Urgent blower help...

Rezlo

Registered User
OK where to start?

Im using a M90 of an earlier (oval port) TB on a custom air to air aftercooled High compretion 3L Mitsubishi V6 stuck in a Dodge Stratus.

It was pretty good till recently, Ive always had a good amount of blower rattle, even after I put new bearings and new coupler it still has a rattle at idle. It has been slowly (very slowly) getting worse.

Ive been slowly adding more and more boost, im at 12psi now (10.5-1 compretion) and as soon as i get it over 5000RPM i start to loose about 3psi of boost to my 6800shift point. Realy sux as my engine makes most of its usable HP up there and it kind of lays over not to bad but anoying enough.

Now I know the latter models of the blowers have coated rottors, has anyone had the earlier ones coated to close the air space (cooler air and less boost loss at high RPM)? Also are there other differences besides inlet opening changing to rectangular on the later year blowers? and i guess last of all are there any direct swaps to newer or larger eatons?

One last thing, Is there anyway of slowing the bypass actualtor from opening, I get to 11% throttle and i start making boost, are there any actuators that have a different spring pressure to stop it from starting to shut the bypass at 4-5In-hq?
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A Couple of Questions for ya

Rezlo said:
It was pretty good till recently, Ive always had a good amount of blower rattle, even after I put new bearings and new coupler it still has a rattle at idle. It has been slowly (very slowly) getting worse.

Ive been slowly adding more and more boost, im at 12psi now (10.5-1 compretion)
Your blower may have a blown front seal. That causes the oil to leak out, & with low/no oil, you get blower rattle.

Are you saying that your STATIC compression is 10.5:1?

Have you upgraded your fuel system? Big fuel pump? Bigger injectors?

68COUGAR
 
Regarding the bypass valve. The stock valve is actuated ONLY from inlet plenum vacuum. In other words, it is not boost referenced. It sounds like you are using boost referenced vacuum to actuate the bypass valve. If you find that with the bypass referenced to the inlet side of the blower that you end up with leakage at high rpm that is a sure sign that you are getting vacuum (cavitation) in front of the blower This would mean that your intake is too restrictive.

Regarding the boost fall off. That is a sign that the blower cannot flow enough air to keep up with your motor. Coating the rotors will not help that problem. What you need is to port the inlet of the blower and/or increase the flow capacity into the inlet. I recommend a minimum consistent 3" diameter going into the blower. If you inlet tract can't keep up you will end up with a vacuum in front of the blower which will result in cavitation and loss of output.
 
I have a huge fuel system,

Yes the bypass is actuated from a vacuum between the TB and the blower so no pressure is seen,

No oil leaks, i think its just getting old, already replaced the nose bearings and seals and used the right oil, i think its mild gear slop (lobes arnt touching at all)

Humm, Ive just put a 60mm TB onto a new inlet, the only place it could be restricting is my sucky air filter if cavitation is the problem.

Ive ported the inlet and outlet housing of the blower to try help it,

Im thinking it might just be that the blower is to small for what im trying to get it to do.

On another note, is there any way of changing the shape of the casting under the outlet lid (like widening it) that would help drop lower RPM boost and help with higher rpm presure?

Ive got to much bottom end and not enough top end... need to try shift the power curve a little.
 
the eaton blowers are notorious for low end torque, thats why you make so much power down low, i'm not familar with your engine is it a 24v dohc 3.0? what is your redline? if it is a higher reving engine then the eatons not going to like it unless you underdrive the SC to build boost higher in your RPM range utilizing your setup more efficeintly, looks like a pretty good setup though

Joe
 
No its a 24Valve SOHC V6 similar to those found in the new Mitsubishi eclipse's.

I love the bottom end I have, gets me off the line real quick with 340ft-tq at a mear 2500rpm but from 300 its just falls to its death at 280ft-tq at 6800(redline) while the HP is trying its hardest to catch up towards redline.
 
Concerning your "rattle", I'd pull the blower off the car immediately and open it up. Look the rotors over for signs of interference with each other, could be that the rear needle bearings are on their way out.

got some more pics of your engine compartment?

'bird

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I had the lit off yesterday, no lobe problems at all, I have a feeling it is the rear bearings. The nose cone is good just the others im not so sure about.

Where can you get those rear bearings? and possibly the front bearings the lobes run on?

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Rezlo said:
I had the lit off yesterday, no lobe problems at all, I have a feeling it is the rear bearings. The nose cone is good just the others im not so sure about.
Where can you get those rear bearings? and possibly the front bearings the lobes run on?
I keep all of the bearings on the shelf.

Nice work there on the manifolds!

'bird
 
Thanks, this has been an on-going project for a while now, im still just making way to much TQ and not enough HP... time to tweek the manifold again and see what I can do to get them to overlap a little.

