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

[Guest bastaad525]

okay this is probably silly, I just noticed this when I was showing some dyno sheets to a friend last night.

 

Between the last dyno runs I did on a Dynojet dyno, and the last time I dynoed and tuned, on a Dynapack dyno, I noticed, the numbers dont jive with each other.

 

The Dynojet graph ended up showing a much higher torque peak number, but a lower hp peak number, vs the Dynapack. I figured... okay so the curves are just different. Nope... the peaks are in the same places, and for the most part, the curves are relatively the same, so I started looking on a 'point by point' basis.

 

Sure enough... they're off.

 

I compared, for instance, the torque and power numbers at 4200rpm (right about where the torque peaks). On the dynojet, it's at 269 lb ft at 4200rpm, on the Dynapack, 248 lb ft at 4200rpm.

 

At that same RPM, the Dynojet shows 208rwhp. The Dynapack shows 220rwhp... whaaa?? The Dynojet shows 20 MORE lb ft of torque but 12 LESS hp at the given rpm? Given that hp is just a derivative of torque, the number being determined by throwing the torque number into a set math equation... this totally does not make sense. Really odd... I'm gonna find that math equation and figure out which one is actually wrong...

 

 

 

EDIT: looks like the dynapack is the one that's off... 248 ft lbs x 4200rpm divided by 5252 is 198rwhp, not 220 like the dynapack graph shows. And the hp peak should read more like 210rwhp on the dynapack as well, if I'm figuring correctly. That seems really low considering I made 200 at 10psi w/o an I/C... with the I/C and 12psi and 99% identical air/fuel ratios I shoulda gained more than 10hp Unless the Hp number is right and the torque number is actually the wrong one??

 

ANOTHER EDIT! Another odd thing... that dynojet graph I'm comparing with was my last run of that particular session... that was the session where the wideband O2 was freaking out, giving funky readings, showing a/f ratios at up at like 20:1! So I remember I had turned boost down a bit from the first runs, and I remember I started at 12psi. I was so worried, with those lean AFR's, that I was gonna melt something, I was still running bone stock EFI, so I ended up turning boost down quite a bit by the time I did that last pull... I think it was like 9 or 10psi (at which point it was still giving me mad lean AFR's in the 20's and I figured his sensor musta been FUBARed). I dont' have the graphs for the first four dynojet runs, but I remember the first run (he only pulled to 4000rpm when he saw it go way lean) peaked torque at like 280ft lbs!!

 

On the first run on the dynapack, the BEGI FMU was set to do nothing, and I had set boost back up to 12psi. I wanted to compare O2 readings to confirm my suspicions about the wideband readings from the dynojet... wouldn't ya know it, afr's never got higher than the 13's on the dynapack!! And yet, my power numbers were way down right from the start?

 

I knew I shoulda just stuck with dynojets... now it's almost like that last dyno session was useless (well... except for allowing me to tune my AFR's I guess).

 

Either way, isn't it odd that the dynapacks numbers don't jive with the math equation?

[Guest bastaad525]

well... I guess I'll be trying to get it to a dynojet soon. $75 waste but... kinda bugs me not knowing what's really going on... I mean, if it's really only 210hp, that SUX...

[Guest Cronic]

EDIT: looks like the dynapack is the one that's off... 248 ft lbs x 4200rpm divided by 5252 is 198rwhp

 

----

 

Remember, you're making 198rwhp @ 4200rpm by that calculation. That's not your peak #. Just what you're making @ 4200.

[Guest Cronic]

PS: At 15psi, you should be right around 230whp @ ~5200rpm

 

I put down 206rwhp on a mustang dyno @ 15psi. Mustang dyno = 10% less then Dynomometer.

[Guest bastaad525]

I put the dynapack graph into MS Paint and drew in the correct hp curve. The HP was off all the way across. The HP peak should have read 210rwhp at 4600rpm... no idea why my hp is peaking so early, but it stays pretty level up to about 5500rpm. I wonder if they were applying some kind of correction to the hp but not the torque?

