Nope, don't have a before sheet. He gave me this and two pages of printed out numbers for HP/TQ @ RPM to go along with this dyno.

I asked him if he knew of an XKR-S dyno and he said he will see if he can find one. That is something I would love to see. Other wise, I would basically be buying a tune completely blind.

 

The first challenge is to compare one dyno manufacturer's results to that of another as they often vary widely. Dynojet dynos are considered to be generally the most comparable from one to another and are therefore the dyno of choice to measure power that can be compared to others. It's also essential to do a "baseline" dyno run to see what power you started with and a post tune dyno to see the relative improvement of any modifications.

A tuner will usually perform tuning on the dyno to see the effect of any adjustments at the time, so the dyno is an important tuning tool. In the case of downloading a new map into the ECU the car may need to be driven before the changes take effect, then back on the dyno to check the results...that's the case with the ETG remapping.

For these reasons we need to see the before and after dyno, and without
both you really don't know much. There is a technique that allows you to adjust results from two different types of dynos to make a general comparison of actual power outputs. When I do this it's clear to me that this car is actually producing much less power than BigCat09' and another I've seen.

It appears to be quite out of tune with torque falling as rpm rises, and this results in the peak hp being roughly equal to peak torque instead of hp being significantly higher. Part of the cause of the poor mid and high rpm results is the unacceptable air/fuel ratio, but there is likely other problems with this car or the tune.

That is what's apparent to me from this dyno, and more information may help better explain these results.

Bruce

 

Thanks for your input, I appreciate the advice. The main reason I wanted to see this dyno was to see if there was anything funny going on with the tcu. I am not sure if he is in the range where this would happen, but I don't see anything strange so far.

I understand everything you are saying, as this is not new to me. I spent many hours helping Vision Function perfect their SC kit for the Lotus Elise. That is one car that I went WAY overboard on. I consider it a lesson learned...lol.



Yes, the Jaxkr's tune is rich, but the main difference IMO is really just an illusion. For example, look at 6000 RPM; the ETG dyno appears to be just below 400 TQ and Jaxkr's is actually just above. They are not that different, but they appear to be because of the scale and the way the dynos look. ETG's looks more zoomed out to me, but I do see the x and y axis are actually similar scale...But ETG got on the gas sooner. EDIT: I also see if Jaxkr's tune had less TQ down low, it would almost appear almost as flat as ETG's, instead of decreasing down so much with RPM. But it appears he is starting at a significantly higher point than the ETG tune.

Also, consider that ETG's dyno is SAE and Jaxkr's is Standard correction. I don't know how much of a difference that actually makes in this case.

Lastly, peak TQ is only higher in Jaxkr's tune because he has more TQ at ~3600 RPM where ETG's peak is at ~3250. If his tune was leaner at the top, there would be no doubt his HP would be higher and there would be a better HP/TQ ratio. But on these cars they have a pretty close ratio anyway. I would like to see Jaxkr's tune leaned out on high-mid to top and see what it looks like then.

Anywho!...None of this really matters to me as I just wanted to see the TQ and find out if the tcu is pulling power. I have an XKR-S and this is not the tune I would need (although I'm sure it would be very similar), but I hope this information is helpful to someone.

I am very interested to see a stock or modified XKR-S tune. Looks like I might have to do it myself if nothing shows up soon.

 

I would suggest both cars would have had near identical torque between 3000-3500 rpm (which we would see if the pulls started at the same rpm) and the difference in numbers is purely the difference in the two dyno types, calibration and correction factors. A before and after dyno would also show this to be the case. Once you account for dyno differences by putting them at the same values on the same y scale at 3500 rpm you'll see tq at 6000 falls way short of 400 in your example. The falling torque curve also supports that view when AFR is considered (ie no way could it be making more torque at 6000 rpm when its running pig rich). And we can't tell if the TCU would have restricted torque because the bad tune beat it to it.

I'm hoping a "before" dyno and some useful info will be offered to accompany this tuned dyno. Even then it is of little value because airfuel ratios are so far off, but it would at least prove that the two dynos record stock engines very differently. Not sure if it's just me, but the scale and info on that dyno is almost impossible to read.

Bruce

 

I emailed back and forth today with Jags. He is going to try to get me an XKR-S dyno sheet. He said one of his clients in Puerto Rico got ~627 HP in the XKR-S and their XKR test car was able to get ~620 HP.

If he comes through I will post the results here. He said it might take a bit since they are closing for 10 days soon, I guess for vacation time.

 

7 hp difference? I would think the XKR-S exhaust alone would be worth more than that (assuming like testing conditions).

I suppose he is figuring a 20% drivetrain loss and adjusting the numbers up from a wheel dyno? Engine dynos aren't super common....

Still, those numbers, if accurate and achieved safely, are worth 2 grand in my book.