Johnny - if you make lots of torque down low in the rpm range, you'll have a nice STREET engine. You won't need to downchange to pass other cars, and you won't need heaps of rpm to accelerate from a standing start. You will not be able to keep up with guys that have the same torque peak at a higher rpm. Provided the other guy built his drivetrain to suit (ie: trans and diff gearing to suit the torque curve), he will out accelerate you all the time.

An example of why higher torque peaks help you accelerate :
A Formula 1 car is reputed to have (around) 320lb/ft torque. Many, many Cobra owners here would have more than that, and their motors certainly didn't cost hundreds of millions of dollars in development and research. The difference is that the F1 motors make their (apparently low) peak torque of 14,000rpm!!!!! :eek: :3DSMILE:

Cobra motor: 320lb/ft @4,900 = 298hp
F1 motor : 320lb/ft @ 14,000rpm = 853hp

Johnny:
I stand by my original example! Craig gets it, torque at higher RPM is more valuable than the same torque at lower RPM.

Given enough gearing (torque multiplier) even my 2.0 liter Aries engine will produce big torque numbers at the drive wheels. The problem is I'm only doing 12 MPH.

Bob

Paul,
I've heard from a few people that DTS make a better dyno than Dyno Dynamics, but nobody can tell me what the improvements are..... If it is a superior product, was it simply timing that gave D/Dynamics the market share, or are they a lot cheaper?

I also like how you managed to get a Cobra on the dyno in the PDF catalogue!!! :3DSMILE:

Okay, just playing devil's advocate with Johnny's quote, and Bob's and Craig's responses...If the guy with the same torque at 2000 rpm geared his car appropriately, as Craig suggested the guy making same peak torque at 4000 would do, wouldn't they both accelerate at the same rate (if the quote is right)? And wouldn't the F1 car also accelerate the same as the two other motors if they all had the same optimum gearing and the same torque-to-weight ratio? Hmmm, I'm getting more confused...

And to muddle things up even more, consider this:
Power to weight is usually expressed (backwards, I might add) as weight/horsepower=lbs./HP. So if you want to consider the power to torque ratio, it would be weight /lbs=lb-ft/lb. Okay, so pound-feet divided by pounds equals feet, right? So, my car weighs 2500 lbs, has 500 ft-lbs of torque, so it has a torque to weight ratio of 2500 lb/500lb-ft="5/feet" (or maybe feet/0.2, whichever way you wanna look at it)...how 'bout that?

So you'd say a car with "5 per foot" has a better torque to weight ratio (backwards again) than a car with "6 per foot", right?

Torque as it's related to time is where "horsepower" comes into play. If you were only looking at torque, and not torque over time, then any wheezy old 5.0L motor with optimised gearing should be able to keep up with an F1 motor. This will clearly never happen.

Mazda rotaries are another example of low torque motors aking lots of horsepower. You will never see an RX7 towing a caravan, because they simply don't have enough torque, but I've seen enough 9 and 10 second rotary rockets at my local dragstrip to appreciate what sort of horsepower they can produce. Same deal with them - LOTS and LOTS of rpm..... At 11,000rpm they make big horsepower.

Back to your lb/ lb/ft theory:
2003 V6 Mustang 220lb/ft weight 3150lb
1992 13B RX7 Racecar 220lb/ft weight 3150lb (with ballast ;) )
Same torque to weight ratio. Both cars geared for maximum performance. Mustang peak torque at 2750rpm, Mazda at 9000rpm.
Mustang 16 second 1/4 mile?
Mazda 11 second 1/4 mile....

Same torque to weight, but because the Mazda can make that torque more quickly (higher rpm), it makes more power, and therefore runs a MUCH quicker 1/4 mile.

I wish I had a scanner, but anyway here are my dyno results. I didn't rev engine over 6000rpm.
Run1 maxhp 244@5100 drops to 200@5400 back to 244@5900
Run3 maxhp 254@5100 drops to 213@5400 back to 254@5900
Run6 maxhp 257@5100 drops to 221@5400 back to 256@5900
Air/Fuel ratio has the same drop at 5100rpm. It richens up from 12.5 to 11.8 and back to 12.5 by 5700.
Started all runs at 3000rpm. Run1&2 is as I drive it normally. Run3#4 was with one sidepipe baffle removed from each side. Run5&6 was with baffles removed and small air cleaners removed.