 

I thought 15psi was good for more like 250hp? Garret76zt is making 274hp at 15psi on a stock T3. Of course he's got full exhaust, big TB and 370's. Those mods enough to make 60hp of difference? I was figuring on having 230ish at 12psi I was making 200 w/o the I/C at 10psi... 2 more psi and added I/C should be worth more than 10 more hp! Maybe the exhaust is crappier than I thought? Or maybe there's some other bottleneck I dont know about.

 

Something I noticed, on ALL of the dyno pulls I've done since installing the I/C, there is a lot of fluctuation of the torque curve as I was tuning and also from testing on two different types of dyno. Torque peaks were as high as 280 ftlbs and as low as 240ftlbs, but the torque ALWAYS falls to about 240ftlbs at 4500rpm, and falls off at the same rate after that, regardless of the peak. Which is why peak hp stays almost exactly the same even with the vastly different torque curves/peaks.

 

I'm hoping now that I"m running 14psi I'm back up near 230hp... of course there is now the small issue of boost falling off a bit at higher RPM's.... So I probably only gained more torque and HP will still stay the same Only another trip to the dyno will tell *swears off Dynapacks for good*.

[Guest Cronic]

Some guys are making much more then I am at the same boost level, but at 16psi (20 spike) I made 266/324 dynojet numbers. Now I can easily see my turbo being old, and my motor not being fresh, as me losing 20whp compared to another person. My engine does burn oil, and has higher compression then stock, 150psi/cyl. So that could make a difference.

 

Oil getting into my cyls actually causes the gas mixture to drop in octane, which will cause less power.

[Guest bastaad525]

yeah well.. my engine is 95% rebuilt (heheh don't ask about the 5%) and doesn't burn any oil at all. The turbo... I dunno, but it has no shaft play, and I dont get oil in my intake pipes, so I assume it's good as well. Admittedly, Garrett's example is a bit extreme... I was pretty shocked when I first read his numbers... but I remember the common consensus being that 15psi should be close to 250hp. I figure Garrett running the good exhaust and TB probably goes a long way towards explaining the extra 24hp. And considering that's about all his setup has that mine doesn't (he's got 370cc inj's but the FMU I have provides more than enough fuel) I find it odd to be SO far behind him. Or so far behind you, for that matter... I had no idea that 20psi was a spike, thought that was the boost it was at full time. So 266hp at 16psi... still tells me I shouldn't be far behind at 14psi or at the 12psi I dynoed at... even at 10hp per psi I get right back to the dynapacks original 226hp number.

 

I dunno... anyways... who's to say that on this dynapack dyno chart the hp is the wrong number? Maybe the torque is too low, and the HP is right? Optimistic thinking? Well.. it jives with everything else so far. It explains why my torque was SO much lower on the dynapack. And fits with the HP number being just about right for the boost I was running and such, as well as being the expected increase in power from when I was running 10psi no I/C. Hell, I even used that estimate of 220-230rwhp to estimate just how much fuel pressure I'd need to get the a/f ratio right, and that guesstimate was VERY close on both sides, both the fuel pressure and the estimated hp that amount of fuel would be good for... I was shooting for 230hp at 65psi.

 

 

Thanks for humoring me with all this by the way, Cronic... think my threads are becoming maybe a little unpopular (or maybe infamous?) because I am a long winded poster Too much free time on my hands I guess *shrug*

[johnc]

Between the last dyno runs I did on a Dynojet dyno, and the last time I dynoed and tuned, on a Dynapack dyno, I noticed, the numbers dont jive with each other

 

Comparing dyno numbers from one dyno to the next is a fool's errand. You're just going to make your head hurt...

[Guest bastaad525]

John - actually I was originally going to pass on the dynapack place, for that very reason. BUT, I had talked to a couple guys who've been to this local place and they said the numbers were usually pretty similiar between dynapack and dynojet. Agreed... I wouldn't split hairs over a few hp or ftlbs, but we're talking really big differences here.

