Dyno HP vs driving feel

General engine tech -- Drag Racing to Circle Track

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Scotthatch
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Dyno HP vs driving feel

Post by Scotthatch » Mon May 14, 2018 1:14 pm

I don't know if this will work but trying to move this out of another thread
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Re: Dyno HP vs driving feel

Post by Scotthatch » Mon May 14, 2018 1:20 pm

The thing that a lot of people don't realize is that the dyno sheet is torque and HP at WOT ...when you drive a car you are at 1/3 to 1/2 throttle and the airflow dynamics in the intake track change ... in this case the longer runners of the truck intake will help the airspeed under part throttle and make more torque then a shorter runner ....

I have fixed cars that where no fun to drive ... in one case I gave up 30 HP peak but took the car from only works at full throttle to drives like a dream ...best 30 HP I did not make

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Re: Dyno HP vs driving feel

Post by mag2555 » Mon May 14, 2018 1:32 pm

Yes, maxing out average port air speed in the most used rpm range can make for loosing the over cooked Linguine feel of the throttle big time!
Think about what just a 15 ft lb torque increase turns into when you multiply by even just let's say second gear and then the rear gear!
Last edited by mag2555 on Mon May 14, 2018 1:40 pm, edited 1 time in total.

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Re: Dyno HP vs driving feel

Post by Zmechanic » Mon May 14, 2018 1:37 pm

I'd have to agree with Jon there. That's apparent even on the dyno graph. It carries 40-50hp more through a pretty wide RPM range.

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Re: Dyno HP vs driving feel

Post by groberts101 » Mon May 14, 2018 5:27 pm

On the surface it appears obvious which one would be more enjoyable to drive but it depends on your version of what's "enjoyable". Absolutely nothing wrong with downshifted balls out light switch like power production either. Changing the rear gear will more than make up for that lower rpm torque deficit and ton's of guys are doing just that with the CJ manifold swaps these days. And many are also doing it on the heavy assed trucks too.

There's an old test between the 2015 Z/28 and GT350 that illustrates how torque output can be nominalized between various engine designs and may help shed some light on what' you're asking here. Around the 7.00 minute mark you can see the power graphs. Kinda goofy video but I like it because I grew up around street racing goofballs like this. :D

https://www.youtube.com/watch?v=vtdtGgf1BF0

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Re: Dyno HP vs driving feel

Post by swampbuggy » Mon May 14, 2018 11:18 pm

Groberts 101----I know which car gave me chill bumps, i'll take the rev's one. :wink: Mark H

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Re: Dyno HP vs driving feel

Post by groberts101 » Mon May 14, 2018 11:25 pm

swampbuggy wrote:
Mon May 14, 2018 11:18 pm
Groberts 101----I know which car gave me chill bumps, i'll take the rev's one. :wink: Mark H
Yeah.. I hear ya there. Torque is great to have in spades on a daily driver, especially with more civil street gear ratios.. but I'll take an 8,000+ rpm high winder with shorter gear any day of the week. Drop down 2 gears and let the symphony begin. :mrgreen:

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Re: Dyno HP vs driving feel

Post by digger » Tue May 15, 2018 12:36 am

I've had a cam change make zero difference on the dyno ( line on line) but at part throttle one was much more responsive to drive that you'd think the dyno would be miles different .

As for the op the one that peaks higher just needs a little more gearing. It'll be a little busier but much faster everywhere

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Re: Dyno HP vs driving feel

Post by Belgian1979 » Tue May 15, 2018 5:10 am

You'd be surprised how few ponies you need to keep a constant speed. Torque en hp is only good for acceleration.
For the rest what counts when going at a certain speed is how well behaved the engine is at your cruise rpm.

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Re: Dyno HP vs driving feel

Post by Orr89rocz » Tue May 15, 2018 7:45 am

Belgian1979 wrote:
Tue May 15, 2018 5:10 am
You'd be surprised how few ponies you need to keep a constant speed. Torque en hp is only good for acceleration.
For the rest what counts when going at a certain speed is how well behaved the engine is at your cruise rpm.
I agree here and alot of that, imo, is how well the engine is tuned. All the cars i ever played with are efi based and tuning can make the difference in how well a car drives

I never had a combo that made decent power, not be enjoyable on the street. Stall and gear come into play and once they agree, the car rips.

