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

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- - Dynoed my 427so Cobra today.... interesting to say the least! (http://www.clubcobra.com/forums/all-cobra-talk/72786-dynoed-my-427so-cobra-today-interesting-say-least.html)

Quote:

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.

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.

The problem with running ANY gear other than a 1 to 1 ratio through the trans is parasitic loss. 1 to 1 is NO GEARS at all, straight through to the rear end. Any other gear is a reduction or an over drive. It should not be under estimated what horse power could be lost due to a compounding gear arrangement (like 3rd).

Keith;

My MSD distributor has 22 degrees built in,so we set it at 8 degrees at idle and started there, that gave me a total of 30 degrees............my timing starts coming in at around 2250 prms and is all in by approx. 2800 rpms........after a 30 minute brake-in run with the timing set at 8 degrees we began making pulls....started at 5000rpms and increased each pull by 500 rpms till we got to 7000rpms......I lucked up and hit the carb jetting just right, so we never changed jets, a/f was right on from the get go, then we began making 6500 rpms pulls and retarded/advanced the timing by 2 degress each time, found my set-up liked a total of 32 degrees, then locked it down right there.........

Clay; I was amazed to see how little loss those GTs showed, I saw them do 3 of them back to back, all bone stock, they did 3 pulls each, and the results were the same, no fluke there either.........I would think the advertised 300hp should not vary more than a few hp from engine to engine.........I guess the new technology and driveline components are just that much better than the "old stuff" and I'm sure some of the new fluids are also way better than say 20 years ago..........still very impressive numbers any way you cut it.........

Had I not been there and seen it for myself, I know I would have a hard time believing some of those numbers..........not sure about the GTs, but I think all the Vettes come with all synthetic fluids, that's gotta help also..............

David

Of course the MSD's can be modified for TOTAL advance AND how fast it comes in by changing the springs and 'stop' button.

I changed mine from stock to a total advance limit of 18 degrees so I could run more 'base' timing, which my motor likes (and NEEDS to have).

10 Month update...lol

Well boys.... after a few thousand bucks and replacing and renewing lots of parts... here are new numbers! Let me know what you see in the dyno sheet. He ended dyno run around 5900 rpm and it was still climbing which i though was strange for big block's. It does have 7000rpm rev limiter but i told him 6k should be enough. Don't the bigblocks edge over around 5500 rpm? Running amazing after replacing distributor with rusty springs and fuel pump and remanufaturing the 1968 carbs to like new and so on... nice 1/2 gallon of water in aluminum fuel tank thanks to sitting i'm guessing for the last 9 years. Only thing left is to check brakes and lines on the big alcon brakes...

How do the numbers look now?

Keith

[IMG]http://www.clubcobra.com/photopost/d...so_7-17-07.jpg[/IMG]

Where big blocks (or any block for that matter) 'nose over' is entirely dependant on the induction system. Side oilers were built to turn 7000 or higher. Mine, with radical cam, high riser heads and 2X4 intake loved 7000 plus! Now I'm sporting a milder cam and 6200-6400 is about where it 'noses over'. :D

nice numbers, is that a chassis or engine dyno

Not bad numbers makes almost as much as my Dart small block 408 built by the same engine builder, Dennis Hoffman. I alway knew I could kick Freddy's ass.:LOL:

Those are chassis dyno #'s.... It's a 23 year old in ground dyno which he didn't sound so sure how it was running anymore. He did say he was searching for new one but guess it doesn't matter as long as he gets A/F right. He left it just tad rich to keep on safe side. At what RPM do you think HP would have peaked?

I had my Cobra dyno'ed in Memphis, Tn. at Dyno Speed Racing, they do a "lot" of Mustangs. Joe told me most stock 05-07 Mustangs dyno at 280-290 rwhp. He said that would be 330 flywheel range. Ford was sued for their advertised HP on the 03 or 04 Cobra Mustang. I think they now advertise a HP rate they know will pass on any dyno.

Dwight

http://www.clubcobra.com/photopost/d...m/DSCN1021.JPG

Your engine has not even reached peak torque by that RPM! What is the cam duration on intake and exhaust? If you want to see what this engine is really capable of, you're going to have to spin it at least another 1500 rpm; maybe more. Your peak power will occur somewhere about 1000-1500rpm beyond peak torque. It'll break 450 at the tires...probably 470.

The dip in the 4000rpm range could quite likely be detonation. Why? Your air fuel shows choppy readings, torque drops, then as piston speed increases, it recovers. It may need a little less spark in that range. Read the plugs...see if they are speckled. Listen critically in that rpm range for ping.

Air/Fuel looks quite good. It probably won't get much better with a carb, but if you have some magic way of leaning it out 1/4 to 1/2 a point up high, it'll help your power numbers. If not, we're only talking about 15hp probably.

Byronrace, ya the dip he said was when the vacuum secondaries kicked in. This is two 1968 Holley 735's on a 1968 tunnel port and he said he could lean it out a bit and get 10-15 more HP but i said if a bit rich is safer then stick with that. It's still NOS 1968 std bore block and i don't want anything bad happening !!! And i later found out that the matched carbs were built for the 427FE as well which is nice to learn... think they were listed for a dragster. I'll probably take it to a local dyno shop to get a 7200rpm run and i'll post that up. Oh byron, I have the iridium plugs by the way and it does have large gap of .44 or .45 if my memory is correct. Oh and i switched to the cast aluminum valve covers which fixed the oil splashing into breathers. Had the chrome pent roof i believe they are called.

OK, vacuum secondaries. I'll buy that.

The engine is running great; and you have a point...if you're happy with how it goes down the road, there's not much to gain (except risk) by increasing your RPM limit. I'm certain you have enough power/torque to scare yourself, so take the next suggestion with a grain of salt.

If you're not comfortable running the engine up to where it's currently making the power, consider a cam change. By shortening the duration of the cam, you will increase the area under the torque curve in the region you are comfortable running it, while at the same time creating a "natural" rpm limit. The engine will peak lower and make more torque, the power will go peak and flat sooner, and you won't be as tempted to keep your foot buried as the engine soars into the rpm range you're not wanting to run in. Right now you have a 7000-7500rpm engine and I'm sure it's pulling like a freight train right up to where you abruptly bump the limiter, leaving you with the feeling that there's a ton more up there if it were allowed. If that's not what you want, a cam change will give you a 6000rpm engine and a more natural feeling as you approach the rpm limit. Less duration will smooth out your idle as well. Depending on your taste, this may not be desirable. Part of a cobras personality is the idle note/beat.

There's nothing wrong with running it just like it is. You probably can't connect more torque anyway...so its pretty much academic, take it for what it is. I don't think there's a thing wrong with the way your engine behaves. I bet it's a blast.

Quote:

Ford was sued for their advertised HP on the 03 or 04 Cobra Mustang.

Are you sure about that? Those motors are generally underated big time. I had an 03 Cobra that dynoed at 394 rwhp. They were rated at 390 bhp. I believe it was the 99 Cobra didn't meet the advertised numbers and an intake swap was made on Fords dime.