level Specialist
Custom Car Fabrication, Customization, High Performance.
GM World Class Technician
Shop Owner
Some are ground 0, some +4 or anything else the the manufacturer decided to spec the cam at. Whatever the advertised advance a cam has is what it will be when the cam phaser is in it's parked position. If the phaser wasn't locked and you commanded 3 degrees of cam timing on a cam advertised as +6 would pull it back to +3. However, if it were locked, it would always be +6
I looked at Texas Speed site and they don't show the advance of the vvt 3 cam. If you look at this cam from Brian Tooley (randomly picked one)
https://briantooleyracing.com/btr-ca...243144145.html
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.
Last edited by g26er; 04-07-2020 at 02:20 PM.
2019 Corvette Grand Sport Black
2018 Camaro SS Bright Yellow
Thanks! That exactly what I thought was going on. Seems like a big deal to me and most cam makers don't even bother to list the cam timing. Next question, are the cam tables in HPT in crank or cam degrees? The notes in the description of the tables mentions "720 degrees" which makes me think it's crank degrees.
Last edited by pmoore4321; 04-10-2020 at 09:11 PM.