Disappointing dyno run... :( :(
Thread Starter
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Disappointing dyno run... :( :(
I just got back from "South Florida Performance" from the dyno test.
I got lucky and caught a rain break for my trip to the dyno shop (1 hour drive)...
The results were pretty disappointing and surprising...
At the best pull - the engine made 316.3 RWHP / 358.7 RWTQ....
The AIR/FUEL Ratio was a little rich above 5100 and a little to lean at 4100... The surprising part is that the maximum HP was reached at only 4800 RPM wth??????. Max. HP at 4800 RPM with the cam and intake that I use seems very strange... CAM: Custom ground solid .525/.545 lift 238/248 degrees duration @ .050..
The Intake is a fully ported and matched Tarantula (RPM Range 3500 - 7000).... What could be wrong????
Olivier
[Modified by GrandSportC3, 12:35 PM 7/10/2002]
I got lucky and caught a rain break for my trip to the dyno shop (1 hour drive)...
The results were pretty disappointing and surprising...
At the best pull - the engine made 316.3 RWHP / 358.7 RWTQ....
The AIR/FUEL Ratio was a little rich above 5100 and a little to lean at 4100... The surprising part is that the maximum HP was reached at only 4800 RPM wth??????. Max. HP at 4800 RPM with the cam and intake that I use seems very strange... CAM: Custom ground solid .525/.545 lift 238/248 degrees duration @ .050..
The Intake is a fully ported and matched Tarantula (RPM Range 3500 - 7000).... What could be wrong????
Olivier
[Modified by GrandSportC3, 12:35 PM 7/10/2002]
Melting Slicks
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From: Katy (Houston) TX
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Re: Disappointing dyno run... :( :( (GrandSportC3)
I hate point out the extremely obvious but have you double checked to see if your linkage is opening up to full throttle? I got mine dynoed and the torque looked right but the HP was way low and came in way too early. Turned out my linkage was only opening the carb up 75%. You can't imagine how stupid I felt. Guess that's why four hands are better than two.
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (tshort)
I hate point out the extremely obvious but have you double checked to see if your linkage is opening up to full throttle? I got mine dynoed and the torque looked right but the HP was way low and came in way too early. Turned out my linkage was only opening the carb up 75%. You can't imagine how stupid I felt. Guess that's why four hands are better than two.
Thanks
Olivier
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From: San Jose CA
Re: Disappointing dyno run... :( :( (GrandSportC3)
Heads? Voltage?
Exhaust?
Proper voltage is critical to high RPM operation. Make sure all your ignition components are good, and up to the power/RPM you're throwing at it.
What heads are you running?
-Steve
Exhaust?
Proper voltage is critical to high RPM operation. Make sure all your ignition components are good, and up to the power/RPM you're throwing at it.
What heads are you running?
-Steve
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From: Living in the Hartland
Re: Disappointing dyno run... :( :( (GrandSportC3)
If you factor in the 20% drive train loss you are at almost 400 horse. (316/.8) Did you only get to do one pull? Sounds like you need some carb tuning but not sure that is going to give you the 50 horse you are looking for. It was supposed to be about 465 horse right? What about timing and as mentioned throttle linkage? What size headers and exhuast? I have seen some posts stating that as you go over 400 horse you need 1 3/4 inch tube headers to get the most out of your engine and 3 inch exhaust. Not sure if that is 100% accurate. Still 400 horse is pretty nice.
Thread Starter
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (Pacin'California)
Heads? Voltage?
Exhaust?
Proper voltage is critical to high RPM operation. Make sure all your ignition components are good, and up to the power/RPM you're throwing at it.
What heads are you running?
-Steve
Exhaust?
Proper voltage is critical to high RPM operation. Make sure all your ignition components are good, and up to the power/RPM you're throwing at it.
What heads are you running?
-Steve
The Voltage was perfectly fine at around 13.5 Volts
Exhaust cannot be the problem too: 1 3/4 inch primaries and 4 inch collector - open (exept for 2 disc CCI Inserts)
It might be the throttle linkage.. The power seems right for 4800 RPM but dropped off after that.. I will check the linkage as soon as I get home!
:cheers:
Olivier
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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Re: Disappointing dyno run... :( :( (GrandSportC3)
That is a little surprising to me also, I would have bet your motor would have put 375 - 400 hp to the rear wheels. How big is the carb, what type of heads, and the flow numbers on the heads if you know them. With your cam I would think that max power should have been at least 6000 rpms. It also surprises me that your torque was so much higher than the hp.
Off top of my head if there is nothing obvious, carb linkage, etc maybe the cam was degreed wrong.
I would raise a little hell with the guy who told you the motor was 465 HP when he sold to you. :boxing
Off top of my head if there is nothing obvious, carb linkage, etc maybe the cam was degreed wrong.
