6.5 Precups - Power -OR- Economy?

[TurboDiverArt]

Any idea what kind of MPG we are talking about here? Is it .5 MPG or 2MPG? Just curious.

Art.

[Chevrolet4x4s]

Any idea what kind of MPG we are talking about here? Is it .5 MPG or 2MPG? Just curious.

Art.

I too would like to know how much the precups will improve it. And a set of theromastiacally controlled daul electric fans should pick up what 3mpg over the stock fly swatter?
Shane

[More Power]

The 6.2L and the 6.5TD longblocks are basically the same, with the exception of bore diameter and precups.

Assuming 3.73 gears, a 6.2 powered truck can deliver low 20's for fuel economy. With the same gearing, a 6.5 equipped truck can produce high teens. There could be 5-mpg difference. Some or most of which is, I believe, attributable to the precups.

GM once sold a 6.5L diesel engine named the "Fuel Miser". The only difference between that engine and a typical 6.5 is that the Miser used smaller port precups and just the rear cylinders received oil spray.

Jim

[Chevrolet4x4s]

which pre cups would be good for a mild to medium twin turbo intercooled 6.5 built for economy? Also what years did the 6.5s get roller cams?
Shane

[DmaxMaverick]

which pre cups would be good for a mild to medium twin turbo intercooled 6.5 built for economy? Also what years did the 6.5s get roller cams?
Shane

I'd suggest using 6.5 TD cups. The gain/risk with N/A cups won't wash.

6.2/6.5 engines have always had rollers.

[Chevrolet4x4s]

I'd suggest using 6.5 TD cups. The gain/risk with N/A cups won't wash.

6.2/6.5 engines have always had rollers.

Well I shouldnt have to pull the heads then.Glad to hear that its a roller cam.

Also which years of 6.5s had the 18 to 1 pistons and is there a casting number on the engine that will tell you if it is the 18 to one engine....Its a late 95 or a 96 engine
Thanks
Shane

[MaxPF]

No factory 6.5 ever had 18:1 compression. 6.2's and early 6.5's had 21.3:1 compression. Later they dropped the compression to 20.3:1. I don't remember when the change was made though...

[MaxPF]

I heard from a VERY reputable source that the problem with using small port precups on a turbo motor is that the cup will get excessively hot and you will get rapid erosion of the port. I wonder what material the precups are made of. They are simply called "stainless steel", but that covers a wide range of alloys, none of which are the best for a precup IMO. HD IDI's usually use a Nimonic alloy (similar to Inconel)... is that what the cups in the 6.x are that are reffered to "stainless steel", or is it some cheaper alloy...?

[More Power]

I heard from a VERY reputable source that the problem with using small port precups on a turbo motor is that the cup will get excessively hot and you will get rapid erosion of the port. I wonder what material the precups are made of. They are simply called "stainless steel", but that covers a wide range of alloys, none of which are the best for a precup IMO. HD IDI's usually use a Nimonic alloy (similar to Inconel)... is that what the cups in the 6.x are that are reffered to "stainless steel", or is it some cheaper alloy...?

The cups are, according to GM, stainless-steel.

I have a disassembled 6.2L engine in the shop that ran for 200,000 miles with a Banks turbo. The cups are no more worse for wear... Peninsular produced turbocharged marine 6.2L diesels from 1984 till 1991. There is no more reputable source than Pen, for info concerning turbocharged 6.2 precup life.

Jim