 

Anyways, that's not even my main point... my main point is that the dynapack numbers dont even agree with themselves! If you take torque at any given rpm on the dynapack sheet, and put it into the T x RPM / 5252 = HP equation, the hp at that rpm is NOT what it should be using that equation.

 

Anyways... here's another example of me having too much time on my hands .... Optimistic though it may be, it makes even more sense to me now, that the HP is actually the correct number and the torque number is the one that's off (too low) on that dynapack chart. I just plotted another graph of my own, drawing in a new line for torque figuring it from the hp numbers the dynapack gave originally. And then laid all that over the dynojet pull, throwing in A/F ratio as well for comparison, and got:

 

(dotted purple is the dynapack torque, dotted blue-green is hp)

 

Notice that the torque curve follows almost EXACTLY, only the whole curve is about 200-300rpm. This strikes me as very funny, because I distinctly remember the tach on the dyno computer reading about 200-300rpm higher than the Z's tach. I never did ask him why that was, figuring my Autometer tach was probably off. But... then I see this... and knowing that his dynapack was off for certain in one respect, who's to say it wasn't HIS tach that was off? The whole thing about RPM being off COULD account for the HP/torque discrepancy, since hp IS just figured from RPM! So if this is correct, I really did put down 226rwhp, but the torque peak was actually about 270ftlbs, and that was at 12psi. But then I think "okay well... yeah the torque curves match up pretty closely, but I was running 2psi MORE on the Dynapack" Yeah... but this fits as well, because I did six pulls on the dynapack, tuning the FMU in between each one. On the first pull I was pretty lean, so I richened it up until the AFR was where I wanted it by the sixth pull. And on the sixth pull, having richened the mixture significanly, I had lost 20ft lbs of torque! So the first dynapack pull would have read 20ftlbs higher on this graph as well had I left it so lean, and makes sense for running two more psi!

 

 

It all fits just a little too perfectly, IMO

[Guest bastaad525]

Not only was I right, I was BETTER than right

 

It was driving me nuts, so I took it back to the place I dynoed at before that dynapack place, back to the dynojet. I figured... there's no other way I'll know for sure if what I've done has made an improvement or not.

 

SO... for once, I'll keep the post short, and get to the goods!

 

 

I was right about the hp afterall... actually it's climbed a few ponies (maybe from bumping timing 2 degrees? but probably just differences between the dyno's). But then the torque... WOW!!!! 303 ftlbs!!! WAY more than the 248 the dynapack was giving me. This was the Corvette specialist place, this guy is used to seeing only Vettes in there, and he was pretty shocked by the torque number... said that's just about what a stock '04 Vette puts down... oh and he said I NEED a cam ... talking about the fact that torque falls off so fast resulting in the much lower hp number. Yeah well actually I hope a real 3" exhaust will take care of that top end when I get around to it. Sweet HP curve though... 200+hp from 3500 to 6000rpm

 

Another note, I was watching boost... it was hitting 14psi and slowly tapering as I've described before, down to about 11psi by 6000rpm. So that accounts for the torque falling off as well.

 

Altogether a WAY better looking curve that what I got on the Dynapack, OH!!! And I did fiddle with the FMU between runs... man now I'm convinced something was wrong with the Dynapack. Remember how I'd said that richening it up a bit, resulted in a lost of 20 to 40ft lbs of torque thru the rev range, and screwed the power curve all up making it a peaky lumpy mess. On the Dynojet, adjusting the mixture had VERY little effect, only a couple hp and ftlbs either way I went (just as BLKMGK said it would).

 

I will NEVER tune on a dynapack again

 

Only downside to the whole day? It started POURING rain on my way home... after it had already become clear and sunny, it decides to start raining again. First time the Z has been in the rain in almost a year... I was pissed. And the moral is... check the weather forecasts before taking 30 mile trips to the dyno.

[Scottie-GNZ]

Stop trying to make sense of dyno numbers and how those numbers compare. The only comparison you should be concerned about is those between your passes on the same dyno, regardless of how the dyno derives its number.

