I've been asked what and how I would modify my XJR. It's true that since I've bought it alot of my thoughts are what I would do to improve it. Its detracting from my 1970 6 speed manual aluminium Hemi Dodge Challenger project-which it mustn't...but in time...
I pulled out some old notes and collected some thoughts and this is what I've come up with:

When I was in Whitley I was involved in the XK180 and a project called the XKR plus (manual transmission). I learned alot from those projects and have evolved my thinking:
1) I would like an engine that revs to about 6750-7000 rpm. The problem is that with the 85 bar peak cylinder pressure loading of the AJV8 SC the max safe rev limit is about 6300 rpm.
The AJ34 torsional vibration damper just about meets the requirement of 0.2deg peak crank-nose amplitude at the 2nd resonance, normally between 5500 and 6000rpm. Beyond 6150 the softest damper from the existing tolerance range shows the amplitude reaching a valley at 6100 meaning this would start to rise again in the region 6100 -7000rpm thus producing a 3rd resonance in the (new) potential speed range. This is the sort of problem that could cause crankshaft failure .
If the moment of inertia of the flywheel is significantly lower (hopefully) then this can reduce the crank-nose vibration. The 6hp SC transmission has a torque converter moment of inertia of 0.232kg.m^2 whereas the NA is 0.16. Unfortuntaley I don't know what the MOI is for the older Mercedes 5 speed transmission TQ! NA value is the right direction from the perspective of crankshaft TVs. I hope the Mercedes Transmission TQ has a lower MOI.
A stiffer crankshaft can be used- which will raise the torsional frequency thus allowing a greater rev range. The AJ27 crankshaft is already stiffer than the AJ33 (thicker 56mm con rod journals vs 53 mm and a shorter 86mm stroke). Alternatively if the FORGED 8 counter weight crank from the Aston AJ37 could be sourced...this would help.

2) Increased Engine capacity: I would like to use darton sleeve liners and take the bore out to 92-93 mms like the NA racing AJV8s I was involved with however...
Head bolt cover ratio is already below the normal guideline and increasing bore or cylinder pressure worsens this (potential head gasket issues).I'm wondering if I could contact Cometic for a specially constructed gasket that may alleviate these potential issues on such a tight bridge distance (target bore= 92-93mm, bore centres are 98mm).

3)AJ37 Aston forged 8 CW crank has a 91mm stroke which would be nice.

4)Ports: I feel sure that with my fully flow bench developed machine port profiles I'll be able to achieve flow coefficients in the 0.68-0.72 region ( at 0.35 L/D) with reasonable tumble characteristics (current AJ27 is 0.55 - 0.58). Possibly look into going to 36mm inlet valves (for enhanced low lift flow) and 31 mm exhausts. If I use the AJ33 heads as a base I’ll machine the nasty shrouding squish and model it more on the BMW M cylinder heads. The AJ27 heads have quiescent ‘open’ chambers.

5) TVS1900 or TVS 2300 Eaton Rootes blower for good fuel economy, throttle response/ power compromise. The TVS series peak isentropic compressor efficiency has gone from 55% (M112) to almost 70%

6) Individual throttle body per cylinder: The AJV8 shares its 98 mm bore centre with its main rival the BMW M62. The S62 M5 engine has individual port throttles. These could easily be adapted to the AJV8. I've played around with ITBs on NA engines to great effect, but never on a boosted engine. Are the benefits still there? A collegue at Porsche doesnt reccommend using ITBs on boosted engines. Why? Needs to be investigated!

7)Redesigned camshafts: The current Aj27 cams have way too high a ramp- at 0.45mms. I will design cams with 0.32 to 0.36 mm ramps as used on the later Land Rovers. In addition it was always policy to minimise overlap on the SC engines to minimise HC emissions. This is an OEM EPA requirement that doesnt really apply to us hot rodders. Will ITBs help this issue? It's obvious to me from my work that the SC engines can benefit from increased exhuast blow down period (as I implemented on the AJ133) so I will look into this.