I would raise a little hell with the guy who told you the motor was 465 HP when he sold to you. :boxing
Thread Starter
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (69 N.O.X. RATT)
That is a little surprising to me also, I would have bet your motor would have put 375 - 400 hp to the rear wheels. How big is the carb, what type of heads, and the flow numbers on the heads if you know them. With your cam I would think that max power should have been at least 6000 rpms. It also surprises me that your torque was so much higher than the hp.
Off top of my head if there is nothing obvious, carb linkage, etc maybe the cam was degreed wrong.
I would raise a little hell with the guy who told you the motor was 465 HP when he sold to you. :boxing
Off top of my head if there is nothing obvious, carb linkage, etc maybe the cam was degreed wrong.
I would raise a little hell with the guy who told you the motor was 465 HP when he sold to you. :boxing
:cheers:
Olivier
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Thread Starter
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (69 N.O.X. RATT)
The guy that sold me the car originally told me that the original owner had modified something around the gas pedal so that you could only depress the gas pedal to 75 percent because his daugther drove the car and he didn't want her to have too much power... However - I thought that my mechanic fixed that problem. I have to double check... I noticed that he re-did the linkage at the carb but I don't know if he checked if the carb would open up completely...
:cheers:
Olivier
P.S. When I last checked it - it was opening approx. 75% (before the new engine was installed)
:cheers:
Olivier
P.S. When I last checked it - it was opening approx. 75% (before the new engine was installed)
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Disappointing dyno run... :( :( (GrandSportC3)
Probably not too far off, 465 GROSS HP no accessories, open exhaust - 15% (accessoreis) = 395 NET HP - 20% ( drive train loss ) = 315 RWHP.
These HP numbers can be mighty confusing but I too have the same problem, my engine peaked around 5 grand and I am still trying to figure it out, whether it's fuel delivery or ignition. Yours and mine should still be pulling well past 5500 RPM.
The main thing to consider here is that you were on the chassis dyno and there is no smoke and mirrors anymore, now we have to find out how to maximize the next run :D
PS Anything in the 300 RWHP range is not too shabby :yesnod:
[Modified by MotorHead, 11:28 AM 7/10/2002]
These HP numbers can be mighty confusing but I too have the same problem, my engine peaked around 5 grand and I am still trying to figure it out, whether it's fuel delivery or ignition. Yours and mine should still be pulling well past 5500 RPM.
The main thing to consider here is that you were on the chassis dyno and there is no smoke and mirrors anymore, now we have to find out how to maximize the next run :D
PS Anything in the 300 RWHP range is not too shabby :yesnod:
[Modified by MotorHead, 11:28 AM 7/10/2002]
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (MotorHead)
Probably not too far off, 465 GROSS HP no accessories, open exhaust - 15% (accessoreis) = 395 NET HP - 20% ( drive train loss ) = 315 RWHP.
These HP numbers can be mighty confusing but I too have the same problem, my engine peaked around 5 grand and I am still trying to figure it out, whether it's fuel delivery or ignition. Yours and mine should still be pulling well past 5500 RPM.
The main thing to consider here is that you were on the chassis dyno and there is no smoke and mirrors anymore, now we have to find out how to maximize the next run :D
PS Anything in the 300 RWHP range is not too shabby :yesnod:
These HP numbers can be mighty confusing but I too have the same problem, my engine peaked around 5 grand and I am still trying to figure it out, whether it's fuel delivery or ignition. Yours and mine should still be pulling well past 5500 RPM.
The main thing to consider here is that you were on the chassis dyno and there is no smoke and mirrors anymore, now we have to find out how to maximize the next run :D
PS Anything in the 300 RWHP range is not too shabby :yesnod:
:cheers:
Olivier
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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Re: Disappointing dyno run... :( :( (GrandSportC3)
15 to 20 % should be total loss from all power robbing items combined, I agree you should have more power than 315 at the wheels, what is a postive point is it peaked so low in the rpm range. The linkage is a very probable problem, lets hope so. :chevy
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From: Virginia USA
Re: Disappointing dyno run... :( :( (69 N.O.X. RATT)
15 to 20 % should be total loss from all power robbing items combined, I agree you should have more power than 315 at the wheels, what is a postive point is it peaked so low in the rpm range. The linkage is a very probable problem, lets hope so. :chevy
John
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (69 N.O.X. RATT)
15 to 20 % should be total loss from all power robbing items combined, I agree you should have more power than 315 at the wheels, what is a postive point is it peaked so low in the rpm range. The linkage is a very probable problem, lets hope so. :chevy
:cheers:
Olivier
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Disappointing dyno run... :( :( (GrandSportC3)
First you have to distiguish between GROSS and NET HP. If GM says that a car is rated at 400HP then you will get 400 - 20% = 320 RWHP. This is the biggest problem here. GM rates it at NET HP.