[80LS1T]

Stop trying to make sense of dyno numbers and how those numbers compare. The only comparison you should be concerned about is those between your passes on the same dyno, regardless of how the dyno derives its number.

 

Exactly! Any guy who knows what he's talking about when it comes to dyno numbers knows not to compare one dyno to the next. Stick to one dyno and then tune off of that one. That way you will know just how much of a difference each mod did after the install!

 

Guy

[wigenOut-S30]

also. take it to the track That is a good way to " test and tune" your car.. hehe. one of the main reasons I go to the track is after I do something.. See what she runs

[Guest bastaad525]

Stick to one dyno and then tune off of that one. That way you will know just how much of a difference each mod did after the install!

Guy

 

 

yeah... I wish... don't think I haven't tried. Before I found this corvette place, I had been to three other dyno shops. Not by choice... every time I went to one, did a baseline, and then went back after a while to test or tune some new mods or whatever, they were out of business! It's like some kind of curse of mine... once they test my car their shop is doomed I think I'll be able to stick with this Corvette place though, the guy is cool, the price is good, and considering the high dollar clientelle I'm assuming he's not going anywhere any time soon.

 

 

I'll say it again... I'm not really that concerned with the differences in the numbers between the dynapack and the dynojet (but I'm glad the dynojet gives me a bit more to brag about ), as much as I'm left wondering why the dynapacks numbers are just wrong. And also, why I got such vastly different power readings from the six runs in a row I did on the dynapack. Of the five times I've been in a dynojet, I've never seen variations of more than about 5hp/ftlbs between any of the runs. Even today when I adjusted the FMU over a wide range between the three runs, power changed only very little, unlike what happened on the dynapack. I thought the dynapack was supposed to be super consistent and great for tuning? I wouldn't call 40ft lbs of torque variation from one run to the next 'consistent'.

 

 

Well, the good news is even when comparing the dyno numbers from today to the last time I dynoed at that same place, power and torque are up significantly, more than I would attribute to simple weather variations or whatever (up 23hp and 30ftlbs), which tells me, at least, that I'm going in the right direction.

 

 

Anyways... whatever happened to "Congrats Bast" or "Nice numbers Bast!"?

[Scottie-GNZ]

Stop wasting all that money for passes on dynos. Invest in an LM-1. Find a buddy or 2 who has the same interest and share the cost. Then, take the car to the track and run it and tune it in the process. Eventually you will become one with the car from seat time and learn to tune your car in the process.

 

What good is a peak HP dyno number unless you just want it to brag? A big dyno number is useless if you cannot put that power to the ground. Going quick down the 1/4-mile is more than having lots of HP. Forget about attaining a HP number. Tune it at the track to increase MPH and with seat time, experimentation with tire pressure, burnout and launch technique, quicken the 60' time. Then you can brag about a stunning ET/MPH and just think of the fun you will have doing it.

 

I do not have the biggest HP number here but I have one of the quickest street-driven cars because I focus on more than HP. Tuning, seat time, tuning, suspension, tuning and , oh yeah, tuning. In case you do not get my drift, you tune more than just the engine. The GNZ has been to the dyno once and it was a waste of my time and money.

[Guest bastaad525]

Scottie - it's not a waste of money if it brings a smile to my face And anyways, I didn't JUST go to get some numbers, I was there to re-tune a bit, see how the FMU was performing or if it was operating any differently. Cygnusx1 or someone had advised me that the performance of the unit could/would change with the seasons. Well... when CA changes seasons it does so pretty rapidly... we very quickly went from 80-90 degree days (it was 97* the last time I dynoed and tuned) to pouring rain and 50-60 degree days, so I wanted to see how that affected the tuning.

 

And the LM-1 is already tops on my X-mas list.

