Today it was finally time to get the snout ready for the smaller upper pulley. A friend of mine knows a guy who runs a small old-school mechanical workshop, so I went there with the supercharger snout. Easy job for this lathe-master:


The result:

 

Mr. Higgins,

How much smaller is the "NEW" smaller Pulley than the Original one? and What would the new Ratio be?
#1. If you continue using the original "Stock" Crankshaft Pulley
compared to:
#2. If you replaced the original Crankshaft Pulley with a Larger one?

#3. What is the size of the "NEW" upper Pulley compared to the Regular Stock Upper Pulley?

#4. In other words, How many more RPM's will the new Pulley spin the S/C?

My point is "How much Power are you leaving behind by not changing out the Lower Pulley, also?

Billy Clyde @ Cinco Ranch

 

Mr Price,

as I wrote earlier in this thread the smaller upper pulley is 10% smaller than the stock one. That will give 10% higher rpm in the SC as well. The size of the pulley is rougly (or maybe precise) 2 5/8 inches (66.6 mm) from what I can measure with a slightly to small caliper.

The lower pulley is OEM on my car as far as I know, but I haven't measured it

Regards,
Higgins

 

Many people believe that a 10% increase in SC rotor rpm is overspinning the Eaton which would decrease power.

Increasing that with a smaller lower pulley would add to that overspinning by quite a bit.

My car is 2005, so different Eaton, and I have the 10% smaller pulley and would note that the mid range punch is pretty darned good and since I do not go full revs frequently the mid range boost is welcome.

 

Thats about how I reason with myself. I don't plan to spin the SC any faster after this mod but never say never.. A bigger and more modern SC would be the ideal next step instead but of course it comes with a huge investment as well

 

It pays to do the math of this. There are several factory supercharged vehicles which come stock with much higher Eaton spin rates than our cars do, notably the Ford Lightning Pickup. Bumping up the supercharger rpm by even 15% is still going to be less than the maximum effective rpm.

The Jaguars are “gentlemen” cars by comparison and the factory engineers design them with that reputation in mind. Low stress all the way.

just check with our Houston friend if you think supercharger rpm increases are making his car less powerful.

Z

 

There is so much evidence to the contrary if you do the research. There is a reason why its nicknamed the "Heaton".

 

you do the research ! You’ll find several applications of the very same Eaton unit l, ex: Ford Lightning pickup, that spin the supercharger far more (higher) than the XKR.

when our Houston friend bcprice36 says he’s down on power after increasing the blower rpm, I’ll eat crow, until then ....

.....and by the way, Merry Christmas to all and here’s hoping for a better year to come.

Z

 

IF what you are claiming is true then why bother going to a twin screw set up?

 

before I go any farther, I’m busy cooking dinner and can’t hold your hand any longer. Put on your big boy pants and open your mind to someone speaking from experience.

I owned my first supercharged V-8 in 1969 , how many years supercharging experience do you have ?
.... or are we talking about just knowing how to type out google.com ?

If you can’t believe me, how about “Car & Driver” ?
I know they are just a shill for their advertisers, but in this case, they just might have the facts straight.

At 5,000 rpm the Ford Lightning is spinning the supercharger 1,000 more than the XKR at the same rpm. There, I’m done, and so is dinner.

bon appétit


https://www.caranddriver.com/reviews...xkr-road-test/

”....As in every other factory-supercharged automotive powerplant sold here, the device doing the work is a belt-driven Eaton Roots-style blower. In the 370-hp, 4.0-liter DOHC AJ V-8's case, it's the same 112-cubic-inch Eaton that Ford uses on its other supercharged V-8, the 360-hp, 5.4-liter SOHC V-8 found in the SVT F-150 Lightning pickup. On the Lightning's long-stroke, two-valve engine (which redlines at a mere 5250 rpm), the M112 supercharger spins at 2.1-times engine speed and peaks at eight pounds of boost. Atop the relatively short-stroke four-valve AJ V-8 (which spins to 6200 rpm before a fuel cutout turns off the fun), the blower turns at 1.9-times engine speed and huffs out 11.6 pounds. The relatively low supercharger drive ratio, says Jaguar, "enhances the refinement and reliability of the supercharger installation." That, and the fact that the blower nestles under its intercoolers, also means it runs more quietly compared with the same unit's operation in the Lightning......”

 

@zray
I see that you don't take the vacuum on the intake and pressure on the outlet into the equation. That determines most of he power consumption for the roots Eaton one, hence it doesn't make sense to compare just the rpm of the unit on different setups. Have a look at the performance graphs of superchargers, although the roots suffers most here, you see it clearly as well for the TVS series and less with the Twin-Screw types with internal compression.

bon appétit as well!

 

[QUOTE=zray;2329627] facts straight.

At 5,000 rpm the Ford Lightning is spinning the supercharger 1,000 more than the XKR at the same rpm. There, I’m done, and so is dinner.

bon appétit

You might want to first get your math corrected above . As you claim the Sc is spinning at 5,000 x 1,000 rpm which of course is total rubbish.

With the heat developed after several hard runs the anti knock retard will reduce power significantly even on a stock Heaton let alone an overspinning one

That is why I have done a lot of work myself to reduce that effect.

 

I’m all for the Twin Screw arrangement, however, the stock unit on the XKR’s is not being “over-spun”, even with the small(er) pulleys many have installed. The proof is in the pudding as the saying goes.

Naysaying doesn’t change the evidence.

Nevertheless, hope you and yours have a swell holiday season and look forward to the many pleasurable driving milestones that await us all.


Z

 

Technically you can spin the unit as fast as you want, "over-spun" depends on what you want to achieve.
A 10% overdrive does give you the feeling of more power as the torque is easier to feel low end, but top end the difference is smaller. Once you want consistent power over the full range and also for consecutive power runs, you have to combat the increased heat, if not at some point you will start to loose power as the ECU will pull timing to protect the engine.

