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5.7L Hemi Dyno Results

4

440sixpack

Senior member
OK, there were a few people here interested in seeing this so I'll post it as promised.

For a bit of background, the stock truck as received has a computer speed limiter at 105 mph, which will not allow a full pull (that's only 4400 RPM @ 105, and the peak power is supposed to come in around 5400 RPM). However, the limiter can be bypassed by pulling the ABS fuse, which will allow a full pull, with the downside being the speedometer not working, and the trans will stop shifting shortly.

Anyway, I did 3 runs with the limiter in place, and one without. Honestly, the results are not what I was expecting, and others have tried this trick as well and got some better numbers, but it appears above 4400 RPM, even without the limiter, the computer is still holding things back somehow, as the power peak is not where is should be.

Anyway, enough blathering, results w/limiter were 232.0 HP and 282.3 Ft.-Lbs.
w/out limiter: 247.0 HP and 299.3 Ft.-Lbs. (was expecting somewhere in the 260's for HP)

Note it was rather humid that day, and a lot of other guys weren't pleased with their results either.

One other thing:

***WARNING***

I want to make one thing very clear. With the speed limiter bypassed, and my 3.55 rear end and 265/70 GY Wrangler tires, I was up around 142 mph at 5600 RPM. THESE TIRES ARE NOT SPEED RATED FOR THAT, AND I CAME VERY CLOSE TO BLOWING THEM OUT. Nothing inspires a panicked burst of adrenaline like the dyno operator yelling "WHOA, WHOA, LET OFF, LET OFF!!!!" I was told at that speed the tires were buckling like a funny car's, they almost collapsed. So if anyone else is going to bypass the limiter, or just drive at excessive speeds in general, please bear in mind the safety limits of your tires.

Dyno Chart
 
Yeah, I was expecting more like 260's/320. Oh, probably should have specified it's bone stock and has 2400 miles on it. Yeah, that's it, it's not fully broken in yet... 😉
 
Is pulling the ABS fuse the only way to disable it? I saw a video of a Hemi-powered Ram racing a Lightning, with the Hemi coming in about 1.3 slower in the 1/4 mile - he got over 105 from what I remember

And aren't the crank numbers like 345/375 or something? And what gear did you pull on?
 
As far as I know, the fuse trick is the only way around it, unless you modify the computer somehow. I was in 3rd (1:1), and yes you are correct on the claimed crank numbers. Some people say with the 4x4 there's more parasitic loss due to the transfer case, but a mopar tech said that would be more noticeable on the drag strip, not the dyno.
 
The numbers are a little low... thats kind of strange.... put a Supercharger on there and you'll beat notfreds numbers. (lets see the garbage stock 5.0L numbers)
 
Heh, not yet for 400, gotta wait for the, erm, uhhh, crap now I forget, Chrysler showed some concept with a 430 hp supercharged hemi. Ah, I'll save my pennies and SC mine someday... Or forget making the truck fast and put money into the Challenger - now that car I could show some numbers on. 😀
 
Is pulling the ABS fuse the only way to disable it? I saw a video of a Hemi-powered Ram racing a Lightning, with the Hemi coming in about 1.3 slower in the 1/4 mile - he got over 105 from what I remember
Click to expand...
Its the only 'easy' and 'free' way as of yet, until some company like Hypertech comes up with an ECM chip/mod.
 
And keep it streetable? Yeah I guess so. Remember, this is not the Hemi of old. 🙂 I'm sure it'll go up as they refine the design, keeping some in the wings to respond as the competition does I assume.
 
Originally posted by: 440sixpack
Heh, not yet for 400, gotta wait for the, erm, uhhh, crap now I forget, Chrysler showed some concept with a 430 hp supercharged hemi. Ah, I'll save my pennies and SC mine someday... Or forget making the truck fast and put money into the Challenger - now that car I could show some numbers on. 😀
Click to expand...
Sadly I think Kenne Belle is gonna be your only hope for a truck blower... Kenne was cool, but that place can go to hell since his asshat brother took over :disgust: If you do get one, do it right... that boost-a-pump crap and their other short cuts are a bunch of $h!t.. go by a inline T-rex... oh and have fun pullin SIXTEEN plugs every season to check em 😉
 
Supposedly Mopar is going to come out with one, warranty and all. This is from a story in the Chicago Tribune on 3/31:

"Mopar is working on some mods, including a supercharger. It also plans to offer a crate motor, a perfomance engine sold by the factory complete with a warranty.

