Expected psi from Eaton blower

I have my m62 Eaton charger belted up at 2:1 crank speed on my ford 2.3 lima

I was expecting a bit more than 3.5psi.

Does that sound right? 

62 cubic inches/rev = 1.02 liter/rev.  Since it's belted 2:1, that's 2.04 liter per crank revolution.

The engine consumes 1 displacement worth, per two revolutions (it's a 4 stroke, not a 2 stroke), at 100% volumetric efficiency (near peak torque >90% is normal).  So call it 1 liter per revolution (2.3/2 * 90% = 1-ish).

2.04 liters / 1 liter = 2.04 pressure ratio.  14.7 psi in, 2.04 pressure ratio = high 20s PSI of manifold pressure, so I'd expect at least somewhere north of 10 psi.

I had estimated at least 7psi. 

I was getting 6psi using an m45 on a 16v 2.0. 

I've capped off the system and pressurised to find leaks.. 

I found some small leaks, fixed those but that made little difference to boost made.  Actually my log showed 0.1 psi increase!

I have a turbo blowing into the charger but I've removed the spring from the wastegate so not building any boost before charger. Im also not getting a -inhg reading between the two so I presume the turbo isn't restricting the charger.. 

I will disconnect a coupling between the too to make sure but what else should I consider looking at?

The belt isn't slipping, is it?

Matthew Kennedy said:

The belt isn't slipping, is it?

Or there is a leak due to failed coating or Teflon. Are you 100% sure you are not underdriven?

Have you opened it to see if the rotors are spinning?  couplers normal fail but that should just make it noisy, the metal fingers should still hit and turn but  one never knows.

In reply to Matthew Kennedy :

no its pretty tight... That was what i first checked.

In reply to wearymicrobe :

Teflon looks real good. I had it all apart to grease the rear bearings.

Pulley is half the diameter of the crank pulley so I put that at 2:1 

In reply to 44Dwarf :

It was originally a clutched pulley but i had a solid one made for it. It doesnt run one of those doughnut rings in the gear box.. The drive goes straight through.

Don't know what the drive ratio was, but the M62 that I had on my 2L Zetec Focus was good for 10psi.

Maybe my diy head port job was bloody fantastic and it breathes like a dragon!?? 

In reply to Craigorypeck :

190% VE? Now that's a berkleying port job.

Please ignore me if this is a stupid question but, are you measuring positive pressure with a MAP and software that's capable of reading more than 1.25 bar?  

I only ask because +3.5psi is a very convenient number for a design/software cap.

Matthew Kennedy said:

62 cubic inches/rev = 1.02 liter/rev.  Since it's belted 2:1, that's 2.04 liter per crank revolution.

The engine consumes 1 displacement worth, per two revolutions (it's a 4 stroke, not a 2 stroke), at 100% volumetric efficiency (near peak torque >90% is normal).  So call it 1 liter per revolution (2.3/2 * 90% = 1-ish).

2.04 liters / 1 liter = 2.04 pressure ratio.  14.7 psi in, 2.04 pressure ratio = high 20s PSI of manifold pressure, so I'd expect at least somewhere north of 10 psi.

That math makes sense until you look at the compressor maps and see that there is a volumetric efficiency for the blower, and it is not 100%.  At lower RPM the efficiency is low, then it comes up, and then it drops off again.  I assume this is because first of seal bleedback and later due to poor breathing and/or beating the air up so that it heats it up a lot.

Also, the VE is dependent on how much pressure is in the intake manifold.  More manifold pressure means lower VE.

I do not have my charts handy, but I would expect no more than 80% VE and I would like to say 70% is a good figure to start guessing at.

Also, the M62 has a redline of 12,000rpm with an absolute max of 14,000.

Most of what a learned about pulley sizing on Eaton blowers is "there are so many ways to get the math wrong, just start with something and go from there."

