LT1 or LSX?

[Obsin71Ls1]

Originally Posted by Vegas69

. Anytime you add complexity, you decrease reliability.

The same was said when GM went from the proven Gen I/II SBC to the gen III. Direct fuel injection is not anything new and certainly not a cause for concern with regard to reliability.

[Efi69Cam]

I don't buy the reliabiliy argument against DI. High pressure DI pumps have been used on diesel engines for a long time.

As Mike said what is going to slow the use of these engines in the hot rod market is the aftermarket support. From what I've read so far the new ECM is locked up pretty tight. That's not say the aftermarket will not step up but it will be awhile.

[kainedogg]

I can't even afford a crate LS7 yet. I shudder to think what this new motor will cost. On the other hand, if the direct injection allows me to run a lot of boost, with a lot of compression, then when it's tossed into an affordable vehicle (Camaro Z28 LT1 ) I might buy it.

[WSSix]

Originally Posted by Obsin71Ls1

The same was said when GM went from the proven Gen I/II SBC to the gen III. Direct fuel injection is not anything new and certainly not a cause for concern with regard to reliability.

GM's had direct injection on the V6 CTS for a while now. I'm unaware of any major issues with that system. I'm with you, I seriously doubt there will be any major reliability issues with the design.

[Vegas69]

Time will tell....

I did a quick search and one thing I found is pretty interesting. On a direct injection engine, the intake valve never see's any fuel but they do see dirt, combustion vapor(Oil), and oil from the valve guide. The additives in fuel help keep the back of the valve clean in non direct injected engines. This could lead to drivability issues and additional maintenence.

I also noticed that some direct injected CTS engines suffered timing chain problems. The lobe on the camshaft for the high pressure pump will increase the load and frequency on the chain.

[MarkM66]

Yeah, DI has been around awhile in gas engines, and so have the problems Todds post states. Not to mention that second fuel pump that's extremely loud , and make the engine sound like a diesel when running, IMO.

[GRob]

Originally Posted by Vegas69

Time will tell....

I did a quick search and one thing I found is pretty interesting. On a direct injection engine, the intake valve never see's any fuel but they do see dirt, combustion vapor(Oil), and oil from the valve guide. The additives in fuel help keep the back of the valve clean in non direct injected engines. This could lead to drivability issues and additional maintenence.

I also noticed that some direct injected CTS engines suffered timing chain problems. The lobe on the camshaft for the high pressure pump will increase the load and frequency on the chain.

While this has been true in the past (Audi RS4 anyone?), I believe that this problem is for the most part solved on the current gen DI engines - but yes, it could be a potential issue for sure.

[Stuart Adams]

Interesting topic. It will be cool to see what shakes out down the road.