The supercharger kit will come with an adjustable PCM (that can be reprogrammed with a PC), an after-the-converter exhaust system and a modified cold-air intake system. And, since the combustion chamber pressure will increase significantly, the engine will require dished pistons."

As always, I'll say "wait and see" on this though. 🙂
 
Those numbers seem pretty good to me considering all the factors involved. I think any or all might contribute to the 10% deficiency in what you expected, or it might just be normal as LAUST pointed out with regard to the torque number.

1. weather as you stated wasn't ideal.
2. automatic transmission
3. 4x4
4. high final drive ratio maybe magnifies inaccuracies of this method of getting HP numbers.
5. not sure but I read somewhere the quad cab has an additinal drive shaft connection
6. just a theory but since I don't know why removing the ABS fuse removes the speed limiter, and makes the transmission not shift ?, maybe it's altering other things in the computer too.
7. gasoline octane- if you mentioned what you used it I must have overlooked it but I assume you were running 89 octane and not regular ?
8. 2500 miles, might still be tight, or it might be slightly out of tune by that time.
9. variations in operation of the dyno. Don't know if it's a factor or not but it might be hard to compare results from different dynos in different parts of the country operated by different people ?
 
You might try doing the Dyno in 3rd (instead of OD) to reduce the drive train losses encountered by the overly fast speed (not to mention the tire issue), and someone calculated a 28% loss from claimed, which for a 4WD is said to be about on par (as you're turning the transfer case as well)
 
A 5.7 liter motor can only come up with that much HP?? Ugh! My 1.8 liter comes up with 140 HP. I would think that with 5.7 it would be around 350-400 HP. WTF?
 
Originally posted by: Chadder007
A 5.7 liter motor can only come up with that much HP?? Ugh! My 1.8 liter comes up with 140 HP. I would think that with 5.7 it would be around 350-400 HP. WTF?
Click to expand...

140hp to the wheels with 4wd and is an auto?
 
NE Dyno is in Worcester, MA, this is their site. ALthough the next day I found out there is a dyno a lot closer to me than that. 🙂

I was in 3rd (O/D disabled) and yes it was 89 octane. I thought it was kinda weird that the TQ was right on at 20% loss but hp was at 28.5%. There must be something else going on in the computer, plus the tire thing.

Oh yeah, and as for the tranny not shifting, I guess if you pull the fuse, after a handful of shifts the tranny will just stay in one gear until the fuse is replaced.
 
Remember, this is a truck engine, it can't be as high-winding as a car's engine. You've got to keep enough torque down low to tow, haul loads, etc. Also bear in mind that this is the first year of this engine, I am sure they are holding back some so they can respond as the competition does. And as noted there's a lot more parasitic loss on an auto 4x4 than you'll see on most cars.
 
Originally posted by: Chadder007
A 5.7 liter motor can only come up with that much HP?? Ugh! My 1.8 liter comes up with 140 HP. I would think that with 5.7 it would be around 350-400 HP. WTF?
Click to expand...

See above post, the dyno is reporting power at the rear wheels. The 5.7L is rated 345 hp / 375 ft.-lbs. at the crank.
 
thats horrible,
honda s2000 makes the same hp outta 2.0 liter... my turbo i4 makes that much as well. (at its current state maybe 240hp at all the wheels ...awd)


240 hp laughably pathetic for a 5.6l v8 , its an insult to the 'hemi' name. (71 426 hemi cuda puts out nearly 400 hp stock)


EDIT: READ MY LIPS...MY CAR IS AWD also nissan skyline is awd and makes nearly 300hp outat 3.0l i6
 
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