This morning my cousin and I dynoed our cars using a Dynapack 5000 load bearing dyno machine. It hooks to the hubs of the rear weels. It doesn't use a roller system like the dynoJet. I have no knowledge of either system but the shop indicates that a load bearing dyno is more accurate than a system like the dynoJet. The temp was about 52 degrees, Bar. was 25.26 and is the altitude is around 4500 ft.

2005 997 Porsche Carrera S
My cousin went first. He has a 2005 997 Porsche Carrera S (stock it is rated at 355 HP & 295 TQ). He has a six speed manual. After his best run, he was putting about 278 to 280 HP SAE to the wheels. That would be about 333 hp at the crank (using a 20% calculation for drive train loss). That means on this dyno with the high altitude and other factors, he was about 22 hp under the Porsche claims (however, there are numerous east coast dynos showing this car at 355 actual sea level testing). All of his pulls (5) were consistent within 5 HP.

2001 CLK55 AMG
I went second. I have a 2001 CLK55 AMG with a SpeedTunningUSA chip upgrade. It is configured for 93-94 octane. Let me just start by saying that the shop had a much harder time configuring my car to run correctly on the dyno since it is an automatic and the ESP can't be fully shut-off.

Even after I turned off the ESP using the switch inside the car, it still cut in and wouldn't let the car perform correctly on this load bearing dyno (hooked directly to rear wheel hubs). So we pulled fuse 24 and 37 (for ESP) in the engine bay on the drivers side- which triggered the ESP, BAS and ABS warnings. However, this allowed the car to rev up smoother to redline of 6,400. Please note that according to the user manual on page 216, that with these three malfunction indicators "only partial engine output will be available." I am not sure this was the case for me but it is possible I experienced some power loss- I wouldn't think so but I didn't see the timing map either.

Regardless, we went forward with the dyno runs. We manually shifted using 3rd and 4th gear to reach the highest dyno numbers. The best pull came on run 3 which was 303 Hp SAE to the wheels at around 5,2000 RPM. The shop indicated that this would be about 364.3 to the crank (using a calculation of 20% for drive train loss). My other runs varied from about 290 to the 303 to the wheels but admittedly it was hard for them to get consistent linear graphs because of the downshifting of the car under load. They were not happy with this issue, so they didn't charge me.

The shop thought the car was very strong and a 302 in that area was pretty good. The air/fuel ratio was about 13.0 (which I believe is on the leaner side). They also thought it would pull higher numbers if we could figure out how to not allow the car to downshift under load. If anyone knows how to avoid this, please let me know so I can have it retested.

So, it appears that the car has at least a 22 hp gain [342 hp stock to crank vs 364 now] with the addition of the Green Filters and the SpeedTuningUSA chip and possibly more if we can get the car to function properly on the dyno.

I see that Chappy has stock 304 to the wheels at a lower altitude- that is great! I wonder what a chip upgrade would test for you at sea level?

 

Congrats. Based on my prior experience (NA 911's), I had serious doubts. If you're seeing a dyno proven 22 HP increase, there is no doubt.

 

Thanks. However, I am concerned that the results are not as accurate as they could be because the car was downshifting under load- which reduces the HP and TQ readings. Also, the car was showing the ESP, ABS and BAS warnings which may have reduced the cars HP to protect the car and driver.

But, overall, the dyno was pretty strong for high altitude. Still, I feel it could be better. I would like to retest with the ESP functions fully shut off, if possible. I was happy it tested much stronger than the 2005 Carrera S!

 

Have you tried just dynoing the car in third gear? or 4th gear?

 

Yes and yes. We manually shifted the car into 4th but it would still downshift to third under load- which affects the dyno numbers. Without pulling the fuses for the ESP the car wouldn't even dyno as it was freaking out that the car was raised (rear wheels removed and dyno hooked to hubs).

Does your car have the ESP as it doesn't sound the same as mine? I understand this is a problem for most people on the CLKs but there hasn't been anyone who has done a dyno on a CLK55 AMG post what they did, if anything to avoid the downshift and ESP functions.

