Dodge Challenger Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
760 Posts
I would say virtually everything this “expert” builder says is incorrect or outdated, beyond the simple functionality of the vvt system.

Vvt helps to create a broader powerband with more efficient low end power and not sacrifice in the rpm as much as a traditional cam platform does by allowing the cam to self retard and advance in certain conditions prescribed by oil pressure (and thus throttle position/rpm).

The reason there are cam limiter and lockout kits for aftermarket vvt cams is due to the increase in lobe size so as to maintain a safe piston to valve clearance.

There is a reason the vast majority of new model weekend racers still retain vvt blocks and cams. Any aftermarket cam (for vvt motors) is designed with vvt in mind.

He also loves saying that it’s used for exhaust gas recirculation to assist emissions... none of the car Hemi VVT motors utilize EGR systems.

That is my backyard mechanic method of explaining it. I’m sure someone with more technical knowledge can do a better job. Just sounds like this guy doesn’t know how to tune modern hemi cars.

Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
15,437 Posts
He also loves saying that it’s used for exhaust gas recirculation to assist emissions... none of the car Hemi VVT motors utilize EGR systems.

That is my backyard mechanic method of explaining it. I’m sure someone with more technical knowledge can do a better job. Just sounds like this guy doesn’t know how to tune modern hemi cars.
there's so much heresay and bad information - it seems that if someone doesn't understand the technology then they'll put it down as being "not good / bad".

Hell, there's some that still can't get their head around fuel injection...

the '03 - '08 engines had EGR systems. The '09 "Eagle" incorporated higher CR, better flowing heads and VVT and gained 35hp and improved mileage over the earlier design engine
 

·
Registered
Joined
·
43 Posts
Discussion Starter #6
I wonder if it’s an oil pressure thing? The build was fresh. Maybe loose clearances with low oil viscosity?
 

·
Registered
2015 RT 5.7 M6
Joined
·
7,602 Posts
According to this site VVT does create EGR.

"All of the rest of the VVT applications create EGR by retarding the cam to leave some residual exhaust gas in the cylinders."


I will add that if you change the part throttle cam tables to match that of the WOT tables (learned this from the guys on HP tuner forum) in the tune the engine seems to respond better/stronger and smoother.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #8
I’ve been logging my comp 270 cam with hp tuners. It does advance and retard the way that it’s supposed to. This engine does have fairly tight bearing clearance with 40 lbs oil pressure hot at idle with 5 20 oil.
 

·
Registered
2015 RT 5.7 M6
Joined
·
7,602 Posts
According to this site VVT does create EGR.

"All of the rest of the VVT applications create EGR by retarding the cam to leave some residual exhaust gas in the cylinders."


I will add that if you change the part throttle cam tables to match that of the WOT tables (learned this from the guys on HP tuner forum) in the tune the engine seems to respond better/stronger and smoother.
As further proof these cars monitor EGR...here is a screenshot of what you get when you check the PCM for DTC with HP tuners.

2015 5.7 Challenger RT
991136



Funny thing is my 2013 5.7 JGC does not monitor EGR. I think there is a setting in the engine diagnostics portion of the tune that can be switched to support or not support this monitor..not 100% sure.
991137
 

·
Super Moderator
Joined
·
15,437 Posts
the '03 - '08 engines had EGR valves. When the Eagle 5.7 came out for MY '09, EGR was eliminated as VVT could clean up the exhaust and probably with valve overlap / cam VVT and ignition timing, accomplish lower NOx emissions levels.

I remember seeing early ('06?) SRTs that had EGR valves on them as well in a couple of folks that got used Charger SRT8s a few years back
 

·
Registered
2015 RT 5.7 M6
Joined
·
7,602 Posts
the '03 - '08 engines had EGR valves. When the Eagle 5.7 came out for MY '09, EGR was eliminated as VVT could clean up the exhaust and probably with valve overlap / cam VVT and ignition timing, accomplish lower NOx emissions levels.

I remember seeing early ('06?) SRTs that had EGR valves on them as well in a couple of folks that got used Charger SRT8s a few years back
The EGR mechanism was removed but the PCM still monitors it. Not sure how as the FSM does not give details but if you check the montiors on your PCM it will give you what I showed in the image perviously.

I can see VVT emulating EGR but on a single cam where LSA is fixed not sure how it can be done as effectively as if there were multiple cams?
 

·
Super Moderator
Joined
·
15,437 Posts
in the old days a lot of NOx reduction approaches were retarding ignition timing, timing advance and fuel mixtures along with the EGR valve. And some had converters that were for NOx treatment and you also had A.I.R. systems as well.

with the OBD-II systems and today's high speed ECM there's a lot of tricks to accomplish things
 

·
Registered
Joined
·
43 Posts
Discussion Starter #13
During part throttle cruise the cam retards and that causes the exhaust valve to close later diluting the cylinder charge with spent gas.
 

·
Vendor
Joined
·
12,278 Posts
most aftermarket cams require a partial lock or complete lock on the phaser,

we also love using the HC cam with boosted application, great cam, inexpensive and we do not lock it, great performance, Bigred runs a stock 707hps cam

and made 950whps without trying or approx 1096 crank

991176
 

·
Registered
2010 R/T Classic 6M
Joined
·
236 Posts
most aftermarket cams require a partial lock or complete lock on the phaser,

we also love using the HC cam with boosted application, great cam, inexpensive and we do not lock it, great performance, Bigred runs a stock 707hps cam

and made 950whps without trying or approx 1096 crank

View attachment 991176
That's awesome, I have 392 cam in my car for an N/A setup. I haven't gotten a dyno but what do u guys usually see on FBO 392 cam 5.7s? Just curious where im around im assuming 400ish
 

·
Registered
2010 R/T Classic 6M
Joined
·
236 Posts
If you swap the intake and install headers you should be around 390ish.
Yep I got all that. Next thing up is gonna be big valve heads so I guess we'll see how much they help on a setup like mine
 
1 - 17 of 17 Posts
Top