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Just needs some answers

6.5L

6.5L

Old Iron Runner
Messages
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Location
Northwest Wyoming
Ok. I have been wondering this for a while, and maybe I am missing something, so feel free to jump right in, but why does the 6.5L not create predictable torque. Like my motor dyno'd at 203rwhp and 331ft lbs of torque. I mean, in theory, shouldn't my torque be up around 375-380ft lbs for a diesel. Is it just because of the whole IDI thing? I see other Ford IDI's dyno and they create close to a 2:1 torque to horsepower ratio. I was just wondering what the idea was behind that. Or if anybody could explain in SIMPLE AS POSSIBLE terms for me. Because it has been bugging me why this happens. Any and all info is welcome.
 
ALOT of it has to do with how your fueling comes in. I know that for teh DURAMAX many will dyno around the 2:1 ratio, but the same truck with a different tune will dyno alot closer to 1.5:1 if they bring the fuel in later on. Big torque numbers are normally atributed to more fuel down lower in teh RPM range where a diesel makes teh most torque, so if you don't fuel hard until higher up in the RPM range your torque number will be down. And also alot of dyno's cannot fully load a diesel hard enough down low in the RPM range to get an accurate torque reading since the engine won't be fully loaded. And if teh RPM reading isn't dead on with the dyno the torque number will also be way off. There are just to many variables when it comes to a dyno to see the magic 2:1 ratio all the time even if your engine is making it. Just remember a dyno is a tuning tool, nothing more. And take teh numbers and use them for tuning, but the real world numbers may be differrent.
 
I know it aint going to be the fabled 2:1 ratio perfect. I just thought it would be a little closer than the 1.6 ratio I am running. Is there any way to "fuel harder" down low so I can bring the torque up a little? My truck is seeing a lot of fuel down low but just can't get the air in enough to burn it. I can be at 1100rpm and floor it and it starts moving and blows a lot of smoke but it doesn't start really go anywhere until my turbo starts building boost which isn't until 1900-2000rpm. Like it's noticable enough that you can feel exactly when the turbo lights. I didn't make peak torque on the dyno until like 2700rpm. If I make torque that high instead of down low, wouldn't the torque number be up since I am fueling a good about the high in the RPM range. The 7.3L IDI video's I see on youtube use the same pump I do. So you think fueling would be the same. And they create closer to the 2:1 than I am running. Is it in the injectors or do they use the same style injector? I know I am asking a lot of questions. I am just wondering. I am still kind of stupid when it comes to this truck.
 
The DB2 pumps seem to cut fuel after 2500 rpms. They will do this even with no governor. At higher rpms there is not enough time to get the plungers filled. The DS4 has full pressure to the plungers all the time,this helps for higher rpm fueling. I guess it would be nice to have max torque down low,but it is harder on every thing . Mine seems to have 0 power under 2000 rpms also. This makes the gearing feel too high.
 
Is there anyway to get the plungers filled faster at higher RPM? I don't notice any fueling loss above 2500rpm. I imagine if I would that my boost would come down but it holds max boost until 3100rpm and then from there to 4000rpm it will only slightly drop PSI. Maybe 3psi total. Not a huge drop considering I normally run 15psi and 18max. At least I don't think so. Ya know I got to thinking, the 6.5L was definately not made to make competitive power. And yet, it is still possible to make a lot of horsepower (for a 6.5L) off a relatively small amount of fuel that goes into it. So there are people out there that are figuring out every little thing with these motors. And it has created what I think is one of the most creative abundance of power and relability idea's for any motor. Which I think is just great!
 
Where was your peak hp and peak tq numbers at in the rpm range ??

Correct me if I'm wrong, but as I recall / have read on these forums, the ATT with it's bigger non gated housing comes on just a tad later in the rpm's maybe more so for towing in a lil higher rpm range. That would be my guess as to why you might not be seeing higher tq numbers lower in the rpm range. Maybe try a GM 8 and see if you don't have higher tq numbers off idle, or just below your 2,000 rpm range.

The hp numbers will be lower at lower rpm's, but you might get the tq numbers up with a smaller quicker spooling turbo hence seeing closer to the 2 : 1 range you are wanting.

Remember, I'm kinda diesel retarded and shooting from the hip here.....

Mike
 
203rwhp at 3800rpm. 331ft lbs. at 2800rpm. and I know in my signiture it says I am using a ATT but it is currently off right now and sitting in the shop. Long story. Just got to find time to put it on. I should have a chance soon if I get a break from college for Halloween. If not, then my Thanksgiving break it will be going on. When I dyno'd my truck, I had the stock GM-3 on set at 15psi.
 
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