 

Sorry to report to you that those dynapak dynos aren't more accurate, actually MORE generous on results than any other dyno...

IE..They remove the wheels rolling mass, coupled w/wheel diameter, take away a proven 10% gain from your totals, or get it done again on Dynojet in your area, there the most widely accepted, accurate

Don't be bummed about results being 10% less or more than what you thought w/Dynapak your 4500ft Elevation does steal lots of oxygen = ponies..

Also a 20% driveline loss for the all wheel drive Porsche is quite low prolly more like 24-26% and 20% for your rwd benz also off, more like 17-18%
If you really want to know what your actually getting to the rear wheels ie pavement contact these are the facts

What math is the shop using to get your results? the most widely accepted calculation is 303hp devided / 0.82 = 369.51 hp using 18% loss ie .82
20% would be 378.75

No flame please just trying to help, curious? did you use the exact same dyno pre ECU tuning? time of year? weather? etc..

 

I really don't know myself if a Dynopak is more reliable than a DynoJet- only relayed what the shop indicated (they had very reasonable support for there contentions). I don't really car either way. What is your support for a Dynopak being less accurate than a DynoJet? Lots of people, including shops, will have their choice but I have yet to see a comparison report.

Also, a Carrera S is not AWD, it is rear RWD. Most Carrera S people use a 16% drive train loss instead of the 20% that I used, which would mean the Carrera S made even less HP than I reported. I just wanted to keep the calculations the same so I didnt' get flamed.

 

Take it EZ no flamage lol... OK if not awd then rwd manual correct? then deff 13-16%

The idea behind my post is you want to know what your RWHP is correct? well removing the wheels? they have weight-rolling mass, steals HP, add to that the diameter of the wheel tire set-up 18"-20" wheels plus tire height retard the differential-gears, the taller you go the less hp gets to the ground, removing the wheels changes all this, 99% of tuners use dynojets, yes your motor results are correct if you could drive around w/NO wheels or tires on.

Something called unsprung weight. in a nut shell, sprung weight is weight of vehicle that is supported by the suspension. unsprung weight is weight of the suspension itself (e.g. wheels, springs, shocks, etc.). the more unsprung weight there is, the harder the suspension has to work. hence wheel weight is important. As the suspension to move up and down, it needs to compensate for it's own weight. Momentum is mass times acceleration; so the less weight, the easier it is for the suspension to move up and down. hope that helps.

I'm sure you've read countless threads where guys are constantly searching for lighter perf wheels, the less weight, = less unsprung mass/weight, critical in achieving max perf, just a few lbs less per wheel/corner can = very good results in overall perf. Old rule of thumb is + or - 2hp per every lb in wheel/tire combo.



What about pre ecu dyno? questions?

 

ashutt, I am with you . As long as you feel you gain something with the upgrade and in fact the dyno did show, plus just consider about increasing the limiter to 6400rpm, you gain a lot for that $300 no matter what other people say.

I'll do mine soon and they you know if I feel the same way.

 

I wish you did a pre-flash dyno and a post flash dyno to see what the true HP gain (if any) would be.

 

I know, I asked that same question? although his original post he lists stock rwhp, but doesn't give where, weather, most importantly same dyno or different locale? etc..

 

I don't know where to dyno. But I got my G-Tech as tune tool. It will not give you exact number, but sure it will give you the feel/proof of tune.

 

With all this talk about what dyno does what and who makes better numbers. The real question is when you hit the gas, can you feel the difference? Bottom line......that's what counts! I ask all my clients to go drive the car hard....before AND after.......and tell me what you feel.

Oliver does a great job at Speedtuning, I'm glad you are happy.

 

Thericker,

Please see previous post for answers to your questions about a dyno before the chip upgrade (in short no dyno was done as I was to impatient): https://mbworld.org/forums/clk55-amg-clk63-amg-w208-w209/186989-speedtuningusa-chip-purchase-dyno-come.html.

