Tuning Scams

[ah206]

I went with a friend of mine the other day to get a dyno tune on his C5 Corvette. The car was already tuned for a smaller cam. I pulled the tune file before the dyno and after the dyno. The tuner got in the car and pulled the tune file. He was there for a while but I couldn't see what he was doing. He made a baseline pull. He then added some timing and leaned out the pe afr(his words). The second pull made 38 hp more. He then said he would try 26 degrees advance and see if it gained any power but it didn't. Friend paid $450 and we left.

Now here's the good part. I opened the before and after files and hit compare. The new tune showed automatic transmission settings changed (The car is 6 speed). The timing tables and modifiers were exactly the same. The pe afr was 12.0 up until the last few cells where it was changed to 12.5. Original was 12.0 across the table.

How common is it for a tuner to intentionally pull timing advance on the baseline run only to show a hp gain after "tuning"?

I personally feel this guy is scamming people. What do you think?

[tris909]

I have never seen anyone go to the effort of de-rating a tune file for dyno power run purposes. Although intake air temp has a big bearing on chassis dyno power run results.
i have known people to tamper with IAT input on the dyno to achieve high number, which is plane just cheating.
The differences of power output can be as much as 35rwkw.

[ah206]

Tamper with IAT? Not sure I follow you. They were back to back runs with about 20 minutes in between. Nothing was done under the hood. If you mean the IAT spark advance modifier tables then maybe as that would effect the total advance. We left with the exact same spark advance that we came in with. VE and MAF were not changed. Just raped the PE table in a few cells to lean out .5 on top end. I guess my question is what's stopping someone from pulling 10-15 degrees of timing, doing a quick write to ensure they show a power gain and get paid?

[tris909]

IAT input has a bearing on the dyno retarder load and ramp rate (particular dyno dynamics) . It calculates iat and ambient temperature on the dyno "weather station" as well as other settings in ramp etc and applies load as necessary to the retarder.

I personally would never think of going to the effort to read, rewrite and run a vehicle for a low number. But that's not to say people may do this.

[07GTS]

another "trick" is and im not a professional tuner or have a dyno so this just something i have picked up on just by being at dyno comps and my own vehicle ect, the first run is always low the second is always a more and the 3rd should be close to second maby a smidge higher and this is without any changes, so in my eyes if a single base run is done the following run will be higher even if no changes are made so its a false positive if an adjustment has been made or can be used to show a gain when there really arnt any, so a base run should be at least 3 runs then start to make changes to see any improvements, with mine the 3-4-5 runs are always within 1-2 hp but the first and second can be 30-40hp difference, not sure if this rings true with anyone alse but just something i have noticed...

[sillycon]

another "trick" is and im not a professional tuner or have a dyno so this just something i have picked up on just by being at dyno comps and my own vehicle ect, the first run is always low the second is always a more and the 3rd should be close to second maby a smidge higher and this is without any changes, so in my eyes if a single base run is done the following run will be higher even if no changes are made so its a false positive if an adjustment has been made or can be used to show a gain when there really arnt any, so a base run should be at least 3 runs then start to make changes to see any improvements, with mine the 3-4-5 runs are always within 1-2 hp but the first and second can be 30-40hp difference, not sure if this rings true with anyone alse but just something i have noticed...

I've observed similar behavior on some, but not all, dynos. I never actually thought to try and correlate the results to see what the cause was, however. It could be as simple as blow by from a loose piston/wall clearance due to the engine being cooler on the first few pulls. The way I've usually seen it done is do a few baseline pulls until you get consistent numbers, then make changes, do a few pulls until consistent numbers, etc.

No doubt there are a *TON* of "cheaters" out there though who will jack a couple cells to get a better peak number and leave everything else untouched. Sadly, it seems more common than many would want to admit.

[tris909]

Another action that can alter results is how the vehicle is tied down on the dyno, such as to much load on the straps.

[GHuggins]

I've never seen the load on the straps change things unless it's just too loose for the tires to get traction on the drum and then I think you would just be too dangerous to run the vehicle? I always try to strap them down tight, but that's me - I prefer to be safe and as safe as possible to the car...

As for adjusting the iat for the dyno - I've seen a few - even some well known shops screw with this - look at your correction factor in the notes section to see if it changed substantially - this should tell you something...

A big cheat factor I've been seeing lately is engaging the brake on the dyno - not to be confused with the eddy brake - right towards the end of the pull to shoot turbocharged vehicles numbers through the roof - watch some youtube dyno's of especially one big named shop and watch for sparks shooting out from under the vehicle as the brake is engaged... The more drag or resistance = less drivetrain loss... I use the eddy brake with a "Vehicle Mathematical Profile" to simulate the weight and wind resistance of the vehicle only - anything else is just being underhanded IMO... AND before anyone says anything to me using the eddy brake like I do - we've compared our dyno to others and typically other than a mustang dyno - our dyno puts out numbers 20 to 30hp less than the rest... Plus without using the eddy brake you wind up with too lean or way too rich conditions on the road itself - I pried myself in doing tunes right - just one of the reasons I do it like I do...

Another way of cheating - so you don't screw yourself over as a end buyer - is reloading a tune that's currently learned itself down to the low octane table, so now it's back on the high octane table - you'll see gains with that alone...

I've never seen one 30hp shy on the first pull doing it the way I do with the eddy brake - did see weird things like this without the eddy brake - I do 3 to 4 pulls with the scanner going to see what spark table it's on - to verify baseline...