Hungary Bill said:

Please ignore me if this is a stupid question but, are you measuring positive pressure with a MAP and software that's capable of reading more than 1.25 bar?  

I only ask because +3.5psi is a very convenient number for a design/software cap.

I have 2 ways to measure boost. A mechanical gauge and a 3 bar map sensor for ecu. 

Both give same readong

Knurled. said:

Matthew Kennedy said:

62 cubic inches/rev = 1.02 liter/rev.  Since it's belted 2:1, that's 2.04 liter per crank revolution.

The engine consumes 1 displacement worth, per two revolutions (it's a 4 stroke, not a 2 stroke), at 100% volumetric efficiency (near peak torque >90% is normal).  So call it 1 liter per revolution (2.3/2 * 90% = 1-ish).

2.04 liters / 1 liter = 2.04 pressure ratio.  14.7 psi in, 2.04 pressure ratio = high 20s PSI of manifold pressure, so I'd expect at least somewhere north of 10 psi.

 

That math makes sense until you look at the compressor maps and see that there is a volumetric efficiency for the blower, and it is not 100%.  At lower RPM the efficiency is low, then it comes up, and then it drops off again.  I assume this is because first of seal bleedback and later due to poor breathing and/or beating the air up so that it heats it up a lot.

 

Also, the VE is dependent on how much pressure is in the intake manifold.  More manifold pressure means lower VE.

 

I do not have my charts handy, but I would expect no more than 80% VE and I would like to say 70% is a good figure to start guessing at.

 

Also, the M62 has a redline of 12,000rpm with an absolute max of 14,000.

 

Most of what a learned about pulley sizing on Eaton blowers is "there are so many ways to get the math wrong, just start with something and go from there."

It hits max psi near instantly and just plateaus.  Gearing up isn't an option, tried that before... Not good.

This is a sohc so i cant dial out any overlap and im using an NA ranger cam. This is a common mod to make use of the roller rockers and most folk say it has the same lift/duration/lsa as the stock turbo slider.

Ive never measured so can't be sure but I think it's leaking just that extra bit out the exhaust. If I get a custom grind I might run a real wide lsa. That seems to be the characteristics of supercharger cam, from what I've read on t'webs.

It is what it is now I suppose.. Going to put the spring in the turbo wastegate tonight. Ill not be crying about low boost figs then...

Wish me luck! 

Worst case, you can always swap the M62 for an M90 at some point...

Following along.

rslifkin said:

Worst case, you can always swap the M62 for an M90 at some point...

Tight for space but maybe!

I recently did a custom M62 supercharger install on my 4.0L Jeep. Hopefully my experience can be useful here.

This site was my inspiration > http://jeepm62superchargerkit.blogspot.com/  He has tons of good information sprinkled about the page, but the most useful was the FAQ, especially #35. I built a spreadsheet based on the calculations. Playing with the pulley diameters revealed to me that the M62 pulley size was a sensitive factor in getting the boost numbers up. A 2.2 pulley ratio predicted 1.5psi, while a 3.0 ratio predicted 6.5psi. I went with the 3.0 ratio and I am getting right at 7.0psi at 5500' elevation.

So my guess is that you're slightly too big on the supercharger pulley. I'd size it to max out the supercharger RPM at redline and see what boost that gives you. If you're already there then consider dropping the max engine rpm 500-1000 rpm so you can run the M62 harder. You may just not be getting the optimal efficiency window of the engine to line up with the optimal efficiency window of the supercharger. For what it's worth, I am seeing 7psi from 1500 to 3500 rpm before it starts to drop off. The M62 seems to prefer making torque rather than power

In reply to Rick O'Shea :

I purely based the pulley size on the redline of the charger and the engine.  6500rpm on the engine is 13000 on the charger. I may be going for a different cam that'll push Red line even higher.

I also have a holset turbo blowing into the charger. Once thats in the loop ill decide on final pulley ratio. Trying to compound boost levels above the back pressure created by turbine.