Dynoed my 427so Cobra today.... interesting to say the least!

[Dennis Kelley]

Your car has a very big lean spot at 3000 rpms. You may need to do some more tuning on the carb. Its killing your torque.

Later

dennis

[Excaliber]

When I remove the side pipes and bolt on my shortys I can FEEL the difference big time. MUCH faster with the open headers.

Standard TKO type trans could either .6 or .8 in 5th gear, for sure it's overdrive, use 4th on a dyno. With the Richmond running in 4th (not 1 to 1 in 5th) I would expect a substantial drive train loss, that pretty much kills any dyno numbers and puts you back to square one.

[427Aggie]

What air cleaner were you running on the 2 fours when you dyno'd it? If its those little chrome things one for each carb..then I know where some of the power went.

On my ERA I gained over 40 lb of torque from just changing to the stainless pipes with less restrictive mufflers...and 18-20% loss would be about right...Again if you have those 2 chrome air cleaners on the carbs those will suck the life out of a motor because it can't get enough air!

matt

[neverwouldof]

Originally Posted by 427Aggie

What air cleaner were you running on the 2 fours when you dyno'd it? If its those little chrome things one for each carb..then I know where some of the power went.

On my ERA I gained over 40 lb of torque from just changing to the stainless pipes with less restrictive mufflers...and 18-20% loss would be about right...Again if you have those 2 chrome air cleaners on the carbs those will suck the life out of a motor because it can't get enough air!

matt

The sidepipes are less restrictive and baffeled. They are not quiet by any means and were designed to be less restrictive then the sidepipes originally on there. I did question the air cleaners.... they are the double 8" round oil soaked style like K&N. Just looking at them i couldn't imagine getting a great deal of air through. However , what other choices do i really have in that?

Thanks for your inputs!!!

[eschaider]

Look at your A/F ratio. You start to go lean at about 2200 rpm. You reach a maximum lean of nearly 18:1 A/F ratio before 3000 rpm. You don't come back to the ranch until almost 4000 rpm. You have a fuel delivery problem! Don't know where it is but you have it big time. You might check float levels, needle and seat assemblies (less likely). The fuel pump's ability to supply high volumes on short notice, with adequate pressure ...

Engines make power by burning fuel. The more you burn (at the right A/f ratio) the more you make. Timing is absolutely essential to making power, be sure to check out your ignition system.

When you fix it get ready for robust numbers and performance and a lot of driving pleasure. Low speed torque is the stuff dreams are made of.

Ed

[Excaliber]

When I run at the drags I remove air filters and sidepipes and usually change jets as well. If not, I'm solid in the 12's instead of 11's.

[427Aggie]

Some of the ones I have seen are the large K&N Filters..but to fit under the hoods you need to have a drop base made for the air cleaner...Rob at Keith Craft Motorsports has made a few for some of keith's cars...he can speak more to what the small 8's will do to your power...Also what mufflers are in the pipes..you should see some of the ones that have been taken off...Rob has a brand he replaces SPF's with and gets quite a HP gain.

Matt

[neverwouldof]

Originally Posted by 427Aggie

Some of the ones I have seen are the large K&N Filters..but to fit under the hoods you need to have a drop base made for the air cleaner...Rob at Keith Craft Motorsports has made a few for some of keith's cars...he can speak more to what the small 8's will do to your power...Also what mufflers are in the pipes..you should see some of the ones that have been taken off...Rob has a brand he replaces SPF's with and gets quite a HP gain.

Matt

I will look into this..... Thanks!

Keith

[Excaliber]

My dyno work is done 1/4 mile at a time...

[DAVID GAGNARD]

What Roger was saying about headers/fuel and other things on the engine dyno will make a lot of difference..............


For instance;when I dynoed my 331 cu in "race" motor, they told me to make sure I LEFT the water pump at home, the same with my mechanical fuel pump.........a water pump and mechanical fuel pump can "eat" 20 hp depending on their type!!!!!!!!!!!!

I had no choice about the water pump as that was the way the dyno was set-up(they had an electrical water pump,NO engine power loss there), but I did use my mechanical fuel pump and brought my own race gas and used my headers instead of the shop headers............once we made about 8 or so pulls and got the timing/fuel mixture right where it needed to be, I added my air filter and luckily for me only loss 2hp with my air filter........

I specifically used my fuel/fuel pump/headers/air filter cause that's the way it was to be run in my car and it would give me more accurate #'s, the main # I was worried about was the a/f ratio, changing air filters/headers can and will affect that # to some degree..........

Now I run the snot out of the little motor and do not worry about going lean and melting a piston.......I have not had the time to get the car on a chasis dyno, but plan to do so soon.......