8) Using VVT on the SC engine: I quite fancy doing a mild form of Miller cycle engine with a high compression ratio and an over expanded expansion stroke for high part load efficiency. Perhaps VVT, ITBs and the TVS blower (much more efficienct than the M112 at high pressure ratios) will allow this without going into knock. I like the idea of high power and torque but with outstanding part load efficiency. Target 10:1 CR with a late intake valve closing at WOT to minimise knocking tendencies

9) In the current SC engine layout cylinders 7 and 8 suffer BADLY in terms of charge robbing. Theyre running about 20% less Volumetric efficiency than the others. This needs to be addressed! I would do this by doing a bespoke exhaust header design and looking at intercooler connectivity opportunities
10) Bigger intercooler radiator-probably from Eurotoys with higher capacity pump or may be the Johnson CM30 intercooler pump
11) New pulley ratio: stock Aj27 is 2.08, AJ33 is 2.1. I’ve played up to 2.2 but the limiting factor is high intake manifold depression. If I can get this down by 50 mbars from the AJ33 norm of 140 mbars (at 1300 kg/hr) then I could look into a higher pulley ratio. TVS blower peak speed is now 18000 not 14000 rpm. I dont know how physically easy it is to get the intake losses lower than 100 mbars when I'm looking to get between 550-600 bhp. Is it possible to go speed density engine management on a boosted engine?


12) stock Aj27 back pressure is 750 mbar, AJ33 is about 850 mbar. I think because noise constraints are less I could target about 400-500 mbar!

All of the above should make a powerful, torquey powerplant still with reasonable fuel economy. Especially if I can get good incylinder tumble and go for part load lean burn.

 

Toyota Supra 7MGTE motors always have problems with the factory gasket because of the as manufactured torque values. It is so common that potential buyers ask about the head as much as Jaguar shoppers ask about the tensioners. The usual solution for modified engines is a copper shim headgasket from HKS or Greddy. Once installed on a properly prepped head and block surface the engine is solid.

Could you help with the following please?

https://www.jaguarforums.com/forum/j...er-tees-52504/

 

Good post, thanks for this information, am certainly looking forward to what you can achieve!

Some comments/questions
1 Has also played in my head to raise the rpm as the only reason the power curve stopping now is due to the limiter. I guess also the injectors need to be changed to allow more fuel in a shorter time, but this shouldn't be the hardest if needed. Have no idea about resonance obviously. I have been looking for a long time for someone that can adjust he TCM, as that one would also need to be changed for the higher revs. And there is even some more time to be gained by changing the shifting strategy (my plan is to use stock values for the normal mode, and the special faster settings for the Sport mode), but so far I just can't find anyone that can do this, would you know?

2 Rocketsports also uses the cometic gaskets (iirc in their 650 bhp na engine), so they may have something already. Am sure they can/will make a custom version, as they also do for the 4.0 gaskets where they make a thicker MLS version.

3 Any idea what such a crank would cost? So far I have only seen from 1 company for a custom forged crankshaft, but that goes already into the 1.750 GBP (without VAT).

7 Do you have any idea how much HP could be gained here top end? I still have a set of RR heads/cams lying around, but never took the time to put these on as I wasn’t sure if these would gain in top end

8 The TVS and TS certainly could have an advantage here, but this was out of my reach to play with.

9 That’s a bad loss worth addressing, would be looking forward to what you could make, and also if that could be done on the XKR regarding space

10 I think that unit is way too thick (at least for the XKR), and will cost you efficiency due to the reduced airflow. But I don’t know how much room you have to increase the frontal area in the XJR, and still keep it thin enough so you can get good airflow thru your intercooler radiator and also still enough for the units behind that one. The CM30 pump seems to be pumping the same as the Bosch units available at 3 psi. Maybe better to put 2 Bosch pumps in parallel, that will not yield double of course, but more than a single one. I use a heavy duty commercial pump now, which yields about 30-40% more flow then the stock hella one at similar pressure.

11 Full new intake is needed anyhow when going to the TVS (just like with the KB), so better to drop the current one with too many bends/small diameter and go to a larger diameter system (with at least 2 bends less).

Success, looks like really nice project!

