New dyno numbers (down with Dynapack, long live Dynojet :D )

[yo2001]

Prolly the dyno operator messed up the rpm reading. Prolly set for 4 cyc. or something. Make since to me, it'll mess up the graph and peak HP since HP caculated with load (torque) vs rpm on dynopack.

 

Personally I like Dynopack better, it's more close to accurate HP since it measures torque at the hubs. Plus it can pull consistant pulls with set rpm by loading the hubs.

[Guest bastaad525]

Yo - Yeah I was figuring the RPM being off would explain everything. I actually called the guy at that shop yesterday and was asking him about why the numbers might have been off... he couldnt' see how the RPM would have been off, but I did mention to him that the rpm reading on his computer was a couple hundred rpm higher than what my tach was showing... he said that shouldn't have made a difference, that the computer 'knows' what the rpm is. But the dynapack doesn't measure rpm by reading spark like a dynojet does.. it just infers rpm from gearing and wheel speed.

 

I have heard from a few guys that the dynapack is better for tuning, for the reasons you said plus others. But I keep mentioning that the pulls on the dynapack were very inconsistent. Maybe that was operator error too... When I talked to the guy and asked about this he said he typicaly sees a lot of power lost over several runs, that it was do to the engine getting hotter. Um... huh??? I've NEVER seen that when doing several runs on any other dyno. And still... does that account for 40ftlbs of torque lost from the first to the 6th run? I can say now with some certainty that it was NOT the minor changes I was making to the a/f ratio that lost all that power, and the engine running hotter doesn't make sense to me either... not for that much power loss.

 

Well it seems the dynapack has a great rep among the people who've used it, it's said that it's so much better for accurate tuning. Maybe I just had an unlucky experience.

[Gollum]

when i mentioned people treating dyno numbers as the bible i'm talking about those people that bench race with thier dyno numbers. The people that say "I have a 300 hp car" when it's like right at 301. I'd consider that a 290HP car personally. I hope i didn't seem like i was pointing fingers at all, i've never met anyone like that here.

 

Oh, and yes if you do back to back pull you'll get less hp the 2nd time through. It's a good idea to let your call cool for a good half hour or more between pulls. Reason being is intake temp. Right after a hard run like that heat is all over the engine, making the overal air in the next run hotter. If you let the engine cool a bit you'll have a lower intake temp and more hp as a result. But it shouldn't be 40hp.

[yo2001]

On dynopack, you get the rpm by gear ratio and something else, (I can't remeber right now) But before the initial dyno, they have to set the rpm with the computer. The dynopack # is usually lower than dyojet though. I wouldn't worry about it too much as long as A/F was good.

[Guest bastaad525]

 

Oh' date=' and yes if you do back to back pull you'll get less hp the 2nd time through. It's a good idea to let your call cool for a good half hour or more between pulls. Reason being is intake temp. Right after a hard run like that heat is all over the engine, making the overal air in the next run hotter. If you let the engine cool a bit you'll have a lower intake temp and more hp as a result. But it shouldn't be 40hp.[/quote']

 

Actually, on the Dynojet I GAINED a couple hp on each subsequent run, but lost a couple ft lbs as well. I think the changes were more to do with me messing with the a/f ratio. And every dyno I've ever run on, the operators always let the car cool for like 10 mins before the next run. So there's no way I should have lost so much power on that dynapack.

 

Yo - that was the whole reason I went to the dynapack was to tune the FMU... but still felt gyped to come away with power levels barely above what I was getting before installing the I/C. But there's me comparing apples to oranges again Personally I don't see why tuning on the dynapack is so advantageous either way.

[Moridin]

Actually' date=' on the Dynojet I GAINED a couple hp on each subsequent run, but lost a couple ft lbs as well. I think the changes were more to do with me messing with the a/f ratio. And every dyno I've ever run on, the operators always let the car cool for like 10 mins before the next run. So there's no way I should have lost so much power on that dynapack.

 

Yo - that was the whole reason I went to the dynapack was to tune the FMU... but still felt gyped to come away with power levels barely above what I was getting before installing the I/C. But there's me comparing apples to oranges again Personally I don't see why tuning on the dynapack is so advantageous either way.[/quote']

 

Sorry to dig this stuff back up again, but the difference between the dynojet and the dynapack is (as you know) in the way they messure horsepower. You will get better results vs. proper street weight loading on the dynapack. The same holds true on Superflow and Mustang dynos. The Dynojet is inertial only and can only do a sweep run at the set weight. This is not the way to tune a car and it will show higher numbers than the other dynos. Best way to check is to check parts before and after on the same dyno on the same day. Understandably, that is not always feesible, but staying on the same dyno is very important.

