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Subscribing for continued hilarity.

A normal engine doesn't have atmospheric pressure in the induction, they have a vacuum because they are sucking. Sucking takes energy. To have normal atmosphere you have to pressurize the induction.

At full throttle, MAP is nearly equal ambient pressure, which can be assumed when it's being tested to find maximum power.

pressure and volume are not the same.

Keep it civilized....

While I'm not in a position to argue all the physics discussed here, and I can't prove or disprove claims made by people either here or in other forums, claims of 2X stock horsepower for my donor engine with little more than an aftermarket turbocharger and intercooler kit are common in Mustang circles. Yes, everyone could be lying, but I don't think they're are all liars. There's just too many of them.

Wanting to illustrate the point (big HP gains from turbocharging), but not wanting to bore the pants off everyone by asking them to read many forum entries elsewhere (as I have), here are a few videos of dyno tests for the Ford 3.8 V6 turbocharged in several configurations. Not all are completely stock, one uses the 4.3L truck crank, but most are 3.8L and in street cars. Given the relationship of the engines, results from Buick 3.8L V6s might be a good substitute.

I don't expect these videos to convince everyone that the results are valid. I'm not claiming they are, or that videos make it so. But at least introduces the idea that these claims may be plausible and could even be truthful. Besides, it's more fun than looking at graphs! From what I've read, the stock 3.8 Mustang would dyno at around 150 RWHP (Rear Wheel HorsePower).


Cheers,

VIDEOS
=====

1) Claim: 309 RWHP, 2000 3.8L V6, stock internals, 10 PSI
Verification: None really, results of dyno test at end of clip
Sorry for the music. They do it because they can - suxx

http://www.youtube.com/watch?v=SmdYiP6QYbw

2) Claim: 474 RWHP, stock internals, No pressure given
Verification: Dyno screen shot, Verbal, multiple runs

http://www.youtube.com/watch?v=pMEkc0DD2Fw

http://www.youtube.com/watch?v=YjHnVodWKVM


3) Claim: 476, 557, 611, 579 RWHP, Twin turbos at Various Pressures for Modified 4.3L (Truck) version
Verification: Quick dyno screen shots, multiple runs

http://www.youtube.com/watch?v=OgqkOemJeQE


4) Claim: 434 RWHP, 3.8L V6, Modified internals, ~14 PSI
Verification: Dyno screen shot, Verbal

http://www.youtube.com/watch?v=0HWYq-WAGPU


5) Claim: 540 RWHP 3.8L V6, Modified internals, No PSI given
Verification: None what ever, could pie in the sky, but fun to listen to anyway

http://www.youtube.com/watch?NR=1&v=Vj2SrCskyoY

Yes indeed, twice the stock airflow and power is entirely realistic and fairly easy to achieve.


All seems quite reasonable.

Just realize that getting around 400 Hp from a modified 3.8 or 4.3 litre engine is entirely different to getting 400 Hp from a bog standard untouched 1.5 to 2.0 litre engine.

One requires maybe doubling the standard power.
The other requires perhaps a four times increase in power.

One is entirely realistic, the other dreaming with a stock internals and completely unmodified engine with standard compression ratio.

See if you can find a dyno sheet for a dead stock original unmodified 3.8 (that probably delivers around 165 factory Hp) boosted to 20 psi that delivers a genuine 660 Hp at the original rpm.

You can probably find a highly modified purpose built 3.8 that can make that sort of power at much higher rpm, with a lot of special non factory parts, but that is not what is being claimed.

This is a stock N/A engine like mine. Looks like its pretty similar until the boost comes on. I dont see what your talking about as this big power difference.

There's a pretty good introduction to turbocharging in a series of articles GM High-Tech Performance magazine ran last spring/summer. The articles uses V8's as their frame of reference but the info presented is relevant to 4's and 6's as well.

http://www.gmhightechperformance.com/te ... index.html
http://www.gmhightechperformance.com/te ... index.html
http://www.gmhightechperformance.com/te ... index.html

A lot of text is imbedded as picture captions, so one needs to click on the pictures to get the most out of the series.

While the articles didn't make a turbo guro out of me, they were a good Turbos for Dummies read.

o/k, here it is right from the Horse's mouth in the well known book "Maximum Boost" by Corky bell.



On page 12 he says:




So taking a two litre (122 cid) engine with 20 psi boost, we get:
Lowest ever measured power .052 x 122 x (20 + 14.7) = 195 Hp
Highest ever measured power .077 x 122 x (20 + 14.7 = 326 Hp

I still find 400 Hp at only 20 psi for two litres unbelievable.
The results go way beyond anything even Corky bell has ever seen on any engine he has ever tested, including prime race engines.

Its 300whp at 20 psi. 438whp at 28psi. And Corky was the man when carbs and 7:1 compression ratios were the hot ticket.

Carbs barely get a mention at all in that book.
And he specifically recommends higher compression.
Plenty on fuel injection and engine management in that book.

And 300 rear wheel horsepower equates to very close to about 360 engine hp on a hub dyno, and about 400 engine Hp on a roller dyno such as you used.

The book was published in 1997, and the laws of thermodynamics and engineering have not changed much in that time.

We have had almost new cars on the dyno and they tested right on calculated back to the crank. This is a dynojet and they all use the same wheel and they all read the same. This is the industry standard for measuring hp.

Dynojets may be the big thing in the US, but outside America they are not all that common.
Any chassis dyno is only really a tuning aid, and definitely not a reliable way to measure crank power.

I have found on my own home eddy current roller dyno, that how hard I tie it down , and tire pressures, and what gear I am in, all influence the readings. But it is great for mapping fuel and ignition timing, and locating problems, which is all a chassis dyno is really good for.

This thread is about realistic turbocharged engines for Lowcost applications.
Turbos are fine, my current road car has a turbo.
But leading people to expect a trouble free three and a half times power increase with 10:1 compression ratio and 20 Lbs boost goes way beyond being realistic.

Im curious what kind of dyno you have? We have a dyno dynamics and a dynojet.