David

[ByronRACE]

Why use a chassis dyno? Confirmation of the known and/or measurement of the unknown. The former, is what causes most problems because it causes controversy. There is usually a gigantic discrepency between most engine builder figures and what is actually measured; even when accounting for drivetrain losses. I've personally dyno'd over 1600 Ford powered cars on a dynojet 248 and can count the number times on one hand that a SBF or BBF actually exceeded 1rwhp per cubic inch on pump gas without a power adder. Compare that experience with the number of engine advertisements with power figures that would EASILY exceed 1rwhp per cubic inch in a car, and you have discovered the root of the problem...marketing fudge factor; big numbers sell engines.

As far as dyno accuracy is concerned, I've compared engine dyno to chassis dyno directly, with a variety of transmissions and have a very good idea regarding 5spd drivetrain losses for various transmissions (within 5%). I've also then taken the same car from the chassis dyno to the street, and produced horsepower/torque functions using dataloggers and simple physics...mass, time, speed...and produced the same data (within 5%) of the chassis dyno.

So, for example...

If you had an engine dyno that showed 600fwhp, and put that engine into a car with say a T5 transmission and 8.8 Ford rear, and did a 4th gear pull that that read 400rwhp... and your engine builder is telling you it's because of the water pump, alternator, and drivetrain losses...there's more to the story.

600fwhp
- 13-15% for drivetrain losses (90hp max)
- 5% for max accessory losses (30hp max)
- 5% fudge factor for tire slip, calculation error, whatever (30hp max)

So worst case, the chassis dyno should read at LEAST 450rwhp for an engine advertised at 600fwhp. In reality, it should read higher because the error isn't truly cumulative as shown above; some losses are related.

Most of the time, a 600fwhp advertised engine will dyno at 400rwhp or below. And, the same 600fwhp engine as tested on your own engine dyno will read far less than 600fwhp; which is even harder to explain away. This is all too common and expected.

In your case, after reviewing the dyno graph, peak torque is at at 5200rpm and peak power has been reached by 5800rpm. As advertised, the engine was supposed to reach peak power by 6700rpm. Either the intake/exhaust geometry has changed dramatically; or the cam or cam timing has changed dramatically since it was dyno'd. If you corked the intake with air filters, it would not change the location of the peaks by nearly 1000rpm; it would just change the amplitude of the high rpm portions of the graph. Same is true for exhaust corking (mufflers). My guess is it's not the same cam, or perhaps not the same cam timing. Furthermore, changing the cam timing after achieving a peak number on an engine dyno isn't unheard of...it's done to produce more bottom-end torque to make the car idle better and be more fun to drive in the rpm band you use the most. You can make a better high rpm number by retarding the cam a bunch, but it may not idle / drive worth a damn...so you compromise. If I had to guess, something like this is what took place. Either that, or the cam is the same and they had a very different intake/exhaust system on the car when it was on the engine dyno. Race gas and timing advance would help amplitude as well, and shift the RPM slightly higher...but I wouldn't expect 1000rpm out of fuel/timing alone.

Either way, you' still have a great running engine approaching 1rwhp/cubic inch at the tires...and that's nothing to be ashamed of.

[DAVID GAGNARD]

When I was dynoing my motor, as we were bolting it on the dyno, the operator began asking me specifics about the engine, I told him the cam specs/compression etc.,etc., he then asked what I EXPECTED out of the motor........I told him I would hope for 475 hp, but would be very happy with an honest 450hp with a good a/f ratio(it made 472hp@ 6400rpms)........He told me I would NOT leave disappointed, cause I was being very realistic about my motor!!!!!!!!!!! I DID NOT leave disappointed at all.........

He said he has dynoed a ton of supposedly 600hp pump gas motors that barely made 400hp and made for some very angry owners........

Keith;even as such, you still have one heck of a motor and car, if YOU are satisfied with the performance, that's all that counts, regardless of any dyno #'s..........

David

[neverwouldof]

Originally Posted by DAVID GAGNARD

When I was dynoing my motor, as we were bolting it on the dyno, the operator began asking me specifics about the engine, I told him the cam specs/compression etc.,etc., he then asked what I EXPECTED out of the motor........I told him I would hope for 475 hp, but would be very happy with an honest 450hp with a good a/f ratio(it made 472hp@ 6400rpms)........He told me I would NOT leave disappointed, cause I was being very realistic about my motor!!!!!!!!!!! I DID NOT leave disappointed at all.........

He said he has dynoed a ton of supposedly 600hp pump gas motors that barely made 400hp and made for some very angry owners........

Keith;even as such, you still have one heck of a motor and car, if YOU are satisfied with the performance, that's all that counts, regardless of any dyno #'s..........