 

To give you an idea, I've heard that Dynojets will show 10% HP at the wheels when compared to a Mustang dyno.

[Guest bastaad525]

Well here is one interesting thing to consider as well.

 

Whenever anyone talks about dyno numbers, you very commonly hear that the driveline losses are about 15%, when calculating from the at-the-wheels numbers to the flywheel numbers.

 

 

This very number seems to be based on using a dynojet dyno. I've seen, heard of, or read of many cars, in stock trim, being tested on a dynojet dyno, and almost always posting exactly or very very close to 15% less than they are rated for from the factory. There have been a few exceptions, of course (Dodge SRT-4, underrated from the factory, actually put MORE power to the wheels than it was rated for, Mazda RX-8, had closer to 25% less to the wheels than it was rated for when it first debuted... Mazda has since changed the rating), but for the most part, the rule seems true. So I still consider the dynojet a good way to measure 'true' horsepower, that is to say, a way to get a very good idea what the actual horsepower at the flywheel is. Yes, Mustang dyno's and Dynapacks will show less RWHP, usually, from a Dynojet (actually the Dynapack and Dynojet tend to be very similiar), but, a lot of people don't seem to take this into account when they throw that "- 15% of the flywheel hp" equation.

 

So I think the dynojet is a good base from which to calculate your true, flywheel hp. Whether it is as good to tune on as the other dyno's or not, I don't really know enough to say, but they are damn popular for a tool that doesn't work so good

[Mikelly]

Well I'm stuck locally with a Dynojet. That said, If you have the option of tuning on a dynopack unit or a DynoJet unit, Don't spend any time on the dynojet. If you want big numbers that won't match your street performance, Go ahead and do a few dynojet runs... And like Scottie and John C. said, NEVER compare different dyno sessions or dyno equipments...

 

Mike

[Scottie-GNZ]

... And like Scottie and John C. said, NEVER compare different dyno sessions or dyno equipments...

I am amazed that discussions comparing dynos and dyno numbers can go on for 3 pages.

[Guest bastaad525]

I've done well tuning on a dynojet I always get VERY consistent results from run to run and session to session, with power only changing when I've made changes to the setup, and the power usually changes somewhat predictably (you could look at the changes made to the setup, take a guess as to how much power was gained, and usually come away with very close to that amount of gain on the dyno). This has also applied when tuning on dynojets at different places...

 

 

And how do you say that the dynojet numbers wont match your street performance? Seems people do seem to get performance at the track or whatever very consistent with what their dynojet pulls indicated. I know my last setup, the N/A motor, performed just about dead on at the track, with what the dynojet numbers combined with the weight of the car said it would run.

[Tony D]

I'd agree with Mike, I wouldn't waste time tuning on a Dynojet if a Mustang was available (like in Oceanside...muahahaha)

The main advantage is they can hold a load point EXACTLY and you can screw with fuel and timing while holding there and get realtime readouts of changes good or bad when movingthings around. It allows you to peak optimize each load point in your fuel/load/spark map which will give better interpolation and FAR better drivability quicker.

Where it really is nice is the partial throttle tuning, where your choices are to either finda flat road, or gradual hill, and ride the brakes and annoying traffic to hold partial load points to tune them.

 

I don't know about you, but my wife does not respond well to being awakened at 0200 to go make fifteen or so passes up the VanBuren hill while I yell at her to hold the brakes at a load point. This makes us both stressed and upset.

 

On the other hand, she only complains a bit when she gets the CC bill for the dyno time...until I remind her of the "alternative solution"

 

LOL

[Guest bastaad525]

yeah well... I must be dealing with the wrong people then because I have been to a mustang dyno and a dynapack dyno, and none of the operators ever suggested or mentioned that I could use them to tune in this way. They just do the same three pulls, allowing you any adjustments you want to make in between, same as every dynojet place I've been.

[Drax240z]

The load control is an option for the Dynojet and one that most places don't spring for. It's a huge tuning benefit, but most places can make more by simply providing people with a dyno sheet and some basic tuning, as that is what the majority of customers want.

[kj280z]

Please. A big mistake that people make too often is to focus on dyno numbers. I'm amazed that this thread has gone on for so long.

 

The only real purpose a dyno serves is to help you to determine if changes you've made had a positive or negative effect as compared to a previous pull on the same dyno.

