Easy way to add HP?

[moore_rb]

Originally Posted by olddog

They can angle the blades and make improvements, but a true centrifugal blower, the pressure output is proportional to the tip speed of the blades. The relationship is typically pretty close to: pressure equals tip speed squared. Since it is difficult to fit a 3 foot diameter blower in a car, they end up with a small diameter and a planetary gear set spinning the wheel up to 80,000 rpm to make pressure. At low rpm the boost is very low, with little increase in boost for a 1000 rpm motor increase. At high rpm, boost is high, and a large increase in boost for a 1000 rpm motor increase. Torque is proportional to boost, and boost increases with the rpm squared. This gives a very steep increase in torque over the rpm range, until the engine pumping efficiency starts dropping off rapidly. Once that point is reached, the centrifugal blower and engine combine to flatten the torque out for a while.

Multi stage compressors wheels exist in industry, but I have never seen them in an auto application. The pressure is still proportional to rpm, but not as steep. These need a good deal of application design and cannot handle a lot of variable changes, as they can get into vibration harmonics and destroy themselves. I don't see these going into auto applications, but I get surprised all the time. I just doubt that there is any centrifugal blower that doesn't have a steep rpm to pressure curve. Physics doesn't change much.

Now change to the roots bower, or better, a screw compressor and they are positive displacement blowers. You pretty much get the same boost pressure (thus torque) at all rpms.

So let's assume your engine NA has 300 ft-lb torque from 2500 - 4500 rpm and then it starts dropping off to say 250 ft-lb at 6000 rpm. With a centrifugal blower you may get 350 ft-lb at 2500 rpm at 2.5 psi boost. At 4500 rpm you are likely at 8.4 psi and 470 ft-lb. At 6000 rpm you are likely at 15 psi and 500 ft-lb. Some of that torque would be consumed by the blower belt, but that's more work than I wanted to put into this, so I am ignoring those losses.

In comparison if you used a positive displacement compressor at 15 psi boost (again ignore power robbed to drive the blower) you would double the torque everywhere. So cruising down the road and pulling up a mountain at 2500 rpm the positive displacement would would have about 600 ft-lb of torque available, where the centrifugal would only have 350 ft-lb available (only 50 more than the engine had normally aspirated). Sure drop two gears and rev it up to 6000 rpm, they both have the same torque, but every place below that, the positive displacement wins hands down.

I hate a different torque at every rpm. So you come out of the first turn at 2500 rpm smash it to the floor and get a modest 350 ft-lb of torque. Yea this is fun. The next corner you are at 4500 rpm and smash the throttle, expecting the same fun, only the engine pumps out 470 ft-lb of torque. The tires break loose on a corner, in a 90 inch wheel base car, and you are dead.

With the centrifugal smash it in first gear, and your tires will hold to the ground until the rpms come up. If you do not back off the throttle before the tires break loose they will rapidly go up in smoke. To keep the tires from breaking loose, you have to continually back off the throttle, as the rpms increase to keep the tires hooked. Same thing in every gear. Not for me.

We're still not talking about the same thing... You are still hammering on fixed ratio, belt driven superchargers... and I don't disagree with anything you wrote (yes, I read your WHOLE post )

However, what if the ratio of engine RPM to compressor RPM wasn't fixed? what if you could vary the impeller speed and set the boost level wherever you wanted it, at almost any RPM? What if your blower could be PROGRAMMED to work with a MAP sensor, and a variable speed transmission, to deliver more boost at lower engine RPMs, and less boost at higher RPMs in order to provide a nice, broad, flat torque curve...?

Yes, you sure can....

https://www.procharger.com/procharger-i1

[olddog]

Originally Posted by moore_rb

We're still not talking about the same thing... You are still hammering on fixed ratio, belt driven superchargers... and I don't disagree with anything you wrote (yes, I read your WHOLE post )

However, what if the ratio of engine RPM to compressor RPM wasn't fixed? what if you could vary the impeller speed and set the boost level wherever you wanted it, at almost any RPM? What if your blower could be PROGRAMMED to work with a MAP sensor, and a variable speed transmission, to deliver more boost at lower engine RPMs, and less boost at higher RPMs in order to provide a nice, broad, flat torque curve...?

