caddman wrote:

Dyno, schmyno. Find a stretch of road that can accomodate a 15-70 mph acceleration run in 2nd gear, start your logging, and let 'er rip!

I'd be curious to see the same data from runs done on a dyno as well.

 

lol, i will after work, im about to head out now....(you asked for dyno....)

 

I'm sick of English units. I just changed my MINI's OBC to Celcius and it's staying that way!

 

LOL, i can go either way, but metric is easier, i just used engish because that what the formulas were in, and ease of the "laymen" who read to understand, as well were using numbers and formulas from the same book, i wanted the ability to say turn to page XX, if the were to be a debate on formulas... im off to work now, post some good info by the time i get back!!!Its your turn..... :smile:

 

I wasn't venting at you about the units. More at Corky Bell.

 

I know i was just agreeing that metric is easier, and explaind why i kept them that way......

So did you check my numbers?....

I ll have to let the girls know you said hello tomorrow, i didnt get your post in time....

 

Here's some rough extrapolations I did with the Eaton-supplied graphs. Without actual testing, there is no way to know how accurate they are.





Here's the spreadsheet I used:

http://www.ross-tech.net/andy/mini/e...apolations.xls
_________________



SHOW ME THE NUMBERS! 1/4 Mile Database

 

It amazes me how everyone is so interested in boost but no one has considered the actual mechanics involved in attaining it. The shaft and bearings on the stock Eaton supercharger was originally designed for the stock pulley, along comes the 15% reduction, and we all (including myself) install them. Now everyone is going to 17% and 19%, How much do you think this SC unit will take? I have heard that with a 15% pulley that SC unit can spin up to 17000 RPMs. Also from what I understand, and I may be wrong, the water pump is hooked up in there. If you all notice, JCW replaces the stock SC unit and they are running less than 15%. That should tell us all something. There used to be a saying back in th 70's (and many of you will be able to relate) "They always GO before they BLOW". Keep that expression in mind the next time you BOLT on some extra horsepower w/o compensating for it in other ways
and that's my take
Craig

 

How do you know the Eaton supercharger was designed for the stock pulley? Have you heard this from Eaton directly? It seems pretty obvious that it was made for something for like the 15% reduction (or 14.5% of JCW) and that the S was "detuned". No auto manufacturer would exceed the limits of one of its parts b/c of warranty and reliability concerns. Yes that does tell us all something. The mechanics at MINI dealers aren't skilled or experienced enough to pull the old pulley off and install the new one. So the new pulley is added to the supercharger at the factory and then the dealer just has to swap superchargers. And if you want to argue that the supercharger for the JCW is different, it isn't - at least not from a reliability aspect. The JCW supercharger uses a different coating. But - even according to MINI and Mike Cooper himself - this coating is for sealing in the boost better - it is not for better reliability.

Now I'm not saying that the 19%, 17% or even the 15% is safe and will be without problems. I'm just saying it's not because of the reasons you mentioned above. :smile:

 

I agree Greatgro, the mp45 super charger is on how many factory cars, but yet it was designed for mini right, also the mP45 was out way before the mini was, we are talking years.....

Andy,
Im not sure about the graphs, i think was a good attempt, but the cfm one doesnt agree with the math, i provided you earlier(formulas by Corky's Supercharged!), Temps one im not sure i would have to check with the math, once again i provided, but there is variables that could explain it(not sure if Eaton is using the "standard" 90d day, after all who and why was that made standard?

 

ok i found the belt formulas!!

does anybody know the crankshaft pulley diameter?..I Dont, i guess ill have to do somemore searching!!!

anyways....

belt velocity=(crankshaft pulley dia*crankshaft rpm)/229=X ft/sec

drive power required by SC..