 

You could put your car on a dynojet and make 400hp on it, then go down the street to another dyno of the same brand and make a completely different number.

 

Dyno's are ONLY for benchmark and comparison purposes!

 

If you're doing it for bragging rights it serves no purpose.

 

One comment on the Mustang Dyno... there are some big advantages to using a Mustang dyno for tuning under load for drivability. BUT, if you're going to a Mustang dyno for bragging rights trying to make a big number you're going to be disappointed.

 

Whenever I see dyno numbers I always take them with a grain of salt... As should everyone here...

 

A more beneficial analysis of a dyno chart is to evaluate the power curve and analyze the characteristics of how and where the motor makes power.

 

This type of analysis allows you to determine if the power band will meet your goals (different applications require different characteristics). For instance if you're building a high compression race motor designed to make power in the upper rpms, learning where your motor makes its best power in this example would allow you to optimize your complete setup (gear ratio's ect) and show where to make changes to get the best result.

 

Ken

[Guest bastaad525]

Again... I'm not really debating the numbers. I know as well as anyone that different dynos will give different results.

 

Myself, I'm debating that a) for everyone raving about the Dynopack for consistency, I got VERY unconsistent results when I was tuning on one, with over 40 ft lbs variation of torque in the course of 6 runs, with only very minor tuning changes. On the dynojet, those same tuning changes only yielded 2-3 hp and ftlbs differences, as was predicted SHOULD happen by guys here who I do believe know their stuff... no one would understand WHY I was seeing so much power loss on the Dynapack.

 

I'm also debating that, while I know it's useless to compare dynojet numbers with numbers from other dynos, I am simply saying that I personally, and many other people as well, have seen a consistency with the Dynojet numbers when testing stock cars... always seeing just about a 15% lower number to the wheels then the factory rating.

 

And since when did it become so wrong to brag about dyno numbers? 300ft lbs of torque on ANY dyno is pretty impressive to me... and is quite an achievement from such a budget project, and also when compared to when I built up my N/A motor... so why shouldn't I be allowed to brag? I'm not going around saying "my car has more torque/hp than yours"... nothing like that, just proud to have accomplished what I have with this car.

[kj280z]

Again... I'm not really debating the numbers. I know as well as anyone that different dynos will give different results.

 

I'm also debating that, while I know it's useless to compare dynojet numbers with numbers from other dynos

 

And since when did it become so wrong to brag about dyno numbers? 300ft lbs of torque on ANY dyno is pretty impressive to me... and is quite an achievement from such a budget project, so why shouldn't I be allowed to brag? I'm not going around saying "my car has more torque/hp than yours"... nothing like that, just proud to have accomplished what I have with this car.

 

I normally wouldn't comment any further, but you're talking out both sides of your mouth so I had to...

 

Soooo... Let me ask you ...if you go to another Dynojet and your car only shows 255 ft-pounds of torque having made no changes what-so-ever, would that also qualify you to "brag"? I guess I should start going to EVERY dyno around and find out which one makes the highest numbers since that seems to be the essence of what you're saying!

 

If you want to "prove" anything, do it on the track and take all the numbers you've made on a dyno with a grain of salt and use them for what they are... benchmarks for comparision and analysis.

[Scottie-GNZ]

...the Dynojet numbers when testing stock cars... always seeing just about a 15% lower number to the wheels then the factory rating.

You are still missing the point. It does not matter what the dyno number is. The only thing that matters is what the dyno number is on the next pull compared to the previous to see if you are making progress. IOW, the only comparison you should be making is the net results of one pull vs another on the same dyno in the same session.

[Drax240z]

You are still missing the point. It does not matter what the dyno number is. The only thing that matters is what the dyno number is on the next pull compared to the previous to see if you are making progress. IOW, the only comparison you should be making is the net results of one pull vs another on the same dyno in the same session.

 

Absolutely agree 100% with that statement, and can't emphasize that enough! The only way to make intelligent improvements to ANYTHING is one change at a time, so you can document and scrutinize the results. As soon as you start playing with different dynos, you are changing MANY factors at once. (Calibration, ambient temp, humidity, possibly dyno manufacturer, airflow, exhaust extraction, etc.) Any of these can have significant effects on your readings. Stick with 1 dyno facility. Try to do mods between pulls on the same day, as close together as you can get timewise. Only change 1 thing between dyno runs before retesting.

[Guest bastaad525]

that's all well and good... for guys with lots of money to spend hours of dyno time in one shot. Unfortunately, I'm not one of them, so for me it's... test... tune whatever I can a bit between pulls (of which you usually are only allowed three). Come back later when some new part has been added and tune for that... rinse... repeat.