 

Wow. Sorry for the lame question about TVS vs Twin Screw on the other post. You are truly an educated mechanical engineer. I am in awe of your knowledge. I need to re-read your post a few times to let it soak in.

BTW, there are a number of companies in the US that make custom crankshafts. I don't know if the limited Jaguar market would be cost effective for them to make a forging, but if budget permits, you can get one turned from billet stock..I guess you know that.

 

avos: "7 Do you have any idea how much HP could be gained here top end? I still have a set of RR heads/cams lying around, but never took the time to put these on as I wasn’t sure if these would gain in top end"
I've forgotten, I'd have to revisit my simulation/calculations and cross correlate it with archive data I have. I dont have time right now. Im in the middle of a move from California to Chicago and when I get there my first car priority is getting my Challenger back up and running!

"3 Any idea what such a crank would cost? So far I have only seen from 1 company for a custom forged crankshaft, but that goes already into the 1.750 GBP (without VAT)."
1750 GBP is rather cheap. Are you sure? When Farndon engineering used to make one off cranks for prototype engines for us they used to cost us about 2500 GBP over 10 years ago.

Hi Fla Steve- thanks for the kind words! I wasn't expecting the Jaguar lot to be so interested in technical modifications! The Muscle car crowd are but when you get too deeply analytical (Im currently trying to design my own set of cams for a 2nd gen 60s Chrysler Hemi engine) they shy away or even shrug you off. The Porsche crown seem to respect only those who have money and go to Ruf or get fast lap times at a race track rather than those who have engineering knowledge!
I know of the US crank manufacturers who do higher volume stuff for Chevys and Mopars obviously. I'll bet there is a huge mark up for the forged Aston Martin crankshaft unfortunately. That thing has 8 counterweights and is fully forged with a riffle drilling to relieve interbay breathing in the crankcase (useful for dry sump applications and high rpm).

 

The 1750 price was actually what I got from Farndon in 2009, if that is already considered cheap then this route might be out of my league. If more are interested and a group by could be made to soften the impact I might still join.

 

HI Count,, would be much simpler to put a Gen 111 Hemi, in the Jag, and probably faster too.

probably cheaper also, and be done with it!

 

I know the GEN 3 Hemi very well, as well as the Gen 2, I've put a Gen 3 ALL ALUMINIUM Hemi 7 litre into an old Cuda T/A. However I wouldn't put one into a Jaguar. Yeah, its faster and its simpler, but then why wouldnt I just get a Chrysler 300C or Dodge Charger in the first place? That's even faster and cheaper-esp when modified.

There's a subtle difference in "HOW Fast you can GO" and "HOW you go Fast"- alot of people stateside don't understand the difference between these phrases- hence you see totally unbalanced Porsches and Jags with cast iron Small block chevys in them and the owners thinking they can get 6K for these and thinking they've done something new.

 

Count,, i believe you said it yourself, how fast do you wanna go= how much money you wanna spend.

if that car you do in OP,it would cost way more than it would ever be worth.

modded cars usually dont get the money they cost!

in other words , you could say,an exercise futile engineering.

 

I believe you're completely missing the point. If I want to go fast cheaply I'll use my 1970 Challenger- it doesnt go around corners, isnt individual (because everyone either has one or wants one) has misfitting doors, terrible weight distribution, leaks oil even with Fel Pro gaskets, isnt refined, has panel gaps a gecko lizard could live in, and will give you a headache if you try to drive over 100 miles in it. You're NEVER going to be any kind of individual driving this. If you want cheaper power- get a Camaro and be just like everyone else- with a small block.
Any car modification hobby will cost you 'way more than it would ever be worth'- so why state the obvious?
Unless you're into numbers matching restorations of Hemis or XKEs.

If you want to be different however (or for someone who is incapable of understanding :"futile engineering") then you can go the route of me or Avos- and spend as much as your wallet can allow and do something DIFFERENT because its as much as a statement of individuality as it is going fast.
If the above is unintelligible and you repeat the same then I give up

 

count, OOPS, didnt mean to push some buttons(maybe i did,LOL).

i just thought it would be different to put a Gen3 hemi in a late model Jag.

i dont know your age, but i owned a NEW in 1964 Dodge Coronet RAMCHARGER 426hemi.

also bought new a 1969 Dodge Roadrunner 440 6-pack. i think i know something about them.

built many dragsters of the era. blown fuel cars ETC. till a divorce, stopped everything.
ya gotta smarten up someday!!

