dcon:

the mini engine has a tiny microphone attached to the block (a mini-mike!) which listens for the pinging sound of detonation (knock) the computer then retards the ignition slightly, dropping power, and reducing the knock.

If you have excess load, higher combustion chamber temps, hotter intake charge, carbon deposits, bad gas or too advanced timing, you are prone to knock. It ain't a good thing, especially at high rpms and can put a hole in your pistons.

My suspicion is that the torque drop at 7200, also seen at other rpms in other dyno runs, is an indicator that the igniton was retarded due to the onset of detonationa t that 7200 point.

Caddman and Randy and others have proposed the theory that if the igniton were slightly retarded anyway, enough to not produce any detonation, with just a minimum power drop, the more major knock detector retard would not come into play and the net result would be more power.

 

Well I'll have to take your word for it, JLM. I'm a right-brain kind of guy. If you want o paint fancy stuff on the hood of your mini, then I'm your man, but I'll leave the wrenching to you, Randy and these others.

Dave

 

RandyBMC wrote:Yes, I have one. Now that you know the factory rev limiter is not 7200, has Evo given you any indication of why there is such a pronounced dropoff at that rpm?

 

This could be cavitation, Andy. I'm sure knock is not a problem at 7000+ rpm, as it could be fixed by retarding the timing. What can't be fixed is supercharger cavitation. The pulley we are now using spins the supercharger to an rpm higher than originally planned for. I suppose a 20% reduction puilley would give stronger low end, but the drop off would occur at an earlier (pre-redline) rpm. Unless the timing were being intentionally retarded (soft touch rev limit) this is the only thing I can think of that would make the engine drop in torque and power that dramatically.

PerfPow

 

I have a problem with that theory. My curve is nice and smooth, even while spinning the blower at 17,700 rpm.

 

The SC is definately at or near its limits at the stock rev limiter but I didnt think there would be such a severe dropoff in power if things started to get funky. I figured power would plateu. Gee randy, a boost plot sure would be nice....

I've got a different idea. What are the chances that there are no table values for RPMs that far over the stock rev limiter? I would imagine the computer takes some default "safe value" if it didnt have a look up value. Another possibilty would be you've exceeeding the stock MAP sensor's range it the computer isnt happy about it which would result in the same outcome, a default value.

Yes/No/Maybe?


--
Cheese

 

andy and cheese,

The answer is I really don't know yet.

I am waiting for an answer, and as soon as I get it (because anything I throw out would be speculation as well), I'll share.

andy,

How do you know you are spinning at 17,700? From what I've discussed with folks in the know, the Eaton isn't turning that fast even at 7500RPM.

cheese,

I'll be doing boost plots soon, and I'll post them ASAP (it sure would be helpful to have that BiMcom stuff!).

That's one of the reasons I'm waiting on an answer - there have been such data collections.

Randy

 

Also, so you all know, because of the dyno results with the pulley, the redline on the cars with the pulley will be limited to 7200 as opposed to 7500.

Randy

 

If the only thing you had to do was retard advance for the last 1,500 rpm or so couldn't you achieve the same result through water injection? Has anyone tried this?

My guess is that they advanced at the lower end, retarded at the top and that along with the leaner a/f is giving the midrange torque and hp at the top.

 

damn...my secret is out!

 

>>cheese,
>>
>>I'll be doing boost plots soon, and I'll post them ASAP (it sure would be helpful to have that BiMcom stuff!).
>>
>>That's one of the reasons I'm waiting on an answer - there have been such data collections.
>>
>>Randy


Why not just give me a free ECU and I'll do the testing at no charge to you :smile:


--
Cheese

 

RandyBMC wrote:
The supercharger spins at 2.06 times engine speed from all the technical literature I have seen. The stock supercharger pulley is ~2.6", the Helix/P&D pulley is ~2.2".

7300 RPM X 2.06 X (2.6" / 2.2&quot = 17,772 RPM.

 

to back up andy, I believe Eaton recommends 14,000 for the blower at max redline: 14,000/6,800=2.06. The 15% pulley would then turn 16,000 at 6,800, for those brief bursts near redline, or about 17,000 at 7,200; a screaming thing. I'm keeping my shift points below 6,800 anyway.

 

>>there are practically 100 modded pulleys out there intstalled and yours is the first to have a belt problem that I have heard of. It might be possible to add a belt guide lip at the front (its already at the back) and or increse the size of the lips, but i would suspect an alignment issue in your case. It would will wear out the belt if mis-aligned, even with lips.