Yes, you sure can....

https://www.procharger.com/procharger-i1

Wow I am behind the times. I read where one of the German car companies were experimenting with a continuous variable drive design on a positive displacement blower. If memory serves they were shooting for no throttle plate. Quite a few years back.

Ok now that I am up to date, yes that would work as you described.

Thanks for the link and explanation.

[MKS427]

Originally Posted by moore_rb

We're still not talking about the same thing... You are still hammering on fixed ratio, belt driven superchargers... and I don't disagree with anything you wrote (yes, I read your WHOLE post )

However, what if the ratio of engine RPM to compressor RPM wasn't fixed? what if you could vary the impeller speed and set the boost level wherever you wanted it, at almost any RPM? What if your blower could be PROGRAMMED to work with a MAP sensor, and a variable speed transmission, to deliver more boost at lower engine RPMs, and less boost at higher RPMs in order to provide a nice, broad, flat torque curve...?

Yes, you sure can....

https://www.procharger.com/procharger-i1

WOW, Impressive numbers on the Coyote! That could easily be 580 TQ at the crank.
I originally suggested a centrifugal, because I am not aware of a screw type for a 302 Windsor, that won’t pop up through the hood (bonnet).

[120mm]

Originally Posted by RB60

Cars are like women, the longer you have them, the less "exhilarating" they become.
.

I guess that means I'm not normal.

All my cars still turn my crank, but then, I've been married for 31 years and still think she's the sexiest thing out there.

[Anthony]

I would just replace the engine with a bigger one.

408/427 windsor vs 450 FE

I think this keeps it simple. I like simple .

[eschaider]

Originally Posted by Selo

3.55? 3.73?
How do you go about choosing a new cam, how expensive to replace (sounds labor intensive) and as long as we're going to be in there, what else to do?

**** Note: Vigilink is adding links that I did not put into this post. If the link is not Bold Face, Italic and Blue it is an unrequested Vigilink link that should be ignored. ****

This is not meant to be deprecating Mike, but it sounds like you are in the deep end of the swimming pool and you don't know how to swim.

I think you might want to step back for a moment and do a little preliminary work. The cost to supercharge, done correctly with proper plumbing, headers and management hardware (if a turbo), intake manifold, intercooler and proper compressor is basically a $10K proposition for a screw blower and 2x that number for a turbo build — before you get to engine internals.

Your questions about n/a engine mods betrays a lack of experience in that area also — again not trying to woof on you. These engine modification or replacement adventures get expensive fast and even more expensive if you have to repeat the experience because of poor choices having been made.

While mechanical experience with engine building can be a good thing if you own one of these cars it tends to fall into two (successful) camps. One is just the installation and ongoing maintenance of the engine car combination and the other is the recipe for making reliable, usable well mannered horsepower with the engine platform you decide to use. The skills sets sound similar perhaps even the same at first glance. While complementary, they are very different.

If you do not have a pressing reason to immediately change your cars engine, I would like to suggest that discretion is the better part of valor here. Get some books and read up on what it takes to build a good version of one of these cars. Try to stay away from the all too common versions that describe the problem from multiple perspectives and never offer an explanation or solution.

There are two excellent books I would point you at. One is, Internal Combustion Engine Fundamentals. The title makes the book sound like an entry level primer that is not worth the effort. It is written by John Heywood. John is a Professor of Mechanical Engineering and Director, of The Sloan Automotive Laboratory at the Massachusetts Institute of Technology — the book is not an entry level primer. It is course material used in graduate and undergraduate engine design courses at MIT. The book is also not inexpensive it is between $30 and $50 on Amazon to rent and anywhere between $100 and ~$300 to buy used. The most recent edition can be purchased for $100 and change directly from the publisher on Amazon. Not cheap but well worth the price.

Heywood's book will be more than you need for the adventure you are about to embark on but it will go to the engineering design principles behind every decision that is necessary to creating the engine you are looking for.

The second book I would point you at is Physics For Gearheads by Randy Beikmann Ph D. It is a bit less expensive at approximately $50+ per copy. Before you think this is one of those upper atmosphere exercises for some type of automotive dilettante, I would ask you to reserve your opinion for a bit. The book is an understandable teaching tour-de-force on vehicle dynamics, energy and power.

