Mutiny32

And I got 147.4 BHP and 228.0 Ft/Lbs of torque.

Only mod - open element.

Temperature - 101 degrees Fahrenheit

Kept hitting the speed limiter.

Thought I'd just let the TBI bretheren know.

Slade1

That sounds about the same with my pure stock setup, remember, even if you change the gears on the diff, it will not alter the engine's characteristics on the dyno. Only true engine mods affect dyno readings. Unlike the 1/4 mile where everything will affect the run. Take a look att my sig to see what a few lower end cheap mods can do for you...

Mutiny32

They guy doing the dyno said that I had something like 190 at the flywheel. Does that dound right when The cars were rated 170 flywheel HP?

Chuck!

If you est for about 18% drive train loss (A4), you have about 175 HP, which isnt bad at all.

Mutiny32

It says something about a 1.08 SAE correction factor. Any ideas?

Slade1

SAE correction factor is based off reference atmospheric conditions like dry air, low air pressure, and 25 C base temperature. It's a caculation to see what your car would be in those "standard" conditions but in reality... when does the weather like to be standard? You're gonna run even if its 30 C and 101 KPa and with some or a lot of humidity so your car will rarely run at those numbers.

Drivetrain loss correction is a good calculation since it tells you what you had at the engine, before you lost it to the tranny, driveshaft, differential, axles, rims, tires etc... Torque and power are used to move those parts so its natural that the torque at the rear wheels is significantly less than at the flywheel that produces them.

For automatics, the rating is 18% loss on average.

For manual... get this.. its only 15% loss on average.

The 700r4 was getting close to the stick.. I think with today's tech a stick and auto are about the same in efficiency making auto vs stick more a user preference than a performance defining item.

Just divide your numbers by 0.82 and you'll have what your power is a the flywheel. If you add in/lighten up parts along the drivetrain, you simply free up that lost energy.

evil t/a

Not even remotely true. In terms of parasitic losses the In fact the correction factor for autos runs between 18 and 25% depending on who you ask .

Slade1

For thirdgen cars the standard acceptance for dynos for programs is that the 700r4 has a 18% loss rating. This is based off a stock late model 700r4 87-up, stock driveshaft, posi diff, steel discs and aluminum rims. I've done a few dynos now at different places and generally they said an 18% loss is about right. The accepted loss for AWD cars is generally 25% so I can see where you heard that, but it varies for manufacturer to manufacturer since they all build their own respective trannies. The T-5 thirdgens got were rated with 15% loss. Now we know the 700r4 has evolved into the 4l60 and the 4l60e and the 4L80 and each incarnation has gotten stronger and more efficient. The Latest 6-speed for the 2003 corvette is still rated at 15% loss meaning not much has improved in GM's stick development where the auto has had major improvments over the last 15 years. Now this is not to say that the stick hasn't gotten stronger thus allowing more torque and hp to be fed to it, it just means its still losing 15% through the entire drivetrain. From what I heard the 2003 model will be revamped via the powertrain to bleed every bit of performance the LS6 has for a goal of 12% loss only. Now at 18% and 15% numbers, thirdgens are pretty close in efficiency. Its just that a stick has the 3rd gear available to it to help it accelerate better than an auto which compared to a stick does the 1-2-4 gear shuffle. It's that wide gap b/w 2-3 in gearing that hurts the auto performance.

evil t/a

Dude the 4l60 , 700 and 4l60e arent any more or less eficient than any eachother and the 4l80 has nothing whatsoever to do with the 700 it is based on the 400. Like I said before the standard correction factor of an auot is between 18 & 25% there is no one constant number and you cant be sure unless you get both you engine dynoed on a stand before you get the car dynoed.


If you want more proof look at the difference between ls1 autos and six speeds.

evil t/a

Im sure that the neazy tourqu coverter and the fact that a fluid has to tranfer power has nothing to do with a stick being better.

Mutiny32

Would the fact that my torque converter is ****ed up have anything to do with it also? It kept shifting into 4th, and I though the gear ratio was 1:1 in 3rd gear. Maybe I'm wrong.

evil t/a

Yeah a screwed up torque converter will lower horsepower at the wheels by ALOT. And why is it shifting into 4th ? The person running the car should just leave it in 3rd.

Slade1

Better rethink that 25% correction.. hell even 18% seems a bit high in the numbers for a stock engine. Its a little to much on the lossy side since if you correct to 25%. After correction you're saying he really has 196 HP and 304 ft/lb of torque at the engine???

you're living in a dreamworld if you think a LO3 in stock form does 196 HP at the flywheel...