 

In my neck of the woods, putting a chizzler in anything is known as, 'Taking a dump in the engine compartment', but then I'm a Ford guy. My next project, (non Jag), now waiting for engine parts, will be powered by the hemi nemesis, otherwise known as the SOHC FE. But the only other possible engine for a Jag is a properly accoutered sbf.

KS

 

I think a great engine for a classic Mustang or Pontiac would most certainly be an old Porsche 928 engine- preferably with the 32 valve heads.
This engine has a bore centre of 122 mms so is of "big block" proportions.
It can accomodate two 39 mm intake valves, with a forged fully counterweighted crankshaft. 928 International do a longer throw crank and the engine can be bored to 7.6 litres. This is ample as this engine is capable of making good high end power combined with good solid BMEP throughout the rev range ( no super long cam ramps bleeding off low speed torque here due to pushrods)- so 9 litre plus of pushrod power isn't needed.
The engine can rev cleanly to 8000 rpm as the components are man enough to handle it. Unlike Ford Cammers or Hemis the engine actually breathes so the power doesnt fall off a cliff/and the engine can still idle. This would be cheaper than building up a trick Mopar 2nd gen Hemi
The engine is all aluminium and light however so lighter than typical cast iron small blocks by some margin.
However on a Ford or Chevy it would probably end up twisting the frame, shaking panels off of the chassis

 

That's why you use a tube chassis. And there are iterations of the SOHC FE that breathe to the tune of 500 CFM per cyl on the intake, NA. Then a pair of turbos about the size of your head, and Bob's your uncle!

KS

 

But , as your cohort keeps saying, then it gets expensive. So much for Cheap American Power...

 

Speed costs, how fast do you want to go?

KS

 

HEY guys? if you want to prove your cars performance bring it to the TEXAS MILE.

that little one 1 mile race can sure seperate facts from fiction!

its more smooth than Maxton mile, 10,000ft concrete.

and MANY guys go home with tail between legs, braggin before, and quiet after race.

then some Mexican kid shows up with a 1997 Chevy pickup(LS powered), and cracks the MAGIC 200mph , try and figure that out!!

full moons comin so lets not show our other side.

 

Depending on details, I'd be willing to bet that the cost for a Moldex billet crank would leave lunch money out of $4K. One thought to throw out regarding the crank's design is the ubiquity of rods and bearings designed to fit a 1.88 crank throw. And that it's quite easy to create a crankshaft with the nominal 2.25 main size of the 302 Ford. You slow down the surface speed and improve seriously on the availability of race-type bearings. Just a Thought!

KS

 

Regarding ITBs on boosted engines: has anyone ever seen such an engine, even if it`s a racing one? I don´t think I have, especially in a V cilynder configuration. I also don`t really know why, and would like to know. Off the top of my head, the 2 main problems would seem to be the difficulty in assuring no leaks of boost through the slide mechanisms, and the potentially greater (bad) effect of relative imbalance between different TBs: the imbalance is magnified by the amount of pressure over atmospheric, and could maybe result in increased vibrations and torsional forces at the crankshaft, especially during transients.

Regarding charge robbing in 7 and 8, a boosted engine with an overlong plenum chamber (ie, chamber quite a bit longer than strictly needed so that the end wall is not near the intakes for the last cylinders), with short intake runners (with or without ITBs...) and exhausts manifolds that are not too restrictive or imbalanced should minimize the issue, and are beneficial to a lot of other aspects...

Other than that, thank you for a very interesting post, and please do keep us all informed on your progress.

Daniel Fróis

 

Some years ago, I had a project running a set of DCOE Webers. The manifold had a balance tube cast in to minimize differences from one runner to another. Balancing 'draw' from one throat to the next with a vacuum gauge, and having the balance tube also, made things such that there simply wasn't any discernible problem.

KS