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View Full Version : Any daily drivers running 25% overdrive?



mywhite89
05-13-2009, 04:52 PM
Seems about every 1,000-3,000 miles I go through a set of supercharger rotors in my MPX. For me, thats about once a year problems. I can see the insides of the fins on the blower rotors deteriorating before it starts really making noise and destroying my case, so I pull it apart before that happens.

I think at 25% overdirve I may be just overheating this thing, but I want some other peoples views and experiences on this. Maybe 25% is a track only kind of overdrive. Seems I've got all the bugs worked out except this darn MPX.

Chris

BLOWN38
05-13-2009, 10:02 PM
I made 63 runs down the 1/4 mile last year with my mp3. Drove it to Dayton and back(800 miles each way) at 25% od alltho I was babying it cause i was runnin on 87 octane (when gas was outragous). Most of this was with a small shot of alky before the blower.

Then this season after having the blower refreshed due to the rotors transfering metal to each other. Made 1 pass with the alky and was fine although it bogged after the 8th due to needing a tune really bad and running way too rich. 2nd pass turned the alky off was about 100* car ran fine till i got to the end of the track the blower started rattling.

Took the blower top off and found the rotor contacted the back of the case. Bye Bye MP3.

So maybe there is something to shootin alittle alky before the blower. I had the 175ml jet before the blower.

johnrada
05-13-2009, 10:51 PM
i think this thread is interesting, how big of a heat difference is there from 15% OD to 20, to 25? Do you think it's only heat related or maybe the bearings just aren't meant to be spun that quickly that often?

frdlvr30
05-13-2009, 11:13 PM
i think this thread is interesting, how big of a heat difference is there from 15% OD to 20, to 25? Do you think it's only heat related or maybe the bearings just aren't meant to be spun that quickly that often?

I'd say all of the above

90blkbrd
05-14-2009, 10:01 AM
I don't know if this has anything to do with it and maybe I should start another thread.

Do 5-speed cars eat more rotors than auto's?
Who is running a solid coupler vs a OEM coupler with springs?

When I am under power and shifting gears I can hear the supercharger change RPMS along with the engine and hear the SC drag a little bit as I release the clutch(belt slip?).

My theory is this. Could this instant rpm change cause problems with the rotors, especially with the high rpms of 25% OD? Could an OEM coupler stop this from happening? Does this same condition happen with an auto?

XR7 Dave
05-14-2009, 10:26 AM
Going from 15% to 25% OD on the blower increases outlet temps by about 75-100 deg F. The higher the engine rpm the bigger the spread. Run for short bursts of time on the street, the impact is probably minimal. Run for extended periods of time at full throttle and high rpm, the curve continues to climb. Even though ACT's tend to level off after a certain speed due to the IC, blower outlet temps do not show any evidence of leveling off.

frdlvr30
05-14-2009, 07:04 PM
Going from 15% to 25% OD on the blower increases outlet temps by about 75-100 deg F. The higher the engine rpm the bigger the spread. Run for short bursts of time on the street, the impact is probably minimal. Run for extended periods of time at full throttle and high rpm, the curve continues to climb. Even though ACT's tend to level off after a certain speed due to the IC, blower outlet temps do not show any evidence of leveling off.

Never actually thought of it that way, nor did I realize the ACT's were that much higher at 25%. Make sense though since the blower is not intercooled, the air is. Would methanol in the plenum be a solution?

XR7 Dave
05-14-2009, 07:18 PM
Would methanol in the plenum be a solution?I would say no.

Quik95SC
05-15-2009, 09:20 AM
I am running 25% on my daily driver and have been for about 3.5 years now. I usually run every other Friday night on an 1/8th mile track and log about 12,000-15,000 miles a year on the car during normal driving.

I am using a 4 year old MPIII I won at the shootout in OK. Rotors still looks good from what I can see. I am running a solid coupler with an Automatic trans.

Only issue I had is that I had to replace a blown snout seal at last years Shootout.

Not sure what to tell you, other than maybe the tolerances in the MPX are just tight enough to cause issues. Ask John Ludorf about his MPX Experience, and destroying them.


Smitty

mywhite89
05-15-2009, 10:12 AM
I am running 25% on my daily driver and have been for about 3.5 years now. I usually run every other Friday night on an 1/8th mile track and log about 12,000-15,000 miles a year on the car during normal driving.

I am using a 4 year old MPIII I won at the shootout in OK. Rotors still looks good from what I can see. I am running a solid coupler with an Automatic trans.

Only issue I had is that I had to replace a blown snout seal at last years Shootout.

Not sure what to tell you, other than maybe the tolerances in the MPX are just tight enough to cause issues. Ask John Ludorf about his MPX Experience, and destroying them.


Smitty

You ever open it up on the road for a halfway extended period of time?Because I do every once in a while, and thats probably what is causing the problem. Other than an MPX being the problem, maybe our driving styles are just different, and I'm a wild driver, who knows.

Quik95SC
05-15-2009, 01:13 PM
You ever open it up on the road for a halfway extended period of time?Because I do every once in a while, and thats probably what is causing the problem. Other than an MPX being the problem, maybe our driving styles are just different, and I'm a wild driver, who knows.

I would have to say no for the most part. I get get a bur up my butt to run up to about 110-120 for a very short burst, but then with the 3.7s gears it gets the rpms up pretty high. By then I have gone too long and get nervous of our local State troopers and back it back down pretty quick.

I do have occasional rips on it in town but usually only up to about 50 or so so it will shift into 2nd and chirp the tires at some silly looking rice car!! LOL

So far, so good, and I pray before ever run at the track it stays together!!

Regards,
Smitty

mywhite89
05-19-2009, 04:24 PM
I would have to say no for the most part. I get get a bur up my butt to run up to about 110-120 for a very short burst, but then with the 3.7s gears it gets the rpms up pretty high. By then I have gone too long and get nervous of our local State troopers and back it back down pretty quick.

I do have occasional rips on it in town but usually only up to about 50 or so so it will shift into 2nd and chirp the tires at some silly looking rice car!! LOL

So far, so good, and I pray before ever run at the track it stays together!!

Regards,
Smitty


Guess I need to stsrt praying more often than cussing at my car from now on!! haha. Thanks for the information

Chris