mark kibort

put up that money, because I would bet that any day of the week on a dynojet 24e, or any roller dyno. even a brake dyno, which ive run on before.

the power very closely follows the improvement for lap times and matches comparisons for straight line acceleration from my 200rwhp 4.7s all the way in stages to 335rwhp. since all the same dynos were used, thats like saying my 200rwhp (or even 189rwhp before that was inflated! )
also, the same dyno was used when bolting on 6.5 liters on to the 5 liter top end stuff, NO other changes. 372rwhp vs the 320rwhp prior measurement. based on my lap times and shift points on tracks, this is almost perfectly expected. dennis measured his HP on a dyno near by. Im sure I could run on his and get my same results. we went head to head on the track for a straight, and his car acted just like his dyno. same power as me, but a rising HP curve, not flat. so I had a big torque advantage post shift to mid gear.

mark kibort

How are they inflated? you ether spin the rollers at a certain rate, or you dont. you cant fool it, unless you play with the correction factors and even then there are realistic limits. how you tie it down, tire inflation, tire durometer, all will play a factor, albeit a small factor. Ive done some experiementing there. also, air to the intake, using fans, etc, can also change outputs data

I dont agree, unless you are talkng SAE correction factors.


15% is generous, and that usually happens at high speed and near redline.
doing coast down tests, rolling friction losses range from 20hp to 10hp from 150mph down to 80mph. I thought the GTS was 350flywheel, that at 15% loss, that would be near 300rwhp

when i went to laguna with my new cam set up. my video showed and was obvious on the track that i couldnt get the engine to rev up and hit my points on the track. we are talking 10hp diff, as shown by the dyno . I also noticed 60-100mph times as measured on level pavement, was ailing ! (5.7 seconds vs 6.5). at the track, we advanced the timing of the cams, and regained the lost power. went back to the dyno after and the power was back up to 318rwhp with the new 85 modded cams. (before 308rwhp before the race) my lap times also showed the improvement after mods. it was very noticeablle, and also proved the dyno was a useful tool and pretty accurate in detecting the issues, even at a 10hp difference level.

RKD in OKC

I thought the SAE correction on the dyno was so you could compare your before and after runs on different days despite the weather ie., barometric pressures, temperatures, and humidity. The local dynojet I use is a NASCAR certified dyno. That means they keep the calibration of the dyno up so that it can be used (and is used) by NASCAR competitors. I have no idea why NASCAR would need or use a dyno in Oklahoma City, but I have had to reschedule because of it.

Lizard928

we have found another point where MK is the master of all information apparently.

Go ahead and drive your car up here and put it on the same dyno I use and I will put the money where my mouth is then.

And seeing as how you are the expert on all of this, you should have no problem explaining exactly how Dennis Kao's 928GT put down 350rwhp before his build up. I saw nothing in his build showing anything but stock parts.
I am very curious in this as this means that everyone else could get 350rwhp out of their GTs, without a full teardown and blueprint!
I expect a good portion of that will be able to be transfered over to all the S4's too!

Now where did I place that plate of torque

James Bailey

NASCAR as an organization has several series including local short tracks often with very strict limitations on engine power modifications in order to keep it competitive and hold down the costs. Perhaps that is who uses that dyno ???

hacker-pschorr

NASA too, a dynojet at each event.

My friends Corvette team regularly uses three different dynojets from Green Bay, Milwaukee, and Chicago. Then on the road the portable unit's at various tracks including in Utah.

The variance is always less than 1%, unless something is wrong with the car. This is going off data from 3-4 different cars on his team.

This is the #1 reason why I'm only using dynojets unless one is not available. Too many erroneous factors with a lot of the other brands out there.
A certain dyno sheet from a few years ago that showed environmental factors that only exist in the eye of a hurricane comes to mind.

All that aside, there is always the factor of something could be physically wrong with the unit and / or software.

Dyno brands aside - it's most important to pick one and stay with it and don't worry about comparing across different brands.