(boost*airflow)/229=x Hp

to find the 100% at the crankshaft, we must divide by belt eff(97% typ.)and adiabatic eff(60% typ)

X Hp/(.97*.6)= Y hp is actual hp the belt is required to carry..


now this formula kinda make sense with your graph.....

we must convert hp to ft/lbs per second,using conversion factor 1Hp=550ft/lbs per sec

Y hp*550(ft-lb/hp-sec)= z (ft-lb/sec)

then force= power/velocity

z(ft-lb/sec)/belt velocity(ft/sec)= ? lb

i hope the formulas make sense, if i didnt portray them correctly look on page 59-62 in Corky Bell's Supercharged!

 

According to my math,
the supercharger at 17.5lbs of boost and 371cfm is requiring 28.3hp at the supercharger, then add in the belt and adiabatic eff, brings it to 48.7hp at the crank, still have not found the crank pulley diameter to get belt velocity, to finish the formulas out....but that shows a big difference than the graphs 48.7 hp at the crank vs approx 125 hp on supercharger load(technically i shoud be using the 28.3 number because thats at the supercharger,the 48.7 hp is taking into effect of powerloss due to the belt stretching and adiabatic eff.)

 

OK ran out and measured, 6-3/8"=6.375"

(6.375*7500)/229=208.7 ft/sec

already did next step...48.7hp

48.7*550=26785(ft-lb/sec)

26785/208.7=128.3 lbs load on belt, thats close to the graph but its load on a belt vs drive power

 

Caddman,

I went over your CFM numbers and they look spot-on. I'll try to get some logging done with the 19% pulley so I have a baseline for both 15% and 19% in the current 0 C weather. Then, in the 30 C summer temps, I 'll do the same. I've done a little bit of logging on the dyno, but never recorded both IAT and MAP at the same time. Using the 15% pulley, with ambient temp about 28 C (82 F), intake temps went from about 33 C (92 F) at 2k RPM to 77 C (170 F) at 7k RPM. I'd attribute a large amount of that delta T to the amount of airflow provided by the dyno fans compared to to real world airflow on the road.

Did you get a chance to do any logging?

 

No not yet Sorry, its been raining here, a strong second gear would be impossible , to much wheel spin... Ill have to wait for a dry day, i did attempt it but, not kosher result due to wheelspin, and any higher gear would be to fast(i try to be a law biding citizen, contray to what people say about me, aka lead foot, maniac, etc, etc)

Beside i have been having fun number crunching....as you can tell...

 

Greatgro,
The whole point of my pontification was simply to question the reliability factor involved in "bolt on boost" . You guys have helped me out imensly in learning more about MCS's. I only pose the questions to fuel the fire so I can get more answers.
Thanks for your input,
Craig

 

Okay, here's a new spreadsheet with all of my logged data and calculated figures on it:

http://www.ross-tech.net/andy/mini/e...ulations02.xls

Here's my data plotted on top of Eaton's supplied data:





The equations used are:

airflow = cid x rpm x 0.5 Ev / 1728

drive power = boost x airflow / 229

belt velocity = crank pulley dia x crank rpm / 229

force = power x 550 / velocity

 

Got ya Craig.

 

That looks much better, except on the temp one, im not sure? is the eaton graph the change in temp and yours is the absolute temp? I just wanted to make sure im reading it correctly, also one minor thing one the airflow,

 

I just got a new Mini S. I've been reading this site to find out all I can.
I was wondering if you could explain how warmer ambient tempatures would increase the internal cylinder pressure. I would think that the colder air would be more dense and when heated would expand to a greater volume. And since the volume is finite the pressure would have to increase. I'm no motorguru, not even close. Not aruging your point or trying to flame you. Just curious for an explanation.

And for what it is worth, how does on start a new topic, or post a question or search the messages to see if the matter has been posted before?


REHUTCH
don't know if you are suppose to post your email or not.
rehutchinsonii
at
yahoo
dot
net

If not, I guess the moderator will remove it or delete my msg.
2004 Mini S, Electric Blue c sunroof. Tint, fuzzy dice, curb feelers.


