Yes, I have had some experience, in the past, with engines using two twin-choke carbs, and also with 4-cylinder bike engines using 4 independent carbs, and that is why I thought of depression imbalance as a potential problem. My gut feeling - totally unproven - is that what is a small imbalance in an atmospheric engine will be magnified in a boosted engine, since the absolute pressure difference will be much greater, all else being equal.

I have some good books on engines and turbo applications, and had thought of checking if there was something there on ITBs on turbos. Of course, I forgot...I`ll try to remember to check tonight, and hopefully report back tonight.

DF

 

seems you are right, there are not many,if any ITB turbo engines, only one i have seen was the Nissan RB26 twin turbo for the 90s Skylines.

also the Nissans that were highly moddified used a large single TB with large plenum, and a gigantic turbocharger. also go like hell! over 1000RWhp.

the best of the Toy. supras run single TB with big turb. they have cracked over 1500hp.

so something to it all,, its also what i use on a couple 4 cyl turbo motors, and a Mazda rotary RX7.

 

the large volume plenum is an important part of the equation, along with the runners!

 

ITBs are not used often with forced induction because they don't add horsepower (maybe a handful); only provide quicker throttle response. They're also a pain in the *** to set up properly.

 

Thanks for the interesting post, Count Iblis!

This year, I have had a T56 manual gearbox installed (see XKR manual in other post). Despite using a 2,1L KenneBell with +10% lower and 2½" upper pulley, you notice that the gearing is a bit higher than with the auto box. Maybe the torque converter is partly responsible for this - does it slip during acceleration, giving an apparent lower gear??

I guess the car doesn't NEED to be any faster but it's easy to become a performance junkie after some time (I mean real performance, not figures!). I was thinking of fitting a different crown wheel but as a first step, maybe a different ECU - one that would allow a higher rev limit (plus better tuning freedom). Looking at your notes, particularly point 1, a higher rev limit may be the best way do do some real damage. It seems as though you would not recommend raising the rev limit unless making other substantial (mechanical) changes. Is that the case?

Thanks
Mark

 

Increasing rpm should be done with care, but is certainly a way to add power if you don't have any other restrictions to support that.

But your particular setup can be improved a lot, as now you are basically choking the supercharger, which costs a lot of power. You will feel now that the engine picks up power quickly, but the higher you go in rpm (/power), the less gains you get because of the choking.

Attached are 2 pictures, one I made once on a car that had the same setup as you have, as you can see the SC intake is not used fully, roughly you are blocking about 30% by this.

The other one shows a 2.6 version I use now (that has a slightly larger intake then the 2.1), but that will show you roughly the difference, and here I use the full opening wihtout any sharp bends towards the SC.

So if you would redesign the intake elbow to make use of the larger intake you get lots of extra power. I had done this for my 1st conversions where I used the 2.1 TS and with that setup I already made 455 rwhp with a 2.5 upper pulley and stock lower. This is way cheaper than extra ECUs and less risky to the engine running much higher top rpm.

Just my 2 cents.

 

Thanks Avos

Actually, we have spoken about this before (I haven't forgotten this alternative). Let's explore this route, it sounds interesting! I am a bit tied up at the moment but will get back as soon as I can - maybe at the weekend.

Mark

 

WIllafizz


Your manual conversion car sounds very interesting.


Regarding revs-


i'm re-examining this again now- and digging into data I have.




The 90.3mm stroke crank (AJ33) with flywheel would not be durable at speeds much above 6000 rev/min due to flywheel whirl. This is forced by firing loads hence increasing speed or firing loads worsens this problem.


A forged Steel crank would raise natural frequency of this mode by around 10%. Frequency of torsional modes also increased.


86mm crank (like the AJ27) also raises frequency but increases firing loads by 7%.


56mm pins are possible with 86mm crank (as they are on the AJ26 and AJ27- the AJ33 has 53mm pins) , these increases flywheel whirl and torsional natural frequency and significantly reduces stress per unit bending.


Lighter flywheel helps raise natural frequency of whirl mode but going too far is likely to cause driveline refinement issues. What sort of flywheel did you use on your Manual Jaguar?
I'm guessing it's somewhat heavier than the standard automatic driveplate.


I would recommend changing the current old 56mm pin rod with a custom forged item (the AJV8 rods are sinter forged and cracked)


A fully forged 8 counterweight crankshaft like the AJ37 (Aston Martin V8) would be nice to try. Like the ones we've talked about possibly from Farndon engineering.

 

Love reading any of your Jaguar engine tech thoughts Count. I just stumbled across this post looking for something else. Did you ever finish your Hemi Charger? Did you start on your Jag?

Cheers,

Gary

[

 

Hi G. Gabriel,


I'm working on both.


