Compression Ratio

[92F350CC]

I've been wondering, why do our IDI's have such trouble with low compression when the GM 6.2/6.5 do fine on 18:1?

 

[flatlander]

I've been wondering, why do our IDI's have such trouble with low compression when the GM 6.2/6.5 do fine on 18:1?

Do they?

 

[dairieman36]

i've heard never seen tho a 6.5 tt with @ 400hp

 

[tractorman86]

twins and 400 is all it could muster

 

[FordGuy100]

twins and 400 is all it could muster

Thats more than we are pushing....


I have no idea why they start that good. Honestly I think they start about the same as our IDI's, but like you said they have lower compression. Different PC design maybe?

 

[Diesel JD]

They don't have lower compression in stock trim, but there is a rebuild kit that puts the CR at 18 or 18.5:1 for the 6.5. I bet a 6.9 would do just fine at 18 or 19:1 with good glow plugs or the block heater. What CR was Ken's that was such a **** to start?

 

[92F350CC]

Ken's was either 18:1 or 18.5:1

I'm fairly certain that turbo 6.5's came with 18:1 from the factory.

 

[FordGuy100]

This is what I say for a low compression IDI. Move all the batteries to the bed, install 4 1000CCA batteries back there, all wired together. Then build yourself some sort of grid heater, and put it on a toggle swith. The put the glow plugs on a toggle switch. Run the grid heater for 1 minute, and glow plugs for 10 seconds, turn both off and turn over. I say it would work pretty good. If not, ditch what I said above ,dont run glow plugs, and just do the ole' give it a squirt of either, throw the can on the ground, run around the hood and into the cab, and turn it over .

I would say my first idea would be better though. Plus then, with the batteries in the back, you will have more room to put things in there, like twin turbo's, where the batteries sat .

 

[Hyde]

Kens was at 17:1 just FYI
http://www.dieselwarden.net/temp/69at17compratio.wav

 

[Diesel JD]

I must eat crow, I looked up the specs on the 6.5TD and it is 18:1. I just assumed it was the same as the 6.2s which were 21.5:1. Does anybody know for sure that 18.5:1 or 18:1 on a 6.9 won't work? Do we really know that lack of compression was Ken's problem, did he really do the build right? If a 6.5 or a 6.2 can run at 18:1 I believe a 6.9 can as well. It would be a good question for towcat since he's seen the guts of both these engines.

 

[92F350CC]

I just realized that the 6.2/6.5 are oversquare/shortstroke motors, which IIRC are more tolerant of lower compression.

It's also, i think, why they can spin to a higher RPM.

 

[Hyde]

The 6.2/5's do make their power and torque numbers at higher rpm than we do, 3600 and 2000 respectively for the 6.2. If you really want to know you could find out for us, no one else here would mind knowing although I think you'll learn that it wont be very easy starting. Imagine the guy with the 900HP IDI running 9:1!

 

[Agnem]

Saw an 04' Dodge make 1024HP and 1130 foot pounds on the dyno with drugs last weekend. I don't know how many times it will do that, or what it cost to get it to that point, but I doubt it will do that for very long! I'm afraid a 900hp IDI is probably out of the question.

 

[tractorman86]

Thats more than we are pushing....


I have no idea why they start that good. Honestly I think they start about the same as our IDI's, but like you said they have lower compression. Different PC design maybe?

with a descent twin turbo setup and adequate fuel i think we would be much higher than 400hp

 

[Hyde]

Well its not out of the question but its not practical. It has been done