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Att dyno results

94turbo- said:
STANDARD ALL THE WAY! All the classifieds I saw while I was shopping for my 6.5 STANDARD said "fresh" or "rebuilt" or "new AUTOMATIC transmission" Standards won't make you feel like your in a minefield with booms and bangs, shifting hard enough to bruise kidneys, leak oil for no reason then stop, shift into four low first gear and stay there for hours, then shift fine. Clutches can be fixed easily, Auto's require a grand just to be up on a hoist.
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manuals arent bulletproof either. boss just snapped the output shaft on his NV4500. he was loaded to 30-35K combination though on a stock tranny.... :)

we have a few NV4500s on the farm that have an issue of some sort, so they arent problem free, its just that they are less problematic IMO.
 
I'll stick with my automatic also. Didn't know the 4L80's had that many problems. Around here I see trucks with 4L80E's over 200K and trans has never been apart.
 
1999gmc said:
I'll stick with my automatic also. Didn't know the 4L80's had that many problems. Around here I see trucks with 4L80E's over 200K and trans has never been apart.
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Not to turn this into a transmission thread (although it seems to be slowly going there), but my 4l80E has 427,000 KMs on it and it doesn't miss a beat. Those aren't running back and forth to wally mart, my truck has been worked hard in it's life (past maxed out payloads).

That's around 265,000 miles for those south of 49....

;)
 
6.5L said:
Max boost with the new housing now is 15-16psi max, and that is unloaded. Loaded, I managed to hit 18psi on a hill but in this housing, boost doesnt shift that much between loaded and unloaded. At least with me it didn't. Either way, the thing is like a rocket ship! I can't wait to see what it does on the dyno
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That's a decent amount of boost. Now all you need is some more fuel and some head studs. To push up power further. And maybe a cam swap. :D
 
Motor smokes a little bit at first then the turbo lights and there's nothing. I can take a video one of these days of it now for you guys if you want. Cam swap won't be needed I don't think. I believe the stock cam is actually pretty effective between idle-3500. But more fueling may be in the future. i don't know yet. If I do though, it won't be but maybe 1/16-1/8 turn, if I even do it. I am kind happy with the 20mpg I am getting right now
 
Heath Diesel sells a towing cam that would allow it to breathe even better down low. I just tend to think the stock cams can definitely be improved on. As far as adding more fuel, remember the mileage is controlled by your foot. You should be able to achieve 20mpg even with it turned up more IMO...
 
Yeah but with the fueling now, I am already at the limit of boost I feel safe running through my motor
 
Did you change precups on this engine to diamonds before dropping it in? Otherwise you may have 6.5 NA Precups that are smaller. Likely the same ones I have in my 1993 that had a rebuilt NA engine dropped in sometime in the past. Precups can limit the amount of fuel you use. I do not know if it gives me more MPG yet as the diesel bugs I am fighting have not allowed a fill up yet...

88 Ford said:
Plus more fuel will light that turbo quicker too which also could help mpg as well as power.
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More fuel would just smoke more. The larger turbo needs to be feathered on the throttle until RPM comes up. Then you can pour the fuel on. Electronic IP's can be tuned for this, the mechanical ones simply have to be tuned by your foot. I like to get smokeless starts then open it up.

The automatic transmission will shift at WOT and keep the engine at full load. This keeps your forward speed up and keeps the turbo loaded and at full boost. Modern vehicles reduce 'engine power' during a shift so the auto clutches/bands can lock instead of slipping.
 
Question on the diamond precups...where can you buy a set of 8? Or where is the best place to buy a set? Peninsular? Also, how much would they lower compression ratio when compared side by side to the stock 6.5 turbo 21.3:1 ratio precups?
 
I think the only 21.3:1 CR 6.5 out there would be the civilian NA engine with NA civilian precups, as I think the military NA precups were slightly larger. As soon as the precups started opening up for the turbo the CR started dropping. Some sources put the latest 506 blocks at 20.2:1 CR, which had diamond precups. So basically one point drop from NA 6.5 to latest diamond cup, and if you have any turbo cup inbetween, the CR would have been somewhere inbetween. A place like Peninsular or anyone that build them might have sets form old cracked heads. You might be able to get new AMG from Peninsular, or used ones, which I had asked them about in the past and said they could get me a set together. They might even have something larger for marine use.
 
Well, when the 6.5 debuted in 1992 with the increased displacement and turbocharger the compression ratio was 21.3:1 and that is according to my factory GM student training book (that you can sometimes pick up on Ebay). I wanna say that the ratio is 21.3:1 from 92-98 and then in the last 2-3 years it dropped to the 20.2:1 figure you stated. And then I'm sure military ratios on 6.2 engines differed from the civilian world, but you go to any older 6.2 diesel pre 1990 I do believe they were all at least 22:1 ratios (especially since they didn't have the turbochargers). I just picked up a 141 block that came out of a 1996 van. Is a 6.5 N/A engine and I am curious what compression ratio it is from the factory. I'm going to take a good guess and say it's likely 21.3:1 or maybe 21.5:1 Another question is did they lower the compression ratio from 21.3 to 20.2 with just the precup change or was it just pistons....or maybe both???
 
On the subject of tranny's (the ones in trucks)... I am 24 and with my stop and go driving checking fields I love my auto but I am ready to get my NV4500's rebuilt for towing/playing. Driving a stick I drive like a mad man at all times. In my experience if my clutch goes then I'm gonna kill the synchros because it always happens when towing or I needthe truck for something.
 
In 1992 they may not have differed precups in NA vs turbo trucks. Might have been a learning experience along the way to increase precup size and lower CR with precups. If the turbo version in 94+ were 21.3 in L56, then the L65 would be lower with bigger precups. Either way all of them have a slightly different CR based on the different precups from L49 to L56 to L65 engine versions that I know had different precups in 94.
 
So I have a question, how would the pre-cups keep me from burning all of that fuel? Wouldn't a smaller pre-cup help swirl better and therefore create better combustion and more power? I thought I heard somewhere that the bigger the pre-cups, the more smoke and EGT's you get? Some insight?
 
And I think the pre-cups are the standard NA square stamp military ones that came with the motor. Haven't swapped them.
 
6.5L said:
So I have a question, how would the pre-cups keep me from burning all of that fuel? Wouldn't a smaller pre-cup help swirl better and therefore create better combustion and more power? I thought I heard somewhere that the bigger the pre-cups, the more smoke and EGT's you get? Some insight?
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When the intake valve opens the precup is full of pressurized exhaust gases, which some will get pulled into the cylinder during the intake stroke, but then compressed back in there. The fuel needs to get out of the cup to mix with the larger volume of fresh air. If the mouth is so small the pressure of the combustion may not let all of the fuel come out of the precup to mix with fresh air. The larger the mouth the faster it can expand into the cylinder for mixing. The efficiency of swirling and smaller precup opening would be more critical when not having much boost. GM even sized the precup openings according to the amount of fuel the PCM programs were intended to put out. I don't think people with diamond cups have EGT issues, there are a lot of them out there.
 
do you think a swap from square stamps to diamond would help create more power? Would i sacrafice low end power with a larger precup when im not building boost
 
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