ducktail and hp increase

[florent78]

Hi gus

I read on several mags the ducktail was build to increase airflow to the engine as well and it gives a slight increase in HP

did someone do a test before (no ducktail) after (ducktail) on a dyne and notice a real improvement, so more than 1 or 2 hp


thanks

[douglas bray]

You would need a wind tunnel to test this theory. A dyno is a stationary testing tool. 8/

['76 911S 3.0]

I don't know about horsepower increase, but when my thermostat was unknowingly stuck closed I saw lower oil temps with the duck as opposed to without (no front cooler, just engine mounted).

[Speed metal]

The cool factor alone raised my HP instantly!

[douglas bray]

Originally Posted by Speed metal

The cool factor alone raised my HP instantly!

You could not be more correct

[Reiver]

Mine is even faster in reverse with the duck!

[Bill Verburg]

Originally Posted by florent78

Hi gus

I read on several mags the ducktail was build to increase airflow to the engine as well and it gives a slight increase in HP

did someone do a test before (no ducktail) after (ducktail) on a dyne and notice a real improvement, so more than 1 or 2 hp


thanks

Most spoilers increase air pressure and laminar flow across the top of the spoiler where the cooling and consumed air is ingested, since engine air intake is through the area it will make for a slight increase is charge density which means a slight increase in hp.

Whales are more efficient in this regard too.

[Trackrash]

I thought spoilers spoiled the laminar flow.....

[jeffbottman]

My ducktail raised my 86 Targas RWHP to 211! I'm sure it has nothing to do with my Steve Wong chip and M&K muffler!

[florent78]

So i will do the test in a few weeks

[chrismorse]

Originally Posted by florent78

Hi gus

I read on several mags the ducktail was build to increase airflow to the engine as well and it gives a slight increase in HP

did someone do a test before (no ducktail) after (ducktail) on a dyne and notice a real improvement, so more than 1 or 2 hp


thanks

IIRC, In this iconic book, Paul stated that the factory was making a real effort to reduce high speed rear lift (390 down to approx. 180 pounds).
The duck also moved the aerodynamic center of pressure rearward,, thus reducing side wind induced instability.
He also mentioned that the duck also slightly, (1-2%), reduced the aerodynamic drag.

I have seen a couple of threads mention a noticeable reduction in oil temps going back and forth between stock engine lids and ducks, although, I am at a bit of a loss to explain why, given that the oil flow to the coolers is controlled by 1 or 2 thermostats. We are left with the assumption that the duck increases the flow of air into the engine compartment to benefit both cooling and Hp.

My 74 is down for a front end refresh and a duck instalation, but, I am thinking about doing a before and after engine compartment air pressure test, at roughly 100mph, just a quick test, si I don't get busted.

Chris

[WP0ZZZ]

Originally Posted by florent78

did someone do a test before (no ducktail) after (ducktail) on a dyne and notice a real improvement, so more than 1 or 2 hp

You would not see the difference on a dyno since there is no car velocity and therefore no increase in pressure in the engine bay due to the ducktail.

Originally Posted by chrismorse

We are left with the assumption that the duck increases the flow of air into the engine compartment to benefit both cooling and Hp.

When the car is moving the ducktail creates a high pressure zone just in front of it which leads to an increased pressure in the engine compartment since the grille is located right in front of the spoiler.

Originally Posted by chrismorse

My 74 is down for a front end refresh and a duck instalation, but, I am thinking about doing a before and after engine compartment air pressure test, at roughly 100mph, just a quick test, si I don't get busted.

That will be an interesting test!

[MBruns]

It increases the HP thru the corners with downforce
Mike

[panzerfaust]

Originally Posted by Trackrash

I thought spoilers spoiled the laminar flow.....

in the ducktail case, yes. i believe it would break up the laminar flow on the decklid to reduce lift and create high pressure on the face of the spoiler

[cmcfaul]

The ducktail does not add much downforce. It reduces the amount of lift or negative air pressure in the rear of the car. While driving without a ducktail, air is drawn out of the engine compartment by the lift thats created (like the wing of an aircraft). The engine fan and intake are fighting with the negative air pressure. With the Duck, there is neutral or just a bit of positive air pressure. This will definitely give a bit of extra cooling CFM's and intake CFM's to the engine. Plus it just looks real cool.

Chris

[florent78]

The tuner i m doing the dyno have a huge fan to simulate high speed
So for sure it s different from real world
But it will give a good indication

[Busta Rib]

duck tail = 1-2 hp
Pegasus decals = 5 hp

Luckily I have both!

[Flojo]

Originally Posted by florent78

I read on several mags the ducktail was build to increase airflow to the engine as well and it gives a slight increase in HP

it rather helps the rear to downforce for more traction an high-speed-stability.
only in combination with front lip!

1970 911 RS clone Aerodynamics question

Originally Posted by florent78

did someone do a test before (no ducktail) after (ducktail) on a dyne and notice a real improvement, so more than 1 or 2 hp

honestly, it DOES help! without lip 'n tale running upt to 220 on the straight was sweatty. now I run full limot with my SC 240 and feel way safer.