Before you preach that he's having up to 25% consider the results of 25% first... consider 18% as well...

Would you really believe 340 ft/lb and 200 HP at the engine for my lightly modded car???

So I don't think 25% is even close to a realistic drivetrain loss number. Any more loss than 18% is quite unrealistic. The results speak for themselves. Do the calculation first and tell me that you can honestly say that a 305 stock and 10 years old will generate that much power...

You can state 18 to 25% all you want but if the numbers at 18% are quite more realistic for the average 700r4 since at 18% he has 179 HP and 278 ft/lb. Stock says 170 HP and 255ft/lb at the flywheel with a restrictive air filter...

Granted we can't do an engine test at the flywheel and then at the rear wheels, but come on I have in reality a 340ft/lb and GM sold me a 255ft/lb engine??? Check the numbers first and then be sure they add up because 25% loss is a lot of loss and makes the engine a lot more powerful than it is on paper. You make mods sound worth more than it is, you give too much credit to GM and you sound like the spokesman that every mod maker wants boosting their products. (Tornado air element gives you up to 25 HP!!! )

I've tested my car and with TCC lockup I'm getting no slippage in 2nd and 3rd as verified by my identical max rw torque on the curves. So I personally have no added loss due to slippage in 2nd and 3rd, I do however have a large gap on my 1/4 mile run during the 3rd gear portion. From first and 2nd it goes to 4200 RPM and the rpm drops to 3800 on 2nd then pulls to 4200 and shifts to 3rd and rpms drop to 3200 rpm. That is a significant loss due to gearing of the auto, nevermind the TCC loss because with lock up its all but eliminated as proven by a dyno run. With proper gearing, I should go 1-2 4200 down to 3800 up to 4200 2-3 down to 3800 to 4200 then down to 3800 and 3-4 which on a stick ends in a 4th gear 1-1 ratio. That's the gearing disadvantage of the auto to the stick. The car will stay in its powerband for the whole run. The auto will not and fall significantly out of the power band do to the large gearing difference b/w 2nd and 3rd. The fluid transfer issue is not an issue since an auto has TCC lockup with a 700r4 which functions exactly like the stick clutch plate hooking the tranny directly to the engine for a true 1-1 ratio. You don't give auto trannies enough credit for their design. I'd also double check efficiency of a 700r4 early pre 87 vs post 87 as there's a significant efficiency issue there b/w the same tranny of different revisions.... can't say they both work the same because I've driven both trannies and can tell you the pre 87 sucks ***...

evil t/a

Well I thought that was pretty clear. I guess you didnt see the part about "no one constant number" or the word "between". Nice try though.




be·tween Pronunciation Key (b-twn)
prep.

In or through the position or interval separating: between the trees; between 11 o'clock and 12 o'clock.
Intermediate to, as in quantity, amount, or degree: It costs between 15 and 20 dollars.
Usage Problem. Connecting spatially: a railroad between the two cities.
Usage Problem. Associating or uniting in a reciprocal action or relationship: an agreement between workers and management; a certain resemblance between the two stories.
In confidence restricted to: Between you and me, he is not qualified.

By the combined effort or effect of: Between them they succeeded.
In the combined ownership of: They had only a few dollars between them.
As measured against. Often used to express a reciprocal relationship: choose between riding and walking.







When you try to discount the 25% number remember that there are cars with alot more poweer than your that have used the 700 and you numbers dont transfer over to theirs.





0

Slade1

We were never talking about other cars with more power, we're talking about stock or close to stock which was what his car was. Perhaps with cars with 400 hp new factors arise that cause the tcc lockup to fail because the given input of the engine is greater than the stall rating thus causing <1 to 1 for energy transfer to the transmission, but since we were never talking about 400 + engines this isn't the case. The 700r4 was designed with up to 400 hp in mind with 1:1 ratio for the TCC. Move into higher power and you need to significantly improve the 700r4 else the efficiency of the transmission drops substantially.

Case in point his readings.

You have to acknowledge the fact even 18% seems to generate higher engine ratings than was specified from stock. I don't imagine GM had more than a 5% standard deviation for their production coming from their plant else their would be some major quality control issues. And at 18% its just hitting a 5% deviation from the 170 hp stock ratings.

You have to acknowledge that 25% powertrain loss causes a deviation from the standard of almost 15% with a 26+ gain in hp from the standard 170 hp at 196 hp. For a plant that outputted more than 50000 305 engines minimum that year, a 15% deviation would be considered a significant quality control issue and I don't imagine with that many engines being created they goofed and gave some engines more power on a mass production line. One of the key signatures of mass production is nearly identical products with <5% standard deviations from the norm. It has been rumored in the past that GM underrated their engines, various dynos have proven in past that those ratings are actually overrated in most cases.

