Dyno Tuning: This is why you do it (56k beware)

[Hugh]

Hell, I street tuned my Tec3 from just barely running to 395rwhp in only a matter of 3 hours or so. I had no prior standalone experience, either.

 

What was the name of the shop? If they're that bad, put the name out here.

 

I've never seen a shop do that to someone, but I have seen a shop inflate numbers on cars they have tuned. It's always funny to see someone with a 380hp dyno sheet with a fat power curve get wasted by someone with 360hp in a heavier car repeatedly. It was not a fluke, it was the shop who tuned it. We saw the same shop do that time and time again. (this was in Japan, though... but ain't much different)

[TimZ]

I'd also like to add the letting your car cool off between runs is worthless' date=' if not harmful to your car. Keep it at the nominal temp, most likely when the thermostat opens or right before that for EVERY run. I hate people who want their car to cool off between each run to try and squeeze every hp possible.

.[/quote']

 

Depends on what you mean by "cool off". I always give the car time to stabilize temperatures (both coolant and intake air temps) between runs. The point isn't to get the temps as cold as possible, but to always start the run with the same conditions. Otherwise, you are adding a huge amount of variability into your results, especially on forced induction cars. My first run is with the engine properly warmed up, and I use a 195deg thermostat. Also, I try to start the run with the intake air within ~5 degF of ambient.

[Hugh]

Agreed, cooling off between runs to me means letting the engine return to normal operating temperature. (ie: leave the car running between runs, but give a it a minute to cool down)

[Dragonfly]

What was the name of the shop? If they're that bad' date=' put the name out here.

 

I've never seen a shop do that to someone, but I have seen a shop inflate numbers on cars they have tuned. It's always funny to see someone with a 380hp dyno sheet with a fat power curve get wasted by someone with 360hp in a heavier car repeatedly. It was not a fluke, it was the shop who tuned it. We saw the same shop do that time and time again. (this was in Japan, though... but ain't much different)[/quote']

 

I did some looking at my paper work to see if I still had any info on that shop, what I found was the results of the runs they printed out for me. When I looked at these sheets I noticed that they all said "Mustang Dyno" at the top but not a single one of them has a name, phone number, or address for the company, they only have my information on them. I also looked to see if I still had one of their cards but I could not find one. If they are still in business and I run across them again in the future I will be sure to post it up on Hybridz for everyone.

 

Dragonfly

[Michael]

I’m wondering about the distinction between tuning a modern, fuel-injected, computer-controlled car vs. 1960’s/1970’s-type “technology†(vacuum-secondary carburetor, naturally aspirated, no nitrous, HEI distributor, mechanical fuel pump). Assuming reasonable initial choices for spark plug gap, ignition timing, distributor rotor weights and springs, and fuel jets, what are some of the options available for tuning with the dynamometer? Would a probe with an oxygen sensor be inserted up the exhaust pipe, closing the loop via external diagnostic equipment, where onboard equipment is insufficient? Would a fuel flow-rate gauge be plumbed into the line between the fuel pump and the carb? What about some sort of intake air flow sensor?

[Drax240z]

The problem is that few cars come to us with reasonable starting points! However, I would suggest if dyno tuning a carb'd car you have a wide selection of jets and a means to adjust timing. We simply use the wideband in the tailpipe/header for our setup, which will give you an indication of balance between airflow and fuel flow, combining that information with the torque reading can basically give you the same information as a fuel flow gauge and airflow gauge.

 

We also can log manifold pressure, air temp at the carb, etc. Not terribly useful on an NA car to log the MAP however... it can show other problems. (car not going to WOT, etc.)

[Michael]

I’m heading to the local dyno shop this Friday. They have a Superflow and plan on using a wide-band O2 sensor in the tailpipe. They can also monitor manifold vacuum. There is no provision for measuring exhaust gas temperatures. Tuning parameters will be jetting, carb spacers, switching to a different carb (750 or 850 mech-secondary double-pumper vs. 750 vacuum-secondary), initial timing, total timing and rpm for total timing, valve lash, and possible cam intake centerline (I have a fancy adjustable timing set). This is a for a big block Chevy engine with dual-plane intake, mild mechanical roller cam and mildly-ported aluminum heads.

