Ess G3 Dyno Dip Question

[Austin8341]

Hey everyone,
Does anyone know what could cause the dyno dips above 7300 rpm?

The first two pulls were back to back after idling for a while. The car then sat for about 15 minutes to cool before the last pull. It was about 85 degrees at 500ft.

Ess G3 on 120 mm pulley
E85
ID1050x
Sai li dual pump return set at 45 psi hot
Catless texas speed 1-7/8 long tubes
Lund tuned

I’ve seen similar dips on some other ess graphs, but some are linear. Is this something you would worry about or is it normal for an ess power curve? I haven’t put it on another dyno, but it’s probably the the best thing to do for confirmation. Just wondering if anyone has input.

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[SheepDog]

Did you log the pull? There's a dozen things that could cause that dip

 

[Austin8341]

Did you log the pull? There's a dozen things that could cause that dip

I didn't. I completely forgot until I left. I’m really looking to see if it is normal to fall after 7300 with an ess and if it’s not, then I’ll dyno again and log this time.

 

[SheepDog]

I didn't. I completely forgot until I left. I’m really looking to see if it is normal to fall after 7300 with an ess and if it’s not, then I’ll dyno again and log this time.

As long as you have the fuel, it should stay pretty linear all the way to redline and beyond. a 120mm pulley isn't overspinning the blower at 7300 RPM engine speed. Without a log, you wouldn't know if it were knock related, if maybe you backed off the throttle a little, tire spin, etc. or its just Lunds crappy tune

 

[Austin8341]

Thanks for the input. It is just guessing without a log. I’m honestly thinking it may be tire spin. The first two pulls had what looked and smelled like tire smoke, but I thought it was just the dyno being a few months old. They tightened the straps before the last pull and I don’t remember seeing any smoke on the last pull. I have done many highway wot pulls on the same tune while logging and didn’t see any knock. I’m gonna have to just dyno again while logging to know.

 

[SheepDog]

Thanks for the input. It is just guessing without a log. I’m honestly thinking it may be tire spin. The first two pulls had what looked and smelled like tire smoke, but I thought it was just the dyno being a few months old. They tightened the straps before the last pull and I don’t remember seeing any smoke on the last pull. I have done many highway wot pulls on the same tune while logging and didn’t see any knock. I’m gonna have to just dyno again while logging to know.

Is your car manual or auto trans?

 

[Austin8341]

Is your car manual or auto trans?

Auto. It was in 7th for the dyno.

 

[Brevin]

Auto. It was in 7th for the dyno.

6th gear is normally what you dyno your car in with the 10R80. 7th is 1:1 ratio but will see very high drum speed on the dyno. Also not good to use 7th gear under power with the 10R80 as it is the weakest gear and can/will cause damage to those clutches. Many variables can cause power drop off, most commonly in the summer is poor airflow through the intercooler on the dyno and the IAT’s climb and the car pulls timing up top. Get a log and dyno again in 6th gear.

 

[engineermike]

@Brevin is right. Also rolling resistance increases dramatically at high speeds. My dyno graph rolled over up top in 7th due to rolling resistance, but didn’t in 6th.

 

[SloppyTX]

Check the plugs.

 

[Lonniesgt]

Just curious. Isn't tq and hp suppose to intersect at 5250 rpm. Is something off with the graph?

Here's my whipple car for reference.

 

[Austin8341]

Just curious. Isn't tq and hp suppose to intersect at 5250 rpm. Is something off with the graph?

Here's my whipple car for reference.

Not sure if it supposed to at 5250. Mine looks to intersect around 5600. You can see that the hp and torque are scaled differently. Right side scale shows torque on my graph.

 

[Lonniesgt]

Not sure if it supposed to at 5250. Mine looks to intersect around 5600. You can see that the hp and torque are scaled differently. Right side scale shows torque on my graph.

Oh yeah. Maybe that's why it's different.

 

[HKusp]

Just curious. Isn't tq and hp suppose to intersect at 5250 rpm. Is something off with the graph?

Here's my whipple car for reference.

Good catch. Something is off.

From this article:
https://www.enginelabs.com/engine-t...y-does-a-dyno-graph-always-cross-at-5252-rpm/

If you’ve seen a dyno graph more than once in your life, you’ve likely noticed that horsepower and torque always seem to cross around 5,200 rpm, regardless of combination or engine type. That’s not some fluke, because horsepower and torque do, in fact, cross at exactly 5,252 rpm. It’s not magic or witchcraft, but rather simple math. We’ll explain.

The mathematical equation for horsepower is torque times RPM, divided by 5,252. If you are familiar with algebraic expressions, you have probably already picked up why the lines of the dyno graph cross at 5,252 rpm. In the horsepower equation, when RPM equals 5,252, dividing it by the constant gives us a value of 1. So simplifying that equation for that specific RPM means that at 5,252 rpm, horsepower equals torque. (If you’re a pedantic math nerd, it actually means that horsepower equals torque, times 1, divided by one.)


So, we’ve answered why they always cross, but you might have picked up on something else… why is there an equation for horsepower? Aren’t we measuring it on the dyno? The answer to that question might surprise you. No, we aren’t directly measuring horsepower on the dyno. We are directly measuring torque, and then calculating horsepower using the torque measurement and engine RPM.


That leads us further down the mathematical rabbit hole. If all that is true, then below 5,252 rpm torque will always be greater than horsepower, and above 5,252 rpm, horsepower will always be greater than torque. But, again, why? That all comes down to the variable of time.

 

[robvas]

Dyno operator should be punched for having the graph setup like that

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