I took everything you said into consideration did the math and it didn't add up, unlike you who loves to take my ideas and not twist them. I never went after you personally in the debate, I simply implied that 25% doesn't add up. I back up my points with simple to understand calculations and I find it quite sad that you would go so far to imply I didn't read your post. I did read it and did the math and it didn't work. I took a guess that perhaps they improved the efficiency of the autos since they had much to improve with them but recall its been 15 years since the last revision of the 700r4 and that was holding a 3% gap to the stick at the time where today's corvette with stick is still at 15% which was the same 15 years ago. I took a guess, I said I imagine that perhaps they've improved... maybe they did or didn't but I didn't state it as a fact. I also told him that it was generally accepted at 18% for the stock car with auto. It was stating that it was 18% and final, just giving a number to work with since I do acknowledge that its different for each setup and changes like a aluminum driveshaft or disc and drums could alter the loss by as much as 4%.

For the most part the fact remains that it does not compute correctly for anything higher than 18% on a stock setup. The 18% powertrain loss is accepted because its the official GM numbers on the average loss of their powertrains for automatic setups. This is not simply attributed to a tranny, be it stick or auto, its the whole thing. Driveshaft, clutch (tcc, tc or stick clutch), differential, posi and open, axles, brakes (drum/disc /aluminum/iron) and tires. Even suspension can add to loss, but by dyno standards, we ignore the suspension factor in the calculation. The whole thing is a part of parasitic power loss, the tranny difference in auto and stick only cause a normal 3% difference between the 2, once again for stock or close to stock.

If you can prove that the loss is greater than 18%, then I stand corrected but going by "depending on people you ask" is not a solid point to say that the loss is greater than 18%. I base my argument on the fact that I've done 3 dynos to my car personally on 3 occasions and 3 different places One in Cali, one in NJ and one in Canada, I've witnessed dynos of other cars at those shops and those who have dynoed a lot of thirdgen vehicles and the majority are around 15-20% drivetrain loss. A range higher than 18% usually exaggerates the numbers so the general acceptance is 18%.

Play with the numbers, the stock numbers, the dynoed numbers and the calculated numbers and you'll see that 15% stick and 18% auto are the most ideal numbers to work with with stock engines for thirdgens.

Chuck!

The pulls shoulda been made in 3rd gear, the ODs less than 1:1 ratio will affect HP/Torque readings. Swap that converter and go back up there!

Slade1

All dyno runs should be in 3rd gear or at the least a 1:1 ratio. This is more of a consistency issue though. A dyno doesn't car what the gearing is it measures mph per RPM you can have all the fancy gearing you want but the dyno will see right thru it so it doesn't matter really what gear you are in, your engine will still have only x max torque number at x rpm. You can't change that, its a physical constant of your engine. Also your engine will only be able to pull x rpm from that max torque rpm till it can only generate only enough hp to sustain x rpm. For a stick you can dyno in any gear, but the practicality of using first is lost because it pulls through the band much to quickly to get enough samples for meaningful data. The opposite problem arises with latter gears <1:1 ratio/overdrive where it takes too long to get through the powerband and gives too much data to analyze. The torque and hp readins will be the same and if taken to a standard equation under statistical analysis a consisten alpha and beta constant will be found with only 1 maximum torque number and 1 maximum HP number. This is proven simply by what point the max torque is generated at it will always occur at the same rpm no matter the gearing. No matter the gearing the gain of mph per rpm will stay consistent.

For example, a run in 3rd gear. Max torque occurs at 3000 rpm. It pulls till 4500 rpm and gains 45 mph from 3000 rpm to 4500 rpm. The dyno puts the numbers through the equation and curve readings and voila 180 hp and 300 ft/lb.

You do a run in 4th gear, harder on the engine, torque is amplified by the 0.7 gearing. The engine will still peak at 3000 rpm, that is a physical constant for this engine, but supposedly the torque is amplified by the gearing but a new change occurs the engine only pulls till 3700 rpm. The torque is higher at 3000 rpm, but the mph gained per rpm is less now dyno analyzes results tosses the numbers in and once again 180 hp and 300 ft/lb.

No matter what gear it is done in the engine will generate the same numbers and lose the same percentage through the drivetrain parasitic loss. Gearing will change how a car will accelerate but it will not change how the engine functions. Thus a dyno is a good test of statistical numbers. A 1/4 mile run is a good test of the design of a whole car.