 

The problem with me doing as you suggest is that it's impossible for me to get in the kind of track time some of you guys do, or the kind of track time that I'd need to really use that as a tuning tool. In the last 7 years of Z ownership I've only gotten to the track twice. Not because I don't want to go. This is because there's not really a track 'close' to me, the two I know about are about an hours drive away, and also because I usually just can't go. Either I'm working the one night a week that the track is open or I've got other things to do, or there's just no way to work it into my schedule. I haven't had a job where I get weekends off or a 9-5 job in a very long time. Now that I work nights, it's even harder for me to get to the track, which is why I haven't even taken the Z there since installing the turbo motor. So track 'test and tuning' is really out of the question for me. When I finally do go to the track it will just be to see what she can do, and given my pretty bad skills at launching and stuff I would not even consider my times to be a good indicator of what the car is capable of. I'm very strongly considering getting someone else to drive the car whenever I finally do get it to the track, because I'll probably never get the kind of practice time I'd need to get a useful number myself. Until then, the dyno IS the best indicator for me of what the car is capable of, and the dyno number is not affected by me being a lousy driver It's as much about a number to brag about as it is a way to see how I'm progressing and the effects of the things I'm doing to it. I know there's lots of guys here have more HP than me so really the 'bragging' doesn't even apply.

 

And by the way, I"m NOT interested in tuning my suspension to make a faster 1/4 mile car. Hell... I don't even care if it's the stickiest mountain road car... like when do I ever even get to take advantage of it like that? What DO I get to do with it, other than the quick blasts up freeway onramps? Seriously, as little as I get to really push, test and enjoy my car in that way, one might be left wondering what the point of building it up like this was in the first place

[johnc]

I know its a long drive for you, but I recommend Superior Automotive Engineering in Anaheim, CA. I used them 3 different times for chassis dyno tuning on my L6 and, after environmental corrections, they were within .5% every time.

 

http://www.superiorautomotive.com/

[cygnusx1]

Cygnusx1 or someone had advised me that the performance of the unit could/would change with the seasons.

 

Nope, wasn't me this time.

 

I do the same thing...I tweak and tweak and tweak but really for no reason other than I can go for another big-grinned test drive. No dynos around here and no tracks within and hour or two. Lots of twisty, hilly, roads though. Tomorrow, will be my first time EVER on any track and it will be Limerock Park Road circuit. Lessons and time trials; brain tweaking.

 

Funny thing is after all this tweaking to go faster, I am proabably going to turn down the boost to about 12psi for the track day. I am there to learn; not to break records, break my neck, or break my Z.

[Gollum]

This is a prime example of why i hate it when people treet dyno nubmers as the bible. It takes a VERY expensive dyno to put out perfect results. For the most part dynos vary alot between eachother. Now, one make/model should perform very clost to another of the same make/model, but you still never really know. And then there are other factors as well, such as humidity, temperature, engine temp, and many others. Cars fluctuate a couple of hp every day. They're not just ON. They vary upon many facors. There is a percentage that you have to count on. One day you might run 13.5 and the next weekend might run 13.2. You might have tail wind. It might be that much cooler outside. You never really know. Dynos have similar variables to them.

 

Now, if you're recieving totally different curves that might worry me. This would mean one of the dyno's calcualtions are off only at certain rpm, wich is strange. If it's off it should generally be off a percentage.

 

Wierd stuff any way you look at it.

[Guest bastaad525]

Cyg - I can never remeber who tells me what any more!

 

Gollum - my results have always been very consistent between Dynojet dyno's, and I prefer to stick with them (people need to stop closing up shop!). The Dynapack gave WAY different results, not by a percentage. The whole curve LOOKED way different. Torque peaked at way higher RPM on the dynapack (4200rpm vs 3000rpm on dynojet), and was a much peakier curve, way less torque from 3000-4000rpm, no plateau like I've always seen on the dynojets.

 

And the HP graph did NOT match the torque graph. And why did power vary SO MUCH from run to run on the same dyno, same day? Well whatever... It's not like I'm trying to compare to anyone else, not sure what you mean about people treating dyno numbers as the bible. I just want to accurately gauge what effect my mods and tweaks are having on my car... and have a bit too much time on my hands lately to think and type about these things