Hi people im new to the platform and am interested in a Jag with the 4.2 S/C the one im looking at has an upgraded upper pulley, remap and dyno runs which were done around 5 years ago with proof.
(i have not mentioned the chassis as its more engine related than chassis specific)

Mustang dyno
Stock wheel: 310hp 314Ft-Lb
Remap wheel: 330hp 360 Ft-Lb

These numbers seem quite low to me considering the stock factory figures all those years back. Not sure if the engine or charger is knacked. Or if anything can be repair or replacement or is this the power out of a 16 year old 4.2 S/C

Id like to know the communities opinion on this

Cheers

 

MUSTANG dynos are called "Heartbreakers" for a reason; they always show lower power than a person expects. Also lower than the other dynos.
Dynoes? I dunno.

 

watching mustang vs dynojets vids now

 

@Rack Jussell Welcome to the Forum. You'll find lots of knowledgeable and helpful members here. But we need you to help us help you.

Below is your Public Profile, which is basically useless. I get it, I'm paranoid about privacy, too. But you can still create a signature that tells us where you are together with your current ride(s).



Read this:*New members - a MUST read if you have just signed up*

Have you seen and driven that 4.2L XKR you're interested in? What year is it, and how many miles/KM does it have, how many previous owners, and what service records do you have?

You're considering a car that's at least 15 years old and may need more work than it's worth.
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Hi Stuart. ill get on to the profile now.

Its an 08 with 106k miles on it only 2 owners. loads of service history. i am planning to take it on a test drive soon after seeing what the forum had to say about the engines power output

 

A normal usage engine should have little power drop with 100k miles. Change items could affect more drastically, such as injectors, plugs, coils and such. Add in normal items like air and fuel filters, that'd leave valve and ring wear to cause problems. Rings would be somewhat noticeable with a slight blue tinge to the exhaust smoke color, and valve seals would cause a puff of blue smoke on cold-start. Valve compression leaks are not obvious. Power-to-the-ground could be affected by tranny wear or burnt/worn fluid. Not a GDI so intake valve blockage shouldn't be a concern.

If there is no excess engine wear or non-maintained parts replacement, you should have 90% and more efficiency.

Oh! If the catalytic converters are original, those only have an expected life of eight years or 100,000 miles. Most last longer, but some die quicker and cause a LOT of problems.

 

Thanks @Cee Jay i will make sure to check if theres any blue tinge on start up if i go to view.

As for cats i think they have been replace with sport cats a while back (need to check with seller when they where installed) but the p0420 and 430 check codes are present. Not sure if this will affect the running of the engine as its the post cat sensors which monitor cat efficiency.

 

Be sure to check the suspension bushings. See:
https://www.jaguarforums.com/forum/x...cement-284665/

 

I have attached a dyno sheet from an STR. It is from 2009 so the car was not very old when they dynoed it. I don't think your far off?
Not my car so no details other than what's on the sheet. It has the stock run and then with a pulley. Very light line on the modified curve so hard to see.

The fact is your not going to get much out of the 4.2L SC engine. That old Heaton M112 has it limits and Jaguar designed this engine very well in stock form. The M112 blower was used because of how tough and long lasting it was. For an OEM installation this was WAY more important than getting another 25HP out of the engine.

If you want to go further I would concentrate on improving the charge cooling. Better IC and better pump. Maybe consider Meth injection which helps on multiple fronts? It increases octane of the fuel as well as providing massive cooling from the latent heat of vaporization as the Meth turns from liquid to a gas. Heck maybe even consider a Killer Chiller if you know what those are?

The upper pulley is also a problem as that requires a smaller pulley so your losing belt wrap and will increase the chances of belt slip. Another problem with the 4.2L engine is very limited space for increasing the diameter of the lower pulley. This is really what you want to do as the larger pulley increases belt wrap and reduces belt slippage.

Don't know if your aware of pressure maps? But that tells the tale on increasing boost on the M112. Note this is the 5th generation of the M112 and the best. You did not tell us the year of your car but you probably do have the latest 5th generation blower.