I know the nose cone is good so how much would the front and rear lobe bearings run me shipped to 60455 Bridgeview IL?

Thanks

Ian
 
Your TB is too small. Ours is 63mm stock and most of us use at least a 70mm unit. It looks like your TB aims right at the back of the blower, so that part seems ok.

Are you sure the bypass is not partiallly opening at high boost/rpm? I've seen it happen. Try blocking the bypass closed and see what happens. Is it possible you are getting belt slip?

If you've checked those things, then you need a MPII blower (and at least a 75MM TB to go with it).

Oh, and how much boost are you getting anyway? What is your drive ratio?
 
Im pulling 11-12psi, from 2000rpm to 5000, then it drops down to around 9psi by 6700, not sure on the drive ratio, ive made so many pullies I cant even remember. Yeah im 100% sure its not slipping and no the bypass isnt opening at WOT, I can see it from inside the car when the hood is off, checked that today.

I put the 60mm on pretty recently, I had a 56mm, did exactly the same thing, with the 60mm its almost to much off the line, i have to REALY feather it to not smoke the tires, I think its the fact my engine is completely ported and flows amazing numbers, maybe my engine seeing 12 psi would be alot higher on a normaly ported engine and im going over the efficiency rating of the charger. Took it for a drive today and poped the air cleaner off, exactly the same, MAYBE 1/3 of a psi difference.

How much difference is there in a MP-II? how much of it can i swap over from my oval port?

Ian
 
I think its the fact my engine is completely ported and flows amazing numbers
Ok now we get to the bottom of it. :D

Definately need a bigger TB! Minimum 75mm. The MPII won't bolt up to the stock plenum you have now, but obviously you can fab, so it shouldn't be any trouble to modify the inlet to match the new blower. Actually what they do is chop the back off your existing case and graft a new one on. Then they port the outlet big time.

A MPII will feed your motor with 16+psi all the way to redline. You will need to spin it a little faster though and you must have a larger TB. Did I already mention that? :D

Magnum Powers
 
I actualy dont think i could go that big, my throttle responce is WAY to great even with a 60, got to remember im FWD i have to feather it so i dont just leave rubber and snapped shafts.

How much do decent MPII's go for ? im a poor basted :)
 
That is so sweet

awesome craftmanship...you running a hood on this car? ...wonder if you are running into a aerodynamic problem and creating a vacume around what little intake track you have at higher speed ..I would build a wall up behind the airfilter on the back side to help build air pressure around the intake filter..the air could be moving so fast around it it could be sucking it out of the charger ...dave
 
I dont think so, does the same thing with the filter on or off, and Ive milled out as much of the air inlet as I can, the TB has a neer straight shot at the blower, I can see the entire oval opening with the TB opened, its all ported and polished to.

Im thinking maybe new bearings would stop air cavitaion, probably a real good idea to change them now anyway seem as the lobes are like brand new so latter on down the road i can sell the blower if i need to.
 
Well the problem is you are exceeding the airflow capability of the 60mm TB. All you need to control the throttle response problem is a variable leverage throttle actuating device (cable over a cam works best for this). I am quite certain that you have throttle cable geometry that is incorrect. We run 85mm TB's all the time with no driveability issues. Its all in the linkage.

What happens with a restrictive TB is that there is cavitation or a vacuum created in front of the blower. When this happens output of the blower is physically limited. So no matter what you do to the blower, your output at high rpm is going to be muted.

Bearings have nothing to do with cavitation, but if they are bad then I'd just change them. ;)
 
It has a large cam, i have to have the pedal about threw the floor to get WOT, did the Exact same thing with a 56mm TB I had on before(I think the GTP's are actualy that small stock to)

I think I should just throw my inlet onto the mill again and try to clean it out even more and see what it will do.


Tbird88 what will the case bearing run me? (I think ive got the nose bearings from you before)
 
Well you just don't have enough blower. I have the same problem with my stock blower on my car. It makes a peak of 10psi at 3000rpm and falls off to about 7psi by 6000. With a good blower on the same motor it makes 14 at 3000 ant 18 at 6000. You are probably leaving up to 100hp on the table like it is. If you are having problems with the TB and throttle response, then you need to work on that as well. If you can mill and fab things, just put on an 03 cobra dual 58mm TB. It's even oval to "kind of" match your blower inlet.
 
Well, got the blower all apart, replaced the rear casing and cartiridge bearings, when assembling i put the drive gear on, then rotated it, the sound it makes when the one rottor is turning the other (no other gear) is how it used to sound, now with the right rottor timming (pita to set) all i can hear is a tiny gear click if i turn it left to right real qick (no oil in it yet)

So im pretty sure the rottor timing was out just a hair, seems fine now, all i need to do now is finnish my new engine and see if it works and sounds better.
 
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