Dyno...Whats up????? Rwhp???
 

Lately I see alot of people talking about "having your car dynoed" and "how much RWHP do you think I have"? Whats up with this?
I know they are great for tuning and if you are using them for a reference point only! I believe people are starting to get way cought up in how much power there cars make at the rear tires!
For an example, couple of years ago when my local speed shops got there dynos, it was like this god sent device for all of us racers. When in fact all it caused was frustation!
My friend and I had street cars that made some power. His Trans-Am made 318 horsepower at the rear wheels on motor. Then it spiked up to about 423 horsepower on the spray. My car was completely different. It only made at best on the dyno 294 horsepower, 384 with the spray. At that time I had to here all the **--ing time that how Trans-Am cars rocked and Fords were slow!
So one weekend we went to the track (thinking I was going to get smoked, because its the first time out with our combo's. His best pass was a 12.46@108 mph. My car ran anywhere from 12.21-12.15@109.5, What gives? We both have torque converters that stall at about 3400 rpm, same gears and tires, so you tell me. His car weighed in at 3550w/ driver and my weighed in at 3250 w/driver.
I believe it was all in the chassis work and having the right parts! Owe yea, by the way I went out the following week-end and blow off a 11.98 at 110 after retuning the car. (with no dyno) On the spray it went 10.86@122mph.
Now all I am saying is that people just maybe need to lay off on how much power there car makes at the rear wheels and just run there cars!!! 500 horsepower at the rear wheels don't do sh-t if you can't hook up!
I also understand that manual transmission will show more horsepower at the rear wheels for the same ET'S, because of less drive train loss. But it also seems that people don't know that race cars with loose torque converters will show alot less horsepower then somebody with a tight torque converter.

Let me know what you guys think. Are we starting to get carried away with this or not?
Thanks

Most guys on this site quote their best qtr. mile ET and mph - not dyno numbers.

See my sig.

E

I just finished my motor last night. Will I go to the dyno? Yeah I sure will to see how my combo works together as well as figure out what my optimum shift points should be etc...

Re: Dyno...Whats up????? Rwhp???
 

I think alot of it has to do with that 300 lbs more weight he has on you.

I want to get my car dyno'd for 2 reasons.
1 - To get the best tune and shift points I can.
2 - To know for a fact, on paper, that all the blood, sweat, and tears in my car did some good.

Ya with only a 40 horsepower and 300 pound difference those times seem right. Weight is the enemy even in cars with alot of power. And its also hard to beleave you went in the 10s with under 400 horsepower and your weight. :confused:

Well, I've never made it to a track, so my dyno numbers are what I use. It was a good tuning tool for me and gives me some idea of what my car might be capable of running, assuming I could drive the thing:) .

Not all of us can get to the tracks, so I guess the dyno is the next best thing.

Re: Re: Dyno...Whats up????? Rwhp???
 

Exactly, and to know what mods did what (if you dyno before/after mods)

Ok cool, Everybody who replied thanks for your time and input, but still, everybody so far are using the dyno for intelligent resons... (For reference points). Maybe I just didin't get my point across right? All I am saying is that it seems that people are exaggerating(or at least hard to believe) Rwhp #'s. I saw somebody quote somebody's combo with such a lack of info, he didn't even know what size cam or cylinder heads he was using!!!
Its just seems its starting to become a pissing contest among people, not here but just in general. Its like the old days "I have 3/4 inch cam so my car must go faster then yours type of thing. I just want to know if its just me or are other people noticing it too?
Before long, according to some ignorant, mis'informed people you will need to make 600 horsepower at the rear wheels to run in the 13's in 3000 pound car!!!!
It's a fact that manual transmission cars will show more horsepower at the rear wheels then an automatic trans car. It's also a fact that automatic cars with loose conveters (4,000 stall+) will show a significantly less horsepower then normal.
My last combo that yelded under 400 horsepower at the rear wheels had a 4200+ stall converter. And if after all of that, you cant get a car to run in the 10's then maybe you need some lessons on driving!! I could you teach for a price.
:p

I don't notice it a whole lot, but it seems like it is just another form of "bench racing". Some can do it intelligently, and others don't know what they are talking about.