The reason why auto dyno's are a bit more tricky is because of kickdown issues with 4th gear for certain automatics. Try to dyno in 4th and it drops to 3rd on certain models. For the early gears TCC lockup doesn't occur or it has no TCC and only when in 3rd its as close to 1:1 as it can be so you don't have the max torque available to you in either case. A TCC will generate a max torque at its flash point, for my car its 2400 flash point where I get 255 ft/lbs at the rear wheels when in lockup. I have lockup available to me via a switch and subsequent dyno runs in 2nd, 3rd and 4th have generated the same consistent max torque at 255 ft/lb @ 2400rpm +- 3ft/lb of torque deviation.

Mutiny32

I'm saying it WAS in third, but it still insisted on downshifting. I've got a post going on the transmission board and they say the problem with my tranny is TC-clutch chatter. I dunno. My shifter is really ****ed up too. That might be a reason.

Slade1

Well that's pretty odd. For all accounts and purposes you should have a decent 700r4, unless its an early 87 model.

Hopefully some adjusting of the TV cable will help, but if your TC is messed, it really shouldn't cause downshifting, just a lack of power. From your results, I say you weren't in third but actually in fourth as technically that is the only gear with it setup as a kickdown valve. The rest 1 2 3 are TV cable dependent on throttle position (TV cable) vs pressure load in order to downshift and a dyno guy will usually get it up to speed before attempting a WOT run.

Your results though speak differently like I said. I have a 4th kickdown issue with my tranny and when tested, it posted identical curves save fore the kickdown part but pulled roughly 148 and 254 respectively when it did kickdown into 3rd.

kdrolt

SAE correction factors for dyno tests are done so that testing can be equitable, day to day, regardless of local weather (temp, barometric pressure, humidity) and season to season on the same dyno.... in addition to allowing comparison across different dynos. It's a means to level the playing field. So a guy in California with dyno data from last Dec can compare with a different guy with dyno data from a test in NJ last week.... assuming the two guys aren't lying and the dyno operators are legit.

Dyno testing can be done in any gear (assuming the trans doesn't shift), and the power and torque measured at the rear wheels are what they are; now if you want the power and torque at the engine flywheel (rather than at the rear wheels), then you need to know the gearing (rear end plus trans) and the effective radius of the driving wheels (usually the rear). Then from simple math, you get closer to the actual engine output.

What's missing from the above is that the frictional loss is different in each gear and the loss is weakly variable in each gear -- i.e. the loss might go as rpm^1.5. In addition, the loss in the torque converter is even worse because it depends on the relative speeds of the input side (engine) and output side (trans input shaft) as well as the effective load (car mass being accelerated on the track, or inertia roller on a chassis dyno) presented up thru the drivetrain to the converter.

The manual trannies are easier to figure, especially if they have converters that lock up AND stay locked up even under maximum acceleraton in 1st gear. There is almost no slippage there, so no loss worth bothering with... other than the gearing itself.

If you are an ME or physics guy, then you probably understand enough of this already. If you aren't, then it's better to stop right here .. unless you want to take Calc I and II, Dynamics, Kinematcs, and at least the Work/Power lectures in Physics.

Most people use correction factors for losses that are all lumped together (i.e. drivetrain loss at 12 to 20+ percent) and held constant no matter what gear the car is tested in, and so it's only an approximation. One way to help get around this is using stock measured rear wheel data and working that backwards into the published factory ratings, in each gear -- then figure out the losses in each gear needed to make them agree, and to do so at the rpms published for peak torque and power.

Example: the LO3 is rated at 170 fwhp @ 4200 rpm and 255 ftlbs at 2400 rpms. Someone measures 147 hp @ 4200 engine rpm at the rear wheels in 3rd gear, but also has peak power data for 1st gear, 2nd gear and 4th gear. That allows the losses factor to be made in each gear because the engine is still making 170 fwhp @ 4200 rpm. You can repeat the exercise for the torque values, again in each of the 3 or 4 gears. The assumptions are that you need a sensible curve shape for losses; I mentioned one previously: rpm^1.5. That one may not fit the data points that well, so what an engineer would do is find out what the best-fit curve would be, for each gear.

The process I just described is a better way to deal with losses than just a straight correcton factor.

People that do this stuff for a living (at GM for example) have more detailed ways of converting the losses, but then they also run dyno tests on the TRANNIES and rear ends (driving them with a big electric motor) to measure the loss vs rpm and load, but I have never seen anyone on ThirdGen either mention this, nor mention the curve fitting approach.

I'll stop now. - Ken