David

I am satisfied with the car by all means, i just wanted to make sure i got what i paid (57k) for..... it sounds like i did and i just need to have it looked over. It has a big hesitation when you get on throttle... not sure if sitting for two years had any effect on lines or pump. The carbs were rebuilt though. we'll see but i'm more optimistic after all the help on here.

Keith

[Excaliber]

Man thats gotta make the heel\toe thing a real bear...

[John McMahon]

...personally, I never even noticed it when driving.

I don't know how tall Keith is or if this is his first Cobra or not, but the pedal thing is just "one of those things" you need to get used to in a Cobra.

While the setup varies from manufacturer to manufacturer, I think we have all had to adjust to the pedals being off center left from a normal driving position.

[neverwouldof]

Originally Posted by Excaliber

Man thats gotta make the heel\toe thing a real bear...

Heel/toe driving is impossible.... i'm going to try and get it set up differently. I'm 6'2 and it has a dropped box in it. but my left knee is still crammed between steering wheel and door sill. Fred must have had short legs or been no taller then 5'10. Also going to have seat position moved 1.5" back which is far as it will go.

[DAVID GAGNARD]

Went to a Mustang Club car show today, brought my race car and my daughter drove my 65 Fastback and I entered it under her name, I only go to 2 or 3 "local" cars shows a year and this is my favorite........good folks and everyone has a good time, great club, they make everybody feel "like family"..........

Well, anyway, they had a couple of guys there with a chasis dyno and was charging 25 bucks a run........it was the kind on wheels (big trailer looking thing) about 6 or 7 feet off the ground.......they probably dynoed 6 or 8 cars and after the judging I tried to get my car on it, been wanting to chasis dyno my car since it has been finished.........well, it did not happen, ramp was too steep and my header collector flanges hit and I needed another 2 inches of clearance to get it up there, we tried adding some boards under the tires, but could not make it work............

So I'm interested in some results and watch them dyno 4 cars, the results were very suprising to say the least.........

Cars 1 thru 3, all 05 Mustang GTs, all 3 bone stock except for maybe a K & N air filter, that's it..........all 3 made from 262rwhp to 267 rwhp, they are adveritsed at 300 flywheel hp!!!!!!!!!!!! that's from 13% to 11% driveline loss, I think either Ford "fudged" those #s a little or else the driveline is very efficent.............

Now the kicker, car 4; 1969 Mach I, 428 Cobra Jet motor, I think these were rated at around 335hp to 350hp???? not sure........anyhow the owner said this motor had about 500 miles on it since a complete rebuild, he added Edelbrock alum heads,headers,big loud Flowmaster dual exhaust,850 cfm Holley, more cam??? not sure how much, not extremely wild, but better than the stock cam, electronic ignition.........now this motor was not an all out motor, but a "healthy" motor, which he estimated to make about 450 hp at the flywheel, never been dynoed, just his estimate, which could be achieved with what he had in the motor.............he ran it up to 6500rpms each of his 3 pulls............

Pull # 1, why he started from a dead stop in 4th gear, I'll never know, but he did, not very good #s, don't remember the exact #, but the owner said it had to be wrong.....I thought the motor loaded up real bad and he probably fouled the plugs some..........

Pull # 2; pretty much the same as # 1, except he starts out before they had the laptop ready and got some wierd readings, so they discounted the whole run.........

Pull # 3; operator told him to start in second gear and do the pull in 3rd gear, again, have NO CLUE why they would do it this way, but they did, I was standing near the rear of the car watching the driveline, he was running WAY,WAY rich by now, both exhaust pipes looked like a diesel truck going up a steep slope loaded down,he made 272 rwhp!!!!!!!!!!!!! when he shut it down and the operatpr showed him the #s and the printout, he was pi$$ed and told them to unhook the car and guide him down......they had a few words and he left, was only charged for 2 runs.........

Later talking to the operator he told me the "average" loss he has seen for late model cars with a stick shift was 15%........

The old Mach I was running a 4 speed toploader and 9" rear end with 3.89 rear gears, he had on a set of drag radials and as I was watching the rear of the car of his last pull, I did not see any signs of his tires slipping or spinning on the drums.........he had a very badly tuned motor, no doubt, but still thought he should have made from 350 to 375 hp at the wheels, he was about 100hp off............

Looks like I will not get a chance to do my car as those portable units are just to steep for my low sitting car............

I was very surprised at the low % of loss for the 05 GTs and very suprised at the high? % loss for a 428 Cobra Jet motor, sure thought it would have done a lot better.............

PS: almost forgot, I took second place with the race car and my daughter took a first place with the Fastback, boy was she proud!!!!!!!!!!!we had a great time together and I think she may be turning into a full fledged waxer now...........