The tone of my posts, in my mind, were not intended to come across as defensive or threatening. Sorry if they were. I am really looking at this issue emperically so no worries about a difference in oppinion or experience.

That being said, I understand you like the DynoJet but do you have any information from a third-party comparison test to support your theory as I think we would both agree that there are many factors that would affect the end dyno result? As you can assume, the Dynopak group has their reasons why the DynoJet is not as accurate a tool (I don't believe their reasons will be helpful to this discussion so I won't relay them).

Basically, what I am looking for is emperical support either way (i.e. someone who has done both dynoes or an article being written by a 3rd party that compared the two dyno processes and the benefits or faults of each. I was not able to find such a resource.

Thanks for your input.

 

It's not that I like one over the other, just going by facts, reasons, listed above, more importantly what 99% of other tuners rely on as definitive rwhp testing equipment.

I understand your wanting more definitive proof for negating one or the other, but just look at it as simply as possible, wheels off you make 10% more HP wheels on you make 10% less, obvious you drive around w/wheels installed, true rwhp reading would indeed be taken w/them on ie..what's the dyno say when actually driving rubber meats the pavement is what really counts, not w/integral parts removed.

 

Congrats on the gains. As for which is more reliable. The bottom line is this, a dyno should be used for reference. They are great tuning tools. Every dyno will give a different number on a different day. If you dynoed prior to mods and then redynoed on the same day under similar conditions and got a gain, that is as reliable as you need. Way too many people get hung up on dyno readings. Best thing to do is just what you did and then take it to the track and back it up with a mph #, not ET. Thats just my opinion. Congrats again on the gain.

 

Thericker,

It sounds like you are making an assumption that the Dynopack doesn't account for the wheels being removed- right? I don't know that answer to this question but I guess you don't either.

Here is what I have been able to discover, the dynapack is closer in design to an engine dyno and it gives more flexability in how you can use it. The dynojet is pretty simple in comparison. If you want to see what the big companies use look up Rototest- which are expensive- they start at about $80,000. The dynojet ($30,000) is cheap compared to the dynapack ($90,000). Rototest and Dynapack operate on the same theory.

Just because more shops have DynoJet doesn't mean it is more accurate. I would assume more shops could purchase a $30,000 dyno machine than a $90,000 one. This could influence the amount in the market. There are certainly more Toyotas and Hondas in my state than Mercedes but I would be hard pressed to assume that makes them a better car.

DynoJets read whp and use engine rpm to calculate torque. The Dynojet really has no way of simulating vehicle load at speed. This is because, once you get the rollers rolling, it takes virtually little HP from the car to keep it there. I understand a shop can purchase an eddy pack for the dynojet which will permit you to load up the wheel while running the car on the dyno, thus simulating what it would be like to try and keep a car moving on the road, but the reason you hardly even see the eddy pack on a dynojet is because it costs $15,000.

Basically, track racers in our area use the Dynopack because it allows you to tune better. I actually devoted more time to this research on the Internet and I believe you will find that the DynoPack is more expesive (consequently less common) for a reason. This is the same reason I bought my CLK55.

Here is a good link: http://member.rivernet.com.au/btaylo...Equipment.html

I have not used a DynoJet so I don't claim it is a less accurate product, but I have my suspicion after researching the technology further. In any case, it really is no big deal either way. I am sure I will dyno on a DynoJet in the future for fun.

 

Not making any assumptions on Dynapack, there is overwhelming evidence on larger wheel diameters killing perf, as well as, unsprung weight ie heavy wheels killing HP, obviously shines thru w/Dynapak #'s being the heighest of any dyno machine ie..Mustang reads lowest, Dynojet right in the middle.

If you remove wheels, what's next? why not pull the entire engine to eliminate any/all driveline losses? point is w/Dynojet we want TRUE RWHP readings, not to be confused as solely using as a tuning tool for perf increases between mods, I and nearly 99% of the rest of tuners/owners want to know what's hitting the pavement.

