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PROPERTY U.S. GOVERNMENT
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Discussion Starter #1
Good morning everyone!

I’m putting the bronco on the dyno today and we’re tuning it. With that being said, the dyno needs to be done in 3rd gear (1:1 ratio). Now, I was going down the highway once, and with the pedal to the metal, and it seemed that the truck was bottoming out at around 85-90, pulling approximately 4000 or so RPM.

My question is, will it bottom out when the wheels and transmission hit 85, or will something be different on the dyno to where they can run the full power band of the motor?
 

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Ford Hoarder
78 & 92
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6,503 Posts
no wind resistance, only the load put on the drivetrain from the dyno. So you should be able to tune it to your desired rpm range. Unless something is mismatched in the build and you stop making any power at 4k rpm, which could be the case...
Not saying not to use a dyno for tuning, but this is an instance where they can not really show the whole truth. Just something to be aware of.
 

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Addicted to Junk
85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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Beat me to it!
 

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PROPERTY U.S. GOVERNMENT
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190 Posts
Discussion Starter #4
no wind resistance, only the load put on the drivetrain from the dyno. So you should be able to tune it to your desired rpm range. Unless something is mismatched in the build and you stop making any power at 4k rpm, which could be the case...
Not saying not to use a dyno for tuning, but this is an instance where they can not really show the whole truth. Just something to be aware of.
True. What I’m saying, it’ll sing and go up to 6200 in 1st gear, but in 3rd, it seems that the transmission limits the speed at 85-90 and the motor is turning around 4k at that time. I’m just trying to see around a ballpark of what it would make, you know?
 

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Ford Hoarder
78 & 92
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Dyno should give you good idea of what is going on. Just a guess with the limited info in this thread, maybe runnning out of fuel on the top end, with the extra load of 3rd gear. I would also try to verify what the timing is doing as well. I know expensive, hopefully dyno has one, a wideband would tell you right away a good idea of what issue is.

The C6 does not have anything to limit speed in it, at least not normally functioning.
 

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PROPERTY U.S. GOVERNMENT
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Discussion Starter #6
Ok, so the numbers almost make me ashamed to post them, but this was a rather stock rebuild.

174.14 HP
215.68 FT/LB
...at the rear wheels.

Way below my expectations, but realistically speaking, the 215 HP version of the ‘95 Mustang made... you guessed it, 215 HP and 285 LB/FT at the crank. Not only that, but the C6 is also up to 25%parasitic to power. Ok, done making excuses 😁

Outcome is that I still gained +1 HP and +5 FT/LB, and lowered the AFR a good bit (was way too lean) just by retarding the timing and putting 3 size bigger jets in. Oh yeah, also, the tech let off at 4850 according to the graph, so there is no governing feature on that C6.
 

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What's the deal with the 4K max in 3rd?
I don't understand why you would tune something that sounds like it has major issues, instead of fixing the issue first?
 

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@84Bronco thanks for posting those numbers. It's good to get real info, helps curb unrealistic expectations.
 

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PROPERTY U.S. GOVERNMENT
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Discussion Starter #9
What's the deal with the 4K max in 3rd?
I don't understand why you would tune something that sounds like it has major issues, instead of fixing the issue first?
There isn’t a max, that’s just the way it felt out on the road. He got the tires to spin up to 110 MPH I’m pretty sure, but he let off of the gas once peak had passed. There just wasn’t a point in pushing the motor even harder when it’s already made it’s most power...
 

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PROPERTY U.S. GOVERNMENT
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Discussion Starter #10
@84Bronco thanks for posting those numbers. It's good to get real info, helps curb unrealistic expectations.
No problem, reality really stepped in when I saw that computer read those numbers, lol. But the more I think about it, that 175 HP & 215 ft/lb get that 5000 lb. truck down the road pretty well, saying it’s an engine designed to carry approximately 3300 lbs...
 

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Would you post your results in the board dyno thread, please?
Along with technical details of your engine build (what makes it different than stock).

 
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