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4th Gen HP Peak

9K views 40 replies 13 participants last post by  catsltd 
#1 ·
Does anyone know at what rpm the 4th gen hemi makes its power peak? Is there a difference between what the manufacturer states and what someone has found on a chassis dyno? I've been playing with my WOT shift points on my Superchips tuner. Currently I have it set at 5950rpm, but it seems like I may be revving too far past my powerband.
 
#3 ·
my stock Ram, 2 dyno runs, first one you can see where it shifted
I hope someone can read it, because i am lost

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#5 ·
From your dyno results which are very close to mine.
Peak HP is at 5300 RPM:314:74 HP.
Peak tq is at 4400-4500 RPM:327:48 TQ.

There is no reason to raise max RPM above stock,unless your racing and your using 93+ octane gas cause your going to get some knock.
Looks to be a good 3rd gear dyno pull before it spiked and shifted into 4th gear.
 
#6 ·
I would change your WOT shifts to 5500 rpm...just above peak. By the time the trans shifts you'll still be in the meat of your torque/power band you won't risk over-revving it.

Like already stated it looks like peak hp is around 5300 and peak torque is around 4250-4500.
 
#8 ·
Thats about as high as Superchips works,before it starts producing a slower shift.
You need to raise your rev limiter also or else it wont shift.
I would raise it to at least 6100 RPM.if your going to be shifting at 5850 RPM.
I think Superchips has a safety feature to force you to raise the rev limiter before the shift RPM???.
I lower my tq managment also to help it shift quicker.
 
#9 ·
Going to make a few runs shifting at 5800rpm, then switch to 5500rpm and see if my ET and MPH picks up. Will keep you posted.
 
#11 ·
Exactly, looking at GTs chart and this one (can't remember where I downloadedd it...maybe from AEM) the HP hits a plateau at 5300 and the torque has already been dropping. Running your rpms much higher will only hurt your times. Only my opinion but shifting at 5500 would be ideal b/c it'll take the trans a split second to shift and the rpms will drop right back into the heart of the power band. Shift any lower than 5500 and by the time the trans shifts the rpms might drop too low in the power band. Shift any higher than 5500 and you are spending unnecessary time in the rpm range where power is dropping and it'll probably feel like the rpms are "hanging".

I'll post my dyno charts next thurs or friday and see what the curves look like. I'm having an Arrington cam installed and 2 tunes written. I finally gave in and bought the aFe stage II cai also.
 

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#12 ·
Well I tried 5800rpm and then 5500rpm shift points back to back and lost an average of one tenth at the 5500rpm setting. I think that the rpm is dropping too low between shifts (under 4000rpm) and I'm falling under my torque peak. I'm going to try raising it to 6000rpm and see what the outcome is. Some guys are reporting gains shifting as high as 6200rpm.
 
#13 ·
dustin, thanks for the feedback. nothing better than realworld results with these motors. I wonder if you hp keeps climbing (vice leveling off) due to the better breathing. I should've thought about your mods when looking at GTs dyno graph. Sorry for the bad advice.
 
#14 ·
Hey, no worries. I like experimenting with things like this! I'll let you guys know how the 6000rpm setting turns out.
 
#16 ·
The Nittos are awesome for wet and dry traction but suck in mud and snow. They barely spin off the line compared to the stock goodyears. I lose about a half second in the quarter due to the heavy 22's though.
 
#18 ·
I tried 6000rpm WOT shift points today. Dropped 2 tenths from the 5500rpm setting and also picked up 1-2 MPH. Runs were more consistent as well. 6200rpm setting is next.
 
#24 ·
I tried 6000rpm WOT shift points today. Dropped 2 tenths from the 5500rpm setting and also picked up 1-2 MPH. Runs were more consistent as well. 6200rpm setting is next.
What were the OEM shift points?

Just so I understand this......when you adjusted from OEM to 5500 rpm, your time was slower by a tenth?

When you switched from 5500 rpm to 6000....you went faster by 2 tenths....is that correct?
 
#23 ·
I started with 8% and now I'm at 6%. Shifts good, don't think I'd go any lower than 6%.
 
#29 · (Edited)
I've heard the first limit on the Hemis isn't the valvetrain but instead the harmonic balancer on the crank. It's been known to fail as low as 6400 rpm I've heard. That's why my rev limit will be set at 6300 when (if) they ever release a tuner.

Also, as far as setting shift points, to make a fairly accurate guess, some math would have to be done for each gear change, as well as knowing your peak horsepower. Each gear change may need to be made at different points in order to keep you nearest the peaks for the longest amount of time. Also, forget torque peak when drag racing. Hp peak is where you want to stay. And before anyone yells foul, remember HP is just torque relative to rpm.

In my case, my power peaked around 55-5600. This means the perfect shift from first to second would be around 62-6300. But wait, that's only assuming that the power drops off after peak at the same rate it rises to peak. That's probably not the case and if I had to guess, these trucks would probably do great shifting at 6500. I won't do it, but you guys feel free. :)
 
#30 ·
In my case, my power peaked around 55-5600. This means the perfect shift from first to second would be around 62-6300. But wait, that's only assuming that the power drops off after peak at the same rate it rises to peak. That's probably not the case and if I had to guess, these trucks would probably do great shifting at 6500. I won't do it, but you guys feel free. :)
Thank you for the info on the harmonic balancer. This is the first I've heard of that issue.

Above you mentioned your power peaked at 5500-5600, making your perfect shift point 6200-6300. How did you come to this conclusion?

I'm not disputing you, just trying to understand how you figured that was the optimal shift point.
 
#35 ·
not sure on the difference?
 
#36 ·
Guess that's what i get for posting before fully awake. SAE is what you want to see and is believed to be a closer representation to real world hp #s. STD #s would be higher. Sorry for my last post. Those are great numbers! How many psi did you peak at? Cant wait to see it with the stroker.
 
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