 

Besides what you’ve posted above, any words of wisdom?

[Phantom]

What a great thread! I had my car do 3 pulls on a dyno about 3 years ago to get a baseline and to have an idea of how well the reflash had been on my ECM for the conversion. It came in at 311 RWHP and 326 torque with the torque curve at 250 by 1,500 rpm and 300 by 2000 which it held until about 5,200 and then back down to 250 by 6,000.

I've been contemplating a dyno tune and now know that I need to:

1) Tell them the car weighs exactly 3,000 lbs with a full tank of gas,

2) Be sure my tires are inflated to 32-35 psi,

3) Take my last 1/4 mile slip with me, and

4) make sure the operator knows in no uncertain terms that he's tuning for maximum area under the torque/HP curves, not for peaks.

 

Thanks so much for all the info!!

[Michael]

Well, I went to the dyno shop on Friday, with high expecations. After the basic questions regarding my engine, the shop owner pointed out that since there are so few miles on the engine (exactly 2.0), it is unready for dynamometer testing; it would need, by his recommendation, a minimum of 100 miles of street break-in time. Otherwise the engine would continue to "seal itself" progressively during the dyno session, thus being a moving target in trying to nail down the best state of tune. His recommendation was that so long as engine temperature and oil pressure are OK, I should drive it aggressively without great concern for failure or damage.

 

This is both reassuring and disappointing; I was hoping to use the dyno session less as a tuning aid than as an expert's blessing that my car is OK. But one should realize, I suppose, that risk and adventurism are part of the price of high performance....

[jmurphz33]

Nice writeup Drax---

haven't even gotten started with the major modifications on my 280, but a buddy of mine works at a very well established dyno-tuning shop... looks like I'll be heading there after I'm running turbo.

I mean, I knew tuning was important--- but some of those hp increase #'s blow my mind! Thanks for the insight.

[Guest CorrPerformance]

Sorry to bring back an old thread, but great write up. As well as the replies from the other members.

 

Alberto

[Tony D]

I missed this first time round, but Drax's point of 1km/sec loading is what we do for the final pull on the Bonneville Car (more like 5km/s). We set it all up for power, then put the hella load on it as we know it will accelerate fine through the first mile, and be almost to top speed, within 5mph likely. But the next two miles on the course, we expect to pick up 1 to 2mph per mile (2-3Km/h in almost 15 seconds, hence the 5 km/s).

 

It really kept us from getting any suprises like a fuel flow lean condition, wiers electrical harmonics, how it performed at the dyno is how it performed (altitude compensated) at the Salt. Very little known tuning trick, good that it was posted. How I missed this post, I'l never know. Worth the bump, IMO!

[DevilZeto]

So i went to a mustang dyno with my slightly modified mustang, its about an hours drive from my home. First run gave out 273 rwhp which i thought wasnt that bad. second pull was 263 with the hood down (my cars carburated and yes it does make a difference if you have a cowl hood) anyway..the thing that got me was that the ownwer of the dyno commented about how a new 2010 ss camaro gave out 292 rwhp...???? That same car he was talking about gave 320 at a dynojet dyno, same mods, same weather, same every thing......

 

So i got a little curious and decided what the hell ill go to the other dyno right away and see the difference for myself. And guess what 301whp on my car!!! same weather, same temperature, same everything!! but not the same horsepower.

Edited September 8, 2009 by Drax240z

[DevilZeto]

Great write up on the dyno tuning...

 

I found a little info as to how each of them operate..

 

The basic reasons for the difference between a DynoJet and Mustang Dyno, is in part on how the power is calculated, and partially due to the amount of "load" the vehicle "sees" during the pull.