Also, explain to me why a car with a high stall converter would show less power? Once that thing is spun up, it shouldn't matter. I could see where it may effect an average hp reading, but peak hp shouldn't change, right:confused: ?

Not to sound stupid but the article to back up my statement is misplaced. When I find it I can send you the info and magizine article. It was in Muscle Mustangs and Fast Fords, under thunder mail. Don't recall which issue, but basically, yes the loose converter causes slippage which will not show the same amount of power as if it was a 5-speed. It is also true that a automatic transmission eats more power then a 5-speed, but we are talking more then that. It seems that when you put a loose converter in a car,you loss pwr according to the dyno, but you didin't, and it proves it when you go to the track. That artice in MM&FF shows a race car that made 420 RWHP but yet blew off a low 10 sec pass. The article then tryed to find out what happen, because the car should have gone alot slower. According to the article they were missing approx. 70-80 horsepower, but ET did not show any loss what so ever. They concluded that it was the converter.
Like I mentioned before, the dyno is an awsome tool for reference use only. Its not to compare with other cars,... well to a point I guess.
If itsany help my first combo was a GT-40 package from Anderson Motorsports. GT-40 heads, Gt-40intake. E-303, Mac 1 5/8 full length hearders, 2 1/2 off-road h-pipe, Flow-masters, 4.10 gears, and a Tremic Transmission 3550. The car made 268 rwhp at the same dyno shop. Car went as follows on average.
60 foot 1.71-----1.76
1/8 mile 8.0's-----88
1/4 mile 12.50's---107
Now I dont know if maybe the shop I went to was calibrated differntly or what, but all the race cars that had race prepped transmissions that made anywhere close to 500 rwhp were all solid 9 sec cars that weighed close to 3000 pounds.
:confused:

You need a load bearing chassis dyno to accurately read horsepwer and torque on a car with a stall convertor. Like you mentioned, with an inertia dyno they will show low horsepower numbers, but they will also show high torque numbers. If the inertia dyno is operated correctly they can still be used as a tuning tool, but comparing horsepower numbers is silly.

On a manual transmission car, its a different story. The Dynojet 248 I have access to is very repeatable. I have been on 3 different 248's and the corrected numbers are usually within 5-7 horsepower of each other. To me, thats close enough for me to quote what my car makes and feel confident that I'm not mis-representing.

Andy

Thanks, when I am ready to get my car on a dyno I will ask to see what type of dyno they have. I will try to find a load bearing chassis dyno like you listed to put my car on. I was completly unaware of such thing. I just assume that a chassis dyno was a chassis dyno. When I find one I will post them (good or bad.)
Thanks

Interesting stuff. What is a load-bearing dyno or what is an example of one? I had mine done on a dynojet, althought I don't know which model.

if it's used right then it's great but i have to agree that it seems like it's getting used as another way to bench race.

A load bearing dyno (also called power absorbing) places a load on the rollers. The Mustang Eddy current dyno is able to apply a load to the drums by using its eddy current absorption feature. Land & Sea makes a chassis dyno with a water absorption brake. I've never operated either of these and I dont understand exactly how they work.

The Dynojet 248 is able to simulate a load by applying the brakes to the drums. (friction method) Its not very accurate in measuring horsepower that way, but in most cases you can get stall convertor cars loaded enough so they dont blow through the rpm band.

Andy

I agree 100%, dyno's are tuning devices and nothing more. When I went to the chassis dyno, I was a little upset. I could only get 451rwhp, and 410lbs. ft.(NA). Through conversions, it said I was only making like 580 flywheel hp. Well car weighs 3150w/driver, and has run a 6.49/10.10(NA). So I just go to my times, and feel much better.

420Nitro: Have you gotten anytimes out of yours yet?

Later, Greg(XSR)

I agree that dynos are just a good tuning tool, but track times can be misleading as well. If some guy runs at sea level busts out a 10 second pass, the same car would be considerably slower at 5000 ft elevation. So it all depends on certain conditions. It basically breaks down to the fact that dyno numbers and track numbers are simply that. NUMBERS. Engine performance changes all the time. I don't understand why everyone feels like that have to post their track times. As long as you enjoy driving your car, who cares what it ran at the track or pulled on the dyno. Of course, I'm gonna post my track times as soon as I get this piece of **** running. :-) but you get my point.

