I am currently running 19 % and the car runs very strong up to redline. I am adding a few more mods this month to "finish" the engine.

I am concerned as I run the car over 6K that I am beating the heck out of the supercharger. I would like to raise the redline over 7K as the engine is very strong up top and makes a lot of power in the last 700 rpm. The question is how high can I raise it with the 17% or do I need to dial back down to 15%? Even if I don't raise the redline but start driving more above 6K what is the wisdom out there?

I have made the decision to port/hone out thr SC and Intake manifold and runners. As long as the car is apart I may as well. After this last step I am done with the engine (I'm repeating myself)

 

"I am adding a few more mods this month to "finish" the engine."

Sounds like you have done it ALL

I hope it LASTS forever, let us know the results

 

Me too

The SC and intake work will be the end for the engine.

After that the Quaife/flywheel/clutch

After that the Sparco/Milano/Prestige.

After that....who knows:smile:

I don't dare add up my receipts anymore

Thanks,

Bob


I don't want to get off thread because I do need this help with pulley size

 

Well... if you do the math... dropping to a 15%@7000RPM will still run SC faster than 19%@6250. Keeping the 19%@7000 SC = 18000+ RPMs , 4K (29%) over spec

I suppose it depends on how much time you plan to drive with engine at high RPMS... it this a street machine or do you take it on the track. A lot of high RPM on track may takes it toll on SC. At some point SC you are not getting any addtional benefit from runinng SC any faster so why not drop to 15%

One note I haven't seen on Eaton website what actual max RPM is... there graph only goes to 14K. It may be higher. You might contact them and ask the question.

Given...
Max Engine RPM: 6250
Max SC RPM: 14000 (eaton) Eaton M45
Crank size: 5.4"

Stock Pulley: 2.58" --> Ratio 2.08 --> Max SC RPM = 13000

15% Pulley: 2.46" --> Ratio 2.46 --> Max SC RPM = 15375

17% Pulley: 2.14" --> Ratio 2.52 --> Max SC RPM = 15771

19% Pulley: 2.09" --> Ratio 2.58 --> Max SC RPM = 16125

If you raised engine RPM to 7000
Max SC RPM:
Stock: 14560 4% over
15%: 17220 23% over
17%: 17640 26% over
19%: 18060 29% over

 

If you do a good deal of high-speed driving, go back down to 15%. You can more fully realize the potential of the UNIChip with the 15% pulley. Unfortunately, you DO lose some low end...but if it's a speed machine, by all means go with the larger pulley and spare your SC.

By the looks of it, you could probably pony up the $$$ to replace your SC with a low mileage unit anyhow if you trash the current one.

Marty

 

Hmmmmm!


I have been thinking 17% but now It looks like maybe back to 15% is the smart play.

Thanks

 

Thank you so much for all that work.....this is very, very helpful

Bob

 

Bob-

Have you fetched an "expert" opinion (i.e. a la Randy Webb)? I have a feeling we both know what he'd say

Marty

 

Actually, I think the SC Redline is over 17K. Check out this thread: https://www.northamericanmotoring.co...ad.php?t=43127 The pertainent info starts around Post #60. Look also at Post #74 & #86.

 

Very good info....Thanks

I called Eric to get a 17% ring for my Helix pulley.

I really appreciate the help. I thought that 23% was absurd so I never read the thread....I should have.

Thanks again

Bob

 

The JCW pulley is what, a 14.7% reduction pulley? I believe that brings the SC beyond the 14,000rpm limit. I cannot imagine that BMW/Mini would leave such a small tolerance...if for warranty purposes alone.

 

The numbers in the other thread indicate that the SC redline is 17,200. And, they indicate (as you noticed) that the highest engine speed (with a JCW pulley) without exceeding the SC redline is 6859 rpm.

This leads to one or more of the following:

1. BMW/MINI/JCW is right at the upper limit
2. Eaton's published redline is conservative
3. The numbers are off in the other thread

Now, it could be any or all of these. The numbers were calculated by trusted sources (Dr Obnxs, cdconsor & Alta), so let's trust them for a moment. If the numbers are OK, how have MCS tuners been getting by with 15-19% reduction pulleys in tandem with ECU mods that often extend the engine's rev-limiter?

The answer may be in #2. And, in the way the car's driven. I don't think it's too big a stretch to assert that the time spent at 7K is minimal for most MCS drivers. It's probably just as true that the time spent at 7K for pullied cars is causing accelerated wear on the SC. That's not news to any of us, right? The question is how much wear are we incurring? And, how conservative is Eaton's published redline?

I think there's ample evidence that JCW & -15% pulleys are safe. There are a growing number of cars overdriving the SC even more with no short-term problems. What's the long-term effect? Well, that stuff will probably wear out faster if it's driven into the upper 6000's on a regular basis.

Bottom line for me is we already knew all this; we're just better able to measure where the "damage" starts and avoid it. One could look at a -19% combination with an upgraded intercooler and think: "I've made more power lower in the rev-range, and if I'm willing to shift at 6500 rpm to keep the SC below its redline, I'm still within the design tolerances."

The question about which combination has more area under the curve has not yet been fully answered, but the hypothetical overdriven car in the preceding paragraph will, in all likelihood, feel faster because of the shift in the torque curve. It may even be faster. I have a feeling Alta's testing will tell the tale...

 

It's been quoted on this site many times but I believe the SC redline is in the 16k RPM range. Not 14k.

 

I have had a conversation this afternoon with someone who has a lot more experience than me. I am going to hang with 19% until I blow up a SC. At that time, if in fact I do, I'll make a decision. I really appreciate everyone who took the time to contribute.


Thanks,

Bob