>>I am going to have to go with JCW, AmD, and some of the other tuning companies who have invested a lot of R&D dollars, who have stated that 15% is the reliable limit on an engine with stock internals. When the heat goes up this summer and people are putting 18 lbs of boost on these engines, I think we will see problems. Even Randy doesn't recommend these.

 

First i want to touch a topic that you quoted from..."When the heat goes up this summer and people are putting 18 lbs of boost on these engines, I think we will see problems. Even Randy doesn't recommend these. " one Randy is not God, a very knowledgeable guy and not trying to knock him, so therefore he shouldnt be mentioned(but i feel he is wrong on the 19%, and funny that he is in a less harsh enviroment, that would make the 19% less stressfull on the engine due to altitude and heat, and less humidity)...two i and many others have been running 19% in the heat of summer with no problems, look at my post as well as BMP/Promini's website to see. I feel that I am probably in one of the worst area's as far heat(not saying im the worst, but close) Im at sea level(densest air) Southern Heat, 95+ degrees day on the regular, on the coast(100% humidity or close to on a reguar basis) now i have not had a single problem yet, 20,000 plus miles hard driven with the 19% pulley, I have done many install for people in FLA and AL, more heat than here still not a problem, but if you read this thread in its entirety(?) i and andy have discussed the heat issue, the heat is more important with these levels of boost, than the pressure increase due to heat, not saying that the pressure is not important, but the pressure due to the warmer ambient temp is a smaller factor, than the pressure created by compression and boost, a warmer ambient temmperature will cause the intake charge to be much less dense, there for in the end causing LESS cylinder pressure than a cold charge, hence the purpose of cold air intakes and intercoolers, also an explination on why i can hit boost levels of 25PSI in the cold winter(sub 30d here), and only 19-20PSI in dead heat of summer, with hot air you will lose power. The formulas i have used in this thread explain all this, all my calculations are based on a 90d "standard" day,( im still wondering who created and why 90d is standerd, but it is) which for most is a rather hot day.. Hope this helps!!

 

Andy, also on your calculations on airflow you need to add in your Boost ratio,

"97.6cid*7500*.5*.8/1728=169.4444

boost ratio on a 19% using your 17.5psi

17.5+14.7=32.2 absolut pressure

32.2/14.7=2.19

so.....

169.444*2.19=371.15 cfm"

 

The temp change surprised me and I think I know why. I used an 85% efficiency for the intercooler. So, the actual change in temp was only 70F or so, compared to ambient. But, presumably that only represents 15% of the temp difference between compressor outlet and ambient. So, I worked backwards to add back in the 85% that was taken out. In reality, I suspect the intercooler wasn't at anywhere near 85% efficiency in this instance.

I'd really like to have a couple more pressure taps and a couple more temperature sensors.

I'm not gonna plug in your 19% figures until I see actual data. I wish I had been able to log temp on BlueMCS's car ... ah well. Maybe I'll swap on my 19% tomorrow. It sure makes metric calculations simple when you do logging at sea level and 0 C.

 

Andy -

Normally, I'd be glad to log that for you but I'm on good behavior for another 350 miles (clutch run-in). I have some old temp logs if that would help?

 

Caddman here you are :smile: The guys over on your thread have been looking for you ever since your last post ( see below ) Everyone is waiting for the pics etc on your cowl scoops. They think you are hiding , drop in and ay hello they would apprecitate it.

Posted: Jan 22, 2004 - 05:23 PM OK, now i really feel bad for not keep ing up with you guys.....Ive been really busy,lots of interesting stuff going on but not quite to the point i can talk about it yet, but any ways yes the are done, and im trying to find my damn pics, i had them on my work computer, now they are missing , but no fear this weekend if i dont find them i ll take some nonprofessional ones to get them up, i really need some on my site obviously, netx time i wont stray away for so long........ my bad!!!