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Re: Dyno HP vs driving feel

Post by Casper393W » Tue May 15, 2018 9:00 am

I know that I have seen a engine develop good power on the engine dyno, but wouldn't accelerate down the drag strip... Nothing like having a 650hp 406ci SBC and the best the car could run was 6.80's in the 1/8th. The owner of the car chased his tail Forever because he didn't want to accept the fact his new $15k engine was the culprit. He changed rear gear, Converter (2 times) and borrowed a known good PG Trans...

He took the engine to my buddies shop...we swapped the heads/and cam went back to the track and ran a 5.92 on his first pass.....

My take away

The biggest head and cam "might" make big power....but it doesn't mean it will be fastest

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Re: Dyno HP vs driving feel

Post by Steve.k » Tue May 15, 2018 9:11 am

Im wondering if there are just things to look for on dyno. How the tq curve comes in and how long it stays in. That likely affects how car moves. The dyno is a useful tool to have, i dont believe that because it made a certain amount of power on dyno it wont move car. Its where the curve is at. The engine in dyno gets more load than it ever sees in vehicle.The emc dyno challenge is a good example. Im betting a emc engine pull hard in vehicle.

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Re: Dyno HP vs driving feel

Post by Warp Speed » Tue May 15, 2018 9:58 am

Casper393W wrote:
Tue May 15, 2018 9:00 am
I know that I have seen a engine develop good power on the engine dyno, but wouldn't accelerate down the drag strip... Nothing like having a 650hp 406ci SBC and the best the car could run was 6.80's in the 1/8th. The owner of the car chased his tail Forever because he didn't want to accept the fact his new $15k engine was the culprit. He changed rear gear, Converter (2 times) and borrowed a known good PG Trans...

He took the engine to my buddies shop...we swapped the heads/and cam went back to the track and ran a 5.92 on his first pass.....

My take away

The biggest head and cam "might" make big power....but it doesn't mean it will be fastest
As long as the tesing is being performed correctly, and it is in the correct span, the one that makes the most power on the dyno will ALWAYS win! Fact!
Look elsewhere....... :wink:

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Re: Dyno HP vs driving feel

Post by Tuner » Tue May 15, 2018 10:04 am

Steve.k wrote:
Tue May 15, 2018 9:11 am
Im wondering if there are just things to look for on dyno. How the tq curve comes in and how long it stays in. That likely affects how car moves. The dyno is a useful tool to have, i dont believe that because it made a certain amount of power on dyno it wont move car. Its where the curve is at. The engine in dyno gets more load than it ever sees in vehicle.
On an engine dyno the load is released to allow RPM to climb, so the engine accelerates into a decreasing load as RPM goes up.

In a vehicle, the load of the mass of the vehicle is constant and aerodynamic drag increases to the square of the speed, so the engine accelerates into an increasing load.

An inertia dyno, like a Dynojet chassis dyno, or the engine dyno at BLP they did the Carb Shootout on, is a constant inertia load but obviously has no aerodynamic drag. Most dyno rollers weigh significantly less than the car being tested, so again the load is less than on the racetrack (or street) unless the car being tested is the same or less weight than the dyno roller.

This difference of load is one reason the ignition timing for best power on a dyno is usually too far advanced for best performance on the racetrack. I don't know where the idea comes from that timing should be advanced at the track beyond the amount that gave best dyno numbers. Because of the difference in load, the tune for best dyno numbers is usually too far advanced and too lean for best numbers on the track.

(As always, your mileage may vary. :roll: )

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Re: Dyno HP vs driving feel

Post by 427dart » Tue May 15, 2018 10:08 am

What was the engine setup in this F150? Was the F150 a stock cast iron 429/460 intake?
Maybe the Edelbrock Performer would give a better balance of HP/Torque between the stock manifold and the larger runner CJ manifold.

A bit different but same theme...I switched from a racy Eddy Super Victor intake manifold to my current dual Holley dual plane type on my 427 Windsor. The runners are smaller than the SV intake but the setup has better throttle response and mid range power below 5000 RPM and cruises at a much leaner A/F ratio now due to better A/F distribution and velocity thru the carb and manifold.

Since most of my driving has the engine running below 4000 RPM but with occasional WOT burst now and then it gives me the nostalgia Ford look with better street performance!

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