3.9L LZ9 engine internal upgrade & performance?

[mrtohil]

I've had the transmission gears,shafts and ring gear sent out to get cryo'd and micro-polished. I've also obtained the limited slip from Quaife. The pics for the LSD, before and after pics of the gears and shafts are posted on my photobucket. The procedure was performed by Evan Performance in Atlanta,GA. Good work!

[robertisaar]

good stuff...

[mrtohil]

I have obtained the forged connecting rods from Cunningham Rods. I also had a torque plate made to properly hone the bores. I have placed the pics on photobucket. I'm still having issues getting the camshaft made. Also seeing how hard it will be to install LS1 valves. I will try to update the thread as much as I can.

[gectek]

really hard to install LS1 valves. they are too large. WAY too large. same design, but diff ballpark

[Nightingale]

Might be able to order a set of valves from manley if Ben has some part numbers from the prototype valves he had made. I bought his extra set for my project. They are the manley race flo stainless steel intake and exhaust in standard lz9 size. Also for a camshaft you can go the route I am, which is to use the 3900 to 3400 bearing spacers CNCguy made up. Should be nice now that you can order custom grinds specific for your application through the store.

[mrtohil]

Nightingale:

Do you have a thread or link to what you are doing with your LZ9? I would like to compare notes.

The problem I have with converting it to a 3400 cam is that I want to try retain the VVT function on this motor. But if the VVT can be retained while still being converted to a 3400 cam...that would be great!

[Joseph Upson]

Nightingale:

Do you have a thread or link to what you are doing with your LZ9? I would like to compare notes.

The problem I have with converting it to a 3400 cam is that I want to try retain the VVT function on this motor. But if the VVT can be retained while still being converted to a 3400 cam...that would be great!

You can't do it. The VVT cam is a unique and non interchangeable design. You can use it as is however you would need to degree it in so that it is not excessively advanced in order for it to provide optimum power. You can then limit it to a small amount of retard action since some of the range is devoted to EGR like function and may actually reduce performance. The best route is probably to have the OE cam reground to performance specs and installed at the correct degree angle and left alone.

[gectek]

the VVT events never work to your advantage due to alot of reasons. #1 this isnt VTEC people lol. #2 you have limited to no tunability for the VVT #3 they have to use a lobe that will work fully retarded or fully advanced #4 they are not made for excessive RPMS. I know in the LS engines, us going from a VVT 6.2L engine to running a straight cam that is very small by LS standards picked up over 30 HP everywhere. that means in the smallest part, 30 HP. When you try to use that same cam, it picked up a peak of 30. sabe?

[IsaacHayes]

You could use the MegaSquirt for this. You could use the Nitrous/Meth injection output to activate it. Then you could use the Nitrous INPUT table switch. That means when activated it would switch to a different VE table tuned for the cam in that position....

That seems like the best way to actually use it. You could do the same for the variable intake.

Not sure what inputs the cam and intake phasers need to switch on, if it's PWM for inbetween points or what... Or if it will tolerate a solid voltage to just max on/off...


But yeah I would probably get a 3400 style cam in there with performance grind. If anything I would just play with the variable intake with a window RPM switch or with MegaSquirt if I had it. But more than likely I'd use the VVT 3500 UIM on it and be done with it.

A 3900 with a hot cam, high compression LS1 pistons and headers would put down a healthy amount of HP NA. If I was going to turbo I'd probably leave the pistons stock and stock cam, maybe a turbo cam later but with a turbo on the engine I'm sure it'd be a beast. Hell a 3400 is pretty crazy stock with a turbo....

[Joseph Upson]

The VVT can be made to work without a VVT PCM. You have to limit the cam range and have the module set to activate under the same circumstances consistantly so that you tune the engine to that function series. Dual VE tables would not be required as long as the cam retards at the same point everytime. Continued variance would require the proper PCM.

The problem with using a 3400 cam I believe is the area reduction under the curve and that's why I recommend a regrind of the stock 3900 cam. It has large lobes and a regrind could offer even more area under the curve without increasing duration if you wanted it that way.

The key is degreeing the cam in. The locked position is to far advanced probably as much as 20 degrees and as far as rpm is concerned the OE limit is about 6300 rpm, hardly an indication VVT is no good for high rpm. The initial peak hp ratings were at 6000 rpm per GM.

Limit the cam travel to a few degrees retard 4-6, I would think the ecm could compensate for that much anyway without extra tuning.

[robertisaar]

i'm new to the specific application, not the concept, but is the amount of advance/retard controlled by voltage, amperage or does it use some other form of control?

[pocket-rocket]

I would imagine it's PWM if I had to take an educated guess.

[Joseph Upson]

I would imagine it's PWM if I had to take an educated guess.

You're correct. A constant voltage should be fine for a primitive function though. The reason I said limit the max cam retard is because when I had the cam locked in the full retard position fuel economy was awful, probably as bad as 8 miles per gallon. I could actually drop the needle reving and idling in the driveway for a few minutes. With the cam fully advanced it's just the opposite. I figure installing the cam with about 5 degrees advance and retarding it to about -5 deg or so at around 5000 rpm should work pretty well.

One thing is for sure, the reground cam doesn't produce the same effect when retarded beyond 0 deg as the stock cam does. The stock cam increases power all the way up to the max stop, while the regrind with narrowed LSA drops in power beyond 0 deg. Both cams produce about the same peak power. That's why I feel increasing duration and lift on the stock cam and leaving the LSA alone may be the most effective route to take in increasing output.


Forgot to mention that I compared the cams in a dyno simulation.

[robertisaar]

You're correct. A constant voltage should be fine for a primitive function though.

so, according to that: as long as we use RPMs as a reference, we can feed the controller our own idea of what is right, based on what i'm assuming is either a 5 or 12 volt signal?

[CNCguy]

The ECM constantly monitors cam position relative to crank position and adjusts the actuator via PWM to achieve desired timing. Due to variations in oil pressure, internal clearances, valve train load and other variables a specific pulse will not provide a consistent timing location.