Well is there anything I should know before I go and dyno my 2004 XJR? Basically Im about to start my list of modifications and want to get a baseline.

I dont need advice on correction factors or anything like that.

What I need to know is

1) What gear to dyno car in
2) Sport mode? Traction control? What setting Im figuring sport mode with traction off


Now before I go get this dont I do have a few questions maybe someone can comment on. I have no check engine lights and car runs smooth as silk. Sometimes however (and not outdoor temperature dependent) performance seems reduced at times. Now perhaps im imagining this but I dont think so.....Anyways I read that sometimes there is an issue with the air flap in teh box sticking closed. Could that be a culprit? Should I maybe remove that before testing?

Thanks in advance all:O)

Damon

 

The main thing about a dyno is to reuse the same one when doing later dynos. Also, to realise that they do not give exact numbers i.e. are not repeatable. Three dynos of the same car, unchanged, over a period of time will not be the exact same values (but should be fairly close).

I've seen various posts recommending traction off and sport mode on. I don't really see it matters much so long as you do it the same when you've done mods as you're trying to see how much difference, if any, the mods make.

The air flap if faulty can just be fixed (it's a solenoid that pulls it open) and would be glaringly obvious with a horrifically low max HP. I'd just dyno and see.

 

The typical gear on a dyno is whichever one get's you closest to a 1:1 gearing. In a 5 speed that is usually third or fourth.
Never dyno'd an automatic, but I'm sure the operator will know what to do (they run the car for you).
You might want to look up the gear ratios and you can tell him which gear is best....and as JagV8 said, you want to repeat with the same dyno/same gear if you can to measure any future changes if you so desire.

have fun, if you haven't done it, it's great to watch - might want to take some video for us then post the graph (make sure to ask for a printout; I've been to a few dyno days where the hung over young tech's couldn't be bothered to do a printout).

 

Its pretty hard they want to kick down all the time when they dynoed my XJR6 we did it in third gear couldn't get full throttle in 4th it would just kick down

 

Thanks Doc, sounds like third it is

I found these ratio's for a 2004, I assume Jag kept them the same in the ZF, so yes, fourth would be the most direct (closest to 1:1), but you do what you can do. They may be able to factor these things in now; been a few years since I've done a pull, software has probably evolved.


Gearbox:

ZF 6HP26

Transmission type:

automatic





Number of gears:

6

Gear ratios (overall):


I

4.171 (12.8)

II

2.34 (7.18)

III

1.521 (4.67)

IV

1.143 (3.51)

V

0.867 (2.66)

VI

0.691 (2.12)

 

Ive dynoed many cars and do my own tuning (SCT racer package, Moates QH and megasquirt III). With the Jag I'm just stuck withwhat I have. I was unsure of which gear to dyno in (1:1 ratio, downshift potential) and cant play with converter lockup or torque management. I just want to make sure I can get a usable number for comparison. I also dont want to waste time so I will just remove that dam flap. After this my exhaust wil get done. No cats, dynomax ultra X resonator, two dynomax ultraflow mufflers and some nice 4 inch slanded/rolled tips. Exhaust will be a full 2.5" SS mandrel bent. Ill then redyno. At that point Ill be adding a 6% blower pulley, 80mm Intake tube and my modified Mina Air intake. Also working on getting a properly calibrated Pro M meter of 85mm or so. AFTER all that another dyno.....Then bored TB/elbow....And thats it. I have no idea what gains to be expected but it should sound nic:O)..I have no expectations here. Nothing crazy but figured Id document the gains along the way

 

Hi Damon,

I will be watching your results with great interest. Just my two cents, but I would suggest leaving Traction Control off, as well as the HVAC system and anything else you can think of that is under control of an ECU rather than the driver and could introduce unnecessary variables into your results (and of course constant-load systems like the stereo, headlamps, etc.).

And if my math is correct, 5th gear, at 0.867, is 13.3% less than 1:1, while 4th gear at 1.143 is 14.3% greater than 1:1, so 5th may actually be closer to 1:1 by a narrow 1% margin.

Cheers,

Don

 

I'm not even concerned with initial dyno numbers but more about what the mods will accomplish. I dont believe thE exhaust will be too loud however I can always add CATS. Typically id improve the intake side first but I really wanted to see just how restrictive the exhaust may be on a stock xjr. I decieded to keep it at 2.5" and not go larger for fear of loosing low end torque. Many of the exhausts out there I believe comprimise performance for sound. The dynomax ultraflows in my past experience on particularly bad sounding engines (ford 3.8 v6) have totally mellowed out the exhaust note as well as resonation on even cammed high HP v6's with little loss in flow. I can imagine on this engine it will sound sweet. I'll post once dynoed and use that thread as a marker for all future performance upgrades and dyno testing. I know its not a race car but its way to quiet for me and my neighbors are starting to think I softened up.....Cant let that happen! If the dyno shop is open this weekend im going.

 

huh, my last post didn't make it up.

Anyway, here's a rewrite of the down and dirty:
*trac control off
*sport mode on
*per Don's math, just have the operator put it in 5th, and if it kicks down to 4th, that's fine (well, 1% fine
*try not to let it get heat soaked; car should be up to temp but don't leave it idling for a half hour or something
*if there is a line or something, and shorter than 20 minutes, keep it idling, if not, you can turn it off and pop the hood. Better to leave it idle with the hood shut.
W/A intercoolers are pretty notorious for heat soaking pretty quick

However you end up doing the dyno, just try to do the follow up pull the same way. The dyno will compensate for temp and humidity, but you want the car as close as you can get it.
Make sure they give you a printout, sometimes they don't unless you ask.

have fun and post the results!

 

Good luck trying to dyno the car in 5th, or even 4th for that matter. It will kick down. Redline in 4th is 150mph, do the runs in 3rd, like everyone else has in the past.

 

ah yes, seems it will...was trying a 'street dyno' in mine today getting on an empty on ramp; kicked down to third.

Oh well, repeatability is what you need.