Looks like to me when it goes rich, power drops like a rock. Maybe the rich ratio comes when the secondaries of both Holleys opens? I am sure I should have replaced the MSD chip and ran it up well past 6000, but I was trying to get a feel for this. Unfortunately, the dyno operator was only an operator and knows nothing about tuning. Between runs, I let the water temp cool to 170 so they would all start the same and tried to do everything exactly alike.

David, good info...now ya gotta figure out wha's causing the A/F ratio to go rich...maybe the float level for the secondaries is too high, and there's a momentary rich condition when they open? Let us know what you find. Any Holley Gurus out there?

Craig, on the comparo between the mustang and the RX7...the only points where the comparison would be in line with Johnny's quote would be...the rates of acceleration during the few seconds where the Mustang was running through its peak torque of 2750, and the Mazda through its peak torque of 9000 RPM, and geared appropriately, right? So, if you compare both the Mustang and the Mazda at 2450 RPM, the Mustang will out-pull the Mazda; make the comparison with the Mustang and the Mazda at 9000 RPM, and the Mazda not only out-pulls the Mustang, it will probably have to pull it back to the trailer, hahaha, since the 'stang will be "broke".
Oh, well, theory makes me dizzy. HELP!
David, didn't mean to hijack your thread, are you going back to the dyno?

Ken, I will probably go back when/if I find the problem. Maybe someone else has had similar? BTW, you didn't hijack as all this is related and interesting. Also, torque curve is very flat with 250@3000 to a high peak of 266ft/lbs@5000rpm and drops just like hp curve, then climbs back up.
I'm open to suggestions?
How much loss for a C6 auto trans? I've heard 25% to 49%? This was a Dynojet my car was on.

David, looks like good numbers for the torque curve, just gotta solve that A/F prob...maybe call Holley Tech line?
I would believe 18 to 22% for your total driveline loss, maybe even 25%, but not much higher, do ya think?

And on rereading my last post, on the Mustang and Mazda comparison, if they both had the same torque to weight ratio (handicapped if necessary) and optimum gearing, wouldn't the Mustang at 2750 RPM accelerate at the same rate as the Mazda at 9000 RPM (neglecting wind and rolling resistance, etc.)? They almost HAVE to...but if so, then why does the Mazda beat the %#*^ out of the Mustang in the quarter? Doesn't horsepower win races? There's something here I don't get...and no wise comments, hahaha...

I'll try to post a chart for run1. This was the lowest HP and fuel mixture was the richest at the top end.

This post is certainly getting interesting.
Bob in ct is correct that 4k is by far better. The farther out into the engine's operating rpm range we move the peak toque the more power we will get. Unfortunately we can also move it past a point where the car isn't much use for daily street driving. We have sacrificed the low end torque to a point where we need to indle at high and drive at such high rpms to benifit from the torque our engine is producing. Peak torque at 2k Vs. 4k?

The Mustang is a good example of this fact. The Mustang's peak torque is at 2750. This may help explain why. A standard tremec 3550 bolted to an engine that the operator shifts at 5,000. The standard drop in rpms of the engine until the drive train is fully engaged in the next gear from Tremec is as follows. 1st to 2nd, etc. 2nd.(3027) 3rd(3384) 4th (3731)
5th ( 3400).
Since a car will excellerate the fastest when it is at it's peak in it's torque curve. When shifting the car at 5k at the completion of every shift we are well past the peak torque of our engine. The result is a car that gives the illunsion of being fast off the line, but really falls flat on it's face running 16 sec. in the 1/4 mile.

So just shift at 4,500? Problem is we will probally run out of gear. And also remember 5th is .68, which we should try to aviod in either case when running the 1/4 mile.

David, seems that your a / f ratio really when down hill after 4,300. Are your dual quads vacuum seconderies? If so, could 4300 be where your engine vacuum recovered enough to pull them in and make you go rich? I am not sure what caused your power drop and spike? My 1st guess would be fuel problem. Your hp numbers should get better. A lean engine produces more power than a rich one. The trick is just not too lean.