AND then one final thing to watch for - look at the baseline numbers - if a stock car is putting down something very close to or over factory rated flywheel hp to the tires and this isn't normal for the vehicle in question - something is probably up with the dyno being used...

[Jason B]

I've suspected one guy of using the Vehicle Mathematical Profile to alter the numbers. This was on a "dyno day" that my friend payed for. And a new shop.
This guy was just a dyno operator, he said I couldn't have hptuners connected while it runs on the dyno. I'm pretty sure he had no access to calibrate the pcm.
Of everyone there I talked to the guy the most, he either didn't know what he was doing or was screwing with vehicle profiles. It was a mustang dyno.

My friends car put down 270 hp, I had almost the same exact car and put down 333 hp.
Later the same day we ran down the track side by side. He ran 11.8, I ran 12.2

[GHuggins]

Usually if your using the wrong vehicle and especially a vehicle with more resistance via the eddy brake it will get lower numbers than it should, so I can see that causing low numbers on your friends car. The brake itself for turbocharged vehicles is what I was referring to in my earlier post...

Yes an unskilled or unknowledgeable operator can lead to engine/trans failure or incorrect numbers. One local operator was putting a constant heavy load to one guys diesel truck resulting in something like he was pulling a loaded gooseneck on a mustang dyno and smoked his transmission...

[tris909]

on a few IRS cars i have seen strapped down to hard causing on 3kw or more so not much to be worthy. Your dyno load inertia can be changed also to alter results, either manually or through "shootout" mode.

[GHuggins]

I just load the vehicle profiles that I'm supposed to be using with that vehicle - lower hp cars I don't even run a load as the drum is enough... Never heard of this "shootout" mode - I use a dynojet small drum awd dyno - something I should be aware of?

[tris909]

Shootout mode is used on dyno dynamics dyno, has pre-loaded inertia and load settings as well as different ramp rates for each vehicle configuration. We only have a 2wd single retarder set-up dyno.

[Area47]

i see it about once or twice a week. when your car weighs 3800 lbs and the roller weighs 2600 lbs, you get away with a lot more in "numbers" I use an eddy current dyno with all of the toys. It is also known as a dream killer in the ego world. I have seen correction factors messed with, which changes the numbers substantially. there is a bunch of little things to look at. most of the time the graph shows the whole story.

[07GTS]

i see so many runs and the graph shows the hp/torque crossover and different rpm points if its set up right shouldnt it always be a 5252 rpm..? looking at mine its about 5000rpm so close but some are in the low 4k area does this mean the torque calculation is off or something

[Hutchinson]

Good question 07GTS, I was wondering this myself. Be interested to see the response on this one. I always thought (from my past research), the HP/TQ curves should cross at approx 5252rpm.

I had my truck dyno tuned a few months back,.....my dyno tuner didn't want to make the pulls in 3rd (he feared damaging the K1500 truck driveshaft????? - which I thought was odd - but, I don't know any better),....
Thus, he made all pulls in 2nd gear - my lines crossed at ~4300rpm (yet, I know 2nd gear ratio is 1.62, as compared to 3rd's 1.00,....) thus, I'm not sure where my HP/TQ curves would have crossed running in 3rd.

[Area47]

Good question 07GTS, I was wondering this myself. Be interested to see the response on this one. I always thought (from my past research), the HP/TQ curves should cross at approx 5252rpm.

I had my truck dyno tuned a few months back,.....my dyno tuner didn't want to make the pulls in 3rd (he feared damaging the K1500 truck driveshaft????? - which I thought was odd - but, I don't know any better),....
Thus, he made all pulls in 2nd gear - my lines crossed at ~4300rpm (yet, I know 2nd gear ratio is 1.62, as compared to 3rd's 1.00,....) thus, I'm not sure where my HP/TQ curves would have crossed running in 3rd.

i do trucks all the time in second due to the chucking a driveshaft issue. been there, done that. If the charts are not foced, or scaled correctly, it will cross at different rpms. The cross point is in fact 5252 to follow the correct mathematical parameter.

[Hutchinson]

Cool Area47, good to hear it's a legit concern/common practice to make truck dyno pulls in 2nd (I didn't know any better bud). What multiplier would you tell your customers to adjust the (2nd gear pull) RWHP/RWTQ max numbers,...to reflect what the numbers should be if you did the pull in 3rd (4x4 truck)?

I.E. my 2nd gear dyno pulls produced max - 241.48 RWHP @ 4600rpm / 309.23 RWTQ @ 3600rpm - HP/TQ curves crossed at ~4300rpm.

The HT383e GMPP crate engine advertises - 323HP @ 4200rpm / 444TQ @ 3000rpm (at crank)

Thus, if I run the 2nd gear pull numbers as is (to find drivetrain loss from crank to rear wheels) - The drivetrain would be sucking up 26% HP and 31% TQ,....thus, I'd presume there should be a multiplier to get top HP/TQ #'s (since we did pull in 2nd instead of 3rd). Hope I'm making sense here and not confusing everyone.

Typical 4x4 drivetrain losses should be in the 17-20% range according to my research,....thus my 2nd gear dyno pull numbers are very low if there isn't a multiplier from 2nd to 3rd.

Thanks guys.

[Area47]

that is a very loaded question actually. Tire size, torque converter stall speed play huge into the final "dyno" numbers. Typically it could range from 30 hp difference to 50 hp difference. depending on the load, gearing and other factors.

You're turning a transmission, transfer case, u joints, pinion gear, ring gear, fluid, bearings, rotating mass of the wheels and tires, and the brakes themselves. each of these do in fact take power to turn.

[01ssreda4]

Did he make changes to the VE at all?