2016 Silverado Refresh

[mr_bots]

I'm well aware of the coking issue on most, if not all, DI engines. I just don't think DI is going anywhere, just going to be improved to where it's no longer an issue. DI does more than VVT, atleast on these engines. VVT on a single cam engine doesn't do much. Compare the non-VVT to the VVT Gen IV 5.3, it didn't do much besides knock the torque peak down a few hundred RPM.

 

[1BADSS396]

I'm well aware of the coking issue on most, if not all, DI engines. I just don't think DI is going anywhere, just going to be improved to where it's no longer an issue. DI does more than VVT, atleast on these engines. VVT on a single cam engine doesn't do much. Compare the non-VVT to the VVT Gen IV 5.3, it didn't do much besides knock the torque peak down a few hundred RPM.

I agree.

 

[DV2000NJ]

Yes, it adds efficiency and some power...but at a cost. Cost to build and a cost to maintain. It's to help satisfy CAFE....period. They try to sell it has a performance feature...Bullshit. You can believe that if you want. There are better/cheaper/more reliable ways to increase power.
.

I will believe it. Not because I want to, but because I understand that when you can increase the compression ratio and further advance timing, an engine will run more efficiently. This isn't something to "believe" or "not believe". That's how engines work. "Period".

And name one other way to increase power AND fuel economy? (Tuning is irrelevant, as it can be done on any engine, MPFI, DI, carbed...)

Even though every other car nowadays seems to offer gasoline direct injection (GDI), Mercedes-Benz was the first to exploit this technology in the 1955 300SL. But it wasn’t until the mid-1990’s that other automakers started to use GDI in mass produced vehicles. GDI promises marginal increases in fuel economy (3% reduction in BSFC )

As an engineer, you should understand that a 3% increase in efficiency on any system that already damn close to being fully optimized is a HUGE difference. Not "marginal".

There several reports of C7's on CorvetteForum that are reporting coked intake valves and drastically reduced power and fuel economy...with less than 50K miles on them.

You can believe what you want.

I'm not disagreeing that coking is an issue with some (or most or all) DI systems. GM's system may very well be a piece of shit right now. But some manufacturers have developed ways around the problem (look into the Toyota system that has been mentioned multiple times).

And if DI adds sooo much more power, how come the LT1 6.2 in the C7's only produces 24 more HP than the port fuel injected LS3 in the C6's? And the LT1 also has VVT, which likely accounts for most of that 24 HP increase.

Pretty sure my tune covered that spread.

Oh, and it only gets about 1 MPG better hwy FE. (30 vs 29) with AFM.

Are the DI issues really worth it in the LT1 vs the LS3? Hell NO!!!!

Great, so your tune covered the spread. What do you think happens when you tune a DI engine? Give up? It will also increase horsepower. As Matt mentioned, VVT on a single-cam engine doesn't do much for increasing power, mostly just moves the power band around. But you said it yourself, from the factory the LT1 is both more powerful, and more fuel efficient. You can't deny that DI has something to do with that.

Jeff, you're an engineer. I'm sure you've worked on systems early in their development. Just because they're not perfect right off the bat doesn't mean that you scrap the idea. I'm not trying to convince you to go buy a vehicle with DI, but to deny that it has SOME significant advantages over MPFI, and to claim that it is purely being done to satisfy CAFE standards is being willfully ignorant.

 

[1BADSS396]

Dan, reading comprehension is your friend. Learn it, embrace it.

What happens to those FE and power gains as carbon builds up on the intake valves Dan? Guess what, they go bye-bye....in many cases with less than 50k miles on the clock.

I never said they should scrap it. I said I will not buy one until they figure out a full solution. Not if I have a choice anyway.

 

[DV2000NJ]

Dan, reading comprehension is your friend. Learn it, embrace it.

What happens to those FE and power gains as carbon builds up on the intake valves Dan? Guess what, they go bye-bye....in many cases with less than 50k miles on the clock.

I never said they should scrap it. I said I will not buy one until they figure out a full solution. Not if I have a choice anyway.

First of all, there's no need to be a condescending prick.

And great. Valve coking. We've already established that it happens.

On the subject of reading comprehension and valve coking, did you completely miss the part about Toyota's system that appears to have almost completely eliminated the coking issue that was mentioned three times?

 

[1BADSS396]

Great. Valve coking. We've already established that it happens.

On the subject of reading comprehension, did you completely miss the part about Toyota's system that appears to have almost completely eliminated the coking issue that was mentioned three times?

yeah, so....what's your point? I should go buy a Toyota then? No thanks.

 

[DV2000NJ]

Great. Valve coking. We've already established that it happens.

On the subject of reading comprehension, did you completely miss the part about Toyota's system that appears to have almost completely eliminated the coking issue that was mentioned three times?

yeah, so....what's your point? I should go buy a Toyota then? No thanks.

My point is that SOMEONE HAS FIGURED OUT A WAY TO ALLEVIATE THE MAIN ISSUE WITH DI, which you claimed had not been done.

I'm done. I forgot what it was like trying to have a discussion with a wall.

 

[1BADSS396]

so why haven't the other automakers started doing it then Dan? If it's such an awesome "fix"?


It's a band-aid fix, that's why. And a costly one at that.

 

[mr_bots]

Wait, Jeff is an engineer too? That explains so much. [emoji38]

 

[1BADSS396]

I'm done. I forgot what it was like trying to argue with someone so much smarter than me.

FTFY