Dyno results..

[patrickt]

Originally Posted by iwantacobra427

... "don't make the mistake of trying to compensate for lack of size in another area like some 427 Cobra guys".

Some; not all.

[razerwire]

Just returned from Las Vegas, went to Kroyer to check engine tune because I thought the engine was running hotter than normally. I can say I was more than a little nervous to see my car all strapped down to get checked out. Kroyer uses a SuperFlow dyno. Runs were made to check part throttle, full throttle and all between. Power runs were held to 6000 r.p.m. Best was 460 tq at 4600 r.p.m and 490 hp at 6000 rpm and still pulling. It was nerve racking to listen to test, I thought engine was hitting 10000 r.p.m untill I went inside and could watch screen. Car runs even better and it run good before. Would recommend to get the most out of your car to do it.

[Got the Bug]

Originally Posted by DAVID GAGNARD

Depending on your sidepipes and a few other things, using a 20% driveline loss, that would come out to around 360 hp at the crank....I think that would be about right for your combo.........

David

So 20% to 25% is a good rule of thumb to calculate the loss from the crank to the rear wheels?

I guess I don't need a dyno to tell me I have enough oomph! The dyno tag on my Roush 402SR/TW came back at 486 HP and 496 Torque at the crank. Less 20% and I've still got more than I need for street use.

[Power Surge]

Originally Posted by Got the Bug

So 20% to 25% is a good rule of thumb to calculate the loss from the crank to the rear wheels?

I guess I don't need a dyno to tell me I have enough oomph! The dyno tag on my Roush 402SR/TW came back at 486 HP and 496 Torque at the crank. Less 20% and I've still got more than I need for street use.

In my experiance dynoing Cobras, that's a pretty valid loss figure.

Also, so many people get caught up on dyno numbers, because they spent big bucks for more motor than they really need because they paid for big power numbers. The reality is the cars are plenty fast regardless of what numbers show compared to what they expected.

My FE powered CSX makes 320 rwhp and is FAR from "slow".

[patrickt]

Originally Posted by Got the Bug

The dyno tag on my Roush 402SR/TW came back at 486 HP and 496 Torque at the crank. Less 20% and I've still got more than I need for street use.

Lop off 85 horses for the pipes, 20% drive train loss, and you're down at PowerSurge's rear wheel numbers.

[DAVID GAGNARD]

Originally Posted by Got the Bug

So 20% to 25% is a good rule of thumb to calculate the loss from the crank to the rear wheels?

I guess I don't need a dyno to tell me I have enough oomph! The dyno tag on my Roush 402SR/TW came back at 486 HP and 496 Torque at the crank. Less 20% and I've still got more than I need for street use.

Zacctly, you've got plenty of power and can probably blow away 95% of the vehicles you'll encounter on the street!!!!!!!!!!!!!!!!!

I've got about 325 to 350 hp at the crank in my tired 351-W in a 3100 pound 65 Fastback and the good thing is I can put it all to the rear wheels pretty much at will and not blow the tires off it... From 0 to 100 mph it is pretty darn quick and at the drag strip I've beat a lot of cars with 100hp more than I have. Being able to effectively use the hp you have is as important as having the hp in the first place.....600 hp will not make a car any faster if it can't hook it up and put the power to the rear wheels....

David

[Got the Bug]

Originally Posted by patrickt

Lop off 85 horses for the pipes, 20% drive train loss, and you're down at PowerSurge's rear wheel numbers.

Still enough. Where you at?

[patrickt]

Originally Posted by Got the Bug

Still enough. Where you at?

440hp at the crank, with pipes attached. Probably 350hp at the rear wheels.

[patrickt]

I would bet my drive train loss is higher with the ERA rear, which is for the most part a Jag rear. I have been told that the Jag rear eats an extra five percent.

[Got the Bug]

Originally Posted by patrickt

I would bet my drive train loss is higher with the ERA rear, which is for the most part a Jag rear. I have been told that the Jag rear eats an extra five percent.

True, but you get a SWEET ride without giving up cornering performance. My cousin had a Jag rear end in his 32 Ford roadster, and that car was a joy to ride in (and the best handling 32 Ford Roadster out there).

My guess, anything approaching 300 HP at the rear wheels in a Cobra, and you've got your hands full.