I have never seen a dual quad setup, and I am assuming that both carbs operate simutaneously vs. in secquence, correct?
I would assume that with an engine producing 250+ horse power, with that flat a torque curve will be excellent in a car as light as a cobra.
As far as the drive train loss being 49% thru a C-6. It has been a long time since I read up on this subject. If memory serves me well, power train loss is basicly caused by friction? If you were encourtering 49% loss thru your C-6 there would be so much heat generated that it would be impossiable to keep it cool.
The 18% numbers i posted earlier appear to be correct.
bud

Craig , The dts dyno is produced and engineered by Allan Murphy the system is new on the market compared to the dynamics dyno soyes it was a timing thing, but it has got 10-15 yrs developement behind it,one of the differering things this system has over ANY other dyno is its ability to measure true drive train loss ,a lot of people claim this ability but no one to date can give a legitimate formula to support thier claims,Allan on the other hand can substaniate his figures with mathematically legitimate calculations, craig believe me there are people trying VERY hard to find out how this sys. does what it does and they've found money can't buy it either.
As for pricing when first released it was substantially cheaper than others which appeared to hinder sales, peoples thinking appeared to be well its cheaper so how can it do and be what it claims to be?So allan put up the price in line with the others and guess what happened!!

I haven't seen the Cobra in the catalog,if it's blue with a white stripe it belonged to John Taylor one of Dts's owners it's a Robnell he also owns the GT40 in the thread in the Gt40 forum i listed a while back.

Craig if you are really interested in the nitty gritty of the system give allan a call i'm sure he would love to talk about all those numbers everybody loves to talk about or if you happen to be in Melbourne at some point give us a call and we'll drop by, DTS is one of the companies owned by John Taylor whom i work for.

Regards Paul

George, I think I agree with a hp loss of 18 to 25%. Seems a of the late model Mustang crowd places the C4 trans at 18%, but the C6 internals weigh a LOT more so the numbers I have heard is 22-25%. Until I built this intaake manifold, I had never had any experience with two Holleys at one time. Luckily fuel distribution is quite even between cylinders according to sparkplug readings. I have done most all tuning up to this point by Seat-of-pants method. Drivability is nothing short of fantastic with only an occasional very small stumble, (Which I have lessened with accel. pump cams and different shooter sizes) when you go from a slow cruise to WOT without downshifting. I don't consider this a problem as with this car I don't often need that rate of acceleration. I have tried many different setups on the carb linkage and the best drivability is with both carbs opening together. Did I mention these are 390 cfm Holleys. Also I now have the "plain" secondary springs (very stiff) in both carbs. I do enjoy a discussion like this. Anyone with some suggestions to try?

Anyone know if there are any difference in a Dynojet Dyno and a Mustang Dyno? Still trying to find my carb problem.

just for info, on the two times i have had my Stroked 351 on a dynojet, at about 70 degrees ambiant, my power curves would lay one on top of the other, even after about 35K miles. Peak HP was 350-360 rwhp, peak torque as 400-410#'s.

Not bad for wheel power.

Good, respectable numbers Hal. Must make a nice package.

There is a difference between dyno jet and Mustang dyno readings. I remember reading an article not too long ago. I believe the dyno jet produces a higher number. Go to www.corral.net and post in 5.0/5.8 windser forum. The Mustang guys will know.

I don't understand why all you guys go get a dyno sheet. Unless you are doing serious engine development, and if you were it would be on a flywheel dyno anyway.

400 ft/lbs at 2500rpm vs. 5000 rpm, the 5000 rpm motor will be allowed twice the gear reduction to achieve the same wheel speed, thus twice the torque at the wheels. right?

C'mon Fixit, it is fun to stand right beside your car while shes going 120 mph and screaming her guts out. Plus, the info is valuable. You can see if your A/F ratio is in the park, play with timing etc. and see the results. No seat of the pants guessing. Plus, you can identify problems such as this case.

I'm just gonna take a guess at this.

It would seem to me that a really high winding motor is going to probably make it's torque and HP over a much wider RPM range. That is, the torque curve will be very flat and peek torque will be available much longer and therefore be much more useful.

I am sitting here looking at my dyno sheet and I see that my torque curve get's really steep at about 3700 rpm, peaks at 437 ftlb at 5100 rpm, then drops off steep again. My peak torque is really only available through a very narrow range of rpm, maybe only about 1000-1500 rpm. I don't know much about motors that turn 10000-14000 rpm but it seems to me they have to have a much wider range of useful rpm and that is one of the things makes them go faster.

Just a thought.

John
spf1421