Long before the Nationwide Series came to Road America, Cup teams were renting the track to help setup the car for their road events. Most of them would show up with flat black painted race cars and blanked out transporters to try and hide who was in town.

Lizard928

So, wait a minute, RDK and Jim. Do you mean to tell us that NASCAR makes the guys go to certified dynos?
But hang on a minute, MK has just told us that every dyno is the same, and that regardless of everything they all will read the same.

Apparently MK needs to teach those guys at NASCAR a thing or two about dynos!

mark kibort

No, just a master of relaying the FACTS . when we post about air filters, driving styles, there can be debate, BUT, when we talk about a lap time, or a dyno run, or drag slip, or a physics equation, it is kind of an absolute. you either do it , or you dont.
If I spin the rollers in a certain time at a certain rate, its a HP value. UNLESS the rollers are not the same weight or diameter, the results are the results.

Not an expert, just relaying the facts. so, instead of mocking what you seemingly dont understand, why dont you give me a logical, scientific scenero, where two dynos would put out different numbers! how is it possible? I would really like to know what Im missing here.

Now, lets explain dennis' motor. did you not follow the process and facts of his build??? Ill cut to the chase. dennis had a SPECIAL grind cam to start. PLUS, he did some things in the rotating assembly that he and Jim Morton would help with power. lighter weight compoents, oliing changes, etc.
So, you ask? his cams with 1mm more lift and more duration, made 15 more HP than my same set up. not a stretch, by any imagination.
edit: also, when he did the tuning with the norcal boys, they got it up to near 375rwhp. (they claimed 381, but it was mostly end of dyno noise) they did it with fuel and ignition timing tuning! and keep in mind, this cam allowed them to run up to near 7000rpm, making power all the way up. Ron's GT in LA, made 320rwhp as well, same as mind did mid lifte. keep in mind, mine had air box mods too that seemed to improve pressure drops in the airbox.

Now, I was going to buy dennis car before he did. it was near the same as the holbert car as far as HP but with more mods making up for the fact that it was an S4, not a GT. (only headers.) 298rwhp by the way to to start.

where did you get your information agian??

So, now that I dont have the holbert 5 liter making 320, you think the 372rwhp for the 6.4 L is high? willing to bet on that? how about all the hundreds of dynos of others cars Ive tested, on multiple dynos in the area, ranging from 200rwhp 911 '84s, to scot's 290rwhp 5 liter part euro Ljet.(going from a very believable 220rwhp , 250rwhp 4.7 euro ,going to 290rwhp with the 5 liter bottomend. you cant have it all ways. if im off on my dynos, then all the other cars ive tested over the past 15 years would be high, and they were just to strong on the track to be weaker on the dyno.

mark kibort

again, your comprehension needs some work.

rolling dynos (inertial), of the dame brand, are the same. (not brake dynos and others.) . If they are not, they still use a very simple physics calculation to determine hp. rate of change of kinetic energy! defined, that is HP! find the rate of change of speed, and you know the hp. you either do it, or you dont. ITS exactly like a drag race down the track. you either ran it or you didnt. you cant fool the system, unless you mess with weights of the drums or something.

actual dyno runs, tell you exactly how much power is put to the wheels. actual is actual! SAE changes things up or down based on advantages of the conditions, but on a standard day 65-70degrees without extreme humidity and at near sea level, there will not much difference.

There some subtle factors with tires, presures, strapdown, etc, but not earthshatering. nothing an operator can do to boost HP. (unless you modify the software, lighten the drums, etc). assuming no foul play, a rolling dyno will be showing what your car can produce as far as HP. if it isnt, tell me how it isnt. forget about SAE corrections. this is why i go to the dyno in summer on an 85 degree day and then in winter in a 60 degree day and look at the actuals. Sure the SAEs are relevant too, but looking at actuals on similar days gives you a good indication of what you got. we are not shaving hairs here. if its 4-5hp off year after year, thats the same in my book, BUT, if we are doing comparison testing on the same dyno day, much more accurate changes can be detected.

soupcan

This is why I like to sneak out late on Saturday night and do a little street racing.

mark kibort

Thank you Eric!