Yes you may be right, I have had over 6k on this pulley and really dont understand why it decided to move off. I was using the replacment NAPA belt that is shorter. I did notice that the Napa belt has a slightly different rib design. It doesnt seem to ride the same way as the stock belt so I am going to a stock belt first to see if this makes a difference.

People should not be concerned about this happening, maybe I am an isolated case.

 

>>to back up andy, I believe Eaton recommends 14,000 for the blower at max redline: 14,000/6,800=2.06. The 15% pulley would then turn 16,000 at 6,800, for those brief bursts near redline, or about 17,000 at 7,200; a screaming thing. I'm keeping my shift points below 6,800 anyway.

Looks like you have to keep it under 6000rpm with a 15% pully to keep the supercharger below its 14,000 limit. Is pushing the blower past this limit something we should worry about?

 

>>to back up andy, I believe Eaton recommends 14,000 for the blower at max redline: 14,000/6,800=2.06. The 15% pulley would then turn 16,000 at 6,800, for those brief bursts near redline, or about 17,000 at 7,200; a screaming thing. I'm keeping my shift points below 6,800 anyway.

I wonder if this could mean that this SC isn't really made to withstand addition of a 15% pulley over the long term, particularly with regular high revving?

Thoughts?

 

I have spoken with two different engineers on the RPM limit of the Eaton - it is safe to 17,219 RPM. At 7,200 RPM, you are just under that. At the stock limit of 6950, you are well under that.

Another comfort for some folks is the same exact supercharger being used by JCW with BMW's blessing using the same reduction.

We have worked hard at gathering data to make sure this is a relatively safe modification. I am very confident that it is.

Randy

 

>>>>to back up andy, I believe Eaton recommends 14,000 for the blower at max redline: 14,000/6,800=2.06. The 15% pulley would then turn 16,000 at 6,800, for those brief bursts near redline, or about 17,000 at 7,200; a screaming thing. I'm keeping my shift points below 6,800 anyway.
>>
>>I wonder if this could mean that this SC isn't really made to withstand addition of a 15% pulley over the long term, particularly with regular high revving?
>>
>>Thoughts?


The JCW kit pushes the redline up to 7200 or 7500 RPM with the 15% pulley. So I'd tend to think this has been thought about and doesn't appear to be a problem. Any other thoughts???

 

as mentioned in another post, the real value of the JCW package is that they warranty it; not because I am going to buy the damn thing, but because that warranty validates the mechanical integrity of the engine, transmission, drivetrain, blower, etc. when pushed to 200hp. QED.

 

For those of us who never paid attention in Latin class:

QED = quod erat demonstrandum

'which was to be demonstrated'

 

The JCW (man i always think JC Whitney when i type that) superchargers might possibly be hand selected. The thing about the eaton blower is its a piece of junk typical domestic casting with a copious (whats the latin word for that?) amount of core shift. The tolerances on the thing are horrible so consider the 14k or 17k rev limit to be pretty dependent on the quality of your actual supercharger. JCW's teflon coating's thickness might tighten up the tolerances some as well.

A respected engine builder quoted me 16k-18k as the RPM limit for a stock eaton blower.

FWIW, an OEM pays ~200 USD for an eaton unit. You can buy one at the dealer for $1200 plus $200 core. Hows that for markup?

--
Cheese

 

hi randy ,great job keeping everybody informed. I have a question regarding the ecu upgrade. Can the dealer detect that you have a different program than the stock one, and can he legally tamper with your new ecu. and bringet back to stock again without your consent.????
Thanks again for all the info. I'll see you in florida for the pulley.

 

>>For those of us who never paid attention in Latin class:
>>
>>QED = quod erat demonstrandum
>>
>>'which was to be demonstrated'


cool.thanks!

 

Randy BMC
Just wondering, what ever happened to the idea of having a "piggy-back"-type of setup for the ECU.
Another question - with such a mod. do we run the risk of having the flash erased by a BMW flash during an upgrade or diagnostic.

 

i had the early Evotech with early Mini firmware. it did nothing for the power, although the redline moved up to 7500, so I knew it was in there. I sent it back, which is to say, George at Mini madness told me to go in and get it re-flashed with the latest upgrade. This was before anyone suspected the early firmware was incompatible with the evo mod, or I might have had it re-Evo-ed.

I did this at the dealer, and a very friendly mechanic let me watch. He knew I had the evo in there, but could find no evidence of it; furthermore, it hadn't tripped the ecu upgrade counter, and if I hadn't told him, he would not have seen it. Re-flashing the firmware totally erased the Evo mod however.

If you do get it overwritten by accident, Evo will re-flash it for you for a minimum charge.