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Author Topic:   Chassis Dyno?
dirtracer14
Member
posted May 15, 2003 07:12 PM
Has anyone ever put there mod on a chassis dyno? Did you dyno your motor by it self also? What was the HP loss from engine to chassis? Thanks, Craig


Racer64
Member
posted May 15, 2003 09:14 PM
I had my modified on the dyno last Monday. My engine builder gave me some free time. And the dyno is brand new. I just got my new motor in Saturday and dynoed it Monday. I thought the way it ran I would see some huge numbers but he told me that you loose about 40% to the rear wheels. I have never dynoed one on the stand.

My new motor is a 406 with 6 inch rods and Dart 215cc heads. About 13 to 1 compression and a decent cam. I came up with about 343 HP and 298 ft lbs. of torque. So what I am figuring is over 500 horses and around 500 ft lbs of torque.

Was a different experience sitting there and mashing the throttle to 7000 and not moving.LOL

Very interesting though.

dirtracer14
Member
posted May 15, 2003 09:40 PM
Well im heading out fri to get strapped down...ya im thinking the same thing about the 7000 sitting there with the rear tires spinning I was thinking around 330 to 350 hp at the wheels but we will see. What do you have for trans,clutch,rear gear? I have a 377 with bone stock bowtie heads and looking to get what i can out of this thing till the good heads get done.


sdhnc29
Member
posted May 15, 2003 10:10 PM
The loss of power through the drive train with a 9" Ford rear end and a Bert or Brinn is 15% . A quick change rear end with the same Bert or Brinn transmission has a loss of 18.2% . The 15% number comes directly from Dyno Jet . The 18.2% Number comes from our own back to back testing from engine dyno to chassis dyno .

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

[This message has been edited by sdhnc29 (edited May 15, 2003).]

jws
Member
posted May 15, 2003 10:42 PM
I agree with everyone elso that has responded. I have spent a fair amount of time on a chassis dyno, made 515 hp at the rear tires. Motor is 406 chevy, 13:1, with very worked Bowtie heads (2.08/1.60), Super Victor, and MSD. This was with a three speed Toploader with a triple disk clutch. I'm curious to see what the motor puts down with my Brinn. We figured a loss of 20% due to drivetrain friction when I ran the triple disk and three speed. The big thing that I noticed, was not the final number, but how I picked up 50 hp and 50 ft lbs of torque by adjusting jetting and ignition with the use of an EGT. I highly recommend the use of a chassis dyno to anyone. It typically only costs $150-$300, but the benefits well outweigh the cost.


dirtracer14
Member
posted May 16, 2003 11:27 AM
With the jetting was there more gain than the timing? Did you do them separate? I have stock bowties and the intake has been ported. i am hoping to swap a few diff fans on it also to see if it will affect it...i will post tonight if i make it there today..


dirtbuster
Member
posted May 16, 2003 11:55 AM
For future reference what can you expect for % loss from the following:
ford 9" and powerglide?
ford 9" and stock muncie?


dirtracer14
Member
posted May 16, 2003 07:35 PM
Well here are the #s 420 ft-lb and 407 hp that was after adding some timing. This was with a muncie 2 spd and a 5 1/4 tilton 3 disk light gears and light spool. The motor is 377 with untouched bowties and flat tappet cam. When i get the iron eagles back i will run it again and see the diff


Chad
Member
posted May 19, 2003 04:12 PM
In response to Dirtracer14, the biggest gain I got was from the jetting. I was running too rich, it was killing the power all the way through the rpm range. Using an EGT, I was able to get the jetting so the temp was in range, but not too close to the edge (running alcohol). After the jetting, I played with the timing. Found most power at 32 degrees. Running the timing up to 36-38 actually lost power, as did running it down to 27 degrees. Running down to 27 degrees really took the torque out, which I will use on a very dryslick tack when I want to take some of the hit out of the motor. Hope this helps, its what worked for me.


HRT187
Member
posted May 19, 2003 04:49 PM
What EGTs would a fella look for on gasoline?


WPP
Member
posted May 19, 2003 04:55 PM
What size jets were you runing and how much did you drop them down how big was the change


jws
Member
posted May 19, 2003 11:00 PM
jws ,
Did you mean to say that ignition timing is not critical on high compression engine's , or was that a misprint ??? Or did you mean to say that ignition timing is EXTREMELY critical on high compression alky and gas engines , and for the type of cylinder head/combustion chamber design being used ???

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


Chad
Member
posted May 21, 2003 06:17 PM
WPP, I'm trying to remember back. I don't run a high dollar carb, just a box stock alcohol Holley. I was running jets in the low 90's, and ended up jetting down to 75 or 77. Remember, the stock Holley alcohol carb has a large (.125") bleed hole drilled above the jet in the metering block (on both metering blocks). This allows smaller jets to be run. If you run a carb with a custom built metering block, chances are the hole over the jets is either non-existent or very small. The builder of these carbs uses the meter block design and jet to control fuel supply. The best thing you can do is get on a chassis dyno and jet to EGT temperature. If my memory serves me right, I think 1200-1250 degrees is a safe temp, but maybe sbhnc29 can correct me on this. I also agree with the prior post about running too rich on alcohol. I can't stress enough how wrong the old saying is "that you can't be too rich on alcohol". Correct jetting made my motor run so much better, not to mention it was easy to start.