Author Topic: +stroke dubble hump (Read 5302 times) Tweet

Commuta_Busa · « **on:** August 12, 2004, 10:34:11 AM »

Can anyone explain to me why on a stroked motor the torque curve resembles the two hump on a camel? My peak torque is almost at two points on my dyno sheet... What's the best approach to try and raise the little valley between the two peaks???

Commuta_Busa · « **Reply #1 on:** August 12, 2004, 01:27:19 PM »

If I knew how to post a pic I would've the dyno run, it might make more sense then...

1st attempt:
http://images.snapfish.com/33%3B5565923232%7Ffp63%3Dot%3E232%3C%3D62%3B%3D63%3C%3DXROQDF%3E23235%3A49233%3C6ot1lsi

Nosgsx1300 · « **Reply #2 on:** August 12, 2004, 06:25:47 PM »

Your dyno graph looks like mine from last year(Okay I have lower #'s)
what cams/lobe centers are you running?
Pipe?
I did bigger cams with higher lobe centers and it is gone now

Nosgsx1300 · « **Reply #3 on:** August 12, 2004, 06:27:46 PM »

also Why does the chart start at 7k?
Like to see a run from 3k ,you could probably tell more

tampated · « **Reply #4 on:** August 12, 2004, 07:47:10 PM »

I'm not an expert but I would think you would want to look at your air/fuel ratio in the range in question first. I also can see you HP curve dip down aswell.

DaveO · « **Reply #5 on:** August 12, 2004, 11:24:52 PM »

Commuta,

Short stacks??? What size motor?

Dave

raxen · « **Reply #6 on:** August 13, 2004, 12:00:31 AM »

Commuta_Busa · « **Reply #7 on:** August 13, 2004, 09:04:00 AM »

my hp starts to flatten off because I'm still running the stock injecters. Ys, it's all short stacks.

I'll have better graphs and more complete info (A/F ratio) sometime next week.

I just recall someone else posting at one time a graph that had similar traits to mine with the twin peak syndrome...

DaveO · « **Reply #8 on:** August 13, 2004, 09:41:27 AM »

Commuta,

The short stacks will do that on larger motors..very typical. I saw it first on my 84mm motor 4 years ago. Somebody coined it the "camel back" torque curve.

Dave

Commuta_Busa · « **Reply #9 on:** August 13, 2004, 09:54:14 AM »

that sounds exactly like my situation... (same bore) any clue who it was so I can ping them

DaveO · « **Reply #10 on:** August 13, 2004, 11:32:36 AM »

Commuta,

Yea it was me....LOL. My 1507 still has a slight dip @8K rpm's. You can tune most of it out using diff stacks, or cam timing, or both. Your best choice depends on your application.

Dave

Commuta_Busa · « **Reply #11 on:** August 13, 2004, 11:44:17 AM »

how much of a drop did you have? mines about 10ft-lbs...

DarkFalcon · « **Reply #12 on:** August 13, 2004, 12:02:00 PM »

Quote from: DaveO

Commuta,

The short stacks will do that on larger motors..very typical. I saw it first on my 84mm motor 4 years ago. Somebody coined it the "camel back" torque curve.

Dave

I wonder if tuning "resonances", whether intake or exhaust, are driving these dual peak patterns.

DaveO · « **Reply #13 on:** August 13, 2004, 02:59:16 PM »

Dark,

You are correct....

Commuta,

Mine dips 2-4 ft/lbs around 8k, it's pretty flat from 7-10k.

Dave

Commuta_Busa · « **Reply #14 on:** August 13, 2004, 03:12:29 PM »

8k is exactly where my valley is between the two peaks, but I'm looking @ about 7-8 ft-lbs...

hmmm wonder if your dyno shet was faxed to me instead of mine! The similarities are uncanny!

Quote from: DaveO

Commuta,

Mine dips 2-4 ft/lbs around 8k, it's pretty flat from 7-10k.

Dave

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Author Topic: +stroke dubble hump (Read 5302 times) Tweet