It's a slow process.


Using the stronger 15 HU diff (from a V12) but fitting a Torsen T2-R slip unit and Dana 44- 30 spline internals is a bit of work.





Whats under the car now







Drawings for the re engineered stub shafts I'm having made





Drawings for the companion flange to mate up to the rubber jurid coupling.


It will be fabbed out of 4340 heat treated steel to 48 HRC hardness.


The Torsen T2-R has a torque biasing ratio of 1-4- so this should be ample. BMW used a Torsen T1 R on their Z3 M coupes and Ford have used them on their Mustangs- so it will be a good solid base.


For the CHallenger I'm building up a 'Low deck stroker'- based on a strong 400 block - the capacity will be a 470 cu in or a 7.7 litre. I have the crankshaft now and the forged Ross pistons and the Mopar Stage 6 cylinder heads. The heads are very trick and are based on the no longer available chapman style CNC'd heads. They are based on the Max Wedge architechture and flow an amazing amount for the small port volumes. Now I'm looking into lubrication modifications so that the engine will be able to rev to about 7300 rpm. I'm building this engine over the summer ready for engine dyno testing come fall. I'll most likely be using 6 pack carburation and designing my own cam. I'm right- now doing some iterations on the cam profile design for this engine downstairs

 

Hi Count,

How cool! Nothing sounds better that mutiple carbs. Thar ripping air sound is intoxicating. I can't even imagine how good a big V8 reving that high will sound with a 6 Pack.

I'm so glad to see you put a Torsen diff in and pave the way. I had one in a built up Road Master and it was easily my favorite diff of the different styles. I've had a TR2 (I think that's what they called) that took forever to get as Torsen builds for their racing teams first. It was years ago but I saved it hoping to put it in the right car. If you feel like sharing that process it would be quite a gift for everyone.

Can't wait to read more of your updates.

 

Yeah, I'm doing the high revving big block for he noise mainly. It will pose quite a challenge for a pushrod valvetrain and the dynamics. Not as easy as a direct acting system like our Jaguars.


I had real trouble getting the Torsen- their primary business is to the military and it is the most lucrative to them and as a result they don't priortise to aftermarket customers like us. I had to use my contacts and talk to the VP in NY.


I will be happy to share, much like yourself personal family issues/marriage issues have taken their toll on the progress of my projects

 

Count been there and done that ,divorce can really upset a persons life.
hang in ,usually its for the best, only time will tell.

 

Look what I picked up out west :








The ports of the AJ37 are better than both the AJ27 and AJ33 heads, they have more motion AND better flow.


It has a fully 8 counter weighted forged steel crankshaft (stock Jag is cast iron with 6 CW). May help mitigating the first mode on SC cars- if we were able to raise the rev limit.


The cams are 256 period duration with 11.1 mm lift. The lift was limited by the valve covers. Will provide a good base for further modification

 

Very nice to see some quality EYE-CANDY!

 

Hi guys
Regarding ITBs on boosted engines, particularly supercharged lumps, you actually want to make sure you don't over size the TB or use much snapper ITBs because otherwise you end up with a throttle that is an on off switch and you could struggle to get it off the line without laying giant 11's every time you breath on the throttle...

When you start doing this you start needing centrifugal clutches like dragsters because the throttle just becomes a digital button for idle speed or 100% power!

My understanding of the AJ26-28's has lead me to believe about an 80-90mm TB is optimum. After that it's a case of upgrading to a more efficient type or supercharger, improving charge temps (I have an idea using thermo-electric coolers that will weigh less than the stock set up and provide coolant at -40c instead of ambient temp) that should massively improve charge temps!

 

I admit I haven't done a calculation to say exactly how good or bad it would work, but I'm not sure that the additional power you get from the engine would benefit over the alternator load required to run it.

TECs are horribly energy inefficient, it takes a huge amount of current to generate that kind of difference in temperature and even though they can get very cold, the thermal resistance through them is pretty bad (they are basically insulators).

For an intercooler you also need something that is good at moving energy from one place to another, temperature is only half of the equation.

 

Count, we are almost neighbors and I sure would like to sit in your garage and split a six pack. Seems we have something in common, we can't leave good enough alone. Keep us updated and if you are ever passing through Wisconsin I'm a 1/4 mile off I-94 and I always have a cold one ready.

 

Sounds good!


I live quite near the WI border but travel alot

 

Count i'm very curious as to your plans with the AM V8.

New pistons to drop the compression and put the Jaguar supercharger gear on top?

What about the firing order? It's different to the Jaguar engines if i'm not mistaken...

I've often wondered what a hybrid Jag & AM supercharged AJV8 would be like, hope to find out one day...