18 to 1 comp fuel economy vs stock comp

[Vin82k3500]

has anyone compared the fuel economy of the 18 to 1 6.5 td engine vs the stock compression ratio I am currently swapping in an n/a 6.2 in a 92 pickup the guy wants to either build or buy an 18 to 1 6.5 but is curious of fuel economy I am not sure he will get over 19 but I am not sure and I did tell him I would say 19 but I dont know for sure hes got a half ton with 3.42s I think the n/a 6.2 is gonna serve him very well in that half ton or maybey id just toss a stock gm turbo setup on it to make it a little quicker off the line and hed still get great fuel mileage but oh know guess what he says he wants to play 37 years old youd think he out grew that at least a few years ago I outgrew playing in my late 20s oh but I forgot I fix busted cars and trucks for a livinganyway just seeing if anyone has compared economy or an 18 to 1 enigne vs the stock comression ratio.

[More Power]

has anyone compared the fuel economy of the 18 to 1 6.5 td engine vs the stock compression ratio I am currently swapping in an n/a 6.2 in a 92 pickup the guy wants to either build or buy an 18 to 1 6.5 but is curious of fuel economy I am not sure he will get over 19 but I am not sure and I did tell him I would say 19 but I dont know for sure hes got a half ton with 3.42s I think the n/a 6.2 is gonna serve him very well in that half ton or maybey id just toss a stock gm turbo setup on it to make it a little quicker off the line and hed still get great fuel mileage but oh know guess what he says he wants to play 37 years old youd think he out grew that at least a few years ago I outgrew playing in my late 20s oh but I forgot I fix busted cars and trucks for a livinganyway just seeing if anyone has compared economy or an 18 to 1 enigne vs the stock comression ratio.

If he's building a hot-rod, a performance-oriented engine, then 18:1 could be a good choice. On the other hand, if this half-ton truck with 3.42 gears will be a daily driver with an emphasis on fuel economy and easy start-ability during the winter months, the stock CR might be a better choice.

The 18:1 Project 6.5 featured here in The Diesel Page was installed in a 2500 series 4WD HD pickup equipped with 4.10 gearing. It was used for heavy towing. Even with the 4.10 gearing, routine fuel economy was in the range on 16-18 during local driving and another 1-2 mpg while traveling unloaded on the Interstate. The best-ever hand calculated fuel economy was 21-mpg, but that was a unique situation and road trip (Lolo Montana to Lewiston, Idaho, about 200 miles on a slower winding 2-lane).

That 18:1 engine got the best of everything at the time it was built, including a careful rebuilding and assembly, competition balancing, new marine fuel injection system, 4" exhaust system, DSG gear drive timing set and a somewhat advanced injection timing. A turbo more suited to the needs of the engine might have improved things even more. The GM-8 wasn't enough turbo. 18:1 engines don't like northern winters. Cold starts can be improved by using the block heater and longer glow times.

Of the stock 6.5L diesels I've driven or heard about, I'd say the fuel economy for our 18:1 is as good or a little better. So, it's not necessarily a detriment to fuel economy when running 18"1 CR.

I'm in the process of assembling another 6.5 project engine. This one is an electronic engine and will get stock CR pistons and small port precups, in part as a fuel economy investigation. It'll also get a DSG gear drive, Fluidampr and possibly another turbocharger. I have extensive fuel economy data for this vehicle in its stock form, so I'll learn what helps.

Jim

[Vin82k3500]

Thank you Jim I was on the right track with what I told him and I did assume that cold starts would not be in his favor his ego is a little bigger than his wallet the fuel economy isnt all bas as you report with yours but as we know yours was built to exact standards that this guy wont come close to I think hes better off with a stock 6.2 or 6.5 with a gm turbo he dont need mods it used to be my truck I think him and a build are a catastrophe waiting to happen I cant wait to see more on your next 6.5 build thanks again he can keep his eyes off my freshly machined block and 18 to 1 pistons that I was gonna make a pulling engine with.

[lilymonster]

Jim, glad to hear you are still at it and working on a new project. Excited to read your write ups on it.