Dyno Vs.Drag Strip Testing

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I’ll jump in with a little experience I had. On my first stand alone fuel injection set up I had a well known tuner set it up on the dyno. Took two days to get it sorted. That was after I had it on a run stand for a week setting up the base tune. I learned more about the software and how to tune it in those two days than I would have learned in months trying to drive the car around with the laptop. The HP the engine made was not the main focus, the HP came as a result of setting up a safe tune with multiple maps for different boost levels and different fuels. Cost me $700 and in my opinion the best money spent on the engine build.
 
RAMM said:
Agreed--I charge $525 CDN for 5 hrs (which is always a full day) or $600 with dual widebands. A day on the dyno WILL accelerate your program (pun intended) by weeks or months or even years--depending on how often you get to the track. A good dyno operator can tell you much more than what is printed on the dyno sheets too. Can timing and jetting requirements be different from the dyno to the track? --Yes--But it won't be off 10 degrees of timing or 10 jet sizes-If your dyno experience is any good.

There is a thread right now about a stroker with TF heads not running the MPH the OP thinks it should. OP's research says it should make 550HP but it runs 113mph and change. A cheap and easy dyno session would have shown him that it makes about 450-475hp likely on the first pull. Then the tuning begins--Yes I have seen 75hp from the first pull to the last but that is extremely rare. It is usually 20-30 hp gain from the first to the last--And it is often what you can tell from reading between the lines that gets you the farthest. J.Rob
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Yes, it's painful to see but, happens all the time! (Preaching to the choir)
Too lean, too hot, over-reving, backfiring through the carb, John Force style burn outs...
I help them, when I can. We all had a beginning.

There's a reason dynos are being used by guys in Super stock and Stock on a regular basis.. it's a time saving tool.
It's not justifiable in some categories (no index) but even some of them do too. It's just practical.
 
RAMM said:
Agreed--I charge $525 CDN for 5 hrs (which is always a full day) or $600 with dual widebands. A day on the dyno WILL accelerate your program (pun intended) by weeks or months or even years--depending on how often you get to the track. A good dyno operator can tell you much more than what is printed on the dyno sheets too. Can timing and jetting requirements be different from the dyno to the track? --Yes--But it won't be off 10 degrees of timing or 10 jet sizes-If your dyno experience is any good.

There is a thread right now about a stroker with TF heads not running the MPH the OP thinks it should. OP's research says it should make 550HP but it runs 113mph and change. A cheap and easy dyno session would have shown him that it makes about 450-475hp likely on the first pull. Then the tuning begins--Yes I have seen 75hp from the first pull to the last but that is extremely rare. It is usually 20-30 hp gain from the first to the last--And it is often what you can tell from reading between the lines that gets you the farthest. J.Rob
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Exactly. You can tell by this thread who has used a dyno, and who has not.
 
RAMM said:
Agreed--I charge $525 CDN for 5 hrs (which is always a full day) or $600 with dual widebands. A day on the dyno WILL accelerate your program (pun intended) by weeks or months or even years--depending on how often you get to the track. A good dyno operator can tell you much more than what is printed on the dyno sheets too. Can timing and jetting requirements be different from the dyno to the track? --Yes--But it won't be off 10 degrees of timing or 10 jet sizes-If your dyno experience is any good.

There is a thread right now about a stroker with TF heads not running the MPH the OP thinks it should. OP's research says it should make 550HP but it runs 113mph and change. A cheap and easy dyno session would have shown him that it makes about 450-475hp likely on the first pull. Then the tuning begins--Yes I have seen 75hp from the first pull to the last but that is extremely rare. It is usually 20-30 hp gain from the first to the last--And it is often what you can tell from reading between the lines that gets you the farthest. J.Rob
Click to expand...
I have what i thought was a well sorted out air intake system. A a dominater aircleaner base and stacked nascar 14x3 filters. A large hood scoop and good seal . i felt my car was 2 to 3 mph slow for the dyno numbers, at 151.5. I had some problems and opted to run without the hood or aircleaner, just the scoop. The aircleaner showed a 1 hp los on the dyno, so i assumed it was quite efficient. But the car went 154.32, or 3.8 mph faster!
So i assume it muat be aerodynamics/airflow around the front end that made the difference.
 