 

DynoJets measure horsepower and derive torque from that. Loaded Dyno's have a load sensor, and actually measure the torque being applied to the drums (it's a little 5volt reference load sensor). Horsepower is then derived from that information. Torque is an actual force (like gravity), where as Horsepower by definition is a derivited of torque (work over time).

 

The load sensor data is then sent to the computer where it takes two constants, vehicle weight and Hp@50mph (aerodynamic coefficient used by the EPA) where the computer then calculates the amount of resistance to be applied to the vehicle (PAU force).

 

For an example of why there's a difference due to load, imagine this. It takes less power (however you measure it) to accelerate the mass of a 2500lb roller from 300rpm to 400rpm in five seconds than accelerating the same roller (2500lbs) with 550lbs of resistance via load cell from 300rpm to 400rpm in the same amount of time (5 seconds). That's why if there's a car that made 425rwhp on a Mustang MD-1100SE dyno, it will be faster than a car that made 425rwhp on a DynoJet.

 

As far as the timing example that somebody brought up, I've found that to be true as well. Sometimes the cars are faster with 1 to 2 degrees less timing than they see on the Dyno. Best was without being at the track is to check the plugs. That's why, no matter how good the dyno is, the opperator, or the tuner is, it will really only get you about 95% there. The last 5% is going to be needed to be done at the track.

 

Because of these reasons, it's like trying to compare apples to oranges. As far as the "10%-15%" difference, we've found that to be untrue. In our tests it doesn't seem to be a constant at all. At 390rwhp on mustang dyno, the same car makes about 405rwhp on a local DynoJet. At 422rwhp on mustang dyno, the same car on the same DynoJet made 458rwhp. I've witnessed cars seeing close to a 80rwhp difference between a Mustang Dyno and a DynoJet at 600rwhp (Mustang MD-1750SE), although I cannot verifiy that with our dyno. More recently, I've found that a 2002 Vortec S/C Z06 that made 550rwhp on our Mustang Dyno, made 645rwhp on a DynoJet over the summer.

T

the difference is closer to 6-7%, but as you make more power, the difference increases as well. You must remember, Dyno's regardless of the type are tuning tools, and are in no means ment to tell people how fast their car is. Now which one is more "real world" is a totally different question. I like to explain it like this..... If you drive your car in a situation in which you have no mass and you're in a vacuum, so basically if you do intergalatic racing in space, use a DynoJet. If your car sees gravity, and has an aerodynamic coeffecient, and you race on a planet called Earth, then use a Mustang Dyno.

Edited September 8, 2009 by Drax240z

[burninator]

Hearing people slam Dynojet Dynos get's old. I think there is a lot of misinformation out there. People have a reasonable theory of how they think power or torque is calculated, but its normally just something they heard from a guy who heard it from a Mustang sales man. A lot of the things people like to pick on Dynojets for (like not having load control to tune certain parts of the map with) are about dynos and software that is pretty old by now. There have been Dynojets available with load control for years now and they work well.

 

DynoJets measure horsepower and derive torque from that. Loaded Dyno's have a load sensor, and actually measure the torque being applied to the drums (it's a little 5volt reference load sensor). Horsepower is then derived from that information. Torque is an actual force (like gravity), where as Horsepower by definition is a derivited of torque (work over time).

Statements like that are fairly inaccurate, and only serve to discredit Dynojet unfairly. For starters, Dynojets (in inertia only mode) only measure acceleration. The drums have a known mass that can never change. As we all should know Force = Mass * Acceleration. If we know the mass and we know the acceleration we know the force, it's as real as it gets. From force, torque and power are calculated. Saying that because torque is actually measured with a loaded dyno makes them better is just false, and makes it sound like Dynojet doesn't measure anything and just pulls the numbers out of the air.

 

Here, I found this link to a paper. Yeah, it's written by a guy from Dynojet (the VP of Dyno Sales), but he's not just some sales guy, he actually knows how to tune cars. I think it offers valuable info (some of which I repeated here). http://www.fmjmotorsports.com/link/Truth_Lies_Dyno%20Runs_Final.pdf

 

And for people who still believe that Dynojets always make more power than any other brand or whatever check this article out: http://www.modified.com/tech/modp-0909-awd-dyno-comparison/dynojet.html They tested four different brands of dynos and the Dynojets that were in the test were neither the highest or lowest.