Lizard, (colin) this is the point!

Mark

by the way, all you have to do is tell me how my actual roller run at 335rwhp actual and SAE corrected, could have been inflated. (particularly, the actual run). forget about putting your money where your mouth is, how about just come common logic or physics?

RKD in OKC

When a NASCAR team came in with a car to use the dyno he basically had to shut down his shop while they were there and had a non-disclosure agreement that he couldn't say whom was using his dyno.

When I had my 944 Turbo that put down 408 SAE rwhp, there was a "who made the most dyno hp" war going on in the 944 Turbo community here on rennlist. Mine made top 10. They argued dyno vs dyno, mustang vs. dynojet, etc. Lindsay Racing even took a car around between a dynojet and a mustang dyno to make runs within an hour of each other on the two different dynos, I don't remember the resulting difference. The group eventually decided an SAE corrected dyno chart from any dyno was acceptable to post and be considered for the top HP list.

Lizard928

MK,
the second statement was a rhetorical one.

And I have seen differences in town and even between dynos. I went to one as I stated before and it showed 250rwhp, that same car made 300 on Louies Dynocom, then after more tuning, and working out some kinks, I saw 310 on another dyno here in town.
There is another dyno here in town. I needed to tune a car and the one I normally use was occupied. On this dyno the car I was tuning put down 230rwhp. A couple weeks later with no further tuning etc. that same car put out 250rwhp on the dyno which the initial baseline was taken. I also have done dyno runs on a shop down in Tacoma (unfortunately they are not around), all the local guys confirmed as well that dyno typically read a little higher numberwise than Louies.

You say that things cannot be changed, and that everything is equal. What are these machines hooked to? Computers, and yes, they can be manipulated. If all dynos had only a very slight variance between them, then why would a national body like NASCAR or NASA require them to be certified? There is no reason. Sure there are a vast amount of the dynos which run fairly consistent numbers. But there are those that do typically read high, and those that read low. Who knows, maybe it is because the shops have not had them calibrated in a long time. It is very possible, and all electronics like that do need at a minimum an annual re-calibration.

And with regards to Dennis's car, I could be wrong as it has been a very long time since I have gone through that thread. But I was sure that his base number before he started his build was 350rwhp.

As to your new motor, no those numbers are not outragous for a 6.5L well, maybe not by US standards.
You really need to get that car tuned, and get some cams in there to make it breath a little more!

Jim Morton

FWIW, Dennis' "base" number, no tuning was 335... Whether it's 335 or 320 is really irrelevant to me as it is the delta values that I concern myself with.

As another FWIW, debating all this power here, power there is futile and only serves the purpose of the poster and those selling parts / services. I say this as I do not think Dennis' engine build represents any sort of large effort or result. It's simply a typical track "hot rod" setup tuned per traditional methods.

The VE of Dennis' engine is nothing to brag about. The BSFC is pretty good, but at the end of the day it's a matter of what your goals were and whether or not the owner and / or builder is satisfied with the result. For Dennis, he wanted me to work to extend his power curve a little higher than what we saw from stock S4 engines. Not only did we see what we wanted, he was happy with the results of the effort.

As fo a few months ago, Dennis' engine now has larger intake valves and some mild porting on the intake ports. We have not re-tuned as we are both very busy. After this setup, we may try some "larger" cams that I have been modelling. I have no plans to go to larger cams until I feel we have gotten all we can from the current setup.

YMMV

IcemanG17

It does appear that GTS's are not the performance upgrade they appear....especially with the extra weight.... 280ish whp seems a common #....with some mods they can get to near 330whp (GT cams, xpipe dual 2.5" exhaust) in 5 speeds....

S4 5 speeds are all over the map.....maybe 275whp for a pure stock one.....then as high as 335whp for the old holbert car (hard to say its stock).....Dennis's engine still holds the record for a 5.0L at 387whp...a typical # for stock S4 5.0L with race exhaust is around 300whp....

However I am quite happy with my lowly 203whp!!!!