Wicked Weasel

I really would like to know what to look at when reading a dyno chart. The top numbers are easy to see, but what else should I be looking for.

thanks

Bob

0foff667

depends what your trying to go for or see or do...what exactly about your dyno chart are you looking to see?

ajderzie

Probably a smooth torque curve with as much area under the curve as possible. The more area under the curve the better acceleration through that rpm range. A smoother line means that the engine is operating more efficently throughout its rpm range. Dips may mean that you are leaving power on the table (so to speak) at that particular point. Technically speaking I think it would mean that the cell on the table that corresponds to that particular dip needs to be adjusted.

I just started learning tuning but I don't think I said anything too controversial here. Hopefully someone with more experience could chime in.

RED99

They are pretty simple. Most has the power and torque on the same scale. But some don't, so those can be misleading if you are not careful.
The top is RPM of course.
The HP will be on one side, and the TQ will be on the opposite side of the chart. One line will represent the HP, and another will represent the TQ. And they always meet at 5250 rpm.
In general, the easiest way to determind which is which, TQ will show the higher number before the 5250 mark, and HP will show the higher mark after 5250.

Wicked Weasel

Ok maybe this is easier with a picture. Here is my Dyno. The first run is with MAF tune and the Second is with Speed Density tune and change of gears from 4.10s to 3.73s.

Being that I road race I like the power to come on after 3500 rpms and up. For the most I do not need quick start line acceleration, but I do need power after coming out of a turn. So looking at the chart below I hit maximum tq right before 5K rpms. If I got it right the only thing to concern me then is the dip of tq right between 4000 and 4500 rpms.

0foff667

many LS1's have that tq dip...not sure if theres a clear public explanation why. But yes your making peak tq at around 5000 rpms, peak hp somewhere around 6500 rpms.

Wicked Weasel

thanks. Would this be considered a smooth curve or a peaky curve? I guess that is what I am looking for more explaination around.

0foff667

IMO for a stock cubed ls1 is a very good curve...tq is over 350ft lb from 3500+rpms which will be great for what you need...gear it correctly & you'll have a monster on your hands.

SBTuner

Hello, perhaps I can offer a little more explanation. When looking at a dyno chart you do not want to focus on the peak values, but focus on the area under the curve as most "Dyno Guys" describe it. That area is derived by taking the peak torque and finding where 85-90% of that begins and ends in your sweep. Usually the wider this RPM range is the better off you are. (This really depends on how you are using the vehicle though) This will give you a better understanding of where you need to operate your engine. Now the area will change a little when in the lower gears (usually dropping off earlier) and can be verified on the engine dyno.

As for the dip in your torque curve we need some additional data. I would want to see the spark angle and knock retard in that area along with commanded AF and actual AF. This is what I would use as a tuner in evaluating this situation.


If you have any furhter questions please let me know.


Kind Regards,

Scott Brown

Bluefire

Why do they always meet at 5250 RPM's?

0foff667

because hp is a # derived from a calculation using tq.

cjs27410

Thanks for that explanation.

Wicked Weasel

thanks it does pull great. I will look for another dyno so maybe we can compare the difference.

Wicked Weasel

thanks that helps.


I am glad that others are getting some info out of this too....

itchynackers

They actually meet at 5252, but who's counting...

SteveDoten

although highly unlikely, you will see some posts of dyno graphs that are not SAE corrected

DOUG @ ECS

My explanation on the dip in the graph, since just about every n/a car seems to it, is while you are sitting on the dyno at say 3000 rpm just about to make a pull you are in high vacuum state. When you floor it quickly you get a spike from the air rushing to that source of vacuum. Once it levels out to ambiant it flatens a bit and then climbs. I could work that out easily by waiting to hit the button on the dyno, or start the pull at 1500rpm etc, but it just never bothered me enough to do anything about it. At least thats my take on it.

hex

If it runs good, and is safe, drive it. You don't race on the dyno. It is just a tool. I personally like to datalog my road course sessions to back up what I saw on the dyno.