gregsdart said:
I have what i thought was a well sorted out air intake system. A a dominater aircleaner base and stacked nascar 14x3 filters. A large hood scoop and good seal . i felt my car was 2 to 3 mph slow for the dyno numbers, at 151.5. I had some problems and opted to run without the hood or aircleaner, just the scoop. The aircleaner showed a 1 hp los on the dyno, so i assumed it was quite efficient. But the car went 154.32, or 3.8 mph faster!
So i assume it muat be aerodynamics/airflow around the front end that made the difference.
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I have tried several times to seal the carbs to the hood scoop, with and without air cleaners. The car slowed down every time I had it sealed, picked up when I threw the seal in the truck. I did NOT try to tune for the seal, cause I'm a lousy carb tuner. It was easier to just not use it.
 
gregsdart said:
I have what i thought was a well sorted out air intake system. A a dominater aircleaner base and stacked nascar 14x3 filters. A large hood scoop and good seal . i felt my car was 2 to 3 mph slow for the dyno numbers, at 151.5. I had some problems and opted to run without the hood or aircleaner, just the scoop. The aircleaner showed a 1 hp los on the dyno, so i assumed it was quite efficient. But the car went 154.32, or 3.8 mph faster!
So i assume it muat be aerodynamics/airflow around the front end that made the difference.
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I doubt your car became more aerodynamic without the hood. I suspect your scoop is making the air entering the carbs VERY turbulent. The reason I say this is I have a Bonneville land speed customer with a 439CI 1st Gen Hemi making well over 800HP NA with 2 carbs. He battled scoop issues and figured it out because after a 3 mile run the firewall and windshield was covered in a red liquid that turned out to be the fuel they have to run in his class. The carbs were getting all kinds of wacky air movement at 200+ MPH and actually spraying fuel anywhere but down the sheetmetal intake. He ditched the forward facing scoop the following year and picked up big time and no more fuel on the firewall/windshield. I have also seen this in a tunnelram street application--where the guy removed his little tiny air cleaners to do some fiddling and the car ran like crap just driving normally down the road. He reinstalled his little air cleaners and the car ran perfect again. The conclusion was the air cleaners straightened out the air entering the carbs and the carbs liked it. Just some of my experiences. J.Rob
 



Lack of interest has been affected all of my projects now. Not really sure what it will run as I never played with nitrous but I know a had to make sacrifices that will really affect NA ET numbers. Dished pistons, thicker head Gaskets, bigger ring gaps, and a nitrous converter. Hopefully I finish it one of these days.
 
Posts 129 and 130 are very interesting. To get a scoop to function is a ton of work. Most scoops are too low and too far back.
 
RAMM said:
I doubt your car became more aerodynamic without the hood. I suspect your scoop is making the air entering the carbs VERY turbulent. The reason I say this is I have a Bonneville land speed customer with a 439CI 1st Gen Hemi making well over 800HP NA with 2 carbs. He battled scoop issues and figured it out because after a 3 mile run the firewall and windshield was covered in a red liquid that turned out to be the fuel they have to run in his class. The carbs were getting all kinds of wacky air movement at 200+ MPH and actually spraying fuel anywhere but down the sheetmetal intake. He ditched the forward facing scoop the following year and picked up big time and no more fuel on the firewall/windshield. I have also seen this in a tunnelram street application--where the guy removed his little tiny air cleaners to do some fiddling and the car ran like crap just driving normally down the road. He reinstalled his little air cleaners and the car ran perfect again. The conclusion was the air cleaners straightened out the air entering the carbs and the carbs liked it. Just some of my experiences. J.Rob
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I am going to start a post about the scoop/hood/aircleaner deal; would like your further comments RAMM after you see pics of my junk. Something wierd is going on.
 
gregsdart said:
I am going to start a post about the scoop/hood/aircleaner deal; would like your further comments RAMM after you see pics of my junk. Something wierd is going on.
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It’s hard to tell how tall that scoop is, and how far forward it goes.

On my early A the scoop had to be almost to the end of the hood, or the air hits that square nose and goes straight up.

