DoD thoughts

[NateD4]

The addition of DI to the vette engine continues to keep it competitive performance, weight and econmy wise. Its clear to me why GM sticks with it.

They could befit from variable cam overlap ( I believe viper has this)...

Id like to see them go to a 4.6L flat plane crank engine with AFM, DI and turbo

[caffeine]

I always wondered why the LT5 seems to have a good reputation but the DOHC V8s produced since then by GM don't have an aftermarket or a good reputation.

Another thing to consider is that IIRC the V8s are now the only engines that aren't DOHC in the lineup. I would expect that the next step would be a DOHC V8.

That being said, I'm not saying the LSx series aren't great, because they clearly have incredible potential. I just would have expected a move to DOHC by now

[robertisaar]

I was also disappointed that it looks like the Gen V SBC appears to be little more than a Gen IV with DI.

Someone local stuffed a VK56DE into a 240sx... so it can't be that hard to fit a DOHC V8 into a vette.

you say that like it's a bad thing.... the LSx are beloved for their simplicity/power/reliability/efficiency. now GM is adding a few parts to let it keep up with the rest of the field with what is essentially a design from the 50s. the actual carryover of parts from the Gen4 to Gen5 is countable on one hand, but it has it's roots clearly defined.

also, DOHC Vette happened already, it's too bad it was so damn expensive.

[caffeine]

Well the only disadvantages to DOHC are a bit more weight, a bit larger of an engine and a bit more cost. I was also disappointed that it looks like the Gen V SBC appears to be little more than a Gen IV with DI.

Someone local stuffed a VK56DE into a 240sx... so it can't be that hard to fit a DOHC V8 into a vette.

[NateD4]

I would think any "modern" engine would require DI and if possible AFM to get the best total power and efficiency package possible. In some ways it amazes me they continue to develop the LS series V8. Today the pushrod engines are almost dead except for industrial/marine applications and of course GM. Not sure to many other automakers are using them anymore... DOHC seems to be here for now...

[robertisaar]

http://www.autoblog.com/2012/10/24/gm-chevrolet-small-block-v8-engine-lt1-corvette-c7-videos/

their updated article mentions AFM as well.

[ericjon262]

I have a 3900 VVT with DOD on the stand right now. If you want to know something ask... I'll try to answer.

A few interesting observations:

The DOD bank had a lot more carbon deposits on the valves and pistons than the non DOD bank.

The lifters are indeed special and have a cut out 'latch' for lack of better terms that disengages the internals of the lifter via hydraulic pressure.

I'm going to attempt to run this setup beyond 7K RPM and see what happens....


As for mileage (no clue). From what I've heard its worth 2-3 MPG on the highway.

The reason it disappeared isn't because it didn't work, but rather because it isn't needed with direct injection.

I'm sure GM only uses it because the pushrod engines are cheaper... it will be interesting to see if the LS engines with direct injection that (were or are) rumored to be out will have DOD and VVT etc...

It's a neat concept but a headache to mess with. It requires a special cam profile for the DOD cylinders that basically adds a few thousandths extra play pickup in the ramp to remove the 'lash' of the DOD mechanism... So far the only way to get a cam is to order a custom cam....

Any other questions ask.

http://www.autoblog.com/2012/10/24/meet-the-lt1-the-corvette-c7s-new-6-2-liter-small-block-v8/

the new LT1 has direct injection and VVT...

[NateD4]

I have a 3900 VVT with DOD on the stand right now. If you want to know something ask... I'll try to answer.

A few interesting observations:

The DOD bank had a lot more carbon deposits on the valves and pistons than the non DOD bank.

The lifters are indeed special and have a cut out 'latch' for lack of better terms that disengages the internals of the lifter via hydraulic pressure.

I'm going to attempt to run this setup beyond 7K RPM and see what happens....


As for mileage (no clue). From what I've heard its worth 2-3 MPG on the highway.

The reason it disappeared isn't because it didn't work, but rather because it isn't needed with direct injection.

I'm sure GM only uses it because the pushrod engines are cheaper... it will be interesting to see if the LS engines with direct injection that (were or are) rumored to be out will have DOD and VVT etc...

It's a neat concept but a headache to mess with. It requires a special cam profile for the DOD cylinders that basically adds a few thousandths extra play pickup in the ramp to remove the 'lash' of the DOD mechanism... So far the only way to get a cam is to order a custom cam....

Any other questions ask.

[3400-95-Modified]

Don't DD the toy.... That solved my fuel use issues... well until I put shit on my legacy... lol

[bob442]

I'm just starting to see it in the shop. So it seemed like a good idea. Now I guess it's not worth it. I would have loved to play with it.

I can't think of a way to bump up the fuel economy enough for it to be worth it with out changing cams to a cam with a lower tourqe curve, and I don't plan to do that with this car... Maybe a s10 3400 would get such a treatment

[onefastV6]

Isn't it just called "active fuel management" now?

They also called it AFM, but that seems to have also been phased out.

[caffeine]

Isn't it just called "active fuel management" now?

[onefastV6]

I would exhaust all other means of tuning for fuel economy before thinking about DoD.
There is a reason that GM has phased out DoD.

[robertisaar]

http://en.wikipedia.org/wiki/Active_fuel_management

i was off a bit.

A solenoid control valve assembly integrated into the engine valley cover contains solenoid valves that provide a pressurized oil signal to specially designed hydraulic roller lifters provided by Eaton Corp. and Delphi. These lifters disable and re-enable exhaust and intake valve operation to deactivate and reactivate engine cylinders

[bob442]

Iirc the lifters are not shut down as a ls motor has the same feature, can't imagine how to shut down a mechanical part either.

Closed loop, how could I disable it.... Disconnect the o2 sensor or interrupt a signal wire for it? I'm trying to think of a way to pretty much "flick a switch" once this become "successful"

I would imagine that I would need a lower rpm tourqe cam to see sufficient results, but it's all an experiment, at 2200 rpm (110kph 68mph) I'm making 112 chp iirc so for shit sake, best case scenario I'm making half that @66 chp, should move the car. Doing 60 kph (37 mph) I go into full lockup an idle at 1100 which is pretty sweet if I did 60 for Long distances