No I have yet to take my car to a dyno. I have been dailing my car in by the means of reading my EGT's. The only problem I am facing is traction. I can't seem to lay into the car till I am at least at the top of second gear, which is causing some problems with the local law enforcement in my area. And let me tell you that I am running the same set up as before with 28x10.5 slicks. The last combo I used to street race with the nitrous on right out of the gates and hook!!!! Now I got problems! I am probably at the 400 rear wheel horsepower mark :rolleyes: But no really It also seems that I will have no choice but to put it on a dyno and use the numbers as just a reference point only. Then I can go to the racetrack and race these 800 RWHP cars and say "what happened to ya!!:p
But seriously I can tell you my whole combo if you like and you tell me what you think.
Later and thanks

I forgot, I also have yet to take my car to the track as well. Working out all the litlle bugs, just about got them all fixed, plus the local tracks are all closed for the winter. Hopefully after Christmas my little girls won't take all my money and I will have something left over so I can get a new N.O.S plate, for spring. I am also considering dumping my Precision Industries torque converter for a new converter from Lenny at TCT.
Later

From an engineering/phsyics standpoint, I don't see why the Dynojet would be any less accurate. Obviously though, they are. Different dyno's give different numbers even though they are really simple machines. You would think that no matter the set up, you would be able to get repeatable, accurate numbrs on any dyno.

May i ask what size injector you ran on that combo?
with that 60' thats about where my car should be.
with a t-5, your dyno would have been a little better, i think the tremecs eat a little hp, probaly not much, what was the weight?
my car is about 3120 with me in it, im hoping to see 280rwhp, but even if it's under that, i know the stock 300rwhp ls1's have all kinds of gap to fill at the track as soon as i leave line :D the SS's are tough to hold off on the topend though.

like mentioned above, i just want to dyno for shift points, and see what the wideband says, so i can adjust fuel pressure, i wont brag on anything, and say im faster than so in so, because i dyno xx, it comes down to who can ride that sucker to the 1320 ft the quickest imo.
good day

At that time I was running 24 pound injectors with 36 pounds of fuel pressure at idle with the vacuum port disconnected. TPS sensor was dail in at .998 volt. Car indle at 850 rpms. 17 degrees base timing. (spout connector disconnected.) Car also had 4.10 gears.

Sorry, I forgot the car weighed at approx. 3,400 pounds at that time.

i saw a new type of dyno that bolted to the rear studs ( you removed the rear wheels) and its supose to be more accurate.

And as someone said elevation can play havioc with hp numbers and if your car doesnt hook it doesnt matter how much rwhp you have but dyno's are great tuning tools and can help find problems on a new engine before you blow it up,

I always tell people no matter how much hp you have it's the first guy through the traps that wins.

About 4-5 percent more. :D With a T-5 thats broken in we will see about 12-13%, whereas a Tremec is about 17-18.

Andy

Agggghhhhh!!! I knew it! I should've kept my T5 :D

E

Hey andy I checked into this and found that I was using and still using a dyno which is called (mustang dynamometer). Which is quite different from a Dynojet 248! This Mustang dyno can simulate elapsed time tests (1/4 mile pass)!:D You can use the transbrake and launch the car off of 6000 rpms and simulate a full pass!!! This dyno is not an inertia dyno. You can make a pass and hold the car at a predetermined rpm and check your wide band o2 and make the adjustment right there while under load!!! The only thing is that it gives a much lower h.p #.The more h.p you make, the more it will vary from a dyno jet (it"s on a percentage).
Example: Fact
My friends down south dynoed a car with 650 rear wheel horse power and could barely keep it tied down. (auto-with a loose converter) Went to the track and gave the car 5psi more boost and blew off a low 8 second pass.! Now on a dyno-jet it would of probably made some where in the 900-1000 hp+ but it would of taken a lot longer to dail in.

On motor my car went 12.0 @ 112 with 310 rwhp.
With 8 psi it went 10.9 @ 128 with 430 rwhp.

The car weighed about 3200 with me in it. These are Dynojet numbers with a 3500 stall convertered C4. A stick might have shown 450 RWHP.

It goes to show you don'y have to make big numbers to run decently fast. A nitrous car might run even faster with an equal peak hp number considering nitrous makes a TON of torque down low compared to a blower.