Proof is in the pudding as you say, when I just had a lower larger pulley and the Eaton, it showed when I did a power run form 2nd gear to the 4th, the max power lowered in the 4th compared to 3rd, where normally in 4th you get the most power due to the 1to1 gearing of the gearbox. That actually got me started to develop something....

Anyway, Bprice3 could prove that as well with a dyno, though I have no doubt that he experiences very clearly loads of torque early in the RPM range, it will defiantly not be the same top end, and will suffer with consecutive power runs due to the excessive heat buildup,

So nothing wrong with a 10% pulley as long as you have the right belt to avoid slippage, don't mind the extra noise (some love it), and don't want more power in the full rpm range and consecutive runs.

Also the best wishes for the coming period, it will not be easy for all under these special conditions, so take care, and better times will come again!

 

In the case of a stock XKR, a 10% increase in blower rpm is so mild, it will not diminish the power at the top of the rpm range one tiny bit. The proof is
in the numbers of people who have made that modification without any reduction in top rpm power,

none.

I don’t believe it’s fully appreciated how mild the XKR / Eaton combination actually is.

as far as the ECU pulling timing, it’s already doing that at high rpm / high loads regardless of the boost level and independent of input from the knock sensors.

Having a 1:1 gearing in 4th has nothing, repeat nothing to do with acceleration or power or whatever you feel was lacking. The rear end gear ratio is too high, (numerically low), in these cars for flat out performance effectiveness given the weight and power, ie horsepower per pound It’s designed that way in order r to have better mpg numbers.

if you want better 4th gear performance, then
a). toss out a thousand pounds of the cars “fluff” and
b) install a performance ratio in the rear end

and the power you think the higher spinning Eaton lost will be back like magic,

End of story.


Z

PS. does a higher spinning supercharger make
more heat ? Of course it does. A good
mechanic / tuner knows a myriad of ways to shed the heat and keep the power.

in the late 1960’s my ball drive Paxton superchargers had an impeller rpm of 39,000 at the red line. Yes, Thirty nine thousand rpm. You think today’s low spinning eatons are difficult to manage ?

Ha.

 

Incorrect, the ECU is pulling additional timing based on your IAT2, easily another 4 degrees, and then on top of that you still have have knock control.
Incorrect, its a fact that the closer you are to 1to1 gearing results in the least losses, hence the highest power output in 4th, any dyno man can tell you that. Even if you don't want to believe that, my point was that power dropped with the Eaton and larger lower pulley (iirc about 16% faster spinning) when doing a longer dyno run, where I normally have in 4th the highest numbers.
Here is a dyno (at least one I could find) where you can see me going thru the gears, and the drop off in 4th. Not sure why we broke off in 4th for the red one though, to long ago.


This irrelevant to what I was telling, but indeed if one wants more feeling of power without increasing engine performance in higher gears, this is the way t go..

Nothing new, and for sustainable upper power I agree that is the way to go. For example, I've done a larger surface area IC radiator (not to thick to still allow a good airflow), better IC pump, water/meth spray and last but not least a SC that produces less heat in the 1st place ;-).
A bit less known but not less important, I have also put the later 2005 bumper on the car as that improves the airflow over the radiators. and replaced the inner bumper beam with a smaller one as that one is actually blocking a big part of the direct airflow (especially if you buy an IC radiator that is way thicker).

How come you think you can just compare rpm with totally different units and the effect on efficiency beats me, though by that analogy, just 39.000 is rubishly low, turbos run 100.000 rpm and (way) higher, Ha. ;-), give it a go have a look at efficiency maps that will show it.

Spinning the Eaton 10% faster isn't that much more and probably gives the best bang for the buck as you feel the low end power come in earlier, but heat is certainly your enemy which raises quickly once you start increasing the pressure and that reduces the gains pending on how you use the power.

 

Heat is always an issue when adding power.

Throwing up your hands and giving up on adding power just so you won’t have the heat issue to deal with seems silly. There are several strategies to mitigate the extra heat and be able to keep all the extra power created by increasing the supercharger rpm by a moderate amount.

No amount of “you’re wrong and I’m right” is going to enlighten anyone.

Wishing you and yours a meaningful & peaceful holiday season.


​​​​​​​Z

 

Agree, but I fail to see who is giving up here on this thread, so not sure who you are referring to.
Its not about right or wrong for me, its about facts and misinformation, people can do with that what they want.

So much so now on heat, but if anyone has more questions, just shoot.

@Higgins
The next steps should really be work on the intake, by pulling more air you also increase the vacuum in the intake which was already stock under designed leaving a lot of power untouched. A larger filter/maf piping and now also the 83mm TB available you have some good extra power to gain, easily above 20 horses. Small note, as you raise the pressure again with the intake work (due to more airflow), it becomes again more important to work on cooling to get and keep the best results.

 

Looking at what Avos has achieved over the years and posted about in this Forum it is no wonder he is one of the most respected posters in this Forum.

He always backs up everything with facts, not conjector, or vague references/claims, or apples to oranges comparisons.

I have followed his advice quite a bit over the years.

As for the heat issue I have addressed that with an additional heat exchanger in line with the original with two puller fans in front. An upgraded Bosch SC pump and a water/meth progressive injection system.

Not much good getting extra power if you can not put it down so I installed a Quaiffe LSD.

 

Thanks for the kind words, and I try my best to share what I know.

I couldn't agree more about the LSD, that gives also so much more confidence in driving, and although I personally prefer clutch type ones, the Quaife is certainly a great improvement. Have driven in every condition you can imagine, and once it becomes slippery you really do need one.