ran the vett on the dyno today.in june i ran the vett max hp was 351 and max trq was 435 at the rear wheels, this was using SAE scale. my trq and hp lines crossed at 5250rpms. today best out of three runs was,
max hp 333 max trq 386 using actual horsepower
max hp 314 max trq 364 using SAE scale
max hp 324 max trq 376 using STD scale
my trq and hp lines crossed at 4500rpms.
heres what i did to the car since the dyno run in june. i changed the rear from a 3:08 to a 3:70,i put in a new disdributer and set the timing to 36% total timing per lars tech tip. the timing is about 5% at idle. the run in june it was about 11%. i also had one plug wire arc out the side of the boot. i'm sure that had some effect.
the vette has a LS6 i was hoping for higher numbers the temp. today was about 40% cooler. the car didn't sound as smooth as it did on the last run.
does anyone know the differance in the scale they used today. the shop printed all three run with using all three scales. there is 19 hp differance between SAE and actual on all three runs. does this mean in june my actual should have been 370max hp :D and why such a drop today

 

First off, check to make sure the _scale_ on each side (one for HP and one for TQ) are the same b/c the HP/TQ curve will ALWAYS intersect at 5250rpm. Hp is a function of TQ, and that's how the math works out. I'm guessing one of the scales may show 300 on one side, but if you look straight across, the other one is at 350. This doesn't mean there's a problem with the dyno or the graphs, but this is why the curve today looks like it crosses at a lower rpm.

As far as Actual vs. SAE... the reason actual was higher is b/c you had some nice, cool crisp air. :) You had a negative "correction factor" today, meaning the air was better than standard. In the summer (at least where I am in Texas) you will most likely have a positive correction factor...meaning the ACTUAL is less than SAE.

As I read the numbers you posted, you are down 37rwhp/71rwtq from the pull last June. The arcing plug wire is a problem...I'm surprised the graph didn't look a bit jagged compared to the June runs (or maybe it does?). Is that worth 37rwhp? Possibly, if its missing really bad on that cylinder, and you're effectively only running on 7 most of the time. Also, swapping from 3.08s to 3.70s will show up as a slight loss in power, too. Don't ask me why...I cannot type the physics involved here in a short paragraph, but the dyno shops I frequent have confirmed this.

I think if you can get a stock/near stock LS6 to hit 350+rwhp then you're doing pretty good. Remember, this is well over 425hp at the crankshaft.

At what rpm does it make peak HP/TQ?

FWIW, ACTUAL #s are what the engine produced _today_ in the air you had. This isn't an inaccurate figure. However, you have to correct the #s (like most people do when racing at 5000' above sea level) to some sort of universal standard of air quality, otherwise it is impossible to compare #s in "good" air to "bad" air (95^F, 50% hum., for instance). SAE and STD are two different correction factors. I do not have the exact data for each, but SAE is lower b/c it uses 72^F, 40% hum, 29.92" Hg baro. pressure. I cannot remember what STD is, but I think its something like 59^F, 0% hum., etc. ... so it will show a higher figure than SAE will.

Again, this is good b/c it allows you to make tuning changes and come back to see what works and what doesn't...without being stuck with the air quality you have on a particular day. :)

[Modified by WA 2 FST, 6:08 PM 1/4/2003]


[Modified by WA 2 FST, 6:13 PM 1/4/2003]

 

Your initial dyno runs were very impressive. My '02 ZO6 LS6 made 352corrected (sae) horse power, but nowhere close to 425 pounds of torque. I don't know of any other factory LS6 doing so either. You must be making that power at a pretty low rpm. As was said above, HP and TORQUE always equal at ~5250rpm. If you know the torque of an engine at any rpm, you can calculate the horsepower and visa versa. The relationship between the two is rigidly determined by the equation.

Chuck

 

Is that a modern LS6? as in, same engine as 2002 ZO6? Or is it a 454 ci LS6 (or is it LS-6) like the rare 1971 bigblock? :) All that torque makes me thingk bigblock! :) MJ

 

MNJack,

I think you are right, I probably confused him with what I think is another '70 with a new LS1/6 transplant. :bb

Chuck

 

thanks for your help. the motor is 1970 454 LS6 it's an off road version of the LS6 offerd in the 1970 chevelle.as for the scale it is differant 350 on the hp side and 400 on the trq side in june the hp pecked at351@5300rpms and the trq pecked at 435@3700rpms. jim

 

different dynos? my experience is limited but I think you can get pretty huge differences between dynos, and maybe even differences on same dyno on different days. but need to consult a dyno expert on this! :) MJ

 

Jim,

Thanks for the information on the HP/TQ rpm peaks. Now, the reason you see the graphs crossing at a lower rpm on your latest runs is b/c the two graphs as scaled differently...that's all. :)

I still say you cost yourself some power by having a misfire on one cylinder, and you will also lose some by going to the steeper gears. Get the spark plug wire problem sorted out and go back and re-dyno and see what it looks like.

You may also have a clue by comparing at what rpm the HP/TQ curves peaked at just a few days ago.