If someone builds a motor and wants to sell it and puts it on a dyno then he is going to want to get the most out of it, you can run it with no altenator, fan etc. This is GROSS HP and the numbers are much higher and yes the losses are probably closer to 30 - 35 % when you get to the rear wheels
[Modified by MotorHead, 1:44 PM 7/10/2002]
[Modified by MotorHead, 1:45 PM 7/10/2002]
If someone builds a motor and wants to sell it and puts it on a dyno then he is going to want to get the most out of it, you can run it with no altenator, fan etc. This is GROSS HP and the numbers are much higher and yes the losses are probably closer to 30 - 35 % when you get to the rear wheels
[Modified by MotorHead, 1:44 PM 7/10/2002]
[Modified by MotorHead, 1:45 PM 7/10/2002]
Thread Starter
Team Owner
Joined: Jul 2001
Posts: 182,997
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (MotorHead)
First you have to distiguish between GROSS and NET HP. If GM says that a car is rated at 400HP then you will get 400 - 20% = 320 RWHP. This is the biggest problem here. GM rates it at NET HP.
If someone builds a motor and wants to sell it and puts it on a dyno then he is going to want to get the most out of it, you can run it with no altenator, fan etc. This is GROSS HP and the numbers are much higher and yes the losses are probably closer to 30 - 35 % when you get to the rear wheels
If someone builds a motor and wants to sell it and puts it on a dyno then he is going to want to get the most out of it, you can run it with no altenator, fan etc. This is GROSS HP and the numbers are much higher and yes the losses are probably closer to 30 - 35 % when you get to the rear wheels
:cheers:
Olivier
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Disappointing dyno run... :( :( (GrandSportC3)
Yes like I said before your engine and mine are capable of higher numbers that will come when we can figure out why they crapped out at such a low RPM
Drifting
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From: Harrison Township, Mi
Re: Disappointing dyno run... :( :( (GrandSportC3)
Grand Sport-I have almost identical RW #'s @ roughly the same RPM (291hp@4800 & 340 tq. @ 3700) with a much milder setup.
383 stroker
ported 1970 LT1 heads
Lt1 intake untouched
Lt1 Holley 780 carb (worked on at Dyno)
stock dist. w/ Pertronix
hyd. roller 509/428 222/230 @ .050
2.5 " exhaust manifolds, port matched to heads
My torque curve was really flat (300 from 2500-4900)
Sounds like somethings off. I would think that you would pull much higher tRPM's than I would....My tuning skills suck, but did you try leaning out the carb a little at WOT? How rich was it?
383 stroker
ported 1970 LT1 heads
Lt1 intake untouched
Lt1 Holley 780 carb (worked on at Dyno)
stock dist. w/ Pertronix
hyd. roller 509/428 222/230 @ .050
2.5 " exhaust manifolds, port matched to heads
My torque curve was really flat (300 from 2500-4900)
Sounds like somethings off. I would think that you would pull much higher tRPM's than I would....My tuning skills suck, but did you try leaning out the carb a little at WOT? How rich was it?
Thread Starter
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (randy72)
Grand Sport-I have almost identical RW #'s @ roughly the same RPM (291hp@4800 & 340 tq. @ 3700) with a much milder setup.
383 stroker
ported 1970 LT1 heads
Lt1 intake untouched
Lt1 Holley 780 carb (worked on at Dyno)
stock dist. w/ Pertronix
hyd. roller 509/428 222/230 @ .050
2.5 " exhaust manifolds, port matched to heads
My torque curve was really flat (300 from 2500-4900)
Sounds like somethings off. I would think that you would pull much higher tRPM's than I would....My tuning skills suck, but did you try leaning out the carb a little at WOT? How rich was it?
383 stroker
ported 1970 LT1 heads
Lt1 intake untouched
Lt1 Holley 780 carb (worked on at Dyno)
stock dist. w/ Pertronix
hyd. roller 509/428 222/230 @ .050
2.5 " exhaust manifolds, port matched to heads
My torque curve was really flat (300 from 2500-4900)
Sounds like somethings off. I would think that you would pull much higher tRPM's than I would....My tuning skills suck, but did you try leaning out the carb a little at WOT? How rich was it?
The lean spot was between 4100 and 4200 at close to 14
:cheers:
Olivier
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Disappointing dyno run... :( :( (GrandSportC3)
here is the dyno sheet!
:cheers:
Olivier
[Modified by GrandSportC3, 9:39 PM 7/10/2002]
:cheers:
Olivier
[Modified by GrandSportC3, 9:39 PM 7/10/2002]