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

[Anthony]

Originally Posted by DAVID GAGNARD

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.............

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............

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.............

I don't think that you can really make any statement about driveline loss only with information from a chassis dyno. I would think that you would have to also dyno the same engine on a stand, using the same dyno, with the same air intake set-up and exhaust system to get a real % driveline loss, otherwise you're just guessing.

Originally Posted by 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.

I don't think it really matters, as the dyno knows the overall gearing from the engine rpm and wheel speed, and I doubt there would be a large percentage loss in the transmission using 3rd gear instead of 4th. Anybody know what the hp loss would be ? Maybe 5-10 hp?

[Excaliber]

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).

[DAVID GAGNARD]

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

[Excaliber]

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).

[neverwouldof]

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][/IMG]

[Excaliber]

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'.

[SL]

nice numbers, is that a chassis or engine dyno

[RACER X #99]

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.

[neverwouldof]

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?

[Dwight]

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

[ByronRACE]

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.