The smaller pulley pushes you out of the high efficiency rings on the chart. So now your in the downward spiral of the M112. The faster you turn it the more heat it makes further reducing power. The factory was very careful to design it so you landed in the center of the efficiency map. Which you will notice is a terrible 62% efficiency. Now you can really see why everyone went to the TVS style blowers. Their efficacy is just way higher than the older designs.

Here is a map of the very nice TVS1900 we have on the later 5.0L SC engines. It's hard to read but the sweet spot is now 75% efficiency! But both blowers hit peak efficiency at around a 1.5-1.6 pressure ratio. More boost is not always the answer to making more power.





Now the expert on 4.2L SC Blower conversions was Avos and I hope he will read this and respond? But the solution is what he did and that was to install a twin screw blower. He made a few kits and I was very interested in installing one but the cost was in the $5K+ range and that's a lot to spend on car not worth much! But that quickly died out because of the price. I think he might have sold 1 or 2 kits if that. Now he did have a claimed 700HP 4.2L SC engine and that was pretty amazing!

I worked a bit with Avos when he designed the STR kit as he had an XK like you. The packaging was a bit different and I made some under hood measurements for him as I was extremely interested at that time on installing a twin screw. But in the end I kept my 2005 STR mostly stock and only swapped out the rear boxes (Mufflers). For me it was too much money for the power increase.

We have had a few guys use Nitrous injection. Not for me but it does work.

Also note the number one draw back of the STR is that open rear diff! A real bad decision by Ford/Jaguar to drop the LSD. We have a story on why they did that but note that when the new models came out after Ford sold Jaguar they ALL came with LSD! That E-Diff is a great bit of engineering and I love it.
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Thanks a bunch @clubairth1 really big insight in to the blower efficiency. The vehicle is a 2008 model so not sure which gen of blowers. i was also very interested in the STR but the J gate shifter without paddles is a no go for me. They also do sell LSD carriers for the STRs but at a hefty price. So i think im going to go down this route.

 

Since it's a ZF 6 speed it can use paddle shifters and Jaguar simply did not install them. It looks to be long gone now BUT Racing Green Jaguar apparently did make a kit back in 2017 but it was for the S-Type. That link is long dead so does not look to be available anymore?
S-Type Paddel Shifters

Yes we fought long and hard to get a LSD for the S-Type and found the 1st gen (Up to 2002) was much easier as it shared a common rear diff with the Lincoln LS. There is the Quaife which is a brilliant unit but as you said very expensive for what is now a cheap used car. The one for your XK is 985 GBP plus the install.
Quaife LSD

With a 2008 you definitely have the Gen 5 Eaton M112. That is the best version. You also have a very late model XKR so I think you also got VVT which was missing on the earlier 4.2L SC cars.
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WOW i did not know that paddle kits used to exist for S types. very impressive

I will have to grab that quaife at some point as open diffs are just no fun at all

Do you know if other cars like the 2008 XF SV8 would also have VVT?

 

Yes they should.
I had a 2005 S Type R and from what I know from 2006 on Jaguar added VVT to the 4.2L SC cars. The NA version had it all along. Not sure why they waited to do it but there was a small bump in HP from 390 to 420 on the STR. I think something about emissions was mentioned by Jaguar too. It was a small change and the 4.2 engine was on it's way out anyway by then. I only know about it because guys were replacing engines on the forum with used ones and this was a change to avoid. You can lock out the VVT's too but better to just replace a VVT engine with another VVT engine and the same with non-VVT engines.
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Amazing new @clubairth1 one other thing iv heard is when dynamic mode is selected on XF SV8s or 5.0 xks that TracDSC is engaged automatically.

Can you have Dynamic mode engaged along with S mode on rotary dial (for fully manual paddle control) and DSC fully off (holding button for more than 10 secs) for use when on track without the nannies for that lovely oversteer

TracDSC is cool and all but will kick in i presume if you oversteer too much.

 

I don't know as Jaguar changed that stuff around depending on year and model. Maybe someone who knows will jump in?
I know my XJR is NOT a burn out machine and it's hard to get much spin as it hooks so well with the E-Diff and the Michelin tires regardless of my settings.

Sorta wish it had some sort of launch control but there is no need really.
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