In his opening comments on page 1, the author offers the following thoughts, "I figured the ideal Physics book would combine the gearheads knowledge of cars with the physical explanations of how they work. Familiar car examples could make the physics practically obvious and the Physics could explain why the designs end up the way they do ..." As he closes his commentary he says, "... this book is for those same people who kept asking why. And who still want to know more today."

The book is excellent and provides it's explanations in a clear, concise manner with simple four function mathematics using only multiplication, division, addition and subtraction. If you want to get into the higher math proofs, there are also more sophisticated explanations provided that will provide you all the insight you may want.

If the math and learning stuff is a bridge too far, there is still a working solution available to you. You have two excellent engine building choices available to you on the Club Cobra site.. One is Craft Performance Engines and the other is Lykins Motorsports. These guys know our cars and can quickly set you up with the solution you are currently trying to noodle out.

BTW irrespective of which of the three paths you choose to take, if you do the job correctly, you will be in the tank for decidedly more than $10K by the time you get everything done and that is a conservative number. If you take a learn as you go approach you are probably well over $20K and run the risk of becoming one of those oh so many advertisers you can find that is selling a car nearly complete but needs ... fill in the blanks.

Pick your poison.


Ed

[Jdata]

look for easy convenience. Just be sure your internals of your engines are well-thought-out and just put nitrous oxide on it so you can get on it when you want to.

[Selo]

Awesome info Ed. Thanks. I'm the first to admit I don't have any experience in these matters and that's why I asked. I never learned how to work on cars - eyeballs instead. I very much appreciate the way you broke it down for me, I like the quick and dirty. Since I'm not at a place just yet to either read those books or do the work myself, I'd be looking to Craft or Lykins. At $10,000 minimum, I'm better off to buy a new car, I think, If I really feel I need more power. New gears will likely be worth it, but not a new motor or Forced Induction.
Thanks for helping me answer that question.

[twobjshelbys]

Originally Posted by RB60

Cars are like women, the longer you have them, the less "exhilarating" they become.
.

I'll take serious umbrage with that claim My wife of 44 years is still pretty hot.

[twobjshelbys]

Originally Posted by MKS427

3.55? 3.73?
Personal choice dependent upon tire size and trans gearing (.82 vs .64 OD), where cruising RPM should be tolerable to you.
You should be able to find a speed calculator online. Typically, you will need to know revolutions per mile for the tires.

What the discussion about transmission and rear end is really about is summarized as "it's not necessarily how much horsepower you have but how effectively you transfer it to the ground". The stuff behind the engine is just as important as the engine itself, and all need to be properly balanced. It does no good if when you step on the accelerator your wheels just spin on the pavement, which is what most "horsepower additions" yield.

[twobjshelbys]

Originally Posted by 120mm

I guess that means I'm not normal.

All my cars still turn my crank, but then, I've been married for 31 years and still think she's the sexiest thing out there.

As I wrote my response which is nearly identical to yours I wondered how many times he's been married (if at all )

[eschaider]

Originally Posted by Selo

Awesome info Ed. Thanks. I'm the first to admit I don't have any experience in these matters and that's why I asked. I never learned how to work on cars - eyeballs instead. I very much appreciate the way you broke it down for me, I like the quick and dirty. Since I'm not at a place just yet to either read those books or do the work myself, I'd be looking to Craft or Lykins. At $10,000 minimum, I'm better off to buy a new car, I think, If I really feel I need more power. New gears will likely be worth it, but not a new motor or Forced Induction.
Thanks for helping me answer that question.

These cars are extraordinary assaults on our senses, no matter what you have previously experienced in automotive performance vehicles. There is something I like to call the spectacle of speed, it is that assault. When you are in roadster like a Cobra, that can in almost any form run low eleven second / high ten second quarter mile performance, it is stunning and much more so because of the open cockpit.

I like to think about these cars as attitude adjustment vehicles. After you have been beat up and beat down during the week in our normal lives an eclectic spin through the mountain roads in a Cobra will bring you home feeling just about as good as is humanly possible.

Enjoy your car as it is today. Don't be too quick to sell your car and start over. You will not believe just how much the car's personality and character changes with a new engine that is several notches higher up the horsepower totem pole than your current engine.

