yea, the graph does look bumpy for a vortech. It should be much more linear. Hopefuly your A/F isn't as bumpy.

 

liche, all,

I have a couple of questions on the dyno graph you've posted.

1. why doesn't Torque and HP cross at 5252 rpm

2. Shouldn't the hp be ~160 at 3000 rpm, using the torque of ~280 from the graph? hp = torque * (rpm/5252)

I know this post is a bit out of the blue, but I was trying to understand the performance differences between s/c and turbos through the rpm range when I came across this.

Jason

 

I don't know much about how they set up the dynopack to do this? Whether they put their own calibration constants for calculating HP or whatever. Anyways, its going back for retune once i put some HFCs on the car, and then i'll hopefully get a better tune (can read A/F directly from bung on HFC rather than through tailpipe) and also going to look at some misfiring issues i had.

Also, i plan to get a dyno run on a dynojet after that as well, just so i have some sort of baseline on each (realizing that they are NOT going to the same with regards to numbers, but the trends should be the same)

 

Because of the formula used to derive HP from torque at a given RPM. If you look at what was posted above, at 5252 rpms, TQ should always equal HP.

 

Hi Liche,

As Coupe said, the dyno graphs always (that I understand and seen) cross at 5252 because of how horsepower is determined in an engine: HP = torque * (rpm/5252). When rpm is 5252, the fraction is 1, so HP equals Torque, the crossing point. Wikipedia has a pretty interesting bit on this: http://en.wikipedia.org/wiki/Horsepower . You can skip down to the section "Relationship with Torque", about half way down for the equation. The history bit is interesting... James Watt coining the term "horsepower" as a way to market steam engines against horses.

 

^^ +1

I have always used the rule of thumb...if the tq doesn't cross the hp at 5252 rpm, something is very not right with the graph. I also believe that dynapack's read so high (compared to other dynos including dj) that it is closer to crank HP regardless of what the shop tells you.

Your misfire could be because of the 2 step colder plugs...as others mentioned, this is the wrong choice for your build.

 

.

Actually, look at the chart again. The HP and Torque curves *DO* intersect at EXACTLY 5250 rpm. If you can't see it, i'll give you a hint later . . .

I am using 1-step colder plugs, not 2-step colder plugs. I thought the shop put in 2-step colder, but they did in fact use 1-step colder.

Also, i'm going to be getting some dynojet runs in two days just to get a "new" baseline for my car on that particular dyno. I'll post them when i get them done.

 

I'll take dyno curve crossings for $500 Liche....

btw, how do you like your catbacks? what is your skinny review?

 

maybe they dont cross at that speed cause its really reading wheel hp/tq, and its the engine hp/tq that cross at 5252?

 

oh wait- the scales arent the same on the sides of the dyno chart.... so basically it does cross, doesnt it.. duh

 

Bingo!

 

nice... understood.....

 

Okay, just had my car dynoed at R/T Tune in Lansdale, PA. Great shop and very knowledgeable and friendly guys there!

Here is the Dynojet graph. SAE correction factor is 0.95
Max. Boost was about 10.5 psi

 

What's with the AF spike there? I would say looks like they just started to decel/get off the gas, but dyno chart keeps climbing.

 

Thats because the tailpipe wideband got spit out at that point - thats all.