David

[clayfoushee]

Originally Posted by DAVID GAGNARD

Went to a Mustang Club car show today, brought my race car and my daughter drove my 65 Fastback and I entered it under her name, I only go to 2 or 3 "local" cars shows a year and this is my favorite........good folks and everyone has a good time, great club, they make everybody feel "like family"..........

Well, anyway, they had a couple of guys there with a chasis dyno and was charging 25 bucks a run........it was the kind on wheels (big trailer looking thing) about 6 or 7 feet off the ground.......they probably dynoed 6 or 8 cars and after the judging I tried to get my car on it, been wanting to chasis dyno my car since it has been finished.........well, it did not happen, ramp was too steep and my header collector flanges hit and I needed another 2 inches of clearance to get it up there, we tried adding some boards under the tires, but could not make it work............

So I'm interested in some results and watch them dyno 4 cars, the results were very suprising to say the least.........

Cars 1 thru 3, all 05 Mustang GTs, all 3 bone stock except for maybe a K & N air filter, that's it..........all 3 made from 262rwhp to 267 rwhp, they are adveritsed at 300 flywheel hp!!!!!!!!!!!! that's from 13% to 11% driveline loss, I think either Ford "fudged" those #s a little or else the driveline is very efficent.............

Now the kicker, car 4; 1969 Mach I, 428 Cobra Jet motor, I think these were rated at around 335hp to 350hp???? not sure........anyhow the owner said this motor had about 500 miles on it since a complete rebuild, he added Edelbrock alum heads,headers,big loud Flowmaster dual exhaust,850 cfm Holley, more cam??? not sure how much, not extremely wild, but better than the stock cam, electronic ignition.........now this motor was not an all out motor, but a "healthy" motor, which he estimated to make about 450 hp at the flywheel, never been dynoed, just his estimate, which could be achieved with what he had in the motor.............he ran it up to 6500rpms each of his 3 pulls............

Pull # 1, why he started from a dead stop in 4th gear, I'll never know, but he did, not very good #s, don't remember the exact #, but the owner said it had to be wrong.....I thought the motor loaded up real bad and he probably fouled the plugs some..........

Pull # 2; pretty much the same as # 1, except he starts out before they had the laptop ready and got some wierd readings, so they discounted the whole run.........

Pull # 3; operator told him to start in second gear and do the pull in 3rd gear, again, have NO CLUE why they would do it this way, but they did, I was standing near the rear of the car watching the driveline, he was running WAY,WAY rich by now, both exhaust pipes looked like a diesel truck going up a steep slope loaded down,he made 272 rwhp!!!!!!!!!!!!! when he shut it down and the operatpr showed him the #s and the printout, he was pi$$ed and told them to unhook the car and guide him down......they had a few words and he left, was only charged for 2 runs.........

Later talking to the operator he told me the "average" loss he has seen for late model cars with a stick shift was 15%........

The old Mach I was running a 4 speed toploader and 9" rear end with 3.89 rear gears, he had on a set of drag radials and as I was watching the rear of the car of his last pull, I did not see any signs of his tires slipping or spinning on the drums.........he had a very badly tuned motor, no doubt, but still thought he should have made from 350 to 375 hp at the wheels, he was about 100hp off............

Looks like I will not get a chance to do my car as those portable units are just to steep for my low sitting car............

I was very surprised at the low % of loss for the 05 GTs and very suprised at the high? % loss for a 428 Cobra Jet motor, sure thought it would have done a lot better.............

PS: almost forgot, I took second place with the race car and my daughter took a first place with the Fastback, boy was she proud!!!!!!!!!!!we had a great time together and I think she may be turning into a full fledged waxer now...........

David

David, I've been wondering the same thing lately. I had always expected 20-25% loss as standard. When the new Z06s showed up advertised as 505HP, I was shocked to see most getting 450 RWHP bone stock, some a little more, some a little less, but a whole bunch of them very close. So many have been tested by owners, it's not a fluke.

Only 11-12% loss is amazing in some modern cars, assuming, of course, the advertised ratings were not understated.

[ByronRACE]

13-15% is normal drivetrain losses for a typical modern rwd manual transmission Ford. And by modern, I mean about 1985 and later. That loss was confirmed on multiple occasions using a superflow engine dyno and a dynojet chassis dyno at Mustang Ranch in Santa Clara, CA.

260+rwhp for a new manual transmission Mustang sounds about right. My 03 4.6L Marauder daily driver with the slushbox pulls 250rwhp on a dynojet 248.

[Excaliber]

That Mach 1 pulled in 3rd gear, again, if your not in a 1 to 1 gear ratio you can throw out the results.