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Att dyno results

It would probably help to improve low end power with greater combustion at high torque angles. And would be better if ever planning to adjust fuel up any more. Its definately something I wouldn't skip if I had the heads off. I wouldn't necessarily take the heads off just to do it though. That is, unless I really needed more power or in hot pursuit of it.
 
Yeah, that's just the thing. I don't really want to remove the heads just to do it. Maybe this summer I will head stud it, and then warrant swapping the cups, but who knows.
 
So with all this precup talk, what did I do when I swapped out my heads from diamond to dot. I hadn't thought about it untill now. If the old cups didn't have all the cracks past the fire ring I most likely would have swapped them out.
 
I never wanted an automatic pickup until I drove an allison. All im gonna say on that topic.

6.5L....so as of now, which turbo housing are you the happiest with? I have the same nv4500 truck but with 3.73's, so I am interested to hear your opinion. And im gonna agree with buddy on wanting peak torque at lower RPMs. Unless im towing, my shifts are in the 2-2200 range. Im really not a fan of high-reving these motors. Just asking for trouble I think. More low end torque is what im after, and im sure our gear ratio differences have a large effect on that.

Thanks for sharing your numbers and findings btw. Impressive.

-Nick
 
Just a FYI.

I don't like to over rev these engines either, but, a shaft will twist at a given torque at a low rpm while at higher rpm it will handle the same torque just fine.

There is probably a happy medium in there.
 
I am running the smaller housing which I enjoy a lot. It lights at about 1700rpm for me. And I keep my motor fairly reved up. I am kind of a firm thinker that if you don't drive it like you stole it sometimes, it will break more often. Both pickups I have had I put through hell and rarely if ever had problems with them. Sometimes I think every motor needs to be pushed every so often. just my two cents.
 
65L I sure agree with you! I don't believe a diesel should just idle around either, they need to be pushed harder at times to keep things clean. I bought my truck from a fellow who idled it around town for 15 years, It had 135,000 km when I bought it. I changed the filters and oil right away. On a long highway trip I noted the boost would peg at 9 psi and drop quickly above 2400 rpm unloaded. I towed a trailer back with an s10 blazer on it, and the box was full of snowmobiles and such, I was pushing it quite hard.
By the end of the 400 mile trip the gauge hits 13 psi and now drops around 2500 rpm, the get up and go is much better as well, my mileage too has increased.
I've owned diesels since 1987 and I have always worked them, and when I didn't they acted like a jock with the coach away.....sluggish and out of shape.
 
I push mine hard a lot (it's just in my nature) and I haven't had a single problem yet with the motor or anything else. She runs strong. Like I said, I'm a firm believer
 
6.5L said:
I am running the smaller housing which I enjoy a lot. It lights at about 1700rpm for me. And I keep my motor fairly reved up. I am kind of a firm thinker that if you don't drive it like you stole it sometimes, it will break more often. Both pickups I have had I put through hell and rarely if ever had problems with them. Sometimes I think every motor needs to be pushed every so often. just my two cents.
Click to expand...

I push my 6.2 HARD, constantly see's over 3000 rpms, cruises over 2500 rpms on back roads, highway speeds push me over 3000 rpms
It just doesnt seem right to keep the rpms low, the 6.2/5 family are not to be grouped with any other diesel engine IMO,

And of course there is my top speed, 80 mph which is over 4000 rpms:hihi:
4.56 gear ratio, 265/75 tires th400 trans

But this is derailing the thread, good numbers 6.5!
 
thanks! And when im doing 70mph im at 2500rpm and on the interstate doing between 75 and 80 im at around 2700-2800rpm and the motor sounds like it could stay there all day. It loves it. And even doing 70mph im right around 20mpg. Its great
 
I love the performance of my '99 with the zATT. Mileage, now that's a different story. I did a check on my last road trip filling the tank to the brim and refilling to the brim. 483 miles for 33.05 gallons. 70% of that was going DOWN Owens Valley from Bishop which is a long gradual descent and I had the cruise control set at 70 mph. Then the last 125 miles we went up the back route to Big Bear Lake and down to Fullerton where I did about 40 miles of in town driving. That's less than 14 mpg vs the 16 to 17 mpg I'd see on my son's Suburban, which has the GM turbo and the 4.10 gears vs the 3.73 gears in my '99. I guess I'm the only one running an ATT who gets lousy mileage.
 
I am not sure why NMB2, but maybe it has something to do with head design or injectors or injector angle. Who knows. just my ideas. I am not super knowledgeable on this, I am sure someone will chime in with the correct answer. And my motor really has never seemed unresponsive below 1800rpm. I think you got to keep these old 6.5L's spinning up a bit higher in the RPM so they will really shine, and with my 4.10's and driving style, isnt a problem with me :)
 
I think alot of it has to do with available fuel, we get more HP by spinning faster mainly cause the IP puts out more fuel as it spins faster. to a point anyway. I have been following your build over on PSN and I'd have to at least partly agree with the latest comment about the precups limiting you.
 
Right around 4000 rpms something happens,not sure what it is. I noticed lower boost and drive psi helped some,and more timing. Timing makes the biggest difference,and lowers drive psi at the same time. At one point I had decent power up to 4700 rpms,but lost power and torque below 3000 rpms.
 
Could the lower torque be partly because you ran the bigger housing at the dyno? I do know that 6.2 and 6.5 Chevys do tend to have higher horsepower compared to torque when they are built up a bit too. Could it also be the cam profile maybe?
 
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