Overinflated Dynapak #'s are just that, unless only used consecutively back to back pre-post mods, even then I'd prefer the real street #'s from a Dynojet, or Mustang dyno, but if that's the only dyno around? then sure why not.

 

You seem to be missing the point of my post, which was not intended to be opinion based. Opinions are welcome but I was hoping for support for those opinions, if it exists.

Thus, I have attached a few examples:
(1) At least one person's experience with three different dynos using the same car. You will see in this case that the DynoPack is not rating the HP or TQ higher than the DynoJet, as you claim- http://forums.nasioc.com/forums/show....php?t=1225751.

(2) Here is another link from a user and tuner showing that the DynoPack used resulted in lower numbers than the DynoJet (twice- see graphs)- http://synapsemotorsport.com/forum/viewtopic.php?p=1977

(3) Finally, here is a Bimmer comparison of both on the same day. Data was not complete but it appears the numbers would have been almost the same in HP, if it was not for operator error- http://forums.bimmerforums.com/forum.../t-173763.html.

I welcome your dyno graphs in support of the DynoPack offering higher numbers than the DynoJet. Any support based on a Dyno would be fine with me, as I don't care either way, I just don't feel you are supporting your claims with any evidence.

Again no hard feelings, just searching for the facts, which will be most useful to the readers of this board.

 

The gains look good to me. Thanks Ashutt for trying to help everyone out with your dyno. I for one was holding my breathe since I have the speedtuningusa chip in my clk500 and am tired of people claiming it doesn't work. If you figure out anything please keep up posted thanks

 

 

I suppose there's some room here for a difference of opinion. If I am modifying my motor with the hopes of generating more HP, then doesn't it stand to reason to remove as much of the other factors as possible? Whereas, if I want to know what my "total modification" power looks like - including driveline - then I'd want the wheels on. We rely on factory numbers that are measured at the crank as the baseline from which measure, don't we?

 

Yes deff no hard feelings My intent has never been one of trying to knock you or put you down, just sharing info/research I have personally done, I'll try and dig up some dyno comparisons for the (2) diff systems, not having a specific article written by a person w/credintials, I still can not negate the reality of unsprung weight, rolling mass, diameter of different wheels etc..rendering a penalty on RWHP, I did quote Luke, from Tirerack, backing up my writings on HP losses due to the aformentioned subject matter.

Either way it would be extremely beneficial to your points/if you just went and got it Dynoed again on a Dynojet? obviously with as close as possible time of day, ambient temp etc..

Lastly you never answered my questioning your tuners/results on equation used to get final Crank HP #'s? I have always been told this is best most accurate one....(your rwhp) 303 rwhp / devided by .80 = 378.75 Crank HP that's using the same 20% driveline losses you did. Your dyno operator calculated 364.30 Crank HP? quite a difference? maybe this is where he corrects for unsprung weight etc...?

 

Yes most consumers are drawn in by big manf. Crank HP #'s.....But us in the modding game have come to rely on much more credible rwhp #'s as to giving the real usable power actually hitting the street, not Crank HP #'s which are only good for bragging rights, sales/marketing.

Kleemann is the only tuner I know of that give crank HP results from there dyno machines, and have been proven many times(By multiple consumers after using there products) at unbiased private facility dynos to be fluffing their #'s heavily.

 

The 364.3 HP to the crank is derived from multiplying the 303 rwhp by 0.20, which represents 20% more hp to the crank as a result of drive train loss of HP to the wheels. This is of course an estimate but 20% seems to be what the industry recommends as a accurate figure for drive train loss. Plug any percentage for drive train loss and the HP goes up and down to the crank.

The Porsche guys typically use a figure of 16% (0.16) for drive train loss, since the engine is right over the rear wheels. However, I used 20% to be more generous for my cousin's Carrera S.

As a side note, the amount of exhaust pressure is pushed out of the car at around 5,000 RPM is incredible. I only noticed while holding the A/F sensor since it wouldn't insert into my oval exhaust tubs. Had to use welding gloves so as not be burned.

What does your Vet put down to the wheels? Is it the 400 HP and 400 TQ engine?