I have had a couple of performance mods made to my 12 XK NA vert; they are a tune by ECU Tuning Group and a Mina exhaust system. I have gotten curious as to what these two mods have done to the car's hp and torque.

So today I went to HK Motorsports in Van Nuys, CA to have a dyno test run on my car. It was impossible to rev the car much beyond idle with out having the dsc kick in, even with the dsc turned off. Spoke to Jags at ECU and he said there is some kind of a bypass/method of side stepping the dsc; but, that a Jaguar computer or set of instructions is required to avoid the dsc. Is anybody able to give me some advice?

By the way, because the front wheels are not turning the computers in the car think that the vehicle is sliding and cuts power.

Any suggestions will be gladly received. Thanks.

 

Great questions and I hope folks can help. I really want to do what you are trying to accomplish. Thanks for putting it out there!!!

 

Hey Ralph, I'd be interested to see what your car pulls too. Others on this forum have had their XKR's and XKR-S's run on a dyno machine. I wonder what they have done to overcome your problem? Keep hitting that fuzzy ball down the line.

 

I think maybe pulling the fuse for the DSC module might do the trick after reading Hawaii's post on another thread. I'm going to speak to the guy who runs the dyno shop about it and see what he .

Thanks for the note DGL. Between chasing that fuzzy yellow ball, spending time with grandchildren and playing with the XK I have little time for much else.

 

I didn't have any issue or need to pull any fuses when my car was dyno'd at Eurocharged. We did have to clear some codes afterwards but that was about it.

Doing the pulls in 4th gear required paying attention with the throttle and flooring it just at the right RPM or the car would try to downshift to third.

Good luck!

 

Well, I finally got back to HK Motorsports in Van Nuys today. In order to run the dyno test on the xk, it is necessary to remove DSC pump fuse which is fuse 20 (40 amp) from the fuse box inside the engine compartment. Easily done.

Result: 329.45 bhp at the rear wheels. Jaguar, as other mfrs do, use bhp at the engine flywheel in their specifications and advertising. In the case of the 5.0L NA engine that is 375bhp. When the engine is attached to the drivetrain; tranny, drive-shaft, universal joint, etc. there is approximately a 20% hp drain.

So, when you get the rear wheels number you convert the results by adding the 20% back to the actual results and the flywheel horsepower on my 12 vert modified comes out to about 412 BHP at the flywheel which is about what I thought it would be.

Oh, the modifications are a re-tuned engine by ECU tuning group and A Mina exhaust system. In addition to the horsepower gain I have a better sounding exhaust and slightly better mpg. Overall, I am very pleased with the results.

 

I usually use this calculator. Just plug in the values and it gives you the est. numbers.

Wheel Horsepower to Crankshaft Horsepower Guestimator

 

Another rough rule of thumb method is to assess a 15% loss of power is crewed up by the delivery of the power through the drive train to the tar for modern automatic transmissions and differentials.


Accordingly, the formula is: dyno result / .85 = estimated crank power. Again, this is only an estimate. The more efficient the drive train delivery system the higher the denominator.

 

Will pulling #20 on a 2013 xkr rag allow it to be dyno'd My bf and I took my car to a shop and they ran into the same problem . Is this also located under the hood fuse box. THey wanted $350 for 3 runs. Too much or reasonable? Thanks

 

The place I go charges $100 for 3 pulls, but that is just data, no tuning or anything fancy.

$350 seems a bit much just for a simple dyno plot.

 

Charlie & Glenn - Thanks for the info. It is probably more accurate than the 20% that Harry at the dyno shop gave me, even though it brings the bhp down somewhat. Regarding the quote you got eurobabe, that seems high to me. My guy charged me $125 cash for three runs with no tuning. Look in your owner's manual on page 192 or thereabouts and you will find the fuse information.

 

The DSC pump fuse on an XKR is the same. i.e. #20 in the engine compartment

 

I think 15 % drivetrain loss on a front engine, rear wheel drive car is optimistic. A 911, with the engine right over the rear wheels, is in the 12-15% range. I would expect an XKR to be roughly 18% or so....

 

Find a shop with an all-wheel drive capable dyno. Just touch base with whoever's tuning GT-R's in your area...


Rich

 

My best guess would also be about 17%, and lower if the torque converter gets locked during a wot session (older MB and ZF boxes don't lock).

But that is for street and dynos with single large drums per wheel. Smaller dual drums cause more drag, so the fulle drivetrain loss gets higher.

So that makes it hard to just put 1 figure as drivetrain loss.

 

Dyno plots are fun and all, but they really are only useful for comparing before and after. There is so much sensitivity to air temp, humidity, the type of dyno and even how that dyno is maintained, that you really can't assume much of anything.

What I did was have a baseline run to see what the car was starting at and then back calculated the driveline loss ASSUMING the factory rated crank power was correct.

333 / 390 = 0.853 or 15% loss

This gives a sort of calibration for the dyno. Is it correct? There is no way to know, but 15% is reasonable, and it gave a reference point for future comparison.

After the mods, the car goes back to the same dyno on as similar a day as is possible and then the baseline data is used as the comparison.

454 / 0.853 = 532

 

Remember that many dynos can read VERY differently. Weather, humidity, temp and many other variable s come into play. Use it as a general frame if reference and not as a fact.

 

As people have said, calibrations vary from dyno to dyno. Dyno dynamics dynos are known as the "heartbreaker" because they often read much lower than others. Dyno jets are generally considered to be more optimistic. The only real way to get useful information from a dyno is to run before and after tests on the same dyno under the same environmental conditions, preferably not too many days apart as dyno calibrations can drift like anything else. Of course, you also need to drive your car in between to ensure it has had sufficient time to adapt to any changes you made.

As far as cost, I wouldn't pay over 150 for three pulls including an a/f sniffer. And that was for an awd dyno.

 

$350 is rediculous. Anything over 100 os absolutely price gouging - badly.

There are many shops in my area that are 50-75 for 3 pulls. If you schedule some sort of gathering then 50 for 3 should be a no brainer.

 

Most shops I have seen are 50-75 for a "dyno day" with a bunch of people and 100-150 for an individual 3 pull session. OP of this question, you are in the DC area, right? I would check other forums (particularly audi and BMW) as they schedule dyno days in that area at least twice a year and a wide variety of cars always show up.