Get close to both Lykins Motorsports and Craft Performance they are excellent and excellent falls short of the mark in expressing just how good they really are. Like most of us, your knowledge and expertise will grow with time and exposure to your car. Be patient. It's not just the end game that is significant. As you have probably heard before the journey is the real prize.

Take your time, measure twice (or more if necessary), cut once and your journey will be extraordinary!


Ed

[Ace23]

Keep it simple. Throw a 460ci Windsor in it and a some rear gear. Have a cam designed to peak at 5500. It will make great power everywhere and completely usable as these things have gas pedals and you don’t have to mash them to the floor all the time. I’ve got a 6-speed with a 4.30 rear gear and a 427 Windsor that spins to 7k...great street setup that can also scare the crap out of you.

[Ace23]

Keep it simple. Throw a 460ci Windsor in it and a some rear gear. Have a cam designed to peak at 5500. It will make great power everywhere and completely usable as these things have gas pedals and you don’t have to mash them to the floor all the time. I’ve got a 6-speed with a 4.30 rear gear and a 427 Windsor that spins to 7k...great street setup that can also scare the crap out of you.

[olddog]

Take a look at how much room there is between the engine and the car, especially on the sides. Also use some silly putty roll up about an inch diameter at maybe 3" long and put them around the air cleaner. Close the hood. Open the hood, and the smashed putty will tell you how much clearance you have.

A 351 windsor is the same engine family as the 302/5.0. Off the top of my head it is about 3/4" taller and about 1-1/2" wider. The heads interchange. Front to back the block is the same length. If there is plenty of room, I would go with that block. If not, I would go with a 347 stroker. There will be almost no extra work to put the 347 in, and it will be a little less cost.

If it will easily fit and it fits you budget go with a stroked 351W. I don't think the 460 cid stroker version is worth the extra cost, but some do. I think the 408 stroker is fairly inexpensive in comparison. Built mild you should have more power than you need.

No one has discussed radical cams and difficulty to drive. Even worse, longevity and maintenance. The more power you make out of the same CID, the more radical you have to go in the build, NA. If you focus on peak Hp, you end up with steep torque curve. A high radical idle. An engine that wants to buck and hop at low rpm. Generally has poor street manors and is a fuel pig. It will have a short life and require a lot of maintenance.

Understand your tolerance to all of this. You can also get an engine that makes good power everywhere, that is reliable and has good street manors. It will not hit the High Peak Hp of the radical build, but it could easily have more power at cruising rpm. Note that in these cars, you do not need huge Hp numbers. They are fast enough to easily get you killed at modest power levels. Don't get caught up in chasing huge Hp numbers. The fact is that you can take the same engine and have it dynoed many places and get just about any number you want. It's not an exact science, even though it should be.

[120mm]

olddog said what I mean in a much more succinct manner.

[olddog]

Originally Posted by 120mm

olddog said what I mean in a much more succinct manner.

Dang! I had to look that word up.

Not the first time I heard it, but its been so long I pretty much forgot it existed. But then again, I have forgotten more than I remember.

[AC Ventura]

I had a 5.0 Liter Efi in mine. 225bhp allegedly and it felt tame. So much so, I wouldn’t take my car buddies out in it. I looked high and low, but couldn’t find a fix. I think the ideal ‘driver’ Cobra has 400-450 hp. I changed mine to an FE, but that was for other reasons. If I was in your position and decided I liked the car enough to keep it (sounds questionable IMO) and just wanted more go, I’d stop wasting your time, give you old motor to a reputable builder and have a budget 331 or 347 built.

[120mm]

Originally Posted by AC Ventura

I had a 5.0 Liter Efi in mine. 225bhp allegedly and it felt tame. So much so, I wouldn’t take my car buddies out in it. I looked high and low, but couldn’t find a fix. I think the ideal ‘driver’ Cobra has 400-450 hp. I changed mine to an FE, but that was for other reasons. If I was in your position and decided I liked the car enough to keep it (sounds questionable IMO) and just wanted more go, I’d stop wasting your time, give you old motor to a reputable builder and have a budget 331 or 347 built.

I keep forgetting his real or username on this forum, but that is what "The Traveler" has in his. A fairly mild 347, and he does ok with that.

A driver quality 347 will make 400 hp/400 tq, and that should feel pretty good in a Cobra.

[Selo]

There doesn't seem to be a lot of enthusiasm for a Coyote.