[Keithc8]

Well since the subject of dyno testing has come up and my name was mentioned I want to talk a little about them. You have engine dynoes and chassi dynoes and there is a place for both. I would never ship an engine out without putting the engine dyno to make sure it was right and to check for leaks and other problems. Since there is no way to dyno test with the exact exhaust that ever engine has we use a set of headers about the size that most of the engines run. We do not run with side pipes because they are all different and we have built up a nice quanity of dyno results with the headers that we have to compare against. If a customer wants to provide there complete exhaust we can dyno test with them. You have all sorts of variables in the car from the exhaust to the air cleaner to the under hood heat the carb may see.
We normally see about 20 to 25 percent decrease in power in the Cobra's due to the exhaust and other factors listed above. The independent rear suspension robs more than the straight axle rear end as well.
We have to keep our dyno set up very close and this is done with calibrating with actual weights. We have NHRA drag race customers that know exactly what their cars will run and how much power it takes to do that. You will also be interested to know that these cars will put done what the engine dyno says and sometimes more so it might be the car that the engines goes in more than a dyno being off.
In the end they are both tools used to make the engine run better for the customer and we are a lot better of with them than without them becaue I remember those days and the many trips to the track when we did not have them. We can put the same engine with the same power in two different cars and one will out run the other one.
Most engine dynoes correct to a certain standard so that you can compare in the winter and summer. Most Chassi dynoes have a correction factor as well for the same reason and if they do not take your car in when the weather is about 50 degrees and no humidity if you want a big dyno number. You will have to richen up a little in the winter and lean down in the summer if you want best results. If you live at altitude you can run more timing and will need to lean the car down if the engine was built at sea level.
Like I said I know that my engine dyno is correct because my drag race customers know exactly where they are. I have seen as much as 70HP difference in just the sidepipes on these Cobra's. It is where most of your power is robbed. I had one FE engine with 650 engine dyno HP or flywheel HP that made 550 rear wheel HP with our side pipes and tuning and this was thru an independent suspension. We picked this guy up 50 rear wheel HP with side pipe work alone.
Just depends on what you want to do with your car. There is a place for both and I think it is a good ideal to get a new engine chassi dyno tuned after installation. I have seen cars with not enough fuel system and they would have burnt a piston or hurt the engine if they ran it hard with what they had. Just a lot of things in the car that matter as well. It is a complete package that needs to work together.

Good luck, Keith Craft

[Got the Bug]

Keith - Thanks for providing your expertise regarding engine and chassis dyno testing. It's great to have a top notch vendor that stays close to the discussions within CC.

[patrickt]

I can just imagine what a PITA it is dealing with well-heeled, but basically ignorant, Cobra owners who complain that their 600HP engine just dynoed at the local Esso at 350HP. Come to think of it, it would be a PITA dealing with Cobra owners on just about anything that is car-related....

[Ital-cobra]

Hi all

Is it the size of the size pipe that robs the HP?

[Rickd]

My KC 331 stroker, with AFR 165's, dyno'd 436 HP at 6000 rpm at KC's shop on the stand, and on a chassis dyno in Ft. Lauderdale it did 326 rwhp at 6000 rpm. Very much in line. I have side pipes. It is a 'strong' little motor, and a great combo for my FIA. Tremendous power to weight ratio.

[patrickt]

Originally Posted by Rickd

My KC 331 stroker, with AFR 165's, dyno'd 436 HP at 6000 rpm at KC's shop on the stand, and on a chassis dyno in Ft. Lauderdale it did 326 rwhp at 6000 rpm. Very much in line.

That's way better than just being "in line." That equates to only a 50HP loss from the pipes and a mere 15% drive train loss. Of course, that assumes both dynos are correct.

[Slick61]

Yep, with sidepipes & IRS my KCR aluminum 427 stroker put down 612 hp on the engine dyno, & 458 hp at the wheels... sounds about right.

[patrickt]

Originally Posted by Slick61

Yep, with sidepipes & IRS my KCR aluminum 427 stroker put down 612 hp on the engine dyno, & 458 hp at the wheels... sounds about right.

That's pretty serious horsepower. Do you find that the traction issues take away from the drivability?

[trularin]

Pat, are you starting up the BB versus SB thingy...again??

[patrickt]

Originally Posted by trularin

Pat, are you starting up the BB versus SB thingy...again??

What? Me provoke? Never. Seriously though, 460HP at the rear wheels, I just wonder if it kicks and bucks and snots at you when you try and give it a little throttle and then when you do it busts its rear wheels loose and you're unexpectedly looking at the guy behind you.