That’s why it needs to be pretty high and forward.

If you look at a modern car, and the low, swoopy front and they still run the high, forward scoop.

Well, the did before they neutered Pro Stock.
 
And then there is what we called scoop packing on sealed set ups.
 
My car has a glass 6 pack hood on it. At the strip it's unhappy without the air pan sealing the hood to the carb.

Thumperdart had to cut some teardrop slots in the back of his 6 pack scoop to make his car happy. IIRC the afr's were all over the place.
 
gregsdart said:
New post shortly
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Interesting , I have a scoop because my throttle body is partially above the hood , didnt really want one .
Have to seal it to the hood because of under engine heat . I have seen big engines (crate 505 in a chevy pick up) , heat up on the hi way because the carb wasnt sealed to the hood , the scoop airflow packed the engine compartment which fought the incoming rad. air .
Have thot about reliefs cut into the back of mine too.
 
It has been proven in the wind tunnel many times that a forward facing hood scoop really doesn’t receive much ram air effect unless it is extremely high above the level off the hood. I have a 6” six pack glass hood on my dart and saw no appreciable difference in performance on or off (not sealed to the carb though). I did notice the engine ran warmer with it ON. I would guess because it disrupted the air moving through the radiator as said above. This was on a mild street strip deal not a full on race effort. On our bonneville cars rear facing scoops always perform better than forward facing and naca ducts work even better
 
TT5.9mag said:
It has been proven in the wind tunnel many times that a forward facing hood scoop really doesn’t receive much ram air effect unless it is extremely high above the level off the hood. I have a 6” six pack glass hood on my dart and saw no appreciable difference in performance on or off (not sealed to the carb though). I did notice the engine ran warmer with it ON. I would guess because it disrupted the air moving through the radiator as said above. This was on a mild street strip deal not a full on race effort. On our bonneville cars rear facing scoops always perform better than forward facing and naca ducts work even better
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Some have run tubes from the air cleaner to the cowl. I've always liked the idea. I need to try it, never have.
 
Has anyone noticed a fuel distribution change when going from the dyno to the actual car as G Forces are applied?
 
Hysteric said:
Has anyone noticed a fuel distribution change when going from the dyno to the actual car as G Forces are applied?
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Yes. You won’t see the results of G forces on the system on the dyno.

For whatever reason, when the supply side starts having issues, the fuel distribution gets weird. I suspect some of it is the lower float levels have some affect. And maybe there is more air in the fuel with the system can’t keep up.
 
yellow rose said:
Yes. You won’t see the results of G forces on the system on the dyno.

For whatever reason, when the supply side starts having issues, the fuel distribution gets weird. I suspect some of it is the lower float levels have some affect. And maybe there is more air in the fuel with the system can’t keep up.
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Bingo! Fuel level affects the emulsion and where it happens not mention the g forces on the fuel exiting the boosters
 
If I built my own stationary dyno, I would probably build it so that i could change the angle of attack to somewhat simulate G forces. Imagine a weighted string hanging from your rear view mirror as a visual indicator of G force. If the car were accelerating at 1G, the angle of that string would be 45 degrees. For a stationary dyno to somewhat replicate 1G of acceleration, nose of the engine would need to angle up 45 degrees. For 2G of accel, the nose would have to angle up about 63 degrees! Imagine the affects on the oiling system, float levels and carb calibration. Makes you wonder why there isn't more performance difference between carbs and efi. No wonder T56's need a pump to spray oil on the head gears.

Grant
 
weedburner said:
If I built my own stationary dyno, I would probably build it so that i could change the angle of attack to somewhat simulate G forces. Imagine a weighted string hanging from your rear view mirror as a visual indicator of G force. If the car were accelerating at 1G, the angle of that string would be 45 degrees. For a stationary dyno to somewhat replicate 1G of acceleration, nose of the engine would need to angle up 45 degrees. For 2G of accel, the nose would have to angle up about 63 degrees! Imagine the affects on the oiling system, float levels and carb calibration. Makes you wonder why there isn't more performance difference between carbs and efi. No wonder T56's need a pump to spray oil on the head gears.

Grant
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Grant stop thinking outside the box it scares these guys!...
 
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