 

And secondly... don't think I wouldn't prefer to stick to one dyno if I could. I don't go around to all these different dynos in hopes of finding one that will read higher than the others so that I have a higher number to brag about.

 

I've mentioned this several times before on these boards... Of the five dyno places I've been to (3 dynojet, one mustang and one dynapack), three of them went out of business or relocated out of my range by the time I went back to retest. Of the two left, one was the dynapack, which I only went to once, and wasn't really satisfied with the whole experience... it took them like two hours to even get my car on the damn thing, and the results from pull to pull (on the same dyno on the same day!) were so inconsistent that I didn't even really look at the numbers as 'counting' at all... rather, the only useful data I got from that was the a/f ratio tuning. Not to mention the price was way higher than what I'm used to paying.

 

that leaves the one dynojet left that I know of that's even relatively close to me, which will be the only place I will go from now on... as long as he stays in business! but he looks very established, so I've little doubt he'll be around for a while.

 

Anyways I don't know why you guys are coming down on me like this. I have not once swaggered around here going "hmmm yeah I got this much hp and torque... my car is SO the s*#t!" nor have I ever compared my dyno numbers to anyone elses in any way other than "hey your power curve looks just like mine!" Not once have I bragged like "heh my dyno #'s are higher than yours!"

 

 

This whole post started as my rant about why I was not thrilled with my experience on the dynapack vs. my experience with dynojets... it really had nothing to do with comparing the numbers between the two... actually if you go back and read the first post THOROUGHLY, all I was talking about was that the dynapacks numbers did not make sense... yes at first I was using the dynojet (THE WHOLE CURVES, NOT just the peaks!) as a comparison, but then in the same post said that the dynopacks numbers didn't even match with themselves! The torque and hp numbers did not match up like they're SUPPOSED to using the equation of torque x rpm / 5252 = hp. And also I could not understand how or why there was such a HUGE variation in my results from pull to pull on the dynapack, even though i was only making small changes to the a/f and nothing else.

 

Whereas I've ALWAYS had consistent numbers on the dynojets... not just from pull to pull, but even from one dyno to another... even though you guys seem dead convinced that even using a different individual of the same model dyno CANNOT POSSIBLY yield the same results. Also, I've always seen appreciable changes (not extreme like the dynapack, but fluctuations that actually MAKE SENSE) from any tuning I've done on the dynojet between pulls. Yes I know you can't tune for a specific load on them like you can on the dynopack or mustang dyno...okay great well since I have not had a need to do that or the ability to make use of it anyways that really doesn't matter to me.

 

And like I was saying... if there was any bragging at all, it would only be that... when I first started building what I wanted to be a fast Z... I started with a built up, high compression N/A EFI setup in an '81 ZX, that put down 141hp and 160ftlbs (on a dynojet!)... So that I've come so far, going to a much ligher 240, and upping output to 233/303... hell even factoring in a big possible variation from one dynojet to another... that's still one hell of an improvement any way you slice it and I think does give me something to pat myself on the back about... whether the numbers are 100% accurate or not, there has been a big improvement there, unless you will try to tell me now that the two different dynojets are just that much off

 

As far as 'well the true test is what it can do at the track'... I disagree. How can you really say that? As much as you guys cry 'foul' on dyno numbers because of possible variations... I say that running the 1/4 mile is NOT necessarily THE benchmark for just how well your car can perform. The same kinda things that affect dyno numbers like weather, altitude and such, will affect your 1/4 times. Also, with the 1/4 mile you factor in one other BIG variation... THE DRIVER!!!! Who's to say I can drive my car down the 1/4 in the best, most optimal fashion and get it to the absolutely fastest time possible? I make no claims of being an pro racer... hell I've only been to the dragstrip once. Not to mention, I'm a big guy, at nearly 300lbs... that's not gonna do any favors for my times at the strip . Unfortunately I'm not friends with any 150lb pro drag racers that I can ask to drive my car for me... Further... I don't have time to go to the strip every week or even every month... so I'm not gonna get any meaningful kind of practice to get really good times anyways. So how would my results at the track be any good indicator of what my car can really do? I think in my case, whatever 1/4 mile time I brought back from the track would be no more accurate indication of the cars true potential than the dyno numbers would be.

[COZY Z COLE]

bastaad525.... Very well said !!!! This has been a very interesting thread to me being that I'm at 24 pulls on a Dynojet for tuning purposes.

 

LARRY