 

Sometimes cars are the things that aren't repeatable or consistent. There are hundreds of factors that can make a car show a different power number from day to day, even on the same dyno. Modern cars with fancy computer controlled maps are notoriously bad about this. And just saying a Z06 didn't produce the same numbers on several different days means nothing to anybody regardless of the dyno they were on. And yes, I'm sure there are even cases of 400 hp cars that are faster than 425 hp cars on that were both measured on the same dyno, there is more to life than peak numbers. Dynos are a tuning tool only. Nobody should be comparing different cars on different dynos and bragging about which peak numbers are best.

 

If you need work done, by all means pick a dyno shop that has the tools you need to do the job you need done, but don't rule out all Dynojet dynos because somebody on the internet said they sucked. And I don't expect anybody to pick them because I said they were good. If you think you need load to hold the car in an area of the map to tune, then find a shop with that. Also, check out what they have for air circulation. You need a lot of cool fresh air and a good way to get rid of the exhaust. And most importantly you need a competent honest operator.

 

End Rant.

[burninator]

For an example of why there's a difference due to load, imagine this. It takes less power (however you measure it) to accelerate the mass of a 2500lb roller from 300rpm to 400rpm in five seconds than accelerating the same roller (2500lbs) with 550lbs of resistance via load cell from 300rpm to 400rpm in the same amount of time (5 seconds). That's why if there's a car that made 425rwhp on a Mustang MD-1100SE dyno, it will be faster than a car that made 425rwhp on a DynoJet.

 

After reading it again, that doesn't even make any sense. I don't know where you got this from, but in the situation described the "absorbed load" from the extra 550lbs of resistance would have to be added into the total power. This is definitely true of how it works with Dynojet dynos, and I'm sure is also true with Mustang dynos. To prove this you can take a Dynojet with a drum of known mass and do a run, then do another run with the load control set to a certain %braking. If you did this the runs would show the same power and torque, but the second run (with the added load) would have taken longer.

 

This example seems to be trying to say that both dynos would have given the same power which is simply not true. If the mass of the drums was the same and the time taken was the same, then the one with the extra load would show more power. This is another example of someone who doesn't know how dynos work trying to slam a brand with false information.

Edited September 18, 2009 by burninator
added more information

[DeleriousZ]

Dynojets suck!

 

 

 

 

 

 

 

 

[langfordchuck]

very informative thread, esp. since I live in victoria, bc. I pm'd Dragx240z, does anyone know if he is still in business in victoria? And i echo an earlier question above: is dyno-tuning a worthwhile investment if you are running a relatively stock n/a 260?

[bradyzq]

Disclaimer: I am a dyno tuner!

 

I would say that it is worth it to get your car onto a dyno along with a good tuner.

 

Here's why: It's not as if when you put your car on a dyno that it will automatically run better when it rolls off, or even that there is much you can do to a stock 260Z on the dyno, BUT, the dyno is IMO the best place to see how your car is currently running. In other words, it'll highlight any problems the car might have. The dyno will also allow you to experiment with mixture knobs and timing to determine what your car likes best.

 

So I definitely say, "Go!" Worst case, if your car turns out to be running perfectly before you even get on the dyno, you'll leave with some dyno graphs of your car and a good baseline for future comparison. Best case, problems will be identified and hopefully corrected, and your car will run much better than it did before.

[Sketch_hs]

From personal experience:

 

Dynapaks tend to be the most consistent dyno. Best for hardcore tuning (50+ runs)

 

* They are a bitch to set up and that will cost you, unless you can do it yourself and have friends with a dynapak lol (especially on 4wd cars)

 

* They tend to read higher than most other dynos (dynos aren't great for measuring power, they are for tuning!)

 